High resolution, fully kinetic, three dimensional (3D) simulation of collisionless plasma turbulence shows the development of turbulence characterized by sheetlike current density structures spanning a range of scales. The nonlinear evolution is initialized with a long wavelength isotropic spectrum of fluctuations having polarizations transverse to an imposed mean magnetic field. We present evidence that these current sheet structures are sites for heating and dissipation, and that stronger currents signify higher dissipation rates. The analyses focus on quantities such as $\mathbf{J}·\mathbf{E}$, electron, and proton temperatures, and conditional averages of these quantities based on local electric current density. Evidently, kinetic scale plasma, like magnetohydrodynamics, becomes intermittent due to current sheet formation, leading to the expectation that heating and dissipation in astrophysical and space plasmas may be highly nonuniform. Comparison with previous results from 2D kinetic simulations, as well as high frequency solar wind observational data, are discussed.

Phase transitions involving spontaneous time-reversal symmetry breaking are studied on the honeycomb lattice at finite hole doping with next-nearest-neighbor repulsion. We derive an exact expression for the mean-field equation of state in closed form, valid at temperatures much less than the Fermi energy. Contrary to standard expectations, we find that thermally induced intraband particle-hole excitations can create and stabilize a uniform metallic phase with broken time-reversal symmetry as the temperature is raised in a region where the ground state is a trivial metal.

The presence of geometric phases is known to affect the dynamics of the systems involved. Here, we consider a quantum degree of freedom, moving in a dissipative environment, whose dynamics is described by a Langevin equation with quantum noise. We show that geometric phases enter the stochastic noise terms. Specifically, we consider small ferromagnetic particles (nanomagnets) or quantum dots close to Stoner instability, and investigate the dynamics of the total magnetization in the presence of tunneling coupling to the metallic leads. We generalize the Ambegaokar-Eckern-Schön effective action and the corresponding semiclassical equations of motion from the U(1) case of the charge degree of freedom to the SU(2) case of the magnetization. The Langevin forces (torques) in these equations are strongly influenced by the geometric phase. As a first but nontrivial application, we predict low temperature quantum diffusion of the magnetization on the Bloch sphere, which is governed by the geometric phase. We propose a protocol for experimental observation of this phenomenon.

Using high-resolution, lifetime removed, x-ray absorption spectroscopy at the As $K$ edge, we evidence the strong sensitivity of the As electronic structure upon electron doping with Co or pressure change in ${\mathrm{BaFe}}_2{\mathrm{As}}_2$, at room temperature. Our results unravel the prominent role played by As-$4p$ orbitals in the electronic properties of the Fe pnictide superconductors. We propose a unique picture to describe the overall effect of both external parameter doping and pressure, resolving the apparent contradiction between angle-resolved photoemission spectroscopy, transport, and absorption results, with the As-$p$ states as a key ingredient.

The fractal globule state is a popular model for describing chromatin packing in eukaryotic nuclei. Here we provide a scaling theory and dissipative particle dynamics computer simulation for the thermal motion of monomers in the fractal globule state. Simulations starting from different entanglement-free initial states show good convergence which provides evidence supporting the existence of a unique metastable fractal globule state. We show monomer motion in this state to be subdiffusive described by $⟨X^2(t)⟩\sim t^{{\alpha }_F}$ with ${\alpha }_F$ close to 0.4. This result is in good agreement with existing experimental data on the chromatin dynamics, which makes an additional argument in support of the fractal globule model of chromatin packing.

Oscillatory systems with time-delayed pulsatile feedback appear in various applied and theoretical research areas, and received a growing interest in recent years. For such systems, we report a remarkable scenario of destabilization of a periodic regular spiking regime. At the bifurcation point numerous regimes with nonequal interspike intervals emerge. We show that the number of the emerging, so-called “jittering” regimes grows exponentially with the delay value. Although this appears as highly degenerate from a dynamical systems viewpoint, the “multijitter” bifurcation occurs robustly in a large class of systems. We observe it not only in a paradigmatic phase-reduced model, but also in a simulated Hodgkin-Huxley neuron model and in an experiment with an electronic circuit.

To a reaction-diffusion medium with an inhomogeneous anisotropic diffusion tensor $\mathbf{D}$, we add a fourth spatial dimension such that the determinant of the diffusion tensor is constant in four dimensions. We propose a generalized minimal principle for rotor filaments, stating that the scroll wave filament strives to minimize its surface area in the higher-dimensional space. As a consequence, stationary scroll wave filaments in the original 3D medium are geodesic curves with respect to the metric tensor $\mathbf{G}=\det (\mathbf{D}){\mathbf{D}}^{-1}$. The theory is confirmed by numerical simulations for positive and negative filament tension and a model with a non-stationary spiral core. We conclude that filaments in cardiac tissue with positive tension preferentially reside or anchor in regions where cardiac cells are less interconnected, such as portions of the cardiac wall with a large number of cleavage planes.

We improve the precision of the interferometric weak-value-based beam deflection measurement by introducing a power recycling mirror, creating a resonant cavity. This results in all the light exiting to the detector with a large deflection, thus eliminating the inefficiency of the rare postselection. The signal-to-noise ratio of the deflection is itself magnified by the weak value. We discuss ways to realize this proposal, using a transverse beam filter and different cavity designs.

We present a search for a neutral, long-lived particle $L$ that is produced in $e^{+}{e}^{-}$ collisions and decays at a significant distance from the $e^{+}{e}^{-}$ interaction point into various flavor combinations of two oppositely charged tracks. The analysis uses an $e^{+}{e}^{-}$ data sample with a luminosity of $489.1{\mathrm{fb}}^{-1}$ collected by the BABAR detector at the $\mathrm{\Upsilon }(4S)$, $\mathrm{\Upsilon }(3S)$, and $\mathrm{\Upsilon }(2S)$ resonances and just below the $\mathrm{\Upsilon }(4S)$. Fitting the two-track mass distribution in search of a signal peak, we do not observe a significant signal, and set 90% confidence level upper limits on the product of the $L$ production cross section, branching fraction, and reconstruction efficiency for six possible two-body $L$ decay modes as a function of the $L$ mass. The efficiency is given for each final state as a function of the mass, lifetime, and transverse momentum of the candidate, allowing application of the upper limits to any production model. In addition, upper limits are provided on the branching fraction $\mathcal{B}(B\to X_{s}L)$, where $X_s$ is a strange hadronic system.

Weakly interacting $K\to \pi X^0$ emission with $m_{X^0}\cong m_{{\pi }^0}$ is out of sight of the current $K^{+}\to {\pi }^{+}\nu \overline{\nu }$ study, but it can be sensed by the $K_L\to {\pi }^0\nu \overline{\nu }$ search. This evades the usual Grossman-Nir bound of $\mathcal{B}(K_L\to {\pi }^0\nu \overline{\nu })<1.4\times {10}^{-9}$; thus, the KOTO experiment is already starting to probe new physics. An intriguing possibility is the $Z^{\prime }$ gauge boson of a weak leptonic force that couples to $L_{\mu }-L_{\tau }$ (the difference between the muon and tauon numbers), which may explain the long-standing “muon $g-2$” anomaly, but is constrained by ${\nu }_{\mu }N\to {\nu }_{\mu }N{\mu }^{+}{\mu }^{-}$ scattering to $m_{Z^{\prime }}\lesssim 400\mathrm{MeV}$. An explicit model for $K\to \pi Z^{\prime }$ is given, which illustrates the link between rare kaon and $B\to K{\mu }^{+}{\mu }^{-}$, $K^{(*)}\nu \overline{\nu }$ decays. Complementary to these searches and future lepton experiments, the LHC might discover the scalar boson $\varphi$ responsible for light $m_{Z^{\prime }}$ generation via $\varphi \to Z^{\prime }{Z}^{\prime }\to 2({\mu }^{+}{\mu }^{-})$.

We propose a two-dimensional interferometry based on the electron wave-packet interference by using a cycle-shaped orthogonally polarized two-color laser field. With such a method, the subcycle and intercycle interferences can be disentangled into different directions in the measured photoelectron momentum spectra. The Coulomb influence can be minimized and the overlapping of interference fringes with the complicated low-energy structures can be avoided as well. The contributions of the excitation effect and the long-range Coulomb potential can be traced in the Fourier domain of the photoelectron distribution. Because of these advantages, precise information on valence electron dynamics of atoms or molecules with attosecond temporal resolution and additional spatial information with angstrom resolution can be obtained with the two-dimensional electron wave-packet interferometry.

Recent experiments on the National Ignition Facility [M. J. Edwards et al., Phys. Plasmas 20, 070501 (2013)] demonstrate that utilizing a near-vacuum hohlraum (low pressure gas-filled) is a viable option for high convergence cryogenic deuterium-tritium (DT) layered capsule implosions. This is made possible by using a dense ablator (high-density carbon), which shortens the drive duration needed to achieve high convergence: a measured 40% higher hohlraum efficiency than typical gas-filled hohlraums, which requires less laser energy going into the hohlraum, and an observed better symmetry control than anticipated by standard hydrodynamics simulations. The first series of near-vacuum hohlraum experiments culminated in a 6.8 ns, 1.2 MJ laser pulse driving a 2-shock, high adiabat ($\alpha \sim 3.5$) cryogenic DT layered high density carbon capsule. This resulted in one of the best performances so far on the NIF relative to laser energy, with a measured primary neutron yield of $1.8\times {10}^{15}$ neutrons, with 20% calculated alpha heating at convergence $\sim 27\times$.

Via measurements of commensurability features near the Landau filling factor $\nu =1/2$, we probe the shape of the Fermi contour for hole-flux composite fermions confined to a wide GaAs quantum well. The data reveal that the composite fermions are strongly influenced by the characteristics of the Landau level in which they are formed. In particular, their Fermi contour is warped when their Landau level originates from a hole band with significant warping.

Most methods of optimal control cannot obtain accurate time-optimal protocols. The quantum brachistochrone equation is an exception, and has the potential to provide accurate time-optimal protocols for a wide range of quantum control problems. So far, this potential has not been realized, however, due to the inadequacy of conventional numerical methods to solve it. Here we show that the quantum brachistochrone problem can be recast as that of finding geodesic paths in the space of unitary operators. We expect this brachistochrone-geodesic connection to have broad applications, as it opens up minimal-time control to the tools of geometry. As one such application, we use it to obtain a fast numerical method to solve the brachistochrone problem, and apply this method to two examples demonstrating its power.

Metastable $\beta$ ice holds small guest molecules in stable gas hydrates, so its solid-liquid equilibrium is of interest. However, aqueous crystal-liquid transitions are very difficult to simulate. A new molecular dynamics algorithm generates trajectories in a generalized $NPT$ ensemble and equilibrates states of coexisting phases with a selectable enthalpy. With replicas spanning the range between $\beta$ ice and liquid water, we find the statistical temperature from the enthalpy histograms and characterize the transition by the entropy, introducing a general computational procedure for first-order transitions.

Extensions of Einstein gravity with higher-order derivative terms arise in string theory and other effective theories, as well as being of interest in their own right. In this Letter we study static black-hole solutions in the example of Einstein gravity with additional quadratic curvature terms. A Lichnerowicz-type theorem simplifies the analysis by establishing that they must have vanishing Ricci scalar curvature. By numerical methods we then demonstrate the existence of further black-hole solutions over and above the Schwarzschild solution. We discuss some of their thermodynamic properties, and show that they obey the first law of thermodynamics.