Thermodynamics Of dilaton-axion black holes

Considering a generalised action for Einstein Maxwell theory in four dimensions coupled to scalar and pseudo-scalar fields, the thermodynamic properties of asymptotically flat black holes solutions in such a background are investigated. Bekenstein-Hawking area-entropy law is verified for these class of black holes. From the property of specific heat, it is shown that such black holes can be stable for certain choice of the parameters like charge, mass and the scalar vacuum expectation value. The possibility of a black hole phase transition is discussed in this context.Comment: 7 Pages, Revtex, To appear in Phys.Rev.

Scattering of Carriers by Charged Dislocations in Semiconductors

The scattering of carriers by charged dislocations in semiconductors is studied within the framework of the linearized Boltzmann transport theory with an emphasis on examining consequences of the extreme anisotropy of the scattering potential. A new closed-form approximate expression for the carrier mobility valid for all temperatures is proposed. The ratios of quantum and transport scattering times are evaluated after averaging over the anisotropy in the relaxation time. The value of the Hall scattering factor computed for charged dislocation scattering indicates that there may be a factor of two error in the experimental mobility estimates using the Hall data. An expression for the resistivity tensor when the dislocations are tilted with respect to the plane of transport is derived. Finally an expression for the isotropic relaxation time is derived when the dislocations are located within the sample with a uniform angular distribution.Comment: 3 figure

Altitude distribution, origin and flux of sodium in the atmosphere

Sodium equilibrium altitude distribution, origin, and flux calculated for earth atmospher