2019 Impact factor 3.000


EPJ B Highlight - Skyrmion dynamics and traverse mobility

Skyrmion trajectory with red circles representing obstacles

Skyrmions could revolutionise computing exhibiting great potential in the electronic storage of information, and the key to such a breakthrough could be understanding their behaviour under applied currents.

As the demands on information technology increase, the need to improve the storage of data also grows. Many solid-state systems suggested for such a task are founded on the manipulation of skyrmions, perfect for such a role due to their size and stability. In a study published in EPJ B, authors N.P. Vizarim and C.J.O. Reichhardt from the Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, New Mexico, USA and their colleagues aim to understand how skyrmions behave in a substrate under dc and ac drives.


EPJ B Highlight - Simulating cooperation in local communities

Modelling an increase in cooperation

Simulations reveal how the social benefits of supplies to goods and service providers in China could be improved through a payoff transfer system, which rewards individuals who cooperate the most with their local communities.

Many goods and service providers in China rely on supplies from local governments, but these are often limited by financial budgets – especially in rural villages. Members of the public must cooperate with their governments and each other in order for this system to run smoothly, but unfortunately, this balance is threatened by a small proportion of individuals who take in welfare without contributing fairly to their communities. In new research published in EPJ B, Ran Yang and colleagues at Tianjin University, China, introduce a new simulation-based approach which could help to solve this issue, through a cost-effective system which rewards individuals who use welfare systems responsibly.


EPJ D Topical review - Wigner scattering theory for systems held together by Coulombic forces

Originally developed and formulated for nuclear scattering, Wigner’s theory is extremely general, with application in many branches of physics. Atomic Physics often makes use of an apparently separate formalism (MQDT) which is in fact a specialisation of Wigner’s theory. In a new Topical Review article published in EPJD, Jean-Patrick Connerade (Imperial College London, UK and and European Academy EASAL, France) discusses the relevance of Wigner Scattering theory and in particular its K-matrix formulation for all systems held together by coulombic forces, including not only atoms and molecules but also clusters.


EPJ B Colloquium - Origin of optical bandgap fluctuations in graphene oxide

Graphene Oxide (GO) is a carbon-based nanomaterial prepared through the chemical oxidation of natural graphite in the presence of strong oxidants. It was identified long before pristine graphene, first reported in the 17th century by Brodie et al. Among many potential applications, GO can be used to produce reduced GO (rGO) for transparent conducting electrodes (TCEs), which has been, for instance, employed in the preparation of organic-light emitting diodes and organic photovoltaic devices. Other works also report the successful use of GO for the preparation of membranes for desalination and water purification, as well as active layers in biosensors, among many other applications. To address the needs of theses versatile applications several modifications in the synthesis of GO have been developed.


EPJ B Highlight - Exploring mass dependence in electron-hole clusters

Electron-hole pairs can form within crystals (By Axelfoley12, from https://en.wikipedia.org/wiki/ Exciton#/media/File:Exciton.png)

New calculations reveal that the behaviours of electron-hole clusters depend strongly on the masses of their particles.

In solid materials, when an electron changes position without another to fill its place, a positively charged ‘hole’ can appear which is attracted to the original electron. In more complex situations, the process can even result in stable clusters of multiple electrons and holes, whose behaviours all depend on each other. Strangely, the masses of each particle inside a cluster can be different to their masses when they are on their own. However, physicists aren’t yet entirely clear how these mass variations can affect the overall properties of clusters in real solids. Through a study published in EPJ B, Alexei Frolov at the University of Western Ontario, Canada, reveals that the behaviour of one type of three-particle cluster displays a distinct relationship with the ratio between the masses of its particles.


EPJ ST Highlight – Introduction to Celestial Mechanics in the XXIst Century

Space exploration is moving into a new era, the turn of the century has seen past glories fade and the focus of science and research move from one-off achievements and firsts, to the establishment of frameworks that will encourage sustainability. At the same time, the more we learn about space, the more we realise that plans must be put in place to mitigate threats from beyond our own atmosphere. As such, the EPJ Special Topics issue on ‘Celestial Mechanics in the XXIst Century’ reflects this shift in attention by spotlighting research that aims to cement humankind’s place amongst the stars.

Here, we present highlights from this issue where we learn how spacecrafts can get a boost in ‘Aerogravity Assisted’ interactions, how we might reduce the risk of space debris collision, and how a tethered diversion might protect Earth from asteroid impact.

EPJ ST Highlight - Spacecrafts get a boost in ‘Aerogravity Assisted’ interactions

The Voyager 2 probe gained the energy boost to escape the solar system from an AGA (NASA/JPL)

New research examines the effect of rotation and other variables in the applications of ‘aerogravity assisted’ manoeuvres to obtain an energy boost for space craft.

In a recent paper published in EPJ Special Topics, Jhonathan O. Murcia Piñeros, a post-doctoral researcher at Space Electronics Division, Instituto Nacional de Pesquisas Espaciais, São José dos Campos, Brazil, and his co-authors, map the energy variations of the spacecraft orbits during ‘aerogravity assisted’ (AGA) manoeuvres. A technique in which energy gains are granted to a spacecraft by a close encounter with a planet or other celestial body via that body’s atmosphere and gravity.


EPJ ST Highlight - Reducing the risk of space debris collision

Debris plot by NASA / Public Domain

An increase in space launches requires the development of a method to clear space debris which could collide with valuable equipment. One plausible method of achieving this through the use of a tug vehicle requires a successful connection procedure.

As humanity expands its horizons beyond the Earth and begins to consider space missions with extended duration, sustainability necessitates the launch of more space vehicles, increasing the risk of collision with existing space debris. One method of clearing this debris involves a tug vehicle dragging it to a safe region. In a new paper published in EPJ Special Topics, authors Antônio Delson Conceição de Jesus and Gabriel Luiz F. Santos, both from the State University of Feira de Santana, Bahia, Brazil, model the complex rendezvous manoeuvres a tug vehicle clearing space debris would have to undergo to mitigate the risk of a collision that could cause irreparable damage at the moment of coupling.


EPJ ST Highlight - Protecting Earth from asteroid impact with a tethered diversion

A depiction of a tether connecting two asteroids

The use of a tether assisted system could prevent an asteroid impacting Earth without the risk of fragmentation.

Our planet exists within the vicinity of thousands of Near-Earth Objects (NEOs), some of which –  Potentially Hazardous Asteroids (PHAs)  –  carry the risk of impacting Earth causing major damage to infrastructure and loss of life. Methods to mitigate such a collision are highly desirable. A new paper published in EPJ Special Topics, authored by Flaviane Venditti, Planetary Radar Department, Arecibo Observatory, University of Central Florida, Arecibo, suggests the use of a tether assisted system to prevent PHA impact.


EPJ E Highlight - ‘Bottom-heavy squirmers’ adopt characteristic group behaviours

Simulating motions of bottom-heavy squirmers.

Simulated particles which mimic the behaviours of self-propelling microorganisms have distinct collective properties which depend on their velocities and bottom-heaviness.

From starling aberrations to self-turbulent fluids, ‘active systems’ encompass a wide family of phenomena in which individual objects propel themselves forward, allowing them to display intriguing collective behaviours. On microscopic scales, they are found in groups of living organisms which move around by squirming, and are aligned with Earth’s gravitational fields due to their bottom-heavy mass distributions. Through research published in EPJ E, Felix Rühle and Holger Stark at the Technical University of Berlin find that depending on their properties, these objects collectively spend most of their time in one of two states, between which some intriguing behaviours can emerge.


K. Bongs
ISSN: 2196-0763 (Electronic Edition)

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