Renormalizability of N=1/2 Wess-Zumino model in superspace

In this letter we use the spurion field approach adopted in hep-th/0307099 in order to show that by adding F and F^2 terms to the original lagrangian, the N=1/2 Wess-Zumino model is renormalizable to all orders in perturbation theory. We reformulate in superspace language the proof given in the recent work hep-th/0307165 in terms of component fields.Comment: 8 pages, minor change

IDENTIFICATION OF ETHNOMEDICINAL COMPOUNDS AND ANTIMICROBIAL STUDIES OF SALVADORA PERSICA L. (SALVADORACEAE)

Objective: Salvadora persica L. is a dense foliaceous evergreen shrub or small tree with diversified medicinal properties. The objective of this work was to do a comparative study on phytochemical composition between different plant parts of S. persica collected from the southern region of India. Methods: The phytochemical analysis of ethyl acetate fraction of ethanolic extracts from leaves, tender stems and tree bark of S. persica was done by gas chromatography-mass spectrometry/mass spectrometry (GC-MS/MS). Also, the anti-bacterial and anti-fungal activity of extracts was analyzed in vitro by Disc-diffusion method. Results: GC-MS/MS analysis of S. persica showed 29 phytocompounds. Among them, except for eugenol, caryophyllene, benzyl isothiocyanate, oleic acid, and fatty acid, the remaining 24 phytocompounds were newly reported in the present study. For the first time, a maximum amount of benzyl isothiocyanate (73.5%) was identified from tree bark extract of S. persica and this extract showed higher in vitro antimicrobial activity against gram-positive, gram-negative bacteria and fungi than leaves and tender stems. Conclusion: The study demonstrated that benzyl isothiocyanate could be the major antimicrobial component in S. persica

On Instantons and Zero Modes of N=1/2 SYM Theory

We study zero modes of N=1/2 supersymmetric Yang-Mills action in the background of instantons. In this background, because of a quartic antichiral fermionic term in the action, the fermionic solutions of the equations of motion are not in general zero modes of the action. Hence, when there are fermionic solutions, the action is no longer minimized by instantons. By deforming the instanton equation in the presence of fermions, we write down the zero mode equations. The solutions satisfy the equations of motion, and saturate the BPS bound. The deformed instanton equations imply that the finite action solutions have U(1) connections which are not flat anymore.Comment: 9 pages, latex file, added references, minor change

Optical investigation of thermoelectric topological crystalline insulator Pb0.77_{0.77}Sn0.23_{0.23}Se

Pb$_{0.77}$Sn$_{0.23}$Se is a novel alloy of two promising thermoelectric materials PbSe and SnSe that exhibits a temperature dependent band inversion below 300 K. Recent work has shown that this band inversion also coincides with a trivial to nontrivial topological phase transition. To understand how the properties critical to thermoelectric efficiency are affected by the band inversion, we measured the broadband optical response of Pb$_{0.77}$Sn$_{0.23}$Se as a function of temperature. We find clear optical evidence of the band inversion at $160\pm15$ K, and use the extended Drude model to accurately determine a $T^{3/2}$ dependence of the bulk carrier lifetime, associated with electron-acoustic phonon scattering. Due to the high bulk carrier doping level, no discriminating signatures of the topological surface states are found, although their presence cannot be excluded from our data.Comment: 11 pages, 6 figure

N=1/2 gauge theory and its instanton moduli space from open strings in R-R background

We derive the four dimensional N=1/2 super Yang-Mills theory from tree-level computations in RNS open string theory with insertions of closed string Ramond-Ramond vertices. We also study instanton configurations in this gauge theory and their ADHM moduli space, using systems of D3 and D(-1) branes in a R-R background.Comment: 29 pages, 6 figures, JHEP class (included

N=1/2 Supersymmetric gauge theory in noncommutative space

A formulation of (non-anticommutative) N=1/2 supersymmetric U(N) gauge theory in noncommutative space is studied. We show that at one loop UV/IR mixing occurs. A generalization of Seiberg-Witten map to noncommutative and non-anticommutative superspace is employed to obtain an action in terms of commuting fields at first order in the noncommutativity parameter tetha. This leads to abelian and non-abelian gauge theories whose supersymmetry transformations are local and non-local, respectively.Comment: One reference added, published versio

Supersymmetric Nambu−-Jona-Lasinio Model on N=1/2{\cal N}=1/2 four-dimensional Non(anti)commutative Superspace

We construct the Lagrangian of the ${\cal N}=1$ four-dimensional generalized supersymmetric Nambu$-$Jona-Lasinio (SNJL) model, which has ${\cal N}=1/2$ supersymmetry (SUSY) on non(anti)commutative superspace. A special attention is paid to the examination on the nonperturbative quantum dynamics: The phenomenon of dynamical-symmetry-breaking/mass-generation on the deformed superspace is investigated. The model Lagrangian and the method of SUSY auxiliary fields of composites are examined in terms of component fields. We derive the effective action, examine it, and solve the gap equation for self-consistent mass parameters.Comment: 16 pages, TeX mistakes corrected, accepted for publication in JHEP, 25 Jan. 200

U(N) Instantons on N=1/2 superspace -- exact solution & geometry of moduli space

We construct the exact solution of one (anti)instanton in N=1/2 super Yang-Mills theory defined on non(anti)commutative superspace. We first identify N = 1/2 superconformal invariance as maximal spacetime symmetry. For gauge group U(2), SU(2) part of the solution is given by the standard (anti)instanton, but U(1) field strength also turns out nonzero. The solution is SO(4) rotationally symmetric. For gauge group U(N), in contrast to the U(2) case, we show that the entire U(N) part of the solution is deformed by non(anti)commutativity and fermion zero-modes. The solution is no longer rotationally symmetric; it is polarized into an axially symmetric configuration because of the underlying non(anti)commutativity. We compute the `information metric' of one (anti) instanton. We find that moduli space geometry is deformed from hyperbolic space (Euclidean anti-de Sitter space) in a way anticipated from reduced spacetime symmetry. Remarkably, the volume measure of the moduli space turns out to be independent of the non(anti)commutativity. Implications to D-branes in Ramond- Ramond flux background and Maldacena's gauge-gravity correspondence are discussed.Comment: 39 pages, 3 figures, JHEP style; v2. typos corrected + a paragraph adde

Scattering Amplitudes and Toric Geometry

In this paper we provide a first attempt towards a toric geometric interpretation of scattering amplitudes. In recent investigations it has indeed been proposed that the all-loop integrand of planar N=4 SYM can be represented in terms of well defined finite objects called on-shell diagrams drawn on disks. Furthermore it has been shown that the physical information of on-shell diagrams is encoded in the geometry of auxiliary algebraic varieties called the totally non negative Grassmannians. In this new formulation the infinite dimensional symmetry of the theory is manifest and many results, that are quite tricky to obtain in terms of the standard Lagrangian formulation of the theory, are instead manifest. In this paper, elaborating on previous results, we provide another picture of the scattering amplitudes in terms of toric geometry. In particular we describe in detail the toric varieties associated to an on-shell diagram, how the singularities of the amplitudes are encoded in some subspaces of the toric variety, and how this picture maps onto the Grassmannian description. Eventually we discuss the action of cluster transformations on the toric varieties. The hope is to provide an alternative description of the scattering amplitudes that could contribute in the developing of this very interesting field of research.Comment: 58 pages, 25 figures, typos corrected, a reference added, to be published in JHE