The classical Landau-Lifshitz equation with a damping term has been derived from the time evolution of a quantum mechanical wave function under the assumption of a non-Hermitian Hamilton operator. Further, the trajectory of a classical spin ($\mathbf{S}$) has been compared with the expectation value of the spin operator ($\widehat{\mathbf{S}}$). A good agreement between classical and quantum mechanical trajectories can be found for Hamiltonians linear in $\widehat{\mathbf{S}}$ or $S$, respectively. Quadratic or higher order terms in the Hamiltonian result in a disagreement.

It is shown that a junction of three critical quantum Ising chains (Delta junction) can be described as a two-channel Kondo model with a spin $S=1/2$ localized at the junction, which is composed of the respective Ising, zero energy boundary Majorana modes.

We examine the zero-temperature phase diagram of the two-dimensional Levin-Wen string-net model with Fibonacci anyons in the presence of competing interactions. Combining high-order series expansions around three exactly solvable points and exact diagonalizations, we find that the non-Abelian doubled Fibonacci topological phase is separated from two nontopological phases by different second-order quantum critical points, the positions of which are computed accurately. These trivial phases are separated by a first-order transition occurring at a fourth exactly solvable point where the ground-state manifold is infinitely many degenerate. The evaluation of critical exponents suggests unusual universality classes.

We demonstrate tuning of magnetocrystalline anisotropy in high-quality ${\mathrm{Sr}}_2{\mathrm{FeMoO}}_6$ epitaxial films over a range of several thousand Gauss using strain induced by epitaxial growth on substrates of varying lattice constants. Spectroscopic measurements reveal a striking, linear dependence of the out-of-plane anisotropy on the strain-induced tetragonal distortion of the ${\mathrm{Sr}}_2{\mathrm{FeMoO}}_6$ lattice. This anisotropy can be tuned from $+2000$ to $-3300\mathrm{Oe}$, a range sufficient to rotate the easy axis from in plane to out of plane. Combined with its half-metallicity and high Curie temperature, this result implies a broad range of scientific and technological applications for this novel spintronic material.

It is demonstrated how the exciton and the biexciton state of a quantum dot can be prepared with high fidelity on a picosecond time scale by driving the dot with a strong laser pulse that is tuned above the exciton resonance for exciton preparation and in resonance with the exciton transition for biexciton preparation. The proposed protocols make use of the phonon-induced relaxation towards photon dressed states in optically driven quantum dots and combine the simplicity of traditional Rabi oscillation schemes with the robustness of adiabatic rapid passage schemes. Our protocols allow for an on-demand, fast, and almost perfect state preparation even at strong carrier-phonon interaction where other schemes fail. In fact, the performance of the presented protocols is shown to be better the stronger the carrier-phonon interaction is.

Recently, an enrichment of identical matching sequences has been found in many eukaryotic genomes. Their length distribution exhibits a power law tail raising the question of what evolutionary mechanism or functional constraints would be able to shape this distribution. Here we introduce a simple and evolutionarily neutral model, which involves only point mutations and segmental duplications, and produces the same statistical features as observed for genomic data. Further, we extend a mathematical model for random stick breaking to analytically show that the exponent of the power law tail is $-3$ and universal as it does not depend on the microscopic details of the model.

Recent experiments on the green alga Chlamydomonas that swims using synchronized beating of a pair of flagella have revealed that it exhibits a run-and-tumble behavior similar to that of bacteria such as E. coli. Using a simple purely hydrodynamic model that incorporates a stroke cycle and an intrinsic Gaussian white noise, we show that a stochastic run-and-tumble behavior could emerge due to the nonlinearity of the combined synchronization-rotation-translation dynamics. Our study suggests that nonlinear mechanics could be a significant contributing factor to how the trajectories of the microorganism are selected.

We analyze experimentally chemical wave propagation in the disordered flow field of a porous medium. The reaction fronts travel at a constant velocity that drastically depends on the mean flow direction and rate. The fronts may propagate either downstream and upstream but, surprisingly, they remain static over a range of flow rate values. Resulting from the competition between the chemical reaction and the disordered flow field, these frozen fronts display a particular sawtooth shape. The frozen regime is likely to be associated with front pinning in low velocity zones, the number of which varies with the ratio of the mean flow and the chemical front velocities.

We present two new primary mechanisms for the synthesis of the rare nucleus ${}^9\mathrm{Be}$, both triggered by $\nu$-induced production of ${}^3\mathrm{H}$ followed by ${}^4\mathrm{He}({}^3\mathrm{H},\gamma ){}^7\mathrm{Li}$ in the He shells of core-collapse supernovae. For progenitors of $\sim 8M_{\odot }$, ${}^7\mathrm{Li}({}^3\mathrm{H},n_0){}^9\mathrm{Be}$ occurs during the rapid expansion of the shocked He shell. Alternatively, for ultra-metal-poor progenitors of $\sim 11–15M_{\odot }$, ${}^7\mathrm{Li}(n,\gamma ){}^8\mathrm{Li}(n,\gamma ){}^9\mathrm{Li}(e^{-}{\overline{\nu }}_e){}^9\mathrm{Be}$ occurs with neutrons produced by ${}^4\mathrm{He}({\overline{\nu }}_e,e^{+}n){}^3\mathrm{H}$, assuming a hard effective ${\overline{\nu }}_e$ spectrum from oscillations (which also leads to heavy element production through rapid neutron capture) and a weak explosion (so the ${}^9\mathrm{Be}$ survives shock passage). We discuss the associated production of ${}^7\mathrm{Li}$ and ${}^{11}\mathrm{B}$, noting patterns in LiBeB production that might distinguish the new mechanisms from others.

We demonstrate one- and two-dimensional transverse laser cooling and magneto-optical trapping of the polar molecule yttrium (II) oxide (YO). In a 1D magneto-optical trap (MOT), we characterize the magneto-optical trapping force and decrease the transverse temperature by an order of magnitude, from 25 to 2 mK, limited by interaction time. In a 2D MOT, we enhance the intensity of the YO beam and reduce the transverse temperature in both transverse directions. The approach demonstrated here can be applied to many molecular species and can also be extended to 3D.

Thin jets of viscous fluid like honey falling from capillary nozzles can attain lengths exceeding 10 m before breaking up into droplets via the Rayleigh-Plateau (surface tension) instability. Using a combination of laboratory experiments and WKB analysis of the growth of shape perturbations on a jet being stretched by gravity, we determine how the jet’s intact length $l_b$ depends on the flow rate $Q$, the viscosity $\eta$, and the surface tension coefficient $\gamma$. In the asymptotic limit of a high-viscosity jet, $l_b\sim (g{Q}^2{\eta }^4/{\gamma }^4{)}^{1/3}$, where $g$ is the gravitational acceleration. The agreement between theory and experiment is good, except for very long jets.

Spherically symmetric direct-drive-ignition designs driven by laser beams with a focal-spot size nearly equal to the target diameter suffer from energy losses due to crossed-beam energy transfer (CBET). Significant reduction of CBET and improvements in implosion hydrodynamic efficiency can be achieved by reducing the beam diameter. Narrow beams increase low-mode perturbations of the targets because of decreased illumination uniformity that degrades implosion performance. Initiating an implosion with nominal beams (equal in size to the target diameter) and reducing the beam diameter by $\sim 30\%–40\%$ after developing a sufficiently thick target corona, which smooths the perturbations, mitigate CBET while maintaining low-mode target uniformity in ignition designs with a fusion gain $\gg 1$.

Beam emission spectroscopy (BES) measurements of ion-scale density fluctuations in the MAST tokamak are used to show that the turbulence correlation time, the drift time associated with ion temperature or density gradients, the particle (ion) streaming time along the magnetic field, and the magnetic drift time are consistently comparable, suggesting a “critically balanced” turbulence determined by the local equilibrium. The resulting scalings of the poloidal and radial correlation lengths are derived and tested. The nonlinear time inferred from the density fluctuations is longer than the other times; its ratio to the correlation time scales as ${\nu }_{*i}^{-0.8\pm 0.1}$, where ${\nu }_{*i}=\mathrm{ion}\mathrm{collision}\mathrm{rate}/\mathrm{streaming}\mathrm{rate}$. This is consistent with turbulent decorrelation being controlled by a zonal component, invisible to the BES, with an amplitude exceeding those of the drift waves by $\sim {\nu }_{*i}^{-0.8}$.

We provide a comprehensive picture of the jamming phase diagram by connecting the athermal, granular ensemble of jammed states and the equilibrium fluid through the inherent structure paradigm for a system of hard disks confined to a narrow channel. The $J$ line is shown to be divided into packings that are either accessible or inaccessible from the equilibrium fluid. The $J$ point itself is found to occur at the transition between these two sets of packings and is located at the maximum of the inherent structure distribution. We also present a general thermodynamic argument that suggests the density of the states at the maximum of the configurational entropy represents a lower bound on the $J$-point density in hard sphere systems. Finally, we show that the granular system, modeled using the Edwards ensemble, and the fluid sample the same set of thermodynamically accessible states over the full range of thermodynamic state points, but only occupy the same set of inherent structures, under the same thermodynamic conditions, at two points, corresponding to zero and infinite pressures, where they sample the $J$-point states and the most dense packing, respectively.

We calculate the photoemission spectra of suspended and epitaxial doped graphene using an ab initio cumulant expansion of the Green’s function based on the $GW$ self-energy. Our results are compared to experiment and to standard $GW$ calculations. For doped graphene on a silicon carbide substrate, we find, in contrast to earlier calculations, that the spectral function from $GW$ only does not reproduce experimental satellite properties. However, ab initio $GW$ plus cumulant theory combined with an accurate description of the substrate screening results in good agreement with experiment, but gives no plasmaron (i.e., no extra well-defined excitation satisfying Dyson’s equation).

We utilized microwave spectroscopy to study the magnetization oscillations locally induced in a Permalloy film by a pure spin current, which is generated due to the spin Hall effect in an adjacent Pt layer. The oscillation frequency is lower than the ferromagnetic resonance of Permalloy, indicating that the oscillation forms a self-localized nonpropagating spin-wave soliton. At cryogenic temperatures, the spectral characteristics are remarkably similar to the traditional spin-torque nano-oscillators driven by spin-polarized currents. However, the linewidth of the oscillation increases exponentially with temperature and an additional peak appears in the spectrum below the ferromagnetic resonance, suggesting that the spectral characteristics are determined by interplay between two localized dynamical states.

We have performed a search for muon neutrinos from dark matter annihilation in the center of the Sun with the 79-string configuration of the IceCube neutrino telescope. For the first time, the DeepCore subarray is included in the analysis, lowering the energy threshold and extending the search to the austral summer. The 317 days of data collected between June 2010 and May 2011 are consistent with the expected background from atmospheric muons and neutrinos. Upper limits are set on the dark matter annihilation rate, with conversions to limits on spin-dependent and spin-independent scattering cross sections of weakly interacting massive particles (WIMPs) on protons, for WIMP masses in the range $20–5000\mathrm{GeV}/c^2$. These are the most stringent spin-dependent WIMP-proton cross section limits to date above $35\mathrm{GeV}/c^2$ for most WIMP models.

We exhaust all exact self-consistent solutions of complex-valued fermionic condensates in the ($1+1$)-dimensional Bogoliubov–de Gennes and chiral Gross-Neveu systems under uniform boundary conditions. We obtain $n$ complex (twisted) kinks, or gray solitons, with $2n$ parameters corresponding to their positions and phase shifts. Each soliton can be placed at an arbitrary position while the self-consistency requires its phase shift to be quantized by $\pi /N$ for $N$ flavors.

We project onto the light front the pion’s Poincaré-covariant Bethe-Salpeter wave function obtained using two different approximations to the kernels of quantum chromodynamics’ Dyson-Schwinger equations. At an hadronic scale, both computed results are concave and significantly broader than the asymptotic distribution amplitude, ${\phi }_{\pi }^{\mathrm{asy}}(x)=6x(1-x)$; e.g., the integral of ${\phi }_{\pi }(x)/{\phi }_{\pi }^{\mathrm{asy}}(x)$ is 1.8 using the simplest kernel and 1.5 with the more sophisticated kernel. Independent of the kernels, the emergent phenomenon of dynamical chiral-symmetry breaking is responsible for hardening the amplitude.

We study experimentally and theoretically structural defects which are formed during the transition from a laser cooled cloud to a Coulomb crystal, consisting of tens of ions in a linear radio frequency trap. We demonstrate the creation of predicted topological defects (“kinks”) in purely two-dimensional crystals and also find kinks which show novel dynamical features in a regime of parameters not considered before. The kinks are always observed at the center of the trap, showing a large nonlinear localized excitation, and the probability of their occurrence saturates at $\sim 0.5$. Simulations reveal a strong anharmonicity of the kink’s internal mode of vibration, due to the kink’s extension into three dimensions. As a consequence, the periodic Peierls-Nabarro potential experienced by a discrete kink becomes a globally confining potential, capable of trapping one cooled defect at the center of the crystal.