112 research outputs found
String Webs from Field Theory
The spectrum of stable electrically and magnetically charged supersymmetric
particles can change discontinuously as one changes the vacuum on the Coulomb
branch of gauge theories with extended supersymmetry in four dimensions. We
show that this decay process can be understood and is well described by
semiclassical field configurations purely in terms of the low energy effective
action on the Coulomb branch even when it occurs at strong coupling. The
resulting picture of the stable supersymmetric spectrum is a generalization of
the ``string web'' picture of these states found in string constructions for
certain theories.Comment: 53 pages, 6 figures; more references adde
Coulomb branches with complex singularities
We construct 4d superconformal field theories (SCFTs) whose Coulomb branches
have singular complex structures. This implies, in particular, that their
Coulomb branch coordinate rings are not freely generated. Our construction also
gives examples of distinct SCFTs which have identical moduli space (Coulomb,
Higgs, and mixed branch) geometries. These SCFTs thus provide an interesting
arena in which to test the relationship between moduli space geometries and
conformal field theory data.
We construct these SCFTs by gauging certain discrete global symmetries of
superYang-Mills (sYM) theories. In the simplest cases, these
discrete symmetries are outer automorphisms of the sYM gauge group, and so
these theories have lagrangian descriptions as sYM theories with
disconnected gauge groups.Comment: 43 page
The Nonperturbative Gauge Coupling of N=2 Supersymmetric Theories
We argue that the topology of the quantum coupling space and the low energy
effective action on the Coulomb branch of scale invariant N=2 SU(n) gauge
theories pick out a preferred nonperturbative definition of the gauge coupling
up to non-singular holomorphic reparametrizations.Comment: 9 pages latex and 2 figures using psfig.sty; computation of S-duality
group corrected and reference adde
4d =2 theories with disconnected gauge groups
In this paper we present a beautifully consistent web of evidence for the
existence of interacting 4d rank-1 SCFTs obtained from gauging
discrete subgroups of global symmetries of other existing 4d rank-1
SCFTs. The global symmetries that can be gauged involve a
non-trivial combination of discrete subgroups of the , low-energy EM
duality group , and the outer automorphism group of the
flavor symmetry algebra, Out().
The theories that we construct are remarkable in many ways: (i) two of them
have exceptional and flavor groups; (ii) they substantially
complete the picture of the landscape of rank-1 SCFTs as they
realize all but one of the remaining consistent rank-1 Seiberg-Witten
geometries that we previously constructed but were not associated to known
SCFTs; and (iii) some of them have enlarged SUSY, and have not
been previously constructed. They are also examples of SCFTs which violate the
Shapere-Tachikawa relation between the conformal central charges and the
scaling dimension of the Coulomb branch vev. We propose a modification of the
formulas computing these central charges from the topologically twisted Coulomb
branch partition function which correctly compute them for discretely gauged
theories.Comment: 45 pages, 3 figure
Comparing Instanton Contributions with Exact Results in N=2 Supersymmetric Scale Invariant Theories
We discuss the general issues and ambiguities involved in matching the exact
results for the low energy effective action of scale invariant N=2
supersymmetric QCD to those obtained by instanton methods. We resolve the
reported disagreements and verify agreement between an infinite series of
coefficients in the low energy effective actions calculated in the two
approaches. In particular, we show that the exact low-energy effective
couplings for SU(N) for all N with 2N fundamental hypermultiplets agree at a
special vacuum on the Coulomb branch where a large unbroken discrete global
symmetry makes the matching of parameters relatively straightforward.Comment: 26 pages, 1 figure; report-no. correcte
The Vacuum Structure of N=2 SuperQCD with Classical Gauge Groups
We determine the vacuum structure of N=2 supersymmetric QCD with fundamental
quarks for gauge groups SO(n) and Sp(2n), extending prior results for SU(n).
The solutions are all given in terms of families of hyperelliptic Riemann
surfaces of genus equal to the rank of the gauge group. In the scale invariant
cases, the solutions all have exact S-dualities which act on the couplings by
subgroups of PSL(2,Z) and on the masses by outer automorphisms of the flavor
symmetry. They are shown to reproduce the complete pattern of symmetry breaking
on the Coulomb branch and predict the correct weak--coupling monodromies.
Simple breakings with squark vevs provide further consistency checks involving
strong--coupling physics.Comment: 29 pages, harvmac, 1 figure included using epsf.te
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