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Andreas Karch

Publications and source records attributed to Andreas Karch.

162 records · Page 9Linked to original sources
arXiv1999

Branes and Supersymmetry Breaking in Three Dimensional Gauge Theories

It is shown that supersymmetry is spontaneously broken in certain three-dimensional supersymmetric gauge theories, by using the s-rule in their string theory realization as brane configurations. In particular, supersymmetry is broken in N=3 supersymmetric Yang-Mills-Chern-Simons theory with gauge group SU(n) and CS coefficient k, as well as in its N=2 and N=1 deformations, when n>|k|. In addition, supersymmetry is broken in the N=1 mass deformation of N=2 supersymmetric Yang-Mills theory with gauge group SU(n) and one matter multiplet when n>1. In the latter case the breaking is induced by an instanton-generated repulsive potential.

hep-th↗
arXiv1999

Mirror Symmetries for Brane Configurations and Branes at Singularities

We study local mirror symmetry on non-compact Calabi-Yau manifolds (conifold type of singularities) in the presence of D3 brane probes. Using an intermediate brane setup of NS 5-branes `probed' by D4 resp. D5 branes, we can explicitly T-dualize three isometry directions to relate a non-compact Calabi-Yau manifold to its local mirror. The intermediate brane setup is the one that is best suited to read off the gauge theory on the probe. Both intervals and boxes of NS 5-branes appear as brane setups. Going from one to the other is equivalent to performing a conifold transition in the dual geometry. One result of our investigation is that the brane box rules as they have been discussed so far should be generalized. Our new rules do not need diagonal fields localized at the intersection. The old rules reappear on baryonic branches of the theory.

hep-th↗
arXiv1999

New N=1 Superconformal Field Theories and their Supergravity Description

In this note we construct a new class of superconformal field theories as mass deformed N=4 super Yang-Mills theories. We will argue that these theories correspond to the fixed points which were recently found by Khavaev, Pilch and Warner studying the deformations of the dual IIB string theory on AdS_5\times S^5.

hep-th↗
arXiv1998

Field Theory Dynamics from Branes in String Theory

I review certain aspects of Hanany-Witten setups and other approaches used to embed (and solve) gauge theories in string theory. Applications covered include dualities in 4 and 3 dimensions, fixed points in 6 dimensions, phase transitions between different geometric backgrounds and dualities between branes and geometry.

hep-th↗
arXiv1998

N=1 Supersymmetric Gauge Theories and Supersymmetric 3-cycles

In this paper we discuss the strong coupling limit of chiral N=1 supersymmetric gauge theory via their embedding into M-theory. In particular we focus on the brane box models of Hanany and Zaffaroni and show that after a T-duality transformation their M-theory embedding is described by supersymmetric 3-cycles; its geometry will encode the holomorphic non-perturbative information about the gauge theory.

hep-th↗
arXiv1998

Infrared Behaviour of Softly Broken SQCD and Its Dual

Applying the recently obtained results on the renormalization of soft supersymmetry-breaking parameters, we investigate the infrared behaviour of the softly broken supersymmetric QCD as well as its dual theory in the conformal window. Under general assumptions on $β$-functions, it is shown that the soft supersymmetry-breaking parameters asymptotically vanish in the infrared limit so that superconformal symmetry in softly broken supersymmetric QCD and in its dual theory revives at the infrared fixed point, provided the soft scalar masses satisfy certain renormalization group invariant relations. If these relations are not satisfied, there exist marginal operators in both theories that lead to the breaking of supersymmetry and also colour symmetry.

hep-th↗
arXiv1998

Superconformal N=1 Gauge Theories, beta-Function Invariants and their Behavior under Seiberg Duality

In this paper we discuss some aspects of the behavior of superconformal N=1 models under Seiberg's duality. Our claim is that if an electric gauge theory is superconformal on some marginal subspace of all coupling constants then its magnetic dual must be also superconformal on a corresponding moduli space of dual couplings. However this does not imply that the magnetic dual of a completely finite N=1 gauge theory is again finite. Moreover we generalize this statement conjecturing that also for non-superconformal N=1 models the determinant of the beta-function equations is invariant under Seiberg duality. During the course of this investigation we construct some superconformal N=1 gauge theories which were not yet discussed before.

hep-th↗
arXiv1998

Branes at Orbifolds versus Hanany Witten in Six Dimensions

We reconstruct non-trivial 6d theories obtained by Blum and Intriligator by considering IIB or SO(32) 5 branes at ALE spaces in the language of Hanany Witten setups. Using ST duality we make the equivalence of the two approaches manifest, thereby uncovering several new T-duality relations between the group theoretic data describing the embedding of the instantonic 5 brane in the ALE and brane positions in the Hanany Witten language. We construct several new 6d theories, which can be understood as arising on 5 branes in IIB orientifolds with oppositely charged orientifold planes recently introduced by Witten.

hep-th↗
arXiv1998

Brane Dynamics and Chiral non-Chiral Transitions

We study brane realizations of chiral matter in N=1 supersymmetric gauge theories in four dimensions. A "cross" configuration which leads to "flavor doubling" is found to have a superpotential. The main example is realized using a special "fork" configuration. Many of the results are found by studying a SU times SU product gauge group first. The chiral theory is then an orientifold projection of the product gauge group. An interesting observation in the brane picture is that there are transitions between chiral and non chiral models. These transitions are closely related to small instanton transitions in six dimensions.

hep-th↗
arXiv1997

Dualities in all order finite N=1 gauge theories

We search for dual gauge theories of all-loop finite, N = 1 supersymmetric gauge theories. It is shown how to find explicitly the dual gauge theories of almost all chiral, N = 1, all-loop finite gauge theories, while several models have been discussed in detail, including a realistic finite SU(5) unified theory. Out of our search only one all-loop, N = 1 finite SO(10) theory emerges, so far, as a candidate for exhibiting also S-duality.

hep-th↗
arXiv1997

Branes and Six Dimensional Fixed Points

We analyze brane configurations corresponding to non-trivial six dimensional fixed points. Several results previously obtained from a pure field theoretical analysis are rederived in the brane language.

hep-th↗
arXiv1997

Matrix Description of M-theory on $T^6$

We give some evidence that the worldvolume theory of the M-theory KK 6-brane is governed by a non-critical membrane theory. We use this theory to give a matrix description of M-theory on $T^6$.

hep-th↗
arXiv1997

Seiberg duality in three dimensions

We analyze three dimensional gauge theories with $Sp$ gauge group. We find that in some regime the theory should be described in terms of a dual theory, very much in the spirit of Seiberg duality in four dimensions. This duality does not coincide with mirror symmetry.

hep-th↗
arXiv1997

More on N=1 Self-Dualities and Exceptional Gauge Groups

Starting from a generalization of a recent result on self-duality we systematically analyze self-dual models. We find a criterion to judge whether a given model is self-dual or not. With this tool we construct some new self-dual pairs, focussing on examples with exceptional gauge groups.

hep-th↗
arXiv1996

N=1 Dualities for Exceptional Gauge Groups and Quantum Global Symmetries

We discuss our attempts to generalize the known examples of dualities in N=1 supersymmetric gauge theories to exceptional gauge groups. We derive some dual pairs from known examples connected to exceptional groups and find an interesting phenomenon: sometimes the full global symmetry is ``hidden'' on the magnetic side. It is not realized as a symmetry on the fundamental fields in the Lagrangian. Rather, it emerges as a symmetry of the quantum theory. We then focus on an approach based on self-dual models. We construct duals for some very special matter content of $E_ 7$, $E_6$ and $F_4$. Again we find that the full global symmetry is not realized on the fundamental fields.

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