Multi - instantons, supersymmetry and topological field theories

In this letter we argue that instanton-dominated Green's functions in N=2 Super Yang-Mills theories can be equivalently computed either using the so-called constrained instanton method or making reference to the topological twisted version of the theory. Defining an appropriate BRST operator (as a supersymmetry plus a gauge variation), we also show that the expansion coefficients of the Seiberg-Witten effective action for the low-energy degrees of freedom can be written as integrals of total derivatives over the moduli space of self-dual gauge connections

Analysis of Rail Yard and Terminal Performances

One of the latest trends in the transport field is the increasing interest for the rejuvenation of the railway. It is considered to be a logical consequence of the gradual switch towards a more sustainable future in transports. Terminals and stations are considered to be the junction points between the various lines that constitute the railway network and can simply be described as points of arrival, departure and interchange of passengers or commodities. The most commonly used indicators that measure the level of their performance are time and cost. This study aims at exploring possible improvements that could be implemented to the infrastructure and the operation of terminals and stations in order to increase the efficiency level. Firstly, drawing upon grounded theory, a description is conducted, followed by a comparative analysis of the different types of existing terminals and stations. Secondly, the suggested improvements are presented in accordance with their time frame completion. The main contribution of the study is to illustrate the high significance of terminals, stations and yards, given the fact that they are considered to be crucial parts of the railway network. In addition to this, great emphasis is given to the need of improving and developing the existing terminal infrastructure and operations

N=2 SYM RG Scale as Modulus for WDVV Equations

We derive a new set of WDVV equations for N=2 SYM in which the renormalization scale $\Lambda$ is identified with the distinguished modulus which naturally arises in topological field theories.Comment: 6 pages, LaTe

Viral genotype and HLA class II alleles influence on extra-hepatic manifestations of chronic HCV infection

Objective: To test whether an association between HCV genotype, HLA class II alleles distribution and extra-hepatic manifestations (EHM ) can be demonstrated in a group of Italian patients with chronic HCV infection . Methods: Sixty patients affected by HCV infection with EHM were consecutively enrolled. 163 HCV patients without EHM were tested as controls for the prevalence of HCV genotypes, while we referred to literature as to the controls for HLA distribution. HCV-RNA was quantified by a RT-PCR. HLA class II alleles typing was performed using a standard microlymphocytotoxicity assay. We used chi-square or Fisher test (p<0.05 significant). Odds Ratio (OR) was performed by 2X2 contingency table. Results: HCV 2c genotype was found in 63.46% of patients compared to 19.63% of controls (p<0.0001; OR=7.11). Furthermore, it correlated with carpal tunnel syndrome (p=0.03; OR=4.5) and autoimmune thyroiditis (p=0.02; OR=9.2). On the contrary, 1b genotype protected from EHM in toto (p=0.0004; OR=0.21) and particularly from carpal tunnel syndrome (p=0.0014; OR=0.07). Moreover, 3a genotype prevented HCV people from having cryoglobulinemia (p=0.05; OR=0.11). As to HLA, DR6 seemed to facilitate EHM in HCV patients (p=0.041; OR=1.61), while DQ2 (p=0.03; OR=0.5) and DQ3 (p=0.002; OR= 0.5) may play a protective role. In addition, HLA DR3 was associated with cryoglobulinemia (p=0.02; OR=9.5). Conclusions: According to our findings, 2c genotype can be considered as a major risk factor for developing HCVrelated EHM, while 1b genotype seems to prevent their onset; there are also evidences suggesting that HLA might play a role in chronic HCV infected patients

Instantons on Quivers and Orientifolds

We compute the prepotential for gauge theories descending from ${\cal N}=4$ SYM via quiver projections and mass deformations. This accounts for gauge theories with product gauge groups and bifundamental matter. The case of massive orientifold gauge theories with gauge group SO/Sp is also described. In the case with no gravitational corrections the results are shown to be in agreement with Seiberg-Witten analysis and previous results in the literature.Comment: 28 pages, revised version, references added, some typos correcte

Topological Vector Symmetry of BRSTQFT and Construction of Maximal Supersymmetry

The scalar and vector topological Yang-Mills symmetries determine a closed and consistent sector of Yang-Mills supersymmetry. We provide a geometrical construction of these symmetries, based on a horizontality condition on reducible manifolds. This yields globally well-defined scalar and vector topological BRST operators. These operators generate a subalgebra of maximally supersymmetric Yang-Mills theory, which is small enough to be closed off-shell with a finite set of auxiliary fields and large enough to determine the Yang-Mills supersymmetric theory. Poincar\'e supersymmetry is reached in the limit of flat manifolds. The arbitrariness of the gauge functions in BRSTQFTs is thus removed by the requirement of scalar and vector topological symmetry, which also determines the complete supersymmetry transformations in a twisted way. Provided additional Killing vectors exist on the manifold, an equivariant extension of our geometrical framework is provided, and the resulting "equivariant topological field theory" corresponds to the twist of super Yang-Mills theory on Omega backgrounds.Comment: 50 page

Chromosome aberrations, valued as frequency of spontaneous micronuclei, in subjects with suspected presclerodermic Raynaud's phenomenon

OBJECTIVE: To evaluate the prevalence of spontaneous chromosome damage in cultured peripheral lymphocytes of subjects with suspected presclerodermic Raynaud's phenomenon (RP), by means of molecular cytogenetic analysis.METHODS: We studied 20 suspected presclerodermic RP, 20 idiopathic RP and 25 healthy subjects. As marker of chromosome alteration we used the micronucleus assay. All subjects were also classified as ANA-, ACA+ or Scl70+. To identify the mechanism of MN formation, a MN fluorescence in situ hybridisation (FISH) analysis using a pancentromeric DNA probe was also performed.RESULTS: Suspected presclerodermic RP subjects, showed significantly higher MN frequencies than idiopathic RP and controls (39+/-15.2 vs 10+/-2.1 and 9.8+/-3.5 respectively p&lt;0.0001). Interestingly, subjects with idiopathic RP displayed MN frequency comparable to that of controls. Furthermore, ACA+ subjects showed the highest MN frequencies (44+/-8.1) as compared to subjects with different antibody pattern (26+/-7.1).CONCLUSIONS: Our results show the presence of higher levels of chromosomal damage in circulating lymphocytes of suspected presclerodermic RP. They also would suggest a key role of anti-centromere antibody in determining the observed cytogenetic anomalies. FISH analysis indicated that both aneuploidogenic and clastogenic events contribute to the formation of MN observed in suspected presclerodermic RP

Multi-Instanton Calculus and Equivariant Cohomology

We present a systematic derivation of multi-instanton amplitudes in terms of ADHM equivariant cohomology. The results rely on a supersymmetric formulation of the localization formula for equivariant forms. We examine the cases of N=4 and N=2 gauge theories with adjoint and fundamental matter.Comment: 29 pages, one more reference adde

On Combinatorial Expansions of Conformal Blocks

In a recent paper (arXiv:0906.3219) the representation of Nekrasov partition function in terms of nontrivial two-dimensional conformal field theory has been suggested. For non-vanishing value of the deformation parameter \epsilon=\epsilon_1+\epsilon_2 the instanton partition function is identified with a conformal block of Liouville theory with the central charge c = 1+ 6\epsilon^2/\epsilon_1\epsilon_2. If reversed, this observation means that the universal part of conformal blocks, which is the same for all two-dimensional conformal theories with non-degenerate Virasoro representations, possesses a non-trivial decomposition into sum over sets of the Young diagrams, different from the natural decomposition studied in conformal field theory. We provide some details about this intriguing new development in the simplest case of the four-point correlation functions.Comment: 22 page