Inflation in a two 3-form fields scenario

A setting constituted by $\mathbb{N}$ 3-form fields, without any direct interaction between them, minimally coupled to gravity, is introduced in this paper as a framework to study the early evolution of the universe. We focus particularly on the two 3-forms case. An inflationary scenario is found, emerging from the coupling to gravity. More concretely, the fields coupled in this manner exhibit a complex interaction, mediated by the time derivative of the Hubble parameter. Our investigation is supported by means of a suitable choice of potentials, employing numerical methods and analytical approximations. In more detail, the oscillations on the small field limit become correlated, and one field is intertwined with the other. In this type of solution, a varying sound speed is present, together with the generation of isocurvature perturbations. The mentioned features allow to consider an interesting model, to test against observation. It is subsequently shown how our results are consistent with current CMB data (viz.Planck and BICEP2).Comment: Version accepted in JCAP. 22 pages, 12 figures, new refs adde

Structure Effects on Coulomb Dissociation of 8^8B

Coulomb Dissociation provides an alternative method for determining the radiative capture cross sections at astrophysically relevant low relative energies. For the breakup of $^8$B on $^{58}$Ni, we calculate the total Coulomb Dissociation cross section and the angular distribution for E1, E2 and M1. Our calculations are performed first within the standard first order semiclassical theory of Coulomb Excitation, including the correct three body kinematics, and later including the projectile-target nuclear interactions.Comment: 6 pages, proceedings from International Workshop on RNB, Puri, India, January 1998 - to be published in J. Phys.

On the particle spectrum and the conformal window

We study the SU(3) gauge theory with twelve flavours of fermions in the fundamental representation as a prototype of non-Abelian gauge theories inside the conformal window. Guided by the pattern of underlying symmetries, chiral and conformal, we analyze the two-point functions theoretically and on the lattice, and determine the finite size scaling and the infinite volume fermion mass dependence of the would-be hadron masses. We show that the spectrum in the Coulomb phase of the system can be described in the context of a universal scaling analysis and we provide the nonperturbative determination of the fermion mass anomalous dimension gamma*=0.235(46) at the infrared fixed point. We comment on the agreement with the four-loop perturbative prediction for this quantity and we provide a unified description of all existing lattice results for the spectrum of this system, them being in the Coulomb phase or the asymptotically free phase. Our results corroborate the view that the fixed point we are studying is not associated to a physical singularity along the bare coupling line and estimates of physical observables can be attempted on either side of the fixed point. Finally, we observe the restoration of the U(1) axial symmetry in the two-point functions.Comment: 40 pages, 22 figure

One,Two,Zero: Scales of Strong Interactions

We discuss our results on QCD with a number of fundamental fermions ranging from zero to sixteen. These theories exhibit a wide array of fascinating phenomena which have been under close scrutiny, especially in recent years, first and foremost is the approach to conformality. To keep this review focused, we have chosen scale generation, or lack thereof as a guiding theme, however the discussion will be set in the general framework of the analysis of the phases and phase transitions of strong interactions at zero and nonzero temperature.Comment: 15 pages, prepared for IJMPA Special Issue 'Recent Nonperturbative Developments in QCD-like Theories

Chiral symmetry restoration in QCD with many flavours

We discuss the phases of QCD in the parameter space spanned by the number of light flavours and the temperature with respect to the realisation of chiral and conformal symmetries. The intriguing interplay of these symmetries is best studied by means of lattice simulations, and some selected results from our recent work are presented here.Comment: 10 pages, proceedings of the 9th International Workshop on Critical Point and Onset of Deconfinement, 17-21 November, 2014, ZiF, Bielefeld, German

Nuclear reaction studies of unstable nuclei using relativistic mean field formalisms in conjunction with Glauber model

We study nuclear reaction cross-sections for stable and unstable projectiles and targets within Glauber model, using densities obtained from various relativistic mean field formalisms. The calculated cross-sections are compared with the experimental data in some specific cases. We also evaluate the differential scattering cross-sections at several incident energies, and observe that the results found from various densities are similar at smaller scattering angles, whereas a systematic deviation is noticed at large angles. In general, these results agree fairly well with the experimental data.Comment: 9 pages, 7 figures, submitted to PR

A Note on the Picard-Fuchs Equations for N=2 Seiberg-Witten Theories

A concise presentation of the PF equations for N=2 Seiberg-Witten theories for the classical groups of rank r with N_f massless hypermultiplets in the fundamental representation is provided. For N_f=0, all r PF equations can be given in a generic form. For certain cases with N_f\neq zero, not all equations are generic. However, in all cases there are at least r-2 generic PF equations. For these cases the classical part of the equations is generic, while the quantum part can be formulated using a method described in a previous paper by the authors, which is well suited to symbolic computer calculations.Comment: 25 pages, Latex; some new references adde

A Frustrated 3-Dimensional Antiferromagnet: Stacked J1−J2J_{1}-J_{2} Layers

We study a frustrated 3D antiferromagnet of stacked $J_1 - J_2$ layers. The intermediate 'quantum spin liquid' phase, present in the 2D case, narrows with increasing interlayer coupling and vanishes at a triple point. Beyond this there is a direct first-order transition from N{\' e}el to columnar order. Possible applications to real materials are discussed.Comment: 11 pages,7 figure

Temperature effects on dislocation core energies in silicon and germanium

Temperature effects on the energetics of the 90-degree partial dislocation in silicon and germanium are investigated, using non-equilibrium methods to estimate free energies, coupled with Monte Carlo simulations. Atomic interactions are described by Tersoff and EDIP interatomic potentials. Our results indicate that the vibrational entropy has the effect of increasing the difference in free energy between the two possible reconstructions of the 90-degree partial, namely, the single-period and the double-period geometries. This effect further increases the energetic stability of the double-period reconstruction at high temperatures. The results also indicate that anharmonic effects may play an important role in determining the structural properties of these defects in the high-temperature regime.Comment: 8 pages in two-column physical-review format with six figure

Slave boson model for two-dimensional trapped Bose-Einstein condensate

A system of N bosons in a two-dimensional harmonic trap is considered. The system is treated in term of the slave boson representation for hard-core bosons which is valid in the arbitrary density regimes. I discuss the consequences of higher order interactions on the density profiles by mapping the slave boson equation to the known Kohn-Sham type equation within the density functional scheme.Comment: 12 pages, 3 figures. Submitted to J. Phys. B : At. mol. opt. phy