String (Gravi)photons, “Dark Brane Photons”, Holography and the Hypercharge Portal

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 where the dark photons are composite. 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.

Emergent gravity from hidden sectors and TT deformations

“…• Although all operators of the hidden theory are coupled weakly at low energies to the SM, the SM quantum corrections generate O(M) masses for all of them with a few notable exceptions that are protected by symmetries: the graviton, the universal axion, [56], and exactly conserved global currents, [58].…”

“…In the context of a hidden theory coupled to the SM, we may make similar comments with global symmetries that arise in the hidden theory. In particular, in the hidden theory, when it is holographic, the global symmetries become local and may couple to the SM, as discussed in detail in [57,58]. The interesting question concerns global symmetries in the SM like B-L.…”

“…The interesting question concerns global symmetries in the SM like B-L. If it is mixed with a hidden global symmetry during the coupling of the hidden and the visible theory, as discussed in detail in [57,58] then it also becomes a local symmetry. However, we seem to have a priori the option to keep it intact and in that case it seems that it remains a global symmetry.…”

“…The exception is QCD, where due to strong coupling, the effective interactions are short range but mediated by scalars. In the presence of graviphotons, [58], emerging from the hidden theory, there are also repulsive interactions, competing with gravity and scalar interactions. Which wins depends on strengths but most importantly on the masses of the associated mediators.…”

Emergent neutrinos from heavy messengers

“…Therefore, composites of the hidden sector behave like weakly-coupled particles coupled to the SM, and those protected by symmetries remain light, providing interesting phenomenology [22,23]. It is worth mentioning the emergent "graviton" [24], the emergent axions [25], the emergent vector fields [26] graviphotons [27] and a new portal for dark matter [28]. All these fields have a compositeness scale below which they behave like fundamental particles, and above, they enter in a non-local, non-standard description.…”