• C N Kumar

      Articles written in Pramana – Journal of Physics

    • Density excitations of a harmonically trapped ideal gas

      Jai Carol Cruz C N Kumar K N Pathak J Bosse

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      The dynamic structure factor $S(\mathbf{q}, \omega)$ of a harmonically trapped Bose gas has been calculated well above the Bose–Einstein condensation temperature by treating the gas cloud as a canonical ensemble of non-interacting classical particles. The static structure factor is found to vanish $\varpropto q^{2}$ in the long-wavelength limit. We also incorporate a relaxation mechanism phenomenologically by including a stochastic friction force to study $S(\mathbf{q}, \omega).$ A significant temperature dependence of the density fluctuation spectra is found. The Debye–Waller factor has been calculated for the trapped thermal cloud as a function of q and the number $\mathcal{N}$ of atoms. A substantial difference is found for small- and large-$\mathcal{N}$ clouds.

    • Complex dynamical invariants for two-dimensional complex potentials

      J S Virdi F Chand C N Kumar S C Mishra

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      Complex dynamical invariants are searched out for two-dimensional complex potentials using rationalization method within the framework of an extended complex phase space characterized by $x = x_{1} + ip_{3}. y = x_{2} + ip_{4}, p_{x} = p_{1} + ix_{3}, p_{y} = p_{2} + ix_{4}$. It is found that the cubic oscillator and shifted harmonic oscillator admit quadratic complex invariants. THe obtained invariants may be useful for studying non-Hermitian Hamiltonian systems.

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