Heating of trapped atoms near thermal surfaces

We study the electromagnetic coupling and concomitant heating of a particle in a miniaturized trap close to a solid surface. Two dominant heating mechanisms are identified: proximity fields generated by thermally excited currents in the absorbing solid and time-dependent image potentials due to elastic surface distortions (Rayleigh phonons). Estimates for the lifetime of the trap ground state are given. Ions are particularly sensitive to electric proximity fields: for a silver substrate, we find a lifetime below one second at distances closer than some ten micrometer to the surface. Neutral atoms may approach the surface more closely: if they have a magnetic moment, a minimum distance of one micrometer is estimated in tight traps, the heat being transferred via magnetic proximity fields. For spinless atoms, heat is transferred by inelastic scattering of virtual photons off surface phonons. The corresponding lifetime, however, is estimated to be extremely long compared to the timescale of typical experiments.Comment: to be published in Europhys. Lett. (7 pages, 3 figures, includes europhys.sty style file

Loss and heating of particles in small and noisy traps

We derive the life time and loss rate for a trapped particle that is coupled to fluctuating fields in the vicinity of a room-temperature metallic and/or dielectric surface. Our results indicate a clear predominance of near field effects over ordinary blackbody radiation. We develop a theoretical framework for both charged and neutral particles with and without spin. Loss processes that are due to a transition to an untrapped internal state are included.Comment: Slightly modified manuscript, as accepted for publication in Appl. Phys. B (04 oct 1999). 10 pages, 5 .eps figures, LaTeX uses Springer style file svjou

Universal amplitude ratios in finite-size scaling: three-dimensional Ising model

Motivated by the results of two-dimensional conformal field theory (CFT) we investigate the finite-size scaling of the mass spectrum of an Ising model on three-dimensional lattices with a spherical cross section. Using a cluster-update Monte Carlo technique we find a linear relation between the masses and the corresponding scaling dimensions, in complete analogy to the situation in two dimensions. Amplitude ratios as well as the amplitudes themselves appear to be universal in this case.Comment: 3 pages, 2 figures, proceedings of LATTICE99, Pis

Recent Developments in Maser Theory

This review covers selected developments in maser theory since the previous meeting, "Cosmic Masers: From Proto-Stars to Black Holes" (Migenes & Reid 2002). Topics included are time variability of fundamental constants, pumping of OH megamasers and indicators for differentiating disks from bi-directional outflows.Comment: Review presented at IAU symposium 242, "Astrophysical Masers and their Environments

Cuestiones actuales del Derecho local alemán

El presente trabajo expone las principales reformas y debates que se han producido en el ámbito del Derecho local de la República Federal de Alemania en los últimos años. Con esa finalidad se analizan los fundamentos básicos constitucionales y legales del Derecho local, así como sus reformas más importantes, previendo los efectos que se han producido o que pueden llegar a producirse.This work deals with the main reforms and debates that have emerged in the field of local government in the last years. With this aim the authors analyze the constitutional and legal foundations of municipal Law in Germany, as well as the most important reforms carried out recently. On that basis they attempt to identify and anticipate the effects that these reforms could have on the German system of local government

Local scale-invariance and ageing in noisy systems

The influence of the noise on the long-time ageing dynamics of a quenched ferromagnetic spin system with a non-conserved order parameter and described through a Langevin equation with a thermal noise term and a disordered initial state is studied. If the noiseless part of the system is Galilei-invariant and scale-invariant with dynamical exponent z=2, the two-time linear response function is independent of the noise and therefore has exactly the form predicted from the local scale-invariance of the noiseless part. The two-time correlation function is exactly given in terms of certain noiseless three- and four-point response functions. An explicit scaling form of the two-time autocorrelation function follows. For disordered initial states, local scale-invariance is sufficient for the equality of the autocorrelation and autoresponse exponents in phase-ordering kinetics. The results for the scaling functions are confirmed through tests in the kinetic spherical model, the spin-wave approximation of the XY model, the critical voter model and the free random walk.Comment: Latex2e, 45 pages, no figures, final for

Ammonia (J,K) = (1,1) to (4,4) and (6,6) inversion lines detected in the Seyfert 2 galaxy NGC 1068

We present the detection of the ammonia (NH3) (J,K) = (1,1) to (4,4) and (6,6) inversion lines toward the prototypical Seyfert 2 galaxy NGC 1068, made with the Green Bank Telescope (GBT). This is the first detection of ammonia in a Seyfert galaxy. The ortho-to-para-NH3 abundance ratio suggests that the molecule was formed in a warm medium of at least 20 K. For the NH3 column density and fractional abundance, we find (1.09\pm0.23)\times10^14 cm^-2 and (2.9\pm0.6)\times10^-8, respectively, from the inner 1.2 kpc of NGC 1068. The kinetic temperature can be constrained to 80\pm20 K for the bulk of the molecular gas, while some fraction has an even higher temperature of 140\pm30 K.Comment: 5 pages, 3 figures, accepted by A&