arXiv subjects

Ajit M. Srivastava

Publications and source records attributed to Ajit M. Srivastava.

62 records · Page 4Linked to original sources

arXiv1997

Vortex-Antivortex Pair Production in a First Order Phase Transition

We carry out numerical simulation of a first order phase transition in 2+1 dimensions by randomly nucleating bubbles, and study the formation of global U(1) vortices. Bubbles grow and coalesce and vortices are formed at junctions of bubbles via standard Kibble mechanism as well as due to a new mechanism, recently proposed by us, where defect-antidefect pairs are produced due to field oscillations. We make a comparative study of the contribution of both of these mechanisms for vortex production. We find that, for high nucleation rate of bubbles, vortex-antivortex pairs produced via the new mechanism have overlapping configurations, and annihilate quickly; so only those vortices survive till late which are produced via the Kibble mechanism. However, for low nucleation rates, bubble collisions are energetic enough to lead to many well separated vortex-antivortex pairs being produced via the new mechanism. For example, in a simulation involving nucleation of 20 bubbles, a total of 14 non-overlapping vortices and antivortices formed via this new mechanism of pair creation (6 of them being very well separated), as compared to 6 vortices and antivortices produced via the Kibble mechanism. Our results show the possibility that in extremely energetic bubble collisions, such as those in the inflationary models of the early Universe, this new mechanism may drastically affect the defect production scenario.

hep-ph↗

arXiv1996

Defect-Antidefect pair production via field oscillations

We show that the mechanism of vortex-antivortex pair production via field oscillations, earlier proposed by two of us for systems with first order transitions in presence of explicit symmetry breaking, is in fact very generally applicable. We further argue that this mechanism applies to all sorts of topological defects (e.g. strings, monopoles, textures) and for second order transitions as well. We also show this explicitly by numerically simulating production of vortex-antivortex pairs by decay of bubble walls for a U(1) global theory in the absence of any explicit symmetry breaking.

hep-ph↗

arXiv1995

Formation of Topological Defects with Explicit Symmetry Breaking

We demonstrate a novel mechanism for the formation of topological defects in a first order phase transition for theories in the presence of small explicit symmetry breaking terms. We carry out numerical simulations of collisions of two bubbles in 2+1 dimensions for a field theory where U(1) global symmetry is spontaneously as well as explicitly broken. In the coalesced region of bubble walls, field oscillations result in the decay of the coalesced portion in a large number of defects (e.g. ten vortices and anti-vortices). We discuss the implications of our results for axionic strings in the early Universe, for baryon formation in quark-gluon plasma, and for electric or magnetic field.

hep-ph↗

arXiv1994

Baryon - Antibaryon Production by Disordered Chiral Condensates

We investigate the production of baryons and antibaryons in the central rapidity region of high energy nuclear collisions within the framework of the Skyrme model taking into account the effects of explicit chiral symmetry breaking. We argue that the formation of disordered chiral condensates may lead to enhanced baryon-antibaryon production at low transverse momentum.

hep-ph↗

arXiv1994

The Proximal Chiral Phase Transition

We consider the form of the chiral symmetry breaking piece of the effective potential in the linear sigma model. Surprisingly, it allows for a second local minimum at both zero and finite temperature. Even though chiral symmetry is not exact, and therefore is not restored in a true phase transition at finite temperature, this second minimum can nevertheless mimic many of the effects of a first order phase transition. We derive a lower limit on the height of the second minimum relative to the global minimum based on cosmological considerations; this limit is so weak as to be practically nonexistent. In high energy nuclear collisions, it may lead to observable effects in Bose-Einstein interferometry due to domain walls and to coherent pion emission.

hep-ph↗

arXiv1994

Towards Observing the Intercommutation of Flux Tubes in Superconductors

We propose a simple experiment to investigate the intercommutation of flux tubes in type II superconductors. Using this method the intercommutation of strings can be observed directly and the dependence of intercommutation on the angle of crossing of strings can also be analyzed.

cond-mat↗

arXiv1993

Propogation of Electromagnetic Waves in the Core of a String Defect in Liquid Crystals

We investigate the propagation of electromagnetic waves in the core of a winding number one string defect with isotropic core in nematic liquid crystals. We numerically solve wave equations for the TE mode and show the existence of guided modes arising due to the variation of the refractive index as a function of the scalar order parameter.

cond-mat↗

arXiv1992

On the Production of Flux Vortices and Magnetic Monopoles in Phase Transitions

We examine the basic assumptions underlying a scenario due to Kibble that is widely used to estimate the production of topological defects. We argue that one of the crucial assumptions, namely the geodesic rule, although completely valid for global defects, becomes ill defined for the case of gauged defects. We address the issues involved in formulating a suitable geodesic rule for this case and argue that the dynamics plays an important role in the production of gauge defects.

hep-ph↗