680,319 research outputs found
Effective superpotentials for B-branes in Landau-Ginzburg models
We compute the partition function for the topological Landau-Ginzburg B-model
on the disk. This is done by treating the worldsheet superpotential
perturbatively. We argue that this partition function as a function of bulk and
boundary perturbations may be identified with the effective D-brane
superpotential in the target spacetime. We point out the relationship of this
approach to matrix factorizations. Using these methods, we prove a conjecture
for the effective superpotential of Herbst, Lazaroiu and Lerche for the A-type
minimal models. We also consider the Landau-Ginzburg theory of the cubic torus
where we show that the effective superpotential, given by the partition
function, is consistent with the one obtained by summing up disk instantons in
the mirror A-model. This is done by explicitly constructing the open-string
mirror map.Comment: 57p, 7 figs, harvma
Radiative Symmetry Breaking in Brane Models
We propose a way to generate the electroweak symmetry breaking radiatively in
non-supersymmetric type I models with string scale in the TeV region. By
identifying the Higgs field with a tree-level massless open string state, we
find that a negative squared mass term can be generated at one loop. It is
finite, computable and typically a loop factor smaller than the string scale,
that acts as an ultraviolet cutoff in the effective field theory. When the
Higgs open string has both ends confined on our world brane, its mass is
predicted to be around 120 GeV, i.e. that of the lightest Higgs in the minimal
supersymmetric model for large and . Moreover, the string
scale turns out to be one to two orders of magnitude higher than the weak
scale. We also discuss possible effects of higher order string threshold
corrections that might increase the string scale and the Higgs mass.Comment: 16 pages, Latex2e, 2 eps figures. Some comments on the large
(longitudinal) radius limit of the mass term at the origin are developed, and
new references adde
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