229 research outputs found
Pure Gauge SU(2) Seiberg-Witten Theory and Modular Forms
We identify the spectral curve of pure gauge SU(2) Seiberg-Witten theory with
the Weierstrass curve \mathbbm{C}/L \ni z \mapsto (1,\wp(z),\wp(z)') and
thereby obtain explicitely a modular form from which the moduli space parameter
and lattice parameters , can be derived in terms of modular
respectively theta functions. We further discuss its relationship with the
triplet model conformal field theory.Comment: 11 + 2 pages, no figures, shortened, to be published in jm
Gauge Thresholds and Kaehler Metrics for Rigid Intersecting D-brane Models
The gauge threshold corrections for globally consistent Z2 x Z2' orientifolds
with rigid intersecting D6-branes are computed. The one-loop corrections to the
holomorphic gauge kinetic function are extracted and the Kaehler metrics for
the charged chiral multiplets are determined up to two constants.Comment: 22 pages, 1 figure; v2: minor modifications, version to appear in
JHE
Stringy Instantons and Cascading Quivers
D-brane instantons can perturb the quantum field theories on space-time
filling D-branes by interesting operators. In some cases, these D-brane
instantons are novel "stringy" effects (not interpretable directly as instanton
effects in the low-energy quantum field theory), while in others the D-brane
instantons can be directly interpreted as field theory effects. In this note,
we describe a situation where both perspectives are available, by studying
stringy instantons in quivers which arise at simple Calabi-Yau singularities.
We show that a stringy instanton which wraps an unoccupied node of the quiver,
and gives rise to a non-perturbative mass in the space-time field theory, can
be reinterpreted as a conventional gauge theory effect by going up in an
appropriate renormalization group cascade. Interestingly, in the cascade, the
contribution of the stringy instanton does not come from gauge theory
instantons but from strong coupling dynamics.Comment: 17 pages, 6 figures, harvma
Instanton effects in N=1 brane models and the Kahler metric of twisted matter
We consider locally consistent systems of magnetized D9 branes on an
orbifolded six-torus which support N=1 gauge theories. In such realizations,
the matter multiplets arise from "twisted" strings connecting different stacks
of branes. The introduction of Euclidean 5 branes (E5) wrapped on the
six-dimensional compact space leads to instanton effects. For instance, if the
system is engineered so as to yield SQCD, a single E5 brane may account for the
ADS/TVY superpotential. We discuss the subtle interplay that exists between the
annuli diagrams with an E5 boundary and the holomorphicity properties of the
effective low-energy action of the N=1 theory. The consistency of this picture
allows to obtain information on the Kahler metric of the chiral matter
multiplets arising from twisted strings.Comment: 33 pages, 4 figures. V2: improved discussion, clarifyng comments and
references added. Version to be published in JHE
Instantons in N=2 magnetized D-brane worlds
In a toroidal orbifold of type IIB string theory we study instanton effects
in N=2 super Yang-Mills theories engineered with systems of wrapped magnetized
D9 branes and Euclidean D5 branes. We analyze the various open string sectors
in this brane system and study the 1-loop amplitudes described by annulus
diagrams with mixed boundary conditions, explaining their role in the stringy
instanton calculus. We show in particular that the non-holomorphic terms in
these annulus amplitudes precisely reconstruct the appropriate Kahler metric
factors that are needed to write the instanton correlators in terms of purely
holomorphic variables. We also explicitly derive the correct holomorphic
structure of the instanton induced low energy effective action in the Coulomb
branch.Comment: 40 pages, 5 figures, JHEP class. Some footnotes added and typos
corrected. Version published in JHE
Nonrelativistic Chern-Simons Vortices on the Torus
A classification of all periodic self-dual static vortex solutions of the
Jackiw-Pi model is given. Physically acceptable solutions of the Liouville
equation are related to a class of functions which we term
Omega-quasi-elliptic. This class includes, in particular, the elliptic
functions and also contains a function previously investigated by Olesen. Some
examples of solutions are studied numerically and we point out a peculiar
phenomenon of lost vortex charge in the limit where the period lengths tend to
infinity, that is, in the planar limit.Comment: 25 pages, 2+3 figures; improved exposition, corrected typos, added
one referenc
Lifting D-Instanton Zero Modes by Recombination and Background Fluxes
We study the conditions under which D-brane instantons in Type II orientifold
compactifications generate a non-perturbative superpotential. If the instanton
is non-invariant under the orientifold action, it carries four instead of the
two Goldstone fermions required for superpotential contributions. Unless these
are lifted, the instanton can at best generate higher fermionic F-terms of
Beasley-Witten type. We analyse two strategies to lift the additional zero
modes. First we discuss the process of instantonic brane recombination in Type
IIA orientifolds. We show that in some cases charge invariance of the measure
enforces the presence of further zero modes which, unlike the Goldstinos,
cannot be absorbed. In other cases, the instanton exhibits reparameterisation
zero modes after recombination and a superpotential is generated if these are
lifted by suitable closed or open string couplings. In the second part of the
paper we address lifting the extra Goldstinos of D3-brane instantons by
supersymmetric three-form background fluxes in Type IIB orientifolds. This
requires non-trivial gauge flux on the instanton. Only if the part of the
fermionic action linear in the gauge flux survives the orientifold projection
can the extra Goldstinos be lifted.Comment: 38 pages, 3 figures, 5 tables; v2: Appendix B slightly expanded,
minor rewordin
Unoriented D-brane Instantons vs Heterotic worldsheet Instantons
We discuss Fermi interactions of four hyperini generated by ``stringy''
instantons in a Type I / Heterotic dual pair on T^4/Z_2.Comment: Minor corrections and clarifications. Added reference
Infrared stability of ABJ-like theories
We consider marginal deformations of the superconformal ABJM/ABJ models which
preserve N=2 supersymmetry. We determine perturbatively the spectrum of fixed
points and study their infrared stability. We find a closed line of fixed
points which is IR stable. The fixed point corresponding to the ABJM/ABJ models
is stable under marginal deformations which respect the original SU(2)xSU(2)
invariance, while deformations which break this group destabilize the theory
which then flows to a less symmetric fixed point. We discuss the addition of
flavor degrees of freedom. We prove that in general a flavor marginal
superpotential does not destabilize the system in the IR. An exception is
represented by a marginal coupling which mixes matter charged under different
gauge sectors. Finally, we consider the case of relevant deformations which
should drive the system to a strongly coupled IR fixed point recently
investigated in arXiv:0909.2036 [hep-th].Comment: 1+11 pages, 4 figures; v2: minor correction
D-instanton derivation of multi-fermion F-terms in supersymmetric QCD
We investigate effects of field theory instantons by considering D-instantons
in a suitable D3-brane background. In supersymmetric QCD with SU(N_c) gauge
group with N_f=N_c flavors, the moduli space of vacua is deformed by
instantons. This effect can be described by the chiral interactions which are
called multi-fermion F-terms. We derive these chiral interaction terms as
D-instanton effects in the presence of D3-branes. For SU(2), the obtained
result agrees with the previous result worked out by Beasley and Witten
[hep-th/0409149]. We also explicitly work out those for the case of the
symplectic gauge group, and show that they describe the deformation of the
moduli space.Comment: 25 page
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