Papers by Lambodar Prasad Singh
Lettere al Nuovo Cimento, 1979
The narrow Y-resonances discovered in c+e -and proton-nucleus reactions (~) have been popularly i... more The narrow Y-resonances discovered in c+e -and proton-nucleus reactions (~) have been popularly interpreted as bound states of a fifth quark (b), ~alled ~beautiful ~), of mass m b ~ 5 GeV and its antiquark (2). A clean test of this idea will be the experimental observation of isodoublet of ~ beautiful, mesons B-(bu), B~ and their resonances B*-and B*. With the PETR~k in operation the observation of these states is perhaps round the corner. _is it has been emphasized in case of charmed mesons (3) the mass differences ~nB---~B o, and roB*--mB*o and m R. --m B will be crucial in determining the production ratios of various ~ beautiful ~ mesons in e+c -annihilation and their decay mechanisms. It should be mentioned here that these mass splittings have recently been calculated by Bo~ (~) and K~A~ (5), using the extension of Cottingham formula to SU5 and nonrelativistic quark model, respectively. It is interesting to note that the results of these two calculations are of some magnitude but of opposite sign. BOAL gets mR---taro = 2 MeV whereas Khare's estimate is m B---~nBo -----(--1.41 • MeV which is rather expected from the nature of K-splittings since ~ b ~> and ~ s ,~ quarks carry the same charge. This situation is to be contrasted with the fact that all the calculations of D*, D ~ mass difference in various formalism like bag model (~), Cottingham formulations (7) (l) S. ~vV.
Propulsion and Power Research, 2016
An attempt has been made to study the heat and mass transfer effects in a boundary layer flow thr... more An attempt has been made to study the heat and mass transfer effects in a boundary layer flow through porous medium of an electrically conducting viscoelastic fluid subject to transverse magnetic field in the presence of heat source/sink and chemical reaction. It has been considered the effects of radiation, viscous and Joule dissipations and internal heat generation/ absorption. Closed form solutions for the boundary layer equations of viscoelastic, second-grade and Walters' B 0 fluid models are obtained. The method of solution involves similarity transformation. The transformed equations of thermal and mass transport are solved by applying Kummer's function. The solutions of temperature field for both prescribed surface temperature (PST) as well as prescribed surface heat flux (PHF) are obtained. It is important to remark that the interaction of magnetic field is found to be counterproductive in enhancing velocity and concentration distribution whereas the presence of chemical reaction as well as porous matrix with moderate values of magnetic parameter reduces the temperature and concentration fields at all points of flow domain.
International Journal of Modern Physics D, 1995
The Dirac equation is generalised to the Robertson-Walker space-time in a Cartesian tetrad gauge.... more The Dirac equation is generalised to the Robertson-Walker space-time in a Cartesian tetrad gauge. Its relationship with the Dirac equation in the diagonal tetrad gauge is established. The time dependence of the solution for different models of the expanding Universe is discussed.
Il Nuovo Cimento A, 1978
SummaryWe study diffractive and inclusive production of charmed mesons in neutrino scattering. Th... more SummaryWe study diffractive and inclusive production of charmed mesons in neutrino scattering. The reactions are considered only in the low-q2 region. The Regge-pole model is invoked to estimate exclusive as well as inclusive cross-sections. The consequences ofV+A weak current are briefly discussed.RiassuntoSi studia la produzione difrattiva ed inclusiva dei mesoni incantati nello scattering dei neutrini. Le reazioni sono considerate solo nella regione aq2 basso. Ci si richiama al modello del polo di Regge per valutare le sezioni d’urto tanto esclusive che inclusive. Si discutono brevemente le conseguenze della corrente deboleV+A.РеэюмеМы исследуем дифракционное и инклюэивное рождение очарованных меэонов в процессе рассеяния нейтрино. Рассматриваются реакции только в области малыхq2. Модель полюсов Редже необходима для оценки зксклюэивных, а также инклюэивных поперечных сечений. Обсуждаются следствияV+A слабого тока.
Pramana, 2002
We exhibit the supersymmetric quantum mechanical structure of the full 3•1 dimensional Dirac equa... more We exhibit the supersymmetric quantum mechanical structure of the full 3•1 dimensional Dirac equation considering 'mass' as a function of coordinates. Its usefulness in solving potential problems is discussed with specific examples. We also discuss the 'physical' significance of the supersymmetric states in this formalism.
Gravitation & Cosmology - GRAVIT COSMOL, 2007
We apply the spacetime dependent lagrangian formalism [1] to the action in general relativity. We... more We apply the spacetime dependent lagrangian formalism [1] to the action in general relativity. We obtain a Barriola-Vilenkin type monopole solution by exploiting theelectrogravity duality of the vacuum Einstein equations and using a modified definition of empty space. An {\it upper bound} is obtained on the monopole mass ${\tt M}$, ${\tt M}\leq e^{(1-\alpha)/\alpha}/(1-\alpha)^{2}{\tt G}$ where $\alpha = 2k $ is the global monopole charge. Keywords: global monopole, electrogravity duality, holographic principle. PACS: 11.15.-q, 11.27.+d, 14.80.Hv, 04.
Physical Review D, 1978
Bounds on slope and curvature of absorptive inelastic differential cross section are deduced. It ... more Bounds on slope and curvature of absorptive inelastic differential cross section are deduced. It is found that the differential cross section for π-p→π 0 n and π-p→ηn scale remarkably over a wide range of energy.
Physical Review D, 1980
Cross sections for production of BB¯, B¯B*+B¯*B, and B*B¯* mesons (carrying b-quark quantum numbe... more Cross sections for production of BB¯, B¯B*+B¯*B, and B*B¯* mesons (carrying b-quark quantum numbers) in e+e- annihilation are estimated and differential cross sections are evaluated. The cross sections for e+e--->e+e-etab, e+e--->e+e-chib, and e+e--->e+e-BB¯ are computed in the equivalent-photon approximation.
Physical Review D, 1977
We study the inclusive production of D' and diffractive production of D*+ in neutrino scattering ... more We study the inclusive production of D' and diffractive production of D*+ in neutrino scattering using the V + A form of the charm current. Cross sections for production of D + and D*' are of'the order of lo-'' cm2/Gev3 and cmZ/GeV3, respectively.
Letters in Mathematical Physics, 1984
The gauge potential for the 2-monopole solution is shown to have an infinite line of singularity ... more The gauge potential for the 2-monopole solution is shown to have an infinite line of singularity running from _oo to +oo in any fixed direction in the unitary gauge. The string structures
International Journal of Modern Physics A, 1991
Masses of t-flavored hadrons have been computed using a modified bag model well suited for consid... more Masses of t-flavored hadrons have been computed using a modified bag model well suited for considering heavy quarks inside the bag. Results have been obtained for mt=50 GeV and 150 GeV as representative masses of the light and heavy top scenarios.
International Journal of Modern Physics A, 1995
We have presented canonical and path integral formulations of a theory of loops and closed string... more We have presented canonical and path integral formulations of a theory of loops and closed strings with the matter field quanta transforming in the adjoint representation of the SU (N) gauge group. The physical processes arising out of the interactions of loops and closed strings are discussed.
The Astrophysical Journal, 2016
We investigate primordial black hole formation in the matter-dominated phase of the Universe, whe... more We investigate primordial black hole formation in the matter-dominated phase of the Universe, where nonspherical effects in gravitational collapse play a crucial role. This is in contrast to the black hole formation in a radiation-dominated era. We apply the Zel'dovich approximation, Thorne's hoop conjecture, and Doroshkevich's probability distribution and subsequently derive the production probability β 0 of primordial black holes. The numerical result obtained is applicable even if the density fluctuation σ at horizon entry is of the order of unity. For σ 1, we find a semi-analytic formula β 0 0.05556σ 5 , which is comparable with the Khlopov-Polnarev formula. We find that the production probability in the matter-dominated era is much larger than that in the radiation-dominated era for σ 0.05, while they are comparable with each other for σ 0.05. We also discuss how σ can be written in terms of primordial curvature perturbations.
General Relativity and Gravitation, 2020
In this work, we use power-law cosmology to investigate the evolution of black holes within the c... more In this work, we use power-law cosmology to investigate the evolution of black holes within the context of metric f (R) gravity satisfying the conditions provided by Starobinsky model. In our study, it is observed that presently accelerated expansion of the universe can be suitably explained by this integrated model without the need for dark energy. We also found that mass of a black hole decreases by absorbing surroundings energy-matter due to modification of gravity and more the accretion rate more is mass loss. Particularly the black holes, whose formation mass is nearly 10 20 gm and above are evaporated at a particular time irrespective of their formation mass. Again our analysis reveals that the maximum mass of a black hole supported by metric f (R) gravity is 10 12 M⊙, where M⊙ represents the solar mass.
International Journal of Theoretical Physics, 2015
In our work, we study the evolution of primordial black holes within the context of Brans-Dicke t... more In our work, we study the evolution of primordial black holes within the context of Brans-Dicke theory by assuming present universe as vacuum dominated. We also consider the accretion of radiation, matter and vacuum energy only during respective dominant periods. From our study, we found that the accretion rate is slower in both radiation and vacuum energy dominated eras in Brans-Dicke theory in comparision with General Theory of Relativity [1]. Thus the PBHs evaporate at a faster rate in Brans-Dicke theory than Standard Cosmology [1], if we consider the presence of vacuum energy in both cases. We also find that vacuum energy accretion efficiency should be less than 0.61.
International Journal of Modern Physics D, 2013
We investigate the evolution of primordial black hole mass spectrum by including both accretion o... more We investigate the evolution of primordial black hole mass spectrum by including both accretion of radiation and Hawking evaporation within Brans–Dicke (BD) cosmology in radiation-, matter- and vacuum-dominated eras. We also consider the effect of evaporation of primordial black holes on the expansion dynamics of the universe. The analytic solutions describing the energy density of the black holes in equilibrium with radiation are presented. We demonstrate that these solutions act as attractors for the system ensuring stability for both linear and nonlinear situations. We show, however, that inclusion of accretion of radiation delays the onset of this equilibrium in all radiation-, matter- and vacuum-dominated eras.
Lettere Al Nuovo Cimento Series 2, 1976
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Papers by Lambodar Prasad Singh