S.C. Kavassalis

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Permanent student of mathematics, physics, and sometimes, the philosophy of their intersection.

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  • November 29, 2010
  • 08:25 PM
  • 1,774 views

This Week in the Universe: November 23rd – November 29th

by S.C. Kavassalis in The Language of Bad Physics

Astrophysics and Gravitation:
Lensing of Black Holes Can Determine the Metric Around Them?
Bin-Nun, A. (2010). Gravitational lensing of stars orbiting Sgr A* as a probe of the black hole metric in the Galactic center Physical Review D, 82 (6) DOI: 10.1103/PhysRevD.82.064009
From the abstract:
We show that a possible astrophysical experiment, detection of lensed images of stars orbiting close to Sgr A*, can provide insight into the form of the metric around a black hole. We model Sgr A* as a black hole and add in a 1/r2 term to the Schwarzschild metric near the black hole. … This knowledge will be useful in constraining any modified gravity theory that adds a similar term into the strong field near a black hole.
Sounds too good to be true?  It’s hard to say, but a technique to observationally determine the spacetime metric would be awfully exciting (and huge – to classical/quantum relativists, that is).
For more, see Black Hole May Offer Clues to Extra Dimensions.
Dark Energy and the Geometry of the Universe
Marinoni, C., & Buzzi, A. (2010). A geometric measure of dark energy with pairs of galaxies Nature, 468 (7323), 539-541 DOI: 10.1038/nature09577
From the abstract:
There is a purely geometric test of the expansion of the Universe (the Alcock–Paczynski test), which would provide an independent way of investigating the abundance () and equation of state () of dark energy. … Here we report an analysis of the symmetry properties of distant pairs of galaxies from archival data. This allows us to determine that the Universe is flat…
Speaking of observing metrics… this is a lot less exciting, however, as it takes in many more assumptions about the basic nature of the universe, galaxy distances, and, of course, dark energy.
For more, see Distant Galaxies Confirm Dark Energy’s Existence and Universe’s Flatness, Dark Energy Theory Gets a Boost From New Galactic Measurements, Cosmology: Geometry of the Universe.
Unified Origin of Matter and Dark Matter?
Davoudiasl, H., Morrissey, D., Sigurdson, K., & Tulin, S. (2010). Unified Origin for Baryonic Visible Matter and Antibaryonic Dark Matter Physical Review Letters, 105 (21) DOI: 10.1103/PhysRevLett.105.211304
The abstract:
We present a novel mechanism for generating both the baryon and dark matter densities of the Universe. A new Dirac fermion X carrying a conserved baryon number charge couples to the standard model quarks as well as a GeV-scale hidden sector. CP-violating decays of X, produced nonthermally in low-temperature reheating, sequester antibaryon number in the hidden sector, thereby leaving a baryon excess in the visible sector. The antibaryonic hidden states are stable dark matter. A spectacular signature of this mechanism is the baryon-destroying inelastic scattering of dark matter that can annihilate baryons at appreciable rates relevant for nucleon decay searches.
This is a surprisingly practical one (and really should be classified as high energy): A UBC team has proposed a new fermion that could explain dark matter, while linking to regular matter and the Standard Model.  Signatures related to this fermion X should be detectable, in the right experiment, making it a target for future searches.
For more, see The X factor, UBC physicists make atoms and dark matter add up.
Accurate Measurement in the Field of the Earth of the General-Relativistic Precession
Lucchesi, D., & Peron, R. (2010). Accurate Measurement in the Field of the Earth of the General-Relativistic Precession of the LAGEOS II Pericenter and New Constraints on Non-Newtonian Gravity Physical Review Letters, 105 (23) DOI: 10.1103/PhysRevLett.105.231103
From the abstract:
The pericenter shift of a binary system represents a suitable observable to test for possible deviations from the Newtonian inverse-square law in favor of new weak interactions between macroscopic objects. We analyzed 13 years of tracking data of the LAGEOS satellites with GEODYN II software but with no models for general relativity. From the fit of LAGEOS II pericenter residuals we have been able to obtain a 99.8% agreement with the predictions of Einstein’s theory
It’s always nice to see confirmations of general relativity, especially when they help put limits on poss... Read more »

Bin-Nun, A. (2010) Gravitational lensing of stars orbiting Sgr A* as a probe of the black hole metric in the Galactic center. Physical Review D, 82(6). DOI: 10.1103/PhysRevD.82.064009  

Marinoni, C., & Buzzi, A. (2010) A geometric measure of dark energy with pairs of galaxies. Nature, 468(7323), 539-541. DOI: 10.1038/nature09577  

Davoudiasl, H., Morrissey, D., Sigurdson, K., & Tulin, S. (2010) Unified Origin for Baryonic Visible Matter and Antibaryonic Dark Matter. Physical Review Letters, 105(21). DOI: 10.1103/PhysRevLett.105.211304  

Lucchesi, D., & Peron, R. (2010) Accurate Measurement in the Field of the Earth of the General-Relativistic Precession of the LAGEOS II Pericenter and New Constraints on Non-Newtonian Gravity. Physical Review Letters, 105(23). DOI: 10.1103/PhysRevLett.105.231103  

Eugenio Bianchi. (2010) Black Hole Entropy, Loop Gravity, and Polymer Physics. arXiv. arXiv: 1011.5628v1

  • July 26, 2010
  • 09:23 PM
  • 1,320 views

This Week in the Universe: July 20th – July 26th

by S.C. Kavassalis in The Language of Bad Physics

What have people been talking about this week in high energy physics, astrophysics, gravitation, general relativity and quantum gravity?... Read more »

Paul A Crowther, Olivier Schnurr, Raphael Hirschi, Norhasliza Yusof, Richard J Parker, Simon P Goodwin, & Hasan Abu Kassim. (2010) The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 Msun stellar mass limit. Monthly Notices of the Royal Astronomical Society. arXiv: 1007.3284v1

Brown, W., Anderson, J., Gnedin, O., Bond, H., Geller, M., Kenyon, S., & Livio, M. (2010) A GALACTIC ORIGIN FOR HE 0437–5439, THE HYPERVELOCITY STAR NEAR THE LARGE MAGELLANIC CLOUD. The Astrophysical Journal, 719(1). DOI: 10.1088/2041-8205/719/1/L23  

Hodges-Kluck, E., Reynolds, C., Miller, M., & Cheung, C. (2010) A DEEP OBSERVATION OF THE X-SHAPED RADIO GALAXY 4C 00.58: A CANDIDATE FOR MERGER-INDUCED REORIENTATION? . The Astrophysical Journal, 717(1). DOI: 10.1088/2041-8205/717/1/L37  

Seth Lloyd, Lorenzo Maccone, Raul Garcia-Patron, Vittorio Giovannetti, & Yutaka Shikano. (2010) The quantum mechanics of time travel through post-selected teleportation. arXiv. arXiv: 1007.2615v2

  • September 1, 2010
  • 01:20 PM
  • 1,289 views

This (Long) Week in the Universe: August 24th – September 1st

by S.C. Kavassalis in The Language of Bad Physics

What have people been talking about this week in high energy physics, astrophysics, gravitation, general relativity and quantum gravity?... Read more »

Lisa J. Kewley, David Rupke, H. Jabran Zahid, Margaret J. Geller, & Elizabeth J. Barton. (2010) Metallicity Gradients and Gas Flows in Galaxy Pairs. arXiv. DOI: 1008.2204  

Mayer L, Kazantzidis S, Escala A, & Callegari S. (2010) Direct formation of supermassive black holes via multi-scale gas inflows in galaxy mergers. Nature, 466(7310), 1082-4. PMID: 20740009  

Mikhail Gorchtein, Stefano Profumo, & Lorenzo Ubaldi. (2010) Probing Dark Matter with AGN Jets. arXiv. arXiv: 1008.2230v1

J. K. Webb, J. A. King, M. T. Murphy, V. V. Flambaum, R. F. Carswell, & M. B. Bainbridge. (2010) Evidence for spatial variation of the fine structure constant. arXiv. arXiv: 1008.3907v1

Harold V. Parks, & James E. Faller. (2010) A Simple Pendulum Determination of the Gravitational Constant. Phys. Rev. Let. arXiv: 1008.3203v2

L. Borsten, D. Dahanayake, M. J. Duff, A. Marrani, & W. Rubens. (2010) Four-qubit entanglement from string theory. Physical Review Letters. arXiv: 1005.4915v2

  • November 24, 2010
  • 10:56 AM
  • 1,192 views

This “Week” in the Universe: November 9th – November 22nd

by S.C. Kavassalis in The Language of Bad Physics

Astrophysics and Gravitation:
Fundamental constants: Big G revisited
Davis, R. (2010). Fundamental constants: Big G revisited Nature, 468 (7321), 181-183 DOI: 10.1038/468181b

Credit: Nature. a, A spherical 'source mass' (ms) is brought near a pendulum's spherical bob (the 'test mass', mt) and causes the bob to move a small distance z from its usual resting position (grey). The gravitational force between the two masses (left side of equation), which depends on Newton's constant (G), can be obtained from a measurement of z provided that k is known (see b). b, The value of k is found by measuring the period (P) of the freely swinging pendulum. To compute the value of G, we need measurements of L, z, ms and P (but not mt). Parks and Faller's experiment was based on four cylindrical source masses of 100 kilograms each, two pendulums and many other refinements.
From the abstract:
Measuring Newton’s constant of gravitation is a difficult task, because gravity is the weakest of all the fundamental forces. An experiment involving two simple pendulums provides a seemingly accurate but surprising value.

For more, see Fundamental constants: Big G revisted.
Galaxy Zoo Supernovae
Galaxy Zoo (2010). Galaxy Zoo Supernovae arXiv arXiv: 1011.2199v2
This paper presents the first results from a new citizen science project: Galaxy Zoo Supernovae which, with 2500 volunteers, has categorized almost 14,000 supernovae candidates.
For more, see Galaxy Zoo paper goes supernova.
“Youngest” Nearby Black Hole
Credits: X-ray: NASA/CXC/SAO/D.Patnaude et al, Optical: ESO/VLT, Infrared: NASA/JPL/Caltech
From the Press Release:
This composite image shows a supernova within the galaxy M100 that may contain the youngest known black hole in our cosmic neighborhood. In this image, Chandra’s X-rays are colored gold, while optical data from ESO’s Very Large Telescope are shown in red, green, and blue, and infrared data from Spitzer are red. The location of the supernova, known as SN 1979C, is labeled… This approximately 30-year age, plus its relatively close distance, makes SN 1979C the nearest example where the birth of a black hole has been observed, if the interpretation by the scientists is correct.
Sure, black holes can have finite age, that seems perfectly reasonable… well no, not really.  The “age” of a black hole is an exceptionally complicated, verging on philosophical, matter that I’ll have to write about.
For more, see Black Hole Baby Spotted Being Born, Youngest nearby black hole found, Youngest Nearby Black Hole.
High Energy Physics and Particles:
Trapped Antihydrogen
Andresen, G., & et al. (2010). Trapped antihydrogen Nature DOI: 10.1038/nature09610
From the abstract:
Antihydrogen, the bound state of an antiproton and a positron, has been produced2, 3 at low energies at CERN (the European Organization for Nuclear Research) since 2002. Antihydrogen is of interest for use in a precision test of nature’s fundamental symmetries. … Here we demonstrate trapping of antihydrogen atoms. …This result opens the door to precision measurements on anti-atoms, which can soon be subjected to the same techniques as developed for hydrogen.
For more, see Antiatoms Bottled for First Time, Antimatter atoms held captive by physicists.
General Relativity, Quantum Gravity, et al.:
Pre-Big-Bang Penrose
V. G. Gurzadyan, & R. Penrose (2010). Concentric circles in WMAP data may provide evidence of violent pre-Big-Bang activity arXiv arXiv: ... Read more »

Davis, R. (2010) Fundamental constants: Big G revisited. Nature, 468(7321), 181-183. DOI: 10.1038/468181b  

Galaxy Zoo. (2010) Galaxy Zoo Supernovae. arXiv. arXiv: 1011.2199v2

Andresen, G., & et al. (2010) Trapped antihydrogen. Nature. DOI: 10.1038/nature09610  

V. G. Gurzadyan, & R. Penrose. (2010) Concentric circles in WMAP data may provide evidence of violent pre-Big-Bang activity. arXiv. arXiv: 1011.3706v1

Belgiorno, F., Cacciatori, S., Clerici, M., Gorini, V., Ortenzi, G., Rizzi, L., Rubino, E., Sala, V., & Faccio, D. (2010) Hawking Radiation from Ultrashort Laser Pulse Filaments. Physical Review Letters, 105(20). DOI: 10.1103/PhysRevLett.105.203901  

Alberto S. Cattaneo, & Florian Schaetz. (2010) Introduction to supergeometry. arXiv. arXiv: 1011.3401v1

Benjamin Bahr, Bianca Dittrich, & Song He. (2010) Coarse graining theories with gauge symmetries. arXiv. arXiv: 1011.3667v1

Veronika E. Hubeny. (2010) The Fluid/Gravity Correspondence: a new perspective on the Membrane Paradigm. arXiv. arXiv: 1011.4948v1

  • November 2, 2010
  • 11:38 AM
  • 1,168 views

This Week in the Universe: October 26th – November 1st

by S.C. Kavassalis in The Language of Bad Physics

Astrophysics and Gravitation:
Hubble Tries to See into the Future
Illustration Credit: NASA, ESA, and G. Bacon (STScI), Science Credit: NASA, ESA, and J. Anderson and R. van der Marel (STScI)
From NASA, ESA, and J. Anderson and R. van der Marel (STScI):
The multicolor snapshot, at top, taken with Wide Field Camera 3 aboard NASA’s Hubble Space Telescope, captures the central region of the giant globular cluster Omega Centauri. All the stars in the image are moving in random directions, like a swarm of bees. Astronomers used Hubble’s exquisite resolving power to measure positions for stars in 2002 and 2006.
From these measurements, they can predict the stars’ future movement. The bottom illustration charts the future positions of the stars highlighted by the white box in the top image. Each streak represents the motion of the star over the next 600 years. The motion between dots corresponds to 30 years.
By precisely observing the stars in Omega Centauri, a 10 million star globular cluster within our galaxy, the NASA/ESA team has been able to predict the stars’ movements over the next 10,000 years.  Considering how many variables are in this system, this is an awfully impressive achievement.
For more, see Hubble Data Used to Look 10,000 Years into the Future.
High Energy Physics and Particles:
ANITA Balloon sees Cosmic Rays by Accident
Hoover, S., & et al. (2010). Observation of Ultrahigh-Energy Cosmic Rays with the ANITA Balloon-Borne Radio Interferometer Physical Review Letters, 105 (15) DOI: 10.1103/PhysRevLett.105.151101
Credit: Physical Review Letters » Covers » Vol. 105, Iss. 15- Locations of direct (black) and reflected (red) detection of ultrahigh energy cosmic ray events by the ANITA balloon experiment over Antarctica. The field of view is delineated by the dashed blue line.
From the abstract:
We report the observation of 16 cosmic ray events with a mean energy of 1.5×1019 eV via radio pulses originating from the interaction of the cosmic ray air shower with the Antarctic geomagnetic field, a process known as geosynchrotron emission. We present measurements in the 300–900 MHz range, which are the first self-triggered, first ultrawide band, first far-field, and the highest energy sample of cosmic ray events collected with the radio technique. Their properties are inconsistent with current ground-based geosynchrotron models.
The ANITA Experiment, while on the hunt for cosmic neutrinos, ended up seeing 16 exceptionally high energy cosmic ray events (particles with energy several orders of magnitude greater than those made in the LHC).  Accidental observations are always fun, especially when they suggest a new technique for observing known phenomena.  Perhaps radio interferometer equipped balloons will now be used to detect these rare cosmic ray events.
For more, see Antarctic balloon sees particles with a million times more energy than the Large Hadron Collider.
Confirmed Top Quark Observation in the LHC
CMS Collaboration (2010). First Measurement of the Cross Section for Top-Quark Pair Production in Proton-Proton Collisions at sqrt(s)=7 TeV arXiv arXiv: 1010.5994v1
Exciting news! The CMS Collaboration has published their first confirmed observations of top quark production at the LHC this week.  This is especially exciting because it means that we’ll be able to study top quarks in multi-TeV proton-proton collisions for the first time.  At the Tevatron, top quark pairs are mainly produced via quark-antiquark annihilation, while at the LHC top quark pair production is expected to be dominated by a gluon fusion process.  Thus, observing top quark production is crucial to our understanding of this new mechanism. This is an important step in the early physics program at the LHC, since, “many signatures of new physics models accessible at the LHC either suffer from top-quark production as a significant background or contain top quarks themselves.”
The US at the Large Hadron Collider Photo of the Week

Credit: US/LHC - Candidate W-boson decay to tau and neutrino in ATLAS
The US/LHC has started an Event of the Week flickr account, showcasing an exciting and beautiful particle event from the current LHC runs every week.  This weeks was a candidate W-boson decaying into a tau and a neutrino within the ATLAS detector!
General Relativity, Quantum Gravity, et al.:
Want to Learn More about Gauge Gravity?
Andrew Randono (2010). Gauge Gravity: a forward-looking introduction arXiv arXiv: 1010.5822v1
... Read more »

Hoover, S., & et al. (2010) Observation of Ultrahigh-Energy Cosmic Rays with the ANITA Balloon-Borne Radio Interferometer. Physical Review Letters, 105(15). DOI: 10.1103/PhysRevLett.105.151101  

CMS Collaboration. (2010) First Measurement of the Cross Section for Top-Quark Pair Production in Proton-Proton Collisions at sqrt(s). arXiv. arXiv: 1010.5994v1

Andrew Randono. (2010) Gauge Gravity: a forward-looking introduction. arXiv. arXiv: 1010.5822v1

  • November 10, 2010
  • 10:30 AM
  • 1,105 views

This Week in the Universe: November 2nd – November 8th

by S.C. Kavassalis in The Language of Bad Physics

Hot topics in astrophysics, gravitation, high energy, and quantum gravity for the week.... Read more »

Negrello, M., & et al. (2010) The Detection of a Population of Submillimeter-Bright, Strongly Lensed Galaxies. Science, 330(6005), 800-804. DOI: 10.1126/science.1193420  

Aguilar-Arevalo, A., & et al. (2010) Event Excess in the MiniBooNE Search for ν[over ¯]_{μ}→ν[over ¯]_{e} Oscillations. Physical Review Letters, 105(18). DOI: 10.1103/PhysRevLett.105.181801  

David J. Toms. (2010) Quantum gravitational contributions to quantum electrodynamics. Nature 468:56-59,2010. arXiv: 1010.0793v1

  • September 1, 2010
  • 01:00 PM
  • 1,090 views

The "Bad" Language of Physics

by S.C. Kavassalis in The Language of Bad Physics

One of the things I sometimes find myself writing about is the “bad” language used by physicists. Sometimes we say Riemannian when we really should say psuedo-Riemannian, sometimes we call something a metric when it really is a line element – the kind of nitpicky pet-peeves that practically everyone has about literature in their field. Today, I’m going to be talking about the bad language in physics in a totally different context however.... Read more »

Regge, T. (1961) General relativity without coordinates. Il Nuovo Cimento, 19(3), 558-571. DOI: 10.1007/BF02733251  

Galassi, M. (1993) Lapse and shift in Regge calculus. Physical Review D, 47(8), 3254-3264. DOI: 10.1103/PhysRevD.47.3254  

Kheyfets A, LaFave NJ, & Miller WA. (1990) Null-strut calculus. II. Dynamics. Physical review D: Particles and fields, 41(12), 3637-3651. PMID: 10012308  

ALPER ÜNGÖR, & ALLA SHEFFER. (2002) PITCHING TENTS IN SPACE-TIME: MESH GENERATION FOR DISCONTINUOUS GALERKIN METHOD. International Journal of Foundations of Computer Science , 13(2). info:/10.1142/S0129054102001059

  • January 18, 2011
  • 10:09 AM
  • 1,072 views

This Week in the Universe: January 11th – January 17th

by S.C. Kavassalis in The Language of Bad Physics

Astrophysics and Gravitation:
Planck’s Early Results
Planck Collaboration (2011). Planck Early Results: The Planck mission arXiv arXiv: 1101.2022v1
The Early Results Papers from the Planck Collaboration are based on the data acquired by the Planck satellite between August 13th, 2009 to June 6th, 2010.  This work is “an overview of the history of Planck in its first year of operations” and was released along side Planck’s Early Release Compact Source Catalogue, “the first data product based on Planck to be released publicly”.  Andrew Jaffe has a great summary of the results so far.
For more, see Planck: First results.

Dark Galaxies?
Sukanya Chakrabarti, Frank Bigiel, Philip Chang, & Leo Blitz (2011). Finding Dark Galaxies From Their Tidal Imprints arXiv arXiv: 1101.0815v1
From the abstract:
We describe ongoing work on a new method that allows one to determine the mass and relative position (in galactocentric radius and azimuth) of galactic companions purely from analysis of observed disturbances in gas disks….This approach has broad implications for many areas of astrophysics — for the indirect detection of dark matter (or dark-matter dominated dwarf galaxies), and for galaxy evolution in its use as a decipher for the dynamical impact of satellites on galactic disks. Here, we provide a proof of principle of the method by applying it to infer and quantitatively characterize optically visible galactic companions of local spirals, from the analysis of observed disturbances in outer gas disks.”
The tl;dr version is that they have a technique for detecting companion galaxies that need not be optically visible (which is great, because sometimes we can’t see things for reasons other than them being made out of dark matter) and this paper acts as a proof of concept by using it to correctly infer and characterize galaxies that we already can observe.  Does it say anything about having detected a dark matter galaxy? No.  If such things existed it could be used to detect them (if they were acting as companion to regular matter galaxies), but it doesn’t say anything about their existence.  I genuinely feel I read a different paper than the authors who wrote the below two articles.
For more, see Dark-Matter Galaxy Detected: Hidden Dwarf Lurks Nearby?, The Milky Way might be surrounded by invisible dark matter galaxies.
Not So Standard Standard Candle
This image layout illustrates how NASA's Spitzer Space Telescope was able to show that a "standard candle" used to measure cosmological distances is shrinking -- a finding that affects precise measurements of the age, size and expansion rate of our universe. Image credit: NASA/JPL-Caltech/Iowa State
From the NASA press release:
Astronomers have turned up the first direct proof that “standard candles” used to illuminate the size of the universe, termed Cepheids, shrink in mass, making them not quite as standard as once thought. The findings, made with NASA’s Spitzer Space Telescope, will help astronomers make even more precise measurements of the size, age and expansion rate of our universe.
Obviously, this is rather significant, but the immediate consequence of standard candles not being standard isn’t that it will allow for accurate future measurements of things, it’s that it calls into question the current measurements we have (for things like galactic distances).
From lead author of the study, Massimo Marengo*:
When using Cepheids as standard candles, we must be extra careful because, much like actual candles, they are consumed as they burn.
*He’s also an author on a wonderfully titled paper, Close Binaries with Infrared Excess: Destroyers of Worlds?.
For more, see Cosmology Standard Candle not so Standard After All.
Dynamical Coupled Dark Energy?

Baldi, M., & Pettorino, V. (2011). High-z massive clusters as a test for dynamical coupled dark energy Monthly Notices of the Royal Astronomical Society: Letters DOI: 10.1111/j.1745-3933.2010.00975.x
Abstract:
The recent detection by Jee et al. of the massive cluster XMMU J2235.3−2557 at a redshift z≈ 1.4, with an estimated mass M324= (6.4 ± 1.2) × 1014 M⊙, has been claimed to be a possible challenge to the standard ΛCDM cosmological model. More specifically, the probability to detect such a cluster has been estimated to be ∼0.005 if a ΛCDM model with Gaussian initial conditions is assumed, resulting in a 3σ discrepancy from the standard cosmological model. In this Letter we propose to use high-redshift clusters as the one detected in Jee et al. to compare the cosmological constant scenario with interacting dark energy models. We show that coupled dark energy models, where an interaction is present between dark energy and cold dark matter, can significantly enhance the probability to observe very massive clusters at high redshift.
So I actually haven’t read this paper yet, but was told by a cosmologist frien... Read more »

Planck Collaboration. (2011) Planck Early Results: The Planck mission. arXiv. arXiv: 1101.2022v1

Sukanya Chakrabarti, Frank Bigiel, Philip Chang, & Leo Blitz. (2011) Finding Dark Galaxies From Their Tidal Imprints. arXiv. arXiv: 1101.0815v1

Baldi, M., & Pettorino, V. (2011) High-z massive clusters as a test for dynamical coupled dark energy. Monthly Notices of the Royal Astronomical Society: Letters. DOI: 10.1111/j.1745-3933.2010.00975.x  

Turok, N. (2011) Particle physics: Beyond Feynman's diagrams. Nature, 469(7329), 165-166. DOI: 10.1038/469165a  

  • October 11, 2010
  • 06:59 PM
  • 1,019 views

This Week in the Universe: October 5th – October 11th

by S.C. Kavassalis in The Language of Bad Physics

Astrophysics and Gravitation:
Early Universe was Overheated, says NASA
Michael Shull, Kevin France, Charles Danforth, Britton Smith, & Jason Tumlinson (2010). Hubble/COS Observations of the Quasar HE 2347-4342: Probing the Epoch of He II Patchy Reionization at Redshifts z = 2.4-2.9 arXiv arXiv: 1008.2957v1
Credit: NASA/Michael Shull, University of Colorado
From the Press Release:
During a period of universal warming 11 billion years ago, quasars — the brilliant core of active galaxies — produced fierce radiation blasts that stunted the growth of some dwarf galaxies for approximately 500 million years.  This important conclusion comes from a team of astronomers that used the new capabilities of NASA’s Hubble Space Telescope to probe the invisible, remote universe. The team’s results will be published in… The Astrophysical Journal.
For more, see Hubble Astronomers Uncover an Overheated Early Universe.
Dark Matter, Neutron Stars, and Strange Quark Matter, Oh My!
Perez-Garcia, M., Silk, J., & Stone, J. (2010). Dark Matter, Neutron Stars, and Strange Quark Matter Physical Review Letters, 105 (14) DOI: 10.1103/PhysRevLett.105.141101
The abstract:
We show that self-annihilating weakly interacting massive particle (WIMP) dark matter accreted onto neutron stars may provide a mechanism to seed compact objects with long-lived lumps of strange quark matter, or strangelets, for WIMP masses above a few GeV. This effect may trigger a conversion of most of the star into a strange star. We use an energy estimate for the long-lived strangelet based on the Fermi-gas model combined with the MIT bag model to set a new limit on the possible values of the WIMP mass that can be especially relevant for subdominant species of massive neutralinos.
For more, see Does dark matter trigger strange stars?.
High Energy Physics and Particles:
Hey, this isn’t research news!
Yeah, it’s not… But, for anyone who will be in Manchester from October 23rd – 27th, 2010 should make sure they check out Super K Sonic Booooum!
This large installation consists of a 22 meter long ‘river’ of water running through a tunnel lined with thousands of silver balloons (photomultiplier tubes). Members of the public embark on a boat, pulled through the tunnel on a submerged track using a pulley system, with sound and lighting effects, and with an expert particle physicist navigator as a guide. On the journey they learn of neutrinos, their role in the Universe and how scientists detect them. All crew members must first don white Tyvek suits, wellies and hard hats or else face the wrath of Nelly the security chief, at the entrance of the tunnel. This installation is designed to deliver physically thrilling experiences; emerging the audience on a journey through the physics of the Universe.
Workshop on Sunday 24 October – 2pm – 4pm
Capture the Invisible: Craft and Science in particle physics.
In this workshop you will get the chance to make your own photomultiplier tube to capture the invisible in your own bedroom! Designed by Nelly Ben Hayoun in collaboration with Dr Jonathan Perkin, physicist and glassblower Jochen Holz
For more, see Super K Sonic Booooum.
SuperB Project Preparing for Construction!
SuperB Collaboration, E. Grauges et al., Francesco Forti, Blair N. Ratcliff, & David Aston (2010). SuperB Progress Reports — Detector arXiv arXiv: 1007.4241v1
It looks like funding for the SuperB Collaboration will come through and see the new experiment built in Frascati.  I hope the Italians take this great opportunity to make many “flavour country” jokes.
From the press release:
The most elementary components of matter, quarks and leptons, have been found, as the result of 100 years of research, to be organized into three replicating “families”. The reason for this specific number or organization remains a full mystery. Flavor physics, the detailed understanding of the relationship between these families and the comparison between properties of matter and antimatter, is one of the most promising ways to explore new physics, quite complementary to the energy frontier research most notably pursued at the CERN LHC collider. Different kinds of new physics have different effects on rare decays of bottom and charmed quarks and of heavy tau leptons. These particles are all produced at SuperB in unparalleled abundance, making possible for the first time measurements of the precision required to be sensitive to the details of new physics uncovered at CERN.
For more, see SuperB project moves forward, preparing for construction.
Bonner Nuclear Lab to Study Quark-Gluon Plasma
Credit: Frank Geurts/Rice University
It was a good week to get funding for high-energy experiments.
From the Press Release:
Rice University’s Bonner Nuclear Lab has won a $1.175 million grant that will support its research on high-density and hot nuclear matter.  Rice physicist Frank Geurts, who has spent his career looking for clues to the basic elements of the universe by smashing the nuclear contents of gold, lead and other heavy atoms, said the Department of Energy grant will facilitate his group’s transition from constructing and commissioning a highly complex detector system to using that machinery to do basic research.
Video: Quark gluon plasma (QGP)
For more, see Grant advances quark-gluon ... Read more »

Michael Shull, Kevin France, Charles Danforth, Britton Smith, & Jason Tumlinson. (2010) Hubble/COS Observations of the Quasar HE 2347-4342: Probing the Epoch of He II Patchy Reionization at Redshifts z . arXiv. arXiv: 1008.2957v1

Perez-Garcia, M., Silk, J., & Stone, J. (2010) Dark Matter, Neutron Stars, and Strange Quark Matter. Physical Review Letters, 105(14). DOI: 10.1103/PhysRevLett.105.141101  

SuperB Collaboration, E. Grauges et al., Francesco Forti, Blair N. Ratcliff, & David Aston. (2010) SuperB Progress Reports -- Detector. arXiv. arXiv: 1007.4241v1

Gary Felder, & Stephanie Erickson. (2010) CurvedLand: An Applet for Illustrating Curved Geometry without Embedding. arXiv. arXiv: 1010.1426v1

Poltis, R., & Stojkovic, D. (2010) Can Primordial Magnetic Fields Seeded by Electroweak Strings Cause an Alignment of Quasar Axes on Cosmological Scales?. Physical Review Letters, 105(16). DOI: 10.1103/PhysRevLett.105.161301  

  • October 26, 2010
  • 11:24 AM
  • 971 views

This “Week” in the Universe: October 12th – October 25th

by S.C. Kavassalis in The Language of Bad Physics

Two weeks of news in one!
Astrophysics and Gravitation:
Did We Already Have the Data to Show Dark Matter Annihilation?
Dan Hooper, & Lisa Goodenough (2010). Dark Matter Annihilation in The Galactic Center As Seen by the Fermi Gamma Ray Space Telescope arXiv arXiv: 1010.2752v1
Analyzing old data from the Fermi Gamma Ray Space Telescope, the authors have noticed gamma ray emissions consistent with predictions for a certain type of dark matter.  Unfortunately, these things are never nice, clear problems where they’ve definitely seen dark matter or have definitely not seen it, but it’s an exciting collection of data points for astrophysicists who are on the dark matter hunt.  It could turn out to be the evidence that people have been looking for, but it’s too early to say anything definitively.
For more, see Signs of Destroyed Dark Matter Found in Milky Way’s Core, Fermilab theorist sees dark matter evidence in public data.
Weighing Planets with Pulsars
Champion, D., et al. (2010). MEASURING THE MASS OF SOLAR SYSTEM PLANETS USING PULSAR TIMING The Astrophysical Journal, 720 (2) DOI: 10.1088/2041-8205/720/2/L201
What can’t pulsars do? The team, using an array of pulsars (PSRs J0437–4715, J1744–1134, J1857+0943, J1909–3744), have identified the masses of the planetary system from Mercury to Saturn, in agreement with the best-known masses determined by spacecraft and other observations.  This new method relies on the incredibly predictable nature of pulsars and solar system ephemeris (the past and future positions of the Sun, Moon, and nine planets in three-dimensional space).
From the authors:
While spacecraft are likely to produce the most accurate measurements for individual solar system bodies, the pulsar technique is sensitive to planetary system masses and has the potential to provide the most accurate values of these masses for some planets.
Practical!
For more, see A New Way to Weigh Planets.
A New Standard Candle?
Poznanski, D., Nugent, P., & Filippenko, A. (2010). TYPE II-P SUPERNOVAE AS STANDARD CANDLES: THE SDSS-II SAMPLE REVISITED The Astrophysical Journal, 721 (2), 956-959 DOI: 10.1088/0004-637X/721/2/956
For years, Type Ia supernovae have been used as standard candles to measure cosmic distances; they were especially important for the measurements that determined that the expansion of the universe ws accelerating.  Now, some astrophysicists are suggesting that for even higher accuracy, we use Type II supernovae as well.  Initially, Type II supernovae weren’t used as standard candles because we weren’t as sure about their properties and actual brightness as we were for Type Ia supernovae.  Using additional markers to gauge cosmic distances could help confirm and strengthen current observations, as well as discover inconsistencies.
Adam Burrows, astrophysicist at Princeton University:
It is unlikely that this technique will be able to compete with Ia, but it can contribute complementary cosmic information. It is coming into its own.
For more, see Alternative yardstick to measure the universe.
Dark Matter in the Sun, Revisited
Lopes, I., & Silk, J. (2010). Neutrino Spectroscopy Can Probe the Dark Matter Content in the Sun Science, 330 (6003), 462-462 DOI: 10.1126/science.1196564
The abstract:
After being gravitationally captured, low-mass cold dark-matter particles (mass range from 5 to ~50 x 109 electron volts) are thought to drift to the center of the Sun and affect its internal structure. Solar neutrinos provide a way to probe the physical processes occurring in the Sun’s core. Solar neutrino spectroscopy, in particular, is expected to measure the neutrino fluxes produced in nuclear reactions in the Sun. Here, we show how the presence of dark-matter particles inside the Sun will produce unique neutrino flux distributions in 7Be- and 8B-, as well as 13N-, 15O-, and 17F-.
Finally, a credible sounding experiment to test this dark-matter-in-the-sun-hypothesis, discover that there is no cold dark matter in the sun, and convince people to stop taking things seriously just because they technically “could” be possible.  We’re not 100% sure of the consistency of the moon either, therefore I propose it’s full of anaerobic unicorns.
For more, see Neutrino Spectroscopy Can Probe the Dark Matter Content in the Sun.
New Oldest/Farthest Object in the Universe*
... Read more »

Dan Hooper, & Lisa Goodenough. (2010) Dark Matter Annihilation in The Galactic Center As Seen by the Fermi Gamma Ray Space Telescope. arXiv. arXiv: 1010.2752v1

Champion, D., Hobbs, G., Manchester, R., Edwards, R., Backer, D., Bailes, M., Bhat, N., Burke-Spolaor, S., Coles, W., Demorest, P.... (2010) MEASURING THE MASS OF SOLAR SYSTEM PLANETS USING PULSAR TIMING. The Astrophysical Journal, 720(2). DOI: 10.1088/2041-8205/720/2/L201  

Poznanski, D., Nugent, P., & Filippenko, A. (2010) TYPE II-P SUPERNOVAE AS STANDARD CANDLES: THE SDSS-II SAMPLE REVISITED. The Astrophysical Journal, 721(2), 956-959. DOI: 10.1088/0004-637X/721/2/956  

Lopes, I., & Silk, J. (2010) Neutrino Spectroscopy Can Probe the Dark Matter Content in the Sun. Science, 330(6003), 462-462. DOI: 10.1126/science.1196564  

Lehnert, M., Nesvadba, N., Cuby, J., Swinbank, A., Morris, S., Clément, B., Evans, C., Bremer, M., & Basa, S. (2010) Spectroscopic confirmation of a galaxy at redshift z . Nature, 467(7318), 940-942. DOI: 10.1038/nature09462  

Raphael Bousso, Ben Freivogel, Stefan Leichenauer, & Vladimir Rosenhaus. (2010) Eternal inflation predicts that time will end. arXiv. arXiv: 1009.4698v1

Sabine Hossenfelder. (2010) Experimental Search for Quantum Gravity. arXiv. arXiv: 1010.3420v1

Major, S. (2010) Shape in an atom of space: exploring quantum geometry phenomenology. Classical and Quantum Gravity, 27(22), 225012. DOI: 10.1088/0264-9381/27/22/225012  

Sachdev, S. (2010) Holographic Metals and the Fractionalized Fermi Liquid. Physical Review Letters, 105(15). DOI: 10.1103/PhysRevLett.105.151602  

Henrique Gomes, Sean Gryb, & Tim Koslowski. (2010) Einstein gravity as a 3D conformally invariant theory. arXiv. arXiv: 1010.2481v1

  • October 18, 2010
  • 12:00 PM
  • 939 views

Guest Post: The fine-structure constant is probably constant by Sean Carroll

by S.C. Kavassalis in The Language of Bad Physics

This is the first guest post on The Language of Bad Physics by Cosmic Variance‘s Sean Carroll.  This post is cross-posted on Cosmic Variance.
A few weeks ago there was a bit of media excitement about a somewhat surprising experimental result. Observations of quasar spectra indicated that the fine structure constant, the parameter in physics that describes the strength of electromagnetism, seems to be slightly different on one side of the universe than on the other. The preprint is here.
Remarkable, if true. The fine structure constant, usually denoted α, is one of the most basic parameters in all of physics, and it’s a big deal if it’s not really constant. But how likely is it to be true? This is the right place to trot out the old “extraordinary claims require extraordinary evidence” chestnut. It’s certainly an extraordinary claim, but the evidence doesn’t really live up to that standard. Maybe further observations will reveal truly extraordinary evidence, but there’s no reason to get excited quite yet.
Chad Orzel does a great job of explaining why an experimentalist should be skeptical of this result. It comes down to the figure below: a map of the observed quasars on the sky, where red indicates that the inferred value of α is slightly lower than expected, and blue indicates that it’s slightly higher. As Chad points out, the big red points are mostly circles, while the big blue points are mostly squares. That’s rather significant, because the two shapes represent different telescopes: circles are Keck data, while squares are from the VLT (“Very Large Telescope”). Slightly suspicious that most of the difference comes from data collected by different instruments.

But from a completely separate angle, there is also good reason for theorists to be skeptical, which is what I wanted to talk about. Theoretical considerations will always be trumped by rock-solid data, but when the data are less firm, it makes sense to take account of what we already think we know about how physics works.
The crucial idea here is the notion of a scalar field. That’s just fancy physics-speak for a quantity which takes on a unique numerical value at every point in spacetime. In quantum field theory, scalar fields lead to spinless particles; the Higgs field is a standard example. (Other particles, such as electrons and photons, arise from more complicated geometric objects — spinors and vectors, respectively.)
The fine structure constant is a scalar field. We don’t usually think of it that way, since we usually reserve the term “field” for something that actually varies from place to place rather than remaining constant, but strictly speaking it’s absolutely true. So, while it would be an amazing and Nobel-worthy result to show that the fine structure constant were varying, it wouldn’t be hard to fit it into the known structure of quantum field theory; you just take a scalar field that is traditionally thought of as constant and allow it to vary from place to place and time to time.
That’s not the whole story, of course, When a field varies from point to point, those variations carry energy. Think of pulling a spring, or twisting a piece of metal. For a scalar field, there are three important contributions to the energy: kinetic energy from the field varying in time, gradient energy from the field varying in space, and potential energy associated with the value of the field at every point, unrelated to how it is changing.
For the fine structure constant, the observations imply that it changes by only a very tiny bit from one end of the universe to the other. So we really wouldn’t expect the gradient energy to be very large, and there’s correspondingly no reason to expect the kinetic energy to matter much.
The potential energy is a different matter. The potential is similar to the familiar example of a ball rolling in a hill; how steep the potential is near its minimum is related to the mass of the field. For most scalar fields, like the Higgs field, the potential is extremely steep; this means that if you displace the field from the minimum of its potential by just a bit, it will tend to immediately roll back down.

A priori, we don’t know ahead of time what the potential should look like; specifying it is part of defining the theory. But quantum field theory gives us clues. At heart, the world is quantum, not classical; the “value” of the scalar field is actually the expectation value of a quantum operator. And such an operator gets contributions from the intrinsic vibrations of all the other fields that it couples to — in this case, every kind of charged particle in the universe. What we actually observe is not the “bare” form of the potential, but the renormalized value, which takes into account the accumulated effects of various forms of virtual particles popping in and out of the quantum vacuum.
The basic effect of renormalization on a scalar field potential is easy to summarize: it makes the mass large. So, if you didn’t know any better, you would expect the potential to be as steep as it could possibly be — probably up near the Planck scale. The Higgs boson probably has a mass of order a hundred times the mass of a proton, which sounds large — but it’s actually a big mystery why it isn’t enormously larger. That’s the hierarchy problem of particle physics.
So what about our friend the fine structure constant? Well, if these observations are correct, the field would have to have an extremely tiny mass — otherwise it wouldn’t vary smoothly over the universe, it would just slosh harmlessly around the bottom of its potential. Plugging in numbers, we find that the mass has to be something like 10-42 GeV or less, where 1 GeV is the mass of the proton. In other words: extremely, mind-bogglingly small.
But there’s no known reason for the mass of the scalar field underlying the fine structure constant to be anywhere near that small. This was established in some detail by Banks, Dine, and Douglas. They affirmed our intuition, that a tiny change in the fine structure constant should be associated with a huge change in potential energy.
Now, there are loopholes — there are always loopholes. In this case, you could possibly prevent those quantum fluctuations from renormalizing your scalar-field potential simply by shielding the field from interactions with other fields. That is, you can impose a symmetry that forbids the field from coupling to other forms of matter, or only lets it couple in certain very precise ways; then you could at least imagine keeping the mass small. That’s essentially the strategy behind the supersymmetric solution to the hierarchy problem.
Problem is, that route is a complete failure when we turn to the fine structure constant, for a very basic reason: we can’t prevent it from coupling to other fields, it’s the parameter that governs the strength of electromagnetism! So like it or not, it will couple to the electromagnetic field and all charged particles in nature. I talked about this in one of my own papers from a few years ago. I was thinking about time-dependent scalars, not spatially-varying ones, but the principles are precisely the same.
That’s why theorists are skeptical of this claimed result. Not that it’s impossible; if the data stand up, it will present a serious challenge to our theoretical prejudices, but that will doubtless goad theorists into being more clever than usual in trying to explain it. Rather, the point is that we have good reasons to suspect that the fine structure constant really is constant; it’s not just a fifty-fifty kind of choice. And given those good reasons, we need really good data to change our minds. That’s not what we have yet — but what we have is certainly more than enough motivation to keep searching.

... Read more »

J. K. Webb, J. A. King, M. T. Murphy, V. V. Flambaum, R. F. Carswell, & M. B. Bainbridge. (2010) Evidence for spatial varia. arXiv. arXiv: 1008.3907v1

  • January 10, 2011
  • 01:23 PM
  • 937 views

This Week in the Universe: January 4th – January 10th

by S.C. Kavassalis in The Language of Bad Physics

Astrophysics and Gravitation:
Supermassive Black Hole Surprise?
CREDIT: Reines, et al., David Nidever, NRAO/AUI/NSF, NASA
The dwarf galaxy Henize 2-10, seen in visible light by the Hubble Space Telescope. The central, light-pink region shows an area of radio emission, seen with the Very Large Array. This area indicates the presence of a supermassive black hole drawing in material from its surroundings. This also is indicated by strong X-ray emission from this region detected by the Chandra X-Ray Observatory.
Astronomers have identified a supermassive black hole candidate at the centre of the dwarf galaxy Henize 2-10.  Amy Reines, one of the members of the discovery team, on why this is important:
This galaxy gives us important clues about a very early phase of galaxy evolution that has not been observed before.
For more, see Surprise: Dwarf Galaxy Harbors Supermassive Black Hole.
High Energy Physics and Particles:
Good-Bye to the Tevatron?
Obviously the big news of today is the rumour that the Tevatron will cease operations at the end of 2011.  We’re still waiting on the official announcement though.
New in Nuclear Fission
Andreyev, A., et al., (2010). New Type of Asymmetric Fission in Proton-Rich Nuclei Physical Review Letters, 105 (25) DOI: 10.1103/PhysRevLett.105.252502
An exotic fission process is studied and an exciting and anomalous asymmetry in the daughter masses is discussed.
As Abhishek Agarwal writes:
The ISOLDE team’s puzzling result hints that a very subtle interplay between macroscopic and microscopic interactions plays a deeper role in the fission process than expected and is likely to inspire detailed theoretical studies and further experiment.
Neat.
For more, see Unequal Parts.

General Relativity, Quantum Gravity, et al.:
Projective flatness in the quantisation of bosons and fermions
Siye Wu (2010). Projective flatness in the quantisation of bosons and fermions arXiv arXiv: 1008.5333v2
The abstract:
We compare the quantisation of linear systems of bosons and fermions. We recall the appearance of projectively flat connection and results on parallel transport in the quantisation of bosons. We then discuss pre-quantisation and quantisation of fermions using the calculus of fermionic variables. We then define a natural connection on the bundle of Hilbert spaces and show that it is projectively flat. This identifies, up to a phase, equivalent spinor representations constructed by various polarisations. We introduce the concept of metaplectic correction for fermions and show that the bundle of corrected Hilbert spaces is naturally flat. We then show that the parallel transport in the bundle of Hilbert spaces along a geodesic is the rescaled projection or the Bogoliubov transformation provided that the geodesic lies within the complement of a cut locus. Finally, we study the bundle of Hilbert spaces when there is a symmetry.
So I’m a sucker for nice math, and this paper has got that in spades.  If you want some beautiful geometry, and some quantum mechanics (which together, I firmly believe are critical to good quantum gravity), then this is well worth the read.
... Read more »

Andreyev, A., Elseviers, J., Huyse, M., Van Duppen, P., Antalic, S., Barzakh, A., Bree, N., Cocolios, T., Comas, V., Diriken, J.... (2010) New Type of Asymmetric Fission in Proton-Rich Nuclei. Physical Review Letters, 105(25). DOI: 10.1103/PhysRevLett.105.252502  

Siye Wu. (2010) Projective flatness in the quantisation of bosons and fermions. arXiv. arXiv: 1008.5333v2

  • February 22, 2011
  • 11:06 AM
  • 914 views

This “Week” in the Universe: February 1st – February 21st

by S.C. Kavassalis in The Language of Bad Physics

So I’ve been remiss in my reading lately, but here are my picks from the past few weeks.  We have Outstanding Problems in Galaxy Formation, Herschel on Dark Matter, Dark Matter Detection Discussed, “Symmetry Breaking” in Graphene?, Closed Timelike Curves and Postselection, Frame-Like Geometry of Double Field Theory, and Loop Lectures with Carlo Rovelli.
Astrophysics and Gravitation:

Outstanding Problems in Galaxy Formation
Joseph Silk (2011). Feedback in Galaxy Formation arXiv arXiv: 1102.0283v1
Abstract:
I review the outstanding problems in galaxy formation theory, and the role of feedback in resolving them. I address the efficiency of star formation, the galactic star formation rate, and the roles of supernovae and supermassive black holes.

Silk’s Figure 1. “The theoretical mass function of galaxies compared to the observed luminosity function.”

So, as most of us know, there are still quite a few puzzles when it comes to how galaxies form.  Joseph Silk has put together a little discussion on some of these problems, and, perhaps more interestingly, ways in which they can be rectified (or already have been). For example, cold dark matter simulations alone predicted more halo dwarf galaxies than were observed (called the “missing satellites” problem; see Kravtsov and pdf slides).  Through both a better understanding of observation (there were in fact more dwarfs out there than we though, they were just very faint) and more sophisticated models (taking into account baryonic physics too), this problem doesn’t seem so huge anymore (it’s not 100% resolved, mind you).  There are many other much less resolved issues when it comes to gravitation and galaxy formation that are also deserving of some serious study.

Herschel on Dark Matter
Alexandre Amblard, & et al. (2011). Sub-millimetre galaxies reside in dark matter halos with masses greater than 3×10^11 solar masses Nature arXiv: 1101.1080v1
From the press release:
ESA’s Herschel space observatory has discovered a population of dust-enshrouded galaxies that do not need as much dark matter as previously thought to collect gas and burst into star formation.
This is certainly good news for some galaxy formation theorists and another fun piece of the puzzle to think about.  The latest analysis of Herschel observations suggest the existence of galaxies that are roughly 300 billion solar masses but with as many stars as expected from a galaxy of 5000 billion solar masses (ie. that’s not got much dark matter in it).  This is quite fascinating, because most of the current theories dealing with galaxy formation require these huge amounts of dark matter to allow budding galaxies to stay together, but now there are observations that suggest otherwise.  It looks like we’ll have to adjust our ideas of dark matter’s role in the galaxy (not that this should surprise anyone).
For more, see Herschel finds less dark matter but more stars.

Dark Matter Detection Discussed
Earlier this month, there was a really excellent guest post at Cosmic Variance about the state of dark matter detection experiments by Neal Weiner (to complete the discussion of dark matter in the galaxy) so you should give that a read.
High Energy Physics and Particles:

“Symmetry Breaking” in Graphene?

San-Jose, P., González, J., & Guinea, F. (2011). Electron-Induced Rippling in Graphene Physical Review Letters, 106 (4) DOI: 10.1103/PhysRevLett.106.045502
So this was a hot topic this month that I’m just getting around to: graphene as an analogy for the Higgs field.  Now, as always with these analogy papers, I get a little nervous.  When there isn’t an explicit (AdS/CFT-esque) correspondence, it’s really very difficult (and a somewhat philosophical matter) to say what we are actually able to learn from analogies. In this case, the analogy comes from the fact that the “energy landscape” of graphene moving in 2-dimensions is similar to that of the Higgs field in 3-dimensions, in that they are both described by a similar Mexican hat potential.  Okay. There are other situations where we see Mexican hat potentials, like when rotating a bead on a circle, but that doesn’t mean that they would be at all useful in thinking about spontaneous symmetry breaking. Since I don’t really know anything relevant about graphene, quantum criticality, or… well, materials in general, I am completely unqualified to to judge this analogy, but it is still an analogy, not a correspondence.  Similar and the same are, importantly, and fundamentally different.
... Read more »

Joseph Silk. (2011) Feedback in Galaxy Formation. arXiv. arXiv: 1102.0283v1

Alexandre Amblard, & et al. (2011) Sub-millimetre galaxies reside in dark matter halos with masses greater than 3x10^11 solar masses. Nature. arXiv: 1101.1080v1

San-Jose, P., González, J., & Guinea, F. (2011) Electron-Induced Rippling in Graphene. Physical Review Letters, 106(4). DOI: 10.1103/PhysRevLett.106.045502  

Lloyd, S., Maccone, L., Garcia-Patron, R., Giovannetti, V., Shikano, Y., Pirandola, S., Rozema, L., Darabi, A., Soudagar, Y., Shalm, L.... (2011) Closed Timelike Curves via Postselection: Theory and Experimental Test of Consistency. Physical Review Letters, 106(4). DOI: 10.1103/PhysRevLett.106.040403  

Hohm, O., & Kwak, S. (2011) Frame-like geometry of double field theory. Journal of Physics A: Mathematical and Theoretical, 44(8), 85404. DOI: 10.1088/1751-8113/44/8/085404  

Carlo Rovelli. (2011) Lectures on loop gravity. arXiv. arXiv: 1102.3660v2

  • December 13, 2010
  • 11:14 AM
  • 902 views

This “Week” in the Universe: November 30th – December 13th

by S.C. Kavassalis in The Language of Bad Physics

Astrophysics and Gravitation:
The Milky Way Project
The Milky Way Project aims to sort and measure our galaxy, the Milky Way. Initially we’re asking you to help us find and draw bubbles in beautiful infrared data from the Spitzer Space Telescope.
Understanding the cold, dusty material that we see in these images, helps scientists to learn how stars form and how our galaxy changes and evolves with time.
The GalaxyZoo project expands! Help astronomers out when you’re feeling in the mood to procrastinate.

GREAT10 Image Analysis Competitions for Cosmological Lensing
GREAT10, a simulation challenge that aims to improve image analysis algorithms for cosmic gravitational lensing.
GREAT10 is a way for astronomers, astrophysicists, computer vision, and AI people to come together and find new ways of solving problems.  Contest details are online.
For more, see Computer Geeks: Compete to Help NASA Explain Dark Energy.
High Energy Physics and Particles:
2010 Ion Run Complete at CERN
From CERN Bulletin:
After a very fast switchover from protons to lead ions, the LHC has achieved performances that allowed the machine to exceed both peak and integrated luminosity by a factor of three. Thanks to this, experiments have been able to produce high-profile results on ion physics almost immediately, confirming that the LHC was able to keep its promises for ions as well as for protons.
Another milestone finished; it’s been a great year for the LHC.
For more, see CERN Bulletin.
General Relativity, Quantum Gravity, et al.:
GravityGeek for Christmas
GravityGeek is a cooperative project to help encourage interaction amongst physicists in gravitation/general relativity with journalists and the public.
GravityGeek, the beta collaboration/networking site for professionals in general relativity, quantum gravity, cosmology, etc., has recommendations for Christmas/other gift giving, in case you have a physicist to buy for (as well as non-technical recommendations for kids and those who just like good popular science literature).
For more, see The GravityGeek Mission.
Fun with 2D Blackholes
Abhay Ashtekar, Frans Pretorius, & Fethi M. Ramazanoğlu (2010). Surprises in the Evaporation of 2-Dimensional Black Holes arXiv arXiv: 1011.6442v1
The abstract:
Quantum evaporation of Callen-Giddings-Harvey-Strominger (CGHS) black holes is analyzed in the mean field approximation. The resulting semi-classical theory incorporates back reaction. Detailed analytical and numerical calculations show that, while some of the assumptions underlying the standard evaporation paradigm are borne out, several are not. Furthermore, if the black hole is initially macroscopic, the evaporation process exhibits remarkable universal properties. Although the literature on CGHS black holes is quite rich, these features had escaped previous analyses, in part because of lack of required numerical precision, and in part because certain properties and symmetries of the model were not recognized. Finally, our results provide support for the full quantum scenario recently developed by Ashtekar, Taveras and Varadarajan.
This is fairly nice for something so dense to read (it’s a lot crammed into four pages).  The key result: for 2D black holes, information in the matter profile on Ī⁻R will not all be recovered at Ī⁺R, in generality.  Slight twists on our understanding of 2D black holes might be suggestive of solutions in 4D.  Of course, the usual problems of discussing anything in 2D are still there, but still…
Cyclic Circles in the Sky? Probably Not
The big topic of the past few weeks has been Roger Penrose and V.G. Gurzadyan’s November paper, suggesting there was evidence, via circle matching in the CMB, of a cyclic cosmology.  There are so many papers being discussed right now, that this requires it’s own section.  Now, because Penrose being a co-author makes any paper big news, mainstream media was all over this “evidence for time before time” (and other completely offensive and nonsensical catchphrases).  What Gurzadyan and Penrose believed they had shown was that patterns in the CMB could not fit with standard inflationary cosmology and were strongly suggestive of a cyclic cosmology – ie. multiple “big bangs” (so our big bang wasn’t the first/didn’t start the cosmic clock, so to speak).  Now, many people who’ve looked for circles in the CMB (because it could be very suggestive of the topology/geometry/history of the universe) were sceptical of this, because, unfortunately, patterns in the CMB are a little like bible codes.  If you’re just looking for something, with a data set that big, you’re bound to find it and it doesn’t make it at all meaningful.  Doubters appeared quickly on the arXiv and in blogs, and Gurzadyan and Penrose quickly responded in kind (see NASA, this is how it’s supposed to work).  Below are the papers in the discussion as it stands, from November 16th to today:
The Original Paper
V. G. Gurzadyan, & R. Penrose (2010). Concentric circles in WMAP data may provide evidence of violent pre-Big-Bang activity arXiv arXiv: 1011.3706v1
Critique #1 by Wehus & Eriksen
I. K. Wehus, & H. K. Eriksen (2010). A search for concentric circles in the 7-year WMAP temperature sky maps arXiv arXiv: 1012.1268v1
Critique #2 by Moss, Scott & Ziblin
Adam Moss, Douglas Scott, & James P. Zibin (2010). No evidence for anomalously low variance circles on the sky ... Read more »

Abhay Ashtekar, Frans Pretorius, & Fethi M. Ramazanoğlu. (2010) Surprises in the Evaporation of 2-Dimensional Black Holes. arXiv. arXiv: 1011.6442v1

V. G. Gurzadyan, & R. Penrose. (2010) Concentric circles in WMAP data may provide evidence of violent pre-Big-Bang activity. arXiv. arXiv: 1011.3706v1

I. K. Wehus, & H. K. Eriksen. (2010) A search for concentric circles in the 7-year WMAP temperature sky maps. arXiv. arXiv: 1012.1268v1

Adam Moss, Douglas Scott, & James P. Zibin. (2010) No evidence for anomalously low variance circles on the sky. arXiv. arXiv: 1012.1305v1

V. G. Gurzadyan, & R. Penrose. (2010) More on the low variance circles in CMB sky. arXiv. arXiv: 1012.1486v1

  • September 15, 2010
  • 10:16 AM
  • 900 views

This Week in the Universe: September 9th – September 15th

by S.C. Kavassalis in The Language of Bad Physics

Astrophysics and Gravitation:
Astrophysics, by General Mills
Vella, D., & Mahadevan, L. (2005). The “Cheerios effect” American Journal of Physics, 73 (9) DOI: 10.1119/1.1898523
FOX News and a few other news agencies have discovered the Cheerios Effect this week (unfortunately, MSNBC beat them to this scope by about five years).  Back in 2005, Vella and Mehadevan described the “Cheerios Effect”, the tendency for small, wet, objects to attract each other.
From the abstract:
Objects that float at the interface between a liquid and a gas interact because of interfacial deformation and the effect of gravity.
Makes sense, but what does this have to do with astrophysics? Well, just like how the few remaining Cheerios left in the bowl have a tendency to group together in the milk, galaxies have a tendency to group together in space.  While the forces involved are quite different, the outcome is visually rather similar, and, astrophysics has a long history of using fluid models for approximations.  Is this big news? No, but it makes a very good classroom demonstration (as the authors originally wanted).
For more, see Cereal And Saturday Morning Physics.
PAMELA Results on the Cosmic-Ray Antiproton Flux
O. Adriani, & et al. (2010). PAMELA Results on the Cosmic-Ray Antiproton Flux from 60 MeV to 180 GeV in Kinetic Energy Phys. Rev. Lett., 105 (12), 1101-1106 : 10.1103/PhysRevLett.105.121101
The abstract:
The satellite-borne experiment PAMELA has been used to make a new measurement of the cosmic-ray antiproton flux and the antiproton-to-proton flux ratio which extends previously published measurements down to 60 MeV and up to 180 GeV in kinetic energy. During 850 days of data acquisition approximately 1500 antiprotons were observed. The measurements are consistent with purely secondary production of antiprotons in the Galaxy. More precise secondary production models are required for a complete interpretation of the results.
Earlier this year, PAMELA observed an usually large flux of positrons within the cosmic rays they were seeing from some unknown, beyond the atmosphere, source.  Naturally, like all unusual cosmic ray results, people thought “dark matter”.  Now, with more data, the PAMELA team has confirmed these observations, but still can’t suggest a cause.  Observation supports some “secondary production” mechanism for their creation, ie. the positrons being produced by some annihilation interaction with some unknown particles, but it’s still quite open what that might be.
For more, see Uncertain Sources.
Hungry Hungry Stars
Credit: X-ray (NASA/CXC/RIT/J.Kastner et al), Optical (UCO/Lick/STScI/M.Perrin et al); Illustration: NASA/CXC/M.Weiss
NASA’s Chandra X-ray Observatory has recently seen evidence of star cannibalism.  It appears that star BP Piscium (BP Psc – a red giant phase star once probably the size of our Sun) may have absorbed a companion star in the past (or perhaps a large planet).
David Rodriguez from UCLA:
BP Psc shows us that stars like our Sun may live quietly for billions of years, but when they go, they just might take a star or planet or two with them.
For more, see Chandra Finds Evidence for Stellar Cannibalism.
Dark Matter in the Sun (again?)
Lopes, I., & Silk, J. (2010). Neutrino Spectroscopy Can Probe the Dark Matter Content in the Sun Science DOI: 10.1126/science.1196564
From the abstract:
After being gravitationally captured, low mass cold dark matter particles (mass range 5 to ~50 x 109 electron volts) are thought to drift to the center of the Sun and affect its internal structure. Solar neutrinos provide a way to probe the physical processes occurring in the Sun’s core. Solar neutrino spectroscopy, in particular, is expected to measure the neutrino fluxes produced in nuclear reactions in the Sun. Here, we show how the presence of dark matter particles inside the Sun will produce unique neutrino flux distributions…
Ah, more speculation that dark matter could be found inside the sun.  Is this based on observation? Well no, but we still can’t quite explain the expected composition of the sun with its mass and spectrum, so there is room for dark matter.  Is it science? Not yet.
For more, see Searching the Sun for dark matter.
General Relativity, Quantum Gravity, et al.:
Fun with Five-Dimensional Black Strings
Lehner, L., & Pretorius, F. (2010). Black Strings, Low Viscosity Fluids, and Violation of Cosmic Censorship Physical Review Letters, 105 (10) DOI: 10.1103/PhysRevLett.105.101102
The Abstract:
We describe the behavior of 5-dimensional black strings, subject to the Gregory-Laflamme instability. Beyond the linear level, the evolving strings exhibit a rich dynamics, where at intermediate stages the horizon can be described as a sequence of 3-dimensional spherical black holes joined by black string segments. These segments are themselves subject to a Gregory-Laflamme instability, resulting in a ... Read more »

Vella, D., & Mahadevan, L. (2005) The “Cheerios effect”. American Journal of Physics, 73(9), 817. DOI: 10.1119/1.1898523  

O. Adriani, & et al. (2010) PAMELA Results on the Cosmic-Ray Antiproton Flux from 60 MeV to 180 GeV in Kinetic Energy. Phys. Rev. Lett., 105(12), 1101-1106. info:/10.1103/PhysRevLett.105.121101

Lopes, I., & Silk, J. (2010) Neutrino Spectroscopy Can Probe the Dark Matter Content in the Sun. Science. DOI: 10.1126/science.1196564  

Lehner, L., & Pretorius, F. (2010) Black Strings, Low Viscosity Fluids, and Violation of Cosmic Censorship. Physical Review Letters, 105(10). DOI: 10.1103/PhysRevLett.105.101102  

  • August 31, 2010
  • 09:00 PM
  • 859 views

The Bad Language of Physics

by S.C. Kavassalis in The Language of Bad Physics

One of the things I sometimes find myself writing about is the “bad” language used by physicists.  Sometimes we say Riemannian when we really should say psuedo-Riemannian, sometimes we call something a metric when it really is a line element – the kind of nitpicky pet-peeves that practically everyone has about literature in their field.  Today, I’m going to be talking about the bad language in physics in a totally different context however.
Teepee Lattices, Future-Pointing Wigwams and Polish Numbers
My secret love for discrete spacetimes comes from a beautiful little sub-field of general relativity (that is experiencing a little bit of a revival right now thanks to loop quantum gravity) called Regge calculus. Regge calculus was a method suggested by John Wheeler and his student, Tullio Regge, in the early 1960s[1], to find approximate solutions to the Einstein Equations. Their basic idea was just to simplify spacetime and see what happened.  Instead of having one complicated, curved, four-dimensional Lorentzian manifold to work in, we would piece our spacetime together out of four-dimensional simplices (the higher order word for triangle), that would have, nice, simple, flat interiors, so the entire picture would show curvature, but each individual section would be easy to describe and work in.
Consider this 2D example
This two-dimensional “simplexification” might be able to give you a better idea of the process. Here, we have triangulated a small “curved” surface.  The interior of each triangle (a 2-simplex) is a flat, Minkowskian space, and the curvature is manifest at the vertices (0-simplices) where the triangles meet.  When we scale this concept up to four dimensions, we end up with flat, Minkowskian, 4-simplices, and then our curvature is contained at the 2-simplices (curvature is now manifest on triangles, not points) where the 4-simplices meet¹.
So that is the basic idea behind Regge calculus – we break up spacetime into simple, triangular, chunks.  The implementation of it is where the real difficulties arises.
Evolution
When we think of our favourite formulation of general relativity in the continuum limit, most of us probably think of the ADM formalism (No? I bet you’ve never even turned your alarm clock off in your sleep thinking that you still needed the lapse and shift to know what time it really was).
Creating a 4-geometry by "sandwiching" two 3-geometries (this is a "sandwich" of infinitesimal thickness): The 4-metric (ie. geometry) of the full 4D spacetime (which is what GR is all about) depends on the lapse and shift of the connectors ("sandwich filling") between the two 3-geometries as well as the 3-metric (the geometry of the "bread"). N is the lapse function (to get the proper time between the upper and lower surfaces you need Ndt) and Nⁱ is the shift function.
The ADM formalism says that we should foliate (slice) our continuous spacetime into three-dimensional spacelike surfaces that we can label by their time coordinates and then define our dynamics from there. It is an elegant, simple and well studied idea that is exceptionally powerful, so logically, it seems like a good set of concepts to work into Regge calculus.
Now, the original idea of Regge calculus was to model the four-dimensional Lorentzian manifold of spacetime by simplices (the Regge analogue of the tangent space), that have flat, Minkowskian interiors (although in his original paper [1] he actually used simplices with flat, Euclidean interiors, which effectively removed the ‘physics’ from the problem), but this didn’t leave much room for describing dynamics. To make Regge calculus more like our beloved ADM formalism, we approximate our differential three-manifolds² (our spacelike slices) by a collection of simplices, which allows us to preserve many important topological properties, while giving us room to describe dynamics (like the evolution of the universe, for example).
Simple Regge Evolution: (a) base triangulation (b) each vertex evolved (c) all connections to rightmost evolved vertex made.
So, the basic idea of evolution in Regge calculus is to take each vertex at a time t and “evolve” it up to some time t + dt (the lines connecting upper and lower vertices are in spirit with our connectors from the ADM foliation).  Since we also want to maintain some sense of reasonableness in our model (ie. that spacetime is locally path-connected, and is thus also connected), we also connect each initial vertex to each evolved vertex, so, for a single 2-simplex, we get:
2-Simplex Evolved: A lattice in 2 + 1 dimensions.
It’s a pretty simple idea, but, if you made it through all of the above, you probably found yourself asking, “But how do we actually know how to evolve a vertex? How do we know how long/at what angle to make all of those connections?”.  That’s a very good question, and one that doesn’t have a definite answer at this point (despite what certain individuals that have certain well known Regge evolution schemes named after them might think).  There is a sizable body of work dedicated to figuring out how to make those connections as physical as possible.

One such example came from Mark Galassi, in 1992, in his PhD dissertation on this very topic in which we were introduced to the concept of a teepee lattice [2].
Teepee (public domain image from Wikipedia)
From Collins English Dictionary:
teepee, noun: a cone-shaped tent of animal skins used by certain North American Indians [A]
It’s pretty obvious where this is going…
From Galassi's "Lattice Geometrodynamics"
The resemblance is uncanny(ish).
What’s nice about Galassi’s “teepees” is that they make the connection to ADM’s lapse and shift more obvious (if you’re familiar with both Regge calculus and the ADM formalism, that is) [3].  Other than that, it’s a rather funny name.  At least in Canada, gratuitous use of the word “teepee” makes a lot of people cringe.  In many circles, “teepee” is considered to be politically incorrect, because it has been so overused as part of stereotyping the Native “Indians”.  Political correctness be damned, says the physicist, it’s a fairly illustrative name for what’s going on in Regge evolution.  Is it offensive to some? Maybe.
Interestingly, this Native American naming concept didn’t come from Galassi, but came from Kheyfets et al. a few years earlier during the “Null Strut calculus” craze, with the introduction of spacetime wigwams [4].  Null Strut calculus is a variant of Regge calculus that insists that the connection between a &... Read more »

Regge, T. (1961) General relativity without coordinates. Il Nuovo Cimento, 19(3), 558-571. DOI: 10.1007/BF02733251  

Galassi, M. (1993) Lapse and shift in Regge calculus. Physical Review D, 47(8), 3254-3264. DOI: 10.1103/PhysRevD.47.3254  

Kheyfets A, LaFave NJ, & Miller WA. (1990) Null-strut calculus. II. Dynamics. Physical review D: Particles and fields, 41(12), 3637-3651. PMID: 10012308  

ALPER ÜNGÖR, & ALLA SHEFFER. (2002) PITCHING TENTS IN SPACE-TIME: MESH GENERATION FOR DISCONTINUOUS GALERKIN METHOD. International Journal of Foundations of Computer Science , 13(2). info:/10.1142/S0129054102001059

  • January 25, 2011
  • 04:38 PM
  • 821 views

This Week in the Universe: January 18th – January 24th

by S.C. Kavassalis in The Language of Bad Physics

Phenomenally beautiful math was the main highlight of this week, I’d say, although none of it for the very faint of heart.
The CMS on SUSY, Bill Unruh on simulated Hawking radiation, Ed Witten on knots, and Schenkel and Van Oystaeyen on noncommutative space(times):

High Energy Physics and Particles:

The LHC Doesn’t Need Data-Collecting Mode To Have Fun
CMS Collaboration (2011). Search for Supersymmetry in pp Collisions at 7 TeV in Events with Jets and Missing Transverse Energy arXiv arXiv: 1101.1628v1
The CMS Collaboration released results this month ruling out supersymmetric particles with masses of less than ~ 0.5 TeV/c2.  This is just one of a series of ongoing SUSY related papers analyzing last years data and spitting out constraints on models (which is hugely important).  We’ll be seeing results papers for years to come, but it’s nice to see evidence of the LHC being exactly what we all hoped it would be already: the thing that tells us if we’re likely on the right track or not.
For more, see Reality check at the LHC.
General Relativity, Quantum Gravity, et al.:

Measurement of Stimulated Hawking Emission
Silke Weinfurtner, Edmund W. Tedford, Matthew C. J. Penrice, William G. Unruh, & Gregory A. Lawrence (2010). Measurement of stimulated Hawking emission in an analogue system Phys. Rev. Lett., 106 (2), 1302-1306 arXiv: 1008.1911v2
The abstract:
Hawking argued that black holes emit thermal radiation via a quantum spontaneous emission. To address this issue experimentally, we utilize the analogy between the propagation of fields around black holes and surface waves on moving water. By placing a streamlined obstacle into an open channel flow we create a region of high velocity over the obstacle that can include surface wave horizons. Long waves propagating upstream towards this region are blocked and converted into short (deep-water) waves. This is the analogue of the stimulated emission by a white hole (the time inverse of a black hole), and our measurements of the amplitudes of the converted waves demonstrate the thermal nature of the conversion process for this system. Given the close relationship between stimulated and spontaneous emission, our findings attest to the generality of the Hawking process.
Analogues often make me a little uncomfortable in physics, for what are probably obvious reasons, but Bill Unruh has had a lot of success and acceptance with his analogue black hole/white hole models in the past.  The line between similar and the same, and if it is actually telling us anything to observe properties in these analogue systems (which have some major fundamental differences) always gets to me in these matters, so I’m going to have to come back to this one to give further comments.
For more, see Wave-Generated ‘White Hole’ Boosts Hawking Radiation Theory: UBC Research.

Ed Witten on Khovanov Homology of Knots.
Edward Witten (2011). Fivebranes and Knots arXiv arXiv: 1101.3216v1
The abstract:
We develop an approach to Khovanov homology of knots via gauge theory (previous physics-based approches involved other descriptions of the relevant spaces of BPS states). The starting point is a system of D3-branes ending on an NS5-brane with a nonzero theta-angle. On the one hand, this system can be related to a Chern-Simons gauge theory on the boundary of the D3-brane worldvolume; on the other hand, it can be studied by standard techniques of S-duality and T-duality. Combining the two approaches leads to a new and manifestly invariant description of the Jones polynomial of knots, and its generalizations, and to a manifestly invariant description of Khovanov homology, in terms of certain elliptic partial differential equations in four and five dimensions.
So Ed Witten is one of those few authors whose work I can feel safe about getting excited over before I’ve read it, and at 146 pages, well, it’s unlikely I’ll ever make it through all of this (although its length is only due to the fact that it very thorough, and thus imaginably very useful).  I’m going to defer to the University of Toronto’s Daniel Moskovich from Low Dimensional Topology (which I can’t recommend enough) on this one, as he wrote:... Read more »

CMS Collaboration. (2011) Search for Supersymmetry in pp Collisions at 7 TeV in Events with Jets and Missing Transverse Energy. arXiv. arXiv: 1101.1628v1

Silke Weinfurtner, Edmund W. Tedford, Matthew C. J. Penrice, William G. Unruh, & Gregory A. Lawrence. (2010) Measurement of stimulated Hawking emission in an analogue system. Phys. Rev. Lett., 106(2), 1302-1306. arXiv: 1008.1911v2

Edward Witten. (2011) Fivebranes and Knots. arXiv. arXiv: 1101.3216v1

Alexander Schenkel. (2011) Quantum Field Theory on Curved Noncommutative Spacetimes. arXiv. arXiv: 1101.3492v2

  • August 2, 2010
  • 01:15 PM
  • 818 views

This Week in the Universe: July 27th – August 2nd

by S.C. Kavassalis in The Language of Bad Physics

What have people been talking about this week in high energy physics, astrophysics, gravitation, general relativity and quantum gravity?... Read more »

A. Kappes for the IceCube Collaboration. (2010) IceCube: Neutrino Messages from GRBs. Proceedings: Deciphering the Ancient Universe with Gamma-Ray Bursts. arXiv: 1007.4629v1

Adam Moss, James P. Zibin, & Douglas Scott. (2010) Precision Cosmology Defeats Void Models for Acceleration. arXiv. arXiv: 1007.3725v1

Hiyama, E., Kamimura, M., Yamamoto, Y., & Motoba, T. (2010) Five-Body Cluster Structure of the Double-Λ Hypernucleus _{ΛΛ}^{11}Be. Physical Review Letters, 104(21). DOI: 10.1103/PhysRevLett.104.212502  

Peter Sorensen. (2010) A coherent understanding of low-energy nuclear recoils in liquid xenon. arXiv. arXiv: 1007.3549v2

Stephen D. H. Hsu. (2010) White holes and eternal black holes. arXiv. arXiv: 1007.2934v1

  • December 26, 2010
  • 09:25 PM
  • 778 views

This Week in the Universe: December 20th – December 27th

by S.C. Kavassalis in The Language of Bad Physics

Since I’m in the Rockies soaking up my last few days of vacation, I haven’t actually looked at much this week, but there were two papers I thought were worth noting.
Astrophysics and Gravitation:
Reconstructing Histories with Good Statistics
Tracy Holsclaw, Ujjaini Alam, Bruno Sanso, Herbert Lee, Katrin Heitmann, Salman Habib, & David Higdon (2010). Nonparametric Dark Energy Reconstruction from Supernova Data Phys. Rev. Lett. arXiv: 1011.3079v1
The abstract:
Understanding the origin of the accelerated expansion of the Universe poses one of the greatest challenges in physics today. Lacking a compelling fundamental theory to test, observational efforts are targeted at a better characterization of the underlying cause. If a new form of mass-energy, dark energy, is driving the acceleration, the redshift evolution of the equation of state parameter w(z) will hold essential clues as to its origin. To best exploit data from observations it is necessary to develop a robust and accurate reconstruction approach, with controlled errors, for w(z). We introduce a new, nonparametric method for solving the associated statistical inverse problem based on Gaussian process modeling and Markov chain Monte Carlo sampling. Applying this method to recent supernova measurements, we reconstruct the continuous history of w out to redshift z=1.5.
As the paper says, “In order to extract useful information from cosmological data, a reliable and robust reconstruction method for w(z) [the equation of state parameter] is crucial”, and that’s what this paper aims to provide.  It’s not the most exciting thing you’ll ever read (although it is short), but without work along these lines, much of cosmology and astrophysics is actually pretty meaningless, so it’s certainly worth remembering that.
For more, see Statistical modeling could help us understand cosmic acceleration.
General Relativity, Quantum Gravity, et al.:
Brane Holes
Valeri P. Frolov, & Shinji Mukohyama (2010). Brane Holes arXiv arXiv: 1012.4541v1
The abstract:
The aim of this paper is to demonstrate that in models with large extra dimensions under special conditions one can extract information from the interior of 4D black holes. For this purpose we study an induced geometry on a test brane in the background of a higher dimensional static black string or a black brane. We show that at the intersection surface of the test brane and the bulk black string/brane the induced metric has an event horizon, so that the test brane contains a black hole. We call it a brane hole. … We discuss thermodynamic properties of brane holes and interesting questions which arise when such an extra dimensional channel for the information mining exists.
Who doesn’t love higher dimensional solutions for black holes?  Honestly, I haven’t had time to give this a thorough read yet but it looks rather promising.
For more, see Cosmologists Discover How Black Holes Can Leak.
... Read more »

Tracy Holsclaw, Ujjaini Alam, Bruno Sanso, Herbert Lee, Katrin Heitmann, Salman Habib, & David Higdon. (2010) Nonparametric Dark Energy Reconstruction from Supernova Data. Phys. Rev. Lett. arXiv: 1011.3079v1

Valeri P. Frolov, & Shinji Mukohyama. (2010) Brane Holes. arXiv. arXiv: 1012.4541v1

  • August 24, 2010
  • 07:00 PM
  • 739 views

This Week in the Universe: August 17th – August 23rd

by S.C. Kavassalis in The Language of Bad Physics

What have people been talking about this week in high energy physics, astrophysics, gravitation, general relativity and quantum gravity?... Read more »

Lo Curto, G., Mayor, M., Benz, W., Bouchy, F., Lovis, C., Moutou, C., Naef, D., Pepe, F., Queloz, D., Santos, N.... (2010) The HARPS search for southern extra-solar planets XXVII. Astronomy and Astrophysics. info:other/10.1051/0004-6361/200913523

D. J. Champion, G. B. Hobbs, R. N. Manchester, R. T. Edwards, D. C. Backer, M. Bailes, N. D. R. Bhat, S. Burke-Spolaor, W. Coles, P. B. Demorest.... (2010) Measuring the mass of solar system planets using pulsar timing. Astrophysical Journal. arXiv: 1008.3607v1

Berné O, Marcelino N, & Cernicharo J. (2010) Waves on the surface of the Orion molecular cloud. Nature, 466(7309), 947-9. PMID: 20725034  

B. W. Ritchie, J. S. Clark, I. Negueruela, & N. Langer. (2010) A VLT/FLAMES survey for massive binaries in Westerlund 1: II. Dynamical constraints on magnetar progenitor masses from the eclipsing binary W13. Astronomy . arXiv: 1008.2840v1

Ephraim Fischbach,, Peter A. Sturrock,, Jere H. Jenkins,, Daniel Javorsek II,, John B. Buncher,, & John T. Gruenwald. (2010) Evidence for Solar Influences on Nuclear Decay Rates . Fifth Meeting on CPT and Lorentz Symmetry. info:/1007.3318

P. E. Koehler, F. Bečvář, M. Krtička, J. A. Harvey, & K. H. Guber. (2010) Anomalous fluctuations of s-wave reduced neutron widths of $^{192,194}$Pt resonances. Phys. Rev. Lett. , 105(7). arXiv: 1007.3675v1

Palenzuela, C., Lehner, L., & Liebling, S. (2010) Dual Jets from Binary Black Holes. Science, 329(5994), 927-930. DOI: 10.1126/science.1191766  

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