Experimental Search for Quantum Gravity 2012

17 talks

October 22, 2012 - October 25, 2012

C12043

Collection Type Conference/School

Description Experimental Search for Quantum Gravity

Displaying 1 - 12 of 17

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
Experimental tests of CPT symmetry

Antonio Di Domenico Sapienza University of Rome

October 25, 2012 PIRSA:12100120
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 search for quantum gravity - the hard facts

Hugo Beauchemin University of Oxford
October 25, 2012 PIRSA:12100115
Quantum Gravity
Lorentz symmetry: Broken, intact or deformed?
- Rafael Sorkin Perimeter Institute for Theoretical Physics
- Sabine Hossenfelder Frankfurt Institute for Advanced Studies (FIAS)
- 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
Astrophysical Searches for Quantum Gravity Signals

Jonathan Granot University of Hertfordshire
October 24, 2012 PIRSA:12100058
Quantum Gravity
Dynamical Dimensional Reduction
- Dejan Stojkovic State University of New York (SUNY)
- Astrid Eichhorn University of Southern Denmark
- Martin Reuter Johannes Gutenberg University Mainz
October 24, 2012 PIRSA:12100104
Quantum Gravity
Cosmological Constant
- Ivan Arraut Osaka City University
- Stephon Alexander Brown University
- Alejandro Satz
- Maïté Dupuis Perimeter Institute for Theoretical Physics
- Antonino Marciano Fudan University - Physics Department
October 23, 2012 PIRSA:12100126
Cosmology
Quantum Gravity Effects in Black Holes and Gravitational Waves
- Giovanni Amelino-Camelia Sapienza Università di Roma - Dipartimento di Fisica
- David Mattingly University of New Hampshire
- Nicolas Yunes University of Illinois System
- Avery Broderick University of Waterloo
October 23, 2012 PIRSA:12100094
Quantum Gravity
Searching for Quantum Gravity with the IceCube Neutrino Observatory

John Kelley University of Wisconsin–Madison
October 23, 2012 PIRSA:12100093
Quantum Gravity
Quantum Gravity Effects in the (Early and Late) Universe
- Stephon Alexander Brown University
- Daniel Sudarsky Universidad Nacional Autónoma De Mexico (UNAM)
- Daniel Litim University of Sussex
- Robert Brandenberger McGill University - Department of Physics
October 23, 2012 PIRSA:12100090
Quantum Gravity
The highest-energy particles of the Universe as viewed by the Pierre Auger Observatory

Markus Risse University of Siegen

October 23, 2012 PIRSA:12100089

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.
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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.
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.
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 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.
Lorentz symmetry: Broken, intact or deformed?
- Rafael Sorkin Perimeter Institute for Theoretical Physics
- Sabine Hossenfelder Frankfurt Institute for Advanced Studies (FIAS)
- 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
Astrophysical Searches for Quantum Gravity Signals

Jonathan Granot University of Hertfordshire
October 24, 2012 PIRSA:12100058
Quantum Gravity
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 University of Southern Denmark
- Martin Reuter Johannes Gutenberg University Mainz
October 24, 2012 PIRSA:12100104
Quantum Gravity
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
Cosmological Constant
- Ivan Arraut Osaka City University
- Stephon Alexander Brown University
- Alejandro Satz
- Maïté Dupuis Perimeter Institute for Theoretical Physics
- Antonino Marciano Fudan University - Physics Department
October 23, 2012 PIRSA:12100126
Cosmology
Dark Matter and Dark Energy as a Possible Manifestation of a Fundamental Scale
If we take the idea of the Planck length as a fundamental (minimum) scale and if additionally we impose the Cosmological Constant ($Lambda$) as and infrared (IR) cut-off parameter. Then it is possible to demonstrate that Dark Matter effects can emerge as a consequence of an IR-UV mix effect. This opens the possibility of unifying the Dark Energy and Dark matter effects in a single approach.

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Geometric Operators in Loop Quantum Gravity with a Cosmological Constant
Loop quantum gravity is a candidate to describe the quantum gravity regime with zero cosmological constant. One of its key results is that geometric operators such as area angle volume are quantized. Not much is known when the cosmological constant is not zero. It is usually believed that to introduce this parameter in the game we need to use quantum groups. However due to the complicated algebraic structure inherent to quantum groups the geometric operators are not yet properly defined (except the area operator). I will discuss how the use of tensor operators can circumvent the difficulties and allow to construct a natural set of observables. In particular I will construct the natural geometric observables such as angle or volume and discuss some of their implications.

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Interplay Between Cosmological Constant and DSR Scale
I offer brief remarks on several ways in which the cosmological constant could provide a clue toward quantum gravity. I then focus on how DSR-relativistic theories can be made compatible with spacetime expansion (possibly cosmological-constant-governed spacetime expansion), and how this interplay could manifest itself in data.

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Quantum Gravity RG Flow: A Cosmological Limit Cycle
I will discuss evidence for the existence of a limit cycle in the renormalization group for quantum gravity which is visible in a minisuperspace approximation. The emergence of the limit cycle can be studied through a tuning parameter representing the number of dimensions in which fluctuations of the conformal factor are suppressed. At the critical value of the tuning parameter all RG trajectories reaching the UV fixed point have an extended semiclassical regime with a small positive cosmological constant providing a possible model for a viable cosmology without fine-tuning.
Quantum Gravity Effects in Black Holes and Gravitational Waves
- Giovanni Amelino-Camelia Sapienza Università di Roma - Dipartimento di Fisica
- David Mattingly University of New Hampshire
- Nicolas Yunes University of Illinois System
- Avery Broderick University of Waterloo
October 23, 2012 PIRSA:12100094
Quantum Gravity
Quantum-gravity effects as noise for gravity-wave detectors
I discuss a mechanism that can allow Planck scale effects to manifest themselves as a source of lof-frequency noise for interferometers. The mechanism requires a discrete formulation of dynamics at the Planck scale.
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Dancing in the Dark: Images of Quantum Black Holes
There have recently been a number of rather surprising suggestions that the quantum nature of black holes is manifested on macroscopic scales. This raises the question of just what the image of such an object should look like. The answer is more than simply academic; with the advent of the Event Horizon Telescope (EHT), a millimetre-wave very long baseline array, it is now possible to probe a handful of supermassive black holes with angular resolutions sufficient to image their horizons. I will discuss what we might expect to see, and how in the near future we will begin to empirically probe the existence of black hole quantum states with horizon scale curvature deviations from general relativity.
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The Irritating Persistence of Horizons
In some approaches to quantum gravity Lorentz invariance is modified. Without Lorentz invariance one can theoretically see behind the usual Killing horizon of a black hole if, for example, one allowed for superluminal propagation. This in turn raises the possibility that one could in principle probe the singularity and the quantum gravity regime. We discuss how Lorentz violating black hole solutions in Einstein-aether theory unfortunately possess another causal boundary behind the Killing horizon that is impenetrable to any superluminal mode. We also detail progress in determining the laws of black hole mechanics and the radiation spectrum from these so-called "universal horizons". Our results suggest that even if superluminal dispersion at high frequencies did exist in nature, singularities and their associated quantum gravity resolutions may very well remain locked behind horizons.
Searching for Quantum Gravity with the IceCube Neutrino Observatory

John Kelley University of Wisconsin–Madison
October 23, 2012 PIRSA:12100093
Quantum Gravity
The IceCube Neutrino Observatory is a cubic-kilometer-scale neutrino detector built into the ice sheet at the geographic South Pole. Completed in December 2010, the detector consists of an array of photomultiplier tubes deployed along 86 cables ("strings") at depths of 1450 to 2450 m, as well as the IceTop air shower array of surface Cherenkov tanks. IceCube is detecting atmospheric neutrinos of energies above approximately 100 GeV at a rate of ~6 per hour, and is currently searching for extraterrestrial neutrinos from cosmic ray accelerators. A measurement of the atmospheric neutrino spectrum can be used to search for possible phenomenological signatures of quantum gravity (QG), such as violations of Lorentz invariance or quantum decoherence, and I present limits we have set on these phenomena in the neutrino sector. To extend the search for QG to much higher energies and cosmological baselines, we require an extraterrestrial neutrino source. In this context, I report on the status of our searches for neutrinos from gamma-ray bursts and from cosmic-ray interactions with the microwave background ("cosmogenic" neutrinos).
Quantum Gravity Effects in the (Early and Late) Universe
- Stephon Alexander Brown University
- Daniel Sudarsky Universidad Nacional Autónoma De Mexico (UNAM)
- Daniel Litim University of Sussex
- Robert Brandenberger McGill University - Department of Physics
October 23, 2012 PIRSA:12100090
Quantum Gravity
Quantum Gravity at the origin of seeds of cosmic structure?
This meeting shows a our impatience for uncovering at long last any signal of unknown physics that might have a quantum gravitational origin. I will argue that the transition from a homogenous and isotropic state characterizing the mid-early parts of inflation ( i.e. the regime after sufficient e- folds of inflation have elapsed so that all traces of the pre-inflationary state are erased), to those eras, where the primordial inhomogeneities have appears might hold ins testing clues about the nature of quantum gravity

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Quantum gravity and cosmology
In the light of upcoming high-precision data from the Planck mission and possible trans-Planckian signatures encoded in eg the microwave background radiation, and in view of possible large-distance modifications of gravity and the accelearted expansion of the universe
The highest-energy particles of the Universe as viewed by the Pierre Auger Observatory

Markus Risse University of Siegen

October 23, 2012 PIRSA:12100089

One century after the seminal balloon flights of Victor Hess, the Pierre Auger Observatory aims at unveiling some of the mysteries of the highest-energy cosmic rays: what are their sources? Is there an end to the spectrum? What kind of particles are they? Are there signatures of new physics or of a violation of fundamental laws of physics? The Auger Observatory measures cosmic rays with energies of 10^20 eV or more by observing the giant air showers created when the particles hit the atmosphere. Located in Argentina, two complementary detector systems are used: an array of 1600 water-Cherenkov detectors distributed over 3000 sqkm, and fluorescence telescopes which monitor the atmosphere above the array in clear nights. Since 2005, data of unprecedented quantity and quality could be taken. In the talk, the observation principles, successes and limitations are described. Current, partly surprising results are presented. Data interpretations related to the search for violation of Lorentz invariance are mentioned.

Title	Speaker(s)	Date	Talk Type	Info
Effective field theory framework in QG	Xavier Calmet, Roberto Percacci, Astrid Eichhorn, Martin Reuter	2012-10-25	Conference	View details
Experimental tests of CPT symmetry	Antonio Di Domenico	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 search for quantum gravity - the hard facts	Hugo Beauchemin	2012-10-25	Conference	View details
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
Astrophysical Searches for Quantum Gravity Signals	Jonathan Granot	2012-10-24	Scientific Series	View details
Dynamical Dimensional Reduction	Dejan Stojkovic, Astrid Eichhorn, Martin Reuter	2012-10-24	Conference	View details
Cosmological Constant	Ivan Arraut, Stephon Alexander, Alejandro Satz, Maïté Dupuis, Antonino Marciano	2012-10-23	Conference	View details
Quantum Gravity Effects in Black Holes and Gravitational Waves	Giovanni Amelino-Camelia, David Mattingly, Nicolas Yunes, Avery Broderick	2012-10-23	Conference	View details
Searching for Quantum Gravity with the IceCube Neutrino Observatory	John Kelley	2012-10-23	Conference	View details
Quantum Gravity Effects in the (Early and Late) Universe	Stephon Alexander, Daniel Sudarsky, Daniel Litim, Robert Brandenberger	2012-10-23	Conference	View details
The highest-energy particles of the Universe as viewed by the Pierre Auger Observatory	Markus Risse	2012-10-23	Conference	View details

Experimental Search for Quantum Gravity 2012

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