On the Instanton Contributions to the Masses and Couplings of E6E_6 Singlets

We consider the gauge neutral matter in the low--energy effective action for string theory compactification on a \cym\ with $(2,2)$ world--sheet supersymmetry. At the classical level these states (the \sing's of $E_6$) correspond to the cohomology group H^1(\M,{\rm End}\>T). We examine the first order contribution of instantons to the mass matrix of these particles. In principle, these corrections depend on the \K\ parameters $t_i$ through factors of the form e^{2\p i t_i} and also depend on the complex structure parameters. For simplicity we consider in greatest detail the quintic threefold \cp4[5]. It follows on general grounds that the total mass is often, and perhaps always, zero. The contribution of individual instantons is however nonzero and the contribution of a given instanton may develop poles associated with instantons coalescing for certain values of the complex structure. This can happen when the underlying \cym\ is smooth. Hence these poles must cancel between the coalescing instantons in order that the superpotential be finite. We examine also the \Y\ couplings involving neutral matter \ysing\ and neutral and charged fields \ymix, which have been little investigated even though they are of phenomenological interest. We study the general conditions under which these couplings vanish classically. We also calculate the first--order world--sheet instanton correction to these couplings and argue that these also vanish.Comment: 40 pages, plain TeX with epsf, one uuencoded figur

A Class of N=1 Supersymmetric RG Flows from Five-dimensional N = 8 Supergravity

We consider the holographic dual of a general class of N=1* flows in which all three chiral multiplets have independent masses, and in which the corresponding Yang-Mills scalars can develop particular supersymmetry-preserving vevs. We also allow the gaugino to develop a vev. This leads to a six parameter subspace of the supergravity scalar action, and we show that this is a consistent truncation, and obtain a superpotential that governs the N=1* flows on this subspace. We analyse some of the structure of the superpotential, and check consistency with the asymptotic behaviour near the UV fixed point. We show that the dimensions of the six couplings obey a sum rule all along the N=1* flows. We also show how our superpotential describes part of the Coulomb branch of the non-trivial N=1 fixed point theory.Comment: 14 pages; harvmac. New version has only minor correction

Deformed Quantum Cohomology and (0,2) Mirror Symmetry

We compute instanton corrections to correlators in the genus-zero topological subsector of a (0,2) supersymmetric gauged linear sigma model with target space P1xP1, whose left-moving fermions couple to a deformation of the tangent bundle. We then deduce the theory's chiral ring from these correlators, which reduces in the limit of zero deformation to the (2,2) ring. Finally, we compare our results with the computations carried out by Adams et al.[ABS04] and Katz and Sharpe[KS06]. We find immediate agreement with the latter and an interesting puzzle in completely matching the chiral ring of the former.Comment: AMSLatex, 30 pages, one eps figure. V4: typos corrected, final version appearing in JHE

Field condensations and Noncritical String for c>1

Quantum theory of 2d gravity for $c>1$ is examined as a non-critical string theory by taking account of the loop-correction of open strings whose end points are on the 2d world surface of the closed string. This loop-correction leads to a conformal anomaly, and we obtain a modified target-space action which implies a new phase of the non-critical closed-string. In this phase, the dual field of the gauge field, which lives on the boundary, condenses and the theory can be extended to $c>1$ without any instability.Comment: 17 pages, Latex, no figur

FOREVER: Fault/intrusiOn REmoVal through Evolution & Recovery

The goal of the FOREVER project is to develop a service for Fault/intrusiOn REmoVal through Evolution & Recovery. In order to achieve this goal, our work addresses three main tasks: the definition of the FOREVER service architecture; the analysis of how diversity techniques can improve resilience; and the evaluation of the FOREVER service. The FOREVER service is an important contribution to intrustion-tolerant replication middleware and significantly enhances the resilience

Fermionic characters for graded parafermions

Fermionic-type character formulae are presented for charged irreduciblemodules of the graded parafermionic conformal field theory associated to the coset $osp(1,2)_k/u(1)$. This is obtained by counting the weakly ordered `partitions' subject to the graded $Z_k$ exclusion principle. The bosonic form of the characters is also presented.Comment: 24 p. This corrects typos (present even in the published version) in eqs (4.4), (5.23), (5.24) and (C.4

A Possible IIB Superstring Matrix Model with Euler Characteristic and a Double Scaling Limit

We show that a recently proposed Yang-Mills matrix model with an auxiliary field, which is a candidate for a non-perturbative description of type IIB superstrings, captures the Euler characteristic of moduli space of Riemann surfaces. This happens at the saddle point for the Yang-Mills field. It turns out that the large-n limit in this matrix model corresponds to a double scaling limit in the Penner model.Comment: 5 pages, LaTe

Semirigid Geometry

We provide an intrinsic description of $N$-super \RS s and $TN$-\SR\ surfaces. Semirigid surfaces occur naturally in the description of topological gravity as well as topological supergravity. We show that such surfaces are obtained by an integrable reduction of the structure group of a complex supermanifold. We also discuss the \s moduli spaces of $TN$-\SR\ surfaces and their relation to the moduli spaces of $N$-\s\ \RS s.Comment: 29p