Stochastic gravitational wave background from global cosmic strings

Chang, Chia-Feng; Cui, Yanou

doi:10.1016/j.dark.2020.100604

Cited by 69 publications

(82 citation statements)

References 41 publications

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“…Detailed realization of these initial conditions and phenomenological consequences for both QCD axion and general ALPs are worth further investigation (an example is given in Appendix B). Meanwhile, a caveat for the scenario of postinflationary PQ breaking is that, as in conventional misalignment, topological defects' contribution to Ω a may dominate over the misalignment contribution and is worth revisiting to advance and complete our understanding of the axion production mechanism [14,17,20,45,46]. Note added.-Recently, Ref.…”

Section: Discussionmentioning

confidence: 99%

New perspectives on axion misalignment mechanism

Chang

Cui

2020

Phys. Rev. D

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A zero initial velocity of the axion field is assumed in the conventional misalignment mechanism. We propose an alternative scenario where the initial velocity is nonzero, which may arise from an explicit breaking of the Peccei-Quinn (PQ) symmetry in the early Universe. We demonstrate that, depending on the specifics of the initial velocity and the time order of the PQ symmetry breaking vs inflation, this new scenario can either enhance or suppress the axion relic abundance relative to the conventional prediction. As a result, new viable parameter regions for axion dark matter may open up.

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Section: Discussionmentioning

confidence: 99%

New perspectives on axion misalignment mechanism

Chang

Cui

2020

Phys. Rev. D

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“…The energy density and spectrum of gravitational waves from a string network have been studied extensively in the literature [109][110][111] (see [112] for more details). Future gravitational wave detectors can probe an axion decay constant as small as ∼ 10 15 GeV at intermediate frequencies (LISA) and ∼ 10 14 GeV at low frequencies (SKA) [113]. The string-domain wall network can produce gravitational waves as it redshifts as well as when domain walls collide or annihilate.…”

Section: Gravitational and Gravitational Wave Signaturesmentioning

confidence: 99%

A CMB Millikan experiment with cosmic axiverse strings

Agrawal

Hook

Huang

2020

J. High Energ. Phys.

111

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We study axion strings of hyperlight axions coupled to photons. Hyperlight axions — axions lighter than Hubble at recombination — are a generic prediction of the string axiverse. These axions strings produce a distinct quantized polarization rotation of CMB photons which is $$ \mathcal{O} $$ O (αem). As the CMB light passes many strings, this polarization rotation converts E-modes to B-modes and adds up like a random walk. Using numerical simulations we show that the expected size of the final result is well within the reach of current and future CMB experiments through the measurement of correlations of CMB B-modes with E- and T-modes. The quantized polarization rotation angle is topological in nature and can be seen as a geometric phase. Its value depends only on the anomaly coefficient and is independent of other details such as the axion decay constant. Measurement of the anomaly coefficient by measuring this rotation will provide information about the UV theory, such as the quantization of electric charge and the value of the fundamental unit of charge. The presence of axion strings in the universe relies only on a phase transition in the early universe after inflation, after which the string network rapidly approaches an attractor scaling solution. If there are additional stable topological objects such as domain walls, axions as heavy as 10−15 eV would be accessible. The existence of these strings could also be probed by measuring the relative polarization rotation angle between different images in gravitationally lensed quasar systems.

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“…Most distinguishable feature of GW emission from cosmic string is prediction of a strong signal across a wide range of frequency which has triggered a growing interest in this JHEP05(2021)211 field [76][77][78][79][80][81][82][83][84][85][86]. This also includes recent studies to probe GUT [87,88], high scale leptogenesis [89], low scale leptogenesis [90].…”

Section: Introductionmentioning

confidence: 99%

Gravitational wave complementarity and impact of NANOGrav data on gravitational leptogenesis

Samanta

Datta

2021

J. High Energ. Phys.

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In seesaw mechanism, if right handed (RH) neutrino masses are generated dynamically by a gauged U(1) symmetry breaking, a stochastic gravitational wave background (SGWB) sourced by a cosmic string network could be a potential probe of leptogenesis. We show that the leptogenesis mechanism that facilitates the dominant production of lepton asymmetry via the quantum effects of right-handed neutrinos in gravitational background, can be probed by GW detectors as well as next-generation neutrinoless double beta decay (0νββ) experiments in a complementary way. We infer that for a successful leptogenesis, an exclusion limit on f − ΩGWh2 plane would correspond to an exclusion on the |mββ| − m1 plane as well. We consider a normal light neutrino mass ordering and discuss how recent NANOGrav pulsar timing data (if interpreted as GW signal) e.g., at 95% CL, would correlate with the potential discovery or null signal in 0νββ decay experiments.

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Stochastic gravitational wave background from global cosmic strings

Cited by 69 publications

References 41 publications

New perspectives on axion misalignment mechanism

New perspectives on axion misalignment mechanism

A CMB Millikan experiment with cosmic axiverse strings

Gravitational wave complementarity and impact of NANOGrav data on gravitational leptogenesis

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