UScholar Works
 
Filters: Department: "Physics" Collection: "ir_uspace"
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CreatorTitleDescriptionSubjectDate
1 Gondolo, PaoloDark matter and relic particlesFor the first time, we have a believable inventory of the contents of the universe. First, we have compelling evidence that the universe is flat (or at least very nearly so), consistent with the prediction of inflation. Measurements of the first acoustic peak in the angular power spectrum of the Cos...Relic particles; MACHOs; WIMP; Weakly interacting massive particles2001
2 Ailion, David CharlesDetection of slow modulation wave diffusion in incommensurate barium sodium niobate by 93Nb 2D exchange NMR93Nb two-dimensional (2D) exchange NMR was used to study ultraslow motions in incommensurate barium sodium niobate (BSN) in the temperature range 500 - 560 K. These 2D exchange data provide strong evidence for diffusionlike motion of the modulation wave in BSN. Such motions in BSN had been previousl...NMR; Hahn spin-echo decay; Incommensurate systems.2001
3 Gondolo, PaoloGamma-ray summary reportThis paper reviews the field of gamma-ray astronomy and describes future experiments and prospects for advances in fundamental physics and high-energy astrophysics through gamma-ray measurements. We concentrate on recent progress in the understanding of active galaxies, and the use of these sources ...EGRET; GLAST; VERITAS2001
4 Williams, Clayton C.Single electron tunneling detected by electrostatic forceSingle electron tunneling events between a specially fabricated scanning probe and a conducting surface are demonstrated. The probe is an oxidized silicon atomic force microscope tip with an electrically isolated metallic dot at its apex. A voltage applied to the silicon tip produces an electrostat...Single electron; Tunneling events; Scanning tunneling microscope; Electrostatic modeling2001
5 Lupton, John MarkTime delayed electroluminescence overshoot in single layer polymer light-emitting diodes due to electrode luminescence quenchingWe investigate the transient response of single layer polymer light-emitting diodes (LEDs) based on poly[2-methoxy, 5-(2'ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV). An electroluminescence overshoot is observed between 1 and 2 μs after turning off the voltage pulse, depending on temperature...MEH-PPV; Delayed electroluminescence; Overshoot; Single layer; Electrode luminescence quenching; Transient responses2001
6 Boehme, ChristophTime domain measurement of spin-dependent recombinationA defect characterization method is presented, the time domain measurement of spin-dependent recombination (TSR). Recombination between paramagnetic states is changed rapidly by electron spin resonant excitation through strong nanosecond microwave pulses. After the pulse, a slow relaxation of the re...Spin-dependent recombination2001
7 Vardeny, Zeev Valentine; Raikh, Mikhail E.Anomalous coherent backscattering of light from opal photonic crystalsWe studied coherent backscattering (CBS) of light from opal photonic crystals with incomplete band gaps. We observed a dramatic broadening of the CBS cone for incident angles close to the Bragg condition in the crystals. We modify the conventional CBS theory to incorporate Bragg attenuation resultin...Coherent backscattering; Bragg condition2001-05
8 Wu, Yong-ShiCharacterization of one-dimensional Luttinger liquids in terms of fractional exclusion statisticsWe develop a bosonization approach to study the low temperature properties of one-dimensional gas of particles obeying fractional exclusion statistics (FES). It is shown that such ideal gas reproduces the low-energy excitations and asymptotic exponents of a one-component Luttinger liquid (with no in...2001-06
9 Vardeny, Zeev ValentineCoherent umklapp scattering of light from disordered photonic crystalsA theoretical study of the coherent light scattering from disordered photonic crystals is presented. In addition to the conventional enhancement of the reflected light intensity into the backscattering direction, the so-called coherent backscattering (CBS), the periodic modulation of the dielectri...Coherent umklapp scattering; Disordered photonic crystals; Coherent backscattering; Bragg2001-05
10 Lupton, John MarkControl of mobility in molecular organic semiconductors by dendrimer generationConjugated dendrimers are of interest as novel materials for light-emitting diodes. They consist of a luminescent chromophore at the core with highly branched conjugated dendron sidegroups. In these materials, light emission occurs from the core and is independent of generation. The dendron branchin...Dendrimer generation; Dendron branching; Charge transport; Mobility2001-03
11 Vardeny, Zeev ValentineExcitation dynamics in single molecular crystals of α-hexathiophene from femtosecond to millisecondWe identify odd- and even-parity states and measure transient photomodulation spectra of Frenkel excitons in a-hexathiophene single crystals. The lowest Frenkel excitons are characterized by a stimulated emission band at ~2 eV and an absorption band at 1.3 eV. Intramolecular internal conversion go...Excitation dynamics; alpha-hexathiophene; Frenkel excitons; pi-conjugated polymers; Photoexcitation2001-04
12 Vardeny, Zeev Valentine; Raikh, Mikhail E.Excitations in photonic crystals infiltrated with polarizable mediaLight propagation in a photonic crystal with incomplete band gap, infiltrated with polarizable molecules is considered. We demonstrate that the interplay between the spatial dispersion caused by Bragg diffraction and polaritonic frequency dispersion gives rise to alternative propagating excitation...Polarizable media; Light propagation; Bragg diffraction; Excitations2001-06
13 DeTar, Carletonf B for various actions: approaching the continuum limit with dynamical fermionsWe present results for pseudoscalar decay constants of heavy-light mesons using both quenched and Nf = 2 dynamical fermion configurations. A variety of fermion actions is investigated: Wilson, nonperturbative clover, and fat-link clover. For heavy quarks the Fermilab formalism is applied. In the q...Decay constants; Wilson fermions2001-03
14 Mishchenko, EugeneFrequency dependence of the photonic noise spectrum in an absorbing or amplifying diffusive mediumA theory is presented for the frequency dependence of the power spectrum of photon current fluctuations originating from a disordered medium. Both the cases of an absorbing medium ("grey body") and of an amplifying medium ("random laser") are considered in a waveguide geometry. The semiclassical ap...Random laser; Noise power spectrum; Frequency dependence; Waveguide geometry2001-01
15 Mishchenko, EugeneFull counting statistics of a charge pump in the Coulomb blockade regimeWe study full charge counting statistics (FCCS) of a charge pump based on a nearly open single electron transistor. The problem is mapped onto an exactly soluble problem of a nonequilibrium g=1/2 Luttinger liquid with an impurity. We obtain an analytic expression for the generating function of the...Counting statistics; Luttinger liquid2001-11
16 Gondolo, PaoloImplications of muon anomalous magnetic moment for supersymmetric dark matterThe anomalous magnetic moment of the muon has recently been measured to be in conflict with the standard model prediction with an excess of 2.6s. Taking the excess at face value as a measurement of the supersymmetric contribution, we find that at 95% confidence level it imposes an upper bound of 50...Magnetic moment; Neutralinos2001-05
17 DeTar, CarletonLattice results for the decay constant of heavy-light vector mesonsWe compute the leptonic decay constants of heavy-light vector mesons in the quenched approximation. The reliability of lattice computations for heavy quarks is checked by comparing the ratio of vector to pseudoscalar decay constant with the prediction of heavy quark effective theory in the limit o...Heavy quark effective theory; Wilson quarks2001-12
18 Gondolo, PaoloMeasurement of the gluon parton distribution function at small x with neutrino telescopesWe analyze the possibility that neutrino telescopes may provide an experimental determination of the slope λ of the gluon distribution in the proton at momentum fractions x smaller than the accelerator reach. The method is based on a linear relation between λ and the spectral index (slope) of th...Neutrino telescopes; Charm2001-01
19 Wu, Yong-ShiNanoscale magnetic-domain structure in colossal magnetoresistance islandsMagnetic force microscopy reveals the nature of local magnetic structure in submicron islands of colossal magnetoresistance (CMR) thin films. The evolution of domains in a magnetic field reveals the importance of shape anisotropy as well as magnetostriction in determining the micromagnetics in suc...Magnetic domain; Colossal magnetoresistance islands2001-11
20 Gondolo, PaoloOn the direct detection of extragalactic weakly interacting massive particlesWe consider the direct detection of weakly interacting massive particles (WIMPs) reaching the Earth from outside the Milky Way. If these WIMPs form a distinct population they will, although of much lower flux than typical galactic halo WIMPs, have a number of features which might aid in their ulti...Extragalactic WIMPs; Weakly interacting massive particles2001-10
21 Wu, Yong-ShiOne-loop shift in noncommutative Chern-Simons couplingIn this paper we study the one-loop shift in the coupling constant in a noncommutative pure U(N) Chern-Simons gauge theory in three dimensions. The one-loop shift is shown to be a constant proportional to N, independent of noncommutativity parameters, and non-vanishing for U(1) theory. Possible phy...2001-01
22 Gerton, JordanPhotoassociative frequency shift in a quantum degenerate gasA light-induced frequency shift is observed in single-photon photoassociative spectra of magnetically trapped, quantum degenerate 7Li. The shift is a manifestation of the coupling between the threshold continuum scattering states and discrete bound levels in the excited-state molecular potential in...2001-10
23 Vardeny, Zeev ValentinePhotoexcitation dynamics in regioregular and regiorandom polythiophene filmsUsing a variety of optical probes techniques we studied the photoexcitation dynamics in thin films of poly-3-hexyl thiophene with regioregular order that forms lamellae structures with increased interchain interaction, as well as regiorandom order that keeps a chainlike morphology. In regiorandom fi...Photoexcitation dynamics; Regio-regular; Regio-random; Polythiophene films2001-11
24 DeTar, CarletonQCD spectrum with three quark flavorsWe present results from a lattice hadron spectrum calculation using three flavors of dynamical quarks - two light and one strange-and quenched simulations for comparison. These simulations were done using a one-loop Symanzik improved gauge action and an improved Kogut-Susskind quark action. The lat...Dynamical quarks2001-08
25 Wu, Yong-ShiRemarks on noncommutative open string theory: V duality and holographyIn this paper we study the interplay of electric and magnetic backgrounds in determining the decoupling limit of coincident D branes towards a noncommutative Yang-Mills (NCYM) or open string (NCOS) theory. No decoupling limit has been found for the NCYM model with space-time noncommutativity. It i...Hubbard operator; Bosonization; Deformation; t-J model2001-03
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