Lorentz symmetry: Broken, intact or deformed?
APA
Sorkin, R., Hossenfelder, S., Mattingly, D., Afshordi, N., Sudarsky, D., Liberati, S., ... (2012). Lorentz symmetry: Broken, intact or deformed?. Perimeter Institute. https://pirsa.org/12100108
MLA
Sorkin, Rafael, et al. Lorentz symmetry: Broken, intact or deformed?. Perimeter Institute, Oct. 24, 2012, https://pirsa.org/12100108
BibTex
@misc{ pirsa_PIRSA:12100108, doi = {10.48660/12100108}, url = {https://pirsa.org/12100108}, author = {Sorkin, Rafael and Hossenfelder, Sabine and Mattingly, David and Afshordi, Niayesh and Sudarsky, Daniel and Liberati, Stefano and Magueijo, Joao}, keywords = {Quantum Gravity}, language = {en}, title = {Lorentz symmetry: Broken, intact or deformed?}, publisher = {Perimeter Institute}, year = {2012}, month = {oct}, note = {PIRSA:12100108 see, \url{https://pirsa.org}} }

Rafael Sorkin Perimeter Institute for Theoretical Physics

Sabine Hossenfelder LudwigMaximiliansUniversität 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
Abstract
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 Lorentzinvariance 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 HoravaLifshiftz gravity
HoravaLifshitz 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 scaleinvariant 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