Critical properties of the four-state Commutative Random Permutation Glassy Potts model in three and four dimensions

We investigate the critical properties of the four-state commutative random permutation glassy Potts model in three and four dimensions by means of Monte Carlo simulation and of a finite size scaling analysis. Thanks to the use of a field programmable gate array we have been able to thermalize a large number of samples of systems with large volume. This has allowed us to observe a spin-glass ordered phase in d=4 and to study the critical properties of the transition. In d=3, our results are consistent with the presence of a Kosterlitz-Thouless transition, but we cannot exclude transient effects due to a value of the lower critical dimension slightly below 3.Comment: 9 pages, 8 Postscript figure

An in-depth view of the microscopic dynamics of Ising spin glasses at fixed temperature

Using the dedicated computer Janus, we follow the nonequilibrium dynamics of the Ising spin glass in three dimensions for eleven orders of magnitude. The use of integral estimators for the coherence and correlation lengths allows us to study dynamic heterogeneities and the presence of a replicon mode and to obtain safe bounds on the Edwards-Anderson order parameter below the critical temperature. We obtain good agreement with experimental determinations of the temperature-dependent decay exponents for the thermoremanent magnetization. This magnitude is observed to scale with the much harder to measure coherence length, a potentially useful result for experimentalists. The exponents for energy relaxation display a linear dependence on temperature and reasonable extrapolations to the critical point. We conclude examining the time growth of the coherence length, with a comparison of critical and activated dynamics.Comment: 38 pages, 26 figure

Ianus: an Adpative FPGA Computer

Dedicated machines designed for specific computational algorithms can outperform conventional computers by several orders of magnitude. In this note we describe {\it Ianus}, a new generation FPGA based machine and its basic features: hardware integration and wide reprogrammability. Our goal is to build a machine that can fully exploit the performance potential of new generation FPGA devices. We also plan a software platform which simplifies its programming, in order to extend its intended range of application to a wide class of interesting and computationally demanding problems. The decision to develop a dedicated processor is a complex one, involving careful assessment of its performance lead, during its expected lifetime, over traditional computers, taking into account their performance increase, as predicted by Moore's law. We discuss this point in detail

The Spin Glass Phase in the Four-State, Three-Dimensional Potts Model

We perform numerical simulations, including parallel tempering, on the Potts glass model with binary random quenched couplings using the JANUS application-oriented computer. We find and characterize a glassy transition, estimating the location of the transition and the value of the critical exponents. We show that there is no ferromagnetic transition in a large temperature range around the glassy critical temperature. We also compare our results with those obtained recently on the "random permutation" Potts glass.Comment: 7 pages and 3 figures. Corrected minor typo

Simulating spin systems on IANUS, an FPGA-based computer

We describe the hardwired implementation of algorithms for Monte Carlo simulations of a large class of spin models. We have implemented these algorithms as VHDL codes and we have mapped them onto a dedicated processor based on a large FPGA device. The measured performance on one such processor is comparable to O(100) carefully programmed high-end PCs: it turns out to be even better for some selected spin models. We describe here codes that we are currently executing on the IANUS massively parallel FPGA-based system.Comment: 19 pages, 8 figures; submitted to Computer Physics Communication

Nonequilibrium spin glass dynamics from picoseconds to 0.1 seconds

We study numerically the nonequilibrium dynamics of the Ising Spin Glass, for a time that spans eleven orders of magnitude, thus approaching the experimentally relevant scale (i.e. {\em seconds}). We introduce novel analysis techniques that allow to compute the coherence length in a model-independent way. Besides, we present strong evidence for a replicon correlator and for overlap equivalence. The emerging picture is compatible with non-coarsening behavior.Comment: 4 pages, 4 eps color figures. Version accepted for publication in Phys. Rev. Let

Neuer Kopf, alte Ideen? : "Normalisierung" des Front National unter Marine Le Pen

In this article, it is investigated whether vibrational entropy (VE) is an important contribution to the free energy of globular proteins at ambient conditions. VE represents the major configurational-entropy contribution of these proteins. By definition, it is an average of the configurational entropies of the protein within single minima of the energy landscape, weighted by their occupation probabilities. Its large part originates from thermal motion of flexible torsion angles giving rise to the finite peak widths observed in torsion angle distributions. While VE may affect the equilibrium properties of proteins, it is usually neglected in numerical calculations as its consideration is difficult. Moreover, it is sometimes believed that all well-packed conformations of a globular protein have similar VE anyway. Here, we measure explicitly the VE for six different conformations from simulation data of a test protein. Estimates are obtained using the quasi-harmonic approximation for three coordinate sets, Cartesian, bond-angle-torsion (BAT), and a new set termed rotamer-degeneracy lifted BAT coordinates by us. The new set gives improved estimates as it overcomes a known shortcoming of the quasi-harmonic approximation caused by multiply populated rotamer states, and it may serve for VE estimation of macromolecules in a very general context. The obtained VE values depend considerably on the type of coordinates used. However, for all coordinate sets we find large entropy differences between the conformations, of the order of the overall stability of the protein. This result may have important implications on the choice of free energy expressions used in software for protein structure prediction, protein design, and NMR refinement

"Feed my lambs" : the spiritual direction ministry of Calvinistic British Baptist Anne Dutton during the early years of the evangelical revival.

This dissertation contends that Anne Dutton (1692-1765) contributed a transatlantic ministry of spiritual direction to the Evangelical Revival in the early 1740s. The first chapter provides a historiographical review of Dutton's reception in the eighteenth and nineteenth centuries and the state of contemporary scholarship of Dutton. The chapter concludes with a historical reflection on spiritual direction, situating Dutton in the tradition of Protestant epistolary spiritual counseling and the long history of women spiritual directors. Chapter two provides an analysis of Dutton's early life in light of the autobiographies of Anne and her husband, Benjamin Dutton. The third chapter demonstrates that Anne Dutton's early literary productions were grounded in the spiritual formation she received in High Calvinistic congregations that encouraged experiential biblicism and Puritan spirituality. Of particular influence upon Dutton was the Puritan Thomas Goodwin with his interpretations of the "ages of Christianity" and the "sealing of the Spirit." Chapter four reconstructs Dutton's early correspondence with Howell Harris, John Wesley, and George Whitefield. The chapter demonstrates that Dutton's Calvinistic spiritual writings were attractive to Harris and Whitefield (who in turn expanded her social-spiritual direction network) and suggests Dutton's direction to these men is best defined as spiritual confirmation. The fifth chapter examines Dutton's presence in the first evangelical magazine, the London Weekly Papers, as the anonymous "Friend in the Country." Published by Dutton's correspondent John Lewis, the magazine included several of Dutton's spiritual pieces and advertised a number of her published works. Dutton's contributions to this publication demonstrate her usefulness to Calvinistic Methodism and the extensiveness of her influence, albeit anonymous, on readers in England, Scotland, and America. Chapter six analyzes Dutton's Letter-Books published in the 1740s. These volumes exhibit her transatlantic influence and the defining elements of her personal spiritual direction. The Letter-Books reveal Dutton's correspondents relating to her as a spiritual director: one who was holy, knowledgeable, compassionate, wise, and discerning. The chapter concludes suggesting Dutton's Letter-Books reflect the expansion and contraction of Dutton's influence in the Evangelical Revival. A final chapter summarizes the contributions of this project to the study of Anne Dutton's life, spirituality, and ministry.by Michael D. Sciretti, Jr.Ph.D