Contrast Interferometry Using Bose-Einstein Condensates to Measure h/m and the Fine Structure Constant

The kinetic energy of an atom recoiling due to absorption of a photon was measured as a frequency using an interferometric technique called ``contrast interferometry''. Optical standing wave pulses were used as atom-optical elements to create a symmetric three-path interferometer with a Bose-Einstein condensate. The recoil phase accumulated in different paths was measured using a single-shot detection technique. The scheme allows for additional photon recoils within the interferometer and its symmetry suppresses several random and systematic errors including those from vibrations and ac Stark shifts. We have measured the photon recoil frequency of sodium to $7$ppm precision, using a simple realization of this scheme. Plausible extensions should yield a sufficient precision to bring within reach a ppb-level determination of $h/m$ and the fine structure constant $\alpha$

Quantum information storage and state transfer based on spin systems

The idea of quantum state storage is generalized to describe the coherent transfer of quantum information through a coherent data bus. In this universal framework, we comprehensively review our recent systematical investigations to explore the possibility of implementing the physical processes of quantum information storage and state transfer by using quantum spin systems, which may be an isotropic antiferromagnetic spin ladder system or a ferromagnetic Heisenberg spin chain. Our studies emphasize the physical mechanisms and the fundamental problems behind the various protocols for the storage and transfer of quantum information in solid state systems.Comment: 11 pages, 9 figures, Review article on the quantum spin based quantum information processing, to appear the special issue of Low Temperature Physics dedicated to the 70-th anniversary of creation of concept "antiferromagnetism" in physics of magnetis

PSR J1829+2456: a relativistic binary pulsar

We report the discovery of a new binary pulsar, PSR J1829+2456, found during a mid-latitude drift-scan survey with the Arecibo telescope. Our initial timing observations show the 41-ms pulsar to be in a 28-hr, slightly eccentric, binary orbit. The advance of periastron, omegadot = 0.28 +/- 0.01 deg/yr is derived from our timing observations spanning 200 days. Assuming that the advance of periastron is purely relativistic and a reasonable range of neutron star masses for PSR J1829+2456 we constrain the companion mass to be between 1.22 Msun and 1.38 Msun, making it likely to be another neutron star. We also place a firm upper limit on the pulsar mass of 1.38 Msun. The expected coalescence time due to gravitational-wave emission is long (~60 Gyr) and this system will not significantly impact upon calculations of merger rates that are relevant to upcoming instruments such as LIGO.Comment: Accepted MNRAS, 5 pages, 3 figure

Green functions and dimensional reduction of quantum fields on product manifolds

We discuss Euclidean Green functions on product manifolds P=NxM. We show that if M is compact then the Euclidean field on P can be approximated by its zero mode which is a Euclidean field on N. We estimate the remainder of this approximation. We show that for large distances on N the remainder is small. If P=R^{D-1}xS^{beta}, where S^{beta} is a circle of radius beta, then the result reduces to the well-known approximation of the D dimensional finite temperature quantum field theory to D-1 dimensional one in the high temperature limit. Analytic continuation of Euclidean fields is discussed briefly.Comment: 17 page

Partitioning of turbulent flux reveals contrasting cooling potential for woody vegetation and grassland during heat waves

© 2015 Royal Meteorological Society. We compared the capacity of woody versus grassy vegetation covers to buffer high temperatures during heat waves by partitioning turbulent heat between latent (λE) and sensible (H) fluxes, and quantifying advection using the Priestley-Taylor coefficient (α), for a16-year old grassland and an adjoining 6-year old plantation. We found that because λE dominated (>65%) the turbulent flux in the plantation and was at least twice as large as on the grassland (λE35°). Annual evapotranspiration was 54% lower from the grassland (384 mm) than from the plantation (834 mm). Woody vegetation covers dominated by broadleaved species are therefore preferred for buffering extreme high temperatures during heat waves and recommended for rehabilitating degraded landscapes in urban areas. We also present functions for approximating α for soil water limited conditions

The Triple Pulsar System PSR B1620-26 in M4

The millisecond pulsar PSR B1620-26, in the globular cluster M4, has a white dwarf companion in a half-year orbit. Anomalously large variations in the pulsar's apparent spin-down rate have suggested the presence of a second companion in a much wider orbit. Using timing observations made on more than seven hundred days spanning eleven years, we confirm this anomalous timing behavior. We explicitly demonstrate, for the first time, that a timing model consisting of the sum of two non-interacting Keplerian orbits can account for the observed signal. Both circular and elliptical orbits are allowed, although highly eccentric orbits require improbable orbital geometries. The motion of the pulsar in the inner orbit is very nearly a Keplerian ellipse, but the tidal effects of the outer companion cause variations in the orbital elements. We have measured the change in the projected semi-major axis of the orbit, which is dominated by precession-driven changes in the orbital inclination. This measurement, along with limits on the rate of change of other orbital elements, can be used to significantly restrict the properties of the outer orbit. We find that the second companion most likely has a mass m~0.01 Msun --- it is almost certainly below the hydrogen burning limit (m<0.036 Msun, 95% confidence) --- and has a current distance from the binary of ~35 AU and orbital period of order one hundred years. Circular (and near-circular) orbits are allowed only if the pulsar magnetic field is ~3x10^9 G, an order of magnitude higher than a typical millisecond pulsar field strength. In this case, the companion has mass m~1.2x10^-3 Msun and orbital period ~62 years.Comment: 12 pages, 6 figures, 3 tables. Very minor clarifications and rewording. Accepted for publication in the Astrophys.

Optical and Near-Infrared Imaging of the IRAS 1-Jy Sample of Ultraluminous Infrared Galaxies: II. The Analysis

The present paper discusses the results from an analysis of the images presented in Paper I (astro-ph/0207373) supplemented with new spectroscopic data obtained at Keck. All but one object in the 1-Jy sample show signs of a strong tidal interaction/merger. Multiple mergers involving more than two galaxies are seen in no more than 5 of the 118 (< 5%) systems. None of the 1-Jy sources is in the first-approach stage of the interaction, and most (56%) of them harbor a single disturbed nucleus and are therefore in the later stages of a merger. Seyfert galaxies (especially those of type 1), warm ULIGs (f_{25}/f_{60} > 0.2) and the more luminous systems (> 10^{12.5} L_sun) all show a strong tendency to be advanced mergers with a single nucleus. An analysis of the surface brightness profiles of the host galaxies in single-nucleus sources reveals that about 73% of the R and K' surface brightness profiles are fit adequately by an elliptical-like R^{1/4}-law. These elliptical-like 1-Jy systems have luminosities, half-light radii, and R-band axial ratio distribution that are similar to those of normal (inactive) intermediate-luminosity ellipticals and follow with some scatter the same mu_e - r_e relation. These elliptical-like hosts are most common among merger remnants with Seyfert 1 nuclei (83%), Seyfert 2 optical characteristics (69%) or mid-infrared (ISO) AGN signatures (80%). In general, the results from the present study are consistent with the merger-driven evolutionary sequence ``cool ULIGs --> warm ULIGs --> quasars,'' although there are many exceptions. (abridged)Comment: Correction to D.-C. Kim's affiliations. 42 pages + 3 tables + 3 multi-page jpeg figures; see http://www.astro.umd.edu/~veilleux/pubs/paper2.tar.gz for original figure

Predictors of varying levels of risks posed by fixated individuals to British public figures

Concerning approaches and communications to the Royal Family and other British public figures are relatively numerous. This paper examines over 2000 such cases logged over a three-year period in the United Kingdom. Using police and health data, the paper conducts a series of bivariate and multivariate analyses to demonstrate the predictors of what types of risk are posed by an individual case (e.g., communicate only, approach, security breach). The results showed that (a) the rates of serious mental disorders are higher among this sample than the general population base rate, (b) approachers were significantly more likely than communicators to suffer from serious mental disorders, (c) approachers were significantly more likely than communicators to have a history of substance use and abuse problems, (d) approachers were significantly more likely than communicators to have a history of violent behavior against property and persons, and (e) the motivations of approachers and communicators significantly differ. The paper concludes with a consideration of the implications for threat assessment and management