Using $pp$ collision data corresponding to $1.0{\mathrm{fb}}^{-1}$ integrated luminosity collected by the LHCb detector, two narrow states are observed in the ${\mathit{\Lambda }}_b^0{\pi }^{+}{\pi }^{-}$ spectrum with masses $5911.97\pm 0.12(\mathrm{stat})\pm 0.02(\mathrm{syst})\pm 0.66({\mathit{\Lambda }}_b^0\mathrm{mass})\mathrm{MeV}/c^2$ and $5919.77\pm 0.08(\mathrm{stat})\pm 0.02(\mathrm{syst})\pm 0.66({\mathit{\Lambda }}_b^0\mathrm{mass})\mathrm{MeV}/c^2$. The significances of the observations are 5.2 and 10.2 standard deviations, respectively. These states are interpreted as the orbitally excited ${\mathit{\Lambda }}_b^0$ baryons, ${\mathit{\Lambda }}_b^{*0}(5912)$ and ${\mathit{\Lambda }}_b^{*0}(5920)$.

We study vertical jumping in a simple robot comprising an actuated mass-spring arrangement. The actuator frequency and phase are systematically varied to find optimal performance. Optimal jumps occur above and below (but not at) the robot’s resonant frequency $f_0$. Two distinct jumping modes emerge: a simple jump, which is optimal above $f_0$, is achievable with a squat maneuver, and a peculiar stutter jump, which is optimal below $f_0$, is generated with a countermovement. A simple dynamical model reveals how optimal lift-off results from nonresonant transient dynamics.

By means of nuclear spin-lattice relaxation rate $T_1^{-1}$, we follow the spin dynamics as a function of the applied magnetic field in two gapped quasi-one-dimensional quantum antiferromagnets: the anisotropic spin-chain system ${\mathrm{NiCl}}_2\mathrm{\text{−}}4\mathrm{SC}({\mathrm{NH}}_2{)}_2$ and the spin-ladder system $({\mathrm{C}}_5{\mathrm{H}}_{12}\mathrm{N}{)}_2\mathrm{Cu}{\mathrm{Br}}_4$. In both systems, spin excitations are confirmed to evolve from magnons in the gapped state to spinons in the gapless Tomonaga-Luttinger-liquid state. In between, $T_1^{-1}$ exhibits a pronounced, continuous variation, which is shown to scale in accordance with quantum criticality. We extract the critical exponent for $T_1^{-1}$, compare it to the theory, and show that this behavior is identical in both studied systems, thus demonstrating the universality of quantum-critical behavior.

One of the most striking aspects of the 11-year sunspot cycle is that there have been times in the past when some cycles went missing, a most well-known example of this being the Maunder minimum during 1645–1715. Analyses of cosmogenic isotopes (${}^{14}\mathrm{C}$ and ${}^{10}\mathrm{Be}$) indicated that there were about 27 grand minima in the last 11 000 yrs, implying that about $2.7\%$ of the solar cycles had conditions appropriate for forcing the Sun into grand minima. We address the question of how grand minima are produced and specifically calculate the frequency of occurrence of grand minima from a theoretical dynamo model. We assume that fluctuations in the poloidal field generation mechanism and in the meridional circulation produce irregularities of sunspot cycles. Taking these fluctuations to be Gaussian and estimating the values of important parameters from the data of the last 28 solar cycles, we show from our flux transport dynamo model that about $1–4\%$ of the sunspot cycles may have conditions suitable for inducing grand minima.

We observe ultralong-range blueshifted ${\mathrm{Cs}}_2$ molecular states near $n{s}_{1/2}$ Rydberg states in an optical dipole trap, where $31\le n\le 34$. The accidental near degeneracy of $(n-4)l$ and $ns$ Rydberg states for $l>2$ in Cs, due to the small fractional $ns$ quantum defect, leads to nonadiabatic coupling among these states, producing potential wells above the $ns$ thresholds. Two important consequences of admixing high angular momentum states with $ns$ states are the formation of large permanent dipole moments, $\sim 15–100$ Debye, and accessibility of these states via two-photon association. The observed states are in excellent agreement with theory.

Nonequilibrium systems are often characterized by the transport of some quantity at a macroscopic scale, such as, for instance, a current of particles through a wire. The asymmetric simple exclusion process (ASEP) is a paradigm for nonequilibrium transport that is amenable to exact analytical solution. In the present work, we determine the full statistics of the current in the finite size open ASEP for all values of the parameters. Our exact analytical results are checked against numerical calculations using density matrix renormalization group techniques.

The capsids of icosahedral viruses are closed shells assembled from a hexagonal lattice of proteins with fivefold angular defects located at the icosahedral vertices. Elasticity theory predicts that these disclinations are subject to an internal compressive prestress, which provides an explanation for the link between size and shape of capsids. Using a combination of experiment and elasticity theory we investigate the question of whether macromolecular assemblies are subject to residual prestress, due to basic geometric incompatibility of the subunits. Here we report the first direct experimental test of the theory: by controlled removal of protein pentamers from the icosahedral vertices, we measure the mechanical response of so-called “whiffle ball” capsids of herpes simplex virus, and demonstrate the signature of internal prestress locked into wild-type capsids during assembly.

Many active fluid systems encountered in biology are set in total geometric confinement. Cytoplasmic streaming in plant cells is a prominent and ubiquitous example, in which cargo-carrying molecular motors move along polymer filaments and generate coherent cell-scale flow. When filaments are not fixed to the cell periphery, a situation found both in vivo and in vitro, we observe that the basic dynamics of streaming are closely related to those of a nonmotile stresslet suspension. Under this model, it is demonstrated that confinement makes possible a stable circulating state; a linear stability analysis reveals an activity threshold for spontaneous autocirculation. Numerical analysis of the longtime behavior reveals a phenomenon akin to defect separation in nematic liquid crystals and a high-activity bifurcation to an oscillatory regime.

We experimentally demonstrate a class of tractor beams created by coherently superposing coaxial Bessel beams. These optical conveyors have periodic intensity variations along their axes that act as highly effective optical traps for micrometer-scale objects. Trapped objects can be moved selectively upstream or downstream along the conveyor by appropriately changing the Bessel beams’ relative phase. The same methods used to project a single optical conveyor can project arrays of independent optical conveyors, allowing bidirectional transport in three dimensions.

We use a first-principles rational-design approach to identify a previously unrecognized class of ferroelectric materials in the $P{6}_{3}mc$ LiGaGe structure type. We calculate structural parameters, polarization, and ferroelectric well depths both for reported and as-yet hypothetical representatives of this class. Our results provide guidance for the experimental realization and further investigation of high-performance materials suitable for practical applications.

We demonstrate a total charge parity measurement by detecting the radio frequency signal that is reflected by a lumped-element resonator coupled to a single InAs nanowire double quantum dot. The high frequency response of the circuit is used to probe the effects of the Pauli exclusion principle at interdot charge transitions. Even parity charge transitions show a striking magnetic field dependence that is due to a singlet-triplet transition, while odd parity transitions are relatively insensitive to a magnetic field. The measured response agrees well with cavity input-output theory, allowing accurate measurements of the interdot tunnel coupling and the resonator-charge coupling rate $g_c/2\pi \sim 17\mathrm{MHz}$.

Some subtleties and apparent difficulties associated with the notion of spontaneous breaking of time-translation symmetry in quantum mechanics are identified and resolved. A model exhibiting that phenomenon is displayed. The possibility and significance of breaking of imaginary time-translation symmetry is discussed.

We consider the possibility that classical dynamical systems display motion in their lowest-energy state, forming a time analogue of crystalline spatial order. Challenges facing that idea are identified and overcome. We display arbitrary orbits of an angular variable as lowest-energy trajectories for nonsingular Lagrangian systems. Dynamics within orbits of broken symmetry provide a natural arena for formation of time crystals. We exhibit models of that kind, including a model with traveling density waves.

Two years after the discovery of element 117, we undertook a second campaign using the ${}^{249}\mathrm{Bk}+{}^{48}\mathrm{Ca}$ reaction for further investigations of the production and decay properties of the isotopes of element 117 on a larger number of events. The experiments were started in the end of April 2012 and are still under way. This Letter presents the results obtained in 1200 hours of an experimental run with the beam dose of ${}^{48}\mathrm{Ca}$ of about $1.5\times {10}^{19}$ particles. The ${}^{249}\mathrm{Bk}$ target was irradiated at two energies of ${}^{48}\mathrm{Ca}$ that correspond to the maximum probability of the reaction channels with evaporation of three and four neutrons from the excited ${}^{297}117$. In this experiment, two decay chains of ${}^{294}117$ ($3n$) and five decay chains of ${}^{293}117$ ($4n$) were detected. In the course of the long-term work, ${}^{249}\mathrm{Cf}$—the product of decay of ${}^{249}\mathrm{Bk}$ (330 d)—is being accumulated in the target. Consequently, in the present experiment, we also detected a single decay of the known isotope ${}^{294}118$ that was produced during 2002–2005 in the reaction ${}^{249}\mathrm{Cf}({}^{48}\mathrm{Ca},3n){}^{294}118$. The obtained results are compared with the data from previous experiments. The experiments are carried out in the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, using the heavy-ion cyclotron U400.

Spontaneous symmetry breaking can lead to the formation of time crystals, as well as spatial crystals. Here we propose a space-time crystal of trapped ions and a method to realize it experimentally by confining ions in a ring-shaped trapping potential with a static magnetic field. The ions spontaneously form a spatial ring crystal due to Coulomb repulsion. This ion crystal can rotate persistently at the lowest quantum energy state in magnetic fields with fractional fluxes. The persistent rotation of trapped ions produces the temporal order, leading to the formation of a space-time crystal. We show that these space-time crystals are robust for direct experimental observation. We also study the effects of finite temperatures on the persistent rotation. The proposed space-time crystals of trapped ions provide a new dimension for exploring many-body physics and emerging properties of matter.

Aberration-corrected microscopes with subatomic resolution will impact broad areas of science and technology. However, the experimentally observed lifetime of the corrected state is just a few minutes. Here we show that the corrected state is intrinsically unstable; the higher its quality, the more unstable it is. Analyzing the contrast transfer function near optimum correction, we define an “instability budget” which allows a rational trade-off between resolution and stability. Unless control systems are developed to overcome these challenges, intrinsic instability poses a fundamental limit to the resolution practically achievable in the electron microscope.

We measure the temperature-dependent carrier density and resistivity of the topological surface state of thin exfoliated ${\mathrm{Bi}}_2{\mathrm{Se}}_3$ in the absence of bulk conduction. When the gate-tuned chemical potential is near or below the Dirac point, the carrier density is strongly temperature-dependent, reflecting thermal activation from the nearby bulk valence band, while, above the Dirac point, unipolar $n$-type surface conduction is observed with negligible thermal activation of bulk carriers. In this regime, linear resistivity vs temperature reflects intrinsic electron-acoustic phonon scattering. A quantitative comparison with a theoretical transport calculation including both phonon and disorder effects gives the ratio of deformation potential to Fermi velocity $D/\hslash {\nu }_{\mathrm{F}}=4.7{\AA }^{-1}$. This strong phonon scattering in the ${\mathrm{Bi}}_2{\mathrm{Se}}_3$ surface state gives intrinsic limits for the conductivity and charge carrier mobility at room temperature of $\sim 550\mu \mathrm{S}$ per surface and $\sim 10000{\mathrm{cm}}^2/\mathrm{V}\mathrm{s}$.

The core-collapse supernova phenomenon, one of the most explosive events in the Universe, presents a challenge to theoretical astrophysics. Of the large variety of forms of matter present in core-collapse supernova, we focus on the transitional region between homogeneous (uniform) and inhomogeneous (pasta) phases. A three-dimensional, finite temperature Skyrme-Hartree-Fock $(3\mathrm{D}\mathrm{\text{−}}\mathrm{SHF})+\mathrm{BCS}$ calculation yields, for the first time fully self-consistently, the critical density and temperature of both the onset of the pasta in inhomogeneous matter, consisting of neutron-rich heavy nuclei and a free neutron and electron gas, and its dissolution to a homogeneous neutron, proton, and electron liquid. We also identify density regions for different pasta formations between the two limits. We employ four different forms of the Skyrme interaction, SkM*, SLy4, NRAPR, and SQMC700 and find subtle variations in the low density and high density transitions into and out of the pasta phase. One new stable pasta shape has been identified, in addition to the classic ones, on the grid of densities and temperatures used in this work. Our results are critically compared to recent calculations of pasta formation in the quantum molecular dynamics approach and Thomas-Fermi and coexisting phase approximations to relativistic mean-field models.

The passage of muons through matter is dominated by the Coulomb interaction with electrons and nuclei. The interaction with the electrons leads to continuous energy loss and stopping of the muons. The interaction with nuclei leads to angle “diffusion.” Two muon-imaging methods that use flux attenuation and multiple Coulomb scattering of cosmic-ray muons are being studied as tools for diagnosing the damaged cores of the Fukushima reactors. Here, we compare these two methods. We conclude that the scattering method can provide detailed information about the core. Attenuation has low contrast and little sensitivity to the core.

Friction is always present when surfaces in contact are set in motion. In this work I describe how a precise, active control of the global friction is possible by adjusting the local molecular conformation of a polyelectrolyte coating via the application of an alternating electric field. The intensity of the applied field determines the degree of interpenetration between polymer brushes in contact, regulating chain stretching while sliding, which is the process at the origin of the global friction. The dynamics of the problem is controlled by the relaxation times of the polyelectrolyte.