arXiv subjects

P. K. Mishra

Publications and source records attributed to P. K. Mishra.

26 records · Page 2Linked to original sources

arXiv2006

Calculation of the Masses and the Running Masses of the Quarks and Leptons from Electroweak to Supersymmetric Grand Unification Mass

We make a systematic theoretical analysis of the masses and their variation with energy by solving the renormalization group equation (RGE) in the Minimal Supersymmetric Standard Model (MSSM). The unification fermion masses of around 115 GeV at GeV scale has been derived by Deo and Maharana. Here we undertake the unfinished but the important task of calculating the masses and their running. The unification mass and group theoretic constants for the model are known. The top mass and its descent is studied very carefully. We find that the Ramond,Roberts and Ross value of the Wolfenstein parameter is nearly equal to 0.22. When raised to integral powers, the whole mass spectra of the remaining eleven fermions are obtained. We deduce formulas and plot them for all the 12 fermions as they vary from $t=log \fracμ{M_z}=0$ to $t_X=33$; the GUT mass being $M_X=2.2\times 10^{16}$ GeV.

hep-ph↗

arXiv2005

Modification of intergrain connectivity, upper critical field anisotropy, and critical current density in ion irradiated MgB2 films

We study the effect of 100 MeV Silicon and 200 MeV Gold ion irradiation on the inter and intra grain properties of superconducting thin films of Magnesium Diboride. Substantial decrease in inter-grain connectivity is observed, depending on irradiation dose and type of ions used. We establish that modification of sigma band scattering mechanism, and consequently the upper critical field and anisotropy, depends on the size and directional properties of the extrinsic defects. Post heavy ion irradiation, the upper critical field shows enhancement at a defect density that is five orders of magnitude less compared to neutron irradiation. The critical current density however is best improved through light ion irradiation.

cond-mat.supr-con↗

arXiv2005

Solutions of the Renormalisation Group Equation in Minimal Supersymmetric Standard Model

Renormalisation Group Equation(RGE) for color and top couplings sector of MSSM has been solved. The mass of the top comes out to be 180.363$\pm$ 10.876 GeV and $β_{top}$=$\fracπ{2}$. It is conjectured that the masses of the other 11 fermions and the CKM phase angle $ϕ$ can be theoretically estimated. The results confirm the fact that the quarks and leptons have been created having equal mass $\sim$ 115 GeV at the MSSM GUT scale $\sim ~2.2\times 10^{16}$ GeV.

hep-ph↗

arXiv2004

Force-induced desorption of a linear polymer chain adsorbed on an attractive surface

We consider a model of self-avoiding walk on a lattice with on-site repulsion and an attraction for every vertex of the walk visited on the surface to study force-induced desorption of a linear polymer chain adsorbed on an attractive surface and use the exact enumeration technique for analyzing how the critical force for desorption $f_c(T)$ depends on the temperature. The curve $f_c(T)$ gives the boundary separating the adsorbed phase from the desorbed phase. Our results show that in two dimensions where surface is a line the force $f_c(T)$ increases monotonically as temperature is lowered and becomes almost constant at very low temperatures. In case of three-dimensions we, however, find re-entrance, i. e. $f_c(T)$ goes through a maximum as temperature is lowered. The behaviour of the polymer chain at different values of temperature and force is examined by calculating the probability distribution of the height from the surface of the vertex at which external force is applied.

cond-mat.stat-mech↗

arXiv2004

Effect of confinement on coil-globule transition

The equilibrium thermodynamic properties of a linear polymer chain confined to a space between two impenetrable walls (lines) at a distance $D$ under various solvent conditions have been studied using series analysis and exact enumeration technique. We have calculated the end to end distance of polymer chain, which shows a non-monotonic behaviour with inter wall ^M separation $D$. The density distribution profile shows a maxima at a particular value of ${(D=)}D^*$. Around this $D^*$, our results show that the collapse^M transition occurs at higher temperature as compared to its bulk value of 2d and 3d. The variation of $θ-$ temperature with $D$ shows a re-entrance behaviour. We also calculate the force of compression exerted by the walls (lines) on the polymer.

cond-mat.stat-mech↗

arXiv2002

A simple and exactly solvable model for a semiflexible polymer chain interacting with a surface

We use the lattice model of directed walks to investigate the conformational as well as the adsorption properties of a semiflexible homopolymer chain immersed in a good solvent in two and three dimensions. To account for the stiffness in the chain we have introduced energy barrier for each bend in the walk and have calculated the persistent length as a function of this energy. For the adsorption on an impenetrable surface perpendicular to the preferred direction of the walk we have solved the model exactly and have found the critical value of the surface attractions for the adsorption in both two and three dimensions. We have also enumerated all the possible walks on square and cubic lattices for the number of steps N <= 30 for two-dimensions and N <= 20 for three dimensions and have used ratio method for extrapolation. The transition located using this method is in excellent agreement with the results found from the analytical method.

cond-mat.stat-mech↗

arXiv2000

Disordered Type-II Superconductors: A Universal Phase Diagram for Low-T$_c$ Systems

A universal phase diagram for weakly pinned low-T$_c$ type-II superconductors is revisited and extended with new proposals. The low-temperature ``Bragg glass'' phase is argued to transform first into a disordered, glassy phase upon heating. This glassy phase, a continuation of the high-field equilibrium vortex glass phase, then melts at higher temperatures into a liquid. This proposal provides an explanation for the anomalies observed in the peak effect regime of 2H-NbSe$_2$ and several other low-T$_c$ materials which is independent of the microscopic mechanisms of superconductivity in these systems.

cond-mat.supr-con↗

arXiv1999

Peak Effect in Ca$_3$Rh$_4$Sn$_{13}$ : Vortex Phase Diagram and Evidences for Stepwise Amorphization of Flux Line Lattice

The Peak Effect (PE) regime in a single crystal of Ca$_3$Rh$_4$Sn$_{13}$ has been investigated in detail via ac susceptibility as well as dc magnetization measurements. The PE region comprises two discontinuous first order like transitions, located near its onset and peak positions and reflects a stepwise fracturing of the flux line lattice (FLL). This scenario can be construed as an alternative to a scheme involving the appearance of Generalized Fulde-Ferrel-Larkin-Ovchinnikov (GFFLO) state as considered in the case of PE phenomenon in isostructural Yb$_3$Rh$_4$Sn$_{13}$ system. The procedure of thermal cycling across the onset position of PE produces an open hysteresis loop, which is consistent with the notion of the fracturing of the FLL. A study of thermomagnetic history dependence of different metastable vortex states shows the path dependence in the critical current density J_c(H,T) over a large part of the (H,T) parameter space. The path dependence in J_c ceases above the peak position of the PE, suggesting a complete amorphization and the loss of long range correlations of the FLL at (T_p, H_p) line. A plausible vortex phase diagram has been illustrated for Ca$_3$Rh$_4$Sn$_{13}$n and phases like an elastic solid, a plastic solid, a pinned amorphous and an unpinned amorphous states have been identified.

cond-mat.supr-con↗