Carroll has worked on a number of areas of theoretical cosmology, field theory and gravitation theory. His research papers include models of, and experimental constraints on, violations of [[Lorentz covariance|Lorentz invariance]]; the appearance of [[closed timelike curve]]s in general relativity; varieties of [[topological defect]]s in field theory; and cosmological dynamics of [[Kaluza–Klein theory|extra spacetime dimensions]]. In recent years he has written extensively on models of [[dark energy]] and its interactions with ordinary matter and [[dark matter]], as well as modifications of [[general relativity]] in cosmology.
Carroll has also worked on the [[arrow of time]] problem. He and Jennifer Chen posit that the [[Big Bang]] is not a unique occurrence as a result of all of the matter and energy in the universe originating in a singularity at the beginning of time, but rather one of many [[cosmic inflation]] events resulting from [[quantum fluctuation]]s of [[vacuum energy]] in a cold [[Dede Sitter space]]. They claim that the universe is infinitely old, but never reaches [[thermodynamic equilibrium]] as entropy increases continuously without limit due to the decreasing matter and energy density attributable to recurrent cosmic inflation. They assert that the universe is "statistically time-symmetric" insofar as it contains equal progressions of time "both forward and backward".<ref>Sean M. Carroll, Jennifer Chen, [https://arxiv.org/abs/hep-th/0410270 "Spontaneous Inflation and the Origin of the Arrow of Time"]</ref><ref>Adam Frank, [http://discovermagazine.com/2008/apr/25-3-theories-that-might-blow-up-the-big-bang/article_view?b_start:int=1&-C= "3 Theories That Might Blow Up the Big Bang"], Discover, April 2008, pp. 57–58</ref><ref>{{Cite news |first=Harold |last=Henderson |url=http://www.chicagoreader.com/pdf/050812/050812_scientists.pdf |title=The Cosmic Jiggle |publisher=[[Chicago Reader]] |date=August 12, 2005 |page=14}}</ref> Some of his work has been on violations of fundamental symmetries, the physics of dark energy, modifications of general relativity, and the arrow of time. Recently he started focusing on issues at the foundations of cosmology, statistical mechanics, quantum mechanics, and complexity.
[[File:Sean Carroll on Computer.jpg|220px|right|thumb]]
