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Arxiv (Free subscription) | yesterday
The problem of cosmological particle creation for a spatially flat, homogeneous and isotropic Universes is discussed in the context of f(R) theories of gravity. Different from cosmological models based on general relativity theory, it is found that a conformal invariant metric does not forbid the creation of massless particles during the early stages (radiation era) of the Universe.
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Astronomy Cmarchesin (Free subscription) | 11/06/2009
The rapidly rotating ultradense remnant of a massive star, a pulsar emits jets of radiation that sweep across space like a lighthouse beam, as shown in this illustration. For the first time, gamma-ray observations have provided clues to radio astronomers about where to find millisecond pulsars. Credit: NASA Fermi Telescope observations provide candidates to check for radio emissions By Ron Cow WASHINGTON...
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Ars Technica (Free subscription) | 11/05/2009
It was 1687 when Issac Newton first published his Philosophiæ Naturalis Principia Mathematica in which he first described his universal law of gravitation—the inverse square law that we are all taught in middle school science class. Nearly 230 years passed before Newton's law was dethroned by Albert Einstein's theory of general relativity, a theory of gravity that reconciled Newton's work...
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the evolving mind (Free subscription) | 11/05/2009
One of my favorite scenes from the sitcom, The Big Bang Theory, has two of the science nerds (Sheldon and Rajesh) working hard at tackling a tough science problem. What are they doing? Outwardly, nothing much. Just staring at a blackboard with a few strings of symbols chalked on it. Minutes [...]
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The complete works of TGR Worzel (Free subscription) | 11/04/2009
The BBC did a pretty good job of explaining black holes on Horizon: Who's afraid of a big black hole? , last night. The photography was a little distracting from what was being said, the cameraman & director seemed to be chasing an award I think, but what was actually said on the programme explained the subject quite well. I was also a little bit distracted by how visually similar Prof. Michio...
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Arxiv (Free subscription) | 11/02/2009
Compactification of type IIB theory on torus, in the presence of fluxes, is considered. The reduced effective action is expressed in manifestly S-duality invariant form. Cosmological solutions of the model are discussed in several cases in the Pre-Big Bang scenario.
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To God and my country (Free subscription) | 10/31/2009
SPOOKY! Is Unknown Force In Universe Acting On Dark Matter? It is possible that a non-gravitational fifth force is ruling the dark matter with an invisible hand, leaving the same fingerprints on all galaxies, irrespective of their ages, shapes and sizes." Such a force might solve an even bigger mystery, known as 'dark energy', which is ruling the accelerated expansion of the Universe. A more radical...
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Arxiv (Free subscription) | 10/28/2009
In this speculative work I investigate whether God may find a place in theoretical physics. The comparison between some aspects of the nature of God, as deduced by the philosopher St. Augustine, and general relativity, suggests to identify God with a chronology violating region of spacetime. From this conclusion some physical suggestions can be drawn. Among them novel solutions to the homogeneity...
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Arxiv (Free subscription) | 10/28/2009
The energy-momentum tensor, which is coordinate independent, is used to calculate energy, momentum and angular-momentum of two different tetrad fields. Although, the two tetrad fields reproduce the same space-time their energies are different. Therefore, a regularized expression of the gravitational energy-momentum tensor of the teleparallel equivalent of general relativity, (TEGR), is used to make...
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Arxiv (Free subscription) | 10/28/2009
We explore the features of gravity in its quantum regime in a mathematically rigorous way by carrying out the classical and quantum formulations of some two-Killing symmetry reductions of general relativity which admit an exact Fock/Schr\"{o}dinger quantization. Concretely, we analyze in depth the linearly polarized 3-handle (S1xS2) and 3-sphere (S3) Gowdy cosmological models coupled to massless...
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Cosmic Variance (Free subscription) | 10/27/2009
As we recently noted, Stephen Hawking has stepped down from the Lucasian Chair at Cambridge. The chair didn’t stay empty for long. It has been announced that Michael Green will become the new Lucasian Professor. Green is one of the pioneers of string theory, and is already at Cambridge. I’m not sure he even switches [...]
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Astronomy Cmarchesin (Free subscription) | 10/27/2009
Up until about 400,000 years after the big bang the Universe was a liquid-like plasma of protons and electrons (“baryons”) in which photons of light were trapped; dark matter was also part of the mix. Imagine a single perturbation, like a stone dropped in a pond: baryons and photons ripple outward togther, traveling through the plasma in a sound wave. But when the Universe cooled enough...
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Astronomy Cmarchesin (Free subscription) | 10/27/2009
Mass can act like a lens: a mass like that of a star or giant planet can displace the apparent position of distant stars. Very massive objects like clumps of dark matter can be strong gravitational lenses. Weak lensing is less obvious but just as useful in “weighing” invisible dark matter. (Strong gravitational lens in Abell 2218 by Hubble Space Telescope; inset from Sean Carroll, “Spacetime...
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Ria Novosti (Free subscription) | 10/27/2009
To see how the world is made is the goal of science. It has penetrated the depths of the Universe, and there are theories of what happened the first instances after the Big Bang, the prime mover of Creation-yet no one knows how the solar system was born.
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Arxiv (Free subscription) | 10/27/2009
In the context of Born-Infeld \emph{determinantal} gravity formulated in a 3-dimensional spacetime with absolute parallelism, we found an exact \emph{vacuum} circular symmetric solution without cosmological constant consisting in a rotating spacetime with non singular behavior. The space behaves at infinity as the conical geometry typical of 3-dimensional General Relativity without cosmological constant....
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orianabvc | 02/05/2009
Leonard and Penny are drawn together after a disastrous visit from Leonard’s mother (Christine Baranski).
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en - (not a member) - 10/26/2009
Dr
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en - (not a member) - 10/22/2009
I finally found a working stream posted at http://leafpen.com/54376 I had to fill out some dumb survey but it worked!! ! !
en - (not a member) - 10/16/2009
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eddymkl | 02/05/2009
Leonard and Penny are drawn together after a disastrous visit from Leonard’s mother (Christine Baranski).
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waynebvc | 02/04/2009
“The Maternal Capacitance” - A disastrous visit from Mrs. Hofstadter brings Leonard and Penny closer together, on THE BIG BANG THEORY, Monday, Feb. 9 (8:00-8:30 PM, ET/PT) on the CBS Television Network.
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