C^+ distribution around S1 in rho Ophiuchi

We analyze a [C II] 158 micron map obtained with the L2 GREAT receiver on SOFIA of the emission/reflection nebula illuminated by the early B star S1 in the rho-OphA cloud core. This data set has been complemented with maps of CO(3-2), 13CO(3-2) and C18O(3-2), observed as a part of the JCMT Gould Belt Survey, with archival HCO^+(4-3) JCMT data, as well as with [O I] 63 and 145 micron imaging with Herschel/PACS. The [C II] emission is completely dominated by the strong PDR emission from the nebula surrounding S1 expanding into the dense Oph A molecular cloud west and south of S1. The [C II] emission is significantly blue shifted relative to the CO spectra and also relative to the systemic velocity, particularly in the northwestern part of the nebula. The [C II] lines are broader towards the center of the S1 nebula and narrower towards the PDR shell. The [C II] lines are strongly self-absorbed over an extended region in the S1 PDR. Based on the strength of the [13C II] F = 2-1 hyperfine component, [C II] is significantly optically thick over most of the nebula. CO and 13CO(3-2) spectra are strongly self-absorbed, while C18O(3-2) is single peaked and centered in the middle of the self-absorption. We have used a simple two-layer LTE model to characterize the background and foreground cloud contributing to the [C II] emission. From this analysis we estimate the extinction due to the foreground cloud to be ~9.9 mag, which is slightly less than the reddening estimated towards S1. Since some of the hot gas in the PDR is not traced by low J CO emission, this result appears quite plausible. Using a plane parallel PDR model with the observed [OI(145)]/[C II] brightness ratio and an estimated FUV intensity of 3100-5000 G0 suggests that the density of the [C II] emitting gas is ~3-4x10^3 cm^-3.Comment: Accepted for publication in Astronomy & Astrophysic

Origin of positive magnetoresistance in small-amplitude unidirectional lateral superlattices

We report quantitative analysis of positive magnetoresistance (PMR) for unidirectional-lateral-superlattice samples with relatively small periods (a=92-184 nm) and modulation amplitudes (V_0=0.015-0.25 meV). By comparing observed PMR's with ones calculated using experimentally obtained mobilities, quantum mobilities, and V_0's, it is shown that contribution from streaming orbits (SO) accounts for only small fraction of the total PMR. For small V_0, the limiting magnetic field B_e of SO can be identified as an inflection point of the magnetoresistance trace. The major part of PMR is ascribed to drift velocity arising from incompleted cyclotron orbits obstructed by scatterings.Comment: 12 pages, 9 figures, REVTe

Determining the phonon DOS from specific heat measurements via maximum entropy methods

The maximum entropy and reverse Monte-Carlo methods are applied to the computation of the phonon density of states (DOS) from heat capacity data. The approach is introduced and the formalism is described. Simulated data is used to test the method, and its sensitivity to noise. Heat capacity measurements from diamond are used to demonstrate the use of the method with experimental data. Comparison between maximum entropy and reverse Monte-Carlo results shows the form of the entropy used here is correct, and that results are stable and reliable. Major features of the DOS are picked out, and acoustic and optical phonons can be treated with the same approach. The treatment set out in this paper provides a cost-effective and reliable method for studies of the phonon properties of materials.Comment: Reprint to improve access. 10 pages, 6 figure

The Paradoxical Forces for the Classical Electromagnetic Lag Associated with the Aharonov-Bohm Phase Shift

The classical electromagnetic lag assocated with the Aharonov-Bohm phase shift is obtained by using a Darwin-Lagrangian analysis similar to that given by Coleman and Van Vleck to identify the puzzling forces of the Shockley-James paradox. The classical forces cause changes in particle velocities and so produce a relative lag leading to the same phase shift as predicted by Aharonov and Bohm and observed in experiments. An experiment is proposed to test for this lag aspect implied by the classical analysis but not present in the currently-accepted quantum topological description of the phase shift.Comment: 8 pages, 3 figure

A Probe Particle in Kerr-Newman-deSitter Cosmos

We consider the force acting on a spinning charged test particle (probe particle) with the mass m and the charge q in slow rotating the Kerr-Newman-deSitter(KNdS) black hole with the mass M and the charge Q. We consider the case which the spin vector of the probe particle is parallel to the angular momentum vector of the KNdS space-time. We take account of the gravitational spin-spin interaction under the slow rotating limit of the KNdS space-time. When Q=M and q=m, we show that the force balance holds including the spin-spin interaction and the motion is approximately same as that of a particle in the deSitter space-time. This force cancellation suggests the possibility of the existence of an exact solution of spinning multi-KNdS black hole.Comment: 7 pages, Classical and Quantum Gravity accepte

A Cosmological No-Hair Theorem

A generalisation of Price's theorem is given for application to Inflationary Cosmologies. Namely, we show that on a Schwarzschild--de Sitter background there are no static solutions to the wave or gravitational perturbation equations for modes with angular momentum greater than their intrinsic spin.Comment: 9 pages, NCL94 -TP4, (Revtex