Sarben Sarkar: Towards theory constraints on ultralight dark matter from quantum gravity

The conjecture by Mavromatos and Sarkar that a PT-symmetric phase plays a role in understanding singular renormalisation group (RG) flows for a Chern-Simons (CS) gauge theory of axions, has been reexamined and significantly improved. We have used the more complete Wetterich equation, which includes gravitational couplings in a systematic way from the start, to understand the emergence of this phase. The singular structure of the RG flows has persisted on including gravitational-couplings, thereby offering further support to the conjecture that PT -symmetric phases of (repulsive) gravity characterise string-effective CS gravitational theories, where the axion is the massless string-model independent axion, which can also play a role of a totally-antisymmetric torsion degree of freedom. This has suggested a novel interpretation of the currently observed acceleration of the expansion of the Universe in terms of such a phase at large (cosmological) scales.

The talk will be based on: 1) Phys.Rev.D 110 (2024) 4, 045004 • e-Print: 2402.14513 [hep-th] and 2) e-Print: 2512.23376 [gr-qc]