1,779 research outputs found
Warm turbulence in the Boltzmann equation
We study the single-particle distributions of three-dimensional hard sphere
gas described by the Boltzmann equation. We focus on the steady homogeneous
isotropic solutions in thermodynamically open conditions, i.e. in the presence
of forcing and dissipation. We observe nonequilibrium steady state solution
characterized by a warm turbulence, that is an energy and particle cascade
superimposed on the Maxwell-Boltzmann distribution. We use a dimensional
analysis approach to relate the thermodynamic quantities of the steady state
with the characteristics of the forcing and dissipation terms. In particular,
we present an analytical prediction for the temperature of the system which we
show to be dependent only on the forcing and dissipative scales. Numerical
simulations of the Boltzmann equation support our analytical predictions.Comment: 4 pages, 5 figure
Superconductivity in the Cuprates as a Consequence of Antiferromagnetism and a Large Hole Density of States
We briefly review a theory for the cuprates that has been recently proposed
based on the movement and interaction of holes in antiferromagnetic (AF)
backgrounds. A robust peak in the hole density of states (DOS) is crucial to
produce a large critical temperature once a source of hole attraction is
identified. The predictions of this scenario are compared with experiments. The
stability of the calculations after modifying some of the original assumptions
is addressed. We find that if the dispersion is changed from an
antiferromagnetic band at half-filling to a tight binding
narrow band at , the main conclusions of the approach remain
basically the same i.e. superconductivity appears in the -channel and is enhanced by a large DOS. The main features
distinguishing these ideas from more standard theories based on
antiferromagnetic correlations are here discussed.Comment: RevTex, 7 pages, 5 figures are available on reques
Experimental assessment of immunoreactivity indices and effectiveness of pharmacotherapy schemes in surgical models of acute pancreatitis of various severity
The investigation was aimed at assessment of immunoreactivity in the experimental groups of animals and evaluation of effectiveness of different combinations of pharmacological drugs used in the surgical models for the treatment of acute pancreatitis (AP) of various degrees of severit
Ordered droplet structures at the liquid crystal surface and elastic-capillary colloidal interactions
We demonstrate a variety of ordered patterns, including hexagonal structures
and chains, formed by colloidal particles (droplets) at the free surface of a
nematic liquid crystal (LC). The surface placement introduces a new type of
particle interaction as compared to particles entirely in the LC bulk. Namely,
director deformations caused by the particle lead to distortions of the
interface and thus to capillary attraction. The elastic-capillary coupling is
strong enough to remain relevant even at the micron scale when its
buoyancy-capillary counterpart becomes irrelevant.Comment: 10 pages, 3 figures, to be published in Physical Review Letter
Extended bound states and resonances of two fermions on a periodic lattice
The high- cuprates are possible candidates for d-wave superconductivity,
with the Cooper pair wave function belonging to a non-trivial irreducible
representation of the lattice point group. We argue that this d-wave symmetry
is related to a special form of the fermionic kinetic energy and does not
require any novel pairing mechanism. In this context, we present a detailed
study of the bound states and resonances formed by two lattice fermions
interacting via a non-retarded potential that is attractive for nearest
neighbors but repulsive for other relative positions. In the case of strong
binding, a pair formed by fermions on adjacent lattice sites can have a small
effective mass, thereby implying a high condensation temperature. For a weakly
bound state, a pair with non-trivial symmetry tends to be smaller in size than
an s-wave pair. These and other findings are discussed in connection with the
properties of high- cuprate superconductors.Comment: 21 pages, RevTeX, 4 Postscript figures, arithmetic errors corrected.
An abbreviated version (no appendix) appeared in PRB on March 1, 199
Hole photoproduction in insulating copper oxide
Basing on t-J model we calculate the k-dependence of a single hole
photoproduction probability for CuO2 plane at zero doping. We also discuss the
radiation of spin-waves which can substantially deform the shape of
photoemission spectra.Comment: latex 8 pages, 3 figure
Surface alignment and anchoring transitions in nematic lyotropic chromonic liquid crystal
The surface alignment of lyotropic chromonic liquid crystals (LCLCs) can be
not only planar (tangential) but also homeotropic, with self-assembled
aggregates perpendicular to the substrate, as demonstrated by mapping optical
retardation and by three-dimensional imaging of the director field. With time,
the homeotropic nematic undergoes a transition into a tangential state. The
anchoring transition is discontinuous and can be described by a double-well
anchoring potential with two minima corresponding to tangential and homeotropic
orientation.Comment: Accepted for publication in Phys. Rev. Lett. (Accepted Wednesday Jun
02, 2010
Low energy states with different symmetries in the t-J model with two holes on a 32-site lattice
We study the low energy states of the t-J model with two holes on a 32-site
lattice with periodic boundary conditions. In contrary to common belief, we
find that the state with d_{x^2-y^2} symmetry is not always the ground state in
the realistic parameter range 0.2\le J/t\le 0.4. There exist low-lying
finite-momentum p-states whose energies are lower than the d_{x^2-y^2} state
when J/t is small enough. We compare various properties of these low energy
states at J/t=0.3 where they are almost degenerate, and find that those
properties associated with the holes (such as the hole-hole correlation and the
electron momentum distribution function) are very different between the
d_{x^2-y^2} and p states, while their spin properties are very similar.
Finally, we demonstrate that by adding ``realistic'' terms to the t-J model
Hamiltonian, we can easily destroy the d_{x^2-y^2} ground state. This casts
doubt on the robustness of the d_{x^2-y^2} state as the ground state in a
microscopic model for the high temperature superconductors
X-ray diffraction measurements of the c-axis Debye-Waller factors of YBa2Cu3O7 and HgBa2CaCu2O6
We report the first application of x-rays to the measurement of the
temperature dependent Bragg peak intensities to obtain Debye-Waller factors on
high-temperature superconductors. Intensities of (0,0,l) peaks of YBa2Cu3O7 and
HgBa2CaCu2O6 thin films are measured to obtain the c-axis Debye-Waller factors.
While lattice constant and some Debye-Waller factor measurements on high Tc
superconductors show anomalies at the transition temperature, our measurements
by x-ray diffraction show a smooth transition of the c-axis Debye-Waller
factors through T. This suggests that the dynamic displacements of the
heavy elements along the c-axis direction in these compounds do not have
anomalies at Tc. This method in combination with measurements by other
techniques will give more details concerning dynamics of the lattice.Comment: 4 pages, 2 figures. To be published in Physical Review B (Brief
Report
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