3,710 research outputs found
Boundedness of multilinear pseudo-differential operators on modulation spaces
Boundedness results for multilinear pseudodifferential operators on products
of modulation spaces are derived based on ordered integrability conditions on
the short-time Fourier transform of the operators' symbols. The flexibility and
strength of the introduced methods is demonstrated by their application to the
bilinear and trilinear Hilbert transform.Comment: 29 pages, journal submissio
Ten years of INTEGRAL observations of the hard X-ray emission from SGR 1900+14
We exploited the high sensitivity of the INTEGRAL IBIS/ISGRI instrument to
study the persistent hard X-ray emission of the soft gamma-ray repeater SGR
1900+14, based on ~11.6 Ms of archival data. The 22-150 keV INTEGRAL spectrum
can be well fit by a power law with photon index 1.9 +/- 0.3 and flux F_x =
(1.11 +/- 0.17)E-11 erg/cm^2/s (20-100 keV). A comparison with the 20-100 keV
flux measured in 1997 with BeppoSAX, and possibly associated with SGR 1900+14,
shows a luminosity decrease by a factor of ~5. The slope of the power law above
20 keV is consistent within the uncertainties with that of SGR 1806-20, the
other persistent soft gamma-ray repeater for which a hard X-ray emission
extending up to 150 keV has been reported.Comment: Accepted for publication in Astronomy & Astrophysics. 4 page
Poisson-Lie T-dual sigma models on supermanifolds
We investigate Poisson-Lie symmetry for T-dual sigma models on supermanifolds
in general and on Lie supergroups in particular. We show that the integrability
condition on this super Poisson-Lie symmetry is equivalent to the super Jacobi
identities of the Lie super-bialgebras. As examples we consider models related
to four dimensional Lie super-bialgebras and
. Then generally it is shown that for Abelian case (g, I)
the super Poisson-Lie T-duality transforms the role of fermionic (bosonic)
fields in the model to bosonic (fermionic) fields on the dual model and vice
versa.Comment: 13 pages, Revised and accepted for publication in JHE
Generic susceptibilities of the half-filled Hubbard model in infinite dimensions
Around a metal-to-insulator transition driven by repulsive interaction (Mott
transition) the single particle excitations and the collective excitations are
equally important. Here we present results for the generic susceptibilities at
zero temperature in the half-filled Hubbard model in infinite dimensions.
Profiting from the high resolution of dynamic density-matrix renormalization at
all energies, results for the charge, spin and Cooper-pair susceptibilities in
the metallic and the insulating phase are computed. In the insulating phase, an
almost saturated local magnetic moment appears. In the metallic phase a
pronounced low-energy peak is found in the spin response.Comment: 12 pages, 12 figures; slight changes and one additional figure due to
referees' suggestion
Increased plasma viscosity as a reason for inappropriate erythropoietin formation
The aim of this study was to examine whether altered plasma viscosity could contribute to the inappropriately low production rate of erythropoietin (EPO) observed in patients suffering from hypergammaglobulinemias associated with multiple myeloma or Waldenström's disease. We found that the EPO formation in response to anemia in these patients was inversely related to plasma viscosity. A similar inverse relationship between plasma viscosity and EPO production was seen in rats in which EPO formation had been stimulated by exchange transfusion and the plasma viscosity of which was thereby altered by using exchange solutions of different composition to alter plasma viscosity and thus whole blood viscosity independently from hematocrit. Raising the gammaglobulin concentration to approximately 40 mg/ml plasma in the rats almost totally blunted the rise in serum EPO levels despite a fall of the hematocrit to 20%. Determination of renal EPO mRNA levels by RNase protection revealed that the reductions in serum EPO levels at higher plasma viscosities were paralleled by reductions in renal EPO mRNA levels. Taken together, our findings suggest that plasma viscosity may be a significant inhibitory modulator of anemia-induced EPO formation. The increased plasma viscosity in patients with hypergammaglobulinemias may therefore contribute to the inappropriate EPO production, which is a major reason for the anemia developing in these patients
Evidence for the PSL(22) Wess-Zumino-Novikov-Witten model as a model for the plateau transition in Quantum Hall effect: Evaluation of numerical simulations
In this paper I revise arguments in favour of the PSL(22)
Wess-Zumino-Novikov-Witten (WZNW) model as a theory of the plateau transition
in Integer Quantum Hall effect. I show that all available numerical data
(including the correlation length exponent ) are consistent with the
predictions of such WZNW model with the level .Comment: 11 pages, no figure
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