We reexamine the azimuthal angle dependence of the local spin polarization of hyperons in heavy ion collisions at 200 GeV in the framework of the $\left(3+1\right)$-dimensional viscous hydrodynamic model CLVisc. Two different initial conditions are considered in our simulation: the optical Glauber initial condition without an initial orbital angular momentum and the AMPT initial condition with an initial orbital angular momentum. We find that the azimuthal angle dependence of the hyperon polarization strongly depends on the choice of the so-called spin chemical potential ${\mathrm{\Omega }}_{\mu \nu }$. With ${\mathrm{\Omega }}_{\mu \nu }$ chosen to be proportional to the temperature vorticity, our simulation shows qualitatively coincidental results with the recent measurements at the BNL Relativistic Heavy Ion Collider for both the longitudinal and the transverse polarization. We argue that such a coincidence may be related to the fact that the temperature vorticity is approximately conserved in the hot quark-gluon matter.

A many-particle system must possess long-range interactions in order to be hyperuniform at thermal equilibrium. Hydrodynamic arguments and numerical simulations show, nevertheless, that a three-dimensional elastic-line array with short-ranged repulsive interactions, such as vortex matter in a type-II superconductor, forms at equilibrium a class-II hyperuniform two-dimensional point pattern for any constant-$z$ cross section. In this case, density fluctuations vanish isotropically as $\sim q^{\alpha }$ at small wave vectors $q$, with $\alpha =1$. This prediction includes the solid and liquid vortex phases in the ideal clean case and the liquid in presence of weak uncorrelated disorder. We also show that the three-dimensional Bragg glass phase is marginally hyperuniform, while the Bose glass and the liquid phase with correlated disorder are expected to be nonhyperuniform at equilibrium. Furthermore, we compare these predictions with experimental results on the large-wavelength vortex density fluctuations of magnetically decorated vortex structures nucleated in pristine, electron-irradiated, and heavy-ion-irradiated superconducting ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+\delta }$ samples in the mixed state. For most cases, we find hyperuniform two-dimensional point patterns at the superconductor surface with an effective exponent ${\alpha }_{\text{eff}}\approx 1$. We interpret these results in terms of a large-scale memory of the high-temperature line-liquid phase retained in the glassy dynamics when field cooling the vortex structures into the solid phase. We also discuss the crossovers expected from the dispersivity of the elastic constants at intermediate length-scales, and the lack of hyperuniformity in the $x\text{−}y$ plane for lengths $q^{-1}$ larger than the sample thickness due to finite-size effects in the $z$ direction. We argue these predictions may be observable and propose further imaging experiments to test them independently.

A common difficulty in applications of machine learning is the lack of any general principle for guiding the choices of key parameters of the underlying neural network. Focusing on a class of recurrent neural networks—reservoir computing systems, which have recently been exploited for model-free prediction of nonlinear dynamical systems—we uncover a surprising phenomenon: the emergence of an interval in the spectral radius of the neural network in which the prediction error is minimized. In a three-dimensional representation of the error versus the time and spectral radius, the interval corresponds to the bottom region of a “valley.” Such a valley arises for a variety of spatiotemporal dynamical systems described by nonlinear partial differential equations, regardless of the structure and the edge-weight distribution of the underlying reservoir network. We also find that, while the particular location and size of the valley depend on the details of the target system to be predicted, the interval tends to be larger for undirected than for directed networks. The valley phenomenon can be beneficial to the design of optimal reservoir computing, representing a small step forward in understanding these machine-learning systems.

We find that the Hanford and Livingston detectors of Advanced LIGO derive a distinct posterior probability distribution of binary tidal deformability $\tilde{\mathrm{\Lambda }}$ of the first binary-neutron-star merger GW170817. By analyzing public data of GW170817 with a nested-sampling engine and the default TaylorF2 waveform provided by the LALInference package, the probability distribution of the binary tidal deformability derived by the LIGO-Virgo detector network turns out to be determined dominantly by the Hanford detector. Specifically, by imposing the flat prior on tidal deformability of individual stars, symmetric 90% credible intervals of $\tilde{\mathrm{\Lambda }}$ are estimated to be ${527}_{-345}^{+619}$ with the Hanford detector, ${927}_{-619}^{+522}$ with the Livingston detector, and ${455}_{-281}^{+668}$ with the LIGO-Virgo detector network. Furthermore, the distribution derived by the Livingston detector changes irregularly when we vary the maximum frequency of the data used in the analysis. This feature is not observed for the Hanford detector. While they are all consistent, the discrepancy and irregular behavior suggest that an in-depth study of noise properties might improve our understanding of GW170817 and future events.

Recently, it was realized that anomalies can be completely classified by topological orders, symmetry protected topological orders, and symmetry enriched topological orders in one higher dimension. The anomalies that people used to study are invertible anomalies that correspond to invertible topological orders and/or symmetry protected topological orders in one higher dimension. In this paper, we introduce a notion of noninvertible anomaly, which describes the boundary of generic topological order. It is characterized by two features. First, a theory with noninvertible anomaly has a multicomponent partition function. Second, under the mapping class group transformation of space-time, the vector of partition functions transform covariantly. In fact, the anomalous partition functions transform in the same way as the degenerate ground states of the corresponding topological order in one higher dimension. This general theory of noninvertible anomaly may have wide applications. As an example, we show that the irreducible gapless boundary of 2+1D double-semion topological order must have central charge $c=\overline{c}>\frac{25}{28}$.

Vortices are localized planar structures that attain topological stability and can be used to describe collective behavior in a diversity of situations of current interest in nonlinear science. In high-energy physics, vortices engender an integer winding number and appear under the presence of a local Abelian symmetry. In this work, we study vortices in a Maxwell-Higgs model, in which the gauge symmetry is enhanced to accommodate additional symmetries, responsible to generate localized structures to be used to constrain the vortex structure in a given region in the plane. The main aim is to examine how the vortex profile changes when it inhabits a limited region, an issue of current interest to the study of vortices at the nanometric scale.

Antiferromagnets (AFMs) are widely believed to be superior to ferromagnets in spintronics because of their high stability due to the vanishingly small stray field. It is thus expected that the order parameter of AFMs should always align along the easy axis of the crystalline anisotropy. In contrast to this conventional wisdom, we find that the AFM order parameter switches away from the easy axis below a critical anisotropy strength when an AFM is properly tailored into a nanostructure. The switching time first decreases and then increases with the damping. Above the critical anisotropy, the AFM order parameter is stable and precesses under a microwave excitation. However, the absorption peak is not at resonance frequency even for magnetic damping as low as 0.01. To resolve these anomalies, we first ascertain the hidden role of dipolar interaction that reconstructs the energy landscape of the nanosystem and propose a model of a damped nonlinear pendulum to explain the switching behavior. In this framework, the second anomaly appears when an AFM is close to the boundary between underdamped and overdamped phases, where the observed absorption line shape has a small quality factor and thus is not reliable any longer. Our results should be significant to extract the magnetic parameters through resonance techniques.

We show that in a generic, ergodic quantum many-body system the interactions induce a nontrivial topology for an arbitrarily small non-Hermitian component of the Hamiltonian. This is due to an exponential-in-system-size proliferation of exceptional points which have the Hermitian limit as an accumulation (hyper)surface. The nearest-neighbor level repulsion characterizing Hermitian ergodic many-body systems is thus shown to be a projection of a richer phenomenology, where actually all the exponentially many eigenvalues are pairwise connected in a topologically robust fashion via exceptional points.

The photofragmentation behavior of the lead-doped bismuth cluster ${}^{209}\mathrm{Bi}_7{}^{208}\mathrm{Pb}^{+}$ is investigated by use of multi-reflection time-of-flight mass spectrometry (MR-ToF MS), which serves both as precursor selector on a scale of single atomic mass units as well as high-resolution fragment analyzer. This is an implementation of a tandem MR-ToF study, where two instances of high-resolution mass spectrometry are used, namely for pre-selection and post-excitation analysis, in quick succession within a single device to determine complex dissociation patterns. The full information of the fragmentation pathways is obtained, including branching ratios describing the retention of the charge on the pure or compound cluster. The results are compared to the behavior of the analogous pure bismuth cluster ${}^{209}\mathrm{Bi}_8^{+}$ and interpreted within the framework of well-established cluster stability rules.

The interplay between spin and orbital angular momentum in the up-conversion process allows us to control the macroscopic wave front of high harmonics by manipulating the microscopic polarizations of the driving field. We demonstrate the control of orbital angular momentum in high-harmonic generation from both solid- and gas-phase targets using the selection rules of spin angular momentum. The gas-phase harmonics extend the control of angular momentum to the extreme-ultraviolet wavelength. We also propose a bicolor scheme to produce spectrally separated extreme-ultraviolet radiation carrying orbital angular momentum.

It is known that, under the presence of a static external magnetic field $B_e$, an electromagnetic field rotates its polarization axes (Faraday rotation) when transmitted across a graphene single layer. Graphene provides record values of Faraday angle per layer thickness, but at frequencies of the order of the cyclotron frequency. This impedes applications, as fields of the order of 10 T would be required even for terahertz operation. Here we show that this condition is relaxed in strained graphene, where the potentially large induced pseudomagnetic field $B_{\text{ps}}$, when combined with a small $B_e$ (needed to break time-reversal symmetry), provides large Faraday rotation at arbitrary frequencies. It is found that the Faraday rotation in this system presents a very rich dependence on all different parameters, being greatly enhanced when the number of occupied Landau levels (governed by $B_e\pm B_{\text{ps}}$) is different in the two graphene valleys.

We observe a set of three replica luminescent peaks at ∼21.4 meV below the dark exciton, and negative and positive dark trions (or exciton polarons) in monolayer $\mathrm{WS}{\mathrm{e}}_2$. The replica redshift energy matches the energy of the zone-center $E^{\prime \prime }$-mode optical phonons. The phonon replicas exhibit a parallel gate dependence and the same $g$-factors as the dark excitonic states, but follow the valley selection rules of the bright excitonic states. While the dark states exhibit an out-of-plane transition dipole and valley-independent linearly polarized emission in the in-plane directions, their phonon replicas exhibit an in-plane transition dipole and valley-dependent circularly polarized emission in the out-of-plane directions. Our results and symmetry analysis show that the $K$-valley dark exciton decays into a left-handed chiral phonon and a right-handed photon, whereas the $K^{\prime }$-valley dark exciton decays into a right-handed chiral phonon and a left-handed photon. Such valley selection rules of chiral phonon replicas can be utilized to identify the valleys of the dark excitonic states and explore their chiral interactions with phonons.

The information convex allows us to look into certain information-theoretic constraints in two-dimensional topological orders. We provide a derivation of the topological contribution $ln{d}_a$ to the von Neumann entropy, where $d_a$ is the quantum dimension of anyon $a$. This value emerges as the only value consistent with strong subadditivity, assuming a certain topological dependence of the information convex structure. In particular, it is assumed that the fusion multiplicities are coherently encoded in a two-hole disk. A similar contribution ($ln{d}_{\alpha }$) is derived for gapped boundaries. This method further allows us to identify the fusion probabilities and certain constraints on the fusion theory. We also derive a linear bound on the circuit depth of unitary non-Abelian string operators and discuss how it generalizes and changes in the presence of a gapped boundary.

We show that the failure time ${\tau }_f$ in the fiber bundle model, taken as a prototype of heterogeneous materials, depends crucially on the strength of the disorder $\delta$ and the stress release range $R$ in the model. In the mean-field limit, the distribution of ${\tau }_f$ is log-normal. In this limit, the average failure time shows the variation ${\tau }_f\sim L^{\alpha \left(\delta \right)}$, where $L$ is the system size. The exponent $\alpha$ has a constant value above a critical disorder ${\delta }_c$ ($=1/6$), while it is an increasing function of $\delta$ in the region $\delta <{\delta }_c$. On the other hand, in the limit where the local stress concentration plays a crucial role, we observe the scaling ${\tau }_f\sim L^{\alpha \left(\delta \right)}\mathrm{\Phi }(R/L^{1-\alpha \left(\delta \right)})$, where $R$ is the stress release range. We find that the crossover length scale $R_c$, between the above two limiting cases, scales as $R_c\sim L^{1-\alpha \left(\delta \right)}$.

Strong coupling of electric transition dipoles with optical or plasmonic resonators modifies their light-matter interaction and, therefore, their optical spectra. Semiconducting $\mathrm{W}{\mathrm{S}}_2$ nanotubes intrinsically provide the dipoles through their excitonic resonances, and the optical cavity via their cylindrical shape. We investigate the nonequilibrium light-matter interaction in $\mathrm{W}{\mathrm{S}}_2$ nanotubes in the time domain using femtosecond transient extinction spectroscopy. We develop a phenomenological coupled oscillator model with time-dependent parameters to describe the transient extinction spectra, allowing us to extract the underlying nonequilibrium electron dynamics. We find that the exciton and trion resonances shift due to many-body effects of the photogenerated charge carriers and their population dynamics on the femto- and picosecond timescale. Our results show that the time-dependent phenomenological model quantitatively reproduces the nonequilibrium optical response of strongly coupled systems.

We report on a chiral observable upon ionization of a chiral molecule (methyloxirane) by a strong elliptically polarized laser field: a rotation of the photoelectron momentum distribution, which is enantiosensitive and forward/backward asymmetric. We explain this forward/backward asymmetric rotation of the count maxima to be equivalent to a dependence of the photoelectron circular dichroism on the electron emission angle in the plane of polarization.

There is a remarkable interest in the study of out-of-time ordered correlators (OTOCs) that goes from many-body theory and high-energy physics to quantum chaos. In the latter case there is a special focus on the comparison with the traditional measures of quantum complexity such as the spectral statistics. The exponential growth has been verified for many paradigmatic maps and systems. However, less is known for multipartite cases. On the other hand, the recently introduced Wigner separability entropy (WSE) and its classical counterpart provide a complexity measure that treats equally quantum and classical distributions in phase space. We compare the behavior of these measures in a system consisting of two coupled and perturbed cat maps with different dynamics: double hyperbolic, double elliptic, and mixed. In all cases, we find that the OTOCs and the WSE have essentially the same behavior, providing a complete characterization in generic bipartite systems and at the same time revealing them as very good measures of quantum complexity for phase-space distributions. Moreover, we establish a relation between both quantities by means of a recently proven theorem linking the second Rényi entropy and OTOCs.

We study the dynamics and pairwise interactions of dark soliton stripes in the two-dimensional defocusing nonlinear Schrödinger equation. By employing a variational approach we reduce the dynamics for dark soliton stripes to a set of coupled one-dimensional “filament” equations of motion for the position and velocity of the stripe. The method yields good qualitative agreement with the numerical results for the transverse instability of the stripes. We propose a phenomenological amendment that also significantly improves the quantitative agreement of the method with the computations. Subsequently, the method is extended for a pair of symmetric dark soliton stripes that include the mutual interactions between the filaments. The reduced equations of motion are compared with a recently proposed adiabatic invariant method and its corresponding findings and are found to provide a more adequate representation of the original full dynamics for a wide range of cases encompassing perturbations with long and short wavelengths, and combinations thereof.

Community structure and interaction delays are common features of ensembles of network coupled oscillators, but their combined effect on the emergence of synchronization has not been studied in detail. We study the transitions between macroscopic states in coupled oscillator systems with community structure and time delays. We show that the combination of these two properties gives rise to nonmonotonic transitions, whereby increasing the global coupling strength can both inhibit and promote synchronization, yielding both desynchronization and synchronization transitions. For relatively wide parameter choices, we also observe asymmetric suppression of synchronization, where communities compete to suppress one another's synchronization properties until one or more win, totally suppressing the others to effective incoherence. Using the ansatz of Ott and Antonsen, we provide analytical descriptions for these transitions that confirm numerical simulations.

In this paper, a Fréedericksz-like positional transition is found for a spherical microdroplet suspended in a nematic liquid crystal cell in the presence of an external electric field. Based on the numerical calculation of elastic energy using the Green's function method, the equilibrium position of the microdroplet is decided through a competition between the buoyant force and the effective force built by the elastic energy gradient existing inside the nematic liquid crystal cell. It is shown that elastic energy dominates the kinetics of the microdroplet until the external field applied reaches a critical value large enough to flatten the elastic energy contour in the central region, which provides a “fast lane” enabling the asymmetric buoyant force to drive the liquid droplet abruptly from the cell midplane to a new equilibrium position, triggering a positional transition. It is also found that such a threshold value of external field depends on thickness $L$ and Frank elastic constant $K$, in a Fréedericksz-like manner, but multiplied by a factor of $3\sqrt{\pi }$. An explicit formula proposed for the critical electric field agrees extremely well with the numerical calculation.