Microlensing and Gravitational Backreaction for Superstring Loops

Cornell University, Ithaca NY

Investigators

Abstract

This award funds the research of Prof. David Chernoff at Cornell University. Substantial theoretical and observational evidence supports the occurrence of inflation at very early times, a brief interval of extremely rapid expansion of the Universe shortly after birth. The mechanism is a profound problem for cosmology and fundamental physics. String theory, the best-developed tool to explore this epoch, suggests that today our Universe may contain relics of that early, energetic phase. The relics are loops of string stretched from microscopic scales to macroscopic scales by the rapid expansion. The proposed research investigates the physics of string loops and possibilities for detecting them. Astronomical detection would be a revolutionary development for string theory and cosmology. Such a discovery would provide a direct glimpse of otherwise inaccessible elements of the underlying physical theory. It would help elucidate the mechanism for inflation while extending our study of the universe to the earliest moments of the big bang itself. At the very beginning, the universe is believed to have grown exponentially in size via the mechanism of inflation. The almost scale-invariant density perturbation spectrum predicted by inflation is strongly supported by recent observational data. Subsequent evolution, the traditional purview of big bang cosmology, can be accurately modeled with tried-and-true physics. However, the precise inflationary mechanism remains a profound problem for cosmology and for fundamental physics. Intellectual Merit: String theory, the best-developed tool to explore this epoch, suggests the inevitable birth and survival of one-dimensional structures of cosmological sizes, namely, cosmic superstrings. Long, horizon-crossing strings fragment to give loops which fall into growing matter perturbations. The local density of these fossil remnant loops within the galaxy is enhanced over the universe's mean density of loops by many orders of magnitude and numerous loops exist within the galaxy. The PI will investigate how these relics can be sought by optical lensing of background stars and studied in detail through gravitational wave emission. These objects will provide some of the best experimental means to learn about string theory and the birth of our universe. Broader Impacts: As part of this proposal (1) The PI will help train postdoctoral fellows, graduate students and undergraduates in theoretical physics and cosmology. (2) The PI is committed to publicizing the big questions of theoretical physics and cosmology that motivate the work. The PI will speak in local science museums and help bring the research to life for general audiences.