arXiv subjects

A. M. Srivastava

Publications and source records attributed to A. M. Srivastava.

7 recordsLinked to original sources

arXiv2026

Role of the Nephelauxetic Effect in Engineering Mn4+ Luminescence Kinetics for Lifetime-Based Thermometry

Although the considerable potential of luminescence thermometry based on emission kinetics has been widely demonstrated, reliable tools for the intentional prediction of thermometric performance remain limited. To address this challenge, the present work introduces an approach that enables a theoretical description of the 2E state lifetime of Mn4+ ions, as well as the absolute and relative sensitivities, in terms of the nephelauxetic effect within the group of double perovskites: Sr2InNbO6, Sr2InTaO6, Ba2InTaO6, and Ba2InNbO6. Our results clearly show that, contrary to common assumptions, the Dq/B ratio is not the primary factor governing either the spectroscopic behavior of Mn4+ ions or the thermometric performance of Mn4+-doped phosphors. Instead, the nephelauxetic beta1 parameter plays the dominant role. The empirical analysis carried out in this study led to the development of a predictive model that enables estimation of SAMAX and SRMAX values based exclusively on beta1. This methodology represents a significant step toward the rational design of lifetime-based luminescence thermometers with predefined thermometric characteristics tailored to the requirements of specific applications.

cond-mat.mtrl-sci↗

arXiv2006

Working Group Report: Heavy-Ion Physics and Quark-Gluon Plasma

This is the report of Heavy Ion Physics and Quark-Gluon Plasma at WHEPP-09 which was part of Working Group-4. Discussion and work on some aspects of Quark-Gluon Plasma believed to have created in heavy-ion collisions and in early universe are reported.

hep-ph↗

arXiv2004

Working Group Report: Neutrino and Astroparticle Physics

This is the report of neutrino and astroparticle physics working group at WHEPP-8. We present the discussions carried out during the workshop on selected topics in the above fields and also indicate progress made subsequently. The neutrino physics subgroup studied the possibilites of constraining neutrino masses, mixing and CPT violation in lepton sector from future experiments. Neutrino mass models in the context of abelian horizontal symmetries, warped extra dimensions and in presence of triplet Higgs were studied. Effect of threshold corrections on radiative magnification of mixing angles was investigated. The astroparticle physics subgroup focused on how various particle physics inputs affect the CMBR fluctuation spectrum, and on brane cosmology. This report also contains an introduction on how to use the publicly available code CMBFAST to calculate the CMBR fluctuations.

hep-ph↗

arXiv1999

Forming a Single, Large, DCC Domain in a Heavy-Ion Collision

We demonstrate the possibility of forming a single, large domain of disoriented chiral condensate (DCC) in a heavy-ion collision. In our scenario, rapid initial heating of the parton system provides a driving force for the chiral field, moving it away from the true vacuum and forcing it to go to the opposite point on the vacuum manifold. This converts the entire hot region into a single DCC domain. Subsequent rolling down of the chiral field to its true vacuum will then lead to emission of a large number of (approximately) coherent pions. The requirement of suppression of thermal fluctuations to maintain the (approximate) coherence of such a large DCC domain, favors three dimensional expansion of the plasma over the longitudinal expansion even at very early stages of evolution. This also constrains the maximum temperature of the system to lie within a window. We roughly estimate this window to be about 200 - 400 MeV. These results lead us to predict that extremely high energy collisions of {\it very small nuclei} (possibly hadrons) are better suited for observing signatures of a large DCC. Another possibility is to focus on {\it peripheral} collisions of heavy nuclei.

hep-ph↗

arXiv1992

The Cosmological Kibble Mechanism in the Laboratory: String Formation in Liquid Crystals

We have observed the production of strings (disclination lines and loops) via the Kibble mechanism of domain (bubble) formation in the isotropic to nematic phase transition of a sample of uniaxial nematic liquid crystal. The probablity of string formation per bubble is measured to be $0.33 \pm 0.01$. This is in good agreement with the theoretical value $1/ π$ expected in two dimensions for the order parameter space $S^2/{\bf Z}_2$ of a simple uniaxial nematic liquid crystal.

hep-ph↗

arXiv1992

Topological Spin-Statistics Theorem for Strings

Recently, a topological proof of the spin-statistics Theorem has been proposed for a system of point particles which does not require relativity or field theory, but assumes the existence of antiparticles. We extend this proof to a system of string loops in three space dimensions and show that by assuming the existence of antistring loops, one can prove a spin-statistics theorem for these string loops. According to this theorem, all unparametrized strings(such as flux tubes in superconductors and cosmic strings ) should be quantized as bosons. Also, as in the point particle case, we find that the theorem excludes nonabelian statistics.

hep-th↗

arXiv1991

Chern-Simons Dynamics and the Quantum Hall Effect

Theoretical developments during the past several years have shown that large scale properties of the Quantum Hall system can be successfully described by effective field theories which use the Chern-Simons interaction. In this article, we first recall certain salient features of the Quantum Hall Effect and their microscopic explanation. We then review one particular approach to their description based on the Chern-Simons Lagrangian and its variants.

hep-th↗