Induced gravitational waves from multi-sound speed resonances during cosmological inflation

Addazi, Andrea; Capozziello, Salvatore; Gan, Qingyu

doi:10.1088/1475-7516/2022/08/051

Cited by 11 publications

(6 citation statements)

References 124 publications

(165 reference statements)

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“…These long-wavelength modes, in particular, may have been generated by quantum fluctuations which grew during inflation and the reheating eras, in a similar way to those which led to density fluctuations and thus to the large scale structure. Their effect on gravitational waves (GWs) and on the CMB has been studied in several papers, see, for example [19][20][21]. In this debate, a particular role has been recently assumed by Teleparallel Gravity (TG) and its extensions which seem to fix several cosmological issues ranging from inflation to dark energy, from primordial Big Bang nucleosynthesis to cosmological perturbations, up to the H 0 tension [22][23][24][25][26][27][28].…”

Section: Jcap10(2022)020mentioning

confidence: 99%

The amplification of cosmological magnetic fields in extended f(T,B) teleparallel gravity

Capozziello¹,

Carleo²,

Lambiase³

2022

J. Cosmol. Astropart. Phys.

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Observations indicate that intergalactic magnetic fields have amplitudes of the order of ∼ 10-6 G and are uniform on scales of ∼ 10 kpc. Despite their wide presence in the Universe, their origin remains an open issue. Even by invoking a dynamo mechanism or a compression effect for magnetic field amplification, the existence of seed fields before galaxy formation is still problematic. General Relativity predicts an adiabatic decrease of the magnetic field evolving as |B| ∝ 1/a 2, where a is the scale factor of the Universe. It results in very small primordial fields, unless the conformal symmetry of the electromagnetic sector is broken. In this paper, we study the possibility that a natural mechanism for the amplification of primordial magnetic field can be related to extended teleparallel gravity f(T,B) models, where T is the torsion scalar, and B the boundary term. In particular, we consider a non-minimal coupling with gravity in view to break conformal symmetry in a teleparallel background, investigating, in particular, the role of boundary term B, which can be consider as a further scalar field. We find that, after solving exactly the f(T,B) field equations both in inflation and reheating eras, a non-adiabatic behavior of the magnetic field is always possible, and a strong amplification appears in the reheating epoch. We also compute the ratio r = ρB /ργ between the magnetic energy density and the cosmic microwave energy density during inflation, in order to explain the present value r ≃ 1, showing that, in the slow-roll approximation, power-law teleparallel theories with Bn have effects indistinguishable from metric theories Rn where R is the Ricci curvature scalar.

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Section: Jcap10(2022)020mentioning

confidence: 99%

The amplification of cosmological magnetic fields in extended f(T,B) teleparallel gravity

Capozziello¹,

Carleo²,

Lambiase³

2022

J. Cosmol. Astropart. Phys.

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“…Throughout the past few decades, massive inflationary models have been used to study PBH production, with the goal of enhancing small-scale primordial curvature disturbances while maintaining the scale-invariant spectrum seen in the cosmic microwave background (CMB). To the best of our knowledge, PBH formation mechanisms fall under the following broad groups: extra contributions from other fields to curvature perturbations in multi-field models [5][6][7][8][9][10][11][12][13][14][15][16][17][18], the non-attractor evolutions lead to the amplification of perturbations (e.g., in the presence of ultra-slow-roll (USR) phases) [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36], parametric resonance or tachyonic instability of curvature perturbations [37][38][39][40][41][42][43][44][45], the non-Gaussianity of distribution probability [46][47][48]…”

Section: Introductionmentioning

confidence: 99%

Sudden braking and turning with a two-field potential bump: primordial black hole formation

Chen

2023

J. Cosmol. Astropart. Phys.

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We investigate the amplification of curvature perturbations in a two-field inflation model featuring a Gaussian potential bump. When the inflaton encounters a potential bump along the inflationary trajectory, its rolling speed is generally reduced, potentially causing a violation of the slow-roll condition. Consequently, the original decaying modes of comoving curvature perturbations during the slow-roll phase start growing, and lead to enhanced small-scale density perturbations which can produce amounts of primordial black holes (PBHs) and associated scalar-induced gravitational waves. In addition, inflaton also undergoes sudden turnings at the encounter of the Gaussian potential bump, which is insignificant to the overall curvature power spectrum due to the short duration of these turns. Our paper offers a simple example of the extension of a bump-like potential for PBH formation in a single-field inflation to a two-field case, which helps alleviate the fine-tuning of initial conditions to some extent.

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“…GW signals typically remain unaffected during their propagation, and thus they can provide valuable information about the very early stages of the universe. For instance, different inflationary models can lead to different predictions for the GWB spectrum [40][41][42][43][44][45][46][47][48][49][50][51][52], and thus GWB can be used as a probe of this primordial universe epoch. Since GWB can provide us with important astrophysical and cosmological probes, it is crucial to understand its composition and properties [53][54][55][56][57][58][59][60][61][62][63].…”

Section: Introductionmentioning

confidence: 99%

Stochastic gravitational wave background from the collisions of dark matter halos

Qi¹,

Ren²,

Zhao³

et al. 2023

Preprint

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We investigate for the first time the effect of the dark matter (DM) halos collisions, namely collisions of galaxies and galaxy clusters, through gravitational bremsstrahlung, on the stochastic gravitational wave background. We first calculate the gravitational wave signal of a single collision event, assuming point masses and linear perturbation theory. Then we proceed to the calculation of the energy spectrum of the collective effect of all dark matter collisions in the Universe. Concerning the DM halo collision rate we show that it is given by the product of the number density of DM halos, which is calculated by the extended Press-Schechter (EPS) theory, with the collision rate of a single DM halo, which is given by simulation results, with a function of the linear growth rate of matter density through cosmological evolution. Hence, integrating over all mass and distance ranges, we finally extract the spectrum of the stochastic gravitational wave background created by DM halos collisions. As we show, the resulting contribution to the stochastic gravitational wave background is of the order of h c ≈ 10 −30 in the pulsar timing array (PTA) band of f ≈ 10 −9 Hz, much smaller than other GW sources, such as super-massive black-hole mergers. However, in very low frequency band, it is larger. With current observational sensitivity it cannot be detected, nevertheless it may be accessible by PTA in the future, where techniques of distinguishing signal overlap should be used in order to isolate it and use it for cosmological studies.

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Induced gravitational waves from multi-sound speed resonances during cosmological inflation

Cited by 11 publications

References 124 publications

The amplification of cosmological magnetic fields in extended f(T,B) teleparallel gravity

The amplification of cosmological magnetic fields in extended f(T,B) teleparallel gravity

Sudden braking and turning with a two-field potential bump: primordial black hole formation

Stochastic gravitational wave background from the collisions of dark matter halos

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