Talks

13129 - 13140 of 20131 Results

Kicking Chameleons: Early Universe Challenges for Chameleon Gravity

Adrienne Erickcek University of North Carolina at Chapel Hill

October 25, 2012

PIRSA:12100125

Astrophysics
Quantum Field Theory - Lecture 13B

Konstantin Zarembo Nordic Institute for Theoretical Physics

October 25, 2012

PIRSA:12100074

High Energy Physics
Condensed Matter - Lecture 13

Assa Auerbach Technion – Israel Institute of Technology

October 25, 2012

PIRSA:12100038

Condensed Matter
Quantum Gravity and the Weak Interactions

Lee Smolin Perimeter Institute for Theoretical Physics

Xavier Calmet University of Sussex

Stephon Alexander Brown University

Daniel Litim University of Sussex

Doug Gingrich University of Alberta

Dejan Stojkovic State University of New York (SUNY)

October 25, 2012

PIRSA:12100116

General Relativity & Quantum Cosmology
Experimental search for quantum gravity - the hard facts

Hugo Beauchemin University of Oxford

October 25, 2012

PIRSA:12100115

General Relativity & Quantum Cosmology
Quantum Field Theory - Lecture 13A

Konstantin Zarembo Nordic Institute for Theoretical Physics

October 25, 2012

PIRSA:12100020

High Energy Physics
Lorentz symmetry: Broken, intact or deformed?

Rafael Sorkin Perimeter Institute for Theoretical Physics

Sabine Hossenfelder Ludwig-Maximilians-Universität München (LMU)

David Mattingly University of New Hampshire

Niayesh Afshordi University of Waterloo

Daniel Sudarsky Universidad Nacional Autónoma De Mexico (UNAM)

Stefano Liberati SISSA International School for Advanced Studies

Joao Magueijo Imperial College London

October 24, 2012

PIRSA:12100108

General Relativity & Quantum Cosmology
12/13 PSI Researcher Presentation

Matthew Johnson York University

October 24, 2012

PIRSA:12100050

Astrophysics
Astrophysical Searches for Quantum Gravity Signals

Jonathan Granot University of Hertfordshire

October 24, 2012

PIRSA:12100058

General Relativity & Quantum Cosmology
Dynamical Dimensional Reduction

Dejan Stojkovic State University of New York (SUNY)

Astrid Eichhorn Universität Heidelberg

Martin Reuter Johannes Gutenberg University Mainz

October 24, 2012

PIRSA:12100104

General Relativity & Quantum Cosmology
Quantum Field Theory - Lecture 12B

Konstantin Zarembo Nordic Institute for Theoretical Physics

October 24, 2012

PIRSA:12100073

High Energy Physics
Condensed Matter - Lecture 12

Assa Auerbach Technion – Israel Institute of Technology

October 24, 2012

PIRSA:12100037

Condensed Matter

Kicking Chameleons: Early Universe Challenges for Chameleon Gravity

Adrienne Erickcek University of North Carolina at Chapel Hill

October 25, 2012

PIRSA:12100125

Astrophysics

Chameleon gravity is a scalar-tensor theory that mimics general relativity in the Solar System. The scalar degree of freedom is hidden in high-density environments because the effective mass of the chameleon scalar depends on the trace of the stress-energy tensor. In the early Universe, when the trace of the stress-energy tensor is nearly zero, the chameleon is very light and Hubble friction prevents it from reaching its potential minimum. Whenever a particle species becomes non-relativistic, however, the trace of the stress-energy tensor is temporarily nonzero, and the chameleon begins to roll. I will show that these "kicks" to the chameleon field have catastrophic consequences for chameleon gravity. The velocity imparted to the chameleon is sufficiently large that the chameleon's mass changes rapidly as it slides past its potential minimum. This nonadiabatic process shatters the chameleon field by generating extremely high-energy perturbations, casting doubt on chameleon gravity's viability as an alternative to general relativity.
Quantum Field Theory - Lecture 13B

Konstantin Zarembo Nordic Institute for Theoretical Physics

October 25, 2012

PIRSA:12100074

High Energy Physics
Condensed Matter - Lecture 13

Assa Auerbach Technion – Israel Institute of Technology

October 25, 2012

PIRSA:12100038

Condensed Matter
Quantum Gravity and the Weak Interactions

Lee Smolin Perimeter Institute for Theoretical Physics

Xavier Calmet University of Sussex

Stephon Alexander Brown University

Daniel Litim University of Sussex

Doug Gingrich University of Alberta

Dejan Stojkovic State University of New York (SUNY)

October 25, 2012

PIRSA:12100116

General Relativity & Quantum Cosmology

Quantum Gravity and the Weak Interactions
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Non-thermal quantum black holes
Motivated by the lack of evidence for physics beyond the Standard Model in the TeV region, we discussed an alternative path for grand unification. We show that simple grand unification models based on e.g. SU(5) can work successfully even without low scale supersymmetry. In particular quantum gravitational effects could easily modify the unification conditions for the gauge and Yukawa couplings.
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Searches for Nonperturbative Gravitational States at the LHC
Searches for black holes and string balls have recently be performed by LHC experiments. Upper limits have been placed on the production crosssections time experimental acceptance. Hard-disk production of thesestates have been ruled out over most of the current LHC energy reach.However the LHC has said little about nonperturbative states producedin model with reduced cross sections. I will discuss some popularmodels that have not yet been ruled out by the LHC experiments.
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Models of new physics beyond the Standard Model of Particle Physics
Models of new physics beyond the Standard Model of Particle Physics suggest that the quantum scale of gravity could be as low as the electro-weak or TeV energy scale. If so, they offer the exciting possibility that quantum gravity becomes accessible, experimentally, at particle colliders such as the LHC. From the theory side, low-scale gravity scenarios often require extra dimensions, or a large number of additional particle species.
I propose to discuss the possibility for signatures of low-scale quantum gravity, the feasibility of concrete (quantitative) predictions based on eg. specific processes and quantum gravity set-ups, and options for experimental tests.
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Unification of gravity with the electroweak interactions
Experimental search for quantum gravity - the hard facts

Hugo Beauchemin University of Oxford

October 25, 2012

PIRSA:12100115

General Relativity & Quantum Cosmology

The LHC has been running for over 2 years and the different experiments have accumulated enough data to find a new particle which could well be the Higgs boson, achieve Standard Model measurements with precision at the percent level, and seriously constrain a large variety of new physics scenarios, giving important hints on what the physics beyond the Standard Model can be and what it cannot be. This presentation will focus on ATLAS and CMS latest searches for new physics in events featuring signatures relevant to theories of quantum gravity. Will be presented the results on searches for large extra dimensions (direct graviton emission, virtual graviton propagation, Kaluza-Klein Randall-Sundrum resonances, etc.) and other TeV-scale gravity phenomena such as black holes (rotating and non-rotating) and string balls production and decay. Results will be reported on each of the various final states investigated for each signals. The results of some searches that are not typically interpreted into bounds on quantum gravity signals, but which could provide complementary information such as the number of possible matter fields compatible with LHC data will also be presented. An attempt to present plausible future reach of the LHC will finally be briefly discussed.
Quantum Field Theory - Lecture 13A

Konstantin Zarembo Nordic Institute for Theoretical Physics

October 25, 2012

PIRSA:12100020

High Energy Physics
Lorentz symmetry: Broken, intact or deformed?

Rafael Sorkin Perimeter Institute for Theoretical Physics

Sabine Hossenfelder Ludwig-Maximilians-Universität München (LMU)

David Mattingly University of New Hampshire

Niayesh Afshordi University of Waterloo

Daniel Sudarsky Universidad Nacional Autónoma De Mexico (UNAM)

Stefano Liberati SISSA International School for Advanced Studies

Joao Magueijo Imperial College London

October 24, 2012

PIRSA:12100108

General Relativity & Quantum Cosmology

Is aether technically natural?
I will discuss whether higher energy Lorentz violation should be considered a natural expectation in theories of quantum gravity with a preferred frame.
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If spacetime is a causal set then Lorentz symmetry is unbroken
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Quantum superpositions of the speed of light
If the metric is an operator, it can exist in superpositions. The simplest case one can look at is a superposition of flat spaces which differ only in the value of the speed of light. I will lay out how such superpositions can be incorporated into quantum field theory, and discuss the fate of Lorentz-invariance in this scenario.
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Relative locality and fate of Lorentz symmetry
In my talk I will briefly introduce the idea of relative locality, being a particular regime of quantum gravity characterized by negligible Planck length and finite Planck mass. Then I will discuss possible scenarios concerning the fate of Lorentz symmetry in this regime.
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Observational constraints on scale hierarchy in Horava-Lifshiftz gravity
Horava-Lifshitz gravity models contain higher order operators suppressed by a characteristic scale, which is required to be parametrically smaller than the Planck scale. We show that recomputed synchrotron radiation constraints from the Crab nebula suffice to exclude the possibility that this scale is of the same order of magnitude as the Lorentz breaking scale in the matter sector. This highlights the need for a mechanism that suppresses the percolation of Lorentz violation in the matter sector and is effective for higher order operators as well.
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Breaking Lorentz invariance: the Universe loves it!
I show how the local Lorentz and / or diffeomorphism invariances may be broken by a varying speed of light, softly or harshly, depending on taste. Regardless of the fundamental implications of such dramas, these smmetry breakings may be of great practical use in cosmology. They may solve the horizon and flatness problesm. A near scale-invariant sprectrum of fluctuation may arise, even without inflation. Distinct observational imprints may be left.
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Quantum Gravity Phenomenology without Lorentz Invariance Violation
Is there hope to see quantum gravity effects if the underlying theory is strictly respecting of Lorentz invariance? I will discuss a novel class of possibilities, suggested by analogy with some simple solid state physics, including one that has lead to an actual experiment, which has placed the first relevant constraints on these kind of effects
12/13 PSI Researcher Presentation

Matthew Johnson York University

October 24, 2012

PIRSA:12100050

Astrophysics
Astrophysical Searches for Quantum Gravity Signals

Jonathan Granot University of Hertfordshire

October 24, 2012

PIRSA:12100058

General Relativity & Quantum Cosmology

Some recent searches for quantum gravity signatures using observations of distant astrophysical sources will be discussed, focusing on the search for Lorentz invariance violation (LIV) in the form of a dependence of the photon propagation speed on its energy. Fermi gamma-ray space telescope observations of ~8 keV to ~30 GeV photons from a short (< 1 s) gamma-ray burst (GRB 090510) at a cosmological distance (z = 0.903), enabled for the first time to put a direct time of flight limit on a possible linear variation of the speed of light with photon energy that is beyond the Planck scale. Parameterizing |v/c-1| = E/E_{QG} our most conservative limits are E_{QG}/E_{Planck} > 1.2, while less conservative limits are up to 1-2 orders of magnitude stricter. Other types of astrophysical searches for LIV will be briefly outlined, along with some prospects for the future.
Dynamical Dimensional Reduction

Dejan Stojkovic State University of New York (SUNY)

Astrid Eichhorn Universität Heidelberg

Martin Reuter Johannes Gutenberg University Mainz

October 24, 2012

PIRSA:12100104

General Relativity & Quantum Cosmology

Dynamical dimensional reduction and Asymptotic Safety
The effective average action approach to Quantum Einstein Gravity (QEG) is discussed as a natural framework for exploring the scale dependent Riemannian geometry and multifractal micro-structure of the effective spacetimes predicted by QEG. Their fractal properties are related to the functional RG flow on theory space, and the special role of the running cosmological constant is emphasized. The prospects of an experimental verification will also be discussed.
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Vanishing dimension: theory and phenomenology
Lower-dimensionality at higher energies has manifold theoretical advantages as recently pointed out. Moreover, it appears that experimental evidence may already exists for it - a statistically significant planar alignment of events with energies higher than TeV has been observed in some earlier cosmic ray experiments. If this alignment is not a fluke, then the LHC should be able to see effects associated with the dimensional crossover. Further, (2+1)-dimensional spacetimes have no gravitational degrees of freedom, and gravity waves cannot be produced in that epoch in the early universe. This places a universal maximum frequency at which primordial gravity waves can propagate, which may be accessible to future gravitational wave detectors such as LISA. In this talk, the theoretical motivation for "vanishing dimensions" as well as generic experimental and observational signature will be discussed
Quantum Field Theory - Lecture 12B

Konstantin Zarembo Nordic Institute for Theoretical Physics

October 24, 2012

PIRSA:12100073

High Energy Physics
Condensed Matter - Lecture 12

Assa Auerbach Technion – Israel Institute of Technology

October 24, 2012

PIRSA:12100037

Condensed Matter

Title	Date	Collection	Type	Info
Kicking Chameleons: Early Universe Challenges for Chameleon Gravity	2012‑10‑25	Cosmology and Gravitation	Scientific Series	View details
Quantum Field Theory - Lecture 13B	2012‑10‑25	12/13 PSI - Quantum Field Theory 1	Course	View details
Condensed Matter - Lecture 13	2012‑10‑25	12/13 PSI - Condensed Matter	Course	View details
Quantum Gravity and the Weak Interactions	2012‑10‑25	Experimental Search for Quantum Gravity 2012	Conference	View details
Experimental search for quantum gravity - the hard facts	2012‑10‑25	Experimental Search for Quantum Gravity 2012	Conference	View details
Quantum Field Theory - Lecture 13A	2012‑10‑25	12/13 PSI - Quantum Field Theory 1	Course	View details
Lorentz symmetry: Broken, intact or deformed?	2012‑10‑24	Experimental Search for Quantum Gravity 2012	Conference	View details
12/13 PSI Researcher Presentation	2012‑10‑24	12/13 PSI Researcher Presentations	Course	View details
Astrophysical Searches for Quantum Gravity Signals	2012‑10‑24	Experimental Search for Quantum Gravity 2012	Scientific Series	View details
Dynamical Dimensional Reduction	2012‑10‑24	Experimental Search for Quantum Gravity 2012	Conference	View details
Quantum Field Theory - Lecture 12B	2012‑10‑24	12/13 PSI - Quantum Field Theory 1	Course	View details
Condensed Matter - Lecture 12	2012‑10‑24	12/13 PSI - Condensed Matter	Course	View details

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Format results

Kicking Chameleons: Early Universe Challenges for Chameleon Gravity

Quantum Field Theory - Lecture 13B

Condensed Matter - Lecture 13

Quantum Gravity and the Weak Interactions

Experimental search for quantum gravity - the hard facts

Quantum Field Theory - Lecture 13A

Lorentz symmetry: Broken, intact or deformed?

12/13 PSI Researcher Presentation

Astrophysical Searches for Quantum Gravity Signals

Dynamical Dimensional Reduction

Quantum Field Theory - Lecture 12B

Condensed Matter - Lecture 12

Kicking Chameleons: Early Universe Challenges for Chameleon Gravity

Quantum Field Theory - Lecture 13B

Condensed Matter - Lecture 13

Quantum Gravity and the Weak Interactions

Experimental search for quantum gravity - the hard facts

Quantum Field Theory - Lecture 13A

Lorentz symmetry: Broken, intact or deformed?

12/13 PSI Researcher Presentation

Astrophysical Searches for Quantum Gravity Signals

Dynamical Dimensional Reduction

Quantum Field Theory - Lecture 12B

Condensed Matter - Lecture 12