1,992 research outputs found
Three-dimensional Black Holes and Liouville Field Theory
A quantization of (2+1)-dimensional gravity with negative cosmological
constant is presented and quantum aspects of the (2+1)-dimensional black holes
are studied thereby. The quantization consists of two procedures. One is
related with quantization of the asymptotic Virasoro symmetry. A notion of the
Virasoro deformation of 3-geometry is introduced. For a given black hole, the
deformation of the exterior of the outer horizon is identified with a product
of appropriate coadjoint orbits of the Virasoro groups .
Its quantization provides unitary irreducible representations of the Virasoro
algebra, in which state of the black hole becomes primary. To make the
quantization complete, holonomies, the global degrees of freedom, are taken
into account. By an identification of these topological operators with zero
modes of the Liouville field, the aforementioned unitary representations
reveal, as far as , as the Hilbert space of this two-dimensional
conformal field theory. This conformal field theory, living on the cylinder at
infinity of the black hole and having continuous spectrums, can recognize the
outer horizon only as a it one-dimensional object in and
realize it as insertions of the corresponding vertex operator. Therefore it can
not be a conformal field theory on the horizon. Two possible descriptions of
the horizon conformal field theory are proposed.Comment: 39 pages, LaTeX, 8 figures are added. Section 4.3 is revised and
enlarged to include the case of conical singularities. Several typos are
corrected. References are adde
Anomalous Nernst Effect in Nonmagnetic Nodal Line Semimetal PbTaSe
PbTaSe is a unique topological material, in which the number of nodal
lines is expected to change at the structural transition between the lower
temperature/pressure "L" phase and the higher temperature/pressure "H" phase.
We report the anomalous Nernst effect attributed to the Berry curvature of
nodal lines and its change with the structural transition. In the L phase, the
Nernst coefficient () shows the step-like magnetic field dependence
reminiscent of the anomalous Nernst effect of nonmagnetic Dirac/Weyl
semimetals. By applying hydrostatic pressure, we discovered that the amplitude
of the anomalous component significantly decreases at the transition to the H
phase, which might correspond to the partial annihilation of nodal line
structures.Comment: 29 page, 14 figure
Amelioration of normothermic canine liver ischemia with prostacyclin.
A model of hepatic ischemia was developed in dogs using a pump-driven splanchnic-to-jugular vein bypass during crossclamping of the portal triad. An LD50 was established with three hours of ischemia. PGI2 given for one hour before the ischemic insult ameliorated the ischemic injury and increased survival
Ferromagnetism, paramagnetism and a Curie-Weiss metal in an electron doped Hubbard model on a triangular lattice
Motivated by the unconventional properties and rich phase diagram of NaxCoO2
we consider the electronic and magnetic properties of a two-dimensional Hubbard
model on an isotropic triangular lattice doped with electrons away from
half-filling. Dynamical mean-field theory (DMFT) calculations predict that for
negative inter-site hopping amplitudes (t<0) and an on-site Coulomb repulsion,
U, comparable to the bandwidth, the system displays properties typical of a
weakly correlated metal. In contrast, for t>0 a large enhancement of the
effective mass, ferromagnetism and a Curie-Weiss magnetic susceptibility are
found in a broad electron doping range. Our observation of Nagaoka
ferromagnetism is consistent with the A-type antiferromagnetism (i.e.
ferromagnetic layers stacked antiferromagnetically) observed in neutron
scattering experiments on NaxCoO2. We propose that `Curie-Weiss metal' phase
observed in NaxCoO2 is a consequence of the crossover from ``bad metal'' with
incoherent quasiparticles at temperatures T>T* and Fermi liquid behavior with
enhanced parameters below T*, where T* is a low energy coherence scale induced
by strong local Coulomb electron correlations. We propose a model which
contains the charge ordering phenomena observed in the system which, we
propose, drives the system close to the Mott insulating phase even at large
dopings.Comment: 24 pages, 15 figures; accepted for publication in Phys. Rev.
Specific heat amplitude ratios for anisotropic Lifshitz critical behaviors
We determine the specific heat amplitude ratio near a -axial Lifshitz
point and show its universal character. Using a recent renormalization group
picture along with new field-theoretical -expansion techniques,
we established this amplitude ratio at one-loop order. We estimate the
numerical value of this amplitude ratio for and . The result is in
very good agreement with its experimental measurement on the magnetic material
. It is shown that in the limit it trivially reduces to the
Ising-like amplitude ratio.Comment: 8 pages, RevTex, accepted as a Brief Report in Physical Review
NMR studies of Successive Phase Transitions in Na0.5CoO2 and K0.5CoO2
59Co- and 23Na-NMR measurements have been carried out on polycrystalline and
c-axis aligned samples of Na0.5CoO2, which exhibits successive transitions at
temperatures T = 87 K (= Tc1) and T = 53 K (= Tc2). 59Co-NMR has also been
carried out on c-axis aligned crystallites of K0.5CoO2 with similar successive
transitions at Tc1 ~ 60 K and Tc2 ~ 20 K. For Na0.5CoO2, two sets of three NMR
lines of 23Na nuclei explained by considering the quadrupolar frequencies nuQ
~1.32 and 1.40 MHz have been observed above Tc1, as is expected from the
crystalline structure. Rather complicated but characteristic variation of the
23Na-NMR spectra has been observed with varying T through the transition
temperatures, and the internal fields at two crystallographically distinct Na
sites are discussed on the basis of the magnetic structures reported
previously. The internal fields at two distinct Co sites observed below Tc1 and
the 591/T1-T curves of Na0.5CoO2 and K0.5CoO2 are also discussed in a
comparative way.Comment: 7 pages, 10 figures, submitted to J. Phys. Soc. Jpn, correction is
made in right colum of p6 (35th line) as K0.5CoO2-->Na0.5CoO
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