Gravitational wave signatures of inflationary models from Primordial Black Hole dark matter

Abstract

Abstract. Primordial Black Holes (PBH) could be the cold dark matter of the universe.They could have arisen from large (order one) curvature fluctuations produced during inflation that reentered the horizon in the radiation era. At reentry, these fluctuations source gravitational waves (GW) via second order anisotropic stresses. These GW, together with those (possibly) sourced during inflation by the same mechanism responsible for the large curvature fluctuations, constitute a primordial stochastic GW background (SGWB) that unavoidably accompanies the PBH formation. We study how the amplitude and the range of frequencies of this signal depend on the statistics (Gaussian versus χ 2 ) of the primordial curvature fluctuations, and on the evolution of the PBH mass function due to accretion and merging. We then compare this signal with the sensitivity of present and future detectors, at PTA and LISA scales. We find that this SGWB will help to probe, or strongly constrain, the early universe mechanism of PBH production. The comparison between the peak mass of the PBH distribution and the peak frequency of this SGWB will provide important information on the merging and accretion evolution of the PBH mass distribution from their formation to the present era. Different assumptions on the statistics and on the PBH evolution also result in different amounts of CMB µ-distortions. Therefore the above results can be complemented by the detection (or the absence) of µ-distortions with an experiment such as PIXIE.

The exponential tail of inflationary fluctuations: consequences for primordial black holes

“…Let us mention that some inflationary models are already known to display a χsquare statistics for the curvature perturbation, such as models of axion inflation in which the gauge field sources the curvature perturbations [40], and that the implications of a χ-square distribution for the gravitational wave signature have been studied in detail in Ref. [41]. However, here, the presence of exponential tails has been found even in single-field, slow-roll inflationary scenarios.…”

“…This is for instance the case for the expansion in terms of the non-linearity parameters f NL and g NL [36]. Non-Gaussianities may therefore play a crucial role in determining the abundance of PBHs [37][38][39][40][41][42][43][44][45][46][47][48][49] and, in this work, we provide a generic, non-perturbative framework to derive the tails of the PDFs of curvature perturbations. This makes use of the stochastic-δN formalism [50][51][52][53][54][55][56][57], in which the curvature perturbations are identified with fluctuations in the local duration of inflation, that varies under the effects of quantum diffusion of the inflaton field, described as stochastic noise in the stochastic inflation formalism [9,[58][59][60].…”

Constraining axion inflation with gravitational waves from preheating

“…From the theoretical point of view, the (approximate) shift symmetry of an pseudoscalar inflaton (axion) inherently protects its potential from large corrections, ensuring the flatness required for a successful inflationary phase. The phenomenology of these models is extremely rich, with possible observable signatures including the production of sizable non-Gaussianities [50][51][52][53], observable gravitational waves [51,52,[54][55][56][57], primordial black holes [53,[58][59][60][61][62], µdistortions [55,63], primordial magnetic fields [49,[64][65][66][67][68], and the generation of the baryon asymmetry [57,[69][70][71][72]. Preheating into gauge fields via a Chern-Simons coupling was first studied within the context of chaotic inflation in Ref.…”

Analytic description of primordial black hole formation from scalar field fragmentation

“…Such primordial black holes (PBHs) can account for all or part of the dark matter (DM) (e.g. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]). PBHs can be associated with a variety of astrophysical phenomena, including the recently discovered [21][22][23] gravitational waves (e.g.…”