4,919 research outputs found

    Smooth Random Surfaces from Tight Immersions?

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    We investigate actions for dynamically triangulated random surfaces that consist of a gaussian or area term plus the {\it modulus} of the gaussian curvature and compare their behavior with both gaussian plus extrinsic curvature and ``Steiner'' actions.Comment: 7 page

    An Effective Model for Crumpling in Two Dimensions?

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    We investigate the crumpling transition for a dynamically triangulated random surface embedded in two dimensions using an effective model in which the disordering effect of the XX variables on the correlations of the normals is replaced by a long-range ``antiferromagnetic'' term. We compare the results from a Monte Carlo simulation with those obtained for the standard action which retains the XX's and discuss the nature of the phase transition.Comment: 5 page

    Cluster variation - Pade` approximants method for the simple cubic Ising model

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    The cluster variation - Pade` approximant method is a recently proposed tool, based on the extrapolation of low/high temperature results obtained with the cluster variation method, for the determination of critical parameters in Ising-like models. Here the method is applied to the three-dimensional simple cubic Ising model, and new results, obtained with an 18-site basic cluster, are reported. Other techniques for extracting non-classical critical exponents are also applied and their results compared with those by the cluster variation - Pade` approximant method.Comment: 8 RevTeX pages, 3 PostScript figure

    Beam spin asymmetries in deeply virtual Compton scattering (DVCS) with CLAS at 4.8 GeV

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    We report measurements of the beam spin asymmetry in deeply virtual Compton scattering (DVCS) at an electron beam energy of 4.8 GeV using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The DVCS beam spin asymmetry has been measured in a wide range of kinematics, 1.0 \u3c Q(2) \u3c 2.8 (GeV/c)(2), 0.12 \u3c x(B) \u3c 0.48, and 0.1 \u3c -t \u3c 0.8 (GeV/c)(2), using the reaction (e) over right arrow - \u3e e\u27pX. The number of H(e, e\u27gamma p) and H(e, e\u27pi(0)p) events are separated in each (Q(2), x(B), t) bin by a fit to the line shape of the H(e, e\u27p) X M(x)(2) distribution. The validity of the method was studied in detail using experimental and simulated data. It was shown that with the achieved missing mass squared resolution and the available statistics, the separation of DVCS-Bethe-Heitler and pi(0) events can reliably be done with less than 5% uncertainty. Also, the Q(2) and t dependences of the sin phi moments of the asymmetry are extracted and compared with theoretical calculations

    Quenched Random Graphs

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    Spin models on quenched random graphs are related to many important optimization problems. We give a new derivation of their mean-field equations that elucidates the role of the natural order parameter in these models.Comment: 9 pages, report CPTH-A264.109

    Dynamic Critical Behavior of the Swendsen-Wang Algorithm: The Two-Dimensional 3-State Potts Model Revisited

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    We have performed a high-precision Monte Carlo study of the dynamic critical behavior of the Swendsen-Wang algorithm for the two-dimensional 3-state Potts model. We find that the Li-Sokal bound (τint,Econst×CH\tau_{int,E} \geq const \times C_H) is almost but not quite sharp. The ratio τint,E/CH\tau_{int,E} / C_H seems to diverge either as a small power (0.08\approx 0.08) or as a logarithm.Comment: 35 pages including 3 figures. Self-unpacking file containing the LaTeX file, the needed macros (epsf.sty, indent.sty, subeqnarray.sty, and eqsection.sty) and the 3 Postscript figures. Revised version fixes a normalization error in \xi (with many thanks to Wolfhard Janke for finding the error!). To be published in J. Stat. Phys. 87, no. 1/2 (April 1997

    Monte Carlo Renormalization of the 3-D Ising model: Analyticity and Convergence

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    We review the assumptions on which the Monte Carlo renormalization technique is based, in particular the analyticity of the block spin transformations. On this basis, we select an optimized Kadanoff blocking rule in combination with the simulation of a d=3 Ising model with reduced corrections to scaling. This is achieved by including interactions with second and third neighbors. As a consequence of the improved analyticity properties, this Monte Carlo renormalization method yields a fast convergence and a high accuracy. The results for the critical exponents are y_H=2.481(1) and y_T=1.585(3).Comment: RevTeX, 4 PostScript file

    On the Stability of the Mean-Field Glass Broken Phase under Non-Hamiltonian Perturbations

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    We study the dynamics of the SK model modified by a small non-hamiltonian perturbation. We study aging, and we find that on the time scales investigated by our numerical simulations it survives a small perturbation (and is destroyed by a large one). If we assume we are observing a transient behavior the scaling of correlation times versus the asymmetry strength is not compatible with the one expected for the spherical model. We discuss the slow power law decay of observable quantities to equilibrium, and we show that for small perturbations power like decay is preserved. We also discuss the asymptotically large time region on small lattices.Comment: 34 page
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