610 research outputs found
Efficient calculation of the antiferromagnetic phase diagram of the 3D Hubbard model
The Dynamical Cluster Approximation with Betts clusters is used to calculate
the antiferromagnetic phase diagram of the 3D Hubbard model at half filling.
Betts clusters are a set of periodic clusters which best reflect the properties
of the lattice in the thermodynamic limit and provide an optimal finite-size
scaling as a function of cluster size. Using a systematic finite-size scaling
as a function of cluster space-time dimensions, we calculate the
antiferromagnetic phase diagram. Our results are qualitatively consistent with
the results of Staudt et al. [Eur. Phys. J. B 17 411 (2000)], but require the
use of much smaller clusters: 48 compared to 1000
Structural precursor to freezing: An integral equation study
Recent simulation studies have drawn attention to the shoulder which forms in
the second peak of the radial distribution function of hard-spheres at
densities close to freezing and which is associated with local crystalline
ordering in the dense fluid. We address this structural precursor to freezing
using an inhomogeneous integral equation theory capable of describing local
packing constraints to a high level of accuracy. The addition of a short-range
attractive interaction leads to a well known broadening of the fluid-solid
coexistence region as a function of attraction strength. The appearence of a
shoulder in our calculated radial distribution functions is found to be
consistent with the broadened coexistence region for a simple model potential,
thus demonstrating that the shoulder is not exclusively a high density packing
effect
Statistical mechanical description of liquid systems in electric field
We formulate the statistical mechanical description of liquid systems for
both polarizable and polar systems in an electric field in the
-ensemble, which is the pendant to the thermodynamic description in
terms of the free energy at constant potential. The contribution of the
electric field to the configurational integral in
the -ensemble is given in an exact form as a factor in the
integrand of . We calculate the contribution of the
electric field to the Ornstein-Zernike formula for the scattering function in
the -ensemble. As an application we determine the field induced
shift of the critical temperature for polarizable and polar liquids, and show
that the shift is upward for polarizable liquids and downward for polar
liquids.Comment: 6 page
Probing spatial spin correlations of ultracold gases by quantum noise spectroscopy
Spin noise spectroscopy with a single laser beam is demonstrated
theoretically to provide a direct probe of the spatial correlations of cold
fermionic gases. We show how the generic many-body phenomena of anti-bunching,
pairing, antiferromagnetic, and algebraic spin liquid correlations can be
revealed by measuring the spin noise as a function of laser width, temperature,
and frequency.Comment: Revised version. 4 pages, 3 figures. Accepted for PR
On the Momentum Distribution and Condensate Fraction in the Bose Liquid
The model recently proposed by A.A. Shanenko [Phys. Lett. A 227 (1997) 367]
is used to derive linear integro-differential equations whose solutions provide
reasonable estimates for the momentum distribution and condensate fraction in
interacting many-boson system at zero temperature. An advantage of these
equations is that they can be employed in the weak coupling regime and beyond.
As an example, analytical treatment of the weak coupling case is given.Comment: 12 pages, REVTEX, no figures, submitted to Phys. Lett.
Production Associated to Rare Events in High Energy Hadron-Hadron Collisions
At very high energy the same universal relation between the multiparticle or
the transverse energy distribution associated to a rare event , and
the corresponding minimum bias distribution P, , or works for nucleus-nucleus collisions as well as
for hadron-hadron collisions. This suggests that asymptotically, all hadronic
processes are similar.Comment: 9 pages, 4 Postscript figure
A unified treatment of Ising model magnetizations
We show how the spontaneous bulk, surface and corner magnetizations in the
square lattice Ising model can all be obtained within one approach. The method
is based on functional equations which follow from the properties of corner
transfer matrices and vertex operators and which can be derived graphically. In
all cases, exact analytical expressions for general anisotropy are obtained.
Known results, including several for which only numerical computation was
previously possible, are verified and new results related to general anisotropy
and corner angles are obtained.Comment: Plain Tex, 30 pages, 21 figures in eps format. Revised for
publication in Annalen der Physi
Phase transition in a 2-dimensional Heisenberg model
We investigate the two-dimensional classical Heisenberg model with a
nonlinear nearest-neighbor interaction
V(s,s')=2K[(1+s.s')/2 ]^p.
The analogous nonlinear interaction for the XY model was introduced by
Domany, Schick, and Swendsen, who find that for large p the Kosterlitz-Thouless
transition is preempted by a first-order transition. Here we show that, whereas
the standard (p=1) Heisenberg model has no phase transition, for large enough p
a first-order transition appears. Both phases have only short range order, but
with a correlation length that jumps at the transition.Comment: 6 pages, 5 encapsulated postscript figures; to appear in Physical
Review Letter
Magnetic Properties of the Novel Low-Dimensional Cuprate Na5RbCu4(AsO4)4Cl2
The magnetic properties of a new compound, Na5RbCu4(AsO4)4Cl2 are reported.
The material has a layered structure comprised of square Cu4O4 tetramers. The
Cu ions are divalent and the system behaves as a low-dimensional S=1/2
antiferromagnet. Spin exchange in Na5RbCu4(AsO4)4Cl2 appears to be
quasi-two-dimensional and non-frustrated. Measurements of the bulk magnetic
susceptibility and heat capacity are consistent with low-dimensional magnetism.
The compound has an interesting, low-entropy, magnetic transition at T = 17 K.Comment: 4 pages, 5 figure
Low temperature series expansions for the square lattice Ising model with spin S > 1
We derive low-temperature series (in the variable )
for the spontaneous magnetisation, susceptibility and specific heat of the
spin- Ising model on the square lattice for , 2, , and
3. We determine the location of the physical critical point and non-physical
singularities. The number of non-physical singularities closer to the origin
than the physical critical point grows quite rapidly with . The critical
exponents at the singularities which are closest to the origin and for which we
have reasonably accurate estimates are independent of . Due to the many
non-physical singularities, the estimates for the physical critical point and
exponents are poor for higher values of , though consistent with
universality.Comment: 14 pages, LaTeX with IOP style files (ioplppt.sty), epic.sty and
eepic.sty. To appear in J. Phys.
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