Self-Binding Transition in Bose Condensates with Laser-Induced ``Gravitation''

In our recent publication (D. O'Dell, et al, Phys. Rev. Lett. 84, 5687 (2000)) we proposed a scheme for electromagnetically generating a self-bound Bose-Einstein condensate with 1/r attractive interactions: the analog of a Bose star. Here we focus upon the conditions neccessary to observe the transition from external trapping to self-binding. This transition becomes manifest in a sharp reduction of the condensate radius and its dependence on the laser intensity rather that the trap potential.Comment: 5 pages, 2 figures: slightly enhanced text: more explanatio

Atomic Bloch-Zener oscillations for sensitive force measurements in a cavity

Cold atoms in an optical lattice execute Bloch-Zener oscillations when they are accelerated. We have performed a theoretical investigation into the case when the optical lattice is the intra-cavity field of a driven Fabry-Perot resonator. When the atoms oscillate inside the resonator, we find that their back-action modulates the phase and intensity of the light transmitted through the cavity. We solve the coupled atom-light equations self-consistently and show that, remarkably, the Bloch period is unaffected by this back-action. The transmitted light provides a way to observe the oscillation continuously, allowing high precision measurements to be made with a small cloud of atoms.Comment: 5 pages, 2 figures. Updated version including cavity heating effect

Oscillations of rotating trapped Bose-Einstein condensates

The tensor-virial method is applied for a study of oscillation modes of uniformly rotating Bose-Einstein condensed gases, whose rigid body rotation is supported by an vortex array. The second order virial equations are derived in the hydrodynamic regime for an arbitrary external harmonic trapping potential assuming that the condensate is a superfluid at zero temperature. The axisymmetric equilibrium shape of the condensate is determined as a function of the deformation of the trap; its domain of stability is bounded by the constraint $\Omega<1$ on the rotation rate (measured in units of the trap frequency $\omega_0$.) The oscillations of the axisymmetric condensate are stable with respect to the transverse-shear, toroidal and quasi-radial modes of oscillations, corresponding to the $l= 2$, $| m| = 0,1,2$ surface deformations. In non-axisymmetric traps, the equilibrium constrains the (dimensionless) deformation in the plane orthogonal to the rotation to the domain $A_2 > \Omega^2$ with $\Omega< 1$. The second harmonic oscillation modes in non-axisymmetric traps separate into two classes which have even or odd parity with respect to the direction of the rotation axis. Numerical solutions show that these modes are stable in the parameter domain where equilibrium figures exist.Comment: 16 pages, including 4 figures, uses Revtex; v2 includes a treatment of modes in unisotropic traps; PRA in pres

Extended axion electrodynamics: Optical activity induced by nonstationary dark matter

We establish a new self-consistent Einstein-Maxwell-axion model based on the Lagrangian, which is linear in the pseudoscalar (axion) field and its four-gradient and includes the four-vector of macroscopic velocity of the axion system as a whole. We consider extended equations of the axion electrodynamics, modified gravity field equations, and discuss nonstationary effects in the phenomenon of optical activity induced by axions.Comment: 6 pages, 0 figures, accepted for publication in the Journal Gravitation and Cosmology, reported at the 14th Russian Gravitational Conference (Ulyanovsk, 2011

Quantum Vacuum Contribution to the Momentum of the Dielectric Media

Momentum transfer between matter and electromagnetic field is analyzed. The related equations of motion and conservation laws are derived using relativistic formalism. Their correspondence to various, at first sight self-contradicting, experimental data (the so called Abraham-Minkowski controversy) is demonstrated. A new, Casimir like, quantum phenomenon is predicted: contribution of vacuum fluctuations to the motion of dielectric liquids in crossed electric and magnetic fields. Velocities about $50nm/s$ can be expected due to the contribution of high frequency vacuum modes

Rotons in gaseous Bose-Einstein condensates irradiated by a laser

A gaseous Bose-Einstein condensate (BEC) irradiated by a far off-resonance laser has long-range interatomic correlations caused by laser-induced dipole-dipole interactions. These correlations, which are tunable via the laser intensity and frequency, can produce a `roton' minimum in the excitation spectrum--behavior reminiscent of the strongly correlated superfluid liquid helium II.Comment: 6 pages, includes 3 figure

Fine Scale Temperature Fluctuations in the the Orion Nebula and the t^2 Problem

We present a high spatial resolution map of the columnar electron temperature (Tc) of a region to the south west of the Trapezium in the Orion Nebula. This map was derived from Hubble Space Telescope images that isolated the primary lines of HI for determination of the local extinction and of the OIII lines for determination of Tc. Although there is no statistically significant variation of Tc with distance from the dominant ionizing star theta1-Ori-C, we find small scale variations in the plane of the sky down to a few arcseconds that are compatible with the variations inferred from comparing the value of Te derived from forbidden and recombination lines, commonly known as the t^2 problem. We present other evidence for fine scale variations in conditions in the nebula, these being variations in the surface brightness of the the nebula, fluctuations in radial velocities, and ionization changes. From our Tc map and other considerations we estimate that t^2=0.028 +-0.006 for the Orion nebula. Shadowed regions behind clumps close to the ionization front can make a significant contribution to the observed temperature fluctuations, but they cannot account for the t^2 values inferred from several methods of temperature determination. It is shown that an anomalous broadening of nebular emission lines appears to have the same sense of correlation as the temperature anomalies, although a causal link is not obvious.Comment: 53 pages, 13 images, many of the images have been downgraded to be able to fit within the astro-ph file size limit

Ten-Micron Observations of Nearby Young Stars

(abridged) We present new 10-micron photometry of 21 nearby young stars obtained at the Palomar 5-meter and at the Keck I 10-meter telescopes as part of a program to search for dust in the habitable zone of young stars. Thirteen of the stars are in the F-K spectral type range ("solar analogs"), 4 have B or A spectral types, and 4 have spectral type M. We confirm existing IRAS 12-micron and ground-based 10-micron photometry for 10 of the stars, and present new insight into this spectral regime for the rest. Excess emission at 10 micron is not found in any of the young solar analogs, except for a possible 2.4-sigma detection in the G5V star HD 88638. The G2V star HD 107146, which does not display a 10-micron excess, is identified as a new Vega-like candidate, based on our 10-micron photospheric detection, combined with previously unidentified 60-micron and 100-micron IRAS excesses. Among the early-type stars, a 10-micron excess is detected only in HD 109573A (HR 4796A), confirming prior observations; among the M dwarfs, excesses are confirmed in AA Tau, CD -40 8434, and Hen 3-600A. A previously suggested N band excess in the M3 dwarf CD -33 7795 is shown to be consistent with photospheric emission.Comment: 40 pages, 4 figures, 5 tables. To appear in the January 1, 2004 issue of Ap

Bivariate genetic modelling of the response to an oral glucose tolerance challenge: A gene x environment interaction approach

AIMS/HYPOTHESIS: Twin and family studies have shown the importance of genetic factors influencing fasting and 2 h glucose and insulin levels. However, the genetics of the physiological response to a glucose load has not been thoroughly investigated. METHODS: We studied 580 monozygotic and 1,937 dizygotic British female twins from the Twins UK Registry. The effects of genetic and environmental factors on fasting and 2 h glucose and insulin levels were estimated using univariate genetic modelling. Bivariate model fitting was used to investigate the glucose and insulin responses to a glucose load, i.e. an OGTT. RESULTS: The genetic effect on fasting and 2 h glucose and insulin levels ranged between 40% and 56% after adjustment for age and BMI. Exposure to a glucose load resulted in the emergence of novel genetic effects on 2 h glucose independent of the fasting level, accounting for about 55% of its heritability. For 2 h insulin, the effect of the same genes that already influenced fasting insulin was amplified by about 30%. CONCLUSIONS/INTERPRETATION: Exposure to a glucose challenge uncovers new genetic variance for glucose and amplifies the effects of genes that already influence the fasting insulin level. Finding the genes acting on 2 h glucose independently of fasting glucose may offer new aetiological insight into the risk of cardiovascular events and death from all causes

The influence of transition metal solutes on dislocation core structure and values of Peierls stress and barrier in tungsten

Several transition metals were examined to evaluate their potential for improving the ductility of tungsten. The dislocation core structure and Peierls stress and barrier of $1/2$ screw dislocations in binary tungsten-transition metal alloys (W$_{1-x}$TM$_{x}$) were investigated using first principles electronic structure calculations. The periodic quadrupole approach was applied to model the structure of $1/2$ dislocation. Alloying with transition metals was modeled using the virtual crystal approximation and the applicability of this approach was assessed by calculating the equilibrium lattice parameter and elastic constants of the tungsten alloys. Reasonable agreement was obtained with experimental data and with results obtained from the conventional supercell approach. Increasing the concentration of a transition metal from the VIIIA group, i.e. the elements in columns headed by Fe, Co and Ni, leads to reduction of the $C^\prime$ elastic constant and increase of elastic anisotropy A=$C_{44}/C^\prime$. Alloying W with a group VIIIA transition metal changes the structure of the dislocation core from symmetric to asymmetric, similar to results obtained for W$_{1-x}$Re$_{x}$ alloys in the earlier work of Romaner {\it et al} (Phys. Rev. Lett. 104, 195503 (2010))\comments{\cite{WRECORE}}. In addition to a change in the core symmetry, the values of the Peierls stress and barrier are reduced. The latter effect could lead to increased ductility in a tungsten-based alloy\comments{\cite{WRECORE}}. Our results demonstrate that alloying with any of the transition metals from the VIIIA group should have similar effect as alloying with Re.Comment: 12 pages, 8 figures, 3 table