Polarizability and dynamic structure factor of the one-dimensional Bose gas near the Tonks-Girardeau limit at finite temperatures

Correlation functions related to the dynamic density response of the one-dimensional Bose gas in the model of Lieb and Liniger are calculated. An exact Bose-Fermi mapping is used to work in a fermionic representation with a pseudopotential Hamiltonian. The Hartree-Fock and generalized random phase approximations are derived and the dynamic polarizability is calculated. The results are valid to first order in 1/\gamma where \gamma is Lieb-Liniger coupling parameter. Approximations for the dynamic and static structure factor at finite temperature are presented. The results preclude superfluidity at any finite temperature in the large-\gamma regime due to the Landau criterion. Due to the exact Bose-Fermi duality, the results apply for spinless fermions with weak p-wave interactions as well as for strongly interacting bosons.Comment: 13 pages, 5 figures, the journal versio

Two-Photon Spiral Imaging with Correlated Orbital Angular Momentum States

The concept of correlated two-photon spiral imaging is introduced. We begin by analyzing the joint orbital angular momentum (OAM) spectrum of correlated photon pairs. The mutual information carried by the photon pairs is evaluated, and it is shown that when an object is placed in one of the beam paths the value of the mutual information is strongly dependent on object shape and is closely related to the degree of rotational symmetry present. After analyzing the effect of the object on the OAM correlations, the method of correlated spiral imaging is described. We first present a version using parametric downconversion, in which entangled pairs of photons with opposite OAM values are produced, placing an object in the path of one beam. We then present a classical (correlated, but non-entangled) version. The relative problems and benefits of the classical versus entangled configurations are discussed. The prospect is raised of carrying out compressive imaging via twophoton OAM detection to reconstruct sparse objects with few measurements

Can the unresolved X-ray background be explained by emission from the optically-detected faint galaxies of the GOODS project?

The emission from individual X-ray sources in the Chandra Deep Fields and XMM-Newton Lockman Hole shows that almost half of the hard X-ray background above 6 keV is unresolved and implies the existence of a missing population of heavily obscured active galactic nuclei (AGN). We have stacked the 0.5-8 keV X-ray emission from optical sources in the Great Observatories Origins Deep Survey (GOODS; which covers the Chandra Deep Fields) to determine whether these galaxies, which are individually undetected in X-rays, are hosting the hypothesised missing AGN. In the 0.5-6 keV energy range the stacked-source emission corresponds to the remaining 10-20 per cent of the total background -- the fraction that has not been resolved by Chandra. The spectrum of the stacked emission is consistent with starburst activity or weak AGN emission. In the 6-8 keV band, we find that upper limits to the stacked X-ray intensity from the GOODS galaxies are consistent with the ~40 per cent of the total background that remains unresolved, but further selection refinement is required to identify the X-ray sources and confirm their contribution.Comment: 7 pages, 1 figure, accepted for publication in MNRA

Supernova Reverse Shocks and SiC Growth

We present new mechanisms by which the isotopic compositions of X-type grains of presolar SiC are altered by reverse shocks in Type II supernovae. We address three epochs of reverse shocks: pressure wave from the H envelope near t = 10$^6$s; reverse shock from the presupernova wind near 10$^8-10^9$s; reverse shock from the ISM near 10$^{10}$s. Using 1-D hydrodynamics we show that the first creates a dense shell of Si and C atoms near 10$^6$s in which the SiC surely condenses. The second reverse shock causes precondensed grains to move rapidly forward through decelerated gas of different isotopic composition, during which implantation, sputtering and further condensation occur simultaneously. The third reverse shock causes only further ion implantation and sputtering, which may affect trace element isotopic compositions. Using a 25M$_{\odot}$ supernova model we propose solutions to the following unsolved questions: where does SiC condense?; why does SiC condense in preference to graphite?; why is condensed SiC $^{28}$Si-rich?; why is O richness no obstacle to SiC condensation?; how many atoms of each isotope are impacted by a grain that condenses at time t$_0$ at radial coordinate r$_0$? These many considerations are put forward as a road map for interpreting SiC X grains found in meteorites and their meaning for supernova physics.Comment: 28 pages, 14 figures, animation for Figure 3 and machine-readable Table 3 can be found at http://antares.steelangel.com/~edeneau/supernova/DHC_2003, Submitted to Ap

Estimating subseasonal variability and trends in global atmosphere using reanalysis data

A new measure of subseasonal variability is introduced that provides a scale-dependent estimation of vertically and meridionally integrated atmospheric variability in terms of the normal modes of linearized primitive equations. Applied to the ERA-Interim data, the new measure shows that subseasonal variability decreases for larger zonal wave numbers. Most of variability is due to balanced (Rossby mode) dynamics but the portion associated with the inertio-gravity (IG) modes increases as the scale reduces. Time series of globally integrated variability anomalies in ERA-Interim show an increase in variability after year 2000. In recent years the anomalies have been about 2% above the 1981–2010 average. The relative increase in variability projecting on the IG modes is larger and more persistent than for the Rossby modes. Although the IG part is a small component of the subseasonal variability, it is an important effect likely reflecting the observed increase in the tropical precipitation variability. ©2018. The Authors

Noise spectroscopy and interlayer phase-coherence in bilayer quantum Hall systems

Bilayer quantum Hall systems develop strong interlayer phase-coherence when the distance between layers is comparable to the typical distance between electrons within a layer. The phase-coherent state has until now been investigated primarily via transport measurements. We argue here that interlayer current and charge-imbalance noise studies in these systems will be able to address some of the key experimental questions. We show that the characteristic frequency of current-noise is that of the zero wavevector collective mode, which is sensitive to the degree of order in the system. Local electric potential noise measured in a plane above the bilayer system on the other hand is sensitive to finite-wavevector collective modes and hence to the soft-magnetoroton picture of the order-disorder phase transition.Comment: 5 pages, 2 figure

Undoing a weak quantum measurement of a solid-state qubit

We propose an experiment which demonstrates the undoing of a weak continuous measurement of a solid-state qubit, so that any unknown initial state is fully restored. The undoing procedure has only a finite probability of success because of the non-unitary nature of quantum measurement, though it is accompanied by a clear experimental indication of whether or not the undoing has been successful. The probability of success decreases with increasing strength of the measurement, reaching zero for a traditional projective measurement. Measurement undoing (``quantum un-demolition'') may be interpreted as a kind of a quantum eraser, in which the information obtained from the first measurement is erased by the second measurement, which is an essential part of the undoing procedure. The experiment can be realized using quantum dot (charge) or superconducting (phase) qubits.Comment: 5 page

Fact: Many SCUBA galaxies harbour AGNs

Deep SCUBA surveys have uncovered a large population of ultra-luminous galaxies at z>1. These sources are often assumed to be starburst galaxies, but there is growing evidence that a substantial fraction host an AGN (i.e., an accreting super-massive black hole). We present here possibly the strongest evidence for this viewpoint to date: the combination of ultra-deep X-ray observations (the 2 Ms Chandra Deep Field-North) and deep optical spectroscopic data. We argue that upward of 38% of bright (f850um>=5mJy) SCUBA galaxies host an AGN, a fraction of which are obscured QSOs (i.e., L_X>3x10^{44} erg/s). However, using evidence from a variety of analyses, we argue that in almost all cases the AGNs are not bolometrically important (i.e., <20%). Thus, star formation appears to dominate their bolometric output. A substantial fraction of bright SCUBA galaxies show evidence for binary AGN activity. Since these systems appear to be interacting and merging at optical/near-IR wavelengths, their super-massive black holes will eventually coalesce.Comment: Invited contribution - 10 pages, 4 figures, to appear in the Proceedings of the ESO/USM/MPE Workshop on "Multiwavelength Mapping of Galaxy Formation and Evolution", eds. R. Bender and A. Renzin