All posts; Tags Include "Cosmology"
- August 3, 2010
- 05:28 PM
- 142 views
New limit on neutrino mass… from cosmology, not particle physics
by Kelly Oakes in Basic Space
Physicists at University College London have found a new upper limit on the mass of a neutrino – one of the tightest constraints yet from either particle physics or cosmology. Neutrinos are elementary particles that travel close to the speed of light, but are very difficult to detect because they are not electrically charged. In [...]... Read more »
Thomas, S., Abdalla, F., & Lahav, O. (2010) Upper Bound of 0.28 eV on Neutrino Masses from the Largest Photometric Redshift Survey. Physical Review Letters, 105(3). DOI: 10.1103/PhysRevLett.105.031301
- August 2, 2010
- 01:15 PM
- 86 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
- August 1, 2010
- 03:38 AM
- 98 views
alt cosmology paper reinvents the big crunch
by Greg Fish in weird things
Extending my previous note on the state of many papers submitted to arXiv today, the view hungry editors at the Technology Review blog decided to do a very, very generous write-up for a paper that predicts a universe with no Big Bang and while explaining a few odd observations related to certain supernovae, forgets to [...]... Read more »
Wun-Yi Shu. (2010) Cosmological Models with No Big Bang. n/a. arXiv: 1007.1750v1
- July 29, 2010
- 03:51 PM
- 120 views
Hubble Bubble
by The Astronomist in The Astronomist.
The Copernican principle holds that humans are not privileged observers of the Universe. Copernicus stated that the Earth is not at the center of the solar system or at any particularly special position in the heavens. Modern cosmology has extended this idea to reason that the earth does not occupy any unique position in the Universe. Modern philosophy of science pushes the principle even further to conclude that every observer (even if they be they little green men) should reason as if they wer........ Read more »
Adam Moss, James P. Zibin, & Douglas Scott. (2010) Precision Cosmology Defeats Void Models for Acceleration. arXiv preprint. arXiv: 1007.3725v1
Conley, A., Carlberg, R., Guy, J., Howell, D., Jha, S., Riess, A., & Sullivan, M. (2007) Is There Evidence for a Hubble Bubble? The Nature of Type Ia Supernova Colors and Dust in External Galaxies. The Astrophysical Journal, 664(1). DOI: 10.1086/520625
- July 19, 2010
- 12:19 PM
- 112 views
This Week in the Universe: July 13th – July 19th
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 »
F. Courbin, M. Tewes, S. G. Djorgovski, D. Sluse, A. Mahabal, F. Rerat, & G. Meylan. (2010) First case of strong gravitational lensing by a QSO : SDSS J0013 1523 at z . Astronomy . arXiv: 1002.4991v2
Butt, Y. (2009) Beyond the myth of the supernova-remnant origin of cosmic rays. Nature, 460(7256), 701-704. DOI: 10.1038/nature08127
Daniel T. Cumberbatch, Joyce. A. Guzik, Joseph Silk, L. Scott Watson, & Stephen M. West. (2010) Light WIMPs in the Sun: Constraints from Helioseismology. arXiv. arXiv: 1005.5102v1
Miller, J. (2010) Laboratory experiment shows that noise can be lessened for LISA. Physics Today, 63(7), 14. DOI: 10.1063/1.3463616
Eugenio Bianchi, & Carlo Rovelli. (2010) Why all these prejudices against a constant?. arXiv. arXiv: 1002.3966v3
Attila Meszaros, Lajos G. Balazs, Zsolt Bagoly, & Peter Veres. (2010) Impact on cosmology of the celestial anisotropy of the short gamma-ray bursts. Baltic Astronomy, Vol.18, 293-296 (2009). arXiv: 1005.1558v1
Chris Clarkson, & Roy Maartens. (2010) Inhomogeneity and the foundations of concordance cosmology. Class. Quantum Grav. 27 124008 (2010). arXiv: 1005.2165v2
Mosconi, M., Fujii, K., Mengoni, A., Domingo-Pardo, C., Käppeler, F., Abbondanno, U., Aerts, G., Álvarez-Pol, H., Alvarez-Velarde, F., Andriamonje, S.... (2010) Neutron physics of the Re/Os clock. I. Measurement of the (n,γ) cross sections of ^{186,187,188}Os at the CERN n_TOF facility. Physical Review C, 82(1). DOI: 10.1103/PhysRevC.82.015802
Nikodem J. Poplawski. (2010) Cosmology with torsion - an alternative to cosmic inflation. arXiv. arXiv: 1007.0587v1
The CDF Collaboration, & T. Aaltonen. (2009) Measurement of $d\sigma/dy$ of Drell-Yan $e^ e^-$ pairs in the $Z$ Mass Region from $p\bar{p}$ Collisions at $\sqrt{s}. Physics Letters. arXiv: 0908.3914v4
Petr Horava, & Charles M. Melby-Thompson. (2010) General Covariance in Quantum Gravity at a Lifshitz Point. arXiv. arXiv: 1007.2410v1
Samuel E. Gralla, & Robert M. Wald. (2009) Derivation of Gravitational Self-Force. arXiv. arXiv: 0907.0414v1
J. Ambjorn, A. Goerlich, J. Jurkiewicz, & R. Loll. (2010) CDT---an Entropic Theory of Quantum Gravity. arXiv. arXiv: 1007.2560v1
- May 12, 2010
- 03:09 PM
- 246 views
Inconstant Constants: "Probing fundamental constant evolution with redshifted conjugate-satellite OH lines"
by Chad Orzel in Uncertain Principles
Via Jennifer Ouellette on Twitter, I ran across a Discovery News story touting a recent arxiv preprint claiming to see variation in the fine-structure constant. It's a basically OK story, but garbles a few details, so I thought it would be worth giving it the ResearchBlogging treatment, in the now-traditional Q&A format.
What did they do? The paper looks at some spectral lines in radio emission from a moderately distant galaxy with the poetic name "PKS1413+135." These lines are produced by ........ Read more »
Nissim Kanekar, Jayaram N. Chengalur, & Tapasi Ghosh. (2010) Probing fundamental constant evolution with redshifted conjugate-satellite OH lines. Astrophysical Journal Letters. arXiv: 1004.5383v1
- May 5, 2010
- 12:51 AM
- 258 views
Dark Matter Confronts Observations
by The Astronomist in The Astronomist.
Dark matter is like the Rome of astronomy, all observations lead to dark matter. The problem is that physicists and astronomers, don't know what it actually is. The observations which support dark matter come from many different independent observations, so it is not just some observational error. The observations which corroborate the dark matter paradigm make for a fantastic discussion, but for right now I would like to focus on explanations for what dark matter may be. Specifically, what kin........ Read more »
Abdo, A., Ackermann, M., Ajello, M., Atwood, W., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Baughman, B., Bechtol, K.... (2010) Spectrum of the Isotropic Diffuse Gamma-Ray Emission Derived from First-Year Fermi Large Area Telescope Data. Physical Review Letters, 104(10). DOI: 10.1103/PhysRevLett.104.101101
Nima Arkani-Hamed, Douglas P. Finkbeiner, Tracy R. Slatyer, & Neal Weiner. (2008) A Theory of Dark Matter. Phys.Rev.D79:015014,2009. arXiv: 0810.0713v3
Feng, J., Kaplinghat, M., & Yu, H. (2010) Halo-Shape and Relic-Density Exclusions of Sommerfeld-Enhanced Dark Matter Explanations of Cosmic Ray Excesses. Physical Review Letters, 104(15). DOI: 10.1103/PhysRevLett.104.151301
- April 11, 2010
- 04:17 PM
- 301 views
Spreading Galaxies Gospel on Facebook
by sarah in SarahAskew
Paolo Salucci has a bone to pick with the community. The Trieste-based astronomer is fed up with his colleagues’ misconceptions about galaxy rotation curves and has decided to Do Something About It. In his short paper posted to astro-ph last Friday, he describes the experiment he’s set up to convince the world that galaxy rotation [...]... Read more »
Paolo Salucci. (2010) Can Social Networks help the progress of Astrophysics and Cosmology? An experiment in the field of Galaxy Kinematics. Arxiv. arXiv: 1004.1190v1
- March 12, 2010
- 03:01 AM
- 255 views
Galaxies are slowly running out of gas
by Charles Daney in Science and Reason
Galaxies are made of stars, and stars are made of... gas. So a large part of understanding how galaxies evolve and grow is understanding how much "gas" (literally, not "gasoline") is present in galaxies – but has not yet been incorporated in stars – at different periods in the history of the universe.What periods of the universe are most interesting in this regard? The answer is: periods somewhat less than the first half of the universe's existence since the time of the big bang, rou........ Read more »
Tacconi, L., Genzel, R., Neri, R., Cox, P., Cooper, M., Shapiro, K., Bolatto, A., Bouché, N., Bournaud, F., Burkert, A.... (2010) High molecular gas fractions in normal massive star-forming galaxies in the young Universe. Nature, 463(7282), 781-784. DOI: 10.1038/nature08773
- February 24, 2010
- 03:06 AM
- 222 views
Where have all the protons gone?
by Charles Daney in Science and Reason
Astronomers have long known that there is a rather close relationship between the intrinsic luminosity of a spiral galaxy and the rotational velocity of stars (around the galactic center) in the outer portions of the galaxy. This relationship even has a name: the Tully-Fisher relation.It has also been known that small, nearby dwarf galaxies, which are irregular in shape, are not nearly as bright as they "should" be, according to the Tully-Fisher relation, given the measured average velocities of........ Read more »
McGaugh, S., Schombert, J., de Blok, W., & Zagursky, M. (2010) THE BARYON CONTENT OF COSMIC STRUCTURES. The Astrophysical Journal, 708(1). DOI: 10.1088/2041-8205/708/1/L14
- February 22, 2010
- 02:15 AM
- 240 views
Dwarf galaxies start making sense
by Charles Daney in Science and Reason
Cosmology has, for a decade, had its "standard model", which largely explains most of the cosmological phenomena that astronomers are able to observe. Except for a relatively small number of things that don't seem to make sense in the model. Prominent among the latter are dwarf galaxies – by one definition, galaxies having less than 10% of the total mass of the Milky Way.The standard model of cosmology is known officially as the Λ-cold-dark-matter model – ΛCDM. (This th........ Read more »
Governato, F., Brook, C., Mayer, L., Brooks, A., Rhee, G., Wadsley, J., Jonsson, P., Willman, B., Stinson, G., Quinn, T.... (2010) Bulgeless dwarf galaxies and dark matter cores from supernova-driven outflows. Nature, 463(7278), 203-206. DOI: 10.1038/nature08640
- February 19, 2010
- 03:47 AM
- 217 views
An Upper Limit On Not Knowing What the F*** They're Doing
by The Astronomist in The Astronomist.
First, I should say that the Supernova Cosmology Group and others using Type Ia supernova as standard candles are very precise in their work and I don't seriously doubt their results as they have been very consistent with other observations. There is though the one dark shadow looming over all their results and that is systematic error. Cosmologists use Type Ia supernova as a lighthouse in the dark because we can assume that all lighthouses have the same intrinsic luminosity and therefore any di........ Read more »
Marat Gilfanov, & Akos Bogdan. (2010) An upper limit on the contribution of accreting white dwarfs to the type Ia supernova rate. Nature, 18 February 2010, Vol.463, p.924. arXiv: 1002.3359v1
- February 19, 2010
- 12:05 AM
- 259 views
An Upper Limit On Not Knowing What the F*** They're Doing
by The Astronomist in The Astronomist.
First, I should say that the Supernova Cosmology Group and others using Type Ia supernova as standard candles are very precise in their work and I don't seriously doubt their results as they have been very consistent with other observations. There is though the one dark shadow looming over all their results and that is systematic error.... Read more »
Marat Gilfanov, & Akos Bogdan. (2010) An upper limit on the contribution of accreting white dwarfs to the type Ia supernova rate. Nature, 18 February 2010, Vol.463, p.924. arXiv: 1002.3359v1
- February 15, 2010
- 10:46 PM
- 176 views
Far out!
by Charles Daney in Science and Reason
If you're interested in something out of the ordinary, astronomically speaking, the best place to look for the exotic may be as far away (in both space and time) as possible.Perhaps that's why I like to consider really far out stuff, like the most distant gamma-ray burst seen yet. Or maybe I just like to get away from the depressing chaos and confusion of "modern" life.In any case, there's always something new, just beyond the farthest thing we've seen yet. That far-out gamma-ray burst (GRB 0904........ Read more »
R. J. Bouwens, G. D. Illingworth, I. Labbe, P. A. Oesch, M. Carollo, M. Trenti, P. G. van Dokkum, M. Franx, M. Stiavelli, V. Gonzalez.... (2009) Constraints on the First Galaxies: z~10 Galaxy Candidates from HST WFC3/IR. Nature. arXiv: 0912.4263v2
- February 10, 2010
- 11:22 PM
- 368 views
The Cosmos isn't strange, people are strange
by The Astronomist in The Astronomist.
The cosmos isn't strange, people are strange. The universe on the largest of scales is actually simple compared to the complexities of the human mind or even the weather. In a statistical sense all current observations indicate that universe is homogeneous and isotropic everywhere. The best evidence for this statement is the cosmic microwave background (CMB) radiation which is light from the big bang that has traveled unimpeded through the universe since recombination. A simp........ Read more »
C. L. Bennett, R. S. Hill, G. Hinshaw, D. Larson, K. M. Smith, J. Dunkley, B. Gold, M. Halpern, N. Jarosik, A. Kogut.... (2010) Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Are There Cosmic Microwave Background Anomalies?. ApJ. arXiv: 1001.4758v1
- February 10, 2010
- 03:17 PM
- 234 views
Expanding Universe
by Brian Koberlein in Upon Reflection
Figure 1: Two models of Newton's universe. Newtonian gravity predicts that stars were packed together tightly in the beginning, and expanded out into space. Over time, the stars either would collapse back together or expand forever. (Source: John D. Norton)...... Read more »
Hubble, E. (1929) A Relation between Distance and Radial Velocity among Extra-Galactic Nebulae. Proceedings of the National Academy of Sciences, 15(3), 168-173. DOI: 10.1073/pnas.15.3.168
- February 8, 2010
- 02:42 AM
- 283 views
The Cosmological Constant and the Dark Sector
by The Astronomist in The Astronomist.
What is the phenomenology of the dark sector? That is my question. The dark sector refers to dark energy and dark matter, which are two distinct phenomena which seem to have no direct connection other than in name. In this post I am going to talk about the cosmological constant, dark energy, and look at some landmark literature on the subject. I am going to show the origin of the 10120 order of magnitude error that results from the quantum field theory prediction and cosmological observation. I ........ Read more »
Carroll, Sean M., Press, William H., & Turner, Edwin L. (1992) The cosmological constant. ARA, 499-542. info:/
Will J. Percival, Beth A. Reid, Daniel J. Eisenstein, Neta A. Bahcall, Tamas Budavari, Joshua A. Frieman, Masataka Fukugita, James E. Gunn, Zeljko Ivezic, Gillian R. Knapp.... (2009) Baryon Acoustic Oscillations in the Sloan Digital Sky Survey Data Release 7 Galaxy Sample. MNRAS. arXiv: 0907.1660v3
- January 29, 2010
- 04:45 AM
- 356 views
The Entropy of the Universe
by Alexander in The Astronomist.
First, what is entropy? The entropy of a system can be defined as proportional to (the natural log of) the number of microstates corresponding to the observed system macrostate. In this post I discuss a paper for anyone was wondering what the entropy of the observable Universe is.... Read more »
Chas A. Egan, & Charles H. Lineweaver. (2010) A Larger Estimate of the Entropy of the Universe. ApJ. arXiv: 0909.3983v3
- January 19, 2010
- 11:01 AM
- 254 views
Dark Materials
by Brian Koberlein in Upon Reflection
Figure 1: A plot of the speed of stars in the Milky Way vs their distance from the galactic center. The top line represents the actual speed distribution of stars, while the bottom line represents what the motion should be...... Read more »
Law, D., Majewski, S., & Johnston, K. (2009) EVIDENCE FOR A TRIAXIAL MILKY WAY DARK MATTER HALO FROM THE SAGITTARIUS STELLAR TIDAL STREAM. The Astrophysical Journal, 703(1). DOI: 10.1088/0004-637X/703/1/L67
- December 14, 2009
- 11:41 AM
- 290 views
Beyond the Farthest Star
by Brian Koberlein in Upon Reflection
Figure 1: The Orion Constellation. (Source: APoD) When you look up into the night sky, you are seeing into the past. Cosmic distances are so vast that it takes time for light to travel them. Light from the closest star...... Read more »
Zhang, B. (2009) Astrophysics: Most distant cosmic blast seen. Nature, 461(7268), 1221-1223. DOI: 10.1038/4611221a
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