9,062 research outputs found
Cuntz-Krieger algebras associated with Hilbert -quad modules of commuting matrices
Let be the -algebra associated with
the Hilbert -quad module arising from commuting matrices with
entries in . We will show that if the associated tiling space
is transitive, the -algebra is simple and purely infinite. In particulr, for two positive
integers , the -groups of the simple purely infinite -algebra
are computed by using the Euclidean
algorithm.Comment: 19 page
N=4 Supersymmetric Yang-Mills on S^3 in Plane Wave Matrix Model at Finite Temperature
We investigate the large N reduced model of gauge theory on a curved
spacetime through the plane wave matrix model. We formally derive the action of
the N=4 supersymmetric Yang-Mills theory on R \times S^3 from the plane wave
matrix model in the large N limit. Furthermore, we evaluate the effective
action of the plane wave matrix model up to the two-loop level at finite
temperature. We find that the effective action is consistent with the free
energy of the N=4 supersymmetric Yang-Mills theory on S^3 at high temperature
limit where the planar contributions dominate. We conclude that the plane wave
matrix model can be used as a large N reduced model to investigate
nonperturbative aspects of the N=4 supersymmetric Yang-Mills theory on R \times
S^3.Comment: 31pages: added comments and reference
New Kinetic Equation for Pair-annihilating Particles: Generalization of the Boltzmann Equation
A convenient form of kinetic equation is derived for pair annihilation of
heavy stable particles relevant to the dark matter problem in cosmology. The
kinetic equation thus derived extends the on-shell Boltzmann equation in a most
straightforward way, including the off-shell effect. A detailed balance
equation for the equilibrium abundance is further analyzed. Perturbative
analysis of this equation supports a previous result for the equilibrium
abundance using the thermal field theory, and gives the temperature power
dependence of equilibrium value at low temperatures. Estimate of the relic
abundance is possible using this new equilibrium abundance in the sudden
freeze-out approximation.Comment: 19 pages, LATEX file with 2 PS figure
Molecular ferroelectric contributions to anomalous hysteresis in hybrid perovskite solar cells
We report a model describing the molecular orientation disorder in
CH3NH3PbI3, solving a classical Hamiltonian parametrised with electronic
structure calculations, with the nature of the motions informed by ab-initio
molecular dynamics. We investigate the temperature and static electric field
dependence of the equilibrium ferroelectric (molecular) domain structure and
resulting polarisability. A rich domain structure of twinned molecular dipoles
is observed, strongly varying as a function of temperature and applied electric
field. We propose that the internal electrical fields associated with
microscopic polarisation domains contribute to hysteretic anomalies in the
current--voltage response of hybrid organic-inorganic perovskite solar cells
due to variations in electron-hole recombination in the bulk.Comment: 10 pages; 4 figures, 2 SI figure
Generic phase diagram of "electron-doped" T' cuprates
We investigated the generic phase diagram of the electron doped
superconductor, Nd2-xCexCuO4, using films prepared by metal organic
decomposition. After careful oxygen reduction treatment to remove interstitial
Oap atoms, we found that the Tc increases monotonically from 24 K to 29 K with
decreasing x from 0.15 to 0.00, demonstrating a quite different phase diagram
from the previous bulk one. The implication of our results is discussed on the
basis of tremendous influence of Oap "impurities" on superconductivity and also
magnetism in T' cuprates. Then we conclude that our result represents the
generic phase diagram for oxygen-stoichiometric Nd2-xCexCuO4.Comment: 12 pages, 4 figures; International Symposium on Superconductivity
(ISS) 200
Measurement by FIB on the ISS: Two Emissions of Solar Neutrons Detected?
A new type of solar neutron detector (FIB) was launched onboard the Space
Shuttle Endeavour on July 16, 2009, and it began collecting data at the
International Space Station (ISS) on August 25, 2009. This paper summarizes the
three years of observations obtained by the solar neutron detector FIB until
the end of July 2012. The solar neutron detector FIB can determine both the
energy and arrival direction of neutrons. We measured the energy spectra of
background neutrons over the SAA region and elsewhere, and found the typical
trigger rates to be 20 counts/sec and 0.22 counts/sec, respectively. It is
possible to identify solar neutrons to within a level of 0.028 counts/sec,
provided that directional information is applied. Solar neutrons were observed
in association with the M-class solar flares that occurred on March 7 (M3.7)
and June 7 (M2.5) of 2011. This marked the first time that neutrons were
observed in M-class solar flares. A possible interpretaion of the prodcution
process is provided.Comment: 36 pages, 16 figures, and 3 Tables; Advanced in Astronmy, 2012,
Special issue on Cosmic Ray Variablity:Century of Its Obseravtion
Nonlocal Charges for Bonus Yangian Symmetries of Super-Yang-Mills
The existence of a "bonus" U(1) level-one Yangian symmetry of N=4
super-Yang-Mills has recently been proposed. We provide evidence for this
proposal by constructing the BRST-invariant nonlocal charge in the pure spinor
sigma model corresponding to this bonus level-one symmetry. We also construct
analogous charges for bonus U(1) symmetries at all odd levels of the Yangian.Comment: LaTeX 16p
Spectral properties of a spin-incoherent Luttinger Liquid
We present time-dependent density matrix renormalization group (DMRG) results
for strongly interacting one dimensional fermionic systems at finite
temperature. When interactions are strong the characteristic spin energy can be
greatly suppressed relative to the characteristic charge energy, allowing for
the possibility of spin-incoherent Luttinger liquid physics when the
temperature is high compared to the spin energy, but small compared to the
charge energy. Using DMRG we compute the spectral properties of the model
at arbitrary temperatures with respect to both spin and charge energies. We
study the full crossover from the Luttinger liquid regime to the
spin-incoherent regime,focusing on small , where the signatures of
spin-incoherent behavior are more manifest. Our method allows us to access the
analytically intractable regime where temperature is of the order of the spin
energy, . Our results should be helpful in the interpretation of
experiments that may be in the crossover regime, , and apply to
one-dimensional cold atomic gases where finite-temperature effects are
appreciable. The technique may also be used to guide the development of
analytical approximations for the crossover regime.Comment: 7 pages, 5 figure
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