Topological defects and nano-Hz gravitational waves in aligned axion models

Higaki, Tetsutaro; Jeong, Kwang Sik; Kitajima, Naoya; Sekiguchi, Toyokazu; Takahashi, Fuminobu

doi:10.1007/jhep08(2016)044

Cited by 41 publications

(45 citation statements)

References 93 publications

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“…To be specific, the theory of an axion with

f > M_{P}

will be understood as an effective theory, which can be obtained from a more fundamental theory of two (or more) axions with subplanckian decay constants. Following , we then proceed to construct an effective string with

f > M_{P}

out of the strings present in the more fundamental theory and examine it for potential pathologies.…”

Section: Magnetic String In An Effective Theory With F>mpmentioning

confidence: 99%

“…The task is hence to examine whether string solutions for

f > M_{P}

suffer from any pathologies. Our most promising candidates will be topological inflation and and a composite string à la .…”

Section: Introductionmentioning

confidence: 99%

“…As

f_{1, 2} < M_{P}

, the corresponding magnetic objects exist and avoid the problems mentioned above. Following , one can then identify a string solution as bound state of the strings of the original two axions connected by domain walls. This object is then checked explicitly for possible pathologies.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

What is the magnetic Weak Gravity Conjecture for axions?

Hebecker

Henkenjohann

Witkowski

2017

Fortschritte der Physik

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The electric Weak Gravity Conjecture demands that axions with large decay constant f couple to light instantons. The resulting large instantonic corrections pose problems for natural inflation. We explore an alternative argument based on the magnetic Weak Gravity Conjecture for axions, which we try to make more precise. Roughly speaking, it demands that the minimally charged string coupled to the dual 2‐form‐field exists in the effective theory. Most naively, such large‐f strings curve space too much to exist as static solutions, thus ruling out large‐f axions. More conservatively, one might allow non‐static string solutions to play the role of the required charged objects. In this case, topological inflation would save the superplanckian axion. Furthermore, a large‐f axion may appear in the low‐energy effective theory based on two subplanckian axions in the UV. The resulting effective string is a composite object built from several elementary strings and domain walls. It may or may not satisfy the magnetic Weak Gravity Conjecture depending on how strictly the latter is interpreted and on the cosmological dynamics of this composite object, which remain to be fully understood. Finally, we recall that large‐field brane inflation is naively possible in the codimension‐one case. We show how string‐theoretic back‐reaction closes this apparent loophole of large‐f (non‐periodic) pseudo‐axions.

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“…To be specific, the theory of an axion with

f > M_{P}

f > M_{P}

out of the strings present in the more fundamental theory and examine it for potential pathologies.…”

Section: Magnetic String In An Effective Theory With F>mpmentioning

confidence: 99%

“…The task is hence to examine whether string solutions for

f > M_{P}

suffer from any pathologies. Our most promising candidates will be topological inflation and and a composite string à la .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

What is the magnetic Weak Gravity Conjecture for axions?

Hebecker

Henkenjohann

Witkowski

2017

Fortschritte der Physik

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“…The formation of domain walls and the production of GWs are also predicted in the context of the aligned axion models [100][101][102], which have been built explicitly by applying the clockwork mechanism discussed in Ref. [103].…”

Section: Axion Modelsmentioning

confidence: 99%

“…Note that the magnitude of the constant term should be w 0 ∼ m 3/2 M 2 Pl in order to cancel 8 String-wall systems may eventually collapse into a single string bundle, since the vacuum may not be disconnected along the direction of the unbroken U(1). However, such a collapse is not likely to occur if N ax is large and i is sufficiently small, since in this case strings obey the scaling solution, i.e., the number of strings per horizon remains O(1), before the formation of domain walls and the size of the hybrid object, which evolves toward the bundle and contains exponentially large number of strings, is far outside the horizon [101].…”

Section: Supersymmetric Modelsmentioning

confidence: 99%

A Review of Gravitational Waves from Cosmic Domain Walls

2017

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Abstract:In this contribution, we discuss the cosmological scenario where unstable domain walls are formed in the early universe and their late-time annihilation produces a significant amount of gravitational waves. After describing cosmological constraints on long-lived domain walls, we estimate the typical amplitude and frequency of gravitational waves observed today. We also review possible extensions of the standard model of particle physics that predict the formation of unstable domain walls and can be probed by observation of relic gravitational waves. It is shown that recent results of pulser timing arrays and direct detection experiments partially exclude the relevant parameter space, and that a much wider parameter space can be covered by the next generation of gravitational wave observatories.

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What if ALP dark matter for the XENON1T excess is the inflaton

Takahashi

Yamada

Yin

2021

J. High Energ. Phys.

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The recent XENON1T excess in the electron recoil data can be explained by anomaly-free axion-like particle (ALP) dark matter with mass mϕ = 2.3 ± 0.2 keV and the decay constant $$ {f}_{\phi }/{q}_e\simeq 2\times {10}^{10}\sqrt{\Omega_{\phi }/{\Omega}_{\mathrm{DM}}} $$ f ϕ / q e ≃ 2 × 10 10 Ω ϕ / Ω DM GeV. Intriguingly, the suggested mass and decay constant are consistent with the relation, $$ {f}_{\phi}\sim {10}^3\sqrt{m_{\phi }{M}_p} $$ f ϕ ∼ 10 3 m ϕ M p , predicted in a scenario where the ALP plays the role of the inflaton. This raises a possibility that the ALP dark matter responsible for the XENON1T excess also drove inflation in the very early universe. We study implications of the XENON1T excess for the ALP inflation and thermal history of the universe after inflation. We find that the successful reheating requires the ALP couplings to heavy fermions in the standard model, which results in an instantaneous reheating and subsequent thermalization of the ALPs. Then, an entropy dilution of $$ \mathcal{O} $$ O (10) is necessary to explain the XENON1T excess, which can be achieved by decays of the right-handed neutrinos.

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Topological defects and nano-Hz gravitational waves in aligned axion models

Cited by 41 publications

References 93 publications

What is the magnetic Weak Gravity Conjecture for axions?

What is the magnetic Weak Gravity Conjecture for axions?

A Review of Gravitational Waves from Cosmic Domain Walls

What if ALP dark matter for the XENON1T excess is the inflaton

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