Abstract
In the purely gravitational dark matter scenario, the dark matter particle does not have any interaction except for gravitational one. We study the gravitational particle production of dark matter particle in such a minimal setup and show that correct amount of dark matter can be produced depending on the inflation model and the dark matter mass. In particular, we carefully evaluate the particle production rate from the transition epoch to the inflaton oscillation epoch in a realistic inflation model and point out that the gravitational particle production is efficient even if dark matter mass is much larger than the Hubble scale during inflation as long as it is smaller than the inflaton mass.
Highlights
As the inflaton mass mφ, even if it is much larger than Hinf
We study the gravitational particle production of dark matter particle in such a minimal setup and show that correct amount of dark matter can be produced depending on the inflation model and the dark matter mass
We carefully evaluate the particle production rate from the transition epoch to the inflaton oscillation epoch in a realistic inflation model and point out that the gravitational particle production is efficient even if dark matter mass is much larger than the Hubble scale during inflation as long as it is smaller than the inflaton mass
Summary
Where MP is the reduced Planck scale, R is the Ricci scalar, φ denotes the inflaton field with V (φ) being its potential and χ denotes a real scalar field. We assume that χ does not have a direct coupling to the inflaton and other standard model fields It interacts only through the metric or the gravity. Where the dot denotes the derivative with respect to the physical time t and the Hubble parameter H is given by the Friedmann equation, H2 =. For any given inflation model, we can calculate the production rate of χ through the time dependence of the scale factor a in (2.3). These equations are written in terms of the conformal time as φ + 2Hφ + a2 ∂V = 0, ∂φ (2.7)
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