Gravity iv conference
Posted Aug26-09 at 07:57 PM by jal
Updated Dec20-09 at 12:47 AM by jal (inserted: Gravity at a Lifshitz Point Conference at perimeter)
Updated Dec20-09 at 12:47 AM by jal (inserted: Gravity at a Lifshitz Point Conference at perimeter)
The BIG question?
How is the universe made and how does the universe work?
Is our world also emergent from an underlying condensed matter like theory.
I do not need to produce a math description of
"TOMMORROW'S BIG BANG".
It's already done.
See Horava's recent article
http://arxiv.org/abs/0901.3775
Quantum Gravity at a Lifshitz Point
Authors: Petr Horava
(Submitted on 26 Jan 2009 (v1), last revised 2 Mar 2009 (this version, v2))
Matt Visser was the first 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-Lifshitz Cosmology
Authors: Robert Brandenberger (McGill University and CERN)
(Submitted on 18 Apr 2009 (v1), last revised 22 Apr 2009 (this version, v2))
Abstract: Horava-Lifshitz gravity, a recent proposal for a UV-complete renormalizable gravity theory, may lead to a bouncing cosmology. In this note we argue that Horava-Lifshitz 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 Lipgshitz 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 infra-red 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.
--------
In the following months, I'm sure that there will be papers that will help to clarify the big questions.
How is the universe made and how does the universe work?
Is our world also emergent from an underlying condensed matter like theory.
-----
Now you can be a fly on the wall.
Petr Horava is in the ideal situation of having serious consideration of his approach being evaluated by other peers in an open forum. I found that there was an extremely high degree of understanding and as a result a serious exchange of ideas.
http://pirsa.org/C09026
Gravity at a Lifshitz Point
November 8 - 10, 2009 Perimeter Institute
The construction of a quantum theory of gravity might require us to give up one or more of the fundamental principles of standard quantum field theory. A recent proposal dispensing with Lorentz invariance builds upon an analogy with condensed matter systems characterized by a Lifshitz point. This proposal also seems to produce a theory which is well behaved in the ultraviolet regime.
This workshop intends to bring together researchers working on this or related ideas. The focus will be on the viability of the proposal (compatibility with large scale phenomenology and renormalizabilty) and its relation to other research directions, like causal dynamical triangulations and aether theories.
A good place to start reading is at
PIRSA:09110066 *( Flash Presentation, Windows Presentation, Windows Video File* , PDF ) Which Format?
Workshop Summary and Discussion
Speaker(s): Ted Jacobson
Abstract:
Date: 10/11/2009 - 3:00 pm
Collection: Gravity at a Lifshitz Point
=====
Here a couple of other papers that are not part of presentations.
http://arxiv.org/abs/0911.0401
Spectral geometry as a probe of quantum spacetime
Dario Benedetti, Joe Henson
(Submitted on 2 Nov 2009)
Employing standard results from spectral geometry, we provide strong evidence that in the classical limit the ground state of three-dimensional causal dynamical triangulations is de Sitter spacetime. This result is obtained by measuring the expectation value of the spectral dimension on the ensemble of geometries defined by these models, and comparing its large scale behaviour to that of a sphere (Euclidean de Sitter). From the same measurement we are also able to confirm the phenomenon of dynamical dimensional reduction observed in this and other approaches to quantum gravity -- the first time this has been done for three-dimensional causal dynamical triangulations. In this case, the value for the short-scale limit of the spectral dimension that we find is approximately 2. We comment on the relevance of these results for the comparison to asymptotic safety and Horava-Lifshitz gravity, among other approaches to quantum gravity.
====
http://arxiv.org/abs/0910.5852
New Models of f(R) Theories of Gravity
J. Kluson
(Submitted on 30 Oct 2009 (v1), last revised 2 Nov 2009 (this version, v2))
We introduce new models of f(R) theories of gravity that are generalization of Horava-Lifshitz gravity.
How is the universe made and how does the universe work?
Is our world also emergent from an underlying condensed matter like theory.
I do not need to produce a math description of
"TOMMORROW'S BIG BANG".
It's already done.
See Horava's recent article
http://arxiv.org/abs/0901.3775
Quantum Gravity at a Lifshitz Point
Authors: Petr Horava
(Submitted on 26 Jan 2009 (v1), last revised 2 Mar 2009 (this version, v2))
Matt Visser was the first 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-Lifshitz Cosmology
Authors: Robert Brandenberger (McGill University and CERN)
(Submitted on 18 Apr 2009 (v1), last revised 22 Apr 2009 (this version, v2))
Abstract: Horava-Lifshitz gravity, a recent proposal for a UV-complete renormalizable gravity theory, may lead to a bouncing cosmology. In this note we argue that Horava-Lifshitz 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 Lipgshitz 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 infra-red 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.
--------
In the following months, I'm sure that there will be papers that will help to clarify the big questions.
How is the universe made and how does the universe work?
Is our world also emergent from an underlying condensed matter like theory.
-----
Now you can be a fly on the wall.
Petr Horava is in the ideal situation of having serious consideration of his approach being evaluated by other peers in an open forum. I found that there was an extremely high degree of understanding and as a result a serious exchange of ideas.
http://pirsa.org/C09026
Gravity at a Lifshitz Point
November 8 - 10, 2009 Perimeter Institute
The construction of a quantum theory of gravity might require us to give up one or more of the fundamental principles of standard quantum field theory. A recent proposal dispensing with Lorentz invariance builds upon an analogy with condensed matter systems characterized by a Lifshitz point. This proposal also seems to produce a theory which is well behaved in the ultraviolet regime.
This workshop intends to bring together researchers working on this or related ideas. The focus will be on the viability of the proposal (compatibility with large scale phenomenology and renormalizabilty) and its relation to other research directions, like causal dynamical triangulations and aether theories.
A good place to start reading is at
PIRSA:09110066 *( Flash Presentation, Windows Presentation, Windows Video File* , PDF ) Which Format?
Workshop Summary and Discussion
Speaker(s): Ted Jacobson
Abstract:
Date: 10/11/2009 - 3:00 pm
Collection: Gravity at a Lifshitz Point
=====
Here a couple of other papers that are not part of presentations.
http://arxiv.org/abs/0911.0401
Spectral geometry as a probe of quantum spacetime
Dario Benedetti, Joe Henson
(Submitted on 2 Nov 2009)
Employing standard results from spectral geometry, we provide strong evidence that in the classical limit the ground state of three-dimensional causal dynamical triangulations is de Sitter spacetime. This result is obtained by measuring the expectation value of the spectral dimension on the ensemble of geometries defined by these models, and comparing its large scale behaviour to that of a sphere (Euclidean de Sitter). From the same measurement we are also able to confirm the phenomenon of dynamical dimensional reduction observed in this and other approaches to quantum gravity -- the first time this has been done for three-dimensional causal dynamical triangulations. In this case, the value for the short-scale limit of the spectral dimension that we find is approximately 2. We comment on the relevance of these results for the comparison to asymptotic safety and Horava-Lifshitz gravity, among other approaches to quantum gravity.
====
http://arxiv.org/abs/0910.5852
New Models of f(R) Theories of Gravity
J. Kluson
(Submitted on 30 Oct 2009 (v1), last revised 2 Nov 2009 (this version, v2))
We introduce new models of f(R) theories of gravity that are generalization of Horava-Lifshitz gravity.
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