- Published on 25 January 2022
A novel theory can link abrupt, non-equilibrium changes to the state of the economy to a central principle of dynamics and thermodynamics
Equilibrium is a fundamental concept in economics: describing situations where the many interacting variables governing the state of the economy are static and perfectly balanced. Yet in reality, the inherent uncertainty and randomness associated with these variables, combined with the fragility of economists’ expectations, mean that the economy can never really be in true equilibrium. In new research published in EPJ B, a research team led by Kun Zhang from the Changchun Institute of Applied Chemistry of the Chinese Academy of Sciences, and Jin Wang at State University of New York at Stony Brook, use new mathematical theories to capture the economy’s true non-equilibrium nature and to show how it can be quantified.
- Published on 12 August 2021
The Publishers and Editors-in-Chief of EPJB: Condensed Matter and Complex Systems are delighted to announce the appointment of three new members of the Editorial Board: Prof Veronica Barone of Central Michigan University, Mount Pleasant, USA; Prof Sanghamitra Neogiof the University of Colorado, Boulder, USA; and Dr Philipp Hövel (starting September 1st), of the School of Mathematical Sciences, University College Cork, Ireland.
- Published on 23 March 2021
The two-dimensional case occupies a special position in the theory of critical phenomena due to the exact results provided by lattice solutions and, directly in the continuum, by the infinite-dimensional character of the conformal algebra. However, some sectors of the theory, and most notably criticality in systems with quenched disorder and short range interactions, have appeared out of reach of exact methods and lacked the insight coming from analytical solutions.
EPJ B Highlight - Considering disorder and cooperative effects in photon escape rates from atomic gases
- Published on 26 February 2021
Investigating more complex models of photon escape rates from cold atomic gases could help researchers learn more about light-matter interactions.
Whilst a great deal of research has studied the rates of photons escaping from cold atomic gases, these studies have used a scalar description of light leaving some of its properties untested. In a new paper published in EPJ B Louis Bellando, a post-doctoral researcher at LOMA, University of Bordeaux, France, and his coauthors—Aharon Gero and Eric Akkermans, Technion-Israel Institute of Technology, Israel, and Robin Kaiser, Université Côte d'Azur, France—aim to numerically investigative the roles of cooperative effects and disorder in photon escape rates from a cold atomic gas to construct a model that considers the vectorial nature of light. Thus, the study accounts for properties of light, previously neglected.
- Published on 02 February 2021
Novel approaches in graph theory have enabled researchers to reveal the characteristic configurations of neurons which arise as our brains process pain
The many different sensations our bodies experience are accompanied by deeply complex exchanges of information within the brain, and the feeling of pain is no exception. So far, research has shown how pain intensity can be directly related to specific patterns of oscillation in brain activity, which are altered by the activation and deactivation of the ‘interneurons’ connecting different regions of the brain. However, it remains unclear how the process is affected by ‘inhibitory’ interneurons, which prevent chemical messages from passing between these regions. Through new research published in EPJ B, researchers led by Fernando Montani at Instituto de Física La Plata, Argentina, show that inhibitory interneurons make up 20% of the circuitry in the brain required for pain processing.
- Published on 29 January 2021
Microscopically very different physical, biological and cultural systems all evolve through a sequence of stages, each characterized by stationary fluctuations around constant values of relevant macroscopic observables. Sudden and rapid changes, called quakes, induce transitions from one stage to the next and reveal the non-equilibrium nature of the dynamics. The duration of the stages increases over time, producing a multi-scaled dynamical behavior known in physics under the name of ``physical aging'', and rooted in all cases in a hierarchically structured underlying configuration space. Record Dynamics (RD) is a coarse-graining approach treating the staged evolution of complex metastable systems with the same statistical tools. This colloquium paper reviews RD methods and ideas that have gradually evolved over time and shows how RD can be applied to selected cases of biological and physical origin. The main property described is that quakes are a log-Poisson process and that the coarse-grained dynamics is therefore log-time homogeneous. The bibliography points the interested reader to the original RD papers and their background.
- Published on 07 December 2020
Improved modelling techniques have enabled a group of researchers to better predict how damaging conditions in the brain can be triggered by complex dynamics in branching networks of neurons.
Within the staggeringly complex networks of neurons which make up our brains, electric currents display intricate dynamics in the electric currents they convey. To better understand how these networks behave, researchers in the past have developed models which aim to mimic their dynamics. In some rare circumstances, their results have indicated that ‘tipping points’ can occur, where the systems abruptly transition from one state to another: events now commonly thought to be associated with episodes of epilepsy. In a new study published in EPJ B, researchers led by Fahimeh Nazarimehr at the University of Technology, Tehran, Iran, show how these dangerous events can be better predicted by accounting for branches in networks of neurons.
- Published on 04 December 2020
Two-dimensional (2D) materials are condensed matter systems whose thickness varies from a single atom, as in graphene, to few atoms, as in transition metal dichalcogenides (TMDs). These exceedingly thin materials present, nevertheless, strong light-matter interaction.
EPJ B Colloquium - Hierarchically nanostructured thermoelectric materials: challenges and opportunities for improved power factors
- Published on 26 November 2020
The field of thermoelectric materials has undergone a revolutionary transformation over the last couple of decades as a result of the ability to nanostructure and synthesize myriads of materials and their alloys. The ZT figure of merit, which quantifies the performance of a thermoelectric material has more than doubled after decades of inactivity, reaching values larger than two, consistently across materials and temperatures. Central to this, is the drastic reduction in the materials’ thermal conductivity due to the hierarchical scattering of phonons on the purposely included numerous interfaces, boundaries, dislocations, point defects, phases, etc. However, as the thermal conductivity has reached amorphous values, these benefits are reaching their limits. Any further benefits would come from the power factor, namely the product of the electronic conductivity and Seebeck coefficient squared. These quantities need to be maximized, however, they are in general inversely related, which makes power factor improvement a significant challenge.
- Published on 06 November 2020
New research reveals that applying a magnetic field to a chiral metamaterial can change the way it polarises light.
Optical activity in chiral molecules has become a hot topic in physics and optics, representing the ability to manipulate the polarized state of light. Understanding how molecules rotate the plane of plane-polarized light has widespread applications, from analytic chemistry to biology and medicine — where it can, for example, be used to detect the amount of sugar in a substance. A new study published in EPJ B by Chengping Yin of the Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, South China, aims to derive an analytical model of optical activity in black phosphorous under an external magnetic field.