98 research outputs found

### An N=1 Triality by Spectrum Matching

On promoting the type IIA side of the N=1 Heterotic/type IIA dual pairs of
[1] to M-theory on a `barely G_2 Manifold' of [2], by spectrum-matching we show
a possible triality between Heterotic on a self-mirror Calabi-Yau, M-theory on
the above `barely G_2-Manifold' constructed from the Calabi-Yau on the type IIA
side and $F$-theory on an elliptically fibered Calabi-Yau 4-fold fibered over a
trivially rationally ruled CP^1 x E base, E being the Enriques surface. We
raise an apparent puzzle on the F-theory side, namely, the Hodge data of the
4-fold derived can not be obtained by a naive freely acting orbifold of
CY_3(3,243) x T^2 as one might have guessed on the basis of arguments related
to dualities involving string, M and (definition of) F theories. There are some
interesting properties of the antiholomorphic involution used in \cite{VW} for
constructing the type IIA orientifold and by us in constructing the 'barely G_2
manifold', that we also study.Comment: 14 pages, LaTex; v3: journal versio

### Duality of N=2 Heterotic -- Type I Compactifications in Four Dimensions

We discuss type I -- heterotic duality in four-dimensional models obtained as
a Coulomb phase of the six-dimensional U(16) orientifold model compactified on
T^2 with arbitrary SU(16) Wilson lines. We show that Kahler potentials, gauge
threshold corrections and the infinite tower of higher derivative F-terms agree
in the limit that corresponds to weak coupling, large T^2 heterotic
compactifications. On the type I side, all these quantities are completely
determined by the spectrum of N=2 BPS states that originate from D=6 massless
superstring modes.Comment: 22 pages, LaTeX; typos corrected and references adde

### Phases of supersymmetric gauge theories from M-theory on G_2 manifolds

We consider M-theory on compact spaces of G_2 holonomy constructed as
orbifolds of the form (CY x S^1)/Z_2 with fixed point set \Sigma on the CY.
This describes N=1 SU(2) gauge theories with b_1(\Sigma) chiral multiplets in
the adjoint. For b_1=0, it generalizes to compact manifolds the study of the
phase transition from the non-Abelian to the confining phase through
geometrical S^3 flops. For b_1=1, the non-Abelian and Coulomb phases are
realized, where the latter arises by desingularization of the fixed point set,
while an S^2 x S^1 flop occurs. In addition, an extremal transition between G_2
spaces can take place at conifold points of the CY moduli space where
unoriented membranes wrapped on CP^1 and RP^2 become massless.Comment: 21 pages, LaTeX, v2: mistake in spectra corrected, reference added,
v3: one more reference added, version published in JHE

### D-Instanton Corrections as (p,q)-String Effects and Non-Renormalization Theorems

We discuss higher derivative interactions in the type IIB superstring in ten
dimensions. From the fundamental string point of view, the non-perturbative
corrections are due to D-instantons. We argue that they can alternatively be
understood as arising from $(p,q)$-strings. We derive a non-renormalization
theorem for eight-derivative bosonic interactions, which states that terms
involving either NS-NS or R-R fields occur at tree-level and one-loop only. By
using the $SL(2, Z)$ symmetry of M-theory on $T^2$, we show that in order for
the possible $R^{3m+1} (m=1,2,...)$ interactions in M-theory to have a
consistent perturbative expansion in nine dimensions, $m$ must be odd. Thus,
only $R^{6N+4} (N=0,1,...)$ terms can be present in M-theory and their string
theory counterparts arise at $N$ and $2N+1$ loops. Finally, we treat an example
of fermionic term.Comment: 24 pages, latex, additional arguments for the perturbative form of
the eight-derivative interaction

### Time-Varying Coefficients in a GMM Framework: Estimation of a Forward Looking Taylor Rule for the Federal Reserve.

This article deals with the estimation of a time-varying coefficients equation with endogenous regressors. A non-parametric approach is proposed, combining the Generalized Method of Moments (GMM) with the smoothing splines litterature as in Hodrick and Prescott (1981). This new method is used to analyze the evolution of a forward-looking Taylor rule for the Federal Reserve (FED) from 1960 until 2006. It suggests that monetary policy accommodated inflation during the 60s and the 70s whereas the chairmanship of P. Volcker was a turning point toward a more aggressive stance on inflation. In addition, monetary policy became more and more countercyclical.Monetary policy rules ; Generalized Method of Moments ; Time-varying coefficients ; Smoothing splines.

### Exact monodromy group of N=2 heterotic superstring

We describe an N=2 heterotic superstring model of rank-3 which is dual to the type-II string compactified on a Calabi-Yau manifold with Betti numbers b_{1,1}=2 and b_{1,2}=86. We show that the exact duality symmetry found from the type-II realization contains the perturbative duality group of the heterotic model, as well as the exact quantum monodromies of the rigid SU(2) super-Yang-Mills theory. Moreover, it contains a non-perturbative monodromy which is stringy in origin and corresponds roughly to an exchange of the string coupling with the compactification radius

### The Exact Quartic Effective Action for the Type IIB Superstring

We propose a four-point effective action for the graviton, antisymmetric two-forms, dilaton and axion of type IIB superstring in ten dimensions. It is explicitly SL(2,Z)-invariant and reproduces the known tree-level results. Perturbatively, it has only one-loop corrections generalizing the non-renormalization theorem of the R^4 term. Finally, the non-perturbative corrections are of the expected form, namely, they can be interpreted as arising from single D-instantons of multiple charge

### On the equivalence of N=1 brane worlds and geometric singularities with flux

We consider Kaluza Klein reductions of M-theory on the Z_N orbifold of the
spin bundle over S^3 along two different U(1) isometries. The first one gives
rise to the familiar ``large N duality'' of the N=1 SU(N) gauge theory in which
the UV is realized as the world-volume theory of N D6-branes wrapped on S^3,
whereas the IR involves N units of RR flux through an S^2. The second reduction
gives an equivalent version of this duality in which the UV is realized
geometrically in terms of an S^2 of A_{N-1} singularities, with one unit of RR
flux through the S^2. The IR is reached via a geometric transition and involves
a single D6 brane on a lens space S^3/Z_N or, alternatively, a singular
background (S^2\times R^4)/Z_N, with one unit of RR flux through S^2 and,
localized at the singularities, an action of their stabilizer group in the U(1)
RR gauge bundle, so that no massless twisted states occur. We also consider
linear sigma-model descriptions of these backgrounds.Comment: 25 pages, LaTeX; v2: one reference added, published versio

### $AdS_6$ Interpretation of 5d Superconformal Field Theories

We explore the connection of anti-de-Sitter supergravity in six dimensions, based on the exceptional F(4) superalgebra, and its boundary superconformal singleton theory. The interpretation of these results in terms of a D4-D8 system and its near horizon geometry is suggested

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