Day # 2
The conference is composed of experts and students from many approaches. Therefore, you can imagine that some of the presentations are not of interest or understandable enough to generate a flurry of questions or discussion.
A comment given to me was that the student fear asking questions that would appear to demonstrated their lack of understanding. This is especially true when the conference is being recorded.
This, therefore, increases the value of physics forums in distributing information.
The organizers offered all of the presenters to submit their presentation and they would put them online. Let’s watch for the development.
A few comments on the presentations
Affleck
Bosonization … successes and limitations
He was a speed talker and I could not take notes fast enough and pay attention at the same time.
In condense matter Lorentz invariance is often broken ( eg. 3d crystals)
Example: Fail Green function
http://en.wikipedia.org/wiki/Green's_function
Depending on the shape of the cos curvature from the Fermi surface to the next energy level.
Those who didn’t need to look up what I said might be able to furnish more detailed info.
Van Raamsdonk
Here is his paper
http://arxiv.org/abs/0907.2939
Comments on quantum gravity and entanglement
(Submitted on 17 Jul 2009)
G.Semenoff
His talk was based upon
http://arxiv.org/abs/hep-th/0605080
AdS/CFT v.s. String Loops
Authors: Gianluca Grignani, Marta Orselli, Bojan Ramadanovic, Gordon W. Semenoff, Donovan Young
(Submitted on 8 May 2006)
As you can see … a mixture of experts trying to communicate to experts in other fields.
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Now we come to the anticipated discussions of Horava's recent article
http://arxiv.org/abs/0901.3775
Quantum Gravity at a Lifgarbagez Point
Authors: Petr Horava
(Submitted on 26 Jan 2009 (v1), last revised 2 Mar 2009 (this version, v2))
Matt Visser was the first to of 4 to speak. (very eloquent and passionate )
http://arxiv.org/abs/0902.0590
Lorentz symmetry breaking as a quantum field theory regulator
Authors: Matt Visser (Victoria University of Wellington)
(Submitted on 3 Feb 2009 (v1), last revised 17 Jul 2009 (this version, v3))
Short notes:
Planck scale and Lorentz symmetry scale breaking will be different.
There has been a proliferation of papers. ( cited 120 times) This subject is hot, hot!
Horava introduced “a preferred foliation”. There are questions of “Projectability’, “detail balance”
Matt Visser will hold judgment for another 6 month of analysis.
Robert Brandenberger
He has two personalities. He becomes a completely different person when presenting his paper to an audience. Wow! He comes alive!
Here is his paper.
http://arxiv.org/abs/0904.2835
Matter Bounce in Horava-Lifgarbagez Cosmology
Authors: Robert Brandenberger (McGill University and CERN)
(Submitted on 18 Apr 2009 (v1), last revised 22 Apr 2009 (this version, v2))
Abstract: Horava-Lifgarbagez gravity, a recent proposal for a UV-complete renormalizable gravity theory, may lead to a bouncing cosmology. In this note we argue that Horava-Lifgarbagez cosmology may yield a concrete realization of the matter bounce scenario, and thus give rise to an alternative to inflation for producing a scale-invariant spectrum of cosmological perturbations. In this scenario, quantum vacuum fluctuations exit the Hubble radius in the pre-bounce phase and the spectrum is transformed into a scale-invariant one on super-Hubble scales before the bounce because the long wavelength modes undergo squeezing of their wave-functions for a longer period of time than shorter wavelength modes. The scale-invariance of the spectrum of curvature fluctuations is preserved during and after the bounce. A distinctive prediction of this scenario is the amplitude and shape of the bispectrum.
If you have not figured it out The Horava Lipggarbagez gravity is an alternative “driver” for inflation.
Paul Saffin
http://arxiv.org/abs/0905.2579
Strong coupling in Horava gravity
Authors: Christos Charmousis, Gustavo Niz, Antonio Padilla, Paul M. Saffin
(Submitted on 15 May 2009 (v1), last revised 21 May 2009 (this version, v2))
Abstract: By studying perturbations about the vacuum, we show that Horava gravity suffers from two different strong coupling problems, extending all the way into the deep infra-red. The first of these is associated with the principle of detailed balance and explains why solutions to General Relativity are typically not recovered in models that preserve this structure. The second of these occurs even without detailed balance and is associated with the breaking of diffeomorphism invariance, required for anisotropic scaling in the UV. Since there is a reduced symmetry group there are additional degrees of freedom, which need not decouple in the infra-red. Indeed, we use the Stuckelberg trick to show that one of these extra modes become strongly coupled as the parameters approach their desired infrared fixed point. Whilst we can evade the first strong coupling problem by breaking detailed balance, we cannot avoid the second, whatever the form of the potential. Therefore the original Horava model, and its "phenomenologically viable" extensions do not have a perturbative General Relativity limit at any scale. Experiments which confirm the perturbative gravitational wave prediction of General Relativity, such as the cumulative shift of the periastron time of binary pulsars, will presumably rule out the theory.
Jiawei Mei
http://arxiv.org/abs/0904.1595
Solutions to Horava Gravity
Authors: H. Lu, Jianwei Mei, C.N. Pope
(Submitted on 10 Apr 2009 (v1), last revised 31 Jul 2009 (this version, v4))
Abstract: Recently Horava proposed a non-relativistic renormalisable theory of gravitation, which reduces to Einstein's general relativity at large distances, and that may provide a candidate for a UV completion of Einstein's theory. In this paper, we derive the full set of equations of motion, and then we obtain spherically symmetric solutions and discuss their properties. We also obtain solutions for the Friedman-Lemaitre-Robertson-Walker cosmological metric.
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As you can see, my comments are brief. The importance of these papers overrule my comments.
Gnite!
Jal
Ps. I was allowed in the group picture. :-)
