18,662 research outputs found

    SU(1,1)SU(1,1) and SU(2)SU(2) Perelomov number coherent states: algebraic approach for general systems

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    We study some properties of the SU(1,1)SU(1,1) Perelomov number coherent states. The Schr\"odinger's uncertainty relationship is evaluated for a position and momentum-like operators (constructed from the Lie algebra generators) in these number coherent states. It is shown that this relationship is minimized for the standard coherent states. We obtain the time evolution of the number coherent states by supposing that the Hamiltonian is proportional to the third generator K0K_0 of the su(1,1)su(1,1) Lie algebra. Analogous results for the SU(2)SU(2) Perelomov number coherent states are found. As examples, we compute the Perelomov coherent states for the pseudoharmonic oscillator and the two-dimensional isotropic harmonic oscillator

    Results of an Examination of Metal Specimens from an Excavation of Shamshir Ghar, Afghanistan

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    Author Institution: Department of Chemistry, The Ohio State University, Columbu

    Melting of Polydisperse Hard Disks

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    The melting of a polydisperse hard disk system is investigated by Monte Carlo simulations in the semigrand canonical ensemble. This is done in the context of possible continuous melting by a dislocation unbinding mechanism, as an extension of the 2D hard disk melting problem. We find that while there is pronounced fractionation in polydispersity, the apparent density-polydispersity gap does not increase in width, contrary to 3D polydisperse hard spheres. The point where the Young's modulus is low enough for the dislocation unbinding to occur moves with the apparent melting point, but stays within the density gap, just like for the monodisperse hard disk system. Additionally, we find that throughout the accessible polydispersity range, the bound dislocation-pair concentration is high enough to affect the dislocation unbinding melting as predicted by Kosterlitz, Thouless, Halperin, Nelson and Young.Comment: 6 pages, 6 figure
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