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EPJ D Highlight - Frozen-planet states in exotic helium atoms

https://commons.wikimedia.org/wiki/ File:Just_your_average_backyard_ low_energy_anti-proton_ accelerator_(2280414954).jpg, Tom Purves, Toronto, Canada / CC BY (https://creativecommons. org/licenses/by/2.0)

In an elegant study published in EPJ D, physicists from Serbia and Russia have mapped the energy levels and estimated the stability of a ‘frozen planet’ configuration of anti-protonic helium.

Exotic subatomic particles that are like ‘normal’ particles apart from one, opposite, property - such as the positron, which is like an electron but positively rather than negatively charged - are collectively known as antimatter. Direct studies of collisions between particles of matter and those of antimatter using giant facilities such as those at CERN can advance our understanding of the nature of matter. A new study by Tasko Grozdanov from the University of Belgrade in Serbia and Evgeni Solov’ev from the Institute of Nuclear Research near Moscow in Russia has mapped the energy levels of an exotic form of helium produced in this way. This work, which is published in EPJ D, has been described by one commentator as ”... a new jewel in the treasure of scientific achievements in atomic physics theory”.

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Victoria Vitkova joins the EPJ Scientific Advisory Committee (SAC)

Victoria Vitkova

The Scientific Advisory Committee of EPJ is delighted to welcome Professor Victoria Vitkova as the new representative for the Bulgarian Physical Society. She is the head of the Soft Matter Department at the G. Nadjakov Institute of Solid State Physics – Bulgarian Academy of Sciences (ISSP-BAS). Graduated from Sofia University in Quantum Electronics and Laser Physics and in Biophysics and Radiobiology, she defended her PhD in the University of Rennes I, France. Her expertise lies in the field of soft matter physics, rheology of complex fluids and membrane biophysics.

EPJ E Highlight - Distortion isn’t a drag on fluid-straddling particles

Straddling particles deform fluid interfaces.

The drag forces experienced by particles which straddle and distort the interfaces between un-mixable fluids are less influenced by the shape of the distortion than previously thought.

Some intriguing physics can be found at the interfaces between fluids, particularly if they are straddled by particles like proteins or dust grains. When placed between un-mixable fluids such as oil and water, a variety of processes, including inter-molecular interactions, will cause the particles to move around. These motions are characterised by the drag force experienced by the particles, which is itself thought to depend on the extent to which they distort fluid interfaces. So far, however, experiments investigating the intriguing effect haven’t yet fully confirmed the influence of this distortion. In new research published in EPJ E, a team led by Jean-Christophe Loudet at the University of Bordeaux, France, showed that the drag force experienced by fluid-straddling particles is less affected by interface distortion than previously believed.

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EPJ B Highlight - Separations between earthquakes reveal clear patterns

Smaller tremors often follow initial earthquakes. https://upload.wikimedia.org/wiki pedia/commons/3/35/2017_Chia pas_earthquake_map_-_SSN.svg

A new analysis of real earthquake data shows that the similarity between inter-earthquake times and distances displays a distinct relationship with their separation from an initial earthquake.

When large earthquakes occur, seismologists are well aware that subsequent, smaller tremors are likely to take place afterwards in the surrounding geographical region. So far, however, few studies have explored how the similarity between these inter-earthquake times and distances is related to their separation from initial events. In a new study published in EPJ B, researchers led by Min Lin at the Ocean University of China in Qingdao show for the first time that the two values become increasingly correlated the closer they are in time and space to previous, larger earthquakes.

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EPJ D Highlight - A better starting point for exploring entanglement

A clearly quantum non-Gaussian curve

Updated mathematical techniques which can distinguish between two types of ‘non-Gaussian curve’ could make it easier for researchers to study the nature of quantum entanglement.

Quantum entanglement is perhaps one of the most intriguing phenomena known to physics. It describes how the fates of multiple particles can become entwined, even when separated by vast distances. Importantly, the probability distributions needed to define the quantum states of these particles deviate from the bell-shaped, or ‘Gaussian’ curves which underly many natural processes. Non-Gaussian curves don’t apply to quantum systems alone, however. They can also be composed of mixtures of regular Gaussian curves, producing difficulties for physicists studying quantum entanglement. In new research published in EPJ D, Shao-Hua Xiang and colleagues at Huaihua University in China propose a solution to this problem. They suggest an updated set of equations which allows physicists to easily check whether or not a non-Gaussian state is genuinely quantum.

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EPJ B Highlight - Stimulating resonance with two very different forces

Fine-tuning frequencies to achieve resonance.

In some specialised oscillators, two driving forces with significantly different frequencies can work together to make the whole system resonate.

Widely studied in many different fields, ‘nonlinear’ systems can display excessively dramatic responses when the forces which cause them to vibrate are changed. Some of these systems are sensitive to changes in the very parameters which define their driving forces, and can be well described using mathematical equations. These ‘parametric’ oscillators have been widely researched in the past, but so far, few studies have investigated how they will respond to multiple driving forces. In new research published in EPJ B, Dhruba Banerjee and colleagues at Jadavpur University in Kolkata explore this case in detail for the first time. They show that some parametric oscillators can be made to resonate when tuned by a high driving frequency to match a separate, far lower frequency.

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Miguel A.F. Sanjuán joins the EPJ Scientific Advisory Committee (SAC)

Miguel A.F. Sanjuan

The Scientific Advisory Committee of EPJ is delighted to welcome Professor Miguel A.F. Sanjuán as the new representative for the Spanish Royal Physics Society.

Miguel A.F. Sanjuán is a professor of Physics at the University Rey Juan Carlos (URJC) in Madrid, Spain. He is the director of the Nonlinear Dynamics, Chaos and Complex Systems research group at the URJC. He is a member of the Spanish Royal Academy of Sciences, foreign member of the Lithuanian Academy of Sciences and member of the Academia Europaea.

He is an internationally renowned expert in Nonlinear Dynamics, Chaos and Complex Systems and currently Editor General of the Spanish Royal Physics Society.

His expertise will be highly appreciated for the review of and advice on the publishing strategy of EPJ. His membership of the committee will support the visibility of EPJ in his community.

EPJ D Highlight - Deconstructing Schrödinger’s Cat

Cartoon of Schrödinger’s cat, https://commons.wikimedia.org/wiki/ File:Schrodingers_cat.svg (CC BY-SA)

The French theoretical physicist Franck Laloë presents a modification of Schrödinger’s famous equation that ensures that all measured states are unique, helping to solve the problem that is neatly encompassed in the Schördinger’s cat paradox.

The paradox of Schrödinger’s cat – the feline that is, famously, both alive and dead until its box is opened – is the most widely known example of a recurrent problem in quantum mechanics: its dynamics seems to predict that macroscopic objects (like cats) can, sometimes, exist simultaneously in more than one completely distinct state. Many physicists have tried to solve this paradox over the years, but no approach has been universally accepted. Now, however, theoretical physicist Franck Laloë from Laboratoire Kastler Brossel (ENS-Université PSL) in Paris has proposed a new interpretation that could explain many features of the paradox. He sets out a model of this possible theory in a new paper in EPJ D.

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EPJ D Highlight - Breaking up amino acids with radiation

Mass spectra of the fragments obtained from glutamine molecules at different radiation doses.

A new study describes how the amino acid, glutamine, is broken up when bombarded with different doses of electrons. This has implications for cancer radiotherapy and understanding the origin of life.

Small organic molecules, including the amino acids that form the ‘building blocks’ of proteins in living cells, fragment to form ions under the impact of high-energy radiation such as electron beams. A new study published in EPJ D has now shown what happens when electrons collide with one amino acid, glutamine. The extent of the damage and the nature of the ions formed are both affected by the energy of the colliding electrons. This work arises from a collaboration between experimental physicists led by Alexander Snegursky at the Institute of Electron Physics, Uzhgorod, Ukraine and theoreticians led by Jelena Tamuliene at Vilnius University, Vilnius, Lithuania.

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EPJ B Highlight - Ultracold gases in time-dependent magnetic fields

Evolution of the energy spectrum of an ultracold gas under a time-dependent magnetic field. Top left-hand figure (6a), where there is no time dependence, shows the symmetrical ‘Hofstadter’s butterfly’ effect.

The phase transitions of an ultracold gas under a fluctuating magnetic field show interesting patterns, particularly a loss of symmetry in the energy spectrum that is well observed in the disappearance of the ‘Hofstadter’s butterfly’ effect.

It is now technically possible to hold groups of atoms at temperatures that are only a few hundredths of a degree above absolute zero. This so-called ‘ultracold gas’ loaded in an optical lattice is an extremely powerful platform to study quantum mechanical phenomena including phase transitions, due to the excellent control of experimental parameters, such as potential depths, inter-particle interaction strengths and lattice parameters. Sk Noor Nabi from Zhejiang University in Hangzhou, China and colleagues in the Indian Institute of Technology, Guwahati, India, have studied the phase transition between the Mott insulating (MI) and superfluid (SF) states of such a gas in a time-dependent synthetic magnetic field. Their results, published in EPJ B, show that the energy spectrum of the gas loses symmetry in the fluctuating magnetic field. This is observed in the disappearance of the striking ‘Hofstadter’s butterfly’ effect seen in the energy spectrum under a constant magnetic field.

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Editors-in-Chief
G. Moutiers and A. Nicolas
ISSN: 2491-9292 (Electronic Edition)

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