Negative differential resistance in nanoscale transport in the Coulomb blockade

Motivated by recent experiments, we have studied transport behavior of coupled quantum dot systems in the Coulomb blockade regime using the master (rate) equation approach. We explore how electron-electron interactions in a donor-acceptor system, resembling weakly coupled quantum dots with varying charging energy, can modify the systems response to an external bias, taking it from normal Coulomb blockade behavior to negative differential resistance (NDR) in the curent-voltage characteristics

Hot Nuclear Matter : A Variational Approach

We develop a nonperturbative technique in field theory to study properties of infinite nuclear matter at zero temperature as well as at finite temperatures. Here we dress the nuclear matter with off-mass shell pions. The techniques of thermofield dynamics are used for finite temperature calculations. Equation of state is derived from the dynamics of the interacting system in a self consistent manner. The transition temperature for nuclear matter appears to be around 15 MeV.Comment: 16 pages, IP/BBSR/91-3

Vanishing corrections on the intermediate scale and implications for unification of forces

In two-step breaking of a class of grand unified theories including SO(10),we prove a theorem showing that the scale $M_I$ where the Pati-Salam gauge symmetry with parity breaks down to the standard gauge group,has vanishing corrections due to all sources emerging from higher scales $\mu >M_I$ such as the one-loop and all higher loop effects,the GUT-threshold,gravitational smearing,and string threshold effects. Implications of such a scale for the unification of gauge couplings with small Majorana neutrino masses are discussed.In string inspired SO(10) we show that $M_I \simeq 5\times 10^{12}$,needed for neutrino masses,with the GUT scale $M_U \simeq M_{str}$ can be realized provided certain particle states in the predicted spectum are light.Comment: 21 pages, Late

Neutron matter - Quark matter phase transition and Quark star

We consider the neutron matter quark matter phase transition along with possible existence of hybrid quark stars. The equation of state for neutron matter is obtained using a nonperturbative method with pion dressing of the neutron matter and an analysis similar to that of symmetric nuclear matter. The quark matter sector is treated perturbatively in the small distance domain. For bag constant $B^{1/4}$=148 MeV, a first order phase transition is seen. In the context of neutron quark hybrid stars, Tolman-Oppenheimer-Volkoff equations are solved using the equations of state for quark matter and for neutron matter with a phase transition as noted earlier. Stable solutions for such stars are obtained with the Chandrasekhar limit as 1.58 $M_\odot$ and radius around 10 km. The bulk of the star is quark matter with a thin crust of neutron matter of less than a kilometer.Comment: 28 pages including 9 figures, Revtex, IP/BBSR/92-8

Radiative stability of neutrino-mass textures

Neutrino-mass textures proposed at high-scales are known to be unstable against radiative corrections especially for nearly degenerate eigen values. Within the renormalization group constraints we find a mechanism in a class of gauge theories which guarantees reproduction of any high-scale texture at low energies with radiative stability. We also show how the mechanism explains solar and atmospheric neutrino anomalies through the bimaximal texture at high scale.Comment: 4 pages REVTEX, 1 Postscript fi

A Blind Signature Scheme using Biometric Feature Value

Blind signature has been one of the most charming research fields of public key cryptography through which authenticity, data integrity and non-repudiation can be verified. Our research is based on the blind signature schemes which are based on two hard problems – Integer factorization and discrete logarithm problems. Here biological information like finger prints, iris, retina DNA, tissue and other features whatever its kind which are unique to an individual are embedded into private key and generate cryptographic key which consists of private and public key in the public key cryptosystem. Since biological information is personal identification data, it should be positioned as a personal secret key for a system. In this schemes an attacker intends to reveal the private key knowing the public key, has to solve both the hard problems i.e. for the private key which is a part of the cryptographic key and the biological information incorporated in it. We have to generate a cryptographic key using biometric data which is called biometric cryptographic key and also using that key to put signature on a document. Then using the signature we have to verify the authenticity and integrity of the original message. The verification of the message ensures the security involved in the scheme due to use of complex mathematical equations like modular arithmetic and quadratic residue as well

New Uncertainties in QCD-QED Rescaling Factors using Quadrature Method

In this paper we briefly outline the quadrature method for estimating uncertainties in a function of several variables and apply it to estimate the numerical uncertainties in QCD-QED rescaling factors. We employ here the one-loop order in QED and three-loop order in QCD evolution equations of fermion mass renormalization. Our present calculations are found to be new and also reliable compared to the earlier values employed by various authors.Comment: 14 page

Low-energy formulas for neutrino masses with tan⁡β\tan \beta-dependent hierarchy

Using radiative correction and seesaw mechanism,we derive analytic formulas for neutrino masses in SUSY unified theories exhibiting, for the first time, a new hierarchial relation among them.The new hierarchy is found to be quite significant especially for smaller values of $\tan\beta$.Comment: 10 pages,REVTEX, no figures,typographical errors rectifie

Type II Seesaw Dominance in Non-supersymmetric and Split Susy SO(10) and Proton Life Time

Recently type II seesaw dominance in a supersymmetric SO(10) framework has been found useful in explaining large solar and atmospheric mixing angles as well as larger values of $theta_{13}$ while unifying quark and lepton masses. An important question in these models is whether there exists consistency between coupling unification and type II seesaw dominance. Scenarios where this consistency can be demonstrated have been given in a SUSY framework. In this paper we give examples where type II dominance occurs in SO(10) models without supersymmetry but with additional TeV scale particles and also in models with split-supersummetry. Grand unification is realized in a two-step process via breaking of SO(10) to SU(5) and then to a TeV scale standard model supplemented by extra fields and an SU(5) Higgs multiplet ${15}_H$ at a scale about $10^{12}$ GeV to give type-II seesaw. The predictions for proton lifetime in these models are in the range $\tau_p^0 = 2\times 10^{35}$ yrs. to $\tau_p^0 = 6\times 10^{35}$ yrs.. A number of recent numerical fits to GUT-scale fermion masses can be accommodated within this model.Comment: 7 pages LaTeX, 3 figures, related areas: hep-ex, hep-th, astro-ph; Reference added, typo corrected, version to appear in Physical Review