EPJ Plus Highlight - Laser-ranged satellite measurement now accurately reflects Earth's tidal perturbations
- Published on 14 February 2018
The most precise ever laser satellite measurement method provides new clues to relativity
Tides on Earth have a far-reaching influence, including disturbing satellites’ measurements by affecting their motion. This disturbance can be studied using a model for the gravitational potential of the Earth, taking into account the fact that Earth’s shape is not spherical. The LAser RElativity Satellite (LARES), is the best ever relevant test particle to move in the Earth’s gravitational field. In a new study published in EPJ Plus, LARES proves its efficiency for high-precision probing of General Relativity and fundamental physics. By studying the Earth’s tidal perturbations acting on the LARES, Vahe Gurzadyan from the Center for Cosmology and Astrophysics at Yerevan State University, Armenia, and colleagues demonstrate the value of laser-range satellites for high-precision measurements.
- Published on 13 February 2018
The papers published in this Focus Point evidence the broad range of interests pursued by the Italian community active in the field of Planetary Sciences.
Although this selection of papers can by no means be considered to exhaustively represent the fields of interest of the community, many points of interests and activities are included, from PI activitities in Planetary Space Missions, both from ESA and NASA programmes (such as Bepi Colombo and Juno) to the study of physical and dynamical properties of minor bodies to the geological study of planetary surfaces to the study of atmospheres to cosmogeophysical studies of meteorites.
The Italian Research Institutes, Observatories and Universities hosting research groups active in Planetary Sciences are based in different regional locations on the Italian territory as also shown by the selection of articles published in this Focus Point, and are evidence of a growing interest of the Astrophysical Community in Planetary Sciences and of a rapid growth in the number of topics investigated and in the number of scientists involved.
- Published on 26 January 2018
How magnetic force acts on charged subatomic particles near the speed of light
Current textbooks often refer to the Lorentz-Maxwell force governed by the electric charge. But they rarely refer to the extension of that theory required to explain the magnetic force on a point particle. For elementary particles, such as muons or neutrinos, the magnetic force applied to such charges is unique and immutable. However, unlike the electric charge, the magnetic force strength is not quantised. For the magnetic force to act on them, the magnetic field has to be inhomogeneous. Hence this force is more difficult to understand in the context of particles whose speed is near the speed of light. Moreover, our understanding of how a point-particle carrying a charge moves in presence of an inhomogenous magnetic field relied until now on two theories that were believed to differ. The first stems from William Gilbert's study of elementary magnetism in 16th century, while the second relies on André-Marie Ampère electric currents. In a new study just published in EPJ C, the authors Johann Rafelski and colleagues from the University of Arizona, USA, succeeded in resolving this ambiguity between Ameperian and Gilbertian forms of magnetic force. Their solution makes it possible to characterise the interaction of particles whose speed is close to the speed of light in the presence of inhomogeneous electromagnetic fields.
- Published on 26 January 2018
Understanding the dynamics of message transmission in networks leads to identification of key individuals spreading news and viruses in epidemics
Social networks, such as Twitter, thrive on key influencers spreading news. Like information, epidemics also spread from key individuals. To identify the most influential actors in such networks, many studies have, until now, focused on ranking the influence of individual nodes. But these methods are not accurate enough to single out influential spreaders because they fail to take into account the spreading dynamics. Now, Byungjoon Min from the Institute of Interdisciplinary Physics and Complex Systems, Balearic Island University, Palma de Mallorca, Spain, has calculated for the first time the expected size of epidemic outbreaks when spreading originates from a single seed. In a study published in EPJ B, Min accurately predicts the influence of spreaders in such networks. Applications include viral marketing, efficient immunisation strategies, and identifying the most influential actors in our society.
- Published on 26 January 2018
It is with great pleasure that we announce that Professor Kai Bongs from the University of Birmingham, UK, has been appointed Editor-in-Chief of EPJ Quantum Technology.
Prof. Bongs is the director of the UK National Quantum Technology Hub in Sensors and Metrology, a consortium of researchers from 11 universities, NPL and over 120 companies, which focuses in translating quantum science enabled precision measurements with cold atoms into technology and economic benefit. He has been working in the field of cold atoms for over 20 years. After studying Physics up to his PhD in the group of Prof. Wolfgang Ertmer at the University of Hannover and a postdoctoral appointment on atom interferometry in the group of Mark Kasevich at Yale University, he did his Habilitation on quantum gas mixtures working with Prof. Klaus Sengstock at the University of Hamburg. Since 2007 he holds a chair at the University of Birmingham heading the group of quantum matter and directing the Birmingham part of the Midlands Ultracold Atom Research Centre, MUARC. His research achievements have been recognised by a Royal Society Wolfson Research Merit Award.
Prof. Bongs takes on this position after the founding Editor, Prof. Gerard Milburn stepped down at the end of 2017. We take this opportunity to show our gratitude to Prof. Milburn for his role in bringing EPJ Quantum Technology to life and for his hard work and leadership in the past four years.
- Published on 23 January 2018
When colloidal particles find themselves in a temperature gradient they move in response to it, in some cases toward the hotter some toward the cooler side, depending on the specific physical chemistry of the colloid and the solvent surrounding it. This process, called thermophoresis, is generally regarded as a phoretic phenomenon: the thermal motion of a colloid is mainly driven by local hydrodynamic stresses in the surrounding liquid. However a complete and unique theoretical description of thermophoresis has been lacking.
- Published on 19 January 2018
EPJ is pleased to announce significant changes concerning the editorial structure of EPJ A. Following the continuous growth and broadening of the journal’s scope over the past few years, the theory section has now been divided into Theory I (Nuclear Physics) and Theory II (Hadron Physics and Quark Matter). Theory I is headed by Prof. Thomas Duguet, who has been newly appointed for this position, while Theory II continues to be headed by Prof. Tamás Biró. Further, and with immediate effect, Prof. Maria Jose Garcia Borge has been appointed Editor-in-Chief for the Experimental Physics section of the journal.
- Published on 09 January 2018
Study of the dynamic properties of biological membranes reveals new anomalous behaviour under specific circumstances
How biological membranes - such as the plasma membrane of animal cells or the inner membrane of bacteria - fluctuate over time is not easy to understand, partly because at the sub-cellular scale, temperature-related agitation makes the membranes fluctuate constantly; and partly because they are in contact with complex media, such as the cells’ structuring element, the cytoskeleton, or the extra-cellular matrix. Previous experimental work described the dynamics of artificial, self-assembled polymer-membrane complexes, embedded in structured fluids. For the first time, Rony Granek from Ben-Gurion University of The Negev, and Haim Diamant from Tel Aviv University, both in Israel, propose a new theory elucidating the dynamics of such membranes when they are embedded in polymer networks. In a new study published in EPJ E, the authors demonstrate that the dynamics of membrane undulations inside such a structured medium are governed by distinctive, anomalous power laws.
- Published on 21 December 2017
New study shows that two seemingly diverging theories of ever-increasing disorder, known as entropy, can be tested against each other experimentally in the smallest possible systems
Have you ever tried turning the spoon back after stirring jam into a rice pudding? It never brings the jam back into the spoon. This ever-increasing disorder is linked to a notion called entropy. Entropy is of interest to physicists studying the evolution of systems made up of multiple identical elements, like gas. Yet, how the states in such systems should be counted is a bone of contention. The traditional view developed by one of the fathers of statistical mechanics, Ludwig Boltzmann - who worked on a very large number of elements - is opposed to the seemingly disjointed theoretical perspective of another founding scientists of the discipline, Willard Gibbs, who describes systems with a very small number of elements. In a new study published in EPJ Plus, Loris Ferrari from the University of Bologna, Italy, demystifies this clash between theories by analysing the practical consequences of Gibbs’ definition in two systems of a well-defined size. Ferrari speculates about the possibility that, for certain quantities, the differences resulting from Boltzmann's and Gibbs' approach can be measured experimentally.
- Published on 21 December 2017
Atomic Spin Squeezing: not the Olympic sport of your dreams, but a way of enhancing measurement reliability at the quantum scale
Noise: it affects us all by distracting us. Noise also occurs at the quantum scale and can e.g. interfere with the measurements of atomic fountain clocks or with quantum information processing. This is because at that scale, there are effects that don't exist at larger scales. As such, finding ways to reduce quantum noise can enhance the precision of measurement in the examples given above. Now a team of physicists including Aranya Bhattacherjee from Jawaharlal Nehru University, New Delhi, India and colleagues are investigating ways of improving the analysis of quantum noise measurement in the case of spectroscopic investigations; their preliminary findings were released in a study in EPJ D. This method, called atomic spin squeezing, works by redistributing the uncertainty unevenly between two components of spin in these measurements systems, which operate at the quantum scale. The spin represents a degree of freedom of the quantum particles involved. Thus, the spin component with reduced uncertainty becomes more precise in delivering its measurement - as the two are inversely correlated. Potential applications include the development of future quantum networks.