Dark Matter Relics and the Expansion Rate in Scalar-Tensor Theories

Abstract

We study the impact of a modified expansion rate on the dark matter relic abundance in a class of scalar-tensor theories. The scalar-tensor theories we consider are motivated from string theory constructions, which have conformal as well as disformally coupled matter to the scalar. We investigate the effects of such a conformal coupling to the dark matter relic abundance for a wide range of initial conditions, masses and cross-sections. We find that exploiting all possible initial conditions, the annihilation cross-section required to satisfy the dark matter content can differ from the thermal average cross-section in the standard case. We also study the expansion rate in the disformal case and find that physically relevant solutions require a nontrivial relation between the conformal and disformal functions. We study the effects of the disformal coupling in an explicit example where the disformal function is quadratic.

v2: 31 pages, 13 figures. Added more examples and figures in section 3 and appendix, small changes elsewhere. Accepted for publication in JCAP

References in corpus (5)

• Starting the Universe: Stable Violation of the Null Energy Condition and Non-standard Cosmologies
• Searching for Dark Matter Annihilation in Recently Discovered Milky Way Satellites with Fermi-LAT
• Dilaton and off-shell (non-critical string) effects in Boltzmann equation for species abundances
• Dark matter relic density in Gauss-Bonnet braneworld cosmology
• Asymmetric dark matter in braneworld cosmology

Cited by in corpus (19)

• The landscape of QCD axion models
• Probing the pre-BBN universe with gravitational waves from cosmic strings
• Ultraviolet Freeze-in and Non-Standard Cosmologies
• Primordial Gravitational Waves in Nonstandard Cosmologies
• Primordial Gravitational Wave Signals in Modified Cosmologies
• A sub-GeV dark matter model
• On Inflationary Scale, Reheating Scale and Pre-BBN Cosmology with Scalar Fields
• TeV Scale Leptogenesis with Dark Matter in Non-standard Cosmology
• Vector Boson Fusion in the Inert Doublet Model
• Establishing the Dark Matter Relic Density in an Era of Particle Decays
• A cosmological pathway to testable leptogenesis
• Primordial Black Hole Formation in Non-Standard Post-Inflationary Epochs
• D-brane Disformal Coupling and Thermal Dark Matter
• Post-inflationary Scalar Tensor Cosmology and Inflationary Parameters
• Dark matter relic density from conformally or disformally coupled light scalars
• WIMPy Leptogenesis in Non-Standard Cosmologies
• The rise of the primordial tensor spectrum from an early scalar-tensor epoch
• Constraints on primordial black holes for nonstandard cosmologies
• Dark Matter Is The New BBN