Volume 16 Issue 4, April 2020

Artificial neural networks now allow the dynamics of supercooled liquids to be predicted from their structure alone in an unprecedented way, thus providing a powerful new tool to study the physics of the glass transition.

Using the coupling between electrons and phonons in a Weyl semimetal allows the detection of the dynamical chiral magnetic effect.

A small twist to a field theory, a giant leap for its phenomenology. Waiving the standard requirement of energy conservation in linear elasticity unravels unexpected mechanical behaviour that has previously been overlooked.

Experiments carried out at the National Ignition Facility show that the degree of degeneracy can be varied for an electron plasma. Partially degenerate electron plasmas make up most of the interiors of low mass stars, brown dwarfs and giant planets.

Complex contagions — for example when ideas spread across a network — are thought to be different from the simple contagions observed for infections. Simple contagions are now shown to exhibit a key macroscopic characteristic of complex behaviour when they interact.

Cooling of trapped ions with a neutral buffer gas makes the study of atom–ion hybrid systems possible in the quantum regime. The new record low achieved opens the door to numerous opportunities, including full control over the atom–ion interactions.

Proposals for the particle physics programmes in the United States and Asia are discussed; mainly the International Linear Collider in Japan, the Circular Electron–Positron Collider in China and accelerator-based long-baseline neutrino experiments in the United States.

The Compact Linear Collider is a proposed high-luminosity electron–positron collider that can reach TeV-scale energies. Its accelerator design and physics programme, mainly focusing on precision measurements and new physics searches, are discussed.

Within the Physics Beyond Collider programme, complementary methods to high-energy frontier particle colliders to investigate the physics of elementary particles and their interactions are studied.

The Future Circular Colliders are proposed as a future step after the Large Hadron Collider has stopped running. The first stage foresees collision of electron–positron pairs before a machine upgrade to allow proton–proton operation.

The STAR collaboration reports a measurement of the mass difference and binding energy of the hypertriton and its antiparticle. This work constrains the hyperon–nucleon interaction and allows us to test the CPT theorem in a nucleus with strangeness.

Cooling an atom–ion hybrid system and bringing it into the quantum regime is challenging owing to the unavoidable heating caused by atom–ion collisions. Here a new record low is achieved in such a system, and the quantum effect starts to manifest.

Light-induced deformations in a film of superfluid helium covering an optical microresonator can greatly enhance Brillouin interactions, enabling strong coupling between counter-propagating modes as well as Brillouin lasing.

In a process dubbed elastic ripening, compressive stresses in a polymer network are shown to suppress phase separation of the solvent that swells it, stabilizing mixtures well beyond the liquid–liquid phase separation boundary.

Knowledge of the spreading mechanisms of contagions is important for understanding a range of epidemiological and social problems. A study now shows that so-called simple and complex contagions cannot be told apart if there is more than one simple contagion traversing the population at the same time.

Transitions between non-degenerate and degenerate plasma are observed in laser-driven implosions of cryogenic capsules at the National Ignition Facility. The observed partially degenerate regime is relevant to the physics of young brown dwarfs.

The phenomenon of many-body localization gives rise to entirely new phases of quantum matter when it is driven away from equilibrium. A numerical study now shows that one of these phases—the discrete time crystal—can also occur in a classical spin chain.

The physics that underlies the glass transition is both subtle and non-trivial. A machine learning approach based on graph networks is now shown to accurately predict the dynamics of glasses over a wide range of temperatures, pressures and densities.

Percolation transitions underpin a generic class of phenomena associated with the degree of connectedness in networks. A detailed numerical study now uncovers a universal scaling in the size of the largest cluster identified in such percolation models.

The hybridized modes of an asymmetric plasmonic dimer show avoided crossing of both the real and imaginary parts. This can lead to plasmonic exceptional points, which are used for biosensing with very high sensitivity.

Herbertsmithite is an experimental realization of the so-called quantum kagome antiferromagnet, a system that is predicted to host a spin liquid state down to zero temperature. Detailed NMR measurements now confirm that this is the case, and that its ground state is indeed gapless.

Active, non-conservative interactions can give rise to elastic moduli that are forbidden in equilibrium and enter the antisymmetric part of the stiffness tensor. The resulting solids function as distributed elastic engines that can perform work on their surroundings through quasistatic strain cycles.

The relationship between the dynamics and spatial order of active matter gives rise to a rich phenomenology that is not fully understood. A study of bacteria swimming in a patterned liquid crystalline environment is a case in point, and provides a way to streamline the chaotic movements of swimming bacteria into polar jets.

Groups of fish tend to move in an organized fashion. Here the authors investigate the behaviour of schools of freshwater fish and find that schooling is induced by noise; the smaller the group size, the greater the noise and hence the greater the alignment.

Watching the ocean’s ebb and flow may be soothing, but the history of the sverdrup unit for ocean flow is more turbulent. Tor Eldevik and Peter Mosby Haugan recount an oceanographic journey reaching high tide with Harald Ulrik Sverdrup and his unit.