94 research outputs found
Theory of K\"ahler Gravity
In this paper we discuss the connection on a space of TCFT's that
appears in the context of background (in)dependence. We formulate a family of
{\it target space field theories} with a similar connection on it. Each theory
is a gauge theory (with the gauge group being in the case of
-fold). It describes deformations of K\"ahler structures much like Kodaira
Spencer theory describes deformations of the complex structures. It is
manifestly background independent. It appears to be a target space field theory
for supersymmetric quantum mechanics
Large N limit of orbifold field theories
We consider certain orbifoldization of the field theories that
leads to field theories in 4 dimensions. These theories were
recently analyzed using the string theory perturbation technique. It was found
that in the large limit all correlation functions of the orbifold theories
coincide with those of , modulo the rescaling of the gauge coupling
constant. In this paper we repeat the same analysis using the field theoretical
language.Comment: 12 pages, 3 figures, harvmac. Minor change
Small Instantons, del Pezzo Surfaces and Type I' theory
Small instantons of exceptional groups arise geometrically by a collapsing
del Pezzo surface in a CY. We use this to explain the physics of a 4-brane
probe in Type I' compactification to 9 dimensions.Comment: 21 pages, minor change
On Four-Dimensional Compactifications of F-Theory
Branches of moduli space of F-theory in four dimensions are investigated. The
transition between two branches is described as a 3-brane-instanton transition
on a 7-brane. A dual heterotic picture of the transition is presented and the
F-theory - heterotic theory map is given. The F-theory data - complex structure
of the Calabi-Yau fourfold and the instanton bundle on the 7-brane is mapped to
the heterotic bundle on the elliptic Calabi-Yau threefold CY_3. The full moduli
space has a web structure which is also found in the moduli space of
semi-stable bundles on . Matter content of the four-dimensional theory is
discussed in both F-theory and heterotic theory descriptions.Comment: 40 pages, TeX, references added, minor changes in Section
A Unifying Topological Action for Heterotic and Type II Superstring Theories
The heterotic and type II superstring actions are identified in different
anomaly-free decompositions of a single topological sigma-model action
depending on bosonic and fermionic coordinates, and \r^A
respectively, and of their topological ghosts. This model results from
gauge-fixing the topological gauge symmetry () and \delta \r^\alpha= \epsilon^\alpha
(z,\bar z). (). From another viewpoint the heterotic and
type II superstring actions emerge as two different gauge-fixings of the same
closed two-form. Comments are also made concerning the possibility of relating
to a Majorana-Weyl space-time spinor superpartner of .Comment: 14 pages, LaTeX, no figure
String Expansion as Large N Expansion of Gauge Theories
We consider string perturbative expansion in the presence of D-branes
imbedded in orbifolded space-time. In the regime where the string coupling is
weak and , the string perturbative expansion coincides with `t
Hooft's large N expansion. We specifically concentrate on theories with d=4 and
, and use world-sheet orbifold techniques to prove vanishing
theorems for the field theory beta functions to all orders in perturbation
theory in the large N limit. This is in accord with recent predictions.Comment: 18 pages, harvmac, minor corrections and additional reference
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