Hanbury Brown and Twiss Correlations of Anderson Localized Waves

When light waves propagate through disordered photonic lattices, they can eventually become localized due to multiple scattering effects. Here we show experimentally that while the evolution and localization of the photon density distribution is similar in the two cases of diagonal and off-diagonal disorder, the density-density correlation carries a distinct signature of the type of disorder. We show that these differences reflect a symmetry in the spectrum and eigenmodes that exists in off-diagonally disordered lattices but is absent in lattices with diagonal disorder.Comment: 4 pages, 3 figures, comments welcom

Hydrodynamic Equations in Quantum Hall Systems at Large Currents

Hydrodynamic equations (HDEQs) are derived which describe spatio-temporal evolutions of the electron temperature and the chemical potential of two-dimensional systems in strong magnetic fields in states with large diagonal resistivity appearing at the breakdown of the quantum Hall effect. The derivation is based on microscopic electronic processes consisting of drift motions in a slowly-fluctuating potential and scattering processes due to electron-electron and electron-phonon interactions. In contrast with the usual HDEQs, one of the derived HDEQs has a term with an energy flux perpendicular to the electric field due to the drift motions in the magnetic field. As an illustration, the current distribution is calculated using the derived HDEQs.Comment: 10 pages, 2 Postscript figures, to be published in J. Phys. Soc. Jpn. 71 (2002) No.

Hydrodynamic Equation for the Breakdown of the Quantum Hall Effect in a Uniform Current

The hydrodynamic equation for the spatial and temporal evolution of the electron temperature T_e in the breakdown of the quantum Hall effect at even-integer filling factors in a uniform current density j is derived from the Boltzmann-type equation, which takes into account electron-electron and electron-phonon scatterings. The derived equation has a drift term, which is proportional to j and to the first spatial derivative of T_e. Applied to the spatial evolution of T_e in a sample with an abrupt change of the width along the current direction, the equation gives a distinct dependence on the current direction as well as a critical relaxation, in agreement with the recent experiments.Comment: 4 pages, 1 Postscript figure, corrected equations, to be published in J. Phys. Soc. Jpn. 70 (2001) No.

Multiple Scattering of Fractionally-Charged Quasiparticles

We employ shot noise measurements to characterize the effective charge of quasiparticles, at filling factor nu=1/3 of the fractional quantum Hall regime, as they scatter from an array of identical weak backscatterers. Upon scattering, quasiparticles are known to bunch, e.g., only three e/3 charges, or 'electrons' are found to traverse a rather opaque potential barrier. We find here that the effective charge scattered by an array of scatterers is determined by the scattering strength of an individual scatterer and not by the combined scattering strength of the array, which can be very small. Moreover, we also rule out intra-edge equilibration of e/3 quasiparticles over length scale of hundreds microns.Comment: 4 pages, 4 figure

Thermohydrodynamics in Quantum Hall Systems

A theory of thermohydrodynamics in two-dimensional electron systems in quantizing magnetic fields is developed including a nonlinear transport regime. Spatio-temporal variations of the electron temperature and the chemical potential in the local equilibrium are described by the equations of conservation with the number and thermal-energy flux densities. A model of these flux densities due to hopping and drift processes is introduced for a random potential varying slowly compared to both the magnetic length and the phase coherence length. The flux measured in the standard transport experiment is derived and is used to define a transport component of the flux density. The equations of conservation can be written in terms of the transport component only. As an illustration, the theory is applied to the Ettingshausen effect, in which a one-dimensional spatial variation of the electron temperature is produced perpendicular to the current.Comment: 10 pages, 1 figur

Separately contacted edge states: A new spectroscopic tool for the investigation of the quantum Hall effect

Using an innovative combination of a quasi-Corbino sample geometry and the cross-gate technique, we have developed a method that enables us to separately contact single edge channels in the quantum Hall regime and investigate equilibration among them. Performing 4-point resistance measurements, we directly obtain information on the energetic and geometric structure of the edge region and the equilibration-length for current transport across the Landau- as well as the spin-gap. Based on an almost free choice in the number of participating edge channels and their interaction-length a systematic investigation of the parameter-space becomes possible.Comment: 8 pages, 7 figure

The Subaru COSMOS 20: Subaru Optical Imaging of the HST COSMOS Field with 20 Filters

We present both the observations and the data reduction procedures of the Subaru COSMOS 20 project that is an optical imaging survey of the HST COSMOS field, carried out by using Suprime-Cam on the Subaru Telescope with the following 20 optical filters: 6 broad-band (B, g', V, r', i', and z'), 2 narrow-band (NB711 and NB816), and 12 intermediate-band filters (IA427, IA464, IA484, IA505, IA527, IA574, IA624, IA679, IA709, IA738, IA767, and IA827). A part of this project is described in Taniguchi et al. (2007) and Capak et al. (2007) for the six broad-band and one narrow-band (NB816) filter data. In this paper, we present details of the observations and data reduction for remaining 13 filters (the 12 IA filters and NB711). In particular, we describe the accuracy of both photometry and astrometry in all the filter bands. We also present optical properties of the Suprime-Cam IA filter system in Appendix.Comment: 15 pages, 8 figures, 7 tables; accepted for publication in PASJ on October 2, 201

Synapse-associated protein 102/dlgh3 couples the NMDA receptor to specific plasticity pathways and learning strategies

Understanding the mechanisms whereby information encoded within patterns of action potentials is deciphered by neurons is central to cognitive psychology. The multiprotein complexes formed by NMDA receptors linked to synaptic membrane-associated guanylate kinase (MAGUK) proteins including synapse-associated protein 102 (SAP102) and other associated proteins are instrumental in these processes. Although humans with mutations in SAP102 show mental retardation, the physiological and biochemical mechanisms involved are unknown. Using SAP102 knock-out mice, we found specific impairments in synaptic plasticity induced by selective frequencies of stimulation that also required extracellular signal-regulated kinase signaling. This was paralleled by inflexibility and impairment in spatial learning. Improvement in spatial learning performance occurred with extra training despite continued use of a suboptimal search strategy, and, in a separate nonspatial task, the mutants again deployed a different strategy. Double-mutant analysis of postsynaptic density-95 and SAP102 mutants indicate overlapping and specific functions of the two MAGUKs. These in vivo data support the model that specific MAGUK proteins couple the NMDA receptor to distinct downstream signaling pathways. This provides a mechanism for discriminating patterns of synaptic activity that lead to long-lasting changes in synaptic strength as well as distinct aspects of cognition in the mammalian nervous system

A Potential Galaxy Threshing System in the Cosmos Field

We report on the discovery of a new potential galaxy threshing system in the COSMOS 2 square degree field using the prime-focus camera, Suprime-Cam, on the 8.2 m Subaru Telescope. This system consists of a giant elliptical galaxy with $M_V \approx -21.6$ and a tidally disrupted satellite galaxy with $M_V \approx -17.7$ at a photometric redshift of $z \approx 0.08$. This redshift is consistent with the spectroscopic redshift of 0.079 for the giant elliptical galaxy obtained from the Sloan Digital Sky Survey (SDSS) archive. The luminosity masses of the two galaxies are $3.7 \times 10^{12} \cal{M}_{\odot}$ and $3.1 \times 10^{9} \cal{M}_{\odot}$, respectively. The distance between the two galaxies is greater than 100 kpc. The two tidal tails emanating from the satellite galaxy extend over 150 kpc. This system would be the second well-defined galaxy threshing system found so far.Comment: 17 pages, 7 figures, accepted for the COSMOS special issue of ApJ