Quantum Reciprocity Conjecture for the Non-Equilibrium Steady State

By considering the lack of history dependence in the non-equilibrium steady state of a quantum system we are led to conjecture that in such a system, there is a set of quantum mechanical observables whose retarded response functions are insensitive to the arrow of time, and which consequently satisfy a quantum analog of the Onsager reciprocity relations. Systems which satisfy this conjecture can be described by an effective Free energy functional. We demonstrate that the conjecture holds in a resonant level model of a multi-lead quantum dot.Comment: References revised to take account of related work on Onsager reciprocity in mesoscopics by Christen, and in hydrodynamics by Mclennan, Dufty and Rub

Exact solutions for equilibrium configurations of charged conducting liquid jets

A wide class of exact solutions is obtained for the problem of finding the equilibrium configurations of charged jets of a conducting liquid; these configurations correspond to the finite-amplitude azimuthal deformations of the surface of a round jet. A critical value of the linear electric charge density is determined, for which the jet surface becomes self-intersecting, and the jet splits into two. It exceeds the density value required for the excitation of the linear azimuthal instability of the round jet. Hence, there exists a range of linear charge density values, where our solutions may be stable with respect to small azimuthal perturbations.Comment: 7 pages, 5 figures, to appear in Physical Review

Magnetic hysteresis in Ising-like dipole-dipole model

Using zero temperature Monte Carlo simulations we have studied the magnetic hysteresis in a three-dimensional Ising model with nearest neighbor exchange and dipolar interaction. The average magnetization of spins located inside a sphere on a cubic lattice is determined as a function of magnetic field varied periodically. The simulations have justified the appearance of hysteresis and allowed us to have a deeper insight into the series of metastable states developed during this process.Comment: REVTEX, 10 pages including 4 figure

On the stability of general relativistic geometric thin disks

The stability of general relativistic thin disks is investigated under a general first order perturbation of the energy momentum tensor. In particular, we consider temporal, radial and azimuthal "test matter" perturbations of the quantities involved on the plane $z=0$. We study the thin disks generated by applying the "displace, cut and reflect" method, usually known as the image method, to the Schwarzschild metric in isotropic coordinates and to the Chazy-Curzon metric and the Zipoy-Voorhees metric ($\gamma$-metric) in Weyl coordinates. In the case of the isotropic Schwarzschild thin disk, where a radial pressure is present to support the gravitational attraction, the disk is stable and the perturbation favors the formation of rings. Also, we found the expected result that the thin disk models generated by the Chazy-Curzon and Zipoy-Voorhees metric with only azimuthal pressure are not stable under a general first order perturbationComment: 11 pages, RevTex. Phys Rev D (in press

Transparent Anomalous Dispersion and Superluminal Light Pulse Propagation at a Negative Group Velocity

Anomalous dispersion cannot occur in a transparent passive medium where electromagnetic radiation is being absorbed at all frequencies, as pointed out by Landau and Lifshitz. Here we show, both theoretically and experimentally, that transparent linear anomalous dispersion can occur when a gain doublet is present. Therefore, a superluminal light pulse propagation can be observed even at a negative group velocity through a transparent medium with almost no pulse distortion. Consequently, a {\it negative transit time} is experimentally observed resulting in the peak of the incident light pulse to exit the medium even before entering it. This counterintuitive effect is a direct result of the {\it rephasing} process owing to the wave nature of light and is not at odds with either causality or Einstein's theory of special relativity.Comment: 12 journal pages, 9 figure

Sonoluminescence and collapse dynamics of multielectron bubbles in helium

Multielectron bubbles (MEBs) differ from gas-filled bubbles in that it is the Coulomb repulsion of a nanometer thin layer of electrons that forces the bubble open rather than the pressure of an enclosed gas. We analyze the implosion of MEBs subjected to a pressure step, and find that despite the difference in the underlying processes the collapse dynamics is similar to that of gas-filled bubbles. When the MEB collapses, the electrons inside it undergo strong accelerations, leading to the emission of radiation. This type of sonoluminescence does not involve heating and ionisation of any gas inside the bubble. We investigate the conditions necessary to obtain sonoluminescence from multielectron bubbles and calculate the power spectrum of the emitted radiation.Comment: 6 figure

On the pearl size of hydrophobic polyelectrolytes

Hydrophobic polyelectrolytes have been predicted to adopt an unique pearl-necklace conformation in aqueous solvents. We present in this Letter an attempt to characterise quantitatively this conformation with a focus on $D_p$, the pearl size. For this purpose polystyrenesulfonate (PSS) of various effective charge fractions $f_{eff}$ and chain lengths $N$ has been adsorbed onto oppositely charged surfaces immersed in water in condition where the bulk structure is expected to persist in the adsorbed state. \emph{In situ} ellipsometry has provided an apparent thickness $h_{app}$ of the PSS layer. In the presence of added salts, we have found: $h_{app}\sim aN^{0}f_{eff}^{-2/3}$ ($a$ is the monomer size) in agreement with the scaling predictions for $D_p$ in the pearl-necklace model if one interprets $h_{app}$ as a measure of the pearl size. At the lowest charge fractions we have found $h_{app}\sim aN^{1/3}$ for the shorter chains, in agreement with a necklace/globule transition.Comment: 7 pages, 4 figures, 1 table. Published in Europhysics Letters, Vol. 62, Number 1, pp. 110-116 (2003

Diffusion and Transport Coefficients in Synthetic Opals

Opals are structures composed of the closed packing of spheres in the size range of nano-to-micro meter. They are sintered to create small necks at the points of contact. We have solved the diffusion problem in such structures. The relation between the diffusion coefficient and the termal and electrical conductivity makes possible to estimate the transport coefficients of opal structures. We estimate this changes as function of the neck size and the mean-free path of the carriers. The theory presented is also applicable to the diffusion problem in other periodic structures.Comment: Submitted to PR

Robin conditions on the Euclidean ball

Techniques are presented for calculating directly the scalar functional determinant on the Euclidean d-ball. General formulae are given for Dirichlet and Robin boundary conditions. The method involves a large mass asymptotic limit which is carried out in detail for d=2 and d=4 incidentally producing some specific summations and identities. Extensive use is made of the Watson-Kober summation formula.Comment: 36p,JyTex, misprints corrected and a section on the massive case adde