A mathematical model suggests that social groups can behave in unexpected ways when subjected to competing mass media.

Systems that exhibit memory, such as crumpled paper and mechanical metamaterials, can be modeled as a collection of interacting bistable elements that together give rise to complex hysteretic behavior. Using a system of connected rubber balloons as an example, this paper introduces a description of such a system in terms of the geometry of its configuration space.

The mechanical rigidity of discrete materials is often understood in terms of the Maxwell-Calladine index theorem, which relates the emergence of the material’s rigidity to the constraints imposed by each of its components on deformation of their shape. In this paper, a generalization of the theorem is proposed that not only takes into account the geometric constraints of the components, but also the energetic cost of the components to deform. The authors show that this result could be used to design metamaterials with specific responses to external forces.

Run and tumble particles show an alternating sequence of propulsion and reorientation. Here, large deviations are found in the fluctuations of local and occupation times of run and tumble particles in one dimension.

Simplicial complexes are higher-order networks that can sustain topological signals, dynamical variables associated not only to nodes, but also to edges, triangles, and higher-dimensional simplices. The authors show that while odd topological signals, such as edge signals, cannot synchronize globally on unweighted simplicial complexes, they can do so on weighted ones.

This paper describes a study of parametric resonance and symmetries in a mass-spring chain of coupled oscillators. The authors develop a framework which they apply to a spatiotemporally modulated ring of oscillators. They demonstrate that conditions for selective one-way amplification in this ring of oscillators are independent of the functional form of the time modulation.

Plants generally orient their growth against the direction of gravity. Rotating them around an axis perpendicular to gravity can produce more complicated growth shapes that depend on the speed of rotation. The authors model this behavior and find a stable family of three-dimensional dynamic equilibria.

Photon correlation spectroscopy is used to examine microscopic dynamics of Brownian suspensions within small spherical droplets. The authors first validate the setup and then demonstrate the method with a study of the shrinking and swelling of millimeter-sized polymer hydrogel beads. Their space-resolved measurements provide new information on microscopic rearrangements occurring during gel swelling.

The authors introduce a model for B cell affinity maturation, the process by which a B cell acquires specificity for an introduced antigen. They consider how vaccination with two antigens with the same subdominant antigenic region affects the antibody pool. Their results suggest guidelines for preparation of antigen cocktails that generate broadly neutralizing antibodies.

This paper investigates, by means of an analytically solvable one-dimensional model, the dissipation in a turbulent, nearly collisionless plasma. When applying a stochastic, external electric field, it is reported that the generalized entropy of the distribution function cascades from large to small scales in position and velocity space, rendering the stochastic heating irreversible.

This is an investigation of collective motion of fish swimming in the presence of obstacles. The authors analyzed trajectories of zebrafish swimming in a tank with varying densities of pillars. As the density of pillars increased, the experiments exhibited a transition from mostly aligned fish, to fish oriented along the axes of the pillar lattice. The authors considered the relative orientations of two fish and developed a stochastic model, which qualitatively reproduced the experimental data.

A model for coordinated motion of cilia is examined in this work. In this model, wave dynamics of cilia are represented by motions of microspheres elastically bound to circular orbits that are inclined with respect to a no-slip surface. Parameters are explored with analytical studies and simulations. The authors demonstrate traveling waves whose dynamics and direction may be tuned by the elasticity.

Cell adhesion proteins bind the cell membrane to its environment and, at the same time, aggregate into stable clusters. In this paper, the proteins’ sensing of the cell membrane curvature is investigated as a mechanism to stabilize these clusters, predicting the emergence of diverse spatial patterns.

Both the predictive power and the memory storage capability of an artificial neural network called a reservoir computer increase when time delays are added into how the network processes signals, according to a new model.

When injected into a plasma, a proton bunch triggers oscillatory phenomena which can lead to different instability regimes. The authors present experimental evidence of the appearance of the oblique two-stream instability, generating filamentation in the bunch-plasma system, in accordance with theoretical and numerical predictions.

In stochastic thermodynamics, entropy production can be estimated for physical systems with a Markovian description. For realistic situations the full Markovian description may not be accessible, and this paper uses an information-theoretic bound to establish an effective approach for such a scenario.

Scarred functions serve as a basis to calculate eigenstates in quantum chaotic systems, and are useful to study the correspondence between classical and quantum systems in the presence of chaos. In this paper, the authors propose a method, based on a machine learning algorithm, to calculate the scarred functions and corresponding eigenstates of the coupled quartic oscillator, and they report that the algorithm increases accuracy and reduces the execution time.

The distribution of vegetation clusters in a tropical rainforest shows evidence of scale-invariance, suggesting a system close to a critical state. This observation could help to diagnose the health of rainforests and other ecosystems in the face of environmental change.

Odd viscoelastic materials obey fewer symmetries than traditional materials, and as a consequence exhibit unusual features. This paper reports an investigation into the motion of a probe particle in an odd viscoelastic fluid, as a means to explore the consequences of the broken symmetries.

The authors investigate an Ising model of an electorate in which voters are influenced by opinion polls, as well as by their neighbors. The voters hold one of two opposite opinions. The work shows that opinion polls tend to bring about polarized societies, with spatially separated groups having different opinions. The authors discuss factors that influence the voters and note that electorates with greater than a million voters tend to have very close elections.

According to quantum electrodynamics, in very strong electromagnetic fields electron–positron pairs can be created, and with a high density of pairs an electron-positron plasma can form. In this paper, the authors simulate this process for a relativistic electron beam colliding with an intense laser pulse, and identify observations that could be used as diagnostics in future experiments.

Nodes with high connectivity, also called hubs, play a critical role in determining the structural and functional properties of networked systems. The author develops classification methods for directed networks that provide a definition of network hubs, and demonstrates them in a range of example applications.

A soliton gas, a large random ensemble of solitons, does not reach thermodynamic equilibrium because there are infinitely many conserved quantities. The authors report water wave experiments with two interacting jets of soliton gases, and find good quantitative agreement with the predictions of spectral kinetic theory.

In first-passage percolation one is interested in the region that can be reached from an origin within a given time. The authors show that on a square lattice with disorder, the boundary of this region behaves as a fluctuating interface in the Kardar-Parisi-Zhang universality class.

An exclusion process on a ring is studied in this paper, where the presence of a defect particle immersed in a bath of normal particles leads to phase transitions between localized and shock phases. The authors use the functional Bethe ansatz to analytically compute the mean current and, for the first time, the diffusion constant, and report good agreement with Monte Carlo simulations.