String (gravi)photons, "dark brane photons", holography and the hypercharge portal

TL;DR

This paper investigates the mixing of graviphotons and dark brane photons with the Standard Model hypercharge within string theory and holographic frameworks, comparing string-derived couplings with effective field theory predictions.

Contribution

It provides a comprehensive analysis of photon mixing in string theory and holography, highlighting the relative suppression of string-derived couplings compared to EFT couplings.

Findings

String theory mixing terms are generally subleading compared to EFT couplings.

Holographic theories also exhibit suppressed mixing terms.

Results help clarify the expected magnitude of photon mixing in different theoretical contexts.

Abstract

The mixing of graviphotons and dark brane photons to the Standard Model hypercharge is analyzed in full generality, in weakly-coupled string theory. Both the direct mixing as well as effective terms that provide mixing after inclusion of SM corrections are estimated to lowest order. The results are compared with Effective Field Theory (EFT) couplings, originating in a hidden large-N theory coupled to the SM. The string theory mixing terms are typically subleading compared with the generic EFT couplings. The case where the hidden theory is a holographic theory is also analyzed, providing also suppressed mixing terms to the SM hypercharge.