Stochastic gravitational-wave background from axion-monodromy oscillons in string theory during preheating

Sang, Yu; Huang, Qing-Guo

doi:10.1103/physrevd.100.063516

Cited by 38 publications

(26 citation statements)

References 38 publications

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“…Oscillon production Oscillons are long-lived compact objects (Gleiser 1994) that can be formed in the early Universe in a variety of post-inflationary scenarios which involve a preheating-like phase (Amin and Shirokoff 2010;Amin et al , 2012Zhou et al 2013;Amin 2013;Lozanov and Amin 2014;Antusch et al 2017Antusch et al , 2018aLozanov and Amin 2018;Amin et al 2018;Antusch et al 2019;Sang and Huang 2019;Lozanov and Amin 2019;Fodor 2019;Hiramatsu et al 2021). Their dynamics is a possible source of GW production.…”

Section: (P)reheatingmentioning

confidence: 99%

Challenges and opportunities of gravitational-wave searches at MHz to GHz frequencies

et al. 2021

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The first direct measurement of gravitational waves by the LIGO and Virgo collaborations has opened up new avenues to explore our Universe. This white paper outlines the challenges and gains expected in gravitational-wave searches at frequencies above the LIGO/Virgo band, with a particular focus on Ultra High-Frequency Gravitational Waves (UHF-GWs), covering the MHz to GHz range. The absence of known astrophysical sources in this frequency range provides a unique opportunity to discover physics beyond the Standard Model operating both in the early and late Universe, and we highlight some of the most promising gravitational sources. We review several detector concepts that have been proposed to take up this challenge, and compare their expected sensitivity with the signal strength predicted in various models. This report is the summary of the workshop “Challenges and opportunities of high-frequency gravitational wave detection” held at ICTP Trieste, Italy in October 2019, that set up the stage for the recently launched Ultra-High-Frequency Gravitational Wave (UHF-GW) initiative.

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Section: (P)reheatingmentioning

confidence: 99%

Challenges and opportunities of gravitational-wave searches at MHz to GHz frequencies

et al. 2021

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“…Nucleosynthesis also provides strong constraints on the QCD axion, even in the absence of a primordial magnetic field [148]. The interplay between solitons and electromagnetic fields can affect the rate of energy transfer and equation of state during reheating, as well as gravitational wave production, and spectral distortions during the early universe [90,126,127,[149][150][151][152][153][154].…”

Section: Early Universementioning

confidence: 99%

Dipole radiation and beyond from axion stars in electromagnetic fields

Amin

Long

Mou

et al. 2021

J. High Energ. Phys.

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We investigate the production of photons from coherently oscillating, spatially localized clumps of axionic fields (oscillons and axion stars) in the presence of external electromagnetic fields. We delineate different qualitative behaviour of the photon luminosity in terms of an effective dimensionless coupling parameter constructed out of the axion-photon coupling, and field amplitude, oscillation frequency and radius of the axion star. For small values of this dimensionless coupling, we provide a general analytic formula for the dipole radiation field and the photon luminosity per solid angle, including a strong dependence on the radius of the configuration. For moderate to large coupling, we report on a non-monotonic behavior of the luminosity with the coupling strength in the presence of external magnetic fields. After an initial rise in luminosity with the coupling strength, we see a suppression (by an order of magnitude or more compared to the dipole radiation approximation) at moderately large coupling. At sufficiently large coupling, we find a transition to a regime of exponential growth of the luminosity due to parametric resonance. We carry out 3+1 dimensional lattice simulations of axion electrodynamics, at small and large coupling, including non-perturbative effects of parametric resonance as well as backreaction effects when necessary. We also discuss medium (plasma) effects that lead to resonant axion to photon conversion, relevance of the coherence of the soliton, and implications of our results in astrophysical and cosmological settings.

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“…A lot of studies on gravitational waves emitted during the formation of oscillons can be found in the recent literature [29][30][31][32][33][34][35][36][37][38]. In this paper, we try to address the following question: How much do the properties of gravitational waves emitted from the formation of oscillons, such as the shape and the amplitude of the power spectrum, depend on the potential of a source scalar field.…”

Section: Jhep03(2021)021mentioning

confidence: 99%

Gravitational wave spectra from oscillon formation after inflation

Hiramatsu

Sfakianakis

Yamaguchi

2021

J. High Energ. Phys.

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We systematically investigate the preheating behavior of single field inflation with an oscillon-supporting potential. We compute both the properties of the emitted gravitational waves as well as the number density and characteristics of the produced oscillons. By performing numerical simulations for a variety of potential types, we divide the analyzed potentials in two families, each of them containing potentials with varying large- or small-field dependence. We find that the shape of the spectrum and the amplitude of emitted gravitational waves have a universal feature with the peak around the physical wavenumber k/a ∼ m at the inflaton oscillation starting period, irrespective of the exact potential shape. This can be used as a smoking-gun for deducing the existence of a violent preheating phase and possible oscillon formation after inflation. Despite this apparent universality, we also find differences in the shape of the spectrum of emitted gravitational waves between the two families of potentials, leading to discriminating features between them. In particular, all potentials show the emergence of a two-peak structure in the gravitational wave spectrum, arising at the time of oscillon formation. However, potentials that exhibit efficient parametric resonance tend to smear out this structure and by the end of the simulation the two-peak structure is replaced by one broad peak in the GW spectrum. We further compute the number density and properties of the produced oscillons for each potential choice, finding differences in the number density and size distribution of stable oscillons and transient overdensities. We also perform a linear fluctuation analysis and use the corresponding Floquet charts to relate the results of our simulations to the structure of parametric resonance for the various potential types. We find that the growth rate of the scalar perturbations and the associated oscillon formation time are sensitive to the small-field shape of a potential while the macroscopic physical properties of oscillons such as the total number depend on the large-field shape of a potential.

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Stochastic gravitational-wave background from axion-monodromy oscillons in string theory during preheating

Cited by 38 publications

References 38 publications

Challenges and opportunities of gravitational-wave searches at MHz to GHz frequencies

Challenges and opportunities of gravitational-wave searches at MHz to GHz frequencies

Dipole radiation and beyond from axion stars in electromagnetic fields

Gravitational wave spectra from oscillon formation after inflation

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