40 research outputs found
Correlations in the Ising antiferromagnet on the anisotropic kagome lattice
We study the correlation function of middle spins, i. e. of spins on
intermediate sites between two adjacent parallel lattice axes, of the spatially
anisotropic Ising antiferromagnet on the kagome lattice. It is given rigorously
by a Toeplitz determinant. The large-distance behaviour of this correlation
function is obtained by analytic methods. For shorter distances we evaluate the
Toeplitz determinant numerically. The correlation function is found to vanish
exactly on a line J_d(T) in the T-J (temperature vs. coupling constant) phase
diagram. This disorder line divides the phase diagram into two regions. For J
less than J_d(T) the correlations display the features of an unfrustrated
two-dimensional Ising magnet, whereas for J greater than J_d(T) the
correlations between the middle spins are seen to be strongly influenced by the
short-range antiferromagnetic order that prevails among the spins of the
adjacent lattice axes. While for J less than J_d(T) there is a region with
ferrimagnetic long-range order, the model remains disordered for J greater than
J_d(T) down to T=0.Comment: 26 pages, 9 figures, published versio
Exact Curie temperature for the Ising model on Archimedean and Laves lattices
Using the Feynman-Vdovichenko combinatorial approach to the two dimensional
Ising model, we determine the exact Curie temperature for all two dimensional
Archimedean lattices. By means of duality, we extend our results to cover all
two dimensional Laves lattices. For those lattices where the exact critical
temperatures are not exactly known yet, we compare them with Monte Carlo
simulations.Comment: 10 pages, 1 figures, 3 table
The partition function of gauge supersymmetric Ising model on 3D regular lattice
The partition function (quantum transition amplitude) of the gauge system
with gauge group coupled with Majorana fermions is calculated on the
regular 3D cubic lattice.Comment: 35 pages, 7 figure
Modeling experimental glaucoma for screening studies of antiglaucomatous activity
The conducted studies of four models of glaucoma and their three modifications in animals made it possible to select two of them, which contributed to a stable and fairly long-term increase in IOP in rabbits (introduction of finely dispersed kaolin into the anterior chamber of the eye) and rats (adrenalineinduced model
Graphic tests usage as knowledge control method for medical universities students
Стаття присвячена сучасним педагогічним підходам у ВНЗ, використання
графічних тестів для навчання і контролю знань, що сприяють розвитку активних
форм мислення студентів-медиків.The article is devoted to modern pedagogical approaches at the university, the
usage of graphic tests for training and knowledge control, contributing to the
development of active forms of thinking of medical students
Statistical Mechanical Calculation of Anisotropic Step Stiffness of a Two-Dimensional Hexagonal Lattice Gas Model with Next-Nearest-Neighbor Interactions: Application to Si(111) Surface
We study a two-dimensional honeycomb lattice gas model with both nearest- and
next-nearest-neighbor interactions in a staggered field, which describes the
surface of stoichiometrically binary crystal.
We calculate anisotropic step tension, step stiffness, and equilibrium island
shape, by an extended random walk method. We apply the results to Si(111)
77 reconstructed surface and high-temperature Si(111) 11
surface. We also calculate inter-step interaction coefficient.Comment: revised on May 29 1999: RevTeX v3.1, 10 pages with 9 figures (one
figure added
Pharmacotherapy of glaucoma in terms of evidence-based medicine
Glaucoma is a disease associated with increased intraocular pressure (IOP). Of the pharmacological agents for treating glaucoma, there are drugs of the first (most effective and safe) and second-line treatment. First-line treatment includes prostaglandin analogs and beta-blockers. The currently used prostaglandin analogs (latanoprost, bimatoprost, tafluprost and travoprost) are PG F2α analogs that act through stimulation of FP receptors. They are distinguished by the optimal ratio of effectiveness and risk of side effects. They are convenient for the patient because for the therapeutic effect, it is enough to prescribe 1 time per day. As a result, it is rational to start the treatment of glaucoma with a drug in this group. In terms of pharmacoeconomics, the most affordable prostaglandin drug is latanoprost, which is generally as effective as other prostaglandin analogs. β-adrenergic blockers reduce the production of intraocular fluid, the formation of which is controlled by β1- and β2-adrenergic receptors. Therefore, non-selective β-blockers (timolol, levobunolol, metipranolol, and carteolol) have a pharmacodynamic advantage over selective β1-adrenergic antagonists (betaxolol). Conducted clinical studies of β-blockers have shown that given the cost, efficacy and safety, timolol was the most preferable treatment for glaucoma. In the presence of medical contraindications to the use of first-line drugs or to enhance their effectiveness, α2-agonists (apraclonidine and brimonidine), carbonic anhydrase inhibitors (usually local action: dorzolamide and brinzolamide), M-cholinomimetics (pilocarpine, carbachol and echothiopate), and also Rho-kinase inhibitors (ripasudil
Planar Graphical Models which are Easy
We describe a rich family of binary variables statistical mechanics models on
a given planar graph which are equivalent to Gaussian Grassmann Graphical
models (free fermions) defined on the same graph. Calculation of the partition
function (weighted counting) for such a model is easy (of polynomial
complexity) as reducible to evaluation of a Pfaffian of a matrix of size equal
to twice the number of edges in the graph. In particular, this approach touches
upon Holographic Algorithms of Valiant and utilizes the Gauge Transformations
discussed in our previous works.Comment: 27 pages, 11 figures; misprints correcte
Chromomagnetic Catalysis of Color Superconductivity in a (2+1)-dimensional NJL Model
The influence of a constant uniform external chromomagnetic field on the
formation of color superconductivity has been investigated. The consideration
was performed in the framework of a (2+1)-dimensional Nambu--Jona-Lasinio model
with two different four-fermionic structures responsible for condensates. In particular, it was shown that there exists a
critical value of the external chromomagnetic field such that at
a nonvanishing diquark condensate is dynamically created (the so-called
chromomagnetic catalysis effect of color superconductivity). Moreover, external
chromomagnetic fields may in some cases enhance the diquark condensate of color
superconductivity.Comment: 32 pages, 2 figures, revte
Magnetic Catalysis: A Review
We give an overview of the magnetic catalysis phenomenon. In the framework of
quantum field theory, magnetic catalysis is broadly defined as an enhancement
of dynamical symmetry breaking by an external magnetic field. We start from a
brief discussion of spontaneous symmetry breaking and the role of a magnetic
field in its a dynamics. This is followed by a detailed presentation of the
essential features of the phenomenon. In particular, we emphasize that the
dimensional reduction plays a profound role in the pairing dynamics in a
magnetic field. Using the general nature of underlying physics and its
robustness with respect to interaction types and model content, we argue that
magnetic catalysis is a universal and model-independent phenomenon. In support
of this claim, we show how magnetic catalysis is realized in various models
with short-range and long-range interactions. We argue that the general nature
of the phenomenon implies a wide range of potential applications: from certain
types of solid state systems to models in cosmology, particle and nuclear
physics. We finish the review with general remarks about magnetic catalysis and
an outlook for future research.Comment: 37 pages, to appear in Lect. Notes Phys. "Strongly interacting matter
in magnetic fields" (Springer), edited by D. Kharzeev, K. Landsteiner, A.
Schmitt, H.-U. Yee. Version 2: references adde