Showing papers in "Physical Review D in 1963"

Thermal Conductivity of Silicon from 300 to 1400°K^*

Abstract: The thermal diffusivity of pure silicon has been measured from 300 to 1400\\ifmmode^\\circ\\else\\textdegree\\fi{}K. The specific heat of the same material over the same temperature range has been measured by Dennison. The thermal conductivity was obtained from the product of the thermal diffusivity, specific heat, and density. At 1400\\ifmmode^\\circ\\else\\textdegree\\fi{}K about two-thirds of the thermal conductivity was caused by lattice vibrations and one-third by bipolar diffusion. Wiedemann-Franz type diffusion accounted for less than one percent of the total thermal conductivity at 1400\\ifmmode^\\circ\\else\\textdegree\\fi{}K. Thermal transport by direct transmission of radiation appeared to be negligible up to 1400\\ifmmode^\\circ\\else\\textdegree\\fi{}K. The Gr\\\"uneisen constant for silicon from these high-temperature thermal conductivity measurements was 1.96, if the Debye temperature is taken as 636\\ifmmode^\\circ\\else\\textdegree\\fi{}K.

Quantized Gravitational Field. II

Abstract: A gravitational action operator is constructed that is invariant under general coordinate transformations and local Lorentz (gauge) transformations. To interpret the formalism the arbitrariness in description must be restricted by introducing gauge conditions and coordinate conditions. The time gauge is defined by locking the time axes of the local coordinate systems to the general coordinate time axis. The resulting form of the action operator, including the contribution of a spinless matter field, enables canonical pairs of variables to be identified. There are four field variables that lack canonical partners, in virtue of differential constraint equations, which can be interpreted as space-time coordinate displacements. In a physically distinguished class of coordinate system the gravitational field variables are not explicit functions of the coordinate displacement parameters. There remains the freedom of Lorentz transformation. The generators of spatial translations and rotations have the correct commutation properties. The question of Lorentz invariance is left undecided since the energy density operator is only given implicitly.

Photodisintegration of helium

Abstract: The electric dipole bremsstrahlung-weighted cross section sigma /sub beta / and integrated cross section sigma /sub int/ for the photodisintegration of helium have been calculated using the modified Irving wave function. Good agreement has been obtained with the current experiment values: sigma = 2.4 plus or minus 0.15 mb and sigma /sub int/ = 95 plus or minus 7 Mev mb. The results have also been compared with the recent calcuiations of Goldhammer and Valk. (auth)