170 research outputs found
Relating c<0 and c>0 Conformal Field Theories
A `canonical mapping' is established between the c=-1 system of bosonic
ghosts and the c=2 complex scalar theory and, a similar mapping between the
c=-2 system of fermionic ghosts and the c=1 Dirac theory. The existence of this
mapping is suggested by the identity of the characters of the respective
theories. The respective c0 theories share the same space of states,
whereas the spaces of conformal fields are different. Upon this mapping from
their c0) complex scalar and the Dirac theories inherit
hidden nonlocal sl(2) symmetries.Comment: 23 pages, harvma
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Drying and reconstitution of subbituminous coal - CRADA 90-004. Final report
AMAX Coal Company (AMAX) has built a 200 tph, demonstration scale fluidized-bed drying process at their Belle Ayr Mine in Wyoming to dry the subbituminous coal of Wyodak seam from an average moisture content of 25-30 wt% to about 10 wt%. Currently, the dryer generates too many fines for proper transportation and handling. Though the raw coal is about 2-inch top size, about 80 wt% of the dryer product ends up finer than 28 mesh, and about 10 wt% of the dried coal is collected in the dryer bag house (minus 200 mesh). Paul Woessner, Director of Research and Development of AMAX, met with personnel from PETC Coal Preparation Division and expressed an interest in an investigation of the feasibility of applying the PETC`s humic acid binder to reconstitute the bag house fines from the dryer. This was an area in which PETC had been doing some research and had some expertise. As a result, AMAX and the U.S. Department of Energy`s Pittsburgh Energy Technology Center (PETC) signed a Cooperative Research and Development Agreement (CRADA, see appendix A) in June 1990 to produce, from fine subbituminous coal, economic low moisture reconstituted solid fuel forms that have suitable storage, handling, transportation, and combustion properties. PETC`s task in this agreement was to conduct broad, baseline studies in three areas: (1) to develop a humic acid binder from AMAX subbituminous coal using the PETC-developed Humic Acid Binder Process, (2) to reconstitute AMAX`s dried subbituminous coal fines from the bag house and the fluidized bed dryer product with humic acid binder, and (3) to produce low moisture, water-resistant pellets from raw subbituminous coal by the PETC-developed Lignipel Process. AMAX, on the other hand, agreed to produce 1-2 tons of reconstituted solid fuel for handleability and combustion tests and partially funded PETC`s efforts
Ring exchange, the Bose metal, and bosonization in two dimensions
Motivated by the high-T_c cuprates, we consider a model of bosonic Cooper
pairs moving on a square lattice via ring exchange. We show that this model
offers a natural middle ground between a conventional antiferromagnetic Mott
insulator and the fully deconfined fractionalized phase which underlies the
spin-charge separation scenario for high-T_c superconductivity. We show that
such ring models sustain a stable critical phase in two dimensions, the *Bose
metal*. The Bose metal is a compressible state, with gapless but uncondensed
boson and ``vortex'' excitations, power-law superconducting and charge-ordering
correlations, and broad spectral functions. We characterize the Bose metal with
the aid of an exact plaquette duality transformation, which motivates a
universal low energy description of the Bose metal. This description is in
terms of a pair of dual bosonic phase fields, and is a direct analog of the
well-known one-dimensional bosonization approach. We verify the validity of the
low energy description by numerical simulations of the ring model in its exact
dual form. The relevance to the high-T_c superconductors and a variety of
extensions to other systems are discussed, including the bosonization of a two
dimensional fermionic ring model
Role of Inter-Electron Interaction in the Pseudo-Gap Opening in High T Tunneling Experiments
The analysis of tunneling experiments showing the pseudogap type behavior is
carried out based on the idea of the renormalization of density of states due
to the inter-electron interaction in the Cooper channel (superconducting
fluctuations contribution in tunneling current). It is demonstrated that the
observed kink of the zero-bias conductance of junctions in
the vicinity of can be explained in terms of fluctuation theory in a
quite wide range of temperature above , using the values of microscopic
parameters of the electron spectrum taken from independent
experiments. The approach proposed also permits to explain qualitatively the
shape of the tunneling anomalies in and gives a correct estimate for
the pseudogap position and amplitude observed in the experiments on
junctions.Comment: 5 pages, 3 figure
Detector Description and Performance for the First Coincidence Observations between LIGO and GEO
For 17 days in August and September 2002, the LIGO and GEO interferometer
gravitational wave detectors were operated in coincidence to produce their
first data for scientific analysis. Although the detectors were still far from
their design sensitivity levels, the data can be used to place better upper
limits on the flux of gravitational waves incident on the earth than previous
direct measurements. This paper describes the instruments and the data in some
detail, as a companion to analysis papers based on the first data.Comment: 41 pages, 9 figures 17 Sept 03: author list amended, minor editorial
change
Geochemistry and mineralogy of the phonolite lava lake, Erebus volcano, Antarctica: 1972–2004 and comparison with older lavas
Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Journal of Volcanology and Geothermal Research 177 (2008): 589-605, doi:10.1016/j.jvolgeores.2007.11.025.Mount Erebus, Antarctica, is a large (3794 m) alkaline open-conduit stratovolcano that
hosts a vigorously convecting and persistently degassing lake of anorthoclase phonolite magma.
The composition of the lake was investigated by analyzing glass and mineral compositions in
lava bombs erupted between 1972 and 2004. Matrix glass, titanomagnetite, olivine,
clinopyroxene, and fluor-apatite compositions are invariant and show that the magmatic
temperature (~1000°C) and oxygen fugacity (ΔlogFMQ = -0.9) have been stable. Large
temperature variations at the lake surface (ca. 400 - 500°C) are not reflected in mineral
compositions. Anorthoclase phenocrysts up to 10 cm in length feature a restricted compositional
range (An10.3-22.9Ab62.8-68.1Or11.4-27.2) with complex textural and compositional zoning.
Anorthoclase textures and compositions indicate crystallization occurs at low degrees of
effective undercooling. We propose shallow water exsolution causes crystallization to occur and
shallow convection repeats this process multiple times, yielding extremely large anorthoclase
crystals. Minor variations in eruptive activity from 1972 to 2004 are decoupled from magma
compositions. The variations probably relate to changes in conduit geometry within the volcano
and/or variable input of CO2-rich volatiles into the upper-level magma chamber from deeper in
the system.
Eleven bulk samples of phonolite lava from the summit plateau that range in age from 0 ±
4 ka to 17 ± 8 ka were analyzed for major and trace elements. Small compositional variations
are controlled by anorthoclase content. The lavas are indistinguishable from modern bulk lava
bomb compositions and demonstrate that Erebus volcano has been erupting lava and tephra from
the summit region with the same bulk composition for ~17 ka.The work at Erebus volcano and the continued operation of the Mount Erebus Volcano
Observatory is supported by grants (OPP-0229305, ANT-0538414) from the Office of Polar
Programs, National Science Foundation
The International Pulsar Timing Array: First data release
International audienceThe highly stable spin of neutron stars can be exploited for a variety of (astro)physical investigations. In particular, arrays of pulsars with rotational periods of the order of milliseconds can be used to detect correlated signals such as those caused by gravitational waves. Three such 'pulsar timing arrays' (PTAs) have been set up around the world over the past decades and collectively form the 'International' PTA (IPTA). In this paper, we describe the first joint analysis of the data from the three regional PTAs, i.e. of the first IPTA data set. We describe the available PTA data, the approach presently followed for its combination and suggest improvements for future PTA research. Particular attention is paid to subtle details (such as underestimation of measurement uncertainty and long-period noise) that have often been ignored but which become important in this unprecedentedly large and inhomogeneous data set. We identify and describe in detail several factors that complicate IPTA research and provide recommendations for future pulsar timing efforts. The first IPTA data release presented here (and available on-line) is used to demonstrate the IPTA's potential of improving upon gravitational-wave limit
Effect of event selection on jetlike correlation measurement in d+Au collisions at sNN=200 GeV
AbstractDihadron correlations are analyzed in sNN=200 GeV d+Au collisions classified by forward charged particle multiplicity and zero-degree neutral energy in the Au-beam direction. It is found that the jetlike correlated yield increases with the event multiplicity. After taking into account this dependence, the non-jet contribution on the away side is minimal, leaving little room for a back-to-back ridge in these collisions
Beam-energy Dependence Of Charge Balance Functions From Au + Au Collisions At Energies Available At The Bnl Relativistic Heavy Ion Collider
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Balance functions have been measured in terms of relative pseudorapidity (Δη) for charged particle pairs at the BNL Relativistic Heavy Ion Collider from Au + Au collisions at sNN=7.7GeV to 200 GeV using the STAR detector. These results are compared with balance functions measured at the CERN Large Hadron Collider from Pb + Pb collisions at sNN=2.76TeV by the ALICE Collaboration. The width of the balance function decreases as the collisions become more central and as the beam energy is increased. In contrast, the widths of the balance functions calculated using shuffled events show little dependence on centrality or beam energy and are larger than the observed widths. Balance function widths calculated using events generated by UrQMD are wider than the measured widths in central collisions and show little centrality dependence. The measured widths of the balance functions in central collisions are consistent with the delayed hadronization of a deconfined quark gluon plasma (QGP). The narrowing of the balance function in central collisions at sNN=7.7 GeV implies that a QGP is still being created at this relatively low energy. © 2016 American Physical Society.942CNPq, Conselho Nacional de Desenvolvimento Científico e TecnológicoMinistry of Education and Science of the Russian FederationMOE, Ministry of Education of the People's Republic of ChinaMOST, Ministry of Science and Technology of the People's Republic of ChinaNRF-2012004024, National Research FoundationNSF, National Stroke FoundationConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq
All-sky search for long-duration gravitational wave transients with initial LIGO
We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10-500 s in a frequency band of 40-1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. For signals from black hole accretion disk instabilities, we set upper limits on the source rate density between 3.4×10-5 and 9.4×10-4 Mpc-3 yr-1 at 90% confidence. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves. © 2016 American Physical Society
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