Some open questions in axion theory

Agrawal, Prateek; Berghaus, Kim V.; Fan, JiJi; Hook, Anson; Marques-Tavares, Gustavo; Rudelius, Tom

doi:10.48550/arxiv.2203.08026

Cited by 2 publications

(2 citation statements)

References 161 publications

(185 reference statements)

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“…However, whenever the theory is endowed with additional couplings, the mere existence of said states may give important information about the composition of the allowed (sub)lattice of states that the theory must support. In particular, if the theory is endowed with some 'θ-terms', whereby an axion couples to topological terms of the form F ∧ F , the Witten effect [26] (see also [30][31][32] for later reviews) predicts the existence of an infinitely populated lattice of states, generated by a seed state.…”

Section: The Witten Effect and An Infinitely Populated Charge Latticementioning

confidence: 99%

Global symmetry-breaking and generalized theta-terms in Type IIB EFTs

Grimm,

Lanza,

van Vuren

2023

J. High Energ. Phys.

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A longstanding conjecture states that global symmetries should be absent in quantum gravity. By investigating large classes of Type IIB four-dimensional $$ \mathcal{N} $$ N = 2 effective field theories, we enlist the potential generalized global symmetries that could be present and explore how they are avoided. Crucial ingredients that arise in such effective field theories are generalized θ-terms. These introduce non-linear couplings between axion fields and topological terms quadratic in the gauge field strengths which break a large subset of the global symmetries. Additional residual global symmetries may further be broken by assuming the existence of some charged states. However, we illustrate that the presence of generalized θ-terms leads to a generalized Witten effect, which implies that the spectrum of charged states is constituted by an infinitely populated lattice. We further show that such a lattice is generated by the action of the monodromy transformation that characterizes the moduli space boundary near which the effective theory is defined.

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Section: The Witten Effect and An Infinitely Populated Charge Latticementioning

confidence: 99%

Global symmetry-breaking and generalized theta-terms in Type IIB EFTs

Grimm,

Lanza,

van Vuren

2023

J. High Energ. Phys.

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“…In the past, such effects have been largely explored [21][22][23] in other contexts, such as warm inflaton [24][25][26][27][28][29][30][31][32][33][34][35][36], late-time quintessence [37], leptogenesis [38,39], electroweak baryogenesis [40] and early dark energy [37,41]; see Section VI in Ref. [42] for a recent review. The present work also contributes to the larger effort in the community to explore the different possibilities for the cosmological axion evolution which open up once the assumptions of the canonical misalignment picture are relaxed or modified.…”

Section: Introductionmentioning

confidence: 99%

Axion dark matter from frictional misalignment

Papageorgiou¹,

Quílez²,

Schmitz³

2022

Preprint

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We study the impact of sphaleron-induced thermal friction on the axion dark-matter abundance due to the interaction of an axion-like particle (ALP) with a dark non-abelian gauge sector in a secluded thermal bath. Thermal friction can either enhance the axion relic density by delaying the onset of oscillations or suppress it by damping them. We derive an analytical formula for the frictional adiabatic invariant, which remains constant along the axion evolution and which allows us to compute the axion relic density in a general set-up. Even in the most minimal scenario, in which a single gauge group is responsible for both the generation of the ALP mass and the friction force, we find that the resulting dark-matter abundance from the misalignment mechanism deviates from the standard scenario for axion masses m a ≳ 100 eV. We also generalize our analysis to the case where the gauge field that induces friction and the gauge sector responsible for the ALP mass are distinct and their couplings to the axion have a large hierarchy as can be justified by means of alignment or clockwork scenarios. We find that it is easy to open up the ALP parameter space where the resulting axion abundance matches the observed dark-matter relic density both in the traditionally over-and underabundant regimes. This conclusion also holds for the QCD axion.

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Some open questions in axion theory

Cited by 2 publications

References 161 publications

Global symmetry-breaking and generalized theta-terms in Type IIB EFTs

Global symmetry-breaking and generalized theta-terms in Type IIB EFTs

Axion dark matter from frictional misalignment

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