121348798
Scaling theory of the Hall coefficient near the metal-insulator transition, a renormalization-group approach
Abstract We investigate the critical properties of the Hall conduxtivity in weak magetic fields near the disorder driven metal-insulator transition. We derive an effective lagrangian governing the interactions of the diffusive modes in the presence of time-reversal and particle-hole symmetry breaking and identify a new operator relevant to the scaling behavior of the weak-field Hall conductivity. A Wilson-Polyakov renormalization-group analysis is carried out and the flow equations are obtained near two dimensions. We show that the perturbative behavior of the Hall conductivity in the weakly localized regime, in two dimensions, is not simply related to the critical behavior of the Hall conductivity, due to the role played by a new scaling variable. Solving the renormalization-group equations close to the zero-field fixed point, our theory predicts that the Hall number vanishes at the mobility edge with an exponent g = 1 in agreement with several experimental observations. We clarify the connection between the field-theoretic approach and the conventional perturbative approach and elucidate why perturbation in the disorder, which is valid in the weak localization regime fails to predict the correct critical behavior.
119266949
MULTIBAND STUDIES OF THE OPTICAL PERIODIC MODULATION IN THE X-RAY BINARY SAX J1808.4–3658 DURING ITS QUIESCENCE AND 2008 OUTBURST
We report on time-resolved optical imaging of the X-ray binary SAX J1808.4-3658 during its quiescent state and 2008 outburst. The binary, containing an accretion-powered millisecond pulsar, has a large sinusoidal-like modulation in its quiescent optical emission. We employ a Markov chain Monte Carlo technique to fit our multi-band light curve data in quiescence with an irradiated star model, and derive a tight constraint of 50(-5)(+6) deg on the inclination angle i of the binary system. The pulsar and its companion are constrained to have masses of 0.97(-0.22)(+0.31) M-circle dot and 0.04(-0.01)(+0.02) M-circle dot (both 1 sigma ranges), respectively. The dependence of these results on the measurements of the companion's projected radial velocity is discussed. We also find that the accretion disk had nearly constant optical fluxes over a similar to 500 day period in the quiescent state our data covered, but started brightening 1.5 months before the 2008 outburst. Variations in modulation during the outburst were detected in our four observations made 7-12 days after the start of the outburst, and a sinusoidal-like modulation with 0.2 mag amplitude changed to have a smaller amplitude of 0.1 mag. The modulation variations are discussed. We estimate the albedo of the companion during its quiescence and the outburst, which was approximately 0 and 0.8 (for isotropic emission), respectively. This large difference probably provides additional evidence that the neutron star in the binary turns on as a radio pulsar in quiescence.
119232297
Subaru Constraint on Circular Polarization in I-Band Emission from the Magnetar 4U 0142+61
We present the first imaging circular polarimetry of the anomalous X-ray pulsar (AXP) 4U 0142+61 at optical wavelengths. The AXP is the only magnetar that has been well studied at optical and infrared wavelengths, and is known to have a complicated broad-band spectrum over the wavelength range. The optical polarimetric observation was carried out with the 8.2-m Subaru telescope at the I-band. From the observation, the degree of circular polarization, V, was measured to be V = 1.1 +/- 2.0%, or vertical bar V vertical bar <= 4.3% (90% confidence). The relatively large uncertainty was due to the faintness of the source (I = 23.4-24.0). Considering the currently suggested models for optical emission from magnetars, our result is not sufficiently conclusive to discriminate the models. We suggest that because linear polarization is expected to be strong in the models, linear polarimetry of this magnetar should be conducted.
119397253
Evidence for superdeformation in Dy-149,Dy-150: Onset of the collapse of the Z=66 deformed shell closure?
An experiment has been performed to search for superdeformed (SD) states in Dy-149,Dy-150. While no evidence for discrete superdeformed states has been observed, a superdeformed ridge with a separation of Delta E-gamma=52 keV with a total intensity of 1.8+/-0.5% that of Dy-150 has been observed. An upper limit of 0.8% (0.9%), of the intensity of Dy-150 (Dy-149), is placed for observation of the most intense discrete line states. The relative weakness in the SD population is suggested to be due to a rapid decrease in the depth of the superdeformed minimum, as one moves away from doubly magic Dy-152.
14918025
Water abundance in molecular cloud cores
We present Submillimeter Wave Astronomy Satellite (SWAS) observations of the 110 → 101 transition of ortho-H2O at 557 GHz toward 12 molecular cloud cores. The water emission was detected in NGC 7538, ρ Oph A, NGC 2024, CRL 2591, W3, W3OH, Mon R2, and W33 and was not detected in TMC-1, L134N, and B335. We also present a small map of the H2O emission in S140. Observations of the H218O line were obtained toward S140 and NGC 7538, but no emission was detected. The abundance of ortho-H2O relative to H2 in the giant molecular cloud cores was found to vary between 6 × 10-10 and 1 × 10-8. Five of the cloud cores in our sample have previous H2O detections; however, in all cases the emission is thought to arise from hot cores with small angular extents. The H2O abundance estimated for the hot core gas is at least 100 times larger than in the gas probed by SWAS. The most stringent upper limit on the ortho-H2O abundance in dark clouds is provided in TMC-1, where the 3 σ upper limit on the ortho-H2O fractional abundance is 7 × 10-8.
119922132
Transport beam line for ultraslow monoenergetic antiprotons
A beam line for the transportation of slow antiprotons from a multiring electrode trap to an experimental chamber is described. The beam line is equipped with a three-stage differential pumping system in order to maintain a pressure lower than 1×10−12 Torr in the trap region while simultaneously having a pressure of around 1×10−6 Torr in the chamber. Tests have shown that 105 positive ions per trapping cycle were successfully extracted at 250 eV from the trap positioned in a superconducting solenoid. The ions were then further transported through three small apertures to the target area located 3.5 m downstream of the trap. Results from the first delivery of a 250 eV antiproton beam are described.
121208627
Subthreshold production of strange hadrons in relativistic heavy ion collisions
We report on preliminary measurements of subthreshold antikaons produced in relativistic heavy ion collisions. Comparison with hadrochemical and transport models show that while the total level of antikaon production may be accounted for, important difficulties remain in describing their momentum and angular distributions.
22580845
Dynamical mass generation of composite Dirac fermions and fractional quantum Hall effects near charge neutrality in graphene.
We develop a composite Dirac fermion theory for the fractional quantum Hall effects (QHE) near charge neutrality in graphene. We show that the interactions between the composite Dirac fermions lead to a dynamical mass generation through exciton condensation. The four-fold spin-valley degeneracy is fully lifted due to the mass generation and exchange effects such that the odd-denominator fractional QHE observed in the vicinity of charge neutrality can be understood in terms of the integer QHE of composite Dirac fermions. At a filling factor ν = 1/2, we show that the massive composite Dirac fermion liquid is unstable against chiral p-wave pairing for weak Coulomb interactions and the ground state is a paired non-Abelian quantum Hall state described by the Moore-Read Pfaffian in the long wavelength limit.
16747983
Non-Abelian quantum Hall states and their quasiparticles: From the pattern of zeros to vertex algebra
In the pattern-of-zeros approach to quantum Hall states, a set of data (n;m;S{sub a}|a=1,...,n;n,m,S{sub a} is n element of N) (called the pattern of zeros) is introduced to characterize a quantum Hall wave function. In this paper we find sufficient conditions on the pattern of zeros so that the data correspond to a valid wave function. Some times, a set of data (n;m;S{sub a}) corresponds to a unique quantum Hall state, while other times, a set of data corresponds to several different quantum Hall states. So in the latter cases, the pattern of zeros alone does not completely characterize the quantum Hall states. In this paper, we find that the following expanded set of data (n;m;S{sub a};c|a=1,...,n;n,m,S{sub a} is an element of N;c is an element of R) provides a more complete characterization of quantum Hall states. Each expanded set of data completely characterizes a unique quantum Hall state, at least for the examples discussed in this paper. The result is obtained by combining the pattern of zeros and Z{sub n} simple-current vertex algebra which describes a large class of Abelian and non-Abelian quantum Hall states PHI{sub Z{sub n}{sup sc}}. The more complete characterization in terms of (n;m;S{sub a};c) allowsmore » us to obtain more topological properties of those states, which include the central charge c of edge states, the scaling dimensions and the statistics of quasiparticle excitations.« less
8540093
Analysis of the Y(4140) and related molecular states with QCD sum rules
In this article, we assume that there exist scalar ${D}^{\ast}{\bar {D}}^{\ast}$, ${D}_{s}^{\ast}{\bar{D}}_{s}^{\ast}$, ${B}^{\ast}{\bar {B}}^{\ast}$ and ${B}_{s}^{\ast}{\bar{B}}_{s}^{\ast}$ molecular states, and study their masses using the QCD sum rules. The numerical results indicate that the masses are about (250–500) MeV above the corresponding D*–${\bar{D}}^{\ast}$, Ds*–${\bar {D}}_{s}^{\ast}$, B*–${\bar{B}}^{\ast}$ and Bs*–${\bar {B}}_{s}^{\ast}$ thresholds, the Y(4140) is unlikely a scalar ${D}_{s}^{\ast}{\bar{D}}_{s}^{\ast}$ molecular state. The scalar $D^{\ast}{\bar{D}}^{\ast}$, $D_{s}^{\ast}{\bar{D}}_{s}^{\ast}$, $B^{\ast}{\bar{B}}^{\ast}$ and $B_{s}^{\ast}{\bar{B}}_{s}^{\ast}$ molecular states maybe not exist, while the scalar ${D'}^{\ast}{\bar{D}}^{\prime\ast}$, ${D}_{s}^{\prime\ast}{\bar{D}}_{s}^{\prime\ast}$, ${B}^{\prime\ast}{\bar{B}}^{\prime\ast}$ and ${B}_{s}^{\prime\ast}{\bar{B}}_{s}^{\prime\ast}$ molecular states maybe exist.
118873737
Laminar plasma dynamos
A new kind of dynamo utilizing flowing laboratory plasmas has been identified. The conversion of plasma kinetic energy to magnetic energy is verified numerically by kinematic dynamo simulations for magnetic Reynolds numbers above 210. As opposed to intrinsically-turbulent liquid-sodium dynamos, the proposed plasma dynamo corresponds to laminar flow topology. Modest plasma parameters (1–20 eV temperatures, 1019–1020 m−3 densities in 0.3–1.0 m scale-lengths driven by velocities on the order of the Alfven critical ionization velocity) self-consistently satisfy the conditions needed for the magnetic field amplication. Growth rates for plasma dynamos are obtained numerically with different geometry and magnetic Reynolds numbers. Magnetic-field-free coaxial plasma guns can be used to sustain the plasma flow and the dynamo.