A5004652381- Theoretical and Computational Physics
- Material Dynamics and Properties
- Stochastic processes and statistical mechanics
- Solid-state spectroscopy and crystallography
- Agriculture Sustainability and Environmental Impact
- Animal Genetics and Reproduction
- Physics of Superconductivity and Magnetism
- Interdisciplinary Research and Collaboration
- CRISPR and Genetic Engineering
- High-pressure geophysics and materials
- Genetically Modified Organisms Research
- Agricultural Innovations and Practices
- Quantum many-body systems
- Animal Disease Management and Epidemiology
- Pharmaceutical and Antibiotic Environmental Impacts
- Advanced NMR Techniques and Applications
- Spectroscopy and Quantum Chemical Studies
- Neural Networks and Applications
- Complex Systems and Time Series Analysis
- Genetic and phenotypic traits in livestock
- Phase Equilibria and Thermodynamics
- Ferroelectric and Piezoelectric Materials
- Statistical Mechanics and Entropy
- Animal Behavior and Welfare Studies
- Opinion Dynamics and Social Influence
University of Edinburgh
2015-2024
University of Bristol
2022
Centre Île-de-France - Versailles-Grignon
2022
Cardiff University
2022
Charles Sturt University
2022
Centre de Coopération Internationale en Recherche Agronomique pour le Développement
2022
University of Liverpool
2022
Qinetiq (United Kingdom)
2009
Roslin Institute
2007
Genomics (United Kingdom)
2007
Food system resilience has multiple dimensions. We draw on food and concepts review framings of different communities. present four questions to frame (Resilience what? Resilience from whose perspective? for how long?) three approaches enhancing (robustness, recovery, reorientation—the “Rs”). focus outcomes argue this will require actors adapting their activities, noting that activities do not change spontaneously but in response a drivers: an opportunity or threat. However, operationalizing...
We report an extensive Monte Carlo study of the density and energy fluctuations in a 2D Lennard-Jones fluid, within grand-canonical ensemble. The results are analyzed finite-size-scaling theory incorporating mixed character scaling fields that manifests particle-hole asymmetry. limiting critical distribution matches magnetization Ising model, illuminating configurational basis universality; corrections to behavior contain antisymmetric component which reflects operator, corroborating...
The authors develop a finite-size-scaling theory describing the joint density and energy fluctuations in near-critical fluid. As result of mixing temperature chemical potential two relevant scaling fields, operator features critical distribution as an antisymmetric correction to limiting scale-invariant form. Both form are predicted be functions that characteristic Ising universality class independently known. is tested with extensive Monte Carlo studies two-dimensional Lennard-Jones fluid,...
We present a method for the direct evaluation of difference between free energies two crystalline structures, different symmetry. The rests on Monte Carlo procedure which allows one to sample along path, through atomic-displacement-space, leading from structure other by way an intervening transformation that switches set lattice vectors another. configurations both structures can thus be sampled within single process, and their evaluated directly ratio measured probabilities each. is used...
For pt.II see ibid., vol.11, no.17, p.3591 (1978). The authors discussed the nature of excitation spectrum a structurally incommensurate phase, both when displacement field is describable by single Fourier component and it may be described in terms an array phase solitons. In each case they established character Goldstone mode, latter found additional whose properties merge into those mode commensurate structure as 'lock-in' boundary approached. They examined mode-acoustic interaction give...
For pt.I see ibid., vol.11, no.17, p.3578 (1978). The authors studied the behaviour of systems undergoing structural transformations between commensurate and incommensurate ordered phases. They reviewed theory developed by McMillan, Bak Emery (1976) in which order parameter for such phase transitions is visualised as a soliton density, give critique this theory. extended analysis to those cases where ordering characterised wavevector Lifschitz type, Brillouin zone corner. In both they found...
The authors examined the behaviour of a wide variety systems undergoing structural phase transitions to incommensurate with high-temperature structure. With aid renormalisation group methods they argued that, in cases examined, either critical is effectively that n=2 component Heisenberg model or transition first order.
We present a study of the multi-canonical Monte Carlo method which constructs and exploits procedures that sample across an extended space macrostates. examine strategies by sampling distribution can be constructed, showing, in particular, good approximation to this may generated efficiently exploiting measurements transition rate between macrostates, simulations launched from sub-dominant explore utility measurement absolute free energies, how it compares with traditional methods based on...
This paper describes a study of the behaviour 'block' coordinates, measuring spatial average, over block side L, local scalar ordering coordinates in system undergoing continuous phase transition. A general renormalisation group argument suggests that, limit which both L and xi (the correlation length) are large compared with lattice spacing, coordinate probability density function tends to universal form, Pinfinity dependent on ratio L/ . The is calculated explicitly for dimension d=1. It...
We describe a Monte Carlo procedure which allows sampling of the disjoint configuration spaces associated with crystalline and fluid phases, within single simulation. The method utilizes biased techniques to enhance probabilities gateway states (in each phase) are such that global switch (to other can be implemented. Equilibrium freezing-point parameters determined directly, statistical uncertainties prescribed transparently, finite-size effects quantified systematically. is potentially...
We develop the statistical mechanics formulation of image restoration problem, pioneered by Geman and (1984). Using Bayesian methods we establish posterior probability distribution for restored images, given data (corrupted image) prior (assumptions about source corruption process). In simplest cases, studied here, is controlled a cost function analagous to configurational energy an Ising model with local fields whose sense defined data. Through combination Monte Carlo simulation mean-field...
Reports acoustic-resonance measurements of the component s11 elastic compliance in SrTiO3 near its 105K phase transition. The observed critical singularity is stronger than that suggested by earlier using pulse-echo techniques, and predicted theory ideal crystal behaviour. These results are indicative a dynamic defect-controlled central-peak phenomenon.
Reports detailed experimental studies of the onset hard-mode Raman activity near cubic-tetragonal structural phase transitions in KMnF3 and RbCaF3. The results are discussed context a theory taking into account influence not only long-range order, reflected macroscopic order parameter, but also that precursor central peak phonon sideband soft-mode spectral function. dominant transition, is responsible for persistence quasi-first-order features above transition temperature. extent this used...
Renormalisation group methods are used to determine, second order in epsilon =4-d, the scaling function describing crossover from Gaussian Heisenberg behaviour susceptibility of an isotropic n-component spin system. The results conjunction with earlier Feynman graph calculation obtain O( 2) representation n-to-m-component function, and corresponding effective exponents, for anisotropic
An anharmonic model of strontium titanate has been developed which gives reasonable agreement with the temperature-dependent frequency and linewidth both zone-centre zone-corner soft modes. The is based upon harmonic models derived from results neutron inelastic scattering experiments, extended to include interactions short range. parameters were determined by constraining fit properties, for particularly simple expressions can be derived. Other effects then computed found give experiment....
We present a Monte Carlo method for the direct evaluation of difference between free energies two crystal structures. The is built on lattice-switch transformation that maps configuration one structure onto candidate other by `switching' set lattice vectors other, while keeping displacements with respect to sites constant. sampling displacement configurations biased, multicanonically, favor paths leading `gateway' arrangements which switch will be accepted. both structures can then...
Monte Carlo methods are used to explore the universal configurational structure of two-dimensional spin- 1/2, spin-1 and border- phi 4 models. Comparison 1/2 data provides evidence that magnetisation distribution (effectively Helmholtz free-energy function) its coupling derivative internal-energy constitute readily accessible signatures a universality class. It is shown that, when allowance made for relatively large corrections-to-scaling effects, behaviour model may be satisfactorily...
Monte Carlo methods have been used to analyse the critical behaviour of d=2 'border' phi 4 model which, according a recent series expansion study, violates expectations based upon universality. The results suggest that does, in fact, fall into Ising universality class, at least as regards those parameters which characterise point configurations ordering variable.
The critical properties of d dimensional systems with a quadratic anisotropic term in the Hamiltonian are investigated aid renormalization group analysis based upon Wilson perturbation expansion epsilon =4-d. For cubic nonzero four-spin coupling constant, u, it is found that asymptotic behaviour always one vanishing anisotropy. In lattice anisotropy simple argument leads to results agreement universality hypothesis.