Production of ultralight dark matter from inflationary spectator fields

Belfiglio A. Luongo O.
15 July 2024 American Physical Society

Physical Review D
2024 #110 Issue 2

We investigate inflationary particle production associated with a spectator ultralight scalar field, which has recently been proposed as a plausible dark matter candidate. In this framework, we select the Starobinsky potential to drive the inflationary epoch, also discussing the case of a nonminimally coupled inflaton field fueled by a quartic symmetry-breaking potential. We focus on particle production arising from spacetime perturbations, which are induced by inflaton fluctuations during the quasi-de Sitter stage of inflation. In particular, we construct the first-order Lagrangian describing interaction between inhomogeneities and the spectator field, quantifying superhorizon particle production during slow-roll. We then compare this mechanism with gravitational particle production associated with an instantaneous transition from inflation to the radiation dominated era. We show that the number of particles obtained from perturbations is typically non-negligible, and it is significantly enhanced on super-Hubble scales by the nonadiabatic inflationary expansion. Possible implications for primordial entanglement generation are also debated.

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School of Science and Technology, University of Camerino, Via Madonna delle Carceri, Camerino, 62032, Italy
Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Perugia, Perugia, 06123, Italy
SUNY Polytechnic Institute, Utica, 13502, NY, United States
INAF, Osservatorio Astronomico di Brera, Milano, 20121, Italy
Al-Farabi Kazakh National University, Al-Farabi Avenue 71, Almaty, 050040, Kazakhstan

School of Science and Technology
Istituto Nazionale di Fisica Nucleare (INFN)
SUNY Polytechnic Institute
INAF
Al-Farabi Kazakh National University

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