Correlations in a BEC collision: First-principles quantum dynamics with 150 000 atoms

The quantum dynamics of colliding Bose-Einstein condensates with 150 000 atoms are simulated directly from the Hamiltonian using the stochastic positive-P method. Two-body correlations between the scattered atoms and their velocity distribution are found for experimentally accessible parameters. Hanbury Brown-Twiss or thermal-like correlations are seen for copropagating atoms, while number correlations for counterpropagating atoms are even stronger than thermal correlations at short times. The coherent phase grains grow in size as the collision progresses with the onset of growth coinciding with the beginning of stimulated scattering. The method is versatile and usable for a range of cold atom systems.Comment: 4 pages, 4 figures. v2: Rewording and style changes, minor except for rewrite of background on the positive-P representation. Original research unchange

Platelet Collapse Model of Pulsar Glitches

A platelet collapse model of starquakes is introduced. It displays self-organized criticality with a robust power-law behavior. The simulations indicate a near-constant exponent, whenever scaling is present.Comment: Figures available by sending request to Ivan Schmidt: [email protected]

Newtonian Limit of Conformal Gravity

We study the weak-field limit of the static spherically symmetric solution of the locally conformally invariant theory advocated in the recent past by Mannheim and Kazanas as an alternative to Einstein's General Relativity. In contrast with the previous works, we consider the physically relevant case where the scalar field that breaks conformal symmetry and generates fermion masses is nonzero. In the physical gauge, in which this scalar field is constant in space-time, the solution reproduces the weak-field limit of the Schwarzschild--(anti)DeSitter solution modified by an additional term that, depending on the sign of the Weyl term in the action, is either oscillatory or exponential as a function of the radial distance. Such behavior reflects the presence of, correspondingly, either a tachion or a massive ghost in the spectrum, which is a serious drawback of the theory under discussion.Comment: 9 pages, comments and references added; the version to be published in Phys. Rev.

A note on dissipation in helical turbulence

In helical turbulence a linear cascade of helicity accompanying the energy cascade has been suggested. Since energy and helicity have different dimensionality we suggest the existence of a characteristic inner scale, $\xi=k_H^{-1}$, for helicity dissipation in a regime of hydrodynamic fully developed turbulence and estimate it on dimensional grounds. This scale is always larger than the Kolmogorov scale, $\eta=k_E^{-1}$, and their ratio $\eta / \xi$ vanishes in the high Reynolds number limit, so the flow will always be helicity free in the small scales.Comment: 2 pages, submitted to Phys. Fluid

Local and global gravity

Our long experience with Newtonian potentials has inured us to the view that gravity only produces local effects. In this paper we challenge this quite deeply ingrained notion and explicitly identify some intrinsically global gravitational effects. In particular we show that the global cosmological Hubble flow can actually modify the motions of stars and gas within individual galaxies, and even do so in a way which can apparently eliminate the need for galactic dark matter. Also we show that a classical light wave acquires an observable, global, path dependent phase in traversing a gravitational field. Both of these effects serve to underscore the intrinsic difference between non-relativistic and relativistic gravity.Comment: LaTeX, 20 pages plus three figures in two postscript files. To appear in a special issue of Foundations of Physics honoring Professor Lawrence Horwitz on the occasion of his 65th birthday; A. van der Merwe and S. Raby, Editors, Plenum Publishing Company, N.Y., 199

Bose-Einstein condensation of trapped atoms with dipole interactions

The path integral Monte Carlo method is used to simulate dilute trapped Bose gases and to investigate the equilibrium properties at finite temperatures. The quantum particles have a long-range dipole-dipole interaction and a short-range s-wave interaction. Using an anisotropic pseudopotential for the long-range dipolar interaction and a hard-sphere potential for the short-range s-wave interaction, we calculate the energetics and structural properties as a function of temperature and the number of particles. Also, in order to determine the effects of dipole-dipole forces and the influence of the trapping field on the dipolar condensate, we use two cylindrically symmetric harmonic confinements (a cigar-shaped trap and a disk-shaped trap). We find that the net effect of dipole-dipole interactions is governed by the trapping geometry. For a cigar-shaped trap, the net contribution of dipolar interactions is attractive and the shrinking of the density profiles is observed. For a disk-shaped trap, the net effect of long-range dipolar forces is repulsive and the density profiles expand

Diagonal quantum Bianchi type IX models in N=1 supergravity

We take the general quantum constraints of N=1 supergravity in the special case of a Bianchi metric, with gravitino fields constant in the invariant basis. We construct the most general possible wave function which solves the Lorentz constraints and study the supersymmetry constraints in the Bianchi Class A Models. For the Bianchi-IX cases, both the Hartle-Hawking state and wormhole state are found to exist in the middle fermion levels.Comment: plain LaTex, 17 pages, accepted for publication in Classical Quantum Gravit

Implications of Cosmic Repulsion for Gravitational Theory

In this paper we present a general, model independent analysis of a recently detected apparent cosmic repulsion, and discuss its potential implications for gravitational theory. In particular, we show that a negatively spatially curved universe acts like a diverging refractive medium, to thus naturally cause galaxies to accelerate away from each other. Additionally, we show that it is possible for a cosmic acceleration to only be temporary, with some accelerating universes actually being able to subsequently recontract.Comment: RevTeX, 13 page

Characteristic and Correlation Between TIME and Complication After Destructive Eye Procedure Patient at Plastic and Reconstruction Division Sanglah Hospital\u27s Eye Clinic Bali-Indonesia

Destructive eye procedure can be carried out by enucleation, evisceration and excenteration. Some efforts have been developed to reduce the complications, but it still occur within several years after the operation. This research aims to find out the characteristic and correlation between time and complications in patient after destructive eye procedure at Plastic and Reconstruction Division Sanglah Hospital\u27s Eye Clinic. For addition, characteristic of other patients in plastic and reconstruction also provided. This report is an analytical cross sectional study. Data were collected retrospectively from medical report of patients with history of destructive eye procedure in Sanglah Hospital\u27s eye clinic from January 1st until December 31st 2010. Patient\u27s characteristics were presented as frequency, percentage, mean, and standard deviation. Correlations between variables were statistically analyzed with Correlation of Lambda. Eye trauma, anophthalmic socket and nasolacrimal duct obstruction were the most common diagnosis at plastic and reconstruction division Sanglah Hospital\u27s eye clinic. There were 17 patients with history of destructive eye procedure in this report, including 76.5% male and 23.5% female. There is 58.8% destructive eye procedure held in age 13-50 year, mean 30.75 (SD 19.81). Infection (35.3%), trauma (23.5%) and tumor (11.8%) were the most common cause of destructive eye procedure in this study. Complications of destructive eye procedure occur in 70.6% of patient with contracted socket was the most common complication (58.3%). There was medium correlation between time and complication after the procedure, but the correlation was not statistically significant (r = 0.40; p > 0.05). In conclusion, from this study we obtained that there was medium correlation between time and complication after the procedure, but the correlation was not statistically significant

Grover's search algorithm: An optical approach

The essential operations of a quantum computer can be accomplished using solely optical elements, with different polarization or spatial modes representing the individual qubits. We present a simple all-optical implementation of Grover's algorithm for efficient searching, in which a database of four elements is searched with a single query. By `compiling' the actual setup, we have reduced the required number of optical elements from 24 to only 12. We discuss the extension to larger databases, and the limitations of these techniques.Comment: 6 pages, 5 figures. To appear in a special issue of the Journal of Modern Optics -- "The Physics of Quantum Information