12,534 research outputs found
Transmogrifying Fuzzy Vortices
We show that the construction of vortex solitons of the noncommutative
Abelian-Higgs model can be extended to a critically coupled gauged linear sigma
model with Fayet-Illiopolous D-terms. Like its commutative counterpart, this
fuzzy linear sigma model has a rich spectrum of BPS solutions. We offer an
explicit construction of the degree static semilocal vortex and study in
some detail the infinite coupling limit in which it descends to a degree
\C\Pk^{N} instanton. This relation between the fuzzy vortex and
noncommutative lump is used to suggest an interpretation of the noncommutative
sigma model soliton as tilted D-strings stretched between an NS5-brane and a
stack of D3-branes in type IIB superstring theory.Comment: 21 pages, 4 figures, LaTeX(JHEP3
Supersymmetric black rings and three-charge supertubes
We present supergravity solutions for 1/8-supersymmetric black supertubes
with three charges and three dipoles. Their reduction to five dimensions yields
supersymmetric black rings with regular horizons and two independent angular
momenta. The general solution contains seven independent parameters and
provides the first example of non-uniqueness of supersymmetric black holes. In
ten dimensions, the solutions can be realized as D1-D5-P black supertubes. We
also present a worldvolume construction of a supertube that exhibits three
dipoles explicitly. This description allows an arbitrary cross-section but
captures only one of the angular momenta.Comment: 59 pages, 6 figures; v2: minor correction
Noncommutative Solitons and Intersecting D-Branes
We construct intersecting D-branes as noncommutative solitons in bosonic and
type II string theory. ``Defect'' branes which are D-branes containing bubbles
of the closed string vacuum play an important role in the construction.Comment: 17 pages, harvmac; published version with added clarification
Path-integral calculation of the third virial coefficient of quantum gases at low temperatures
We derive path-integral expressions for the second and third virial
coefficients of monatomic quantum gases. Unlike previous work that considered
only Boltzmann statistics, we include exchange effects (Bose-Einstein or
Fermi-Dirac statistics). We use state-of-the-art pair and three-body potentials
to calculate the third virial coefficient of 3He and 4He in the temperature
range 2.6-24.5561 K. We obtain uncertainties smaller than those of the limited
experimental data. Inclusion of exchange effects is necessary to obtain
accurate results below about 7 K.Comment: The following article has been accepted by The Journal of Chemical
Physics. After it is published, it will be found at http://jcp.aip.org/
Version 2 includes the corrections detailed in the Erratu
Bipolar Magnetic Regions on the Sun: Global Analysis of the SOHO/MDI Data Set
The magnetic flux that is generated by dynamo inside the Sun emerges in the
form of bipolar magnetic regions. We have analyzed the whole set of solar
magnetograms obtained with the SOHO/MDI instrument in 1995-2011, and
automatically identified 160,079 bipolar magnetic regions that span a range of
scale sizes across nearly four orders of magnitude. Their properties have been
statistically analyzed, in particular with respect to the polarity orientations
of the bipolar regions, including their tilt angle distributions. The latitude
variation of the average tilt angles (with respect to the E-W direction), known
as Joy's law, is found to closely follow the relation 32.1*sin(latitude)[deg].
There is no indication of a dependence on region size that one may expect if
the tilts were produced by the Coriolis force during the buoyant rise of flux
loops from the tachocline region. A few percent of all regions have
orientations that violate Hale's polarity law. We show examples, from different
phases of the solar cycle, where well defined medium-size bipolar regions with
opposite polarity orientations occur side by side in the same latitude zone.
Such oppositely oriented large bipolar regions cannot be part of the same
toroidal flux system, but different flux systems must coexist in the same
latitude zones. These examples are incompatible with the paradigm of coherent,
subsurface toroidal flux ropes as the source of sunspots, and instead show that
fluctuations must play a major role at all scales for the turbulent dynamo. We
see no observational support for a separation of scales or a division between a
global and a local dynamo, since also the smallest scales in the data set
retain a non-random component that significantly contributes to the accumulated
emergence of a N-S dipole moment that leads to the replacement of the old
global poloidal field with a new one that has the opposite orientation.Comment: 38 pages, 9 figures; to appear in the Astrophysical Journa
Solitons of Sigma Model on Noncommutative Space as Solitons of Electron System
We study the relationship of soliton solutions for electron system with those
of the sigma model on the noncommutative space, working directly in the
operator formalism. We find that some soliton solutions of the sigma model are
also the solitons of the electron system and are classified by the same
topological numbers.Comment: 12 pages, LaTeX2e, improvements to discussions, Version to be
published in JHE
Lost equivalence of nonlinear sigma and models on noncommutative space
We show that the equivalence of nonlinear sigma and models which is
valid on the commutative space is broken on the noncommutative space. This
conclusion is arrived at through investigation of new BPS solitons that do not
exist in the commutative limit.Comment: 17 pages, LaTeX2
Conversion of lignocellulose from palm (Elaeis guineensis) fruit fibre and physic (Jatropha curcas) nut shell into bio-oil
Harmful gases are released into the atmosphere through burning of residues which is commonly practiced in Nigeria and can be attributed to climate change issues. Agricultural residues have the potentials to be used as energy and chemical source and meet its deficit in the country. This paper focuses on utilization of lignocellulosic materials obtained from two agricultural residues through renewable technology to produce bio-energy and chemical feedstock. The lignocellulosic materials were extracted from palm fruit (Elaeis guineensis) fibre and physic nut (Jatropha curcas) shell, and pyrolyzed under low temperature and pressure at various particle sizes. The main properties of solid (lignocellulosic) materials were tested and the bio-oil produced was analyzed using GC-MS. Results show proximate analyses (volatile, ash and fixed carbon contents) and ultimate analysis (carbon, oxygen, nitrogen, magnesium, phosphorus and zinc). The pH value of the bio-oil from both residues increased with increase in temperatures. The density, viscosity and calorific value of the palm and physic residue oil are 831.99 and 947.5 kg/m3, 0.695 and 1.58 cPa at room temperature, 22.33 and 14.169 kJ/g, respectively. Aromatics and other compounds are major dominant compounds in the palm fruit fibre oil which is characterized for bio-fuel production. Physic nut shell oil contains aromatic ethers, cyclic ethers, secondary amides and organic halogen compound which are important chemical feedstock. Conversion of these residues to useful products will alleviate the energy supply deficit, improve social and economic development, promote clean and healthy atmosphere of the nation and significantly contribute to global climate change mitigation
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