The Crooks relation in optical spectra - universality in work distributions for weak local quenches

We show that work distributions and non-equilibrium work fluctuation theorems can be measured in optical spectra for a wide class of quantum systems. We consider systems where the absorption or emission of a photon corresponds to the sudden switch on or off of a local perturbation. For the particular case of a weak local perturbation, the Crooks relation establishes a universal relation in absorption as well as in emission spectra. Due to a direct relation between the spectra and work distribution functions this is equivalent to universal relations in work distributions for weak local quenches. As two concrete examples we treat the X-ray edge problem and the Kondo exciton.Comment: 4+ pages, 1 figure; version as publishe

Describing many-body localized systems in thermal environments

In this work we formulate an efficient method for the description of fully many-body localized systems in weak contact with thermal environments at temperature T. The key idea is to exploit the representation of the system in terms of quasi-local integrals of motion (l-bits) to efficiently derive the generator for the quantum master equation in Born-Markov approximation. We, moreover, show how to compute the steady state of this equation efficiently by using quantum-jump Monte-Carlo techniques as well as by deriving approximate kinetic equations of motion. As an example, we consider a one-dimensional disordered extended Hubbard model for spinless fermions, for which we derive the l-bit representation approximately by employing a recently proposed method valid in the limit of strong disorder and weak interactions. Coupling the system to a global thermal bath, we study the transport between two leads with different chemical potentials at both of its ends. We find that the temperature-dependent current is captured by an interaction-dependent version of Mott's law for variable range hopping, where transport is enhanced/lowered depending on whether the interactions are attractive or repulsive, respectively. We interpret these results in terms of spatio-energetic correlations between the l-bits

Polarization Evolution in Strong Magnetic Fields

Extremely strong magnetic fields change the vacuum index of refraction. Although this polarization dependent effect is small for typical neutron stars, it is large enough to decouple the polarization states of photons traveling within the field. The photon states evolve adiabatically and follow the changing magnetic field direction. The combination of a rotating magnetosphere and a frequency dependent state decoupling predicts polarization phase lags between different wave bands, if the emission process takes place well within the light cylinder. This QED effect may allow observations to distinguish between different pulsar emission mechanisms and to reconstruct the structure of the magnetosphere.Comment: 22 pages, 10 figures, accepted for publication in MNRA

How Common Are Magnetars? The Consequences of Magnetic-Field Decay

Ultramagnetized neutron stars or magnetars have been invoked to explain several astrophysical phenomena. We examine how the magnetic field of a magnetar will decay over time and how this decay affects the cooling of the object. We find that for sufficiently strong nascent fields, field decay alters the cooling evolution significantly relative to similarly magnetized neutron stars with constant fields. As a result, old magnetars can be expected to be bright in the soft X-ray band. The soft X-ray source RXJ~0720.4$-$3125 may well be the nearest such old magnetar.Comment: 7 pages, 1 figure, accepted for publication in Ap. J. Letter

Dynamical Quantum Phase Transitions in the Transverse Field Ising Model

A phase transition indicates a sudden change in the properties of a large system. For temperature-driven phase transitions this is related to non-analytic behavior of the free energy density at the critical temperature: The knowledge of the free energy density in one phase is insufficient to predict the properties of the other phase. In this paper we show that a close analogue of this behavior can occur in the real time evolution of quantum systems, namely non-analytic behavior at a critical time. We denote such behavior a dynamical phase transition and explore its properties in the transverse field Ising model. Specifically, we show that the equilibrium quantum phase transition and the dynamical phase transition in this model are intimately related.Comment: 4+4 pages, 4 figures, Appendix adde

Magnetar giant flare high-energy emission

High energy ($> 250$ keV) emission has been detected persisting for several tens of seconds after the initial spike of magnetar giant flares. It has been conjectured that this emission might arise via inverse Compton scattering in a highly extended corona generated by super-Eddington outflows high up in the magnetosphere. In this paper we undertake a detailed examination of this model. We investigate the properties of the required scatterers, and whether the mechanism is consistent with the degree of pulsed emission observed in the tail of the giant flare. We conclude that the mechanism is consistent with current data, although the origin of the scattering population remains an open question. We propose an alternative picture in which the emission is closer to that star and is dominated by synchrotron radiation. The $RHESSI$ observations of the December 2004 flare modestly favor this latter picture. We assess the prospects for the Fermi Gamma-Ray Space Telescope to detect and characterize a similar high energy component in a future giant flare. Such a detection should help to resolve some of the outstanding issues.Comment: 20 pages, 14 figure

1RXS J214303.7+065419/RBS 1774: A New Isolated Neutron Star Candidate

We report on the identification of a new possible Isolated Neutron Star candidate in archival ROSAT observations. The source 1RXS J214303.7+065419, listed in the ROSAT Bright Survey as RBS 1774, is very soft, exhibits a thermal spectrum well fitted by a blackbody at ${T}\sim 90$ eV and has a low column density, ${N_H}\sim 5\times 10^{20}$ ${cm}^{-2}$. Catalogue searches revealed no known sources in other energy bands close to the X-ray position of RBS 1774. Follow-up optical observations with NTT showed no peculiar object within the X-ray error circle. The absence of any plausible optical counterpart down to ${m_R}\sim 23$ results in an X-ray to optical flux ratio in excess of 1000.Comment: LaTeX (A&A style files), 5 pages, 3 figures. Accepted for publication in Astronomy and Astrophysics Letters. Minor correction

Handling and analysis of ices in cryostats and glove boxes in view of cometary samples

Comet nucleus sample return mission and other return missions from planets and satellites need equipment for handling and analysis of icy samples at low temperatures under vacuum or protective gas. Two methods are reported which were developed for analysis of small icy samples and which are modified for larger samples in cometary matter simulation experiments (KOSI). A conventional optical cryostat system was modified to allow for transport of samples at 5 K, ion beam irradiation, and measurement in an off-line optical spectrophotometer. The new system consists of a removable window plug containing nozzles for condensation of water and volatiles onto a cold finger. This plug can be removed in a vacuum system, changed against another plug (e.g., with other windows (IR, VIS, VUV) or other nozzles). While open, the samples can be treated under vacuum with cooling by manipulators (cut, removal, sample taking, irradiation with light, photons, or ions). After bringing the plug back, the samples can be moved to another site of analysis. For handling the 30 cm diameter mineral-ice samples from the KOSI experiments an 80x80x80 cm glove box made out of plexiglass was used. The samples were kept in a liquid nitrogen bath, which was filled from the outside. A stream a dry N2 and evaporating gas from the bath purified the glove box from impurity gases and, in particular, H2O, which otherwise would condense onto the samples

The oxygen-II luminosity density of the Universe

Equivalent widths of [OII] 3727 A lines are measured in 375 faint galaxy spectra taken as part of the Caltech Faint Galaxy Redshift Survey centered on the Hubble Deep Field. The sensitivity of the survey spectra to the [OII] line is computed as a function of magnitude, color and redshift. The luminosity function of galaxies in the [OII] line and the integrated luminosity density of the Universe in the [OII] line are computed as a function of redshift. It is found that the luminosity density in the [OII] line was a factor of ~10 higher at redshifts z~1 than it is at the present day. The simplest interpretation is that the star formation rate density of the Universe has declined dramatically since z~1.Comment: accepted for publication in Ap