EAPSI: Computer simulations of dark matter with an altered gravitational attraction

Croker Kevin A, Honolulu HI

Investigators

Abstract

Physicists and astronomers have conclusively determined that a large percent of the matter within our universe is dark and of unknown composition. While computer simulations which model this dark matter over billions of years produce a universe in agreement with observation at sizes larger than galaxies, disagreement with data remains at the size of individual galaxies. Recent extensions to Einstein's description of gravity have produced a new type of dark matter which agrees with data at the size of individual galaxies. Through supercomputer simulations, in collaboration with Dr. Naoki Yoshida jointly at University of Tokyo and Kavli Institute on the Physics and Mathematics of the Universe (IPMU) in Japan, this study will investigate whether this form of dark matter can also produce a universe in agreement with data at sizes larger than galaxies. This study has the potential to resolve a long-standing disagreement between astronomers and astrophysicists, and could point toward more fruitful extensions to Einstein's gravity. N-body simulation of point-like dark matter agrees well with the galactic power spectrum as inferred from comprehensive sky surveys. Yet, at the scale of a single galaxy, N-body simulations predict densities that diverge toward galactic centers, while observational evidence strongly suggests constant densities. There have emerged extensions to Einstein gravity that predict a dark matter candidate with Newtonian gravitational interactions at large separation but which diminish linearly to zero at small separation. The N-body code GADGET-2 will be augmented to permit distinct gravitational interactions between particles, with focus on deviations from point-mass behavior as predicted by recent models featuring multiple metric tensors. The effect of these deviations on large-scale structure will be compared against existing sky surveys. Research outcomes will either lessen tension between large-scale and small-scale dark matter observations, or exclude these specific models. This NSF EAPSI award is funded in collaboration with the Japan Society for the Promotion of Science.