Analysis of Birefringence and Dispersion Effects from Spacetime-Symmetry Breaking in Gravitational Waves

In this work, we review the effective field theory framework to search for Lorentz and CPT symmetry breaking during the propagation of gravitational waves. The article is written so as to bridge the gap between the theory of spacetime-symmetry breaking and the analysis of gravitational-wave signals detected by ground-based interferometers. The primary physical effects beyond General Relativity that we explore here are dispersion and birefringence of gravitational waves. We discuss their implementation in the open-source LIGO-Virgo algorithm library suite, and we discuss the statistical method used to perform a Bayesian inference of the posterior probability of the coefficients for symmetry-breaking. We present preliminary results of this work in the form of simulations of modified gravitational waveforms, together with sensitivity studies of the measurements of the coefficients for Lorentz and CPT violation. The findings show the high potential of gravitational wave sources across the sky to sensitively probe for these signals of new physics.

Penning-Trap Searches for Lorentz and CPT Violation

An overview of recent progress on testing Lorentz and CPT symmetry using Penning traps is presented. The theory of quantum electrodynamics with Lorentz-violating operators of mass dimensions up to six is summarized. Dominant shifts in the cyclotron and anomaly frequencies of the confined particles and antiparticles due to Lorentz and CPT violation are derived. Existing results of the comparisons of charge-to-mass ratios and magnetic moments involving protons, antiprotons, electrons, and positrons are used to constrain various coefficients for Lorentz violation.

Testing CPT violation, entanglement and gravitational interactions in particle mixing with trapped ions

By analyzing the analogies between the effective system of N spins described by the Ising Hamiltonian and the phenomenon of the self-gravity in mixed particle systems, we show that cooled ions held in a segmented ion trap and exposed to a magnetic field gradient can simulate the proposed mechanism of mutual interaction in mixed neutrino system. We show that with trapped ions one can reproduce the expected corrections to the flavor transitions and the CPT violation induced by gravity on flavor fields, which may have played an important role in the early stages of the universe. The results presented are experimentally testable.

Tests of CPT invariance in gravitational waves with LIGO-Virgo catalog GWTC-1

A discovery of gravitational waves from binary black holes raises a possibility that measurements of them can provide strict tests of CPT invariance in gravitational waves. When CPT violation exists, if any, gravitational waves with different circular polarizations could gain a slight difference in propagating speeds. Hence, the birefringence of gravitational waves is induced and there should be a rotation of plus and cross modes. For CPT-violating dispersion relation $${\omega ^{2}=k^{2}}$$ ω 2 = k 2 $${\pm 2\zeta k^{3}}$$ ± 2 ζ k 3 , where a sign $${\pm }$$ ± denotes different circular polarizations, we find no substantial deviations from CPT invariance in gravitational waves by analyzing a compilation of ten signals of binary black holes in the LIGO-Virgo catalog GWTC-1. We obtain a strict constraint on the CPT-violating parameter, i.e., $$\zeta =0.14^{+0.22}_{-0.31}\times 10^{-15}\,\text {m}$$ ζ = 0 . 14 - 0.31 + 0.22 × 10 - 15 m , which is around two orders of magnitude better than the existing one. Therefore, this study stands for the up-to-date strictest tests of CPT invariance in gravitational waves.

Revealing neutrino nature and CPT violation with decoherence effects

We study decoherence effects on mixing among three generations of neutrinos. We show that in presence of a non-diagonal dissipation matrix, both Dirac and Majorana neutrinos can violate the CPT symmetry and the oscillation formulae depend on the parametrization of the mixing matrix. We reveal the CP violation in the transitions preserving the flavor, for a certain form of the dissipator. In particular, for such dissipators, the CP violation affects all the transitions in the case of Majorana neutrinos, unlike Dirac neutrinos which still preserve the CP symmetry in one of the transitions flavor preserving. The precise form of the dissipation matrix is not known a-priori as it depends on the nature of the phenomenon that originates it. However, our theoretical results show that decoherence effects, if exist for neutrinos, could allow to reveal the neutrino nature and to test fundamental symmetries.