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Full-Text Articles in Physics

Thermodynamics Of Integrable Chains With Alternating Spins, H. J. De Vega, Luca Mezincescu, Rafael I. Nepomechie Jan 1994

Thermodynamics Of Integrable Chains With Alternating Spins, H. J. De Vega, Luca Mezincescu, Rafael I. Nepomechie

Physics Articles and Papers

We consider a two-parameter (c¯,c̃) family of quantum integrable isotropic Hamiltonians for a chain of alternating spins of spin s=1/2 and s=1. We determine the thermodynamics for low-temperature T and small external magnetic field H, with T≪H. In the antiferromagnetic (c¯>0,c̃>0) case, the model has two gapless excitations. In particular, for c¯=c̃, the model is conformally invariant and has central charge cvir=2. When one of these parameters is zero, the Bethe ansatz equations admit an infinite number of solutions with lowest energy.


Numerical Simulation Of Nonequilibrium Effects In An Argon Plasma Jet, C. H. Chang, John D. Ramshaw Jan 1994

Numerical Simulation Of Nonequilibrium Effects In An Argon Plasma Jet, C. H. Chang, John D. Ramshaw

Physics Faculty Publications and Presentations

Departures from thermal (translational), ionization, and excitation equilibrium in an axisymmetric argon plasma jet have been studied by two?dimensional numerical simulations. Electrons, ions, and excited and ground states of neutral atoms are represented as separate chemical species in the mixture. Transitions between excited states, as well as ionization/recombination reactions due to both collisional and radiative processes, are treated as separate chemical reactions. Resonance radiation transport is represented using Holstein escape factors to simulate both the optically thin and optically thick limits. The optically thin calculation showed significant underpopulation of excited species in the upstream part of the jet ...


Thermodynamics Of A Free Q Fermion Gas, Asim Gangopadhyaya Dec 1993

Thermodynamics Of A Free Q Fermion Gas, Asim Gangopadhyaya

Asim Gangopadhyaya

We study the thermodynamics of a q-fermion gas for complex values of q on the unit circle. Special emphasis is given to the study of the virial coefficients and the specific heat of this gas. In particular, it is shown that if any state can accommodate up to p q-fermions, then the first p virial coefficients of such a gas are the same as that of a gas of free bosons. Explicit expressions for the deviation of higher virial coefficients from the corresponding values for a Bose gas are obtained. Further, as for ordinary fermions, it is shown that the ...