Finite Theories and Marginal Operators on the Brane

We show how to use D and NS fivebranes in Type IIB superstring theory to construct large classes of finite N=1 supersymmetric four dimensional field theories. In this construction, the beta functions of the theories are directly related to the bending of branes; in finite theories the branes are not bent, and vice versa. Many of these theories have multiple dimensionless couplings. A group of duality transformations acts on the space of dimensionless couplings; for a large subclass of models, this group always includes an overall SL(2,\ZZ) invariance. In addition, we find even larger classes of theories which, although not finite, also have one or more marginal operators.Comment: 32 pages, 13 figures, uses revte

Discovering the Higgs Through Highly-Displaced Vertices

We suggest that the Higgs could be discovered at the Tevatron or the LHC (perhaps at the LHCb detector) through decays with one or more substantially displaced vertices from the decay of new neutral particles. This signal may occur with a small but measurable branching fraction in the recently-described ``hidden valley'' models, hep-ph/0604261; weakly-coupled models with multiple scalars, including those of hep-ph/0511250, can also provide such signals, potentially with a much larger branching fraction. This decay channel may extend the Higgs mass reach for the Tevatron. Unusual combinations of b jets, lepton pairs and/or missing energy may accompany this signal.Comment: v2, minor improvements/clarifications, one added referenc

BPS Z(N) String Tensions, Sine Law and Casimir Scaling and Integrable Field Theories

We consider a Yang-Mills-Higgs theory with spontaneous symmetry breaking of the gauge group G -> U(1)^r -> C(G), with C(G) being the center of G. We study two vacua solutions of the theory which produce this symmetry breaking. We show that for one of these vacua, the theory in the Coulomb phase has the mass spectrum of particles and monopoles which is exactly the same as the mass spectrum of particles and solitons of two dimensional affine Toda field theory. That result holds also for N=4 Super Yang-Mills theories. On the other hand, in the Higgs phase, we show that for each of the two vacua the ratio of the tensions of the BPS Z(N) strings satisfy either the Casimir scaling or the sine law scaling for G=SU(N). These results are extended to other gauge groups: for the Casimir scaling, the ratios of the tensions are equal to the ratios of the quadratic Casimir constant of specific representations; for the sine law scaling, the tensions are proportional to the components of the left Perron-Frobenius eigenvector of Cartan matrix and the ratios of tensions are equal to the ratios of the soliton masses of affine Toda field theories.Comment: 21 pages, 10 figures. A correction on the title pag