scholarly journals Higher-order Lorentz-invariance violation, quantum gravity and fine-tuning

2015 ◽  
Vol 746 ◽  
pp. 190-193 ◽  
Author(s):  
Carlos M. Reyes ◽  
Sebastian Ossandon ◽  
Camilo Reyes
Keyword(s):  
Quantum Gravity ◽  
Lorentz Invariance ◽  
Higher Order ◽  
Fine Tuning ◽  
Invariance Violation ◽  
Lorentz Invariance Violation

scholarly journals Constraints on Lorentz Invariance Violation from Optical Polarimetry of Astrophysical Objects

Symmetry ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 596 ◽  
Author(s):  
Fabian Kislat
Keyword(s):  
Standard Model ◽  
Quantum Gravity ◽  
Linear Polarization ◽  
Lorentz Invariance ◽  
Polarization Angle ◽  
Standard Model Extension ◽  
Polarization Measurements ◽  
Invariance Violation ◽  
The Standard Model ◽  
Lorentz Invariance Violation

Theories of quantum gravity suggest that Lorentz invariance, the fundamental symmetry of the Theory of Relativity, may be broken at the Planck energy scale. While any deviation from conventional Physics must be minuscule in particular at attainable energies, this hypothesis motivates ever more sensitive tests of Lorentz symmetry. In the photon sector, astrophysical observations, in particular polarization measurements, are a very powerful tool because tiny deviations from Lorentz invariance will accumulate as photons propagate over cosmological distances. The Standard-Model Extension (SME) provides a theoretical framework in the form of an effective field theory that describes low-energy effects due to a more fundamental quantum gravity theory by adding additional terms to the Standard Model Lagrangian. These terms can be ordered by the mass dimension d of the corresponding operator and lead to a wavelength, polarization, and direction dependent phase velocity of light. Lorentz invariance violation leads to an energy-dependent change of the Stokes vector as photons propagate, which manifests itself as a rotation of the polarization angle in measurements of linear polarization. In this paper, we analyze optical polarization measurements from 63 Active Galactic Nuclei (AGN) and Gamma-ray Bursts (GRBs) to search for Lorentz violating signals. We use both spectropolarimetric measurements, which directly constrain the change of linear polarization angle, as well as broadband spectrally integrated measurements. In the latter, Lorentz invariance violation manifests itself by reducing the observed net polarization fraction. Any observation of non-vanishing linear polarization thus leads to constraints on the magnitude of Lorentz violating effects. We derive the first set limits on each of the 10 individual birefringent coefficients of the minimal SME with d = 4 , with 95% confidence limits on the order of 10−34 on the dimensionless coefficients.

scholarly journals Probing Quantum Gravity with Imaging Atmospheric Cherenkov Telescopes

Universe ◽  
2021 ◽  
Vol 7 (9) ◽  
pp. 345
Author(s):  
Tomislav Terzić ◽  
Daniel Kerszberg ◽  
Jelena Strišković
Keyword(s):  
Quantum Gravity ◽  
Historical Development ◽  
Lorentz Invariance ◽  
High Energy ◽  
Cherenkov Telescopes ◽  
Analysis Methods ◽  
Invariance Violation ◽  
Lorentz Invariance Violation ◽  
Comparison Of The Results ◽  
Energy Dependent

High energy photons from astrophysical sources are unique probes for some predictions of candidate theories of Quantum Gravity (QG). In particular, Imaging atmospheric Cherenkov telescope (IACTs) are instruments optimised for astronomical observations in the energy range spanning from a few tens of GeV to ∼100 TeV, which makes them excellent instruments to search for effects of QG. In this article, we will review QG effects which can be tested with IACTs, most notably the Lorentz invariance violation (LIV) and its consequences. It is often represented and modelled with photon dispersion relation modified by introducing energy-dependent terms. We will describe the analysis methods employed in the different studies, allowing for careful discussion and comparison of the results obtained with IACTs for more than two decades. Loosely following historical development of the field, we will observe how the analysis methods were refined and improved over time, and analyse why some studies were more sensitive than others. Finally, we will discuss the future of the field, presenting ideas for improving the analysis sensitivity and directions in which the research could develop.

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