Time correlations in 1D quantum impurity problems

We develop in this letter an analytical approach using form- factors to compute time dependent correlations in integrable quantum impurity problems. As an example, we obtain for the first time the frequency dependent conductivity $G(\omega)$ for the tunneling between the edges in the $\nu=1/3$ fractional quantum Hall effect, and the spectrum $S(w)$ of the spin-spin correlation in the anisotropic Kondo model and equivalently in the double well system of dissipative quantum mechanics, both at vanishing temperature.Comment: 4 pages, Revtex and 2 figure

Geometrical Expression for the Angular Resolution of a Network of Gravitational-Wave Detectors

We report for the first time general geometrical expressions for the angular resolution of an arbitrary network of interferometric gravitational-wave (GW) detectors when the arrival-time of a GW is unknown. We show explicitly elements that decide the angular resolution of a GW detector network. In particular, we show the dependence of the angular resolution on areas formed by projections of pairs of detectors and how they are weighted by sensitivities of individual detectors. Numerical simulations are used to demonstrate the capabilities of the current GW detector network. We confirm that the angular resolution is poor along the plane formed by current LIGO-Virgo detectors. A factor of a few to more than ten fold improvement of the angular resolution can be achieved if the proposed new GW detectors LCGT or AIGO are added to the network. We also discuss the implications of our results for the design of a GW detector network, optimal localization methods for a given network, and electromagnetic follow-up observations.Comment: 13 pages, for Phys. Rev.

Quasi-adiabatic Continuation of Quantum States: The Stability of Topological Ground State Degeneracy and Emergent Gauge Invariance

We define for quantum many-body systems a quasi-adiabatic continuation of quantum states. The continuation is valid when the Hamiltonian has a gap, or else has a sufficiently small low-energy density of states, and thus is away from a quantum phase transition. This continuation takes local operators into local operators, while approximately preserving the ground state expectation values. We apply this continuation to the problem of gauge theories coupled to matter, and propose a new distinction, perimeter law versus "zero law" to identify confinement. We also apply the continuation to local bosonic models with emergent gauge theories. We show that local gauge invariance is topological and cannot be broken by any local perturbations in the bosonic models in either continuous or discrete gauge groups. We show that the ground state degeneracy in emergent discrete gauge theories is a robust property of the bosonic model, and we argue that the robustness of local gauge invariance in the continuous case protects the gapless gauge boson.Comment: 15 pages, 6 figure

EXAMINING FOOD CONSUMPTION IN JAPAN UNDER LIFE-CYCLE HYPOTHESIS: IMPLICATION FROM CROSS-SECTIONAL DATA

This study estimates a cross-sectional model through a theoretically consistent Almost Ideal Demand System (AIDS) to examine the economic and demographic determinants of food consumption patterns in Japan over life-cycle periods. Results show key factors that explain such behavior, including family size, number of children, lifestyle and health concern.Research Methods/ Statistical Methods,

Coherence measurements on Rydberg wave packets kicked by a half-cycle pulse

A kick from a unipolar half-cycle pulse (HCP) can redistribute population and shift the relative phase between states in a radial Rydberg wave packet. We have measured the quantum coherence properties following the kick, and show that selected coherences can be destroyed by applying an HCP at specific times. Quantum mechanical simulations show that this is due to redistribution of the angular momentum in the presence of noise. These results have implications for the storage and retrieval of quantum information in the wave packet.Comment: 4 pages, 4 figures (5 figure files

Resonating singlet valence plaquettes

We consider the simplest generalizations of the valence bond physics of SU(2) singlets to SU(N) singlets that comprise objects with N sites -- these are SU(N) singlet plaquettes with N=3 and N=4 in three spatial dimensions. Specifically, we search for a quantum mechanical liquid of such objects -- a resonating singlet valence plaquette phase that generalizes the celebrated resonating valence bond phase for SU(2) spins. We extend the Rokhsar-Kivelson construction of the quantum dimer model to the simplest SU(4) model for valence plaquette dynamics on a cubic lattice. The phase diagram of the resulting quantum plaquette model is analyzed both analytically and numerically. We find that the ground state is solid everywhere, including at the Rokhsar-Kivelson point where the ground state is an equal amplitude sum. By contrast, the equal amplitude sum of SU(3) singlet triangular plaquettes on the face centered cubic lattice is liquid and thus a candidate for describing a resonating single valence plaquette phase, given a suitably defined local Hamiltonian.Comment: 12 pages, 15 figures, minor changes, references added, Phys Rev B versio

The Grassmannian Sigma Model in SU(2) Yang-Mills Theory

Spin-charge separation in pure SU(2) Yang-Mills theory was recently found to involve the dynamics of an O(3) non-linear sigma model and, seemingly, a Grassmannian non-linear sigma model. In this article we explicitly construct the Grassmannian sigma model of the form appearing in the the spin-charge separated SU(2) theory through a quaternionic decomposition of the manifold, thus verifying its relevance in this context. The coupling between this model and the O(3) non-linear sigma model is further commented upon.Comment: 11 pages, undergraduate research project; version published in J. Phys.

Food Consumption and Demographics in Japan: Implications for an Aging Population

This study estimates a cross-sectional model based on the Almost Ideal Demand System (AIDS) to examine the determinants of food consumption patterns in Japan over life-cycle periods. The test of structural changes, the analysis of the effects of demographic characteristics, and the estimation of expenditure and price elasticities are conducted from a random sample of 1,281 households from a Japanese household survey in 1997. Results show that each economic or non-economic factor has a different impact on food consumption over a lifetime. Changes in consumption of some food groups can be explained by price and income effects where others can be explained by demographic characteristics. Financial constraint is not binding and residential location is likely to have little or no impact on predicting consumers’ food choices at different periods of their lives. Other key factors that affect consumption pattern include family size, number of children, lifestyle and health concern.Japan, Food Demand, Life-Cycle, AIDS, Household

Exotic order in simple models of bosonic systems

We show that simple Bose Hubbard models with unfrustrated hopping and short range two-body repulsive interactions can support stable fractionalized phases in two and higher dimensions, and in zero magnetic field. The simplicity of the constructed models advances the possibility of a controlled experimental realization and novel applications of such unconventional states.Comment: 4 pages, 4 figure

Molecular dynamics simulations of the dipolar-induced formation of magnetic nanochains and nanorings

Iron, cobalt and nickel nanoparticles, grown in the gas phase, are known to arrange in chains and bracelet-like rings due to the long-range dipolar interaction between the ferromagnetic (or super-paramagnetic) particles. We investigate the dynamics and thermodynamics of such magnetic dipolar nanoparticles for low densities using molecular dynamics simulations and analyze the influence of temperature and external magnetic fields on two- and three-dimensional systems. The obtained phase diagrams can be understood by using simple energetic arguments.Comment: 6 pages, 6 figure