Articles written in Pramana – Journal of Physics

    • Field theoretic model of composite particles: a variational approach

      S P Misra S Panda

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      We consider here a variational method for describing composite particles. We use equal time anticommutators/commutators, and regard the field operators as arbitrary except for the constraint from the above. The expectation value of the Hamiltonian is extremized both with respect to the field operators and with respect to the wave functions, the former extremization being the new feature here. Comparison with other calculations has been made, and correspondence with them has also been established. We further show here how an “effective mass” can arise from a potential.

    • Static baryon properties in a relativistic quark model with centre-of-mass correction

      S N Jena S Panda

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      The static properties such as magnetic moments, charge radii and axial vector coupling constant ratios of the quark core of baryons in the nucleon octet have been calculated in an independent-quark model based on the Dirac equation with equally mixed scalar-vector potential in linear form in the current quark mass limit. The results obtained with appropriate corrections due to centre-of-mass motion are in reasonable agreement with experimental data. The magnetic moments of the quark core of baryons in the charmed andb-flavoured sectors have also been calculated with this model and the overall predictions so obtained compare very well with other model predictions.

    • Weak electric and magnetic form factors for semileptonic baryon decays in a relativistic quark model

      S N Jena S Panda

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      Weak electric and magnetic form factors for semileptonic baryon decays are calculated in a relativistic quark model based on the Dirac equation with the independent-quark confining potential of the formVq(r)=1/2(1+γ0)(a2r+V0). The values obtained for (g2/g1) are not very much different from the nonrelativistic results of Donoghue and Holstein. The values of (g1/f1) extracted from our model calculations of (f2/f1) in the Cabibbo limit compare well with the experimental values. The values of (f2/f1) for various semileptonic transitions are also estimated incorporating phenomenologically the effect of nonzerog2 in the ratio (g1/f1). It is found that the SU(3)-symmetry breaking does not generate significant departures in (f2/f1) values from the corresponding Cabibbo predictions.

    • Analytic methods for field induced tunneling in quantum wells with arbitrary potential profiles

      S Panda B K Panda

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      Electric field induced tunneling is studied in three different types of quantum wells by solving time-independent effective mass equation in analytic methods based on three different Airy function approaches. Comparison of different Airy function methods indicates that they are identical and connected to each other by the Breit-Wigner formula.

    • Working group report: Astroparticle and neutrino physics

      Raj Gandhi Subhendra Mohanty Tarun Souradeep S Agarwalla K Bhattacharya B Brahmachari R Crittenden S Goswami P Ghoshal M Lindner H S Mani S Mitra S Pascoli S Panda R Rangarajan S Ray T Roy Choudhury R Saha S Sarkar A Srivastava R Sheth S Uma Sankar U Yajnik

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      The working group on astroparticle and neutrino physics at WHEPP-9 covered a wide range of topics. The main topics were neutrino physics at INO, neutrino astronomy and recent constraints on dark energy coming from cosmological observations of large scale structure and CMB anisotropy.

    • Mixed convection MHD nanofluid flow over a wedge with temperature-dependent heat source


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      The present work investigates the transfer of heat, mass and fluid flow at the boundary layer of a nanofluid past a wedge in the presence of a variable magnetic field, temperature-dependent heat source and chemical reaction. The study is entirely theoretical and the proposed model describes the influence of Brownian motion and thermophoresis in the case of nanofluids. This study also includes the impact of thermal radiation. The partial differential equations relating to the flow are nonlinear and hence are numerically solved after transforming them into ordinary differential equations with similar variables. The outcome of the present study is given in tabular form and depicted graphically. It is found that the nanofluid flow along the wedge is accelerated by enhancing the Falkner–Skan parameter. The study further reveals that the magnetic field has an improved effect on the velocity. The Brownian motion parameter raises the profile of temperature but decreases the profile of volume fractions. Thermal radiation decreases the energy transport rate to the fluid and hence reduces the degree of heat present in the fluid. It is also observed that heat sink blankets the surface with a layer of cold fluid.

    • Exact solution for MHD elastico-viscous flow in porous medium with radiative heat transfer


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      This work focusses on deriving exact analytic solutions for an oscillatory flow of an elastico-viscous conducting fluid in a porous medium over a moving plate with variable suction. The momentum equation is enhanced with the resisting force offered by the permeability of the medium by incorporating the Darcy model. The energy transfer is equipped with volumetric heat generation/absorption and thermal radiation. Exact solutions for the governing equations are obtained by employing Cardan’s method, and comparative discussion is made by using the perturbation technique. The temperature distribution is evaluated by solving the energy equation considering relaxation time. Solutions of velocity fields are obtained for any value of viscoelastic parameter k$_1$. The results obtained from the analytical and approximation methods for any value of viscosity parameter are compared and found to be in good agreement. The physical behaviour of the pertinent parameters is obtained and displayed in graphs.

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