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

High-pressure melting behavior of tin up to 105 GPa

The melting curve of Sn initially rises steeply as a function of pressure but exhibits a decrease in slope (dTm/dP) above 40 GPa to become nearly flat above 50 GPa. Previous studies have argued that a body-centered tetragonal (bct) to cubic (bcc) phase transition occurs in this range at room temperature. However, our investigations have shown that the phase behavior is more complex in this region with orthorhombic (bco) splitting of reflections occurring in the x-ray diffraction pattern above 32 GPa and coexisting diffraction signatures of bco and bcc structures are observed between 40 and 70 GPa. Here we have documented the simultaneous presence of bco and bcc reflections up to the melting point, negating the possibility that their coexistence might indicate a kinetically hindered first-order phase transformation. In this paper we have extended the observation of Sn melting relations into the megabar (P>100 GPa) range using the appearance of liquid diffuse scattering in x-ray diffraction patterns and discontinuities during thermal signal processing to diagnose the occurrence of melting. Both techniques yield consistent results that indicate the melting line maintains the same low slope up to the highest pressure examined and does not flatten. The results below approximately 40 GPa agree well with the melting relations produced recently using a multiphase equation of state fitted to available or assumed data. Above this pressure the experimental melting points lie increasingly below the predicted crystal-liquid phase boundary, but above the flat melting from past studies, indicating that the thermodynamic properties of the body-centered “γ”-Sn structure remain to be clarified

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

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

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

Mid-Infrared Spectral Diagnostics of Luminous Infrared Galaxies

We present a statistical analysis of the mid-infrared (MIR) spectra of 248 luminous infrared (IR) galaxies (LIRGs) which comprise the Great Observatories All-sky LIRG Survey (GOALS) observed with the Infrared Spectrograph (IRS) on-board the Spitzer Space Telescope. The GOALS sample enables a direct measurement of the relative contributions of star-formation and active galactic nuclei (AGN) to the total IR emission from a large sample of local LIRGs. The AGN contribution to the MIR emission (f-AGN) is estimated by employing several diagnostics based on the properties of the [NeV], [OIV] and [NeII] fine structure gas emission lines, the 6.2 microns PAH and the shape of the MIR continuum. We find that 18% of all LIRGs contain an AGN and that in 10% of all sources the AGN contributes more than 50% of the total IR luminosity. Summing up the total IR luminosity contributed by AGN in all our sources suggests that AGN supply ~12% of the total energy emitted by LIRGs. The average spectrum of sources with an AGN looks similar to the average spectrum of sources without an AGN, but it has lower PAH emission and a flatter MIR continuum. AGN dominated LIRGs have higher IR luminosities, warmer MIR colors and are found in interacting systems more often than pure starbursts LIRGs. However we find no linear correlations between these properties and f-AGN. We used the IRAC colors of LIRGs to confirm that finding AGN on the basis of their MIR colors may miss ~40% of AGN dominated (U)LIRGsComment: accepted for publication in ApJ, 34 pages, 12 figure

Recombinant Fibrinogen Studies Reveal That Thrombin Specificity Dictates Order of Fibrinopeptide Release

During cleavage of fibrinogen by thrombin, fibrinopeptide A (FpA) release precedes fibrinopeptide B (FpB) release. To examine the basis for this ordered release, we synthesized A'beta fibrinogen, replacing FpB with a fibrinopeptide A-like peptide, FpA' (G14V). Analyses of fibrinopeptide release from A'beta fibrinogen showed that FpA release and FpA' release were similar; the release of either peptide followed simple first-order kinetics. Specificity constants for FpA and FpA' were similar, demonstrating that these peptides are equally competitive substrates for thrombin. In the presence of Gly-Pro-Arg-Pro, an inhibitor of fibrin polymerization, the rate of FpB release from normal fibrinogen was reduced 3-fold, consistent with previous data; in contrast, the rate of FpA' release from A'beta fibrinogen was unaffected. Thus, with A'beta fibrinogen, fibrinopeptide release from the beta chain is similar to fibrinopeptide release from the alpha chain. We conclude that the ordered release of fibrinopeptides is dictated by the specificity of thrombin for its substrates. We analyzed polymerization, following changes in turbidity, and found that polymerization of A'beta fibrinogen was similar to that of normal fibrinogen. We analyzed clot structure by scanning electron microscopy and found that clots from A'beta fibrinogen were similar to clots from normal fibrinogen. We conclude that premature release of the fibrinopeptide from the N terminus of the beta chain does not affect polymerization of fibrinogen

HIFI observations of warm gas in DR21: Shock versus radiative heating

The molecular gas in the DR21 massive star formation region is known to be affected by the strong UV field from the central star cluster and by a fast outflow creating a bright shock. The relative contribution of both heating mechanisms is the matter of a long debate. By better sampling the excitation ladder of various tracers we provide a quantitative distinction between the different heating mechanisms. HIFI observations of mid-J transitions of CO and HCO+ isotopes allow us to bridge the gap in excitation energies between observations from the ground, characterizing the cooler gas, and existing ISO LWS spectra, constraining the properties of the hot gas. Comparing the detailed line profiles allows to identify the physical structure of the different components. In spite of the known shock-excitation of H2 and the clearly visible strong outflow, we find that the emission of all lines up to > 2 THz can be explained by purely radiative heating of the material. However, the new Herschel/HIFI observations reveal two types of excitation conditions. We find hot and dense clumps close to the central cluster, probably dynamically affected by the outflow, and a more widespread distribution of cooler, but nevertheless dense, molecular clumps.Comment: Accepted for publication by A&

The [CII] 158 um Line Deficit in Ultraluminous Infrared Galaxies Revisited

We present a study of the [CII] 157.74 um fine-structure line in a sample of 15 ultraluminous infrared (IR) galaxies (L_IR>10^12 Lsun; ULIRGs) using the Long Wavelength Spectrometer (LWS) on the Infrared Space Observatory (ISO). We confirm the observed order of magnitude deficit (compared to normal and starburst galaxies) in the strength of the [CII] line relative to the far-IR dust continuum emission found in our initial report (Luhman et al. 1998), but here with a sample that is twice as large. This result suggests that the deficit is a general phenomenon affecting 4/5 ULIRGs. We present an analysis using observations of generally acknowledged photodissociation region (PDR) tracers ([CII], [OI] 63 and 145 um, and FIR continuum emission), which suggests that a high UV flux G_o incident on a moderate density n PDR could explain the deficit. However, comparisons with other ULIRG observations, including CO (1-0), [CI] (1-0), and 6.2 um polycyclic aromatic hydrocarbon (PAH) emission, suggest that high G_o/n PDRs alone cannot produce a self-consistent solution that is compatible with all of the observations. We propose that non-PDR contributions to the FIR continuum can explain the apparent [CII] deficiency. Here, unusually high G_o and/or n physical conditions in ULIRGs as compared to those in normal and starburst galaxies are not required to explain the [CII] deficit. Dust-bounded photoionization regions, which generate much of the FIR emission but do not contribute significant [CII] emission, offer one possible physical origin for this additional non-PDR component. Such environments may also contribute to the observed suppression of FIR fine-structure emission from ionized gas and PAHs, as well as the warmer FIR colors found in ULIRGs. The implications for observations at higher redshifts are also revisited.Comment: to be published in The Astrophysical Journal, 58 page

Charge-Induced Fragmentation of Sodium Clusters

The fission of highly charged sodium clusters with fissilities X>1 is studied by {\em ab initio} molecular dynamics. Na_{24}^{4+} is found to undergo predominantly sequential Na_{3}^{+} emission on a time scale of 1 ps, while Na_{24}^{Q+} (5 \leq Q \leq 8) undergoes multifragmentation on a time scale \geq 0.1 ps, with Na^{+} increasingly the dominant fragment as Q increases. All singly-charged fragments Na_{n}^{+} up to size n=6 are observed. The observed fragment spectrum is, within statistical error, independent of the temperature T of the parent cluster for T \leq 1500 K. These findings are consistent with and explain recent trends observed experimentally.Comment: To appear in Physical Review Letter