Dark matter production via a non-minimal coupling to gravity

Abstract

We study postinflationary scalar dark matter production via its non-minimal coupling to gravity. During the inflaton oscillation epoch, dark matter is produced resonantly for a sufficiently large non-minimal coupling ξ ≳ 5. We find that backreaction on the curvature and rescattering effects typically become important for the values of ξ above 30, which invalidate simple estimates of the production efficiency. At large couplings, the dark matter yield becomes almost independent of ξ, signifying approximate quasi-equilibrium in the inflaton-dark matter system. Although the analysis gets complicated by the presence of apparent negative energy in the Jordan frame, this behaviour can be regularized by introducing mild dark matter self-interaction. Using lattice simulations, we delineate parameter space leading to the correct dark matter relic abundance.

Effects of fragmentation on post-inflationary reheating

“…Notably, even if λ ≪ 1, as required by the measured amplitude of the primordial curvature fluctuation, the growth of inhomogeneities can be amplified by the accumulation of the (bosonic) field fluctuations over the oscillation of the inflaton. This parametric self-resonance persists despite the expansion of the universe, leading then to the exponential growth of non-zero momentum modes until they backreact into the homogeneous condensate, fragmenting it [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55]. The resulting inhomogeneous field distribution can become localized in transient structures, lasting for a few oscillations, or into long-lived, soliton-like structures called oscillons [41,42,47,[56][57][58].…”

Gravitational freeze-in dark matter from Higgs preheating

“…Neglecting L non−G int , the authors of refs. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] have studied the gravitational freeze-in DM production via inflaton annihilation φφ → h µν → χχ, either with the minimal or non-minimal coupling…”

Reheating after inflaton fragmentation

“…The quartic inflaton system has been extensively studied in the past by means of lattice methods, see e.g. [21,[30][31][32][33][34][35]37]. For our analysis we use the publicly available code CosmoLattice [60,61].…”

“…Preheating in non-quadratic minima has also been studied extensively [21,[25][26][27][28][29][30][31][32][33][34][35][36][37]. Notably, the presence of inflaton self-interactions, even if small, can accumulate over several oscillations and source the resonant growth of non-zero momenta inflaton modes, eventually backreacting with the homogeneous component.…”