Axion landscape cosmology

Bachlechner, Thomas C.; Eckerle, Kate; Janssen, Oliver; Kleban, Matthew

doi:10.1088/1475-7516/2019/09/062

Cited by 19 publications

(19 citation statements)

References 62 publications

(166 reference statements)

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“…6 It has certain generic couplings to the standard model, allowing the possibility of experimental detection (see below). More general examples-namely, axion-like-particles which have similar couplings to the standard model but do not contribute to the resolution of the strong CP problem-arise naturally in string theory as the Kaluza-Klein zero modes of higher form fields when the extra dimensions are compactified (Green et al 1988, Svrcek & Witten 2006, Arvanitaki et al 2010, Dine 2016, Halverson et al 2017, Bachlechner et al 2019.…”

Section: Particle Physics Motivationsmentioning

confidence: 99%

“…Most of them would be too massive to be a suitable dark matter candidate. But if one of them is light enough to be dark matter, perhaps there maybe more (Arvanitaki et al 2010, Bachlechner et al 2019, Luu et al 2020)? And if these light axions are coupled, how is the relic abundance computation modified?…”

Section: Experimental Detection Of Axionsmentioning

confidence: 99%

“…For recent reviews, see Graham et al (2015), Marsh (2016), Sikivie (2020). String theory also predicts a large number of axion-like-particles (ALP), one or some of which could be dark matter (Svrcek & Witten 2006, Arvanitaki et al 2010, Halverson et al 2017, Bachlechner et al 2019. At the extreme end of the spectrum is the possibility of an ALP with mass around 10 −22 − 10 −20 eV, with a relic abundance that naturally matches the observed dark matter density (see Section 2).…”

Section: Introductionmentioning

confidence: 97%

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Wave Dark Matter

Hui

2021

Preprint

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We review the physics and phenomenology of wave dark matter: a bosonic dark matter candidate lighter than about 30 eV. Such particles have a de Broglie wavelength exceeding the average inter-particle separation in a galaxy like the Milky Way, thus well described as a set of classical waves. We outline the particle physics motivations for them, including the QCD axion as well as ultra-light axion-like-particles such as fuzzy dark matter. The wave nature of the dark matter implies a rich phenomenology:• Wave interference gives rise to order unity density fluctuations on de Broglie scale in halos. One manifestation is vortices where the density vanishes and around which the velocity circulates. There is one vortex ring per de Broglie volume on average. • For sufficiently low masses, soliton condensation occurs at centers of halos. The soliton oscillates and random walks, another manifestation of wave interference. The halo and subhalo abundance is expected to be suppressed at small masses, but the precise prediction from numerical wave simulations remains to be determined. • For ultra-light ∼ 10 −22 eV dark matter, the wave interference substructures can be probed by tidal streams/gravitational lensing. The signal can be distinguished from that due to subhalos by the dependence on stream orbital radius/image separation. • Axion detection experiments are sensitive to interference substructures for wave dark matter that is moderately light. The stochastic nature of the waves affects the interpretation of experimental constraints and motivates the measurement of correlation functions.Current constraints and open questions, covering detection experiments and cosmological/galactic/black-hole observations, are discussed.

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Section: Particle Physics Motivationsmentioning

confidence: 99%

Section: Experimental Detection Of Axionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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Wave Dark Matter

Hui

2021

Preprint

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“…In fact, the flux compactification of the higher-dimensional space in the string theory predicts a large number of axions and gauged dark sectors in the low-energy effective field theory. Inflation may occur in the axion field space, the so-called axion landscape [43][44][45][46][47][48]. For instance, the reheating could occur via the decay into gauge fields.…”

Section: Case Of Multiple Dark Radiation Componentsmentioning

confidence: 99%

Anthropic bound on dark radiation and its implications for reheating

Takahashi

Yamada

2019

J. Cosmol. Astropart. Phys.

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We derive an anthropic bound on the extra neutrino species, ∆N eff , based on the observation that a positive ∆N eff suppresses the growth of matter fluctuations due to the prolonged radiation dominated era, which reduces the fraction of matter that collapses into galaxies, hence, the number of observers. We vary ∆N eff and the positive cosmological constant while fixing the other cosmological parameters. We then show that the probability of finding ourselves in a universe satisfying the current bound is of order a few percents for a flat prior distribution. If ∆N eff is found to be close to the current upper bound or the value suggested by the H 0 tension, the anthropic explanation is not very unlikely. On the other hand, if the upper bound on ∆N eff is significantly improved by future observations, such simple anthropic consideration does not explain the small value of ∆N eff . We also study simple models where dark radiation consists of relativistic particles produced by heavy scalar decays, and show that the prior probability distribution sensitively depends on the number of the particle species.

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“…The isocurvature projection S IJ W IJ /σ, identified by the dynamics above as the large scale adiabatic source term, is related to the contraction of the variables Q I with respect to the turn-rate α I often used in the multifield literature. Different notions of a turn-rate have been considered and the formal definitions that are in use are not all equivalent [43,44,45,46,47,48,49,50,51,52,53].…”

Section: Multifield Inflationmentioning

confidence: 99%

Modular inflation at higher levelN

Lynker

Schimmrigk

2019

J. Cosmol. Astropart. Phys.

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We introduce the framework of modular inflation with level structure, generalizing the level one theory considered previously to higher levels. We analyze the modular structure of CMB observables in this framework and show that the nontrivial geometry of the target space suffices to ensure the almost holomorphic modularity of the relevant parameters. We further introduce a concrete class of models based on hauptmodul functions that provide generators of the corresponding inflationary potentials at level N > 1. The phenomenology of this class of models provides targets for ground-based CMB experiments in the immediate future. In the framework of our models we also discuss the status of the quantum gravity conjectures that have been formulated in the context of the swampland.

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Axion landscape cosmology

Cited by 19 publications

References 62 publications

Wave Dark Matter

Wave Dark Matter

Anthropic bound on dark radiation and its implications for reheating

Modular inflation at higher levelN

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