On the Universality Class of Monopole Percolation in Scalar QED

We study the critical properties of the monopole-percolation transition in U(1) lattice gauge theory coupled to scalars at infinite ($\beta=0$) gauge coupling. We find strong scaling corrections in the critical exponents that must be considered by means of an infinite-volume extrapolation. After the extrapolation, our results are as precise as the obtained for the four dimensional site-percolation and, contrary to previously stated, fully compatible with them.Comment: 11 pages, 3 figure

Finite Size Scaling and ``perfect'' actions: the three dimensional Ising model

Using Finite-Size Scaling techniques, we numerically show that the first irrelevant operator of the lattice $\lambda\phi^4$ theory in three dimensions is (within errors) completely decoupled at $\lambda=1.0$. This interesting result also holds in the Thermodynamical Limit, where the renormalized coupling constant shows an extraordinary reduction of the scaling-corrections when compared with the Ising model. It is argued that Finite-Size Scaling analysis can be a competitive method for finding improved actions.Comment: 13 pages, 3 figure

Palaeomicrobiology: application of ancient DNA sequencing to better understand bacterial genome evolution and adaptation

Next generation sequencing (NGS) has unlocked access to the wide range of non-cultivable microorganisms, including those present in the ancient past. The study of microorganisms from ancient sources (palaeomicrobiology) using DNA sequencing now provides a unique opportunity to examine ancient microbial genomic content, explore pathogenicity, and understand microbial evolution in greater detail than ever before. As a result, current studies have focused on reconstructing the evolutionary history of a number of human pathogens involved in ancient and historic pandemic events. These studies have opened the door for a variety of future palaeomicrobiology studies, which can focus on commensal microorganisms, species from non-human hosts, information from host-genomics, and the use of bacteria as proxies for additional information about past human health, behavior, migration, and culture. Here, we describe the origin and the historical and recent advances in the field of palaeomicrobiology, review some of the most notable ancient pathogenic microorganism studies, and provide perspectives on how NGS and whole genome information from ancient microorganisms contributes to our understanding of bacterial evolution on a broader scale. We conclude by exploring the application of newly developed tools in palaeomicrobiology and discussing how future studies can improve our current understanding of non-pathogenic microbes.Luis A. Arriola, Alan Cooper and Laura S. Weyric

Non-western celebrity politics and diplomacy: introduction

The origins of the specific project featured in this Cultural Report lie in a larger scale project funded by the Arts and Humanities Research Council and based at the White Rose East Asia Centre at the Universities of Leeds and Sheffield. The project set out to explore the influence and roles of a range of informal political actors such as former leaders, political spouses and 10 celebrity diplomats, to name but a few, across both the domestic and international levels of analysis in three regions of the world: East Asia, Russia and the Arab World

Chaos and Preheating

We show evidence for a relationship between chaos and parametric resonance both in a classical system and in the semiclassical process of particle creation. We apply our considerations in a toy model for preheating after inflation.Comment: 7 pages, 9 figures; uses epsfig and revtex v3.1. Matches version accepted for publication in Phys. Rev.

Relativistic nuclear structure effects in quasielastic neutrino scattering

Charged-current cross sections are calculated for quasielastic neutrino and antineutrino scattering using a relativistic meson-nucleon model. We examine how nuclear-structure effects, such as relativistic random-phase-approximation (RPA) corrections and momentum-dependent nucleon self-energies, influence the extraction of the axial form factor of the nucleon. RPA corrections are important only at low-momentum transfers. In contrast, the momentum dependence of the relativistic self-energies changes appreciably the value of the axial-mass parameter, $M_A$, extracted from dipole fits to the axial form factor. Using Brookhaven's experimental neutrino spectrum we estimate the sensitivity of M$_A$ to various relativistic nuclear-structure effects.Comment: 26 pages, revtex, 6 postscript figures (available upon request

Finite size effects on measures of critical exponents in d=3 O(N) models

We study the critical properties of three-dimensional O(N) models, for N=2,3,4. Parameterizing the leading corrections-to-scaling for the $\eta$ exponent, we obtain a reliable infinite volume extrapolation, incompatible with previous Monte Carlo values, but in agreement with $\epsilon$-expansions. We also measure the critical exponent related with the tensorial magnetization as well as the $\nu$ exponents and critical couplings.Comment: 12 pages, 2 postscript figure

Critical properties of the Antiferromagnetic \RP2$ model in three dimensions

We study the behavior of the antiferromagnetic RP$^2$ model in $d=3$. The vacuum structure is analyzed in the critical and low temperature regions, paying special attention to the spontaneous symmetry breaking pattern. Near the critical point we observe a full breakdown of the O(3) symmetry of the action. Several methods for computing critical exponents are compared. We conclude that the most solid determination is obtained using a measure of the correlation length. Corrections-to-scaling are parameterized, yielding a very accurate determination of the critical coupling and a 5\% error measure of the related exponent. This is used to estimate the systematic errors due to finite-size effects.Comment: 31 pages, 10 postscript figure

The four dimensional site-diluted Ising model: a finite-size scaling study

Using finite-size scaling techniques, we study the critical properties of the site-diluted Ising model in four dimensions. We carry out a high statistics Monte Carlo simulation for several values of the dilution. The results support the perturbative scenario: there is only the Ising fixed point with large logarithmic scaling corrections. We obtain, using the Perturbative Renormalization Group, functional forms for the scaling of several observables that are in agreement with the numerical data.Comment: 30 pages, 8 postscript figure

Hybrid Monte Carlo algorithm for the Double Exchange Model

The Hybrid Monte Carlo algorithm is adapted to the simulation of a system of classical degrees of freedom coupled to non self-interacting lattices fermions. The diagonalization of the Hamiltonian matrix is avoided by introducing a path-integral formulation of the problem, in $d+1$ Euclidean space-time. A perfect action formulation allows to work on the continuum euclidean time, without need for a Trotter-Suzuki extrapolation. To demonstrate the feasibility of the method we study the Double Exchange Model in three dimensions. The complexity of the algorithm grows only as the system volume, allowing to simulate in lattices as large as $16^3$ on a personal computer. We conclude that the second order paramagnetic-ferromagnetic phase transition of Double Exchange Materials close to half-filling belongs to the Universality Class of the three-dimensional classical Heisenberg model.Comment: 20 pages plus 4 postscript figure