Techniques for improving reliability of computers

Modular design techniques improve methods of error detection, diagnosis, and recovery. Theoretical computer (MARCS (Modular Architecture for Reliable Computer Systems)) study deals with postulated and modeled technology indigenous to 1975-1980. Study developments are discussed

Iterative Solution of the Supereigenvalue Model

An integral form of the discrete superloop equations for the supereigenvalue model of Alvarez-Gaume, Itoyama, Manes and Zadra is given. By a change of variables from coupling constants to moments we find a compact form of the planar solution for general potentials. In this framework an iterative scheme for the calculation of higher genera contributions to the free energy and the multi-loop correlators is developed. We present explicit results for genus one.Comment: 21 pages, LaTeX, no figure

Supersymmetric Chern-Simons Theories with Vector Matter

In this paper we discuss SU(N) Chern-Simons theories at level k with both fermionic and bosonic vector matter. In particular we present an exact calculation of the free energy of the N=2 supersymmetric model (with one chiral field) for all values of the 't Hooft coupling in the large N limit. This is done by using a generalization of the standard Hubbard-Stratanovich method because the SUSY model contains higher order polynomial interactions.Comment: 46 pages, 24 figures, v2: comments and references added, v3: a footnote in Section 3.5 adde

Quark Confinement and Dual Representation in 2+1 Dimensional Pure Yang-Mills Theory

We study the quark confinement problem in 2+1 dimensional pure Yang-Mills theory using euclidean instanton methods. The instantons are regularized and dressed Wu-Yang monopoles. The dressing of a monopole is due to the mean field of the rest of the monopoles. We argue that such configurations are stable to small perturbations unlike the case of singular, undressed monopoles. Using exact non-perturbative results for the 3-dim. Coulomb gas, where Debye screening holds for arbitrarily low temperatures, we show in a self-consistent way that a mass gap is dynamically generated in the gauge theory. The mass gap also determines the size of the monopoles. In a sense the pure Yang-Mills theory generates a dynamical Higgs effect. We also identify the disorder operator of the model in terms of the Sine-Gordon field of the Coulomb gas.Comment: 26 pages, RevTex, Title changed, a new section added, the discussion on stability of dressed monopole expanded. Version to appear in Physical Review

Nielsen-Olesen Vortices in Noncommutative Abelian Higgs Model

We construct Nielsen-Olesen vortex solution in the noncommutative abelian Higgs model. We derive the quantized topological flux of the vortex solution. We find that the flux is integral by explicit computation in the large $\theta$ limit as well as in the small $\theta$ limit. In the context of a tachyon vortex on the brane-antibrane system we demonstrate that it is this topological charge that gives rise to the RR charge of the resulting BPS D-brane. We also consider the left-right-symmetric gauge theory which does not have a commutative limit and construct an exact vortex solution in it.Comment: 24 pages, (v2) clarifying comments added regarding topological index using coherent states; n-vortex solution added; version to appear in JHE

French feminism: national and international perspectives

During the 1980s, the French media proclaimed the death of feminism, but although the 1970s women’s movement had demobilised, feminists were still active in issue-specific groups, in academia and within the institutions of the state. Paying careful attention to the difficulties associated with defining feminisms and national feminisms in particular, this article situates an analysis of French feminism since the 1980s in a context of growing international feminist dialogue and activism and a renewed debate about the meaning of feminism. It focuses on the question of separatism and on changing relations between theory and practice, asking how feminists can act for change and form effective coalitions with men and with other movements. It argues that feminism is plural and often fragmented and diffuse. Feminism is shaped by local social, economic, political and cultural factors and by exchanges of people and ideas, and any analysis of feminist theory and activism needs to take these into account

Pure Cerebellar Ataxia with Homozygous Mutations in the PNPLA6 Gene

Autosomal-recessive cerebellar ataxias (ARCA) are clinically and genetically heterogeneous conditions primarily affecting the cerebellum. Mutations in the PNPLA6 gene have been identified as the cause of hereditary spastic paraplegia and complex forms of ataxia associated with retinal and endocrine manifestations in a field where the genotype-phenotype correlations are rapidly expanding. We identified two cousins from a consanguineous family belonging to a large Zoroastrian (Parsi) family residing in Mumbai, India, who presented with pure cerebellar ataxia without chorioretinal dystrophy or hypogonadotropic hypogonadism. We used a combined approach of clinical characterisation, homozygosity mapping, whole-exome and Sanger sequencing to identify the genetic defect in this family. The phenotype in the family was pure cerebellar ataxia. Homozygosity mapping revealed one large region of shared homozygosity at chromosome 19p13 between affected individuals. Within this region, whole-exome sequencing of the index case identified two novel homozygous missense variants in the PNPLA6 gene at c.3847G>A (p.V1283M) and c.3929A>T (p.D1310V) in exon 32. Both segregated perfectly with the disease in this large family, with only the two affected cousins being homozygous. We identified for the first time PNPLA6 mutations associated with pure cerebellar ataxia in a large autosomal-recessive Parsi kindred. Previous mutations in this gene have been associated with a more complex phenotype but the results here suggest an extension of the associated disease spectrum

Symmetry Breaking in the Double-Well Hermitian Matrix Models

We study symmetry breaking in $Z_2$ symmetric large $N$ matrix models. In the planar approximation for both the symmetric double-well $\phi^4$ model and the symmetric Penner model, we find there is an infinite family of broken symmetry solutions characterized by different sets of recursion coefficients $R_n$ and $S_n$ that all lead to identical free energies and eigenvalue densities. These solutions can be parameterized by an arbitrary angle $\theta(x)$, for each value of $x = n/N < 1$. In the double scaling limit, this class reduces to a smaller family of solutions with distinct free energies already at the torus level. For the double-well $\phi^4$ theory the double scaling string equations are parameterized by a conserved angular momentum parameter in the range $0 \le l < \infty$ and a single arbitrary $U(1)$ phase angle.Comment: 23 pages and 4 figures, Preprint No. CERN-TH.6611/92, Brown HET-863, HUTP -- 92/A035, LPTHE-Orsay: 92/2

Single-plant chambers to control humidity for pathological studies

The construction of a set of controlled-humidity chambers for single plants is described. Accurate control of relative humidity (r.h.) between 40% and 99% was achieved by mixing dry air with a saturated air stream using solenoid valves controlled by a programmable data logger. At values of r.h. >90%, mean values over periods greater than 1 min were constant to within ±0-1% and spot measurements at 3 s intervals were within 0-3% of the mean value. The system responded to a step change of r.h. in about 6-10 min and diurnal changes of r.h. were reproduced, similar to those observed in nature. The stability of control made it possible to differentiate between the requirement of liquid water and very high humidity (98% r.h.) for conidial germination and subsequent infection of groundnut by Phaeoisariopsis personata, the cause of late leaf spot disease

Matrix dynamics of fuzzy spheres

We study the dynamics of fuzzy two-spheres in a matrix model which represents string theory in the presence of RR flux. We analyze the stability of known static solutions of such a theory which contain commuting matrices and SU(2) representations. We find that irreducible as well as reducible representations are stable. Since the latter are of higher energy, this stability poses a puzzle. We resolve this puzzle by noting that reducible representations have marginal directions corresponding to non-spherical deformations. We obtain new static solutions by turning on these marginal deformations. These solutions now have instability or tachyonic directions. We discuss condensation of these tachyons which correspond to classical trajectories interpolating from multiple, small fuzzy spheres to a single, large sphere. We briefly discuss spatially independent configurations of a D3/D5 system described by the same matrix model which now possesses a supergravity dual.Comment: 26 pages, 3 figures, uses JHEP.cls; (v2) references adde