Improved constraints on anisotropic birefringent Lorentz invariance and CPT violation from broadband optical polarimetry of high redshift galaxies

In Vacuo Dispersion-Like Spectral Lags in Gamma-Ray Bursts

“…[12] on dimension-four operators added to the Standard-Model lagrangian, whereas the effects we here consider would be described in field-theory in terms of dimension-five operators. However, describing photons within the SME the effects of dispersion would be combined with birefringence [13][14][15][16][17], which we here assume to be absent consistently with results obtained in frameworks alternative to the SME, such as those studied in Refs. [1,3,7] and references therein).…”

New Constraints on Lorentz Invariance Violation from Combined Linear and Circular Optical Polarimetry of Extragalactic Sources

“…In Equation ( 17), H 0 is the Hubble constant and Ω r , Ω m , Ω k , and Ω Λ are the present day fractional contributions of radiation, matter, curvature, and dark energy to the energy budget of the universe. In this study, we adopt H 0 = 67.66 km s −1 Mpc −1 = 1.4433 × 10 −33 eV, Ω m = 0.3111, Ω r = 9.182 × 10 −5 , Ω Λ = 0.6889, and Ω k = 0, following [39,49] (see [39] in particular for a discussion of the accuracy of those values in this context and the Hubble tension).…”

“…While, in principle, both CPT-even (d = 4) and CPT-odd (d = 3) contributions to the Lagrangian may exist simultaneously, it is generally preferable to begin the search for Lorentz invariance violation with the smallest number of free parameters. We will follow [12,22,32,39,40,50] and assume that the effects at a specific d dominate. In particular, we choose to focus on the d = 4 case as an even mass dimension is required for helicity coupling (for odd d, the birefringence axis is parallel to the Stokes V axis and, therefore, circular polarization of the photon is conserved).…”

“…In Equation ( 18), the dependence of Φ on the direction of arrival is determined by the particular SME configuration, which we seek to constrain by comparison with observations. Following [12,39,41], we limit the dependence to 10 linearly independent degrees of freedom (corresponding to the 10 independent components of k (4)…”

“…We developed a method to combine polarization measurements from many objects in order to individually constrain the coefficients of a given mass dimension. By applying this method to a large number of optical polarization measurements, we obtained the strongest constraints on individual coefficients to date [32,[38][39][40]. In essence, we sample the SME coefficient space and, for each set of coefficients, calculate the likelihood to make all given polarization measurements with the published uncertainties of the linear polarization values.…”