Generation of pulse trains in the normal dispersion regime of a dielectric medium using a relaxing nonlinearity

We show that modulation-type instability can occur in the normal dispersion regime of a dielectric medium for the case of a relaxing self-focusing nonlinearity. This instability leads to the generation of pulse trains with almost no pedestal when periodic boundary conditions are applied. © 1991 American Institute of PhysicsThis work was supported by the Joint Services Optical Program of the Air Force Office of Scientific Research and the Army Research Office, the Army Research Office (DAAL03-88-KOO66), and J. M. Soto-Crespo acknowl- edges a grant from the Ministerio de Education y Ciencia, Spain.Peer Reviewe

Fair Value Accounting: Current Status And A Proposal For Convergence

Accounting for fair values is a complex subject full of controversial recognition, measurement, and reporting rules. This paper first analyzes the current status of fair value accounting, highlighting the criticisms of the current fair value accounting standards. Next, the U.S. and international standards are discussed to highlight the areas where they differ. Finally, an accounting approach for fair values is proposed that reports the economic reality and the financial condition of a firm and may be used to achieve global convergence

Gas Excitation in ULIRGS: Maps of Diagnostic Emission-Line Ratios in Space and Velocity

Emission-line spectra extracted at multiple locations across 39 ultraluminous infrared galaxies have been compiled into a spectrophotometric atlas. Line profiles of H alpha, [N II], [S II], [O I], H beta, and [O III] are resolved and fit jointly with common velocity components. Diagnostic ratios of these line fluxes are presented in a series of plots, showing how the Doppler shift, line width, gas excitation, and surface brightness change with velocity at fixed position and also with distance from the nucleus. One general characteristic of these spectra is the presence of shocked gas extending many kiloparsecs from the nucleus. In some systems, the shocked gas appears as part of a galactic gas disk based on its rotation curve. These gas disks appear primarily during the early stages of the merger. The general characteristics of the integrated spectra are also presented.Comment: Submitted to ApJS. The first 10 pages are writeup. Also included are 3 appendices (91 pages) that include a large sample of figures and tables intended for the online only version of the publication. 101 pages total, 5 figures, 2 figure sets (39 subfigures each), 5 tables. This is a companion paper to "The Emission-Line Spectra of Major Mergers: Evidence for Shocked Outflows" by Soto et al. 201

Stability of solitons in PT-symmetric couplers

Families of analytical solutions are found for symmetric and antisymmetric solitons in the dual-core system with the Kerr nonlinearity and PT-balanced gain and loss. The crucial issue is stability of the solitons. A stability region is obtained in an analytical form, and verified by simulations, for the PT-symmetric solitons. For the antisymmetric ones, the stability border is found in a numerical form. Moving solitons of both types collide elastically. The two soliton species merge into one in the "supersymmetric" case, with equal coefficients of the gain, loss and inter-core coupling. These solitons feature a subexponential instability, which may be suppressed by periodic switching ("management").Comment: Optics Letters 2011 (in press

Evidence of Andreev bound states as a hallmark of the FFLO phase in κ\kappa-(BEDT-TTF)2_2Cu(NCS)2_2

Superconductivity is a quantum phenomena arising, in its simplest form, from pairing of fermions with opposite spin into a state with zero net momentum. Whether superconductivity can occur in fermionic systems with unequal number of two species distinguished by spin, atomic hyperfine states, flavor, presents an important open question in condensed matter, cold atoms, and quantum chromodynamics, physics. In the former case the imbalance between spin-up and spin-down electrons forming the Cooper pairs is indyced by the magnetic field. Nearly fifty years ago Fulde, Ferrell, Larkin and Ovchinnikov (FFLO) proposed that such imbalanced system can lead to exotic superconductivity in which pairs acquire finite momentum. The finite pair momentum leads to spatially inhomogeneous state consisting of of a periodic alternation of "normal" and "superconducting" regions. Here, we report nuclear magnetic resonance (NMR) measurements providing microscopic evidence for the existence of this new superconducting state through the observation of spin-polarized quasiparticles forming so-called Andreev bound states.Comment: 6 pages, 5 fig

One more neighbor: The first brown dwarf in the VVV survey

Context. The discovery of brown dwarfs (BDs) in the solar neighborhood and young star clusters has helped to constraint the low-mass end of the stellar mass function and the initial mass function. We use data of the Vista Variables in the V\'ia L\'actea (VVV), a near-infrared (NIR) multiwavelength (Z Y J H Ks) multi-epoch (Ks) ESO Public Survey mapping the Milky Way bulge and southern Galactic plane to search for nearby BDs. Aims. The ultimate aim of the project is to improve the completeness of the census of nearby stellar and substellar objects towards the Galactic bulge and inner disk regions. Methods. Taking advantage of the homogeneous sample of VVV multi-epoch data, we identified stars with high proper motion (> 0.1"/yr), and then selected low-mass objects using NIR colors. We searched for a possible parallax signature using the all available Ks band epochs. We set some constraints on the month-to-year scale Ks band variability of our candidates, and even searched for possible transiting companions. We obtained NIR spectra to properly classify spectral type and then the physical properties of the final list of candidates. Results. We report the discovery of VVV BD001, a new member of the local volume-limited sample (within 20pc from the sun) with well defined proper motion, distance, and luminosity. The spectral type of this new object is an L5+-1, unusually blue dwarf. The proper motion for this BD is PM(\alpha)=-0.5455+-0.004 "/yr, PM(\delta)=-0.3255+-0.004 "/yr, and it has a parallax of 57+-4 mas which translates into a distance of 17.5 +- 1.1 pc. VVV BD001 shows no evidence of variability (\Delta Ks <0.05mag) over two years, especially constrained on a six month scale during the year 2012.Comment: 5 pages, 4 figures, 1 table, Accepted for publication in Astronomy and Astrophysics Letter

Seasonal and inter-annual variability in nutrient supply in relation to mixing in the Bay of Biscay

Post-print

Automated measurement of redshift from mid-infrared low resolution spectroscopy

We present a new SED-fitting based routine for redshift determination that is optimised for mid-infrared (MIR) low-resolution spectroscopy. Its flexible template scaling increases the sensitivity to slope changes and small scale features in the spectrum, while a new selection algorithm called Maximum Combined Pseudo-Likelihood (MCPL) provides increased accuracy and a lower number of outliers compared to the standard maximum-likelihood (ML) approach. Unlike ML, MCPL searches for local (instead of absolute) maxima of a 'pseudo-likelihood' (PL) function, and combines results obtained for all the templates in the library to weed out spurious redshift solutions. The capabilities of MCPL are demonstrated by comparing its results to those of regular ML and to the optical spectroscopic redshifts of a sample of 491 Spitzer/IRS spectra from sources at 0<z<3.7. MCPL achieves a redshift accuracy dz/(1+z)<0.005 for 78% of the galaxies in the sample compared to 68% for ML. The rate of outliers (dz/(1+z)>0.02) is 14% for MCPL and 22% for ML. chi^2 values for ML solutions are found to correlate with the SNR of the spectra, but not with redshift accuracy. By contrast, the peak value of the normalised combined PL (gamma) is found to provide a good indication on the reliability of the MCPL solution for individual sources. The accuracy and reliability of the redshifts depends strongly on the MIR SED. Sources with significant polycyclic aromatic hydrocarbon emission obtain much better results compared to sources dominated by AGN continuum. Nevertheless, for a given gamma the frequency of accurate solutions and outliers is largely independent on their SED type. This reliability indicator for MCPL solutions allows to select subsamples with highly reliable redshifts. In particular, a gamma>0.15 threshold retains 79% of the sources with dz/(1+z)<0.005 while reducing the outlier rate to 3.8% (abridged).Comment: 23 pages, 12 figures, 5 tables. Accepted for publication in MNRA

Automated measurement of redshift from mid-infrared low resolution spectroscopy

We present a new SED-fitting based routine for redshift determination that is optimised for mid-infrared (MIR) low-resolution spectroscopy. Its flexible template scaling increases the sensitivity to slope changes and small scale features in the spectrum, while a new selection algorithm called Maximum Combined Pseudo-Likelihood (MCPL) provides increased accuracy and a lower number of outliers compared to the standard maximum-likelihood (ML) approach. Unlike ML, MCPL searches for local (instead of absolute) maxima of a 'pseudo-likelihood' (PL) function, and combines results obtained for all the templates in the library to weed out spurious redshift solutions. The capabilities of MCPL are demonstrated by comparing its results to those of regular ML and to the optical spectroscopic redshifts of a sample of 491 Spitzer/IRS spectra from sources at 0<z<3.7. MCPL achieves a redshift accuracy dz/(1+z)<0.005 for 78% of the galaxies in the sample compared to 68% for ML. The rate of outliers (dz/(1+z)>0.02) is 14% for MCPL and 22% for ML. chi^2 values for ML solutions are found to correlate with the SNR of the spectra, but not with redshift accuracy. By contrast, the peak value of the normalised combined PL (gamma) is found to provide a good indication on the reliability of the MCPL solution for individual sources. The accuracy and reliability of the redshifts depends strongly on the MIR SED. Sources with significant polycyclic aromatic hydrocarbon emission obtain much better results compared to sources dominated by AGN continuum. Nevertheless, for a given gamma the frequency of accurate solutions and outliers is largely independent on their SED type. This reliability indicator for MCPL solutions allows to select subsamples with highly reliable redshifts. In particular, a gamma>0.15 threshold retains 79% of the sources with dz/(1+z)<0.005 while reducing the outlier rate to 3.8% (abridged).Comment: 23 pages, 12 figures, 5 tables. Accepted for publication in MNRA

Using the 1.6um Bump to Study Rest-frame NIR Selected Galaxies at Redshift 2

We explore the feasibility and limitations of using the 1.6um bump as a photometric redshift indicator and selection technique and use it to study the rest-frame H-band galaxy luminosity and stellar mass functions at redshift z~2. We use publicly available Spitzer/IRAC images in the GOODS fields and find that color selection in the IRAC bandpasses alone is comparable in completeness and contamination to BzK selection. We find that the shape of the 1.6um bump is robust, and photometric redshifts are not greatly affected by choice of model parameters. Comparison with spectroscopic redshifts shows photometric redshifts to be reliable. We create a rest-frame NIR selected catalog of galaxies at z~2 and construct a galaxy stellar mass function (SMF). Comparisons with other SMFs at approximately the same redshift but determined using shorter wavelengths show good agreement. This agreement suggests that selection at bluer wavelengths does not miss a significant amount of stellar mass in passive galaxies. Comparison with SMFs at other redshifts shows evidence for the downsizing scenario of galaxy evolution. We conclude by pointing out the potential for using the 1.6um technique to select high-redshift galaxies with the JWST, whose lambda > 0.6 um coverage will not be well suited to selecting galaxies using techniques that require imaging at shorter wavelengths.Comment: Accepted for publication in Ap