Results for "Surjeet Singh"

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Anomalous lattice contraction and emergent electronic phases in Bi-doped Eu$_2$Ir$_2$O$_7$Feb 08 2019We study the pyrochlore series (Eu$_{1-x}$Bi$_x$)$_2$Ir$_2$O$_7$ for $ 0 \leq x \leq 1$. We show that for small $x$, the lattice undergoes an anomalous contraction but the all-in/all-out and metal-to-insulator transitions remain robust, and the resistivity ... More
Finite-size effects in the quasi-one-dimensional quantum magnets Sr$_{2}$CuO$_{3}$, Sr$_{2}$Cu$_{0.99}$M$_{0.01}$O$_{3}$ (M = Ni, Zn), and SrCuO$_{2}$Jan 10 2015Jun 17 2015We studied the finite-size effects on the magnetic behavior of the quasi-one-dimensional spin S = $\frac{1}{2}$ Heisenberg antiferromagnets Sr$_{2}$CuO$_{3}$, Sr$_{2}$Cu$_{0.99}$M$_{0.01}$O$_{3}$ (M = Zn and Ni), and SrCuO$_{2}$. Magnetic susceptibility ... More
Magnetic ordering of Mn sublattice, dense Kondo lattice behavior of Ce in (RPd3)8Mn (R = La, Ce)Apr 02 2003We have synthesized two new interstitial compounds (RPd3)8Mn (R = La and Ce). The Mn ions present in "dilute" concentration of just 3 molar percent form a sublattice with an unusually large Mn-Mn near neighbor distance of ~ 85 nm. While the existence ... More
Rings of Invariant Module Type and Automorphism-Invariant ModulesJul 23 2012A module is called automorphism-invariant if it is invariant under any automorphism of its injective hull. In [Algebras for which every indecomposable right module is invariant in its injective envelope, Pacific J. Math., vol. 31, no. 3 (1969), 655-658] ... More
Rings and modules which are stable under automorphisms of their injective hullsJan 24 2013It is proved, among other results, that a prime right nonsingular ring (in particular, a simple ring) $R$ is right self-injective if $R_R$ is invariant under automorphisms of its injective hull. This answers two questions raised by Singh and Srivastava, ... More
High temperature linear magnetoresistance and scaling behavior in the Ba(Fe${_{1-x}}$Co${_{x}}$)$_{2}$As$_{2}$ seriesJan 11 2018We present magnetotransport studies of the parent, an underdoped and an optimally doped composition of the Ba(Fe${_{1-x}}$Co${_{x}}$)${_{2}}$As${_{2}}$ series. We observe that both the Kohler's and modified Kohler's scaling is typically violated in both ... More
Crystal growth of the non-magnetic Zn$^{2+}$ and magnetic Co$^{2+}$ doped quasi one-dimensional spin chain compound SrCuO$_{2}$ using the travelling solvent floating zone methodJan 10 2015We report on the crystal growth of the quasi one-dimensional quantum spin chain compound SrCuO$_{2}$ and its doped variants containing magnetic cobalt (0.25%, 0.5%, 1% and 2.5%) and non-magnetic zinc (0.5\% and 1\%) impurities. Crystals are grown using ... More
CeMnNi4: A soft ferromagnet with a high degree of transport spin polarizationSep 05 2005Oct 20 2005In this letter we introduce a new soft ferromagnetic compound, i.e. CeMnNi4, which exhibits a large moment (~4.95mu_B/Mn) and high degree of spin polarization. The system has a ferromagnetic transition temperature of 148K. Isothermal magnetization measurements ... More
Excess speicific heat of the gapped sliding phonons in the incommensurate composite crystal Sr$_{14}$Cu$_{24}$O$_{41}$Aug 02 2018Aug 03 2018We show that low temperature specific heat (C$_p$) of the incommensurate chain-ladder system Sr$_{14}$Cu$_{24}$O$_{41}$ is enriched by the presence of a rather large excess contribution of non-magnetic origin. Diluted Al doping at the Cu site or annealing ... More
Impurities in weakly coupled quantum spin chains Sr$_{2}$CuO$_{3}$ and SrCuO$_{2}$Jun 05 2017We study the effect of non-magnetic Zn$^{2+}$ (spin-$0$) and magnetic Ni$^{2+}$ (spin-$1$) impurities on the ground state and low-lying excitations of the quasi-one-dimensional spin-$1/2$ Heisenberg antiferromagnet Sr$_{2}$CuO$_{3}$ using inelastic neutron ... More
Dilute stuffing in the pyrochlore iridate $Eu_2Ir_2O_7$May 04 2018The pyrochlore Eu$_2$Ir$_2$O$_7$ has recently attracted significant attention as a candidate Weyl semimetal. The previous reports on this compound unanimously show a thermally induced metal to insulator (MI) transition, concomitant with antiferromagnetic ... More
Magnetic disorder and gap symmetry in optimally electron doped Sr(Fe, Co)$_2$As$_2$ superconductorAug 30 2017Aug 31 2017We investigate the magnetic pair-breaking due to Mn impurities in the optimally electron doped Sr(Fe$_{0.88} $Co$_{0.12} $)$_{2} $As$_2 $ superconductor to deduce the symmetry of the superconducting order parameter. Experiments on the as-grown crystals ... More
Metastable Nuclear Isomers as Dark Matter AcceleratorsJun 28 2019Inelastic dark matter and strongly interacting dark matter are poorly constrained by direct detection experiments since they both require the scattering event to deliver energy from the nucleus into the dark matter in order to have observable effects. ... More
The Dark Matter Phonon CouplingMay 14 2019Generically, the effective coupling between the dark matter and an atom scales with the number of constituents in the atom, resulting in the effective coupling being proportional to the mass of the atom. In this limit, when the momentum transfer is also ... More
Equidistribution of signs for Hilbert modular forms of half-integral weightAug 18 2017Feb 22 2018We prove an equidistribution of signs for the Fourier coefficients of Hilbert modular forms of half-integral weight. Our study focuses on certain subfamilies of coefficients that are accessible via the Shimura correspondence. This is a generalization ... More
Ordered spin-ice state in the geometrically frustrated metallic-ferromagnet Sm2Mo2O7Jun 28 2007The recent discovery of Spin-ice is a spectacular example of non-coplanar spin arrangements that can arise in the pyrochlore A2B2O7 structure. We present magnetic and thermodynamic studies on the metallic-ferromagnet pyrochlore Sm2Mo2O7. Our studies, ... More
Manifestation of geometric frustration on magnetic and thermodynamic properties of pyrochlores $Sm_2X_2O_7$ (X=Ti, Zr)Dec 18 2007We present here magnetization, specific heat and Raman studies on single-crystalline specimens of the first pyrochlore member $Sm_2Ti_2O_7$ of the rare-earth titanate series. Its analogous compound $Sm_2Zr_2O_7$ in the rare-earth zirconate series is also ... More
Study of CeNi4Mn by neutron diffractionOct 17 2006We report neutron diffraction measurements on CeNi4Mn, which has recently been identified as a soft ferromagnet (Tc ~ 140 K) with a sizeable spin-transport polarization. Our data show conclusively that the Mn atoms occupy a unique site (4c) in the unit ... More
Effects of quantum impurity spins on the magnetic properties of zigzag and linear spin chainsFeb 11 2016We investigated the magnetic ground state and low-energy excitations of the spin chains compounds SrCuO$_{2}$ (zigzag chains) and Sr$_{2}$CuO$_{3}$ (linear chains) in the presence of quantum impurities induced by lightly doping ($\leq 1 \%$) with Zn$^{2+}$ ... More
Single-crystal growth and magnetic properties of the metallic molybdate pyrochlore Sm2Mo2O7Aug 24 2007We have successfully grown cm3-size single crystals of the metallic-ferromagnet Sm2Mo2O7 by the floating-zone method using an infrared-red image furnace. The growth difficulties and the remedies found using a 2-mirror image furnace are discussed. Magnetization ... More
Effect of magnetic and non-magnetic impurities on the spin dimers in the spin 1/2 chains of quantum magnet Sr$_{14}$Cu$_{24}$O$_{41}$Aug 02 2018We study the effect of impurities on the two types of spin-dimers in the hybrid chain/ladder spin 1/2 quantum magnet Sr$_{14}$Cu$_{24}$O$_{41}$. Four different impurities were used, namely, the non-magnetic Zn (0.0025 and 0.01 per Cu) and Al (0.0025 and ... More
On $n^{th}$ class preserving automorphisms of $n$-isoclinism familyJan 19 2017Let $G$ be a finite group and $M,N$ be two normal subgroups of $G$. Let $Aut_N^M(G)$ denote the group of all automorphisms of $G$ which fix $N$ element wise and act trivially on $G/M$. Let $n$ be a positive integer. In this article we have shown that ... More
Coupled antiferromagnetic-ferroelectric transition, higher compensation temperature and enhanced exchange bias in SmFeO3 nanoparticlesNov 09 2016In transition metal oxides, quantum confinement arising from a large surface to volume ratio often gives rise to novel physico-chemical properties at nanoscale. Their size dependent properties have potential applications in diverse areas, including therapeutics, ... More
Temperature dependent Raman and x-ray studies of spin-ice pyrochlore $Dy_2Ti_2O_7$ and non-magnetic pyrochlore $Lu_2Ti_2O_7$Nov 28 2008We present here temperature-dependent Raman, x-ray diffraction and specific heat studies between room temperature and 12 K on single crystals of spin-ice pyrochlore compound $Dy_2Ti_2O_7$ and its non-magnetic analogue $Lu_2Ti_2O_7$. Raman data show a ... More
Nanosize effect: Enhanced compensation temperature and existence of magneto-dielectric coupling in SmFeO3Nov 09 2016Jun 29 2017In transition metal oxides, quantum confinement arising from a large surface to volume ratio often gives rise to novel physico-chemical properties at nanoscale. Their size dependent properties have potential applications in diverse areas, including therapeutics, ... More
Simultaneous behaviour of the Fourier coefficients of two Hilbert modular cusp formsMay 01 2018In this article, we study the simultaneous sign changes of the Fourier coefficients of two Hilbert cusp forms of different integral weights. We also study the simultaneous non-vanishing of Fourier coefficients, of two distinct non-zero primitive Hilbert ... More
Low temperature and high pressure Raman and x-ray studies of pyrochlore Tb$_2$Ti$_2$O$_7$ : phonon anomalies and possible phase transitionApr 23 2009We have carried out temperature and pressure-dependent Raman and x-ray measurements on single crystals of Tb$_2$Ti$_2$O$_7$. We attribute the observed anomalous temperature dependence of phonons to phonon-phonon anharmonic interactions. The quasiharmonic ... More
Highly tunable magnetic spirals and electric polarization in Gd$_{0.5}$Dy$_{0.5}$MnO$_3$Mar 05 2019Recent progress in the field of multiferroics led to the discovery of many new materials in which ferroelectricity is induced by cycloidal spiral orders. The direction of the electric polarization is typically constrained by spin anisotropies and magnetic ... More
On Equality of Certain Automorphism GroupsMay 21 2015Jan 29 2016Let $G = H\times A$ be a group, where $H$ is a purely non-abelian subgroup of $G$ and $A$ is a non-trivial abelian factor of $G$. Then, for $n \geq 2$, we show that there exists an isomorphism $\phi : Aut_{Z(G)}^{\gamma_{n}(G)}(G) \rightarrow Aut_{Z(H)}^{\gamma_{n}(H)}(H)$ ... More
On the gaps between non-zero Fourier coefficients of eigenforms with CMAug 15 2016Suppose $E$ is an elliptic curve over $\mathbb{Q}$ of conductor $N$ with complex multiplication (CM) by $\mathbb{Q}(i)$, and $f_E$ is the corresponding cuspidal Hecke eigenform in $S^{\mathrm{new}}_2(\Gamma_0(N))$. Then $n$-th Fourier coefficient of $f_E$ ... More
Statistical Theory of Force Induced Unzipping of DNAMay 07 2004May 18 2005The unzipping transition under the influence of external force of a dsDNA molecule has been studied using the Peyrard-Bishop Hamiltonian. The critical force $F_c(T)$ is found to depend on the potential parameters $k$, represents the stiffness of single ... More
Effect of genome sequence on the force-induced unzipping of a DNA moleculeMar 14 2006We considered a dsDNA polymer in which distribution of bases are random at the base pair level but ordered at a length of 18 base pairs and calculated its force elongation behaviour in the constant extension ensemble. The unzipping force $F(y)$ vs. extension ... More
Statistical Mechanics of thermal denaturation of DNA oligomersMay 07 2004Double stranded DNA chain is known to have nontrivial elasticity. We study the effect of this elasticity on the denaturation profile of DNA oligomer by constraining one base pair at one end of the oligomer to remain in unstretched (or intact) state. The ... More
Microcontroller Based Testing of Digital IP-CoreMay 09 2012Testing core based System on Chip is a challenge for the test engineers. To test the complete SOC at one time with maximum fault coverage, test engineers prefer to test each IP-core separately. At speed testing using external testers is more expensive ... More
Atmospheric muons charge ratio analysis at the INO-ICAL detectorSep 02 2017Jun 29 2018The proposed Iron Calorimeter (ICAL) detector at Indian Neutrino Observatory(INO) will be a large (50 kt) magnetized detector located 1270 m underground at Bodi West Hills in Tamilnadu. ICAL is capable of identifying the charge of the particles. In this ... More
Super-Arrhenius behaviour of molecular glass formersFeb 02 2019A theory is developed to calculate values of the potential energy barriers to structural relaxation in molecular glass formers from the data of static pair correlation function. The barrier height is shown to increase due to increase in number of the ... More
A Text to Speech (TTS) System with English to Punjabi ConversionNov 13 2014The paper aims to show how an application can be developed that converts the English language into the Punjabi Language, and the same application can convert the Text to Speech(TTS) i.e. pronounce the text. This application can be really beneficial for ... More
Effect of salt concentration on the stability of heterogeneous DNASep 28 2015We study the role of cations on the stability of double stranded DNA (dsDNA) molecules.It is known that the two strands of double stranded DNA(dsDNA) have negative charge due to phosphate group. Cations in the form of salt in the solution, act as shielding ... More
Phase diagram of mechanically stretched DNA: The salt effectSep 05 2014The cations, in form of salt, present in the solution containing DNA play a crucial role in the opening of two strands of DNA. We use a simple non linear model and investigate the role of these cations on the mechanical unzipping of DNA. The Hamiltonian ... More
Design and Implementation of Bit Transition CounterFeb 11 2014In today VLSI system design, power consumption is gaining more attention as compared to performance and area. This is due to battery life in portable devices and operating frequency of the design. Power consumption mainly consists of static power, dynamic ... More
Effect of defects on thermal denaturation of DNA OligomersMay 03 2001Aug 29 2001The effect of defects on the melting profile of short heterogeneous DNA chains are calculated using the Peyrard-Bishop Hamiltonian. The on-site potential on a defect site is represented by a potential which has only the short-range repulsion and the flat ... More
Case Study Based Software Engineering Project Development: State of ArtJun 11 2013This research paper designates the importance and usage of the case study approach effectively to educating and training software designers and software engineers both in academic and industry. Subsequently an account of the use of case studies based ... More
The Cosmology of Sub-MeV Dark MatterJan 30 2017Feb 28 2018Light dark matter is a compelling experimental target in light of stringent constraints on heavier WIMPs. However, for a sub-MeV WIMP, the universe is sufficiently well understood at temperatures below 10 MeV that there is no room for it to be a thermal ... More
Supernova signals of light dark matterMay 22 2019Dark matter direct detection experiments have poor sensitivity to a galactic population of dark matter with mass below the GeV scale. However, such dark matter can be produced copiously in supernovae. Since this thermally-produced population is much hotter ... More
Unbiased Ratio-Type Estimator Using Transformed Auxiliary Variable In Negative Correlation CaseOct 06 2012The objective of this paper is to propose an unbiased ratio-type estimator for finite population mean when the variables are negatively correlated. Hartley and Ross[2] and Singh and Singh [6] estimators are identified as particular cases of the proposed ... More
Axion Dark Matter Detection with Cold MoleculesJan 13 2011Sep 15 2011Current techniques cannot detect axion dark matter over much of its parameter space, particularly in the theoretically well-motivated region where the axion decay constant f_a lies near the GUT and Planck scales. We suggest a novel experimental method ... More
Vertex-disjoint Cycle Cover for graph signal processingFeb 19 2016Eigenvectors of the Laplacian of a cycle graph exhibit the sinusoidal characteristics of the standard DFT basis, and signals defined on such graphs are amenable to linear shift invariant (LSI) operations. In this paper we propose to reduce a generic graph ... More
Quantum Stern-Gerlach experiment and path entanglement of Bose-Einstein condensateAug 14 2016In this paper, a quantum Stern-Gerlach thought experiment is introduced where, in addition to the intrinsic angular momentum of an atom, the magnetic field is also treated quantum mechanically. A freely falling spin polarised Bose-Einstein condensate ... More
Spin fluctuations in a metallic antiferromagnetJul 01 2002The magnon energy and amplitude renormalization due to intraband particle-hole excitations are studied in a metallic antiferromagnet. The change in sign of the intraband contribution with $\omega$ results in significant differences between static and ... More
Spin waves in a band ferromagnet: spin-rotationally symmetric study with self-energy and vertex correctionsDec 26 2005Jan 19 2007First-order quantum corrections to the transverse spin-fluctuation propagator are obtained within a systematic inverse-degeneracy 1/N expansion, which provides a spin-rotationally symmetric scheme for including self-energy and vertex corrections while ... More
Spectral function of transverse spin fluctuations in an antiferromagnetJun 06 2000The spectral function of transverse spin fluctuations, including the contributions from both the single-particle and the collective (magnon) excitations in an antiferromagnet, is evaluated for the Hubbard model with NN and NNN hoppings in the full U-range ... More
On evaluation of transverse spin fluctuations in quantum magnetsFeb 04 1998Jan 28 2000A numerical method is described for evaluating transverse spin correlations in the random phase approximation. Quantum, spin-fluctuation corrections to sublattice magnetization are evaluated for the half-filled Hubbard antiferromagnet in two and three ... More
Time-Frequency analysis via the Fourier RepresentationApr 18 2016The nonstationary nature of signals and nonlinear systems require the time-frequency representation. In time-domain signal, frequency information is derived from the phase of the Gabor's analytic signal which is practically obtained by the inverse Fourier ... More
Extracting neutrino oscillation parameters using a simultaneous fit of the $ν_{e}$ appearance and $ν_μ$ disappearance data in the NOvA experimentOct 10 2017NOvA is a two detector, long baseline neutrino oscillation experiment designed to study $\nu_{e}$ ($\bar{\nu}_{e}$) appearance and $\nu_{\mu}$ ($\bar{\nu}_{\mu}$) disappearance in a $\nu_{\mu}$ ($\bar{\nu}_{\mu}$) beam produced at Fermilab. The near detector ... More
Numerical loop quantum cosmology: an overviewAug 27 2012A brief review of various numerical techniques used in loop quantum cosmology and results is presented. These include the way extensive numerical simulations shed insights on the resolution of classical singularities, resulting in the key prediction of ... More
Loop cosmological dynamics and dualities with Randall-Sundrum braneworldsMar 11 2006The discrete quantum geometric effects play an important role in dynamical evolution in the loop quantum cosmology. These effects which are significant at the high energies lead to the quadratic energy density modifications to the Friedmann equation, ... More
Interior-exterior penalty approach for solving elasto-hydrodynamic lubrication problem: Part IDec 12 2017Aug 21 2018A new interior-exterior penalty method for solving quasi-variational inequality and pseudo-monotone operators arising in two-dimensional point contact problem has been analyzed and developed in discontinuous Galerkin finite volume method environment. ... More
An attempt to settle the one-component versus two-component debate in Cuprate high-$T_c$ superconductorsApr 29 2019Related to the electronic structure of cuprate high-Tc superconductors there are two prevailing views: In one view, Barzykin, Pines, and collaborators argue that cuprates consist of two electronic subsystems: one with localized spins and the other having ... More
On the failure of mean-field theories near a critical pointFeb 27 2014Mar 04 2014It is well known that mean-field theories fail to reproduce the experimentally known critical exponents. The traditional argument which explain this failure of mean-field theories near a critical point is the Ginsburg criterion in which diverging fluctuations ... More
Thermodynamical Phase transitions, the mean-field theories, and the renormalization (semi)group: A pedagogical introductionFeb 27 2014While analyzing second order thermodynamical phase transitions, Lev Landau (the famous Russian physicist) introduced a very vital concept, the concept of an "order parameter". This not only amalgamated the previous fragmentary theoretical understanding ... More
Proposal for designing a two-stage buffer gas cooled beam sourceJan 11 2019A novel two-stage helium buffer gas cooled beam source is introduced. The properties of the molecular beams produced from this source are investigated theoretically using the CaF as a test molecule. The gas phase molecules are first produced inside a ... More
Bohm's realist interpretation of Quantum mechanicsMay 13 2008A brief account of the world view of classical physics is given first. We then recapitulate as to why the Copenhagen interpretation of the quantum mechanics had to renounce most of the attractive features of the clasical world view such as a causal description, ... More
Hidden Variables, Non Contextuality and Einstein-Locality in Quantum MechanicsJul 19 2005Jul 25 2005We discuss the problem of hidden variables and the motivation for introducting them in quantum mechanics. These include determinism, and the problem of meassurement and incompleteness. We first discuss Von-Neumann's imposisbility proof and then analyse ... More
Analytical method and its convergence analysis based on homotopy analysis for the integral form of doubly singular boundary value problemsNov 23 2017In this paper, we consider the nonlinear doubly singular boundary value problems $(p(x)y'(x))'+ q(x)f(x,y(x))=0,~0<x<1$ with Dirichlet/Neumann boundary conditions at $x=0$ and Robin type boundary conditions at $x=1$. Due to the presence of singularity ... More
Parametrized Borsuk-Ulam problem for projective space bundlesOct 26 2008Sep 27 2010Let $\pi: E \to B$ be a fiber bundle with fiber having the mod 2 cohomology algebra of a real or a complex projective space and let $\pi^{'}: E^{'} \to B$ be vector bundle such that $\mathbb{Z}_2$ acts fiber preserving and freely on $E$ and $E^{'}-0$, ... More
Conormal Varieties on the Cominuscule Grassmannian - IIMay 31 2018Sep 24 2018Let $X_w$ be a Schubert subvariety of a cominuscule Grassmannian $X$, and let $\mu:T^*X\rightarrow\mathcal N$ be the Springer map from the cotangent bundle of $X$ to the nilpotent cone $\mathcal N$. In this paper, we construct a resolution of singularities ... More
Reduction of Blocking Artifacts In JPEG Compressed ImageOct 03 2012Feb 12 2014In JPEG (DCT based) compresses image data by representing the original image with a small number of transform coefficients. It exploits the fact that for typical images a large amount of signal energy is concentrated in a small number of coefficients. ... More
Worldline approach to few-body physics on the latticeDec 06 2018We study the physics of two species of non-relativistic hard-core bosons with attractive or repulsive delta function interactions on a spacetime lattice using the worldline formulation. By tuning the chemical potential carefully we show that worm algorithms ... More
RG flows and cascades of $Lif_4^{(2)}\times S^1\times S^5$ vacuaMay 14 2018The (F1,D2,D8) brane configuration produces $Lif_4^{(2)}\times {S}^1\times S^5$ Lifshitz vacua supported by `massive' $B$-field. We present exact deformations of this system under which new massless $B$-modes of strings also get excited. Due to these ... More
Generation, estimation, and protection of novel quantum states of spin systemsApr 30 2018This thesis deals with the generation, estimation and preservation of novel quantum states of two and three qubits, on an NMR quantum information processor. Using the maximum likelihood ansatz, we have developed a method for state estimation such that ... More
The Yang-Mills and chiral fields in six dimensionsNov 14 2012Feb 20 2013In previous work (Singh, 2011), we constructed an action in six dimensions using Yang-Mills fields and an auxiliary Abelian field. Here we first write down all the equations of motion and the constraints which arise from such an action. From these equations ... More
Super-Yang-Mills and M5-branesJul 18 2011Aug 23 2011We uplift 5-dimensional super-Yang-Mills theory to a 6-dimensional gauge theory with the help of a space-like constant vector $\eta^M$, whose norm determines the Yang-Mills coupling constant. After the localization of $\eta^M$ the 6D gauge theory acquires ... More
SU(N) membrane $B\wedge F$ theory with dual-pairsNov 11 2008Dec 04 2008We construct a SU(N) membrane $B\wedge F$ theory with dual pairs of scalar and tensor fields. The moduli space of the theory is precisely that of $N$ M2-branes on the noncompact flat space. The theory possesses explicit SO(8) invariance and is an extension ... More
3-Branes on Eguchi-Hanson 6D InstantonsJan 15 2007Apr 27 2007We use the approach used by Eguchi-Hanson in constructing four-dimensional instanton metrics and construct a class of regular six-dimensional instantons which are nothing but $S^2\times S^2$ resolved conifolds. We then also obtain D3-brane solutions on ... More
Generalised Penrose Limits and PP-WavesJul 09 2003Jan 31 2004In this paper we construct generalised Penrose limits for the solutions of massive type IIA supergravity. We consider a Freund-Rubin type solution and apply these {\it massive} Penrose limits and obtain supersymmetric pp-wave which is a standard type ... More
New Supersymmetric Vacua for N=4, D=4 Gauged SupergravityJan 08 1998May 26 1998In this paper we obtain supersymmetric brane-like configurations in the vacuum of N=4 gauged $SU(2)\times SU(2)$ supergravity theory in four spacetime dimensions. Almost all of these vacuum solutions preserve either half or one quarter of the supersymmetry ... More
Macroscopic String-like Solutions in Massive SupergravityOct 24 1997Nov 25 1997In this report we obtain explicit string-like solutions of equations of motion of massive heterotic supergravity recently obtained by Bergshoeff, Roo and Eyras. We also find consistent string source which can be embedded in these backgrounds when space-time ... More
Magnetic Wormholes and Vertex OperatorsJul 20 1994We consider wormhole solutions in $2+1$ Euclidean dimensions. A duality transformation is introduced to derive a new action from magnetic wormhole action of Gupta, Hughes, Preskill and Wise. The classical solution is presented. The vertex operators corresponding ... More
An Analytic Perturbation Approach for Classical Spinning Particle DynamicsJun 07 2007Apr 10 2008A perturbation method to analytically describe the dynamics of a classical spinning particle, based on the Mathisson-Papapetrou-Dixon (MPD) equations of motion, is presented. By a power series expansion with respect to the particle's spin magnitude, it ... More
Weight distributions of all irreducible $μ$-constacyclic codes of length $\ell^n$Jun 27 2018Let $\mathbb{F}_q$ be a finite field of order $q$ and integer $n\ge 1$. Let $\ell$ be a prime such that $\ell^k|(q-1)$ for some integer $k\ge 1$ and $\mu$ be an element of order $\ell^k$ in $\mathbb{F}_q$. In this paper, we determine the weight distributions ... More
Orthogonal Hypergeometric Groups with a Maximally Unipotent MonodromyJun 23 2014Mar 10 2015Similar to the symplectic cases, there is a family of fourteen orthogonal hypergeometric groups with a maximally unipotent monodromy (cf. Table 1.1). We show that two of the fourteen orthogonal hypergeometric groups associated to the pairs of parameters ... More
Rates of convergence of a transient diffusion in a spectrally negative Lévy potentialJun 19 2006Jan 02 2008We consider a diffusion process $X$ in a random L\'{e}vy potential $\mathbb{V}$ which is a solution of the informal stochastic differential equation \begin{eqnarray*}\cases{dX_t=d\beta_t-{1/2}\mathbb{V}'(X_t) dt,\cr X_0=0,}\end{eqnarray*} ($\beta$ B. ... More
Real Elements in Spin GroupsApr 08 2008Let $F$ be a field of characteristic $\neq 2$. Let $G$ be an algebraic group defined over $F$. An element $t\in G(F)$ is called {\bf real} if there exists $s\in G(F)$ such that $sts^{-1}=t^{-1}$. A semisimple element $t$ in $GL_n(F), SL_n(F), O(q), SO(q), ... More
Classification of non-homogeneous Fourier matrices associated with modular data up to rank 5Oct 17 2016Nov 02 2016Modular data is an important topic of study in rational conformal field theory. A modular datum defines finite dimensional representations of the modular group $\mbox{SL}_2(\mathbf{Z})$. For every Fourier matrix in a modular datum there exists an Allen ... More
A Domino Theory of FlavorJun 25 2009Feb 03 2010We argue that the fermion masses and mixings are organized in a specific pattern. The approximately equal hierarchies between successive generations, the sizes of the mixing angles, the heaviness of just the top quark, and the approximate down-lepton ... More
Gravitational Collapse of Dark Energy Field ConfigurationsJul 29 2010It is now a well established fact based on several observations that we live in a Universe dominated by dark energy. The most natural candidates for dark energy are fields in curved space-time. We develop the formalism to study the gravitational collapse ... More
Gravitational Wave transient signal emission via Ekman Pumping in Neutron Stars during post-glitch relaxation phaseMay 26 2016Sep 05 2016Glitches in the rotational frequency of a spinning neutron star could be promising sources of gravitational wave signals lasting between a few {\mu}s to a few weeks. The emitted signals and their properties depend upon the internal properties of the neutron ... More
A small non-vanishing cosmological constant from vacuum energy: physically and observationally desirableDec 05 1994Dec 15 1995Increasing improvements in the independent determinations of the Hubble constant and the age of the universe now seem to indicate that we need a small non-vanishing cosmological constant to make the two independent observations consistent with each other. ... More
Classification of Homogeneous Fourier Matrices Associated with Modular DataOct 17 2016Modular data are commonly studied in mathematics and physics. A modular datum defines finite dimensional representations of the modular group $\mbox{SL}_2(\ZZ)$. For every Fourier matrix in a modular datum there exists a self-dual $C$-algebra. A Fourier ... More
Partition function of a bubble formed in double stranded DNASep 09 2009We calculate the entropic part of partition function of a bubble embedded in a double stranded DNA (dsDNA) by considering the total weights of possible configurations of a system of two single stranded DNA (ssDNA) of given length which start from a point ... More
Quantum Mechanics and RealityDec 20 2004We begin by discussing ``What exists?'', i.e. ontology, in Classical Physics which provided a description of physical phenomena at the macroscopic level. The microworld however necessitates a introduction of Quantum ideas for its understanding. It is ... More
Homi Jehangir Bhabha : Architect of Modern Science and Technology in IndiaJun 18 2009After describing Bhabha's early life at Bombay, now Mumbai, we discuss his research career at Cambridge, where he made many distinguished contributions to positron physics, cosmic rays and the meson theory. These include theory of positron-electron scattering ... More
Einstein and the QuantumOct 24 2005We review here the main contributions of Einstein to the quantum theory. To put them in perspective we first give an account of Physics as it was before him. It is followed by a brief account of the problem of black body radiation which provided the context ... More
Quantum effects in biology: master equation studies of exciton motion in photosynthetic systemsMar 01 2012The present review is devoted to our recent studies on the excitonic motion in photosynthetic systems. In photosynthesis, the light photon is absorbed to create an exciton in the antenna complex of the photosynthetic pigments. This exciton then migrates ... More
Non-linear Nyquist theorem: A conjectureSep 23 2014Thermodynamics of equilibrium states is well established. However, in nonequilibrium few general results are known. One prime and important example is that of Nyquist theorem. It relates equilibrium tiny voltage fluctuations across a conductor with its ... More
Controllable diffusion of cold atoms in a harmonically driven and tilted optical lattice: Decoherence by spontaneous emissionDec 11 2006May 07 2008We have studied some transport properties of cold atoms in an accelerated optical lattice in the presence of decohering effects due to spontaneous emission. One new feature added is the effect of an external AC drive. As a result we obtain a tunable diffusion ... More
Relaxation of Femtosecond Non-equilibrium Electrons in a Metallic SampleDec 11 2006A model calculation is given for the energy relaxation of a non-equilibrium distribution of hot electrons prepared in a metallic sample that has been subjected to homogeneous photo-excitation by a femtosecond laser pulse. The model assumes that the delta ... More
Studying the physics potential of long-baseline experiments in terms of new sensitivity parametersAug 24 2016We investigate physics opportunities to constraint leptonic CP-violation phase $\delta_{CP}$ through numerical analysis of working neutrino oscillation probability parameters, in the context of long base line experiments. Numerical analysis of two parameters, ... More
The Texture One Zero Neutrino Mass Matrix With Vanishing TraceMar 28 2018In the light of latest neutrino oscillation data, we have investigated the one zero Majorana neutrino mass matrix $M_{\nu}$ with zero sum condition of mass eigen values in the flavor basis, where charged lepton mass matrix is diagonal. Among the six possible ... More
Implication of rephasing invariant parameters on texture specific mass matricesApr 03 2018In the quark sector, Jarlskog rephasing invariant parameter $J_{CP}$ has important implications for the CP violation as well as phase structure of the quark mass matrices. In fact all CP violating effects in this sector are proportional to the magnitude ... More