119399108
LAGRANGIAN AND HAMILTONIAN FORMULATIONS OF HIGHER ORDER CHERN–SIMONS THEORIES
We consider models involving the higher (third) derivative extension of the Abelian Chern–Simons (CS) topological term in D = 2 + 1 dimensions. The polarization vectors in these models reveal an identical structure with the corresponding expressions for usual models which contain, at most, quadratic structures. We also investigate the Hamiltonian structure of these models and show how Wigner's little group acts as a gauge generator.
15230645
Critical generation of soliton mode in a gauged O(3) sigma model with interpolating potential
We show that a new soliton mode is generated in a gauged sigma model with interpolating potential when the interpolation parameter decreases below a critical value. pradip@boson.bose.res.in kumar@boson.bose.res.in Recently a class of gauged O(3) sigma models in three dimensions have been studied [1, 2, 3, 4, 5] where a U(1) subgroup of the O(3) symmetry of the model was gauged by coupling the sigma model fields with a gauge field through the corresponding U(1) current. This is different from the minimal coupling via the topological current discussed previously [6]. The motivation behind the new gauged O(3) sigma models was to break the scale invariance of the self dual solutions of the usual O(3) sigma model [7]. Initially the gauge field dynamics was assumed to be dictated by the Maxwell term [1]. Later the extension of the model with the Chern Simons coupling was investigated [2]. A particular form of self interaction was required to be included in these models in order to saturate the Bogomol’nyi bounds [8]. The form of the assumed self interaction potential is of crucial importance. The minima of the potential determine the vaccum structure of the theory. The solutions change remarkably when the vaccum structure exhibits spontaneous breaking of the symmetry of the gauge group. Thus it was demonstrated that the observed degeneracy of the solutions of [1, 2] is lifted when potentials with symmetry breaking minima were incorporated [4, 5]. A generalisation of the models [1, 2] was proposed in [3]where an adjustable real parameter v was introduced in the expression of the self interaction potential. Detailed solutions of the model with the C S coupling were provided. The parameter v interpolates between the symmetric and symmetry breaking phases. The inclusion of such adjustable potential in the corresponding Maxwell coupled model was conjectured, but not fully explored. In this letter we show that this generalisation indeed leads to certain important consequences. The most interesting outcome is a kind of ’critical phenomenon’ where a new self dual soliton mode emerges when the parameter v decreases below v = 1. It will be useful to start with a brief review of the nonlinear O(3) sigma model [7]. The lagrangian of the model is given by, L = 1 2 ∂μφ · ∂ φ (1) Here φ is a triplet of scalar fields constituting a vector in the internal space with unit norm φa = na · φ, (a = 1, 2, 3) (2) φ · φ = φaφa = 1 (3) The vectors na constitute a basis of unit orthogonal vectors in the internal space. We work in the Minkowskian space time with the metric tensor diagonal, gμν = (1,−1,−1). The finite energy solutions of the model (1) satisfies the boundary condition limφ = φa(0) (4) at physiacal infinity. The condition (4) corresponds to one point compactification of the physical infinity. The physical space R2 becomes topologically equivalent to S2 due to this compactification. The static finite energy solutions of the model are then maps from this sphere to the internal sphere. Such solutions are classified by the homotopy [9]
120583515
BIANCHI TYPE-II COSMOLOGICAL MODELS WITH CONSTANT DECELERATION PARAMETER
A special law of variation for Hubble's parameter in anisotropic space–time models that yields a constant value of the deceleration parameter is presented. Also, a spatially homogeneous and anisotropic but locally rotationally symmetric (LRS) Bianchi type-II cosmological model is studied with a perfect fluid and constant deceleration parameter. Assuming the equation of state p = γρ, where 0≤γ≤1, and using a special law of variation for the Hubble parameter, we are able to construct many new solutions to Einstein's field equations of LRS Bianchi type-II for four different physical models (dust, radiation, Zel'dovich and vacuum). We discuss the solutions with power-law and exponential expansion and examine a particular class of models. A detailed study of kinematic, geometrical and observational properties is carried out.
14887515
S-duality of the Leigh-Strassler Deformation via Matrix Models
We investigate an exactly marginal = 1 supersymmetric deformation of SU(N) = 4 supersymmetric Yang-Mills theory discovered by Leigh and Strassler. We use a matrix model to compute the exact superpotential for a further massive deformation of the U(N) Leigh-Strassler theory. We then show how the exact superpotential and eigenvalue spectrum for the SU(N) theory follows by a process of integrating-in. We find that different vacua are related by an action of the SL(2,) modular group on the bare couplings of the theory extending the action of electric-magnetic duality away from the = 4 theory. We perform non-trivial tests of the matrix model results against semiclassical field theory analysis. We also show that there are interesting points in parameter space where condensates can diverge and vacua disappear. Based on the matrix model results, we propose an exact elliptic superpotential to describe the theory compactified on a circle of finite radius.
118683185
A comparative study of model ingredients: Fragmentation in heavy-ion collisions using quantum molecular dynamics model
We aim to understand the role of NN cross-sections, equation of state as well as different model ingredients such as width of Gaussian, clusterization range and different clusterization algorithms in multifragmentation using quantum molecular dynamics model. We notice that all model ingredients have sizable effect on the fragment pattern.
122529836
Anisotropic dark energy models with constant deceleration parameter
We consider a spatially homogeneous and totally anisotropic Bianchi-I space-time with perfect fluid (dark matter and standard visible matter) and anisotropic dark energy, which has dynamical energy density. The two sources are assumed to interact minimally and therefore their energy momentum tensors are conserved separately. Using suitable physical assumptions, the field equations are solved exactly. Various dark energy models are studied and it is found that quintessence model is suitable for describing the present evolution of the universe. The geometrical and kinematical features of the models and the behavior of the anisotropy of the dark energy, are examined in detail.
120097279
Thirring fermions at high temperature
A Green's-function method is used to study the thermodynamic properties of self-interacting massless dimension and one time dimension. It is shown that the exact expression can be obtained for the thermodynamic one-particle Green's function for the case where the dimensionless chemical potential $mu$ = 0, which is identical with the corresponding field-theoretic Green's function. The number density is obtained as an infinite sum. It exhibits a peculiar peaked behavior as a function of momentum. The energy, however, is a continuous function of temperature. (AIP)