Volume 13 Issue 5, May 2017

A recent burst of activity in applying machine learning to tackle fundamental questions in physics suggests that associated techniques may soon become as common in physics as numerical simulations or calculus.

There is growing evidence for the kinetics of homogeneous nucleation being a multi-step process. Colloid experiments and simulations now suggest that heterogeneous nucleation is no exception.

The spectroscopic observations of the very early stages of a supernova provide a glimpse into its environment prior to the explosion.

Over the past decade, remarkable progress has occurred in the physics of closed quantum systems away from equilibrium, culminating in the recent experimental realization of so-called time crystals. This Progress Article surveys these developments.

The success of machine learning techniques in handling big data sets proves ideal for classifying condensed-matter phases and phase transitions. The technique is even amenable to detecting non-trivial states lacking in conventional order.

A neural-network technique can exploit the power of machine learning to mine the exponentially large data sets characterizing the state space of condensed-matter systems. Topological transitions and many-body localization are first on the list.

Plasma optics enables the manipulation of highly intense laser beams. Now, plasma holograms, involving the creation of a modulated plasma surface on a solid target, are reported — for example, plasma hologram fork gratings produce optical vortices.

A demonstration of switching between solitons of different chirality in a one-dimensional electronic system shows how topological excitations can be used to realize non-trivial algebraic operations.

Experiments show how domain walls can act as reservoirs of exchange energy that can be used to controllably launch or detect spin waves in ferromagnetic nanowires.

A detailed analysis of low-temperature torsional oscillation measurements on two-dimensional ⁴He reveals evidence for intertwined superfluid and density wave order in this system.

Many-body localization, which exhibits a fascinating interplay between disorder and interactions, can be studied using ultracold atoms in a quasiperiodic chain. Adding periodic driving makes things even more interesting.

Combining synthetic magnetism and controlled dissipation, researchers created an optomechanical device in which photons and phonons are coupled, enabling non-reciprocal (asymmetric) photon transport and directional amplification.

An experimental and theoretical study of the real-time dynamics in strong-field ionization of xenon atoms reveals the previously unknown role of transient ground-state polarization.

Recent developments in advanced light sources have made it possible to transiently alter the electronic properties of materials by exciting specific atomic vibrations in solids. This study provides a theoretical framework for these experiments.

Lattice gauge theories are notoriously hard to analyse at finite fermion density, due to the so-called fermion sign problem. A study now shows this can be circumvented for the case of Ising gauge theories.

Two challenging questions related to the quantum Hall effect (QHE) are how edge reconstruction works and where the current flows. A new model now gives the answer for two types of QHE states — two separate downstream chiral edge channels are involved.

Controlled wave propagation in disordered media is a challenge because of scattering processes. Now it is shown that for speckled targets much larger than the wavelength, long-range correlations between the speckles enhance wave propagation control.

Controlled crystal growth can be achieved by initiating nucleation on a substrate — but the mechanisms at play are still poorly understood. Experiments and simulations now reveal conditions for the growth of defect-free crystals of charged colloids.

Type II supernova explosions are common, but our understanding of such events is not complete. Such an event was observed just three hours after the explosion started, providing important information about the early stages.

Alberto Moscatelli surveys a series of experiments on the electron g-factor that marked the departure from the Dirac equation and contributed to the development of quantum electrodynamics.