Results
- Showing results for:
- Reset all filters
Search results
-
Journal articleDhar D, Pruessner G, Expert P, et al., 2016,
Directed Abelian sandpile with multiple downward neighbors
, Physical Review E, Vol: 042107, ISSN: 1539-3755We study the directed Abelian sandpile model on a square lattice, with K downward neighborsper site, K > 2. The K = 3 case is solved exactly, which extends the earlier known solution forthe K = 2 case. For K > 2, the avalanche clusters can have holes and side-branches and are thusqualitatively different from the K = 2 case where avalanche clusters are compact. However, we findthat the critical exponents for K > 2 are identical with those for the K = 2 case, and the largescale structure of the avalanches for K > 2 tends to the K = 2 case.
-
Journal articleBroga KM, Viegas E, Jensen HJ, 2016, , Physica A - Statistical Mechanics and Its Applications, Vol: 457, Pages: 225-238, ISSN: 0378-4371
We analyse the effect of distinct levels of interest rates on the stability of the financial network under ourmodelling framework. We demonstrate that banking failures are likely to emerge early on under sustainedhigh interest rates, and at much later stage - with higher probability - under a sustained low interest ratescenario. Moreover, we demonstrate that those bank failures are of a different nature: high interest ratestend to result in significantly more bankruptcies associated to credit losses whereas lack of liquidity tends tobe the primary cause of failures under lower rates.
-
Journal articleRochester CC, Kondrat S, Pruessner G, et al., 2016, , The Journal of Physical Chemistry C, Vol: 120, Pages: 16042-16050, ISSN: 1932-7447
We develop a statistical theory of charging quasi single-file pores with cations and anions of different sizes as well as solvent molecules or voids. This is done by mapping the charging onto a one-dimensional Blume–Emery–Griffith model with variable coupling constants. The results are supported by three-dimensional Monte Carlo simulations in which many limitations of the theory are lifted. We explore the different ways of enhancing the energy storage which depend on the competitive adsorption of ions and solvent molecules into pores, the degree of ionophilicity and the voltage regimes accessed. We identify new solvent-related charging mechanisms and show that the solvent can play the role of an “ionophobic agent”, effectively controlling the pore ionophobicity. In addition, we demonstrate that the ion-size asymmetry can significantly enhance the energy stored in a nanopore.
-
Journal articleClough JR, Evans TS, 2016, , Physica A: Statistical Mechanics and its Applications, Vol: 448, Pages: 235-247, ISSN: 0378-4371
Citation networks represent the flow of information between agents. They are constrained in time and so form directed acyclic graphs which have a causal structure. Here we provide novel quantitative methods to characterise that structure by adapting methods used in the causal set approach to quantum gravity by considering the networks to be embedded in a Minkowski spacetime and measuring its dimension using Myrheim–Meyer and Midpoint-scaling estimates. We illustrate these methods on citation networks from the arXiv, supreme court judgements from the USA, and patents and find that otherwise similar citation networks have measurably different dimensions. We suggest that these differences can be interpreted in terms of the level of diversity or narrowness in citation behaviour.
-
Journal articleYan X, Minnhagen P, Jensen HJ, 2016, , Physica A - Statistical Mechanics and Its Applications, Vol: 456, Pages: 112-119, ISSN: 0378-4371
We point out that the functional form describing the frequency of sizes of events in complexsystems (e.g. earthquakes, forest fires, bursts of neuronal activity) can be obtained from maximallikelihood inference, which, remarkably, only involve a few available observed measures such asnumber of events, total event size and extremes. Most importantly, the method is able to predictwith high accuracy the frequency of the rare extreme events. To be able to predict the few, oftenbig impact events, from the frequent small events is of course of great general importance. For adata set of wind speed we are able to predict the frequency of gales with good precision. We analyseseveral examples ranging from the shortest length of a recruit to the number of Chinese characterswhich occur only once in a text.
-
Journal articleNekovar S, Pruessner G, 2016, , Journal of Statistical Physics, Vol: 163, Pages: 604-641, ISSN: 0022-4715
The Wiener Sausage, the volume traced out by a sphere attachedto a Brownian particle, is a classical problem in statistics and mathematicalphysics. Initially motivated by a range of field-theoretic, technical questions,we present a single loop renormalised perturbation theory of a stochasticprocess closely related to the Wiener Sausage, which, however, proves to beexact for the exponents and some amplitudes. The field-theoretic approach isparticularly elegant and very enjoyable to see at work on such a classic problem.While we recover a number of known, classical results, the field-theoretictechniques deployed provide a particularly versatile framework, which allowseasy calculation with different boundary conditions even of higher momentaand more complicated correlation functions. At the same time, we provide ahighly instructive, non-trivial example for some of the technical particularitiesof the field-theoretic description of stochastic processes, such as excludedvolume, lack of translational invariance and immobile particles. The aim ofthe present work is not to improve upon the well-established results for theWiener Sausage, but to provide a field-theoretic approach to it, in order togain a better understanding of the field-theoretic obstacles to overcome.
-
Journal articleWatkins NW, Pruessner G, Chapman SC, et al., 2016, , Space Science Reviews, Vol: 198, Pages: 3-44, ISSN: 1572-9672
Introduced by the late Per Bak and his colleagues, self-organized criticality (SOC) has been one of the most stimulating concepts to come out of statistical mechanics and condensed matter theory in the last few decades, and has played a significant role in the development of complexity science. SOC, and more generally fractals and power laws, have attracted much comment, ranging from the very positive to the polemical. The other papers (Aschwanden et al. in Space Sci. Rev., 2014, this issue; McAteer et al. in Space Sci. Rev., 2015, this issue; Sharma et al. in Space Sci. Rev. 2015, in preparation) in this special issue showcase the considerable body of observations in solar, magnetospheric and fusion plasma inspired by the SOC idea, and expose the fertile role the new paradigm has played in approaches to modeling and understanding multiscale plasma instabilities. This very broad impact, and the necessary process of adapting a scientific hypothesis to the conditions of a given physical system, has meant that SOC as studied in these fields has sometimes differed significantly from the definition originally given by its creators. In Bak’s own field of theoretical physics there are significant observational and theoretical open questions, even 25 years on (Pruessner 2012). One aim of the present review is to address the dichotomy between the great reception SOC has received in some areas, and its shortcomings, as they became manifest in the controversies it triggered. Our article tries to clear up what we think are misunderstandings of SOC in fields more remote from its origins in statistical mechanics, condensed matter and dynamical systems by revisiting Bak, Tang and Wiesenfeld’s original papers.
-
Journal articleWatkins NW, Pruessner G, Chapman SC, et al., 2016, , Space Science Reviews, Vol: 198, Pages: 45-45, ISSN: 1572-9672
Introduced by the late Per Bak and his colleagues, self-organized criticality (SOC) has been one of the most stimulating concepts to come out of statistical mechanics and condensed matter theory in the last few decades, and has played a significant role in the development of complexity science. SOC, and more generally fractals and power laws, have attracted much comment, ranging from the very positive to the polemical. The other papers (Aschwanden et al. in Space Sci. Rev., 2014, this issue; McAteer et al. in Space Sci. Rev., 2015, this issue; Sharma et al. in Space Sci. Rev. 2015, in preparation) in this special issue showcase the considerable body of observations in solar, magnetospheric and fusion plasma inspired by the SOC idea, and expose the fertile role the new paradigm has played in approaches to modeling and understanding multiscale plasma instabilities. This very broad impact, and the necessary process of adapting a scientific hypothesis to the conditions of a given physical system, has meant that SOC as studied in these fields has sometimes differed significantly from the definition originally given by its creators. In Bak’s own field of theoretical physics there are significant observational and theoretical open questions, even 25 years on (Pruessner 2012). One aim of the present review is to address the dichotomy between the great reception SOC has received in some areas, and its shortcomings, as they became manifest in the controversies it triggered. Our article tries to clear up what we think are misunderstandings of SOC in fields more remote from its origins in statistical mechanics, condensed matter and dynamical systems by revisiting Bak, Tang and Wiesenfeld’s original papers.
-
Journal articleAschwanden MJ, Crosby NB, Dimitropoulou M, et al., 2016, , Space Science Reviews, Vol: 198, Pages: 47-166, ISSN: 1572-9672
Shortly after the seminal paper “Self-Organized Criticality: An explanation of 1/f noise” by Bak et al. (1987), the idea has been applied to solar physics, in “Avalanches and the Distribution of Solar Flares” by Lu and Hamilton (1991). In the following years, an inspiring cross-fertilization from complexity theory to solar and astrophysics took place, where the SOC concept was initially applied to solar flares, stellar flares, and magnetospheric substorms, and later extended to the radiation belt, the heliosphere, lunar craters, the asteroid belt, the Saturn ring, pulsar glitches, soft X-ray repeaters, blazars, black-hole objects, cosmic rays, and boson clouds. The application of SOC concepts has been performed by numerical cellular automaton simulations, by analytical calculations of statistical (powerlaw-like) distributions based on physical scaling laws, and by observational tests of theoretically predicted size distributions and waiting time distributions. Attempts have been undertaken to import physical models into the numerical SOC toy models, such as the discretization of magneto-hydrodynamics (MHD) processes. The novel applications stimulated also vigorous debates about the discrimination between SOC models, SOC-like, and non-SOC processes, such as phase transitions, turbulence, random-walk diffusion, percolation, branching processes, network theory, chaos theory, fractality, multi-scale, and other complexity phenomena. We review SOC studies from the last 25 years and highlight new trends, open questions, and future challenges, as discussed during two recent ISSI workshops on this theme.
-
Journal articleGoldberg SR, Anthony H, Evans TS, 2015, , SCIENTOMETRICS, Vol: 105, Pages: 1577-1604, ISSN: 0138-9130
- Cite
- Citations: 31
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.