Primordial black holes and gravitational waves in multiaxion-Chern-Simons inflation

Mavromatos, Nikolaos; Spanos, Vassilis C.; Stamou, Ioanna D.

doi:10.1103/physrevd.106.063532

Cited by 14 publications

(31 citation statements)

References 123 publications

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“…In [33] we have considered one such toy string-inspired extension of the stringy RVM model, in which we considered the effects of one more axion field, arising from compactification, a(x), with axion coupling f a , in addition to the KR axion b(x) that drove the RVM inflation. Below 2 We note that the variation of the gravitational CS anomaly terms in (5) with respect to the graviton field is non trivial, giving rise to the so-called Cotton tensor [41,42], which affects the Einstein equation:…”

Section: Enhanced Primordial Black Holes and Modified Gravitational W...mentioning

confidence: 99%

“…Then, the corresponding condensate-induced linear axion-b effective potential (cf. ( 5)) reads [33] V…”

Section: Enhanced Primordial Black Holes and Modified Gravitational W...mentioning

confidence: 99%

“…where, in the study of [33], the parameters ξ1 , f a , and the world-sheet instanton induced scales Λ 1 , Λ 2 are treated as phenomenological, with the constraint though that [33]:…”

Section: Enhanced Primordial Black Holes and Modified Gravitational W...mentioning

confidence: 99%

“…The structure of the talk is the following: in the next section 2, we discuss the potentially important rôle of (gravitational) anomalies and torsion on inducing RVM-type inflation in the string-inspired cosmological model, without the need for external inflatons. In section 3, we discuss the rôle of periodic modulations of the potential of axion fields arising from compactification in the underlying microscopic string theory model on inducing an enhanced density of primordial black holes during inflation, which in turn will affect the profile of GW during the radiation era [33], with in principle observable consequences in future interferometers like LISA [34,35]. In section 4, we explain how, in the above anomalous class of string-inspired models, one may generate a matter-antimatter asymmetry in the Universe as a consequence of torsion-induced axion backgrounds which violate spontaneously Lorentz and CPT symmetries.…”

Section: Introductionmentioning

confidence: 99%

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Anomalies, the Dark Universe and Matter-Antimatter asymmetry

Mavromatos

2023

J. Phys.: Conf. Ser.

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I review a (3+1)-dimensional, string-inspired cosmological model with gravitational anomalies (of Chern-Simons (CS) type) at early epochs, and a totally-antisymmetric torsion, dual to a massless axion-like field (“gravitational axion”), which couples to the CS term. Under appropriate conditions, primordial gravitational waves can condense, leading to a condensate of the CS anomaly term. As a consequence, one obtains inflation in this theory, of running-vacuum-model (RVM) type, without the need for external inflatons. At the end of the inflationary era, chiral fermionic matter is generated, whose gravitational anomalies cancel the primordial ones. On the other hand, chiral anomalies of gauge type, which are also generated by the chiral matter, remain present during the post-inflationary epochs and become responsible for the generation of a non-perturbative mass for the torsion-related gravitational axion, which, in this way, might play the rôle of a Dark Matter component of geometrical origin. Moreover, in this model, stringy non-perturbative effects during the RVM inflationary phase generate periodic structures for the potential of axion-like particles that arise due to compactification, and co-exist with the gravitational axions. Such periodic potential modulations may lead to an enhanced production of primordial black holes during inflation, which in turn affects the profile of the generated gravitational waves during the radiation era, with potentially observable consequences. This model also entails an unconventional mechanism for Leptogenesis, due to Lorentz-violating backgrounds of the gravitational axions that are generated during inflation, as a consequence of the anomaly condensates, and remain undiluted in the radiation era.

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Section: Enhanced Primordial Black Holes and Modified Gravitational W...mentioning

confidence: 99%

“…Then, the corresponding condensate-induced linear axion-b effective potential (cf. ( 5)) reads [33] V…”

Section: Enhanced Primordial Black Holes and Modified Gravitational W...mentioning

confidence: 99%

“…where, in the study of [33], the parameters ξ1 , f a , and the world-sheet instanton induced scales Λ 1 , Λ 2 are treated as phenomenological, with the constraint though that [33]:…”

Section: Enhanced Primordial Black Holes and Modified Gravitational W...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Anomalies, the Dark Universe and Matter-Antimatter asymmetry

Mavromatos

2023

J. Phys.: Conf. Ser.

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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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