4Vote!
Arxiv (Free subscription) | 11/25/2009
When Inflation is embedded in a fundamental theory, such as string theory, it typically begins when the Universe is already substantially larger than the fundamental scale [such as the one defined by the string length scale]. This is naturally explained by postulating a pre-inflationary era, during which the size of the Universe grew from the fundamental scale to the initial inflationary scale. The...
5Vote!
Ask Slashdot (Free subscription) | 11/24/2009
eldavojohn writes "Petr Horava, a physicist at the University of California in Berkeley, has a new theory about gravity and spacetime. At high energies, it actually snips any ties between space and time, yet at low energies devolves to equivalence with the theory of General Relativity, which binds them together. The theory is gaining popularity with physicists because it fits some observations...
5Vote!
Chez Aspie - DJ Kirkby's blog (Free subscription) | 11/24/2009
Thank you so much to everyone who left a comment on the post below. The correct answers are in italics below and Marcus has kindly provided some additional detail in his answers for the questions that seemed to cause the most confusion. 1) If all the empty space were squeezed out of matter, the human race could fit in: a) Wembley Stadium? b) The area of the Isle of Wight? c) The volume of a sugar cube?...
4Vote!
Arxiv (Free subscription) | 11/24/2009
In this talk, I describe and defend four non-standard claims about four effective field theories, and try to extract some lessons about the limits of effective field theory. The four theses (and a capsule diagnosis given in parentheses) are: 1) Kaon loops are not a reliable part of chiral perturbation theory (dimensional regularization does not know about the chiral scale), 2) Regge physics is inappropriately...
5Vote!
Physorg (Free subscription) | 11/23/2009
A bit of imagination on the part of a measuring instrument wouldn't be a bad thing. It could help to add data from areas where the instrument is unable to measure. However, it must do so constructively. In order to infer missing data in an astronomical measurement with more than just imagination, physicists at the Max Planck Institute for Astrophysics have formulated a theory of spatial perception...
4Vote!
Red Orbit (Free subscription) | 11/23/2009
Information field theory enables astronomers, medical practitioners and geologists to look into places where their measuring instruments are blindA bit of imagination on the part of a measuring instrument wouldn’t be a bad thing. It could help to add data from areas where the instrument is unable to measure. However, it must do so constructively. In order to infer missing data in an astronomical...
4Vote!
Arxiv (Free subscription) | 11/19/2009
In this thesis, multipole expansions of mass, momentum and stress density will be made for a body in Newtonian mechanics. Using these definitions; momentum, angular momentum, center of mass, force and torque are defined for $N$ gravitationally interacting isolated bodies. Equations of motions of such a system are derived. Definitions of momentum, angular momentum, center of mass, force and torque...
4Vote!
Arxiv (Free subscription) | 11/18/2009
Since the early days of the theory of electromagnetism and of gravity the idea of space, then space-time, as a sort of physical continuum hovered the scientific community. Actually general relativity shows the strong similarity that exists between the geometrical properties of space-time and the ones of a strained elastic continuum. The bridge between geometry and the elastic potential, as well in...
5Vote!
Nature (Free subscription) | 11/18/2009
Light from a distant γ-ray burst backs up a key prediction of Albert Einstein's theory of relativity — that photon speed is the same regardless of energy. But it might set the stage for evolution of the theory.
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WorldoReason (Free subscription) | 11/15/2009
What is Quantum Loop Gravity? The Quick and Dirty: A Theory of spacetime Leading proponents include: Lee Smolin, Carlo Rovelli, John Baez, Roger Penrose and Abhay Ashtekar Alternative to string theory - views space space as made up of discrete (quantised) loops that mesh together Loops are spin networks of gravitational fields that have been energized. In short: It is a quantum theory of Gravity. It...
5Vote!
Physorg (Free subscription) | 11/12/2009
(PhysOrg.com) -- A Harvard theoretical physicist has discussed with scientists at the Large Hadron Collider in Switzerland the possibility that they may discover a theorized "stau" particle, with a lifetime of a minute or so, that could provide the first experimental confirmation of string theory.
4Vote!
Arxiv (Free subscription) | 11/12/2009
One of the main challenges in theoretical physics over the last five decades has been to reconcile quantum mechanics with general relativity into a theory of quantum gravity. However, such a theory has been proved to be hard to attain due to i) conceptual difficulties present in both the component theories (General Relativity (GR) and Quantum Theory); ii) lack of experimental evidence, since the regimes...
4Vote!
Arxiv (Free subscription) | 11/12/2009
General Relativity is not the definitive theory of Gravitation due to several shortcomings which are coming out both from theoretical and experimental viewpoints. At large scales (astrophysical and cosmological scales) the attempts to match it with the today observational data lead to invoke Dark Energy and Dark Matter as the bulk components of the cosmic fluid. Since no final evidence, at fundamental...
12Vote!
Slog (Free subscription) | 11/11/2009
Slog reader Jeff Yencho just asked me to comment on this piece of news ("I read this today and thought 'geez, I'd love to hear Charles' take on this...'"): Sometime on Nov. 3, the supercooled magnets in sector 81 of the Large Hadron Collider (LHC), outside Geneva, began to dangerously overheat. Scientists rushed to diagnose the problem, since the particle accelerator has to maintain a temperature...
4Vote!
Arxiv (Free subscription) | 11/10/2009
Our universe contains a great number of extremely compact and massive objects which are generally accepted to be black holes. Precise observations of orbital motion near candidate black holes have the potential to determine if they have the spacetime structure that general relativity demands. As a means of formulating measurements to test the black hole nature of these objects, Collins and Hughes...
3Vote!
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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