We compare the decay of turbulence in superfluid ${}^4\mathrm{He}$ produced by a moving grid to the decay of turbulence created by either impulsive spin-down to rest or by intense ion injection. In all cases, the vortex line density $\mathcal{L}$ decays at late time $t$ as $\mathcal{L}\propto t^{-3/2}$. At temperatures above 0.8 K, all methods result in the same rate of decay. Below 0.8 K, the spin-down turbulence maintains initial rotation and decays slower than grid turbulence and ion-jet turbulence. This may be due to a decoupling of the large-scale superfluid flow from the normal component at low temperatures, which changes its effective boundary condition from no-slip to slip.

The collective strength of a system of fibers, each having a failure threshold drawn randomly from a distribution, indicates the maximum load carrying capacity of different disordered systems ranging from disordered solids, power-grid networks, to traffic in a parallel system of roads. In many of the cases where the redistribution of load following a local failure can be controlled, it is a natural requirement to find the most efficient redistribution scheme, i.e., following which system can carry the maximum load. We address the question here and find that the answer depends on the mode of loading. We analytically find the maximum strength and corresponding redistribution schemes for sudden and quasistatic loading. The associated phase transition from partial to total failure by increasing the load has been studied. The universality class is found to be dependent on the redistribution mechanism.

We consider a theoretical problem of electron-electron scattering time in a quasi-one-dimensional (Q1D) conductor in a magnetic field, perpendicular to its conducting axis. We show that inverse electron-electron scattering time becomes of the order of characteristic electron energy, $1/\tau \sim \epsilon \sim T$, in a high magnetic field, directed far from the main crystallographic axes, which indicates breakdown of the Fermi-liquid theory. In a magnetic field, directed close to one of the main crystallographic axis, inverse electron-electron scattering time becomes much smaller than characteristic electron energy and, thus, applicability of Fermi-liquid theory restores. We suggest that there exist crossovers (or phase transitions) between Fermi-liquid and some non-Fermi-liquid states in a strong enough tilted magnetic field. Application of our results to the Q1D conductor $(\text{Per}{)}_2\mathrm{Au}(\text{mnt}{)}_2$ shows that it has to be possible to observe the above-mentioned phenomenon in feasibly high magnetic fields of the order of $H\ge H^{*}\simeq 25\mathrm{T}$.

We introduce two operational entanglement measures that are applicable for arbitrary multipartite (pure or mixed) states. One of them characterizes the potentiality of a state to generate other states via local operations assisted by classical communication and the other characterizes the simplicity of generating the state at hand. We show how these measures can be generalized to two classes of entanglement measures. Moreover, we compute the new measures for pure few-partite systems and use them to characterize the entanglement contained in a three-qubit state. We identify the Greenberger-Horne-Zeilinger and $W$ state as the most powerful pure three-qubit states regarding state manipulation.

Recently, Almheiri, Dong, and Harlow have argued that the localization of bulk information in a boundary dual should be understood in terms of quantum error correction. We show that this structure appears naturally when the gauge invariance of the boundary theory is incorporated. This provides a new understanding of the nonuniqueness of the bulk fields (precursors). It suggests a close connection between gauge invariance and the emergence of spacetime.

The rare decay $B\to \pi {\ell }^{+}{\ell }^{-}$ arises from $b\to d$ flavor-changing neutral currents and could be sensitive to physics beyond the standard model. Here, we present the first ab initio QCD calculation of the $B\to \pi$ tensor form factor $f_T$. Together with the vector and scalar form factors $f_{+}$ and $f_0$ from our companion work [J. A. Bailey et al., Phys. Rev. D 92, 014024 (2015)], these parametrize the hadronic contribution to $B\to \pi$ semileptonic decays in any extension of the standard model. We obtain the total branching ratio $\mathrm{BR}(B^{+}\to {\pi }^{+}{\mu }^{+}{\mu }^{-})=20.4(2.1)\times {10}^{-9}$ in the standard model, which is the most precise theoretical determination to date, and agrees with the recent measurement from the LHCb experiment [R. Aaij et al., J. High Energy Phys. 12 (2012) 125].

We present the final combination of CDF and D0 measurements of cross sections for single-top-quark production in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to $9.7{\mathrm{fb}}^{-1}$ per experiment. The $t$-channel cross section is measured to be ${\sigma }_t=2.25_{-0.31}^{+0.29}\mathrm{pb}$. We also present the combinations of the two-dimensional measurements of the $s$- vs $t$-channel cross section. In addition, we give the combination of the $s+t$ channel cross section measurement resulting in ${\sigma }_{s+t}=3.30_{-0.40}^{+0.52}\mathrm{pb}$, without assuming the standard model value for the ratio ${\sigma }_s/{\sigma }_t$. The resulting value of the magnitude of the top-to-bottom quark coupling is $|V_{tb}|=1.02_{-0.05}^{+0.06}$, corresponding to $|V_{tb}|>0.92$ at the 95% C.L.

We theoretically demonstrate the possibility to generate both trains and isolated attosecond pulses with high ellipticity in a practical experimental setup. The scheme uses circularly polarized, counterrotating two-color driving pulses carried at the fundamental and its second harmonic. Using a model Ne atom, we numerically show that highly elliptic attosecond pulses are generated already at the single-atom level. Isolated pulses are produced by using few-cycle drivers with controlled time delay between them.

In this Letter, we demonstrate the effect of nonresonant charged-particle acceleration by an electrostatic wave propagating across the background magnetic field. We show that in the absence of resonance (i.e., when particle velocities are much smaller than the wave phase velocity) particles can be accelerated by electrostatic waves provided that the adiabaticity of particle motion is destroyed by magnetic field fluctuations. Thus, in a system with stochastic particle dynamics the electrostatic wave should be damped even in the absence of Landau resonance. The proposed mechanism is responsible for the acceleration of particles that cannot be accelerated via resonant wave-particle interactions. Simplicity of this straightforward acceleration scenario indicates a wide range of possible applications.

An important limit for energy gain in laser-plasma wakefield accelerators is the dephasing length, after which the electron beam reaches the decelerating region of the wakefield and starts to decelerate. Here, we propose to manipulate the phase of the electron beam in the wakefield, in order to bring the beam back into the accelerating region, hence increasing the final beam energy. This rephasing is operated by placing an upward density step in the beam path. In a first experiment, we demonstrate the principle of this technique using a large energy spread electron beam. Then, we show that it can be used to increase the energy of monoenergetic electron beams by more than 50%.

According to the mean-field theory a condensed Bose-Bose mixture collapses when the interspecies attraction becomes stronger than the geometrical average of the intraspecies repulsions, $g_{12}^2>g_{11}{g}_{22}$. We show that instead of collapsing such a mixture gets into a dilute liquidlike droplet state stabilized by quantum fluctuations thus providing a direct manifestation of beyond mean-field effects. We study various properties of the droplet and find, in particular, that in a wide range of parameters its excitation spectrum lies entirely above the particle emission threshold. The droplet thus automatically evaporates itself to zero temperature, the property potentially interesting by itself and from the viewpoint of sympathetic cooling of other systems.

We study the prototype $5d$ pyrochlore iridate ${\mathrm{Y}}_2{\mathrm{Ir}}_2{\mathrm{O}}_7$ from first principles using the local density approximation and dynamical mean-field theory ($\mathrm{LDA}+\mathrm{DMFT}$). We map out the phase diagram in the space of temperature, on-site Coulomb repulsion $U$, and filling. Consistent with experiments, we find that an all-in–all-out ordered insulating phase is stable for realistic values of $U$. The trigonal crystal field enhances the hybridization between the $j_{\mathrm{eff}}=1/2$ and $j_{\mathrm{eff}}=3/2$ states, and strong interband correlations are induced by the Coulomb interaction, which indicates that a three-band description is important. We demonstrate a substantial band narrowing in the paramagnetic metallic phase and non-Fermi-liquid behavior in the electron- or hole-doped system originating from long-lived quasi-spin-moments induced by nearly flat bands.

In this Letter we present, in a number conserving framework, a model of interacting fermions in a two-wire geometry supporting nonlocal zero-energy Majorana-like edge excitations. The model has an exactly solvable line, on varying the density of fermions, described by a topologically nontrivial ground state wave function. Away from the exactly solvable line we study the system by means of the numerical density matrix renormalization group. We characterize its topological properties through the explicit calculation of a degenerate entanglement spectrum and of the braiding operators which are exponentially localized at the edges. Furthermore, we establish the presence of a gap in its single particle spectrum while the Hamiltonian is gapless, and compute the correlations between the edge modes as well as the superfluid correlations. The topological phase covers a sizable portion of the phase diagram, the solvable line being one of its boundaries.

In integrable many-particle systems, it is widely believed that the stationary state reached at late times after a quantum quench can be described by a generalized Gibbs ensemble (GGE) constructed from their extensive number of conserved charges. A crucial issue is then to identify a complete set of these charges, enabling the GGE to provide exact steady-state predictions. Here we solve this long-standing problem for the case of the spin-$1/2$ Heisenberg chain by explicitly constructing a GGE which uniquely fixes the macrostate describing the stationary behavior after a general quantum quench. A crucial ingredient in our method, which readily generalizes to other integrable models, are recently discovered quasilocal charges. As a test, we reproduce the exact postquench steady state of the Néel quench problem obtained previously by means of the Quench Action method.

We introduce a simple model of $\mathrm{SO}(N)$ spins with two-site interactions which is amenable to quantum Monte Carlo studies without a sign problem on nonbipartite lattices. We present numerical results for this model on the two-dimensional triangular lattice where we find evidence for a spin nematic at small $N$, a valence-bond solid at large $N$, and a quantum spin liquid at intermediate $N$. By the introduction of a sign-free four-site interaction, we uncover a rich phase diagram with evidence for both first-order and exotic continuous phase transitions.

We show that the formation of a magnon condensate in thin ferromagnetic films can be explained within the framework of a classical stochastic non-Markovian Landau-Lifshitz-Gilbert equation where the properties of the random magnetic field and the dissipation are determined by the underlying phonon dynamics. We have numerically solved this equation for a tangentially magnetized yttrium-iron garnet film in the presence of a parallel parametric pumping field. We obtain a complete description of all stages of the nonequilibrium time evolution of the magnon gas which is in excellent agreement with experiments. Our calculation proves that the experimentally observed condensation of magnons in yttrium-iron garnet at room temperature is a purely classical phenomenon which should be called Rayleigh-Jeans rather than Bose-Einstein condensation.

We report on dynamical interference between short-lived Rabi oscillations and long-lived coherent phonons in CuCl semiconductor microcavities resulting from the coupling between the two oscillations. The Fourier-transformed spectra of the time-domain signals obtained from semiconductor microcavities by using a pump-probe technique show that the intensity of the coherent longitudinal optical phonon of CuCl is enhanced by increasing that of the Rabi oscillation, which indicates that the coherent phonon is driven by the Rabi oscillation through the Fröhlich interaction. Moreover, as the Rabi oscillation frequency decreases upon crossing the phonon frequency, the spectral profile of the coherent phonon changes from a peak to a dip with an asymmetric structure. The continuous wavelet transformation reveals that these peak and dip structures originate from constructive and destructive interference between Rabi oscillations and coherent phonons, respectively. We demonstrate that the asymmetric spectral structures in relation to the frequency detuning are well reproduced by using a classical coupled oscillator model on the basis of dynamical Fano-like interference.

We study the constant stress and pressure rheology of dense hard-sphere colloidal suspensions using Brownian dynamics simulation. Expressing the flow behavior in terms of the friction coefficient—the ratio of shear to normal stress—reveals a shear arrest point from the collapse of the rheological data in the non-Brownian limit. The flow curves agree quantitatively (when scaled) with the experiments of Boyer et al. [Phys. Rev. Lett. 107, 188301 (2011)]. Near suspension arrest, both the shear and the incremental normal viscosities display a universal power law divergence. This work shows the important role of jamming on the arrest of colloidal suspensions and illustrates the care needed when conducting and analyzing experiments and simulations near the flow-arrest transition.