Searches for other vacua. Part I. Bubbles in our universe

Hook, Anson; Huang, Junwu

doi:10.1007/jhep08(2019)148

Cited by 13 publications

(15 citation statements)

References 87 publications

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“…In some sense, this is a third example, following [89] and [90], where we can search for signatures related to the presence of other vacua in the landscape, albeit indirectly. In a recent example some of the authors worked on [90], a deterministic Higgstory is achieved for large Hubble rates because the electroweak minimum disappears and only the high energy minimum of the Higgs persists during inflation.…”

Section: Discussionmentioning

confidence: 99%

Maximal axion misalignment from a minimal model

Huang

Madden

Racco

et al. 2020

J. High Energ. Phys.

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The QCD axion is one of the best motivated dark matter candidates. The misalignment mechanism is well known to produce an abundance of the QCD axion consistent with dark matter for an axion decay constant of order 1012 GeV. For a smaller decay constant, the QCD axion, with Peccei-Quinn symmetry broken during inflation, makes up only a fraction of dark matter unless the axion field starts oscillating very close to the top of its potential, in a scenario called “large-misalignment”. In this scenario, QCD axion dark matter with a small axion decay constant is partially comprised of very dense structures. We present a simple dynamical model realising the large-misalignment mechanism. During inflation, the axion classically rolls down its potential approaching its minimum. After inflation, the Universe reheats to a high temperature and a modulus (real scalar field) changes the sign of its minimum dynamically, which changes the sign of the mass of a vector-like fermion charged under QCD. As a result, the minimum of the axion potential during inflation becomes the maximum of the potential after the Universe has cooled through the QCD phase transition and the axion starts oscillating. In this model, we can produce QCD axion dark matter with a decay constant as low as 6 × 109 GeV and an axion mass up to 1 meV. We also summarise the phenomenological implications of this mechanism for dark matter experiments and colliders.

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Section: Discussionmentioning

confidence: 99%

Maximal axion misalignment from a minimal model

Huang

Madden

Racco

et al. 2020

J. High Energ. Phys.

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“…We would like to note that our analysis of the physics of a light field such as the QCD-axion in systems at finite chemical potential is of general applicability, therefore of relevance for other light (below the QCD confinement scale) axion-like particles coupled to QCD degrees of freedom, e.g. [17,[36][37][38][39]. 2 We find this type of new physics well motivated and very interesting, specially in light of the excellent experimental prospects for improving our understanding of dense astrophysical objects such as NSs, as exemplified by the recent detection of gravitational waves from merger events [41].…”

Section: Jhep07(2020)221mentioning

confidence: 99%

“…Lastly, the instanton potential is minimized with respect to β at cos β = Sign [cos(3α)] . (5.38) Therefore, one finds that the axion is aligned with the η , such that 39) while the axion mass, neglecting mixing with η and normalized to its vacuum value, is given by…”

Section: Jhep07(2020)221mentioning

confidence: 99%

“…In terms of such fields, which we recall make up the finite-density background, the baryon Lagrangian is given by where we defined the dressed mass matrix Finally, we recall that at zero temperature all the states with E(p) = p 2 + m 2 ψ < µ ψ are occupied, such that 39) with g ψ counting the internal degrees of freedom, e.g. g ψ = 2 for a fermion.…”

Section: B2 Non-linear Field Basismentioning

confidence: 99%

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The QCD axion at finite density

Balkin

Serra

Springmann

et al. 2020

J. High Energ. Phys.

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We show how the properties of the QCD axion change in systems at finite baryonic density, such as neutron stars. At nuclear saturation densities, where corrections can be reliably computed, we find a mild reduction of the axion mass and up to an order of magnitude enhancement in the model-independent axion coupling to neutrons. At moderately higher densities, if realized, meson (kaon) condensation can trigger axion condensation. We also study the axion potential at asymptotically large densities, where the color-superconducting phase of QCD potentially leads to axion condensation, and the mass of the axion is generically several orders of magnitude smaller than in vacuum due to the suppressed instantons. Several phenomenological consequences of the axion being sourced by neutron stars are discussed, such as its contribution to their total mass, the presence of an axionic brane, or axion-photon conversion in the magnetosphere.

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“…A very small value of V rebounce ∼ V 0 could arise assuming that the contraction/rebounce/expansion phase triggers movement of some lighter fields φ with potentials such that vacua close by in field space have similar energies. 'Ordered' landscapes of this kind have been considered, for instance, in [31][32][33][34][35][36][37]. 2 An example of this hiccupping structure is provided by Abbott's model [31], i.e.…”

Section: Possible Hiccuping Dynamicsmentioning

confidence: 99%

Cosmological constant: Relaxation vs multiverse

Струмиа

Teresi

2019

Physics Letters B

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We consider a scalar field with a bottom-less potential, such as g 3 φ, finding that cosmologies unavoidably end up with a crunch, late enough to be compatible with observations if g < ∼ 1.2HPl . If rebounces avoid singularities, the multiverse acquires new features; in particular probabilities avoid some of the usual ambiguities. If rebounces change the vacuum energy by a small enough amount, this dynamics selects a small vacuum energy and becomes the most likely source of universes with anthropically small cosmological constant. Its probability distribution could avoid the gap by 2 orders of magnitude that seems left by standard anthropic selection.

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Searches for other vacua. Part I. Bubbles in our universe

Cited by 13 publications

References 87 publications

Maximal axion misalignment from a minimal model

Maximal axion misalignment from a minimal model

The QCD axion at finite density

Cosmological constant: Relaxation vs multiverse

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