1,601 research outputs found
Heterotic/type I duality, D-instantons and an N=2 AdS/CFT correspondence
D-instanton effects are studied for the IIB orientifold T^2/I\Omega(-1)^{F_L}
of Sen using type I/heterotic duality. An exact one loop threshold calculation
of t_8 \tr F^4 and t_8(\tr F^2)^2 terms for the heterotic string on T^2 with
Wilson lines breaking SO(32) to SO(8)^4 is related to D-instanton induced terms
in the worldvolume of D7 branes in the orientifold. Introducing D3 branes and
using the AdS/CFT correspondence in this case, these terms are used to
calculate Yang-Mills instanton contributions to four point functions of the
large N_c limit of N=2 USp(2N_c) SYM with four fundamental and one
antisymmetric tensor hypermultiplets.Comment: 25 pages, harvmac(b), one figure, v2: minor changes, version to
appear in PR
Hints for Off-Shell Mirror Symmetry in type II/F-theory Compactifications
We perform a Hodge theoretic study of parameter dependent families of
D-branes on compact Calabi-Yau manifolds in type II and F-theory
compactifcations. Starting from a geometric Gauss-Manin connection for B type
branes we study the integrability and flatness conditions. The B model geometry
defines an interesting ring structure of operators. For the mirror A model this
indicates the existence of an open-string extension of the so-called A model
connection, whereas the discovered ring structure should be part of the
open-string A model quantum cohomology. We obtain predictions for genuine
Ooguri-Vafa invariants for Lagrangian branes on the quintic in P4 that pass
some non-trivial consistency checks. We discuss the lift of the brane
compactifications to F-theory on Calabi-Yau 4-folds and the effective couplings
in the effective supergravity action as determined by the N = 1 special
geometry of the open-closed deformation space.Comment: 49 pages, 1 table; v2: Appendix and references added, minor
corrections; v3: discussion in sect. 2 extended, version published in
Nucl.Phys.
D-brane superpotentials and RG flows on the quintic
The behaviour of D2-branes on the quintic under complex structure
deformations is analysed by combining Landau-Ginzburg techniques with methods
from conformal field theory. It is shown that the boundary renormalisation
group flow induced by the bulk deformations is realised as a gradient flow of
the effective space time superpotential which is calculated explicitly to all
orders in the boundary coupling constant.Comment: 24 pages, 1 figure, v2:Typo in (3.14) correcte
A Note on Computations of D-brane Superpotential
We develop some computational methods for the integrals over the 3-chains on
the compact Calabi-Yau 3-folds that plays a prominent role in the analysis of
the topological B-model in the context of the open mirror symmetry. We discuss
such 3-chain integrals in two approaches. In the first approach, we provide a
systematic algorithm to obtain the inhomogeneous Picard-Fuchs equations. In the
second approach, we discuss the analytic continuation of the period integral to
compute the 3-chain integral directly. The latter direct integration method is
applicable for both on-shell and off-shell formalisms.Comment: 61 pages, 5 figures; v2: typos corrected, minor changes, references
adde
Moduli Webs and Superpotentials for Five-Branes
We investigate the one-parameter Calabi-Yau models and identify families of
D5-branes which are associated to lines embedded in these manifolds. The moduli
spaces are given by sets of Riemann curves, which form a web whose intersection
points are described by permutation branes. We arrive at a geometric
interpretation for bulk-boundary correlators as holomorphic differentials on
the moduli space and use this to compute effective open-closed superpotentials
to all orders in the open string couplings. The fixed points of D5-brane moduli
under bulk deformations are determined.Comment: 41 pages, 1 figur
Orientifolds, Unoriented Instantons and Localization
We consider world-sheet instanton effects in N=1 string orientifolds of
noncompact toric Calabi-Yau threefolds. We show that unoriented closed string
topological amplitudes can be exactly computed using localization techniques
for holomorphic maps with involution. Our results are in precise agreement with
mirror symmetry and large N duality predictions.Comment: 25 pages, 10 figures, published version; v4: typos correcte
The low energy expansion of the one-loop type II superstring amplitude
The one-loop four-graviton amplitude in either of the type II superstring
theories is expanded in powers of the external momenta up to and including
terms of order s^4 log s R^4, where R^4 denotes a specific contraction of four
linearized Weyl tensors and s is a Mandelstam invariant. Terms in this series
are obtained by integrating powers of the two-dimensional scalar field theory
propagator over the toroidal world-sheet as well as the moduli of the torus.
The values of these coefficients match expectations based on duality relations
between string theory and eleven-dimensional supergravity.Comment: harvmac (b), 25 pages, 3 eps figures. v2: Factors of 2 corrected.
Conclusion unchange
Enhanced Gauge Groups in N=4 Topological Amplitudes and Lorentzian Borcherds Algebras
We continue our study of algebraic properties of N=4 topological amplitudes
in heterotic string theory compactified on T^2, initiated in arXiv:1102.1821.
In this work we evaluate a particular one-loop amplitude for any enhanced gauge
group h \subset e_8 + e_8, i.e. for arbitrary choice of Wilson line moduli. We
show that a certain analytic part of the result has an infinite product
representation, where the product is taken over the positive roots of a
Lorentzian Kac-Moody algebra g^{++}. The latter is obtained through double
extension of the complement g= (e_8 + e_8)/h. The infinite product is
automorphic with respect to a finite index subgroup of the full T-duality group
SO(2,18;Z) and, through the philosophy of Borcherds-Gritsenko-Nikulin, this
defines the denominator formula of a generalized Kac-Moody algebra G(g^{++}),
which is an 'automorphic correction' of g^{++}. We explicitly give the root
multiplicities of G(g^{++}) for a number of examples.Comment: 33 pages, 3 figure
Higgs Mechanism in String Theory
In first-quantized string theory, spacetime symmetries are described by inner
automorphisms of the underlying conformal field theory. In this paper we use
this approach to illustrate the Higgs effect in string theory. We consider
string propagation on M^{24,1} \times S^1, where the circle has radius R, and
study SU(2) symmetry breaking as R moves away from its critical value. We find
a gauge-covariant equation of motion for the broken-symmetry gauge bosons and
the would-be Goldstone bosons. We show that the Goldstone bosons can be
eliminated by an appropriate gauge transformation. In this unitary gauge, the
Goldstone bosons become the longitudinal components of massive gauge bosons.Comment: 12 pages, Te
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