Experimental Search for Quantum Gravity 2012

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
Quantum Gravity
Experimental search for quantum gravity - the hard facts

Hugo Beauchemin
University of Oxford
October 25, 2012

PIRSA:12100115
Quantum Gravity
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
Quantum Gravity
Experimental tests of CPT symmetry

Antonio Di Domenico
Sapienza University of Rome

October 25, 2012

PIRSA:12100120
Effective field theory framework in QG
- Xavier Calmet
  University of Sussex
- Roberto Percacci
  SISSA International School for Advanced Studies
- Astrid Eichhorn
  University of Southern Denmark
- Martin Reuter
  Johannes Gutenberg University Mainz
October 25, 2012

PIRSA:12100121
Quantum Gravity

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
Quantum Gravity
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
Experimental search for quantum gravity - the hard facts

Hugo Beauchemin
University of Oxford
October 25, 2012

PIRSA:12100115
Quantum Gravity
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 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
Quantum Gravity
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 tests of CPT symmetry

Antonio Di Domenico
Sapienza University of Rome

October 25, 2012

PIRSA:12100120

The three discrete symmetries of Quantum Mechanics, charge conjugation, parity, and time reversal, are all violated, singly or in pairs. CPT is the only combination of these symmetries which appears to be conserved in Nature. Even though this result is in agreement with the well known CPT theorem, that holds for standard quantum field theories, CPT violation in some cases might be expected and justified in the framework of a quantum theory of gravity. Here the last and more refined experimental searches for CPT violation effects will be reported with a special focus on the tests performed on neutral meson systems and the interplay between CPT symmetry and the basic principles of Quantum Mechanics. No deviation from the expectations of CPT symmetry and quantum mechanics is observed, while the precision of the measurements, in some cases, reaches the interesting Planck scale region. Finally, prospects for this kind of experimental studies will be presented.
Effective field theory framework in QG
- Xavier Calmet
  University of Sussex
- Roberto Percacci
  SISSA International School for Advanced Studies
- Astrid Eichhorn
  University of Southern Denmark
- Martin Reuter
  Johannes Gutenberg University Mainz
October 25, 2012

PIRSA:12100121
Quantum Gravity
Gravity Induced Grand Unification
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.
_____________________________

Testing the consistency of quantum gravity with low-energy properties of the standard model
Testing quantum gravity is possible by using, e.g. the available data on the properties of the standard model. I will discuss how a parameterisation of quantum gravity fluctuations in terms of metric fluctuations can be used to test the compatibility of quantum gravity with the observed low-energy properties of the standard model, such as the existence of fermions with masses much below the Planck mass.
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The Asymptotic Safety program
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.

Title	Speaker(s)	Date	Talk Type	Info
Lorentz symmetry: Broken, intact or deformed?	Rafael Sorkin, Sabine Hossenfelder, David Mattingly, Niayesh Afshordi, Daniel Sudarsky, Stefano Liberati, Joao Magueijo	2012-10-24	Conference	View details
Experimental search for quantum gravity - the hard facts	Hugo Beauchemin	2012-10-25	Conference	View details
Quantum Gravity and the Weak Interactions	Lee Smolin, Xavier Calmet, Stephon Alexander, Daniel Litim, Doug Gingrich, Dejan Stojkovic	2012-10-25	Conference	View details
Experimental tests of CPT symmetry	Antonio Di Domenico	2012-10-25	Conference	View details
Effective field theory framework in QG	Xavier Calmet, Roberto Percacci, Astrid Eichhorn, Martin Reuter	2012-10-25	Conference	View details

Experimental Search for Quantum Gravity 2012

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