• Volume 50, Issue 4

      April 1998,   pages  271-354

    • Correlation between zeroes and poles ofS matrix for complex potentials

      I Jamir E F P Lyngdoh C S Shastry

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      Using several illustrative examples, the nature of resonance poles and the corresponding zeroes of the s-waveS matrix is examined for several potentials having an absorptive pocket followed by a barrier. It is shown that even though the presence of absorption practically suppresses the manifestation of resonance in the elastic scattering cross section, the effect of the resonances generated by the absorptive pocket is more clearly manifested in the absorption cross section provided the barrier width is not too large. We further find that the signature of barrier top resonances are also more clearly manifested in the absorption cross section rather than in the elastic scattering cross section. These results have been interpreted in terms of complex resonance poles and corresponding zeroes of theS matrix. This implies that in complex potential scattering like heavy ion collisions, the reaction channel cross section peak is a more reliable signature of resonance phenomenon than the variation of the elastic channel cross section with energy.

    • Universal inaccessibility principle

      Anil A Bhalekar

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      The universal inaccessibility principle (UIP) which was previously used in developing the generalized phenomenological irreversible thermodynamic theory (GPITT) is discussed at length. UIP provides both the thermodynamic temperature and the corresponding entropy function for a local nonequilibrium state without involving any physical device. The Carathéodory principle is obtained as a particular case of the equilibrium part of UIP. The system with negative temperatures are also covered by UIP. It is revealed that the use of UIP is implied in the De Donderian thermodynamic description of irreversibility due to chemical reactions and also in the classical irreversible thermodynamic description of Onsager-Prigogine-Meixner-de Groot. The reversible adiabatic paths of a chemically reactive closed system remain perfectly isentropic even if concomitantly a chemical conversion takes place within the system.

    • On the construction of an extended thermodynamic framework for irreversible processes

      Anil A Bhalekar Leopoldo S García-Colín

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      It is shown that the practice in extended irreversible thermodynamics of raising the physical fluxes, such asq, the heat flux density, etc. to the status of independent thermodynamic variables does not meet the basic thermodynamic requirements nor in a real situation by keeping them constant one can vary the other thermodynamic independent variables. To elucidate this point the phenomena of rigid body heat conduction is used as an illustrative expample. It is argued that the thermometric temperature of systems whether in equilibrium or in nonequilibrium is the same physical entity.

    • Schwarzschild black hole with global monopole charge

      Naresh Dadhich K Narayan U A Yajnik

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      We derive the metric for a Schwarzschild black hole with global monopole charge by relaxing asymptotic flatness of the Schwarzschild field. We then study the effect of global monopole charge on particle orbits and the Hawking radiation. It turns out that existence, boundedness and stability of circular orbits scale up by (1−8πη2)−1, and the perihelion shift and the light bending by (1−8πη2)−3/2, while the Hawking temperature scales down by (1−8πη2)2 the Schwarzschild values. Hereη is the global charge.

    • Approximate fixed-ρ solution of ‘sea-quark’ evolution equation at small-x and HERA

      A Saikia

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      We found an approximate simple solution of sea-quark evolution equation in terms ofρ(=√ln(x0/x)/ln[ln(Q22)/(Q022)]) andζ(≡ln[ln(Q2Λ2)/ln(Q022)]) in the small-x region whenρ is fixed and compared with HERA data. Agreement with data is found for largeQ2 and smallρ. Comparison with double asymptotic scaling prediction is made. We found a critical value ofρ. More data are needed to confirm this point.

    • Weak radiative decay Λb→Λγ in the heavy quark effective theory

      A K Giri R Mohanta

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      The weak radiative decay Λb→Λγ is studied in the heavy quark effective theory treatings-quark as heavy. This rare decay is induced by the short distance electromagnetic penguins. Including corrections of the order of (1/mQ), we obtain the transition matrix element and the corresponding decay width. The Isgur-Wise function is evaluated in the largeNc limit and the branching ratio obtained is 1.48×10−5.

    • Frictional trajectories near a barrier: A dissipationless Newtonian approach

      V J Menon N Chanana Y Singh

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      We address the problem of classical frictional motion under a potentialV possessing a barrier, apart from other possible confining and nonstationary terms. It is pointed out that the Green’s solution of the exact equation of motion can be reduced (under suitable conditions) either to an improved Rayleigh form or a non-Rayleigh form, the latter being outside the scope of the standard large-friction treatment of the Fokker-Planck equation. The resulting dissipationless dynamics involves an appropriately scaled potential which may have promising applications to quantum stochastic phenomena. Genuine dissipative corrections in regions far away from the barrier can be accounted for by the higher-order terms in our asymptotic expansions.

    • Orthogonal interaction of bernstein mode with ion-acoustic wave through plasma maser effect

      P N Deka

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      Interaction of Bernstein mode wave with ion-acoustic turbulence is treated as the plasma maser effect. Ion-acoustic turbulence is considered as resonant mode, propagating orthogonal to the test Bernstein mode. The external magnetic field, in the direction of ion-acoustic turbulence, is playing key role in transferring energy in upconversion process from resonant low frequency wave to the high frequency wave through modulated electric field. It is shown that the direct coupling term and the associated reverse absorbtion effect do not contribute individually to the growth or damping to the Bernstein mode. Only the polarization coupling term is found to be effective in the energy upconversion process as the external magnetic field is providing momentum in the direction of propagation of Bernstein mode. The polarization coupling term is identified to be the dominant upconversion factor in the plasma maser effect.

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