Search results for: Wolfhard Janke

Items from 1 to 20 out of 93 results

article

Monte Carlo Simulation of Long Hard‐Sphere Polymer Chains in Two to Five Dimensions

Stefan Schnabel, Wolfhard Janke

Macromolecular Theory and Simulations > 32 > 5 > n/a - n/a

Simulations are performed for long hard‐sphere polymer chains using a recently developed binary‐tree based Monte Carlo method. Systems in two to five dimensions with free and periodic boundary conditions and up to 10⁷ repeat units are considered. The analysis is focused on scaling properties of the end‐to‐end distance and the entropy and their dependence on the sphere diameter. To this end new methods...

article

GPU accelerated population annealing algorithm

Lev Yu. Barash, Martin Weigel, Michal Borovský, Wolfhard Janke, more

Computer Physics Communications > 2017 > 220 > C > 341-350

Population annealing is a promising recent approach for Monte Carlo simulations in statistical physics, in particular for the simulation of systems with complex free-energy landscapes. It is a hybrid method, combining importance sampling through Markov chains with elements of sequential Monte Carlo in the form of population control. While it appears to provide algorithmic capabilities for the simulation...

article

Dynamic greedy algorithms for the Edwards–Anderson model

Stefan Schnabel, Wolfhard Janke

Computer Physics Communications > 2017 > 220 > C > 74-80

To provide a novel tool for the investigation of the energy landscape of the Edwards–Anderson spin-glass model we introduce an algorithm that allows an efficient execution of a greedy optimization based on data from a previously performed optimization for a similar configuration. As an application we show how the technique can be used to perform higher-order greedy optimizations and simulated annealing...

article

Convergence of Stochastic Approximation Monte Carlo and modified Wang–Landau algorithms: Tests for the Ising model

Simon Schneider, Marco Mueller, Wolfhard Janke

Computer Physics Communications > 2017 > 216 > C > 1-7

We investigate the behavior of the deviation of the estimator for the density of states (DOS) with respect to the exact solution in the course of Wang–Landau and Stochastic Approximation Monte Carlo (SAMC) simulations of the two-dimensional Ising model. We find that the deviation saturates in the Wang–Landau case. This can be cured by adjusting the refinement scheme. To this end, the 1 ∕ t -modification...

article

Scaling and universality in the phase diagram of the 2D Blume-Capel model

Johannes Zierenberg, Nikolaos G. Fytas, Martin Weigel, Wolfhard Janke, more

The European Physical Journal Special Topics > 2017 > 226 > 4 > 789-804

We review the pertinent features of the phase diagram of the zero-field Blume-Capel model, focusing on the aspects of transition order, finite-size scaling and universality. In particular, we employ a range of Monte Carlo simulation methods to study the 2D spin-1 Blume-Capel model on the square lattice to investigate the behavior in the vicinity of the first-order and second-order regimes of the ferromagnet-paramagnet...

article

Plaquette Ising models, degeneracy and scaling

Desmond A. Johnston, Marco Mueller, Wolfhard Janke

The European Physical Journal Special Topics > 2017 > 226 > 4 > 749-764

We review some recent investigations of the 3d plaquette Ising model. This displays a strong first-order phase transition with unusual scaling properties due to the size-dependent degeneracy of the low-temperature phase. In particular, the leading scaling correction is modified from the usual inverse volume behaviour ∝ 1/L³ to 1/L². The degeneracy also has implications for the magnetic order in the...

article

Exploring first-order phase transitions with population annealing

Lev Yu. Barash, Martin Weigel, Lev N. Shchur, Wolfhard Janke

The European Physical Journal Special Topics > 2017 > 226 > 4 > 595-604

Population annealing is a hybrid of sequential and Markov chain Monte Carlo methods geared towards the efficient parallel simulation of systems with complex free-energy landscapes. Systems with first-order phase transitions are among the problems in computational physics that are difficult to tackle with standard methods such as local-update simulations in the canonical ensemble, for example with...

article

Effect of grafting on the binding transition of two flexible polymers

Johannes Zierenberg, Katharina Tholen, Wolfhard Janke

The European Physical Journal Special Topics > 2017 > 226 > 4 > 683-692

We investigate the binding transition of two flexible polymers grafted to a steric surface with closeby end points. While free polymers show a discontinuous transition, grafting to a steric flat surface leads to a continuous binding transition. This is supported by results from Metropolis and parallel multicanonical simulations. A combination of canonical and microcanonical analyses reveals that the...

article

Single-chain behavior of poly(3-hexylthiophene)

Momchil Ivanov, Jonathan Gross, Wolfhard Janke

The European Physical Journal Special Topics > 2017 > 226 > 4 > 667-681

Poly(3-hexylthiophene) (P3HT) has been in the focus of recent studies due to its promising future use in organic photovoltaics, electronics and photonics. Recent publications investigate the melt behavior of P3HT, its interaction with other molecules, mainly various fullerene derivates, and isolated chains interacting with substrates. In this work we lay the focus on the single-chain properties of...

article

Exact solutions to plaquette Ising models with free and periodic boundaries

Marco Mueller, Desmond A. Johnston, Wolfhard Janke

Nuclear Physics B > 2017 > 914 > C > 388-404

An anisotropic limit of the 3d plaquette Ising model, in which the plaquette couplings in one direction were set to zero, was solved for free boundary conditions by Suzuki (1972) [1], who later dubbed it the fuki-nuke, or “no-ceiling”, model. Defining new spin variables as the product of nearest-neighbour spins transforms the Hamiltonian into that of a stack of (standard) 2d Ising models and reveals...

chapter

Rugged Free-Energy Landscapes – An Introduction

Wolfhard Janke

Lecture Notes in Physics > Rugged Free Energy Landscapes > Rugged Free-Energy Landscapes – An Introduction > 1-7

chapter

Monte Carlo Methods in Classical Statistical Physics

Wolfhard Janke

Lecture Notes in Physics > Computational Many-Particle Physics > Classical Monte Carlo > 79-140

chapter

Quantum Gravity with Matter Fields in Two Dimensions

Elmar Bittner, Wolfhard Janke, Harald Markum, Jürgen Riedler

Lecture Notes in Physics > Geometry and Quantum Physics > 383-383

Spin systems coupled to two-dimensional manifolds are studied as a simple example for matter fields coupled to gravity. We consider two versions of quantum Regge calculus. The Standard Regge Calculus [1] where the quadratic link lengths q of the simplicial manifold vary continuously and the Discrete Regge Model [2] where they are restricted to two possible values. These manifolds are coupled with...

chapter

Thermodynamics of Protein Folding from Coarse-Grained Models’ Perspectives

Michael Bachmann, Wolfhard Janke

Lecture Notes in Physics > Rugged Free Energy Landscapes > Protein Folding > 203-246

Folding and aggregation of proteins, the interaction between proteins and membranes, as well as the adsorption of organic soft matter to inorganic solid substrates belong to the most interesting challenges in understanding structure and function of complex macromolecules. This is reasoned by the interdisciplinary character of the associated questions ranging from the molecular origin of the loss of...

book

Rugged Free Energy Landscapes

Wolfhard Janke

Lecture Notes in Physics

This collection of lectures and tutorial reviews by renowned experts focusses on the common computational approaches in use to unravel the static and dynamical behaviour of complex physical systems at the interface of physics, chemistry and biology. Paradigmatic examples of condensed matter physics are spin and structural glasses and protein folding, as well as their aggregation and adsorption to...

chapter

Monte Carlo Studies of Connectivity Disorder

Wolfhard Janke, Martin Weigel

High Performance Computing in Science and Engineering, Munich 2004 > Solid-State Physics > 363-373

article

Planar ordering in the plaquette-only gonihedric Ising model

Marco Mueller, Wolfhard Janke, Desmond A. Johnston

Nuclear Physics, Section B > 2015 > 894 > Complete > 1-14

In this paper we conduct a careful multicanonical simulation of the isotropic 3d plaquette (“gonihedric”) Ising model and confirm that a planar, fuki-nuke type order characterises the low-temperature phase of the model. From consideration of the anisotropic limit of the model we define a class of order parameters which can distinguish the low- and high-temperature phases in both the anisotropic and...

article

Probing the Effect of Density on the Aggregation Temperature of Semi-flexible Polymers in Spherical Confinement

Marco Mueller, Johannes Zierenberg, Martin Marenz, Philipp Schierz, more

Physics Procedia > 2015 > 68 > Complete > 95-99

Applying parallel multicanonical simulations, we study the aggregation transition of finite semi-flexible polymers in dependence on the density, where we keep the polymer length fixed as a chemical property. A spherical confinement is imposed to constrain the translational entropy. We show that the competition between single-polymer collapse and many-polymer aggregation yields a lower temperature...

article

Computer Simulation Studies of Polymer Adsorption and Aggregation – From Flexible to Stiff

Wolfhard Janke

Physics Procedia > 2015 > 68 > Complete > 69-79

This mini-review gives a brief overview of our recent Monte Carlo computer simulations of polymer adsorption and aggregation based on coarse-grained continuum models of theta polymers focusing on excluded volume, short-range attraction and bending stiffness. The simulations are performed in generalized ensembles (multicanonical and parallel tempering) and analyzed with canonical and microcanonical...

article

Multicanonical analysis of the plaquette-only gonihedric Ising model and its dual

Marco Mueller, Desmond A. Johnston, Wolfhard Janke

Nuclear Physics B > 2014 > 888 > C > 214-235

The three-dimensional purely plaquette gonihedric Ising model and its dual are investigated to resolve inconsistencies in the literature for the values of the inverse transition temperature of the very strong temperature-driven first-order phase transition that is apparent in the system. Multicanonical simulations of this model allow us to measure system configurations that are suppressed by more...

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INFONA - science communication portal

Search results for: Wolfhard Janke

Monte Carlo Simulation of Long Hard‐Sphere Polymer Chains in Two to Five Dimensions

GPU accelerated population annealing algorithm

Dynamic greedy algorithms for the Edwards–Anderson model

Convergence of Stochastic Approximation Monte Carlo and modified Wang–Landau algorithms: Tests for the Ising model

Scaling and universality in the phase diagram of the 2D Blume-Capel model

Plaquette Ising models, degeneracy and scaling

Exploring first-order phase transitions with population annealing

Effect of grafting on the binding transition of two flexible polymers

Single-chain behavior of poly(3-hexylthiophene)

Exact solutions to plaquette Ising models with free and periodic boundaries

Rugged Free-Energy Landscapes – An Introduction

Monte Carlo Methods in Classical Statistical Physics

Quantum Gravity with Matter Fields in Two Dimensions

Thermodynamics of Protein Folding from Coarse-Grained Models’ Perspectives

Rugged Free Energy Landscapes

Monte Carlo Studies of Connectivity Disorder

Planar ordering in the plaquette-only gonihedric Ising model

Probing the Effect of Density on the Aggregation Temperature of Semi-flexible Polymers in Spherical Confinement

Computer Simulation Studies of Polymer Adsorption and Aggregation – From Flexible to Stiff

Multicanonical analysis of the plaquette-only gonihedric Ising model and its dual

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