Dense plasma focus $Z$-pinch devices are sources of copious high energy electrons and ions, x rays, and neutrons. The mechanisms through which these physically simple devices generate such high-energy beams in a relatively short distance are not fully understood. We now have, for the first time, demonstrated a capability to model these plasmas fully kinetically, allowing us to simulate the pinch process at the particle scale. We present here the results of the initial kinetic simulations, which reproduce experimental neutron yields ($\sim {10}^7$) and high-energy (MeV) beams for the first time. We compare our fluid, hybrid (kinetic ions and fluid electrons), and fully kinetic simulations. Fluid simulations predict no neutrons and do not allow for nonthermal ions, while hybrid simulations underpredict neutron yield by $\sim 100x$ and exhibit an ion tail that does not exceed 200 keV. Only fully kinetic simulations predict MeV-energy ions and experimental neutron yields. A frequency analysis in a fully kinetic simulation shows plasma fluctuations near the lower hybrid frequency, possibly implicating lower hybrid drift instability as a contributor to anomalous resistivity in the plasma.

Measurements of the energy spectrum and of the vortex-density fluctuation spectrum in superfluid turbulence seem to contradict each other. Using a numerical model, we show that at each instance of time the total vortex line density can be decomposed into two parts: one formed by metastable bundles of coherent vortices, and one in which the vortices are randomly oriented. We show that the former is responsible for the observed Kolmogorov energy spectrum, and the latter for the spectrum of the vortex line density fluctuations.

Ultracold fermionic alkaline earth atoms confined in optical lattices realize Hubbard models with internal $\mathrm{SU}(N)$ symmetries, where $N$ can be as large as ten. Such systems are expected to harbor exotic magnetic physics at temperatures below the superexchange energy scale. Employing quantum Monte Carlo simulations to access the low-temperature regime of one-dimensional chains, we show that after adiabatically loading a weakly interacting gas into the strongly interacting regime of an optical lattice, the final temperature decreases with increasing $N$. Furthermore, we estimate the temperature scale required to probe correlations associated with low-temperature $\mathrm{SU}(N)$ magnetism. Our findings are encouraging for the exploration of exotic large-$N$ magnetic states in ongoing experiments.

Motivated by the possibility to load multicolor fermionic atoms in optical lattices, we study the entropy dependence of the properties of the one-dimensional antiferromagnetic $\mathrm{SU}(N)$ Heisenberg model, the effective model of the $\mathrm{SU}(N)$ Hubbard model with one particle per site (filling $1/N$) in the large $U/t$ limit. Using continuous-time world-line Monte Carlo simulations for $N=2–5$, we show that characteristic short-range correlations develop at low temperature as a precursor of the ground state algebraic correlations. We also calculate the entropy as a function of temperature, and we show that the first sign of short-range order appears at an entropy per particle that increases with $N$ and already reaches $0.8k_B$ at $N=4$, in the range of experimentally accessible values.

We analytically solve the core percolation problem for complex networks with arbitrary degree distributions. We find that purely scale-free networks have no core for any degree exponents. We show that for undirected networks if core percolation occurs then it is continuous while for directed networks it is discontinuous (and hybrid) if the in- and out-degree distributions differ. We also find that core percolations on undirected and directed networks have completely different critical exponents associated with their critical singularities.

It is highly desirable to integrate graphene into existing semiconductor technology, where the combined system is thermodynamically stable yet maintain a Dirac cone at the Fermi level. First-principles calculations reveal that a certain transition metal (TM) intercalated $\mathrm{\text{graphene}}/\mathrm{SiC}(0001)$, such as the strongly bound graphene on SiC with Mn intercalation, could be such a system. Different from freestanding graphene, the hybridization between graphene and $\mathrm{Mn}/\mathrm{SiC}$ leads to the formation of a dispersive Dirac cone of primarily TM $d$ characters. The corresponding Dirac spectrum is still isotropic, and the transport behavior is nearly identical to that of freestanding graphene for a bias as large as 0.6 V, except that the Fermi velocity is half that of graphene. A simple model Hamiltonian is developed to qualitatively account for the physics of the transfer of the Dirac cone from a dispersive system (e.g., graphene) to an originally nondispersive system (e.g., TM).

We present a combined experimental and theoretical study of the interplay between the atomic structure and the magnon excitations in low dimensional ferromagnets. Two monolayer thick Fe films on W(110) with and without a Au buffer layer are investigated. Our experiments show that adding the Au layer leads to a significant softening of the magnons. First-principles calculations confirm the experimental results revealing a strong dependency of exchange interactions on the atomic structure. It is observed that the intralayer exchange interactions increase with increasing distance between Fe layers. This unusual relationship is attributed to the complexity of the electronic structure and the contribution of different orbitals to the hybridization and exchange interaction. Our results suggest a way of tailoring magnetic excitations in low-dimensional magnetic structures.

Large scale traffic networks are an indispensable part of contemporary human mobility and international trade. Networks of airport travel and cargo ship movements are invaluable for the understanding of human mobility patterns [R. Guimera et al., Proc. Natl. Acad. Sci. U.S.A. 102, 7794 (2005))], epidemic spreading [V. Colizza et al., Proc. Natl. Acad. Sci. U.S.A. 103, 2015 (2006)], global trade [International Maritime Organization, http://www.imo.org/], and spread of invasive species [G. M. Ruiz et al., Nature (London) 408, 49 (2000)]. Different studies [M. Barthelemy, Phys. Rept. 499, 1 (2011)] point to the universal character of some of the exponents measured in such networks. Here we show that exponents which relate (i) the strength of nodes to their degree and (ii) weights of links to degrees of nodes that they connect have a geometric origin. We present a simple robust model which exhibits the observed power laws and relates exponents to the dimensionality of 2D space in which traffic networks are embedded. We show that the relation between weight strength and degree is $s(k)\sim k^{3/2}$, the relation between distance strength and degree is $s^d(k)\sim k^{3/2}$, and the relation between weight of link and degrees of linked nodes is $w_{ij}\sim (k_i{k}_j{)}^{1/2}$ on the plane 2D surface. We further analyze the influence of spherical geometry, relevant for the whole planet, on exact values of these exponents. Our model predicts that these exponents should be found in future studies of port networks and it imposes constraints on more refined models of port networks.

We propose a method for quantization of Lagrangians for which the Hamiltonian, as a function of momentum, is a branched function, possibly with cusps. Appropriate boundary conditions, which we identify, ensure unitary time evolution. In special cases a dual (canonical) transformation maps the problem into a problem of quantum mechanics on singular spaces, which we also develop. Several possible applications are indicated.

We propose the implementation of the Holstein model by means of digital methods in a linear chain of trapped ions. We show how the simulation fidelity scales with the generation of phononic excitations. We propose a decomposition and a stepwise trapped-ion implementation of the Holstein Hamiltonian. Via numerical simulations, we study how the protocol is affected by realistic gates. Finally, we show how measurements of the size of the simulated polaron can be performed.

In this note we discuss the classification of duality orbits of $N=8$ gauged supergravity models. Using tensor classifiers, we show that there is a one-parameter family of inequivalent SO(8) gauged supergravity theories. We briefly discuss the couplings of such models and show that, although the maximally symmetric vacuum has the same quadratic spectrum, the supersymmetry transformations, the couplings, and the scalar potential are parameter dependent. We also comment on the possible M theory uplift and on the meaning of the parameter for the dual gauge theories.

We derive first next-to-next-to-leading logarithmic resummations for jet-veto efficiencies in Higgs and $Z$-boson production at hadron colliders. Matching with next-to-next-to-leading order results allows us to provide a range of phenomenological predictions for the LHC, including cross-section results, detailed uncertainty estimates, and comparisons to current widely used tools.

We present a parameter-free postdiction of the high-$p_T$ charged-hadron nuclear modification factor ($R_{AA}$) in two centralities, measured by the CMS Collaboration in Pb-Pb collisions at the LHC. The evolution of the bulk medium is modeled using viscous fluid dynamics, with parameters adjusted to describe the soft hadron yields and elliptic flow. Assuming the dominance of radiative energy loss, we compute the medium modification of the $R_{AA}$ using a perturbative QCD-based formalism, the higher twist scheme. The transverse momentum diffusion coefficient $\widehat{q}$ is assumed to scale with the entropy density and is normalized by fitting the $R_{AA}$ in the most central Au-Au collisions at the Relativistic Heavy-Ion Collider. This setup is validated in noncentral Au-Au collisions at the Relativistic Heavy-Ion Collider and then extrapolated to Pb-Pb collisions at the LHC, keeping the relation between $\widehat{q}$ and entropy density unchanged. We obtain a satisfactory description of the CMS $R_{AA}$ over the $p_T$ range from 10 to 100 GeV.

Classical novae are important contributors to the abundances of key isotopes, such as the radioactive ${}^{18}\mathrm{F}$, whose observation by satellite missions could provide constraints on nucleosynthesis models in novae. The ${}^{17}\mathrm{O}(p,\gamma ){}^{18}\mathrm{F}$ reaction plays a critical role in the synthesis of both oxygen and fluorine isotopes, but its reaction rate is not well determined because of the lack of experimental data at energies relevant to novae explosions. In this study, the reaction cross section has been measured directly for the first time in a wide energy range $E_{\mathrm{c}.\mathrm{m}.}\simeq 200–370\mathrm{keV}$ appropriate to hydrogen burning in classical novae. In addition, the $E_{\mathrm{c}.\mathrm{m}.}=183\mathrm{keV}$ resonance strength, $\omega \gamma =1.67\pm 0.12\mu \mathrm{eV}$, has been measured with the highest precision to date. The uncertainty on the ${}^{17}\mathrm{O}(p,\gamma ){}^{18}\mathrm{F}$ reaction rate has been reduced by a factor of 4, thus leading to firmer constraints on accurate models of novae nucleosynthesis.

The interaction of an $E/A=70$-MeV ${}^7\mathrm{Be}$ beam with a Be target was used to populate levels in ${}^6\mathrm{Be}$ following neutron knockout reactions. The three-body decay of the ground and first excited states into the $\alpha +p+p$ exit channel were detected in the High Resolution Array. Precise three-body correlations extracted from the experimental data allowed us to obtain insight into the mechanism of the three-body democratic decay. The correlation data are in good agreement with a three-cluster-model calculation and thus validate this theoretical approach over a broad energy range.

We report on direct time-of-flight based mass measurements of 16 light neutron-rich nuclei. These include the first determination of the masses of the Borromean drip-line nuclei ${}^{19}\mathrm{B}$, ${}^{22}\mathrm{C}$, and ${}^{29}\mathrm{F}$ as well as that of ${}^{34}\mathrm{Na}$. In addition, the most precise determinations to date for ${}^{23}\mathrm{N}$ and ${}^{31}\mathrm{Ne}$ are reported. Coupled with recent interaction cross-section measurements, the present results support the occurrence of a two-neutron halo in ${}^{22}\mathrm{C}$, with a dominant $\nu 2s_{1/2}^2$ configuration, and a single-neutron halo in ${}^{31}\mathrm{Ne}$ with the valence neutron occupying predominantly the $2p_{3/2}$ orbital. Despite a very low two-neutron separation energy the development of a halo in ${}^{19}\mathrm{B}$ is hindered by the $1d_{5/2}^2$ character of the valence neutrons.

In this Letter, we study the impact of the inclusion of the recently measured beta decay properties of the ${}^{102;104;105;106;107}\mathrm{Tc}$, ${}^{105}\mathrm{Mo}$, and ${}^{101}\mathrm{Nb}$ nuclei in an updated calculation of the antineutrino energy spectra of the four fissible isotopes ${}^{235,238}\mathrm{U}$ and ${}^{239,241}\mathrm{Pu}$. These actinides are the main contributors to the fission processes in pressurized water reactors. The beta feeding probabilities of the above-mentioned Tc, Mo, and Nb isotopes have been found to play a major role in the $\gamma$ component of the decay heat of ${}^{239}\mathrm{Pu}$, solving a large part of the $\gamma$ discrepancy in the 4–3000 s range. They have been measured by using the total absorption technique, insensitive to the pandemonium effect. The calculations are performed by using the information available nowadays in the nuclear databases, summing all the contributions of the beta decay branches of the fission products. Our results provide a new prediction of the antineutrino energy spectra of ${}^{235}\mathrm{U}$, ${}^{239,241}\mathrm{Pu}$, and, in particular, ${}^{238}\mathrm{U}$ for which no measurement has been published yet. We conclude that new total absorption technique measurements are mandatory to improve the reliability of the predicted spectra.

We apply the sum-over-states approach to calculate partial contributions to parity nonconservation (PNC) in cesium [Porsev, Beloy, and Drevianko, Phys. Rev. Lett. 102, 181601 (2009)]. We find significant corrections to two nondominating terms coming from the contribution of the core and highly excited states ($n>9$, the so called tail). When these differences are taken into account the result of Porsev et al., $E_{\mathrm{PNC}}=0.8906(24)\times {10}^{-11}i(-Q_W/N)$ changes to 0.8977 (40), coming into good agreement with our previous calculations, 0.8980 (45). The interpretation of the PNC measurements in cesium still indicates reasonable agreement with the standard model ($1.5\sigma$); however, it gives new constraints on physics beyond it.

We have studied the influence of the local density of optical states (LDOS) on the rate and efficiency of Förster resonance energy transfer (FRET) from a donor to an acceptor. The donors and acceptors are dye molecules that are separated by a short strand of double-stranded DNA. The LDOS is controlled by carefully positioning the FRET pairs near a mirror. We find that the energy transfer efficiency changes with LDOS, and that, in agreement with theory, the energy transfer rate is independent of the LDOS, which allows one to quantitatively control FRET systems in a new way. Our results imply a change in the characteristic Förster distance, in contrast to common lore that this distance is fixed for a given FRET pair.

When a liquid drop impacts a solid surface, air is generally entrapped underneath. Using ultrafast x-ray phase-contrast imaging, we directly visualized the profile of an entrapped air film and its evolution into a bubble during drop impact. We identified a complicated evolution process that consists of three stages: inertial retraction of the air film, contraction of the top air surface into a bubble, and pinch-off of a daughter droplet inside the bubble. Energy transfer during retraction drives the contraction and pinch-off of a daughter droplet. The wettability of the solid surface affects the detachment of the bubble, suggesting a method for bubble elimination in many drop-impact applications.