Speaker
Description
In this talk, I will argue that the consistency of non-perturbative $\theta$-vacua in gauge theories and gravity predicts the presence of axion-like particles (ALPs) in the particle spectrum. This prediction also necessitates additional structures in these theories. Specifically, General Relativity incorporates Eguchi-Hanson instantons, which generate gravitational $\theta$-vacua. The $S$-matrix formulation of gravity requires the elimination of these $\theta$-vacua, leading to the formulation of the Gravity-CP problem. The only viable solution to this problem is spontaneously broken supergravity, which predicts an ALP that acquires mass exclusively from gravitational $\theta$-vacua. Consequently, these particles exhibit a correlated mass with the gravitino. Their appearance is due to consistency, making them promising candidates for dark matter.
Furthermore, the electroweak sector of the Standard Model possesses its own $\theta$-vacua, which are removed via $B+L$ symmetry. I will argue that this symmetry should be realized non-linearly, leading to the emergence of a composite ultra-light particle, $\eta_w$, within the Standard Model. I will also examine the scenario where $B+L$ symmetry is explicitly broken. Using gravitational arguments, I will discuss the necessity of its exactness and/or the existence of an external ALP coupled with the aforementioned $\theta$-vacuum structure, thereby making predictions about the existence of the $\eta_w$ particle rigorous and strict.\
The talk is based on:
2406.18402 [hep-th], 2408.07535 [hep-th].
