Gravitational production of vector dark matter

• Main Authors: Aqeel Ahmed, Bohdan Grzadkowski, Anna Socha
• Format: Article
• Language: English
• Published: SpringerOpen 2020-08-01
• Series: Journal of High Energy Physics
• Subjects: Beyond Standard Model; Cosmology of Theories beyond the SM
• Online Access: http://link.springer.com/article/10.1007/JHEP08(2020)059

Abstract A model of vector dark matter that communicates with the Standard Model only through gravitational interactions has been investigated. It has been shown in detail how does the canonical quantization of the vector field in varying FLRW geometry implies a tachyonic enhancement of some of its momentum modes. Approximate solutions of the mode equation have been found and verified against exact numerical ones. De Sitter geometry has been assumed during inflation while after inflation a non-standard cosmological era of reheating with a generic equation of state has been adopted which is followed by the radiation-dominated universe. It has been shown that the spectrum of dark vectors produced gravitationally is centered around a characteristic comoving momentum k ⋆ that is determined in terms of the mass of the vector m X , the Hubble parameter during in- flation H I, the equation of state parameter w and the efficiency of reheating γ. Regions in the parameter space consistent with the observed dark matter relic abundance have been determined, justifying the gravitational production as a viable mechanism for vector dark matter. The results obtained in this paper are applicable within various possible models of inflation/reheating with non-standard cosmology parametrized effectively by the corresponding equation of state and efficiency of reheating.