Beyond Einstein’s Gravity

Abstract

Despite the impotant experimental success of General Relativity, there are several theoretical reasons indicating that gravitational phenomena may change radically from the predictions of Einstein’s theory at very short distances. A main motivation comes from studies of unifying all fundamental forces in the framework of a consistent quantum theory, called string theory. This theory introduces a new physical constant, the string length, under which a new elementary structure shows up, changing drastically all physical laws of nature. In particular, lowering the string scale in the TeV region provides a theoretical framework for solving the so-called mass hierarchy problem: the apparent weakness of gravity can then be accounted by the existence of large internal dimensions, in the submillimeter tegion, and transverse to a braneworld where our obserbed universe is confined. I review the main properties of this scenario and its implications for new travitational phenomena that can be obserbed at both particle colliders, and in non-accelerator experiments searching for new short range forces at submillimeter distaces. I also discuss the warped metric case and possible localization of gravity in the presence of infinite size extra dimensions that cal modify Newton’s law at cosmoligical distance scales.