We describe the behavior of 5-dimensional black strings, subject to the Gregory-Laflamme instability. Beyond the linear level, the evolving strings exhibit a rich dynamics, where at intermediate stages the horizon can be described as a sequence of 3-dimensional spherical black holes joined by black string segments. These segments are themselves subject to a Gregory-Laflamme instability, resulting in a self-similar cascade, where ever-smaller satellite black holes form connected by ever-thinner string segments. This behavior is akin to satellite formation in low-viscosity fluid streams subject to the Rayleigh-Plateau instability. The simulation results imply that the string segments will reach zero radius in finite asymptotic time, whence the classical space-time terminates in a naked singularity. Since no fine-tuning is required to excite the instability, this constitutes a generic violation of cosmic censorship.

The spatial fluctuations of deformation are studied in the creep in Andrade’s power law and the logarithmic phases, using paper samples. Measurements by the digital image correlation technique show that the relative strength of the strain rate fluctuations increases with time, in both creep regimes. In the Andrade creep phase characterized by a power-law decay of the strain rate ${ϵ}_t\sim t^{-\theta }$, with $\theta \approx 0.7$, the fluctuations obey $\Delta {ϵ}_t\sim t^{-\gamma }$, with $\gamma \approx 0.5$. The local deformation follows a data collapse appropriate for a phase transition. Similar behavior is found in a crystal plasticity model, with a jamming or yielding transition.

Mechanical properties of nanoconfined water layers are still poorly understood and continue to create controversy, despite their importance for biology and nanotechnology. We report on dynamic nanomechanical measurements of water films compressed to a few single molecular layers. We show that the mechanical properties of nanoconfined water layers change significantly with their dynamic state. In particular, we observed a sharp transition from viscous to elastic response even at extremely slow compression rates, indicating that mechanical relaxation times increase dramatically once water is compressed to less than 3–4 molecular layers.

The operation principles of nanoscale devices are based upon both electronic and mechanical properties of materials. Because these properties can be coupled, they need to be investigated simultaneously. At this moment, however, the electronic structure calculations with custom-made long-range mechanical distortions are impossible, or expensive at best. Here we present a unified formalism to solve exactly the electronic structures of nanomaterials with versatile distortions. We illustrate the formalism by investigating twisted armchair graphene nanoribbons with the least possible number of atoms. Apart from enabling versatile material distortions, the formalism is capable of reducing computational costs orders of magnitude in various areas of science and engineering.

We demonstrate that a purely ideal mechanism, originating in the space-time distortion caused by the demands of special relativity, can break the topological constraint (leading to helicity conservation) that would forbid the emergence of a magnetic field (a generalized vorticity) in an ideal nonrelativistic dynamics. The new mechanism, arising from the interaction between the inhomogeneous flow fields and inhomogeneous entropy, is universal and can provide a finite seed even for mildly relativistic flows.

We derive the Markovian description for the nonequilibrium Brownian motion of a heated nanoparticle in a simple solvent with a temperature-dependent viscosity. Our analytical results for the generalized fluctuation-dissipation and Stokes-Einstein relations compare favorably with measurements of laser-heated gold nanoparticles and provide a practical rational basis for emerging photothermal tracer and nanoparticle trapping and tracking techniques.

Using a three-frequency one-dimensional kicked rotor experimentally realized with a cold atomic gas, we study the transport properties at the critical point of the metal-insulator Anderson transition. We accurately measure the time evolution of an initially localized wave packet and show that it displays at the critical point a scaling invariance characteristic of this second-order phase transition. The shape of the momentum distribution at the critical point is found to be in excellent agreement with the analytical form deduced from the self-consistent theory of localization.

We apply polarization resolved photoluminescence spectroscopy to measure the spin polarization of a two dimensional electron gas in perpendicular magnetic field. We find that the splitting between the ${\sigma }^{+}$ and ${\sigma }^{-}$ polarizations exhibits a sharp drop at $\nu =5/2$ and is equal to the bare Zeeman energy, which resembles the behavior at even filling factors. We show that this behavior is consistent with filling factor $\nu =5/2$ being unpolarized.

From our investigation of magnetoelectric properties of a multiferroic phase in ${\mathrm{Eu}}_{0.75}{\mathrm{Y}}_{0.25}{\mathrm{MnO}}_3$ competing with a weak-ferromagnetic phase in magnetic fields, we found intriguing hysteretic behaviors of physical properties with variation of temperature and magnetic field. These hysteretic behaviors arise from the kinetic arrest (dearrest) processes of the first-order multiferroic-weak-ferromagnetic transition, resulting in frozen (melted) magnetoelectric glass states with coexisting two phases. Tipping the delicate balance of two competing phases by applying electric and magnetic fields leads to a remarkable control of magnetization and electric polarization.

A scanning tunneling microscope (STM) has been equipped with a nanoscale force sensor and signal transducer composed of a single ${\mathrm{D}}_2$ molecule that is confined in the STM junction. The uncalibrated sensor is used to obtain ultrahigh geometric image resolution of a complex organic molecule adsorbed on a noble metal surface. By means of conductance-distance spectroscopy and corresponding density functional calculations the mechanism of the sensor and transducer is identified. It probes the short-range Pauli repulsion and converts this signal into variations of the junction conductance.

We report quasielastic neutron scattering studies of ${\mathrm{H}}_2\mathrm{\text{−}}{\mathrm{D}}_2$ diffusion in a carbon molecular sieve, demonstrating remarkable quantum effects, with the heavier isotope diffusing faster below 100 K, confirming our recent predictions. Our transition state theory and molecular dynamics calculations show that while it is critical for this effect to have narrow windows of size comparable to the de Broglie wavelength, high flux requires that the energy barrier be reduced through small cages. Such materials will enable novel processes for kinetic molecular sieving of hydrogen isotopes.

Even below its normal melting temperature, ice melts when subjected to high pressure and refreezes once the pressure is lifted. A classic demonstration of this regelation phenomenon is the passing of a thin wire through a block of ice when sufficient force is exerted. Here we present a molecular-dynamics study of a nanowire cutting through ice to unravel the molecular level mechanisms responsible for regelation. In particular, we show that the transition from a stationary to a moving wire due to increased driving force changes from symmetric and continuous to asymmetric and discontinuous as a hydrophilic wire is replaced by a hydrophobic one. This is explained at the molecular level in terms of the wetting properties of the wire.

Partial oxidation of methanol to formaldehyde over Cu(110) is one of the most studied catalytic reactions in surface science, yet the local site of the reaction intermediate, methoxy, remains unknown. Using a combination of experimental scanned-energy mode photoelectron diffraction, and density functional theory, a consistent structural solution is presented in which all methoxy species occupy twofold coordinated “short-bridge” adsorption sites. The results are consistent with previously-published scanning tunnelling microscopy images and theoretical calculations of the reaction mechanism.

Functionalizing graphene was recently shown to have a dramatic effect on the electronic properties of this material. Here we investigate spatial ordering of adatoms driven by the RKKY-type interactions. In the ordered state, which arises via a Peierls-instability-type mechanism, the adatoms reside mainly on one of the two graphene sublattices. Bragg scattering of electron waves induced by sublattice symmetry breaking results in a band gap opening, whereby Dirac fermions acquire a finite mass. The band gap is found to be immune to the adatoms’ positional disorder, with only an exponentially small number of localized states residing in the gap. The gapped state is stabilized in a wide range of electron doping. Our findings show that controlled adsorption of adatoms or molecules provides a route to engineering a tunable band gap in graphene.

We introduce and characterize a first-order model for a generic class of colloidal particles that have a preferred spherical shape but can undergo deformations while always maintaining hard-body interactions. The model consists of hard spheres that can continuously change shape at fixed volume into prolate or oblate ellipsoids of revolution, subject to an energetic penalty. The severity of this penalty is specified by a single parameter that determines the flexibility of the particles. The deformable hard spheres crystallize at higher packing fractions than rigid hard spheres, have a narrower solid-fluid coexistence region and can reach high densities by a second transition to an orientationally ordered crystal.

In the quantum regime information can be copied with only a finite fidelity. This fidelity gradually increases to 1 as the system becomes classical. In this Letter we show how this fact can be used to directly measure the amount of radiated power. We demonstrate how these principles can be used to build a practical primary standard.

We measure the charge asymmetry $A\equiv (N^{++}-N^{--})/(N^{++}+N^{--})$ of like-sign dimuon events in $6.1{\mathrm{fb}}^{-1}$ of $p\overline{p}$ collisions recorded with the D0 detector at a center-of-mass energy $\sqrt{s}=1.96\mathrm{TeV}$ at the Fermilab Tevatron collider. From $A$ we extract the like-sign dimuon charge asymmetry in semileptonic $b$-hadron decays: $A_{\mathrm{sl}}^b=-0.00957\pm 0.00251(\mathrm{stat})\pm 0.00146(\mathrm{sys})$. It differs by 3.2 standard deviations from the standard model prediction $A_{\mathrm{sl}}^b(\mathrm{SM})=(-{2.3}_{-0.6}^{+0.5})\times {10}^{-4}$, and provides first evidence of anomalous $CP$ violation in the mixing of neutral $B$ mesons.

Dramatic eruption of an arched magnetic flux rope in a large ambient plasma has been studied in a laboratory experiment that simulates coronal loops. The eruption is initiated by laser generated plasma flows from the footpoints of the rope that significantly modify the magnetic-field topology and link the magnetic-field lines of the rope with the ambient plasma. Following this event, the flux rope erupts by releasing its plasma into the background. The resulting impulse excites intense magnetosonic waves that transfer energy to the ambient plasma and subsequently decay.

We present a quantum-accurate multiscale study of how hydrogen-filled discoidal “platelet” defects grow inside a silicon crystal. Dynamical simulations of a 10-nm-diameter platelet reveal that ${\mathrm{H}}_2$ molecules form at its internal surfaces, diffuse, and dissociate at its perimeter, where they both induce and stabilize the breaking up of highly stressed silicon bonds. A buildup of ${\mathrm{H}}_2$ internal pressure is neither needed for nor allowed by this stress-corrosion growth mechanism, at odds with previous models. Slow platelet growth up to micrometric sizes is predicted as a consequence, making atomically smooth crystal cleavage possible in implantation experiments.

We obtained an unprecedentedly large number of $s$-wave neutron widths through $\mathcal{R}$-matrix analysis of neutron cross-section measurements on enriched Pt samples. Careful analysis of these data rejects the validity of the Porter-Thomas distribution with a statistical significance of at least 99.997%.