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Condensed Matter and Complex Systems

News / Highlights / Colloquia

EPJ B Highlight - Green photon beams more agile than optical tweezers

Charge-density computation of butane molecules.

A new manipulation tool exploits the fact that when light interacts with matter, it creates a force that produces material properties in macromolecules and biological cells

Romanian scientists have discovered a novel approach for the optical manipulation of macromolecules and biological cells. Their findings stem from challenging the idea that visible light would induce no physical effect on them since it is not absorbed. Instead, Sorin Comorosan, working as physicist at the National Institute for Physics and Nuclear Engineering based in Magurele, Romania, and as a biologist at the Fundeni Clinical Institute, Bucharest, Romania, and colleagues had the idea to use green photon beams. With them, it is possible to perform optical manipulation of macrostructures, such as biological proteins, with greater precision than with optical tweezers made from focused laser beams.

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EPJ B Highlight - Atom-based analogues to electronic devices

Spectral functions of the first (left panel) and the second (right panel) quantum dot.

New research gives a theoretical explanation as to how transport of single atoms is made possible through a chain of quantum dots

Scientists have pushed back the boundaries of atom-based transport, creating a current by charac-terising the many-body effects in the transport of the atoms along a periodic lattice. This work by Anton Ivanov and colleagues from the Institute for Theoretical Physics, at the University of Heidel-berg, Germany, adopted a new analytical approach before comparing it to approximate numerical simulations, and is reported in a paper recently published in EPJ B.

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EPJ B Highlight - Studying emotions causing opinions to change

Example of evolution of agent opinions.

Physicists can use their tools to help understand how, in real life, opinions form and change by modelling the complex interactions between information and emotion

Social phenomena fascinate with their complexity, but are not easily understood. Pawel Sobkowicz, an independent researcher based in Warsaw, Poland, has developed a model to study the dynamic of standard people, called ‘agents’, and their response to a given piece of information, depending on their emotional state. In a study just published in EPJ B, the author shows that opinion dynamics differ depending on whether the agent is agitated or not.

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EPJ B Highlight - When diffusion depends on chronology

Motorways are an example of nodes connected by edges studied as complex networks.
© Highways Agency

Study shows that the order of events taking place in complex networks may dramatically alter the way diffusion occurs

The Internet, motorways and other transport systems, and many social and biological systems are composed of nodes connected by edges. They can therefore be represented as networks. Scientists studying diffusion over such networks over time have now identified the temporal characteristics that affect their diffusion pathways. In a paper just published in EPJ B, Renaud Lambiotte and Lionel Tabourier from the University of Namur, Belgium, together with Jean-Charles Delvenne from the Catholic University of Louvain, Belgium, show that one key factor that can dramatically change a diffusion process is the order in which events take place in complex networks.

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EPJ B Highlight - Semantics on the basis of words’ connectivity

Illustration of a tourist walk.

It is now possible to identify the meaning of words with multiple meanings, without using their semantic context

Two Brazilian physicists have now devised a method to automatically elucidate the meaning of words with several senses, based solely on their patterns of connectivity with nearby words in a given sentence – and not on semantics. Thiago Silva and Diego Amancio from the University of São Paulo, Brazil, reveal, in a paper just published in EPJ B, how they modelled classics texts as complex networks in order to derive their meaning. This type of model plays a key role in several natural processing language tasks such as machine translation, information retrieval, content analysis and text processing.

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EPJ B Highlight - Averting worse economic collapses

The local separation of one equilibrium surface from another.

A new study shows how specific parameters can help us steer clear of tipping points in dynamic systems, such as entire economies.

By managing macro-economic parameters, scientists believe that—unlike previously thought—it is possible to steer an economy around irreversible changes in its complex dynamics and avert potential economic disasters. These findings, just published in EPJ B, stem from the theoretical work of Michael Harré and colleagues at the Complex Systems Group at the University of Sydney, Australia.

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EPJ B Highlight - Predicting collective online behaviour

The visualisation of several clickstream networks.

A team of Chinese scientists evaluates the impact of a website based on the interaction between its users with the entire Web

A new study shows that small websites, in terms of daily user flux based on number of clicks, have a disproportionally high impact when it comes to traffic generation and influence compared to larger websites. These findings, just published in EPJ B, have implications for estimating the value of sites and related advertising revenue. They result from the work of Lingfei Wu from the City University of Hong Kong and Jiang Zhang from the School of Management, at Beijing Normal University, China.

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EPJ B Highlight - Coupled particles cross energy wall

Numerically-computed evolution of the coupled particle density function across the potential wall

Model demonstrates that it is possible for two particles to cross an energy barrier together, where a single particle could not

For the first time, a new kind of so-called Klein tunnelling—representing the quantum equivalent of crossing an energy wall— has been presented in a model of two interacting particles. This work by Stefano Longhi and Giuseppe Della Valle from the Institute of Photonics and Nanotechnology in Milan, Italy, has just been published in EPJ B.

Klein tunnelling is a quantum phenomenon referring to the fact that a high-potential barrier can be transparent to a particle moving at a speed nearing that of light, referred to as relativistic. Most of the previous Klein tunnelling models describe the phenomenon for a single particle. However, when two particles are involved, tunnelling can be modified as a result of their mutual interaction. This means, for example, that two electrons hopping on a lattice, or two ultra-cold atoms trapped in an optical lattice can exchange energy when they occupy the same lattice site.

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EPJ B Highlight - Promising doped zirconia

Positive (red) and negative (blue) isosurfaces of the magnetisation density of doped zirconia

A new study discusses the electric and magnetic characteristics of a material which could be used in spintronics

Materials belonging to the family of dilute magnetic oxides (DMOs) — an oxide-based variant of the dilute magnetic semiconductors — are good candidates for spintronics applications. This is the object of study for Davide Sangalli of the Microelectronics and Microsystems Institute (IMM) at the National Research Council (CNR), in Agrate Brianza, Italy, and colleagues. They recently explored the effect of iron (Fe) doping on thin films of a material called zirconia (ZrO2 oxide). For the first time, the authors bridged the gap between the theoretical predictions and the experimental measurements of this material, in a paper just published in EPJ B.

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EPJ B Highlight - Physicists decipher social cohesion issues

Evolution of individuals into clusters representing social cohesion, under directional migrations. © H. Y. Cheng et al

Studying the effect of migration on cooperation could help to better understand social cohesion

Migrations happen for a reason, not randomly. A new study, based on computer simulation, attempts to explain the effect of so-called directional migration – migration for a reason – on cooperative behaviours and social cohesion. These results appear in a study just published in EPJ B by Hongyan Cheng from Beijing University of Posts and Telecommunications and colleagues.

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Executive Editors:
Eduardo Hernandez, Heiko Rieger, Bikas K. Chakrabarti, Wenhui Duan
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

Conference announcements

POSMOL 2017

Magnetic Island, Queensland, Australia, 22-24 July 2017