arXiv subjects

Andreas Heuer

Publications and source records attributed to Andreas Heuer.

At least 73 records · Page 4Linked to original sources

arXiv2012

How does the past of a soccer match influence its future?

Scoring goals in a soccer match can be interpreted as a stochastic process. In the most simple description of a soccer match one assumes that scoring goals can be described by a constant goal rate for each team, implying simple Poissonian and Markovian behavior. Here a general framework for the identification of deviations from this behavior is presented. For this endeavor it is essential to formulate an a priori estimate of the expected number of goals per team in a specific match. The analysis scheme is applied to approximately 40 seasons of the German Bundesliga. It is possible to characterize the impact of the previous course of the match on the present match behavior. This allows one to identify interesting generic features about soccer matches and thus to learn about the hidden complexities behind scoring goals.

physics.data-an↗

arXiv2012

A statistical view on team handball results: home advantage, team fitness and prediction of match outcomes

We analyze the results of the German Team Handball Bundesliga for ten seasons in a model-free statistical time series approach. We will show that the home advantage is nearly negligible compared to the total sum of goals. Specific interest has been spent on the time evolution of the team fitness expressed in terms of the goal difference. In contrast to soccer, our results indicate a decay of the team fitness values over a season while the long time correlation behavior over years is nearly comparable. We are able to explain the dominance of a few teams by the large value for the total number of goals in a match. A method for the prediction of match winners is presented in good accuracy with the real results. We analyze the properties of promoted teams and indicate drastic level changes between the Bundesliga and the second league. Our findings reflect in good agreement recent discussions on modern successful attack strategies.

stat.OT↗

arXiv2011

Macromolecular unfolding properties in presence of compatible solutes

We present Molecular Dynamics simulations of Chymotrypsin inhibitor II and PEO in presence of compatible solutes. Our results indicate that the the native compact state of the studied macromolecules is stabilized in presence of hydroxyectoine. We are able to explain the corresponding mechanism by a variation of the solvent properties for higher hydroxyectoine concentrations. Our results are validated by detailed free energy calculations.

physics.bio-ph↗

arXiv2011

Hidden complexities in the unfolding mechanism of a cytosine-rich DNA strand

We investigate the unfolding pathway of a cytosine-rich DNA hairpin structure via Molecular Dynamics simulations. Our results indicate a hidden complexity present in the unfolding process. W e show that this complex behavior arises due to non-stochastic contributions which have an important impact on the description of the dynamics in terms of collective variables.

cond-mat.soft↗

arXiv2011

Properties of compatible solutes in aqueous solution

We have performed Molecular Dynamics simulations of ectoine, hydroxyectoine and urea in explicit solvent. Special attention has been spent on the local surrounding structure of water molecules. Our results indicate that ectoine and hydroxyectoine are able to accumulate more water molecules than urea by a pronounced ordering due to hydrogen bonds. We have validated that the charging of the molecules is of main importance resulting in a well defined hydration sphere. The influence of a varying salt concentration is also investigated. Finally we present experimental results of a DPPC monolayer phase transition that validate our numerical findings.

cond-mat.soft↗

arXiv2011

Unfolding mechanism and the free energy landscape of a single stranded DNA i-motif

We present Molecular Dynamics simulations of a single stranded unprotonated DNA i-motif in explicit solvent. Our results indicate that the native structure in non-acidic solution at 300 K is unstable and completely vanishes on a time scale up to 10 ns. Two unfolding mechanisms with decreasing connectivity between the initially interacting nucleobases can be identified where one pathway is characterized as entropically more favorable. The entropic preference can be mainly explained by strong water ordering effects due to hydrogen bonds for several occurring structures along the pathways. Finally we are able to indicate via free energy calculations the most stable configurations belonging to distinct hairpin structures in good agreement to experimental results.

physics.bio-ph↗

arXiv2011

High temperature unfolding simulations of a single stranded DNA i-motif

We present the results of high temperature 500 K Molecular Dynamics simulations of the DNA i-motif. The essential dynamics and the main unfolding pathways are compared to a biased metadynamics simulation at 300 K. Our results indicate a remarkable agreement of the concerted motion at both temperatures. The transition can be described by a few number of eigenvectors indicating a simple unfolding process. Two main mechanisms for the unfolding pathway at 500 K can be detected which are in good agreement to the results of the biased simulation at 300 K.

physics.bio-ph↗

arXiv2011

Calculation of free energy landscapes: A Histogram Reweighted Metadynamics approach

We present an efficient method for the calculation of free energy landscapes. Our approach involves a history dependent bias potential which is evaluated on a grid. The corresponding free energy landscape is constructed via a histogram reweighting procedure a posteriori. Due to the presence of the bias potential, it can be also used to accelerate rare events. In addition, the calculated free energy landscape is not restricted to the actual choice of collective variables and can in principle be extended to auxiliary variables of interest without further numerical effort. The applicability is shown for several examples. We present numerical results for the alanine dipeptide and the Met-Enkephalin in explicit solution to illustrate our approach. Furthermore we derive an empirical formula that allows the prediction of the computational cost for the ordinary metadynamics variant in comparison to our approach which is validated by a dimensionless representation.

physics.comp-ph↗

arXiv2011

Memory effects in the relaxation of the Gaussian trap model

We investigate the memory effect in a simple model for glassy relaxation, a trap model with a Gaussian density of states. In this model thermal equilibrium is reached at all finite temperatures and therefore we can consider jumps from low to high temperatures in addition to the quenches usually considered in aging studies. We show that the evolution of the energy following the Kovacs-protocol can approximately be expressed as a difference of two monotonously decaying functions and thus show the existence of a so-called Kovacs hump whenever these functions are not single exponentials. It is well established that the Kovacs effect also occurs in the linear response regime and we show that most of the gross features do not change dramatically when large temperature jumps are considered. However, there is one distinguishing feature that only exists beyond the linear regime which we discuss in detail. For the memory experiment with 'inverted' temperatures, i.e. jumping up and then down again, we find a very similar behavior apart from an opposite sign of the hump.

cond-mat.soft↗

arXiv2010

Characterization of local dynamics and mobilities in polymer melts - a simulation study

The local dynamical features of a PEO melt studied by MD simulations are compared to two model chain systems, namely the well-known Rouse model as well as the semiflexible chain model (SFCM) that additionally incorporates chain stiffness. Apart from the analysis of rather general quantities such as the mean square displacement (MSD), we present a new statistical method to extract the local bead mobility from the simulation data on the basis of the Langevin equation, thus providing a complementary approach to the classical Rouse-mode analysis. This allows us to check the validity of the Langevin equation and, as a consequence, the Rouse model. Moreover, the new method has a broad range of applications for the analysis of the dynamics of more complex polymeric systems like comb-branched polymers or polymer blends.

cond-mat.soft↗

arXiv2010

Continuous Markovian model for Levy random walks with superdiffusive and superballistic regimes

We consider a previously devised model describing Levy random walks (Phys. Rev E 79, 011110; 80, 031148, (2009)). It is demonstrated numerically that the given model describes Levy random walks with superdiffusive, ballistic, as well as superballistic dynamics. Previously only the superdiffusive regime has been analyzed. In this model the walker velocity is governed by a nonlinear Langevin equation. Analyzing the crossover from small to large time scales we find the time scales on which the velocity correlations decay and the walker motion essentially exhibits Levy statistics. Our analysis is based on the analysis of the geometric means of walker displacements and allows us to tackle probability density functions with power-law tails and, correspondingly, divergent moments.

cond-mat.stat-mech↗

arXiv2010

Aging effects manifested in the potential energy landscape of a model glass former

We present molecular dynamics simulations of a model glass-forming liquid (the binary Kob-Anderson Lennard-Jones model) and consider the distributions of inherent energies and metabasins during aging. In addition to the typical protocol of performing a temperature jump from a high temperature to a low destination temperature, we consider the temporal evolution of the distributions after an 'up-jump', i.e. from a low to a high temperature. In this case the distribution of megabasin energies exhibits a transient two-peak structure. Our results can qualitatively be rationalized in terms of a trap model with a Gaussian distribution of trap energies. The analysis is performed for different system sizes. A detailed comparison with the trap model is possible only for a small system because of major averging effects for larger systems.

cond-mat.dis-nn↗

arXiv2010

Soccer: is scoring goals a predictable Poissonian process?

The non-scientific event of a soccer match is analysed on a strictly scientific level. The analysis is based on the recently introduced concept of a team fitness (Eur. Phys. J. B 67, 445, 2009) and requires the use of finite-size scaling. A uniquely defined function is derived which quantitatively predicts the expected average outcome of a soccer match in terms of the fitness of both teams. It is checked whether temporary fitness fluctuations of a team hamper the predictability of a soccer match. To a very good approximation scoring goals during a match can be characterized as independent Poissonian processes with pre-determined expectation values. Minor correlations give rise to an increase of the number of draws. The non-Poissonian overall goal distribution is just a consequence of the fitness distribution among different teams. The limits of predictability of soccer matches are quantified. Our model-free classification of the underlying ingredients determining the outcome of soccer matches can be generalized to different types of sports events.

physics.data-an↗

arXiv2009

Continuous time multidimensional Markovian description of Levy walks

The paper presents a multidimensional model for nonlinear Markovian random walks that generalizes one we developed previously (Phys. Rev. E v.79, 011110, 2009) in order to describe the Levy type stochastic processes in terms of continuous trajectories of walker motion. This approach may open a way to treat Levy flights or Levy random walks in inhomogeneous media or systems with boundaries in the future. The proposed model assumes the velocity of a wandering particle to be affected by a linear friction and a nonlinear Langevin force whose intensity is proportional to the magnitude of the velocity for its large values. Based on the singular perturbation technique the corresponding Fokker-Planck equation is analyzed and the relationship between the system parameters and the Levy exponent is found. Following actually the previous paper we demonstrate also that anomalously long displacements of the wandering particle are caused by extremely large fluctuations in the particle velocity whose duration is determined by the system parameters rather than the duration of the observation interval. In this way we overcome the problem of ascribing to Levy random walks non-Markov properties.

cond-mat.stat-mech↗

arXiv2009

Fitness, chance, and myths: an objective view on soccer results

We analyze the time series of soccer matches in a model-free way using data for the German soccer league (Bundesliga). We argue that the goal difference is a better measure for the overall fitness of a team than the number of points. It is shown that the time evolution of the table during a season can be interpreted as a random walk with an underlying constant drift. Variations of the overall fitness mainly occur during the summer break but not during a season. The fitness correlation shows a long-time decay on the scale of a quarter century. Some typical soccer myths are analyzed in detail. It is shown that losing but no winning streaks exist. For this analysis ideas from multidimensional NMR experiments have been borrowed. Furthermore, beyond the general home advantage there is no statistically relevant indication of a team-specific home fitness. Based on these insights a framework for a statistical characterization of the results of a soccer league is introduced and some general consequences for the prediction of soccer results are formulated.

physics.data-an↗

arXiv2009

Dynamic effects on the loss of control in template-directed nucleation

Full nucleation control for deposited functional molecules on pre-patterned surfaces is of major technological relevance. To understand the nucleation behavior we combine the numerical solution for the evolution of the adatom concentration with standard nucleation theory. From the qualitative change in nucleation behavior upon variation of the pattern spacing and coverage we show why the quality of nucleation control can vary significantly in different parameter regimes. In some limits analytical expressions can be formulated for the nucleation control. Our analysis provides a theoretical explanation for previous experimental observations [Wang et al, PRL 98, 225504 (2007)].

cond-mat.mtrl-sci↗

arXiv2008

Different routes towards oscillatory zoning in the growth of solid solutions

Oscillatory zoning, i.e. self-formation of spatial quasi-periodic oscillations in the composition of solid growing from aqueous solution, is analyzed theoretically. Keeping in mind systems like (Ba,Sr)SO4 we propose a 1D model that takes into account the nonideality of the solid solution and the system asymmetry, in particular, reflecting itself in different solubilities for such systems. Based on a linear stability analysis different parameter regions can be identified. Even an ideal solution solution with a sufficiently large asymmetry can display oscillatory zoning. Numerical simulations complement the linear stability analysis as well as the qualitative consideration of the instability development and reveal the nature of the limit cycles.

nlin.PS↗

arXiv2008

Loss of control in pattern-directed nucleation: a theoretical study

The properties of template-directed nucleation are studied close to the transition where full nucleation control is lost and additional nucleation occurs beyond the pre-patterned regions. First, kinetic Monte Carlo simulations are performed to obtain information on a microscopic level. Here the experimentally relevant cases of 1D stripe patterns and 2D square lattice symmetry are considered. The nucleation properties in the transition region depend in a complex way on the parameters of the system, i.e. the flux, the surface diffusion constant, the geometric properties of the pattern and the desorption rate. Second, the properties of the stationary concentration field in the fully controlled case are studied to derive the remaining nucleation probability and thus to characterize the loss of nucleation control. Using the analytically accessible solution of a model system with purely radial symmetry, some of the observed properties can be rationalized. A detailed comparison to the Monte Carlo data is included.

cond-mat.mtrl-sci↗