Geometry, physics, and phenomenology of the Randall-Sundrum model
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ometry, Physics, and Phenomenology of the Randall–Sundrum Model E. E. Boos, V. E. Bunichev, I. P. Volobuev, and M. N. Smolyakov Skobeltsyn Institute of Nuclear Physics, Moscow, 119991 Russia Abstract—This review is devoted to a discussion of the geometry and physics of the Randall–Sundrum model with two branes. The main focus is on its phenomenologically acceptable stabilized version. For this model, the second variation Lagrangian is constructed, its gauge invariance is studied, corresponding equations of motion are derived and decoupled, and physical degrees of freedom are explicitly isolated. For the stabilized model, possible phenomenological manifestations in experiments at the Tevatron and LHC are discussed for cases in which the centerofmass energy is below or above the production threshold of the first Kaluza– Klein tensor resonance. DOI: 10.1134/S1063779612010017
INTRODUCTION The hypothesis of the existence of extra spacetime dimensions has been discussed in theoretical physics for nearly a hundred years; no wonder it has consider ably been modified throughout this time span [1, 2]. In the original version of this approach—in the socalled Kaluza–Klein theories—macroscopic unobservabil ity of extra dimensions was explained by their tiny size being of order of the Planck scale [3, 4]. What is more, in effective fourdimensional theory only zero modes, that is, the fields independent of the coordinates of those extra dimensions, turned out to be observable. About a quarter of a century ago, a new scenario for the KaluzaKlein theories was proposed, based on the idea of the fields localized on a domain wall, which admits the existence of large and even infinitely large extra dimensions unobservable at low energies [5]. In the limit of an infinitely thin domain wall a new object appears in the theory—a membrane, or brane, that is, a threedimensional surface in multidimen sional space with the Standard Model (SM) fields localized on it; the models of this type were dubbed “brane world” models. These latter brane world models with extra space dimensions and various fields, either living in the bulk of multidimensional space or localized on the branes, open up quite a number of intriguing opportunities to solve or take a fresh look at various problems of ele mentary particle physics and cosmology. These prob lems include the hierarchy problem of gravitational interaction, proton stability, baryo and leptogenesis, tiny masses of neutrinos and their strong mixing, dark matter and energy, and others. It turned out that such models arise in superstring theories as well [6, 7], and that they can naturally feature supersymmetry and other possible symmetries. Besides, brane world mod els lead to interesting predictions for the experiments
(to be) conducted at the TeVscale colliders—Teva tron, LHC, and ILC. In braneworld scenarios, the energy scales, appearing in the model and usually fixed by the gravi tational interaction, play a crucial role. This is a con sequence of the fact that it is gravity that g
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