Possible evidence of QCD axion stars in HSC and OGLE microlensing events

Sugiyama, Sunao; Takada, Masahiro; Kusenko, Alexander

doi:10.48550/arxiv.2108.03063

Cited by 3 publications

(10 citation statements)

References 38 publications

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“…1 shows the 68% (red shaded region) and 95% (pink shaded region) credible regions obtained in Ref. [26] to explain the single microlensing event reported by Subaru HSC observation. Taking α = 1 in Eq.…”

Section: Introductionmentioning

confidence: 53%

“…3). As additional information, we have added the pink (red) band which refers to the axion star masses within the credible region at the 95%(68%) confidence to explain the single microlensing event in Subaru HSC data [26].…”

Section: Pre-inflationary Pq Symmetry Breaking Scenariomentioning

confidence: 99%

“…A rich phenomenology is associated with these compact objects ranging from parametric resonance of photons [20][21][22] and explosion in relativistic axions [23,24] to axion-photon conversion in neutron star magnetospheres [25]. In addition to these indirect searches, QCD axion stars could potentially be discovered by gravitational microlensing events as has been recently suggested in the literature [26].…”

Section: Introductionmentioning

confidence: 99%

“…Assuming QCD axion stars behave as point-like lens, authors in Ref. [26] claim that such astrophysical objects could explain the single microlensing candidate reported by the Subaru HSC. The corresponding contour for the credible region at the 95% of confidence includes axion stars with masses around [4 × 10 −10 − 10 −5 M ] representing a fraction of the dark matter f > ∼ 4 × 10 −6 .…”

Section: Introductionmentioning

confidence: 99%

“…1 in Ref. [26]. We have added the mass regime for the maximum axion star mass according to the allowed mass range for the dark matter QCD axion.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Can QCD Axion Stars explain Subaru HSC microlensing?

Schiappacasse,

Yanagida

2021

Preprint

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A non-negligible fraction of the QCD axion dark matter may form gravitationally bound Bose Einstein condensates, which are commonly known as axion stars or axion clumps. Such astrophysical objects have been recently proposed as the cause for the single candidate event reported by Subaru HSC microlensing search in the Andromeda galaxy. Depending on the breaking scale of the Peccei-Quinn symmetry and the details of the dark matter scenario, QCD axion clumps may form via gravitational condensation during radiation domination, in the dense core of axion miniclusters, or within axion minihalos around primordial black holes. We analyze all these scenarios and conclude that the microlensing candidate detected by the Subaru HSC survey is likely not caused by QCD axion stars.

show abstract

Section: Introductionmentioning

confidence: 53%

Section: Pre-inflationary Pq Symmetry Breaking Scenariomentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…1 in Ref. [26]. We have added the mass regime for the maximum axion star mass according to the allowed mass range for the dark matter QCD axion.…”

Section: Introductionmentioning

confidence: 99%

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Can QCD Axion Stars explain Subaru HSC microlensing?

Schiappacasse,

Yanagida

2021

Preprint

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QCD Axion Kinetic Misalignment without Prejudice

et al. 2022

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The axion field, the angular direction of the complex scalar field associated with the spontaneous symmetry breaking of the Peccei–Quinn (PQ) symmetry, could have originated with initial non-zero velocity. The presence of a non-zero angular velocity resulting from additional terms in the potential that explicitly break the PQ symmetry has important phenomenological consequences such as a modification of the axion mass with respect to the conventional PQ framework or an explanation for the observed matter-antimatter asymmetry. We elaborate further on the consequences of the “kinetic misalignment” mechanism, assuming that axions form the entirety of the dark matter abundance. The kinetic misalignment mechanism possesses a weak limit in which the axion field starts to oscillate at the same temperature as in the conventional PQ framework, and a strong limit corresponding to large initial velocities which effectively delay the onset of oscillations. Following a UV-agnostic approach, we show how this scenario impacts the formation of axion miniclusters, and we sketch the details of these substructures along with potential detecting signatures.

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Primordial black holes as a dark matter candidate in theories with supersymmetry and inflation

Flores¹,

Kusenko²

2021

Preprint

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We show that supersymmetry and inflation, in a broad class of models, generically lead to formation of primordial black holes (PBHs) that can account for dark matter. Supersymmetry predicts a number of scalar fields that develop a coherent condensate along the flat directions of the potential at the end of inflation. The subsequent evolution of the condensate involves perturbative decay, as well as fragmentation into Q-balls, which can interact by some long-range forces mediated by the scalar fields. The attractive scalar long-range interactions between Q-balls facilitates the growth of Q-balls until their ultimate collapse to black holes. For a flat direction lifted by supersymmetry breaking at the scale Λ ∼ 100 TeV, the black hole masses are of the order of (4π) 3/2 (M 3 Planck /Λ 2 ) ∼ 10 23 g, in the allowed range for dark matter. Similar potentials with a lower scale Λ (not necessarily associated with supersymmetry) can result in a population of primordial black holes with larger masses, which can explain some recently reported microlensing events.

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Possible evidence of QCD axion stars in HSC and OGLE microlensing events

Cited by 3 publications

References 38 publications

Can QCD Axion Stars explain Subaru HSC microlensing?

Can QCD Axion Stars explain Subaru HSC microlensing?

QCD Axion Kinetic Misalignment without Prejudice

Primordial black holes as a dark matter candidate in theories with supersymmetry and inflation

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