- Published on 29 October 2014
The Casimir electromagnetic fluctuation forces across plasmas are analogous to so-called weak nuclear interaction forces, as new findings showA new theoretical work establishes a long-sought-after connection between nuclear particles and electromagnetic theories. Its findings suggests that there is an equivalence between generalised Casimir forces and what are referred to as weak nuclear interactions between protons and neutrons. The Casimir forces are due to the quantisation of electromagnetic fluctuations in vacuum, while the weak nuclear interactions are mediated by subatomic scale particles, originally called mesons by Yukawa. These findings by Barry Ninham from the Australian National University, in Canberra, and European colleagues, have now been published in EPJ D.
- Published on 15 October 2014
A new theoretical study demonstrates for the first time that quantum holograms could be a candidate for becoming quantum information memory
Russian scientists have developed a theoretical model of quantum memory for light, adapting the concept of a hologram to a quantum system. These findings are included in study just published in EPJ D, by Anton Vetlugin and Ivan Sokolov from St. Petersburg State University in Russia. The authors demonstrate for the first time, that it is theoretically possible to retrieve, on demand, a given portion of the stored quantised light signal of a holographic image—set in a given direction in a given position in time sequence.
- Published on 14 October 2014
In this EPJ D colloquium paper, the authors review a cross-section of recent results relating to low-energy positron scattering from atomic targets, and present a comparison of the latest measurements and calculations for positron collisions with the noble gases, together with a brief update on the newest studies addressing other atomic targets. In particular, they provide an overview of the work that has been done in examining elastic scattering, positronium formation, direct and total ionisation, as well as total scattering, at typical energies ranging from 0.1 eV to a few hundred eV.
- Published on 29 September 2014
Improved theoretical model of photoabsorption of nitrous oxide matters because its by-product, nitric oxide, is involved in the catalytic destruction of stratospheric ozone
New theoretical physics models could help us better grasp the atmospheric chemistry of ozone depletion. Indeed, understanding photoabsorption of nitrous oxide (N2O)-- a process which involves the transfer of the energy of a photo to the molecule--matters because a small fraction of N2O reacts with oxygen atoms in the stratosphere to produce, among other things, nitric oxide (NO). The latter participates to the catalytic destruction of ozone (O3). Now, new theoretical work unveils the actual dynamic of the photoabsorption of nitrous oxide (N2O) molecules. These findings by Mohammad Noh Daud from the University of Malaya, Kuala Lumpur in Malaysia, have just been published in EPJ D. The work has led to new calculations of the probability of an absorption process taking place, also referred to as absorption cross section, which confirm experimental results.
- Published on 29 September 2014
Bohmian mechanics provides an explanation of quantum phenomena in terms of point particles guided by wave functions. This EPJ D review focuses on the formalism of non-relativistic Bohmian mechanics, rather than its interpretation, and although the Bohmian and standard quantum mechanical theories have different formalisms, they both yield exactly the same predictions for all phenomena.
- Published on 25 September 2014
Over the past 15 years, the density matrix renormalisation group (DMRG) has become increasingly important for ab initio quantum chemistry. Its underlying wavefunction ansatz, the matrix product state (MPS), is a low-rank decomposition of the full configuration interaction tensor. The virtual dimension of the MPS, viz. the rank of the decomposition, controls the size of the corner of the many-body Hilbert space that can be reached with the ansatz, and can be systematically increased until numerical convergence is reached. The MPS ansatz naturally captures exponentially decaying correlation functions, and the DMRG therefore works extremely well for noncritical one-dimensional systems.
- Published on 31 July 2014
A new theoretical study elucidates mechanisms that could help in producing coherent radiations, and could ultimately help to achieve high-contrast images of biological samples
Ever heard of the water window? It consists of radiations in the 3.3 to 4.4 nanometre range, which are not absorbed by the water in biological tissues. New theoretical findings predict a novel way of achieving coherent radiations within the water window. These could be the basis of an optimal technique to obtain a high-contrast image of the biological samples or to be used in high-precision spectroscopy. Now, a new theoretical study identifies the physical mechanism needed to efficiently generate the harmonic radiations - which are multiples of an incoming laser’s frequency - at high laser intensities that occur beyond the saturation threshold of atoms and molecules. These findings, aimed at improving conventional methods of coherent radiation production to reach the water window, were recently published in the EPJ D by José Pérez-Hernández from the Centre for Pulsated Laser, CLPU, in Salamanca, Spain, and colleagues.
- Published on 21 July 2014
The seminal 1914 experiment of James Franck and Gustav Hertz provided a graphic demonstration of the quantisation properties of atoms, and thereby laid the foundations of modern atomic physics. This EPJ D colloquium revisits the experiment on the occasion of its Centenary and compares the traditional and modern interpretations, as well as highlighting the link between microscopic processes, which are governed by the laws of quantum mechanics, and macroscopic phenomena, as observed in the laboratory.
- Published on 17 July 2014
In this EPJ D topical review, the authors present a systematic study of gas breakdown potentials. An analysis of the key elementary processes involved in low-current low-pressure discharges is given, with the aim of illustrating how such discharges are used to determine swarm parameters and how such data may be applied to the modeling of discharges.
- Published on 30 June 2014
New study provides proof of the validity of a filtering device for ultra-cold neutral atoms based on tunnelling
Techniques for controlling ultra-cold atoms travelling in ring traps currently represent an important research area in physics. A new study published in EPJ D gives a proof of principle, confirmed by numerical simulations, of the applicability to ultra-cold atoms of a very efficient and robust transport technique called spatial adiabatic passage (SAP). Yu Loiko from the University of Barcelona, Spain, and colleagues have, for the first time, applied SAP to inject, extract, and filter the velocity of neutral atoms from and into a ring trap. Such traps are key to improving our understanding of phenomena involving ultra-cold atoms, which are relevant to high-precision applications such as atom optics, quantum metrology, quantum computation, and quantum simulation.