13,581 research outputs found
Finite-size scaling and the deconfinement transition in gauge theories
We introduce a new method for determining the critical indices of the
deconfinement transition in gauge theories. The method is based on the finite
size scaling behavior of the expectation value of simple lattice operators,
such as the plaquette. We test the method for the case of SU(3) pure gauge
theory in (2+1) dimensions and obtain a precise determination of the critical
index , in agreement with the prediction of the Svetitsky-Yaffe
conjecture.Comment: 6 pages. Several comments and one reference added, results unchange
Influence of disordered porous media in the anomalous properties of a simple water model
The thermodynamic, dynamic and structural behavior of a water-like system
confined in a matrix is analyzed for increasing confining geometries. The
liquid is modeled by a two dimensional associating lattice gas model that
exhibits density and diffusion anomalies, in similarity to the anomalies
present in liquid water. The matrix is a triangular lattice in which fixed
obstacles impose restrictions to the occupation of the particles. We show that
obstacules shortens all lines, including the phase coexistence, the critical
and the anomalous lines. The inclusion of a very dense matrix not only suppress
the anomalies but also the liquid-liquid critical point
A lattice test of alternative interpretations of ``triviality'' in theory
There are two physically different interpretations of ``triviality'' in
theories. The conventional description predicts a
second-order phase transition and that the Higgs mass must vanish in the
continuum limit if , the physical v.e.v, is held fixed. An alternative
interpretation, based on the effective potential obtained in
``triviality-compatible'' approximations (in which the shifted `Higgs' field
is governed by an effective quadratic Hamiltonian)
predicts a phase transition that is very weakly first-order and that and
are both finite, cutoff-independent quantities. To test these two
alternatives, we have numerically computed the effective potential on the
lattice. Three different methods were used to determine the critical bare mass
for the chosen bare coupling value. All give excellent agreement with the
literature value. Two different methods for obtaining the effective potential
were used, as a control on the results. Our lattice data are fitted very well
by the predictions of the unconventional picture, but poorly by the
conventional picture.Comment: 16 pages, LaTeX, 2 eps figures (acknowledgements added in the
replaced version
Testicular endocrine activity is upregulated by D-Aspartic acid in the green frog Rana esculenta
This study investigated the involvement of D-aspartic acid (D-Asp) in testicular steroidogenesis of the green frog Rana esculenta and its effect on stimulation of thumb pad morphology and glandular activity, a typical testosterone-dependent secondary sexual characteristic in this amphibian species. In the testis, D-Asp concentrations vary significantly during the reproductive cycle: they are low in pre- and post-reproductive periods, but reach peak levels in the reproductive period (140-236 nmol/g wet tissue). Moreover, the concentrations of D-Asp in the testis through the sexual cycle positively match the testosterone levels in the gonad and the plasma. The racemase activity evaluated during the cycle expresses its peak when D-Asp and testosterone levels are highest, that is, during the reproductive period, confirming the synthesis of D-Asp from L-Asp by an aspartate racemase. Short-term in vivo experiments consisting of a single injection of D-Asp (2.0 micro mol/g body weight) demonstrated that this amino acid accumulates significantly in the testis, and after 3 h its uptake is coupled with a testosterone increase in both testis and plasma. Moreover, within 18 h of amino acid administration, the D-Asp concentration in the testis decreased along with the testosterone titer to prestimulation levels. Other amino acids (L-Asp, D-Glu and L-Glu) used instead of D-Asp were ineffective, confirming that the significant increase in testicular testosterone was a specific feature of this amino acid. In long-term experiments, D-Asp had been administered chronically to frogs caught during the three phases of the reproductive cycle, inducing testosterone increase and 17beta-estradiol decrease in the gonad during the pre- and post-reproductive period, and vice versa during the reproductive period
Comparison of the TaqMan and LightCycler systems in pharmacogenetic testing: evaluation of the CYP2C9*2/*3 polymorphisms.
Background: Pharmacogenetic testing for drugmetabolizing enzymes is not yet widely used in clinical practice. Methods: In an attempt to facilitate the application of this procedure, we have compared two real-time PCRbased methods, the TaqMan_ and the LightCycler_ for the pharmacogenetic evaluation of CYP2C9*2/*3 polymorphisms. Results and Conclusion: Both procedures are suitable for pharmacogenetic studies. The TaqMan procedure was less expensive in terms of cost per sample, but the TaqMan apparatus is more expensive than the LightCycler apparatus
The spectrum of screening masses near T_c: predictions from universality
We discuss the spectrum of screening masses in a pure gauge theory near the
deconfinement temperature from the point of view of the dimensionally reduced
model describing the spontaneous breaking of the center symmetry. Universality
arguments can be used to predict the values of the mass ratios in the scaling
region of the deconfined phase when the transition is of second order. One such
prediction is that the scalar sector of the screening spectrum in SU(2) pure
gauge theory contains a bound state of the fundamental excitation,
corresponding through universality to the bound state found in the 3D Ising
model and phi^4 theory in the broken symmetry phase. A Monte Carlo evaluation
of the screening masses in the gauge theory confirms the validity of the
prediction. We briefly discuss the possibility of using similar arguments for
first order deconfinement transitions, and in particular for the physically
relevant case of SU(3).Comment: 12 pages, 3 figures. Some changes in the discussion, added
references, results unchanged. Version to appear in Phys. Rev.
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