We employ gravitational-wave radiometry to map the stochastic gravitational wave background expected from a variety of contributing mechanisms and test the assumption of isotropy using data from the Advanced Laser Interferometer Gravitational Wave Observatory’s (aLIGO) first observing run. We also search for persistent gravitational waves from point sources with only minimal assumptions over the 20–1726 Hz frequency band. Finding no evidence of gravitational waves from either point sources or a stochastic background, we set limits at 90% confidence. For broadband point sources, we report upper limits on the gravitational wave energy flux per unit frequency in the range $F_{\alpha ,\mathrm{\Theta }}(f)<(0.1–56)\times {10}^{-8}\mathrm{erg}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}{\mathrm{Hz}}^{-1}(f/25\mathrm{Hz}{)}^{\alpha -1}$ depending on the sky location $\mathrm{\Theta }$ and the spectral power index $\alpha$. For extended sources, we report upper limits on the fractional gravitational wave energy density required to close the Universe of $\mathrm{\Omega }(f,\mathrm{\Theta })<(0.39–7.6)\times {10}^{-8}{\mathrm{sr}}^{-1}(f/25\mathrm{Hz}{)}^{\alpha }$ depending on $\mathrm{\Theta }$ and $\alpha$. Directed searches for narrowband gravitational waves from astrophysically interesting objects (Scorpius X-1, Supernova 1987 A, and the Galactic Center) yield median frequency-dependent limits on strain amplitude of $h_0<(6.7,5.5,\mathrm{and}7.0)\times {10}^{-25}$, respectively, at the most sensitive detector frequencies between 130–175 Hz. This represents a mean improvement of a factor of 2 across the band compared to previous searches of this kind for these sky locations, considering the different quantities of strain constrained in each case.

Radiative heat transfer (RHT) between macroscopic bodies at separations that are much smaller than the thermal wavelength is ruled by evanescent electromagnetic modes and can be orders of magnitude more efficient than its far-field counterpart, which is described by the Stefan-Boltzmann law. In this Letter, we present a microscopic theory of RHT in van der Waals stacks comprising graphene and a natural hyperbolic material, i.e., hexagonal boron nitride (hBN). We demonstrate that RHT between hot carriers in graphene and hyperbolic phonon polaritons in hBN is extremely efficient at room temperature, leading to picosecond time scales for the carrier cooling dynamics.

A general formalism is introduced to allow the steady state of non-Markovian processes on networks to be reduced to equivalent Markovian processes on the same substrates. The example of an epidemic spreading process is considered in detail, where all the non-Markovian aspects are shown to be captured within a single parameter, the effective infection rate. Remarkably, this result is independent of the topology of the underlying network, as demonstrated by numerical simulations on two-dimensional lattices and various types of random networks. Furthermore, an analytic approximation for the effective infection rate is introduced, which enables the calculation of the critical point and of the critical exponents for the non-Markovian dynamics.

We demonstrate numerically the existence of a nontrivial topological Haldane phase for the one-dimensional extended ($U\text{−}V$) Hubbard model with a mean density of one particle per site, not only for bosons but also for anyons, despite a broken reflection parity symmetry. The Haldane insulator, surrounded by superfluid, Mott insulator, and density-wave phases in the $V\text{−}U$ parameter plane, is protected by combined (modified) spatial-inversion and time-reversal symmetries, which is verified within our matrix-product-state based infinite density-matrix renormalization group scheme by analyzing generalized transfer matrices. With regard to an experimental verification of the anyonic Haldane insulator state the calculated asymmetry of the dynamical density structure factor should be of particular importance.

We propose a new representation of the nonlinear sigma model that exhibits a manifest duality between flavor and kinematics. The fields couple exclusively through cubic Feynman vertices which define the structure constants of an underlying kinematic algebra. The action is invariant under a combination of internal and spacetime symmetries whose conservation equations imply flavor-kinematics duality, ensuring that all Feynman diagrams satisfy kinematic Jacobi identities. Substituting flavor for kinematics, we derive a new cubic action for the special Galileon theory. In this picture, the vanishing soft behavior of amplitudes is a by-product of the Weinberg soft theorem.

A generic expression to compute triple parton scattering cross sections in high-energy proton-proton ($pp$) collisions is presented as a function of the corresponding single parton cross sections and the transverse parton profile of the proton encoded in an effective parameter ${\sigma }_{\text{eff},\mathrm{TPS}}$. The value of ${\sigma }_{\text{eff},\mathrm{TPS}}$ is closely related to the similar effective cross section that characterizes double parton scatterings, and amounts to ${\sigma }_{\text{eff},\mathrm{TPS}}=12.5\pm 4.5\mathrm{mb}$. Estimates for triple charm ($c\overline{c}$) and bottom ($b\overline{b}$) production in $pp$ collisions at LHC and FCC energies are presented based on next-to-next-to-leading-order perturbative calculations for single $c\overline{c}$, $b\overline{b}$ cross sections. At $\sqrt{s}\approx 100\mathrm{TeV}$, about 15% of the $pp$ collisions produce three $c\overline{c}$ pairs from three different parton-parton scatterings.

We propose an optical scheme, employing optical parametric down-converters interlaced with nonlinear sign gates (NSGs), that completely converts an $n$-photon Fock-state pump to $n$ signal-idler photon pairs when the down-converters’ crystal lengths are chosen appropriately. The proof of this assertion relies on amplitude amplification, analogous to that employed in Grover search, applied to the full quantum dynamics of single-mode parametric down-conversion. When we require that all Grover iterations use the same crystal, and account for potential experimental limitations on crystal-length precision, our optimized conversion efficiencies reach unity for $1\le n\le 5$, after which they decrease monotonically for $n$ values up to 50, which is the upper limit of our numerical dynamics evaluations. Nevertheless, our conversion efficiencies remain higher than those for a conventional (no NSGs) down-converter.

We show that dephasing of individual atoms destroys the superradiance transition of the Dicke model, but that adding individual decay toward the spin down state can restore this transition. To demonstrate this, we present a method to give an exact solution for the $N$ atom problem with individual dephasing which scales polynomially with $N$. By comparing finite size scaling of our exact solution to a cumulant expansion, we confirm the destruction and restoration of the superradiance transition hold in the thermodynamic limit.

We show that steady nonuniform motion of a medium through an optical resonator can yield light amplification at the resonator frequency. High gain can be achieved if at the generated frequency the medium refractive index is close to zero or the medium has a very strong frequency dispersion. We also discuss an analogy between light amplification by a moving medium and the generation of sound waves when gas flows along a tube with acoustically closed-open boundaries.

The flagellar beat is extracted from human sperm digital imaging microscopy and used to determine the flow around the cell and its trajectory, via boundary element simulation. Comparison of the predicted cell trajectory with observation demonstrates that simulation can predict fine-scale sperm dynamics at the qualitative level. The flow field is also observed to reduce to a time-dependent summation of regularized Stokes flow singularities, approximated at leading order by a blinking force triplet. Such regularized singularity decompositions may be used to upscale cell level detail into population models of human sperm motility.

For viscously unstable, miscible Hele-Shaw displacements, we investigate the origin of the streamwise vorticity shown to be responsible for the inner splitting mechanism by Oliveira and Meiburg [J. Fluid Mech. 687 431 (2011)]. Towards this end, we compare 3D Navier-Stokes simulation results for neutrally buoyant, viscously unstable displacements and gravitationally unstable, constant viscosity ones. Only the former exhibit the generation of streamwise vorticity. The simulation results show that it is caused by the lateral displacement of the more viscous fluid by the less viscous one, with the variable viscosity terms playing a dominant role.

The nature of the magnetic structure arising from ion specular reflection in shock compression studies is examined by means of 1D particle-in-cell simulations. Propagation speed, field profiles, and supporting currents for this magnetic structure are shown to be consistent with a magnetosonic soliton. Coincidentally, this structure and its evolution are typical of foot structures observed in perpendicular shock reformation. To reconcile these two observations, we propose, for the first time, that shock reformation can be explained as the result of the formation, growth, and subsequent transition to a supercritical shock of a magnetosonic soliton. This argument is further supported by the remarkable agreement found between the period of the soliton evolution cycle and classical reformation results. This new result suggests that the unique properties of solitons can be used to shed new light on the long-standing issue of shock nonstationarity and its role on particle acceleration.

We show that graphene-dielectric multilayers give rise to an unusual tunability of the Casimir-Lifshitz forces and allow to easily realize completely different regimes within the same structure. Concerning thermal effects, graphene-dielectric multilayers take advantage of the anomalous features predicted for isolated suspended graphene sheets, even though they are considerably affected by the presence of the dielectric substrate. They can also achieve the anomalous nonmonotonic thermal metallic behavior by increasing the graphene sheets density and their Fermi level. In addition to a strong thermal modulation occurring at short separations, in a region where the force is orders of magnitude larger than the one occurring at large distances, the force can be also adjusted by varying the number of graphene layers as well as their Fermi levels, allowing for relevant force amplifications which can be tuned, very rapidly and in situ, by simply applying an electric potential. Our predictions can be relevant for both Casimir experiments and micro- or nanoelectromechanical systems and in new devices for technological applications.

We derive an exact operatorial reformulation of the rotational invariant slave boson method, and we apply it to describe the orbital differentiation in strongly correlated electron systems starting from first principles. The approach enables us to treat strong electron correlations, spin-orbit coupling, and crystal field splittings on the same footing by exploiting the gauge invariance of the mean-field equations. We apply our theory to the archetypical nuclear fuel ${\mathrm{UO}}_2$ and show that the ground state of this system displays a pronounced orbital differentiation within the $5f$ manifold, with Mott-localized ${\mathrm{\Gamma }}_8$ and extended ${\mathrm{\Gamma }}_7$ electrons.

We report on the strong coupling of surface plasmon polaritons and molecular vibrations in an organic-inorganic plasmonic hybrid structure consisting of a ketone-based polymer deposited on top of a silver layer. Attenuated-total-reflection spectra of the hybrid reveal an anticrossing in the dispersion relation in the vicinity of the carbonyl stretch vibration of the polymer with an energy splitting of the upper and lower polariton branch up to 15 meV. The splitting is found to depend on the molecular layer thickness and saturates for micrometer-thick films. This new hybrid state holds a strong potential for application in chemistry and optoelectronics.

No experiment could directly test the particle-antiparticle duality of Majorana fermions, so far. However, this property represents a necessary ingredient towards the realization of topological quantum computing schemes. Here, we show how to complete this task by using microwave techniques. The direct coupling between a pair of overlapping Majorana bound states and the electric field from a microwave cavity is extremely difficult to detect due to the self-adjoint character of Majorana fermions which forbids direct energy exchanges with the cavity. We show theoretically how this problem can be circumvented by using photoassisted tunneling to fermionic reservoirs. The absence of a direct microwave transition inside the Majorana pair in spite of the light-Majorana coupling would represent a smoking gun for the Majorana self-adjoint character.