2017 Impact factor 1.536
Condensed Matter and Complex Systems

News / Highlights / Colloquia

EPJ B Highlight - Market crashes are anomalous features in the financial data fractal landscape

Graph of the normalised empirically found distribution of the American Dow Jones Industrial Average index, DJIA (red squares), and European Euro Stoxx 50 (blue circles) index data with prices recorded every minute data along with the Standard Normal curve for comparison. © Green et al.

Analysing the adequation of financial data structure with its expected fractal scaling could help early detection of extreme financial events because these represent a scaling irregularity

Due to their previously discovered fractal nature, financial data patterns are self-similar when scaling up. New research shows that the most extreme events in financial data dynamics—reflected in very large price moves—are incompatible with multi-fractal scaling. These findings have been published in EPJ B by physicist Elena Green from the National University of Ireland, Maynooth, Ireland and colleagues. Understanding the multi-fractal structure of financially sound markets could, ultimately, help in identifying structural signs of impending extreme events.

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EPJ B Highlight - Particles near absolute zero do not break the laws of physics after all

A free particle strongly coupled to a heat bath. © Adamietz et al.

A change of models demystifies anomalous particle behaviour at very low temperatures, confirming that the third law of thermodynamics cannot be violated

In theory, the laws of physics are absolute. However, when it comes to the laws of thermodynamics—the science that studies how heat and temperature relate to energy—there are times where they no longer seem to apply. In a paper recently published in EPJ B, Robert Adamietz from the University of Augsburg, Germany, and colleagues have demonstrated that a theoretical model of the environment’s influence on a particle does not violate the third law of thermodynamics, despite appearances to the contrary. These findings are relevant for systems at the micro or nanometer scale that are difficult to decouple from the heat or the quantum effects exerted by their environment.

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EPJ B Highlight - Nanoscale heat flow predictions

Snapshot of the final configuration of a nc-Si sample. © Melis et al.

A new study predicts that heat flow in novel nanomaterials could contribute to creating environmentally friendly and cost-effective nanometric-scale energy devices

Physicists are now designing novel materials with physical properties tailored to meet specific energy consumption needs. Before these so-called materials-by-design can be applied, it is essential to understand their characteristics, such as heat flow. Now, a team of Italian physicists has developed a predictive theoretical model for heat flux in these materials, using atom-scale calculations. These findings, published in EPJ B by Claudio Melis and colleagues from the University of Cagliary, Italy, could have implications for optimising the thermal budget of nanoelectronic devices—which means they could help dissipate the total amount of thermal energy generated by electron currents—or in the production of energy through thermoelectric effects in novel nanomaterials.

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EPJ B Highlight - Grasp of SQUIDs dynamics facilitates eavesdropping

Average voltage output of a DC SQUID under varying conditions. © Berggren et al.

Latest theoretical advances pertaining to the dynamics of highly sensitive magnetometers could find military applications in low-noise amplifiers and sensitive antennas

Theoretical physicists are currently exploring the dynamics of a very unusual kind of device called a SQUID. This Superconducting Quantum Interference Device is a highly sensitive magnetometer used to measure extremely subtle magnetic fields. It is made of two thin regions of insulating material that separate two superconductors – referred to as Josephson junctions – placed in parallel into a ring of superconducting material. In a study published in EPJ B, US scientists have focused on finding an analytical approximation to the theoretical equations that govern the dynamics of an array of SQUIDs. This work was performed by Susan Berggren from the US Navy research lab, SPAWAR Systems Center Pacific, in San Diego, CA, USA and Antonio Palacios San Diego State University. Its applications are mainly in the military sector, including SQUID array-based low-noise amplifiers and antennas.

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EPJ B Highlight - Graphene nanoribbons as electronic switches

© Credit: Dmitry Knorre/Fotolia

A new theoretical study shows the conductivity conditions under which graphene nanoribbons can become switches in externally controlled electronic devices

One of graphene’s most sought after properties is its high conductivity. Argentinian and Brazilian physicists have now successfully calculated the conditions of the transport, or conductance mechanisms, in graphene nanoribbons. The results, recently published in a paper in EPJ B, yield a clearer theoretical understanding of conductivity in graphene samples of finite size, which have applications in externally controlled electronic devices.

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EPJB Colloquium – From SiC to fluorescent SiC based white LEDs

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Three free standing 3C-SiC substrates with size 10x10 mm (Fig. 16).

A new EPJ B Colloquium reviews the latest advances in silicon carbide (SiC) for optoelectronics. The wide bandgap of SiC makes it a great semiconductor material to make devices for in high power, high frequency and high temperature applications.

During the past decade, SiC has also become a promising materials for light-emitting diodes (LED), since it was found that co-doping it with nitrogen and boron produces a high donor-acceptor pair emission efficiency. Fluorescent SiC based white LED light source is an innovative concept for optoelectronic devices.

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EPJB Review - New promising bulk thermoelectrics

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Superlattice structure of (BiS)1.2(TiS2)2 misfit layer sulfide. (Fig. 15).

The growing need for alternative “green” energy sources has prompted renewed interest in thermoelectric materials. These materials can directly convert heat to electricity or, conversely, use electrical current to cool. The thermoelectric performance of a material can be estimated by the so-called figure of merit, zT = σα2T/λ (α is the Seebeck coefficient, σα2 is the power factor, σ and λ are the electrical and thermal conductivity, respectively), the value of which depends only on the material.

In a new EPJ B review, authors Gonçalves and Godart discuss the state of the art in this field, with special emphasis on the strategies to reduce the lattice part of the thermal conductivity and maximize the power factor in thermoelectric materials.

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EPJ B Highlight - Football displays fractal dynamics

Players’ and ball’s positions captured on video. © Kijima et al.

Physicists reveal that the real-time dynamics in a football game are subject to self-similarity characteristics in keeping with the laws of physics, regardless of players’ psychology and training

Football fascinates millions of fans, all of them unaware that the game is subject to the laws of physics. Despite their seemingly arbitrary decisions, each player obeys certain rules, as they constantly adjust their positions in relation to their teammates, opponents, the ball and the goal. A team of Japanese scientists has now analysed the time-dependent fluctuation of both the ball and all players’ positions throughout an entire match. They discovered that a simple rule governs the complex dynamics of the ball and the team’s front-line. These findings , published in EPJ B, could have implications for other ball games, providing a new perspective on sports science.

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EPJ B Highlight - Probing the edge of chaos

Fractals. © wajakaa - Photolia

To understand natural phenomena with a chaotic nature, the key is to find out how their variable physical characteristics behave at the very point preceding the onset of chaos

The edge of chaos—right before chaos sets in—is a unique place. It is found in many dynamical systems that cross the boundary between a well-behaved dynamics and a chaotic one. Now, physicists have shown that the distribution—or frequency of occurrence—of the variables constituting the physical characteristics of such systems at the edge of chaos has a very different shape than previously reported distributions. The results have been published in EPJ B by Miguel Angel Fuentes from the Santa Fe Institute in New Mexico, USA, and Universidad del Desarrollo, Chile, and Alberto Robledo from the National Autonomous University of Mexico, Mexico City. This could help us better understand natural phenomena with a chaotic nature.

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EPJ B Highlight - Optimising custody is child’s play for physicists

A graph depicting the children’s custody problem, where grey nodes represent couples. © Gomberoff et al.

Ensuring that parents in recomposed families see their children regularly is a complex network problem that models developed to study materials may help to solve

Physics can provide insights into societal trends. Problems involving interactions between people linked in real-life networks can be better understood by using physical models. As a diversion from his normal duties as a theoretical physicist, Andrés Gomberoff from the Andres Bello University, in Santiago, Chile, set out to resolve one of his real-life problems: finding a suitable weekend for both partners in his recomposed family to see all their children at the same time. He then joined forces with a mathematician and a complex systems expert. This resulted in a study published in EPJ B, showing that solving this problem essentially equates to minimising the energy in a material model.

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Acting EiC: Wenhui Duan

Executive Editors:
B.K. Chakrabarti, W. Duan, E. Hernandez, H. Rieger
Thank you for the very fruitful and efficient collaboration. It has been a pleasure!!

Paul van Loosdrecht, Guest Editor Topical issue: Excitonic Processes in Condensed Matter, Nanostructured and Molecular Materials, 2013

ISSN (Print Edition): 1434-6028
ISSN (Electronic Edition): 1434-6036

© EDP Sciences, Società Italiana di Fisica and Springer-Verlag