170 research outputs found
Modular and duality properties of surface operators in N=2* gauge theories
We calculate the instanton partition function of the four-dimensional N=2*
SU(N) gauge theory in the presence of a generic surface operator, using
equivariant localization. By analyzing the constraints that arise from
S-duality, we show that the effective twisted superpotential, which governs the
infrared dynamics of the two-dimensional theory on the surface operator,
satisfies a modular anomaly equation. Exploiting the localization results, we
solve this equation in terms of elliptic and quasi-modular forms which resum
all non-perturbative corrections. We also show that our results, derived for
monodromy defects in the four-dimensional theory, match the effective twisted
superpotential describing the infrared properties of certain two-dimensional
sigma models coupled either to pure N=2 or to N=2* gauge theories.Comment: 51 pages, v3: references added, typos fixed, footnote added, some
small changes in the text, appendix B streamlined. Matches the published
versio
Notes on unoriented D-brane instantons
In the first lecture, we discuss basic aspects of worldsheet and penta-brane
instantons as well as (unoriented) D-brane instantons, which is our main focus
here, and threshold corrections to BPS-saturated couplings. The second lecture
is devoted to non-perturbative superpotentials generated by `gauge' and
`exotic' instantons living on D3-branes at orientifold singularities. In the
third lecture we discuss the interplay between worldsheet and D-string
instantons on . We focus on a 4-fermi amplitude, give Heterotic and
perturbative Type I descriptions, and offer a multi D-string instanton
interpretation. We conclude with possible interesting developments.Comment: 31 pages. Based on lectures delivered by M. Bianchi at the Fourth
Young Researchers Workshop of the European Superstring Theory Network in
Kounnas Bay, Cyprus, September 200
Surface operators in 5d gauge theories and duality relations
We study half-BPS surface operators in 5d N=1 gauge theories compactified on
a circle. Using localization methods and the twisted chiral ring relations of
coupled 3d/5d quiver gauge theories, we calculate the twisted chiral
superpotential that governs the infrared properties of these surface operators.
We make a detailed analysis of the localization integrand, and by comparing
with the results from the twisted chiral ring equations obtain constraints on
the 3d and 5d Chern-Simons levels so that the instanton partition function does
not depend on the choice of integration contour. For these values of the
Chern-Simons couplings, we comment on how the distinct quiver theories that
realize the same surface operator are related to each other by Aharony-Seiberg
dualities.Comment: 39 pages. v2: A few sentences rephrased, references added, and typos
corrected. Matches version published in JHE
HyperK\"ahler quotients and N=4 gauge theories in D=2
We consider certain N=4 supersymmetric gauge theories in D=2 coupled to
quaternionic matter multiplets in a minimal way. These theories admit as
effective theories sigma-models on non-trivial HyperK\"ahler manifolds obtained
as HyperK\"ahler quotients. The example of ALE manifolds is discussed. (Based
on a talk given by P. Fr\'e at the F. Gursey Memorial Conference, Istanbul,
June 1994).Comment: 22 pages, Latex, no figure
Two Moving-Angled 1-Branes with Electric Fields in a Partially Compact Spacetime
In this article we consider two -branes at angle in the presence of the
background electric fields, in a partially compact spacetime. The branes have
motions along a common direction that is perpendicular to both of them. Using
the boundary state formalism, we calculate their interaction amplitude. Some
special cases of this interaction will be studied in detail.Comment: 10 pages, no figure, Late
D-brane Instantons on the T^6/Z_3 orientifold
We give a detailed microscopic derivation of gauge and stringy instanton
generated superpotentials for gauge theories living on D3-branes at
Z_3-orientifold singularities. Gauge instantons are generated by D(-1)-branes
and lead to Affleck, Dine and Seiberg (ADS) like superpotentials in the
effective N=1 gauge theories with three generations of bifundamental and
anti/symmetric matter. Stringy instanton effects are generated by Euclidean
ED3-branes wrapping four-cycles on T^6/\Z_3. They give rise to Majorana masses
in one case and non-renormalizable superpotentials for the other cases. Finally
we determine the conditions under which ADS like superpotentials are generated
in N=1 gauge theories with adjoints, fundamentals, symmetric and antisymmetric
chiral matter.Comment: 31 pages, no figure
Surface operators, dual quivers and contours
We study half-BPS surface operators in four dimensional N=2 SU(N) gauge
theories, and analyze their low-energy effective action on the four dimensional
Coulomb branch using equivariant localization. We also study surface operators
as coupled 2d/4d quiver gauge theories with an SU(N) flavour symmetry. In this
description, the same surface operator can be described by different quivers
that are related to each other by two dimensional Seiberg duality. We argue
that these dual quivers correspond, on the localization side, to distinct
integration contours that can be determined by the Fayet-Iliopoulos parameters
of the two dimensional gauge nodes. We verify the proposal by mapping the
solutions of the twisted chiral ring equations of the 2d/4d quivers onto
individual residues of the localization integrand.Comment: 42 pages. v2: Sections 4 and 5 partially restructured in order to
describe in a more compact ad unified way the association of contours to
quiver
N=4 superconformal mechanics as a Non linear Realization
An action for a superconformal particle is constructed using the non linear
realization method for the group PSU(1,1|2), without introducing superfields.
The connection between PSU(1,1|2) and black hole physics is discussed. The
lagrangian contains six arbitrary constants and describes a non-BPS
superconformal particle. The BPS case is obtained if a precise relation between
the constants in the lagrangian is verified, which implies that the action
becomes kappa-symmetric.Comment: new subection, references added and new acknowledgment
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