Prethermalization Production of Dark Matter

At the end of inflation, the inflaton field decays into an initially nonthermal population of relativistic particles which eventually thermalize. We consider the production of dark matter from this relativistic plasma, focusing on the prethermal phase. We find that for a production cross section $\sigma(E)\sim E^n$ with $n> 2$, the present dark matter abundance is produced during the prethermal phase of its progenitors. For $n\le 2$, entropy production during reheating makes the nonthermal contribution to the present dark matter abundance subdominant compared to that produced thermally. As specific examples, we verify that the nonthermal contribution is irrelevant for gravitino production in low scale supersymmetric models ($n=0$) and is dominant for gravitino production in high scale supersymmetry models ($n=6$).Comment: 12 pages, 4 figure

Science in the Third Dimension of R&D

We study a Schumpeterian model of long-run growth with endogenous fertility and with three interacting dimensions of innovation. Scientific research is the fundamental dimension of innovation that creates new technological knowledge. This is allocated over new working prototypes in the horizontal dimension. New firms finance scientific research by obtaining the property rights of new working prototypes, and existing firms invest in developing the blueprint mode of working prototypes into the more productive modes of production in the vertical dimension. Balanced growth in the standards of living is fully endogenous without scale effects, and a new parameter, i.e., the elasticity of scientific knowledge with respect to existing collective scientific knowledge, nonlinearly accelerates long-run growth. With exogenous population growth, the model generates a semi-endogenous result due to the endogenously determined bound on technological opportunity.Science; Technology; Blueprints; R&D; Endogenous Fertility

From Wires to Cosmology

We provide a statistical framework for characterizing stochastic particle production in the early universe via a precise correspondence to current conduction in wires with impurities. Our approach is particularly useful when the microphysics is uncertain and the dynamics are complex, but only coarse-grained information is of interest. We study scenarios with multiple interacting fields and derive the evolution of the particle occupation numbers from a Fokker-Planck equation. At late times, the typical occupation numbers grow exponentially which is the analog of Anderson localization for disordered wires. Some statistical features of the occupation numbers show hints of universality in the limit of a large number of interactions and/or a large number of fields. For test cases, excellent agreement is found between our analytic results and numerical simulations.Comment: v3: minor changes and references added; matches published version in JCA