Lorentz violation in the sky

Lorentz symmetry is fundamental in describing all known interactions and a crucial building block of the Standard Model of particle physics. However, there are good theoretical reasons to think that Lorentz symmetry may be broken at a high energy scale, or by sector which is not part of the standard model, for instance, dark matter or gravity. The Standard Model Extension (SME) [1,2] is an effective field theory which consistently includes Lorentz-violating terms so that Lorentz violation can be experimentally tested without alluding to specific theories.

As a PhD student, you will work on studying various aspects of SME phenomenology with cosmology. Possibilities include determining the SME operators for known Lorentz-violating theories of gravity beyond General Relativity, determining the effect of SME operators on cosmological observables [3], and/or using data to constrain the SME operators [4,5].

References:

[1] Lorentz-Violating Extension of the Standard Model, https://arxiv.org/abs/hep-ph/9809521
[2] Gravity, Lorentz violation, and the Standard Model, https://arxiv.org/abs/hep-th/0312310
[3] For example, Probing Lorentz-Violating electrodynamics with CMB polarization, https://arxiv.org/abs/2212.04867
[4] Lorentz violation: Motivation and new constraints, https://arxiv.org/abs/0906.0681
[5] Tests of Lorentz symmetry in the gravitational sector, https://arxiv.org/abs/1610.04682