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Search Results: 1 - 10 of 10612 matches for " Andreas Nussbaumer "
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Make life simple: unleash the full power of the parallel tempering algorithm
Elmar Bittner,Andreas Nussbaumer,Wolfhard Janke
Physics , 2008, DOI: 10.1103/PhysRevLett.101.130603
Abstract: We introduce a new update scheme to systematically improve the efficiency of parallel tempering simulations. We show that by adapting the number of sweeps between replica exchanges to the canonical autocorrelation time, the average round-trip time of a replica in temperature space can be significantly decreased. The temperatures are not dynamically adjusted as in previous attempts but chosen to yield a 50% exchange rate of adjacent replicas. We illustrate the new algorithm with results for the Ising model in two and the Edwards-Anderson Ising spin glass in three dimensions
Evaporation/Condensation of Ising Droplets
Andreas Nussbaumer,Elmar Bittner,Wolfhard Janke
Physics , 2005,
Abstract: Recently Biskup et al. [Europhys. Lett. 60 (2002) 21] studied the behaviour of d-dimensional finite-volume liquid-vapour systems at a fixed excess $\delta N$ of particles above the ambient gas density. They identify a dimensionless parameter $\Delta (\delta N)$ and a universal constant $\Delta_\mathrm{c}(d)$ and show that for $\Delta < \Delta_c$ a droplet of the dense phase occurs while for $\Delta > \Delta_c$ the excess is absorbed in the background. The fraction $\lambda_\Delta$ of excess particles forming the droplet is given explicitly. Furthermore, they state, that the same is true for solid-gas systems. To verify these results, we have simulated the spin-1/2 Ising model on a square lattice at constant magnetisation equivalent to a fixed particle excess in the lattice-gas picture. We measured the largest minority droplet, corresponding to the solid phase, at various system sizes ($L=40, ..., 640$). Using analytic values for the spontaneous magnetisation $m_0$, the susceptibility $\chi$ and interfacial free energy $\tau_\mathrm{W}$ for the infinite system, we were able to determine $\lambda_\Delta$ in very good agreement with the theoretical prediction.
Self-affirmation model for football goal distributions
Elmar Bittner,Andreas Nussbaumer,Wolfhard Janke,Martin Weigel
Physics , 2007, DOI: 10.1209/0295-5075/78/58002
Abstract: Analyzing football score data with statistical techniques, we investigate how the highly co-operative nature of the game is reflected in averaged properties such as the distributions of scored goals for the home and away teams. It turns out that in particular the tails of the distributions are not well described by independent Bernoulli trials, but rather well modeled by negative binomial or generalized extreme value distributions. To understand this behavior from first principles, we suggest to modify the Bernoulli random process to include a simple component of self-affirmation which seems to describe the data surprisingly well and allows to interpret the observed deviation from Gaussian statistics. The phenomenological distributions used before can be understood as special cases within this framework. We analyzed historical football score data from many leagues in Europe as well as from international tournaments and found the proposed models to be applicable rather universally. In particular, here we compare men's and women's leagues and the separate German leagues during the cold war times and find some remarkable differences.
Football fever: goal distributions and non-Gaussian statistics
Elmar Bittner,Andreas Nussbaumer,Wolfhard Janke,Martin Weigel
Physics , 2006, DOI: 10.1140/epjb/e2008-00396-1
Abstract: Analyzing football score data with statistical techniques, we investigate how the not purely random, but highly co-operative nature of the game is reflected in averaged properties such as the probability distributions of scored goals for the home and away teams. As it turns out, especially the tails of the distributions are not well described by the Poissonian or binomial model resulting from the assumption of uncorrelated random events. Instead, a good effective description of the data is provided by less basic distributions such as the negative binomial one or the probability densities of extreme value statistics. To understand this behavior from a microscopical point of view, however, no waiting time problem or extremal process need be invoked. Instead, modifying the Bernoulli random process underlying the Poissonian model to include a simple component of self-affirmation seems to describe the data surprisingly well and allows to understand the observed deviation from Gaussian statistics. The phenomenological distributions used before can be understood as special cases within this framework. We analyzed historical football score data from many leagues in Europe as well as from international tournaments, including data from all past tournaments of the ``FIFA World Cup'' series, and found the proposed models to be applicable rather universally. In particular, here we analyse the results of the German women's premier football league and consider the two separate German men's premier leagues in the East and West during the cold war times and the unified league after 1990 to see how scoring in football and the component of self-affirmation depend on cultural and political circumstances.
Castration of piglets under general anaesthesia: a possible approach
Iwan Nussbaumer
Veterinary Science Development , 2012, DOI: 10.4081/vsd.2012.e9
Abstract: Since January 2010 the castration of piglets without pain relief has been forbidden in Switzerland. Swiss pig farmers now have two choices, either vet-performed anaesthesia and analgesia by intramuscular injection or farmer-administered isofluran anaesthesia by an inhalation device. Many smaller pig producers, with less than 60 sows, have chosen injected anaesthesia for economic, user safety and environmental reasons.
Bernard Jouve et Christian Lefèvre (éd), 2004, Horizons Metropolitains, Lausanne, Editions Presses Polytechniques et Universitaires romandes, Collection Recherches Urbaines , 288p., 47€.
Jacques Nussbaumer
Développement Durable et Territoires , 2004,
Abstract: Sous un titre elliptique, cet ouvrage collectif analyse la question de la métropolisation sous l’angle de la transformation du cadre de l’action publique, en proposant une approche doublement comparative. D’une part, il s’appuie sur six exemples de métropoles européennes de rang moyen (Marseille, Lyon, Genève-Lausanne, Stuttgart, Zurich, Naples), permettant de mettre en parallèles différents cadres institutionnels et différentes pratiques de gouvernance. D’autre part, pour chaque métropole ét...
Einstein's aborted attempt at a dynamic steady-state universe
Harry Nussbaumer
Physics , 2014,
Abstract: In June 1930 Einstein visited Cambridge where he stayed with Eddington who had just shown that Einstein's supposedly static universe of 1917 was not stable. This forced Einstein to rethink his cosmology. He spent January and February 1931 at Pasadena. There, he discussed cosmology intensely with Tolman, conscious that he had to replace his original model of 1917. However, at the end of February he still had not made up his mind about an alternative. The Albert Einstein Archives of Jerusalem (AEA) hold an undated draft, handwritten by Einstein, which I date to the beginning of January 1931. In this draft Einstein hopes to have found a solution to the cosmological problem: a stationary, dynamic universe in expansion. His model was stationary because particles leaving a given volume were replaced by particles created out of the vacuum, anticipating an idea of Bondi, Gold and Hoyle published in 1948. He saw the cosmological term as energy reservoir. However, he realised that his calculations contained a numerical error. When the error was corrected his steady-state-model collapsed.
Slipher's redshifts as support for de Sitter's model and the discovery of the dynamic universe
Harry Nussbaumer
Physics , 2013,
Abstract: Of the first two relativistiv world models, only the one by de Sitter predicted redshifted spectra from far away astronomical objects. Slipher's redshifts therefore seemed to arbitrate against Einstein's model which made no such predictions. Both models were trying to describe a static universe. However, Lemaitre found that de Sitter's construct resulted in a spatially inhomogeneous universe. He then opted for a model that correspondes to Einstein's closed, curved universe but allowed the radius of curvature to change with time. Slipher's redshifts suggested to him that the universe is dynamic and expanding. We also discuss the respective merits of Friedman and Lemaitre in revealing the dynamic nature of the universe.
Einstein's conversion from his static to an expanding universe
Harry Nussbaumer
Physics , 2013, DOI: 10.1140/epjh/e2013-40037-6.
Abstract: In 1917 Einstein initiated modern cosmology by postulating, based on general relativity, a homogeneous, static, spatially curved universe. To counteract gravitational contraction he introduced the cosmological constant. In 1922 Alexander Friedman showed that Einstein's fundamental equation also allowed dynamical worlds, and in 1927 Geroges Lemaitre, backed by observational evidence, concluded that our universe was expanding. Einstein impetuously rejected Friedman's as well as Lemaitre's findings. However, in 1931 he retracted his former static model in favour of a dynamic solution. This investigation follows Einstein on his hesitating path from a static to the expanding universe. Contrary to an often repeated belief the primary motive for his switch was not observational evidence, but the realisation that his static model was unstable.
Who discovered the expanding universe?
Harry Nussbaumer,Lydia Bieri
Physics , 2011,
Abstract: Who discovered the expanding universe? Was it Hubble, or Lema\^itre, or was it just the end result of a long series of investigations? In this article we summarise the main steps and contributions that led to one of the most exciting discoveries ever made, of which Lema\^itre was the principal architect. In 1927 he combined his dynamical solutions of the Einstein equations with astronomical observations to conclude that the universe is expanding. He derived the linear velocity-distance relationship and calculated the first numerical value of what later was called the "Hubble constant". His discovery paper of 1927 was written in French and in 1931 it was translated into English and published in Monthly Notices. However, the translation omits the section where Lema\^itre computed the "Hubble constant". Why was that done, and who was responsible? We do not speculate on this question, but present in a very condensed way the facts along the path of discovery. The documented details from primary sources can be found in our book "Discovering the Expanding Universe".
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