We demonstrate that measurements of rapidity differential anisotropic flow in heavy-ion collisions can constrain the temperature dependence of the shear viscosity to entropy density ratio $\eta /s$ of QCD matter. Comparing results from hydrodynamic calculations with experimental data from the RHIC, we find evidence for a small $\eta /s\approx 0.04$ in the QCD crossover region and a strong temperature dependence in the hadronic phase. A temperature independent $\eta /s$ is disfavored by the data. We further show that measurements of the event-by-event flow as a function of rapidity can be used to independently constrain the initial state fluctuations in three dimensions and the temperature dependent transport properties of QCD matter.

We report the first observation of localized modulation of turbulent density fluctuations $\tilde{n}$ (via beam emission spectroscopy) by neoclassical tearing modes (NTMs) in the core of the DIII-D tokamak. NTMs are important as they often lead to severe degradation of plasma confinement and disruptions in high-confinement fusion experiments. Magnetic islands associated with NTMs significantly modify the profiles and turbulence drives. In this experiment $\tilde{n}$ was found to be modulated by 14% across the island. Gyrokinetic simulations suggest that $\tilde{n}$ could be dominantly driven by the ion temperature gradient instability.

The question of the nature of water’s glass transition has continued to be disputed over many years. Here we use slow heating scans ($0.4\mathrm{K}{\min }^{-1}$) of compact amorphous solid water deposited at 77 K and an analysis of the accompanying changes in the small-angle neutron scattering signal, to study mesoscale changes in the ice network topology. From the data we infer the onset of rotational diffusion at 115 K, a sudden switchover from nondiffusive motion and enthalpy relaxation of the network at $<121\mathrm{K}$ to diffusive motion across sample grains and sudden pore collapse at $>121\mathrm{K}$, in excellent agreement with the glass transition onset deduced from heat capacity and dielectric measurements. This indicates that water’s glass transition is linked with long-range transport of water molecules on the time scale of minutes and, thus, clarifies its nature. Furthermore, the slow heating rates combined with the high crystallization resistance of the amorphous sample allow us to identify the glass transition end point at 136 K, which is well separated from the crystallization onset at 144 K—in contrast to all earlier experiments in the field.

A hidden order that emerges in the frustrated pyrochlore ${\mathrm{Tb}}_{2+x}{\mathrm{Ti}}_{2-x}{\mathrm{O}}_{7+y}$ with $T_c=0.53\mathrm{K}$ is studied using specific heat, magnetization, and neutron scattering experiments on a high-quality single crystal. Semiquantitative analyses based on a pseudospin-$1/2$ Hamiltonian for ionic non-Kramers magnetic doublets demonstrate that it is an ordered state of electric quadrupole moments. The elusive spin liquid state of the nominal ${\mathrm{Tb}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ is most likely a $\mathrm{U}(1)$ quantum spin-liquid state.

Manipulating and controlling the optical energy flow inside random media is a research frontier of photonics and the basis of novel laser designs. Here, we show that a metamaterial consisting of randomly dispersed graphene nanoflakes embedded within an optically pumped gain medium (rhodamine 6G) can operate as a cavity-free laser thanks to its extraordinarily low threshold for saturable absorption. The emitted light is self-organized into a well-determined spatial pattern, which depends on the graphene flake density and can be externally controlled through the optical pump. We provide different examples of tunable laser operation ranging from stable single-mode to chaoticlike behavior. Our metamaterial design holds great potential for the optical control of light amplification, as well as for the development of single-mode beam-engineered cavity-free lasers.

We study a model of bacterial dynamics where two interacting random walkers perform run-and-tumble motion on a one-dimensional lattice under mutual exclusion and find an exact expression for the probability distribution in the steady state. This stationary distribution has a rich structure comprising three components: a jammed component, where the particles are adjacent and block each other; an attractive component, where the probability distribution for the distance between particles decays exponentially; and an extended component in which the distance between particles is uniformly distributed. The attraction between the particles is sufficiently strong that even in the limit where continuous space is recovered for a finite system, the two walkers spend a finite fraction of time in a jammed configuration. Our results potentially provide a route to understanding the motility-induced phase separation characteristic of active matter from a microscopic perspective.

We study weak coupling perturbative series in 4D $\mathcal{N}=2$ and 5D $\mathcal{N}=1$ supersymmetric gauge theories with Lagrangians. We prove that the perturbative series of these theories in the zero-instanton sector are Borel summable for various observables. Our result for the 4D $\mathcal{N}=2$ case supports an expectation from a recent proposal on a semiclassical realization of infrared renormalons in QCD-like theories, where the semiclassical solution does not exist in $\mathcal{N}=2$ theories and the perturbative series are unambiguous, namely, Borel summable. We also prove that the perturbative series in an arbitrary number of instanton sectors are Borel summable for a wide class of theories. It turns out that exact results can be obtained by summing over the Borel resummations with every instanton number.

The strong dependence of Coulomb energies on nuclear radii makes it possible to extract the latter from calculations of the former. The resulting estimates of neutron skins indicate that two mechanisms are involved. The first one—isovector monopole polarizability—amounts to noting that when a particle is added to a system it drives the radii of neutrons and protons in different directions, tending to equalize the radii of both fluids independently of the neutron excess. This mechanism is well understood and the Duflo-Zuker (small) neutron skin values derived 14 years ago are consistent with recent measures and estimates. The alternative mechanism involves halo orbits whose huge sizes tend to make the neutron skins larger and have a subtle influence on the radial behavior of $sd$ and $pf$ shell nuclei. In particular, they account for the sudden rise in the isotope shifts of nuclei beyond $N=28$ and the near constancy of radii in the $A=40–56$ region. This mechanism, detected here for the first time, is not well understood and may well go beyond the Efimov physics usually associated with halo orbits.

We present a new type of colossal magnetoresistance (CMR) arising from an anomalous collapse of the Mott insulating state via a modest magnetic field in a bilayer ruthenate, Ti-doped ${\mathrm{Ca}}_3{\mathrm{Ru}}_2{\mathrm{O}}_7$. Such an insulator-metal transition is accompanied by changes in both lattice and magnetic structures. Our findings have important implications because a magnetic field usually stabilizes the insulating ground state in a Mott-Hubbard system, thus calling for a deeper theoretical study to reexamine the magnetic field tuning of Mott systems with magnetic and electronic instabilities and spin-lattice-charge coupling. This study further provides a model approach to search for CMR systems other than manganites, such as Mott insulators in the vicinity of the boundary between competing phases.

We construct condensate states encoding the continuum spherically symmetric quantum geometry of a horizon in full quantum gravity, i.e., without any classical symmetry reduction, in the group field theory formalism. Tracing over the bulk degrees of freedom, we show how the resulting reduced density matrix manifestly exhibits a holographic behavior. We derive a complete orthonormal basis of eigenstates for the reduced density matrix of the horizon and use it to compute the horizon entanglement entropy. By imposing consistency with the horizon boundary conditions and semiclassical thermodynamical properties, we recover the Bekenstein-Hawking entropy formula for any value of the Immirzi parameter. Our analysis supports the equivalence between the von Neumann (entanglement) entropy interpretation and the Boltzmann (statistical) one.

We propose a nonperturbative gauge-invariant regulator for $d$-dimensional chiral gauge theories on the lattice. The method involves simulating domain wall fermions in $d+1$ dimensions with quantum gauge fields that reside on one $d$-dimensional surface and are extended into the bulk via gradient flow. The result is a theory of gauged fermions plus mirror fermions, where the mirror fermions couple to the gauge fields via a form factor that becomes exponentially soft with the separation between domain walls. The resultant theory has a local $d$-dimensional interpretation only if the chiral fermion representation is anomaly free. A physical realization of this construction would imply the existence of mirror fermions in the standard model that are invisible except for interactions induced by vacuum topology, and which could gravitate differently than conventional matter.

The RENO experiment has analyzed about 500 live days of data to observe an energy dependent disappearance of reactor ${\overline{\nu }}_e$ by comparing their prompt signal spectra measured in two identical near and far detectors. In the period between August of 2011 and January of 2013, the far (near) detector observed 31 541 (290 775) electron antineutrino candidate events with a background fraction of 4.9% (2.8%). The measured prompt spectra show an excess of reactor ${\overline{\nu }}_e$ around 5 MeV relative to the prediction from a most commonly used model. A clear energy and baseline dependent disappearance of reactor ${\overline{\nu }}_e$ is observed in the deficit of the observed number of ${\overline{\nu }}_e$. Based on the measured far-to-near ratio of prompt spectra, we obtain ${\sin }^{2}2{\theta }_{13}=0.082\pm 0.009(\text{stat})\pm 0.006(\text{syst})$ and $|\mathrm{\Delta }{m}_{ee}^2|=[2.62_{-0.23}^{+0.21}(\text{stat}{)}_{-0.13}^{+0.12}(\text{syst})]\times {10}^{-3}{\mathrm{eV}}^2$.

We report the analysis of the three-body $e^{+}{e}^{-}\to B\overline{B}{\pi }^{\pm }$, $B{\overline{B}}^{*}{\pi }^{\pm }$, and $B^{*}{\overline{B}}^{*}{\pi }^{\pm }$ processes, including the first observations of the $Z_b^{\pm }(10610)\to [B{\overline{B}}^{*}+\mathrm{c}.\mathrm{c}.{]}^{\pm }$ and $Z_b^{\pm }(10650)\to [B^{*}{\overline{B}}^{*}{]}^{\pm }$ transitions that are found to dominate the corresponding final states. We measure Born cross sections for the three-body production of $\sigma (e^{+}{e}^{-}\to [B{\overline{B}}^{*}+\mathrm{c}.\mathrm{c}.{]}^{\pm }{\pi }^{\mp })=[17.4\pm 1.6(\text{stat})\pm 1.9(\text{syst})]\mathrm{pb}$ and $\sigma (e^{+}{e}^{-}\to [B^{*}{\overline{B}}^{*}{]}^{\pm }{\pi }^{\mp })=[8.75\pm 1.15(\text{stat})\pm 1.04(\text{syst})]\mathrm{pb}$ and set a 90% C.L. upper limit of $\sigma (e^{+}{e}^{-}\to [B\overline{B}{]}^{\pm }{\pi }^{\mp })<2.9\mathrm{pb}$. The results are based on a $121.4{\mathrm{fb}}^{-1}$ data sample collected with the Belle detector at a center-of-mass energy near the $\mathrm{\Upsilon }(10860)$ peak.

We present a fully differential next-to-next-to-leading order calculation of charm-quark production in charged-current deep-inelastic scattering, with full charm-quark mass dependence. The next-to-next-to-leading order corrections in perturbative quantum chromodynamics are found to be comparable in size to the next-to-leading order corrections in certain kinematic regions. We compare our predictions with data on dimuon production in (anti)neutrino scattering from a heavy nucleus. Our results can be used to improve the extraction of the parton distribution function of a strange quark in the nucleon.

We explore a prototypical two-dimensional massive model of the nonlinear Dirac type and examine its solitary wave and vortex solutions. In addition to identifying the stationary states, we provide a systematic spectral stability analysis, illustrating the potential of spinor solutions to be neutrally stable in a wide parametric interval of frequencies. Solutions of higher vorticity are generically unstable and split into lower charge vortices in a way that preserves the total vorticity. These conclusions are found not to be restricted to the case of cubic two-dimensional nonlinearities but are found to be extended to the case of quintic nonlinearity, as well as to that of three spatial dimensions. Our results also reveal nontrivial differences with respect to the better understood nonrelativistic analogue of the model, namely the nonlinear Schrödinger equation.

The spin-orbit Mott insulator ${\mathrm{Sr}}_3{\mathrm{Ir}}_2{\mathrm{O}}_7$ provides a fascinating playground to explore insulator-metal transition driven by intertwined charge, spin, and lattice degrees of freedom. Here, we report high-pressure electric resistance and resonant inelastic x-ray scattering measurements on single-crystal ${\mathrm{Sr}}_3{\mathrm{Ir}}_2{\mathrm{O}}_7$ up to 63–65 GPa at 300 K. The material becomes a confined metal at 59.5 GPa, showing metallicity in the $ab$ plane but an insulating behavior along the $c$ axis. Such an unusual phenomenon resembles the strange metal phase in cuprate superconductors. Since there is no sign of the collapse of spin-orbit or Coulomb interactions in x-ray measurements, this novel insulator-metal transition is potentially driven by a first-order structural change at nearby pressures. Our discovery points to a new approach for synthesizing functional materials.