Speaker
Description
Fifth force and equivalence principle tests search for new physics by precisely measuring forces between macroscopic objects and their properties under free fall. These experiments test the interactions between macroscopic collections of atoms and molecules, and any new interactions effectively take place between these low energy degrees of freedom.
In contrast, the early Universe plasma probes these interactions at a more fundamental level.
In this talk, I will consider the case of a scalar mediating a fifth force, and show that the effects of dimensional transmutation, spontaneous symmetry breaking, and the running of the gauge couplings cause the scalar interactions to mix, leading to nearly universal dynamics at early times. Using the well-known expressions for the pressure of the Standard Model during its various epochs to compute the scalar effective potential, I will show that scalar couplings to matter larger than $\sim 10^{-6}(m_\phi/\eV)^{-1/4}$ relative to gravity produce the correct dark matter abundance, motivating new physics searches in this part of parameter space.
