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Abstract
| Despite the important 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. In the first part of my lectures (Sects. 1–6), I discuss the main motivations and directions for physics beyond the Standard Model of elementary particles and I give a short introduction on perturbative string theory. This theory introduces a new physical constant, the string length, under which a new fundamental structure appears, changing drastically the 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 be accounted for by the existence of large internal dimensions, in the submillimeter region, and transverse to a braneworld where our observed universe is confined. In the second part of my lectures (Sects. 7–11), I describe the main properties of this scenario and its implications for new gravitational phenomena that can be observed at both particle colliders, and in non-accelerator experiments searching for new short-range forces. |