Stochastic Dark Matter from Curvature Perturbations.

Area of Science:

• Cosmology
• Particle Physics
• Astrophysics

Background:

• The origin of dark matter remains a significant unsolved problem in cosmology.
• The standard cosmological model relies on metric perturbations generated during inflation or standard cosmology.
• These perturbations can break the symmetries of the spacetime metric.

Purpose of the Study:

• To investigate the production of dark matter from metric perturbations.
• To analyze particle production from conformally coupled fields, specifically fermions.
• To establish a connection between perturbation properties and dark matter abundance.

Main Methods:

• Calculating particle production using Bogoliubov transformations.
• Analyzing the impact of metric perturbations on conformally coupled fields.
• Deriving a formula for particle abundance based on the power spectrum of curvature perturbations.

Main Results:

• Metric perturbations enable the production of particles, even those with negligible mass.
• A closed-form formula relates dark matter abundance to the power spectrum of curvature perturbations.
• The critical dark matter abundance is achieved for masses M≳10⁶ GeV in the simplest scenarios.

Conclusions:

• Metric perturbations offer a viable mechanism for dark matter production.
• This mechanism is particularly effective when perturbation amplitudes are enhanced near the end of inflation.
• The study provides a testable prediction linking cosmological perturbations to dark matter properties.