We present an incisive spectroscopic technique for directly probing redox orbitals based on bulk electron momentum density measurements via high-resolution x-ray Compton scattering. Application of our method to spinel ${\mathrm{Li}}_x{\mathrm{Mn}}_2{\mathrm{O}}_4$, a lithium ion battery cathode material, is discussed. The orbital involved in the lithium insertion and extraction process is shown to mainly be the oxygen $2p$ orbital. Moreover, the manganese $3d$ states are shown to experience spatial delocalization involving $0.16\pm 0.05$ electrons per Mn site during the battery operation. Our analysis provides a clear understanding of the fundamental redox process involved in the working of a lithium ion battery.

Many models of earthquake faults have been introduced that connect Gutenberg-Richter (GR) scaling to triggering processes. However, natural earthquake fault systems are composed of a variety of different geometries and materials and the associated heterogeneity in physical properties can cause a variety of spatial and temporal behaviors. This raises the question of how the triggering process and the structure interact to produce the observed phenomena. Here we present a simple earthquake fault model based on the Olami-Feder-Christensen and Rundle-Jackson-Brown cellular automata models with long-range interactions that incorporates a fixed percentage of stronger sites, or asperity cells, into the lattice. These asperity cells are significantly stronger than the surrounding lattice sites but eventually rupture when the applied stress reaches their higher threshold stress. The introduction of these spatial heterogeneities results in temporal clustering in the model that mimics that seen in natural fault systems along with GR scaling. In addition, we observe sequences of activity that start with a gradually accelerating number of larger events (foreshocks) prior to a main shock that is followed by a tail of decreasing activity (aftershocks). This work provides further evidence that the spatial and temporal patterns observed in natural seismicity are strongly influenced by the underlying physical properties and are not solely the result of a simple cascade mechanism.

It is well known that the ground states of a Fermi liquid with and without a single Kondo impurity have an overlap that decays as a power law of the system size, expressing the Anderson orthogonality catastrophe. Ground states with two different values of the Kondo couplings have, however, a finite overlap in the thermodynamic limit. This overlap, which plays an important role in quantum quenches for impurity systems, is a universal function of the ratio of the corresponding Kondo temperatures, which is not accessible using perturbation theory or the Bethe ansatz. Using a strategy based on the integrable structure of the corresponding quantum field theory, we propose an exact formula for this overlap, which we check against extensive density matrix renormalization group calculations.

We derive an effective potential for binary black hole (BBH) spin precession at second post-Newtonian order. This effective potential allows us to solve the orbit-averaged spin-precession equations analytically for arbitrary mass ratios and spins. These solutions are quasiperiodic functions of time: after a fixed period, the BBH spins return to their initial relative orientations and jointly precess about the total angular momentum by a fixed angle. Using these solutions, we classify BBH spin precession into three distinct morphologies between which BBHs can transition during their inspiral. We also derive a precession-averaged evolution equation for the total angular momentum that can be integrated on the radiation-reaction time and identify a new class of spin-orbit resonances that can tilt the direction of the total angular momentum during the inspiral. Our new results will help efforts to model and interpret gravitational waves from generic BBH mergers and predict the distributions of final spins and gravitational recoils.

An annihilation signal of dark matter is searched for from the central region of the Milky Way. Data acquired in dedicated on-off observations of the Galactic center region with H.E.S.S. are analyzed for this purpose. No significant signal is found in a total of $\sim 9\mathrm{h}$ of on-off observations. Upper limits on the velocity averaged cross section, $⟨\sigma v⟩$, for the annihilation of dark matter particles with masses in the range of $\sim 300\mathrm{GeV}$ to $\sim 10\mathrm{TeV}$ are derived. In contrast to previous constraints derived from observations of the Galactic center region, the constraints that are derived here apply also under the assumption of a central core of constant dark matter density around the center of the Galaxy. Values of $⟨\sigma v⟩$ that are larger than $3\times {10}^{-24}{\mathrm{cm}}^3/\mathrm{s}$ are excluded for dark matter particles with masses between $\sim 1$ and $\sim 4\mathrm{TeV}$ at 95% C.L. if the radius of the central dark matter density core does not exceed 500 pc. This is the strongest constraint that is derived on $⟨\sigma v⟩$ for annihilating TeV mass dark matter without the assumption of a centrally cusped dark matter density distribution in the search region.

A method based on laser wakefield acceleration with controlled ionization injection triggered by another frequency-tripled laser is proposed, which can produce electron bunches with low energy spread. As two color pulses copropagate in the background plasma, the peak amplitude of the combined laser field is modulated in time and space during the laser propagation due to the plasma dispersion. Ionization injection occurs when the peak amplitude exceeds a certain threshold. The threshold is exceeded for limited duration periodically at different propagation distances, leading to multiple ionization injections and separated electron bunches. The method is demonstrated through multidimensional particle-in-cell simulations. Such electron bunches may be used to generate multichromatic x-ray sources for a variety of applications.

We report electrical resistivity, ac magnetic susceptibility, and x-ray absorption spectroscopy measurements of intermediate valence ${\mathrm{YbNi}}_3{\mathrm{Ga}}_9$ under pressure and magnetic field. We have revealed a characteristic pressure-induced Yb valence crossover within the temperature-pressure phase diagram, and a first-order metamagnetic transition is found below $P_c\sim 9\mathrm{GPa}$ where the system undergoes a pressure-induced antiferromagnetic transition. As a possible origin of the metamagnetic behavior, a critical valence fluctuation emerging near the critical point of the first-order valence transition is discussed on the basis of the temperature-field-pressure phase diagram.

Several experiments have been performed on $1T\text{−}{\mathrm{TiSe}}_2$ in order to identify whether the electronic structure is semimetallic or semiconducting without reaching a consensus. In this Letter, we theoretically study the impact of electron-hole and electron-phonon correlations on the bare semimetallic and semiconducting electronic structure. The resulting electron spectral functions provide a direct comparison of both cases and demonstrate that $1T\text{−}{\mathrm{TiSe}}_2$ is of predominant semiconducting character with some spectral weight crossing the Fermi level.

The transport properties at finite temperature of crystalline organic semiconductors are investigated, within the Su-Schrieffer-Heeger model, by combining an exact diagonalization technique, Monte Carlo approaches, and a maximum entropy method. The temperature-dependent mobility data measured in single crystals of rubrene are successfully reproduced: a crossover from super- to subdiffusive motion occurs in the range $150\le T\le 200\mathrm{K}$, where the mean free path becomes of the order of the lattice parameter and strong memory effects start to appear. We provide an effective model, which can successfully explain features of the absorption spectra at low frequencies. The observed response to slowly varying electric field is interpreted by means of a simple model where the interaction between the charge carrier and lattice polarization modes is simulated by a harmonic interaction between a fictitious particle and an electron embedded in a viscous fluid.

Liquid water molecules interact strongly with each other, forming a fluctuating hydrogen bond network and thereby giving rise to the anomalous phase diagram of liquid water. Consequently, symmetric and asymmetric water molecules have been found in the picosecond time average with IR and optical Raman spectroscopy. With subnatural linewidth resonant inelastic x-ray scattering (RIXS) at vibrational resolution, we take sub-femtosecond snapshots of the electronic and structural properties of water molecules in the hydrogen bond network. We derive a strong dominance of nonsymmetric molecules in liquid water in contrast to the gas phase on the sub-femtosecond timescale of RIXS and determine the fraction of highly asymmetrically distorted molecules.

We compute the length and time scales associated with resonant orbits around Kerr black holes for all orbital and spin parameters. Resonance-induced effects are potentially observable when the Event Horizon Telescope resolves the inner structure of Sgr A*, when space-based gravitational wave detectors record phase shifts in the waveform during the resonant passage of a compact object spiraling into the black hole, or in the frequencies of quasiperiodic oscillations for accreting black holes. The onset of geodesic chaos for non-Kerr spacetimes should occur at the resonance locations quantified here.

We present results from the evolution of spacetimes that describe the merger of asymptotically global anti–de Sitter black holes in 5D with an SO(3) symmetry. Prompt scalar field collapse provides us with a mechanism for producing distinct trapped regions on the initial slice, associated with black holes initially at rest. We evolve these black holes towards a merger, and follow the subsequent ring down. The boundary stress tensor of the dual conformal field theory is conformally related to a stress tensor in Minkowski space that inherits an axial symmetry from the bulk SO(3). We compare this boundary stress tensor to its hydrodynamic counterpart with viscous corrections of up to second order, and compare the conformally related stress tensor to ideal hydrodynamic simulations in Minkowski space, initialized at various time slices of the boundary data. Our findings reveal far-from-hydrodynamic behavior at early times, with a transition to ideal hydrodynamics at late times.

We present a state-of-the-art determination of the complex valued static quark-antiquark potential at phenomenologically relevant temperatures around the deconfinement phase transition. Its values are obtained from nonperturbative lattice QCD simulations using spectral functions extracted via a novel Bayesian inference prescription. We find that the real part, both in a gluonic medium, as well as in realistic QCD with light $u$, $d$, and $s$ quarks, lies close to the color singlet free energies in Coulomb gauge and shows Debye screening above the (pseudo)critical temperature $T_c$. The imaginary part is estimated in the gluonic medium, where we find that it is of the same order of magnitude as in hard-thermal loop resummed perturbation theory in the deconfined phase.

A pair of transverse wobbling bands is observed in the nucleus ${}^{135}\mathrm{Pr}$. The wobbling is characterized by $\mathrm{\Delta }I=1$, $E2$ transitions between the bands, and a decrease in the wobbling energy confirms its transverse nature. Additionally, a transition from transverse wobbling to a three-quasiparticle band comprised of strong magnetic dipole transitions is observed. These observations conform well to results from calculations with the tilted axis cranking model and the quasiparticle rotor model.

The intermediate domain of strong-field ionization between the tunneling and multiphoton regimes is investigated using the strong-field approximation and the imaginary-time method. An intuitive model for the dynamics is developed which describes the ionization process within a nonadiabatic tunneling picture with a coordinate dependent electron energy during the under-the-barrier motion. The nonadiabatic effects in the elliptically polarized laser field induce a transversal momentum shift of the tunneled electron wave packet at the tunnel exit and a delayed appearance in the continuum as well as a shift of the tunneling exit towards the ionic core. The latter significantly modifies the Coulomb focusing during the electron excursion in the laser field after exiting the ionization tunnel. We show that nonadiabatic effects are especially large when the Coulomb field of the ionic core is taken into account during the under-the-barrier motion. The simple man model modified with these nonadiabatic corrections provides an intuitive background for exact theories and has direct implications for the calibration of the attoclock technique.

The interaction between the endohedral unit in the single-molecule magnet ${\mathrm{Dy}}_2\mathrm{ScN}@{\mathrm{C}}_{80}$ and a rhodium (111) substrate leads to alignment of the Dy $4f$ orbitals. The resulting orientation of the ${\mathrm{Dy}}_2\mathrm{ScN}$ plane parallel to the surface is inferred from comparison of the angular anisotropy of x-ray absorption spectra and multiplet calculations in the corresponding ligand field. The x-ray magnetic circular dichroism is also angle dependent and signals strong magnetocrystalline anisotropy. This directly relates geometric and magnetic structure. Element specific magnetization curves from different coverages exhibit hysteresis at a sample temperature of $\sim 4\mathrm{K}$. From the measured hysteresis curves, we estimate the zero field remanence lifetime during x-ray exposure of a submonolayer to be about 30 seconds.

In neural circuits, statistical connectivity rules strongly depend on cell-type identity. We study dynamics of neural networks with cell-type-specific connectivity by extending the dynamic mean-field method and find that these networks exhibit a phase transition between silent and chaotic activity. By analyzing the locus of this transition, we derive a new result in random matrix theory: the spectral radius of a random connectivity matrix with block-structured variances. We apply our results to show how a small group of hyperexcitable neurons within the network can significantly increase the network’s computational capacity by bringing it into the chaotic regime.

We report here magnetic resonance imaging measurements performed on suspensions with a bulk solid volume fraction (${\varphi }_0$) up to 0.55 flowing in a pipe. We visualize and quantify spatial distributions of $\varphi$ and velocity across the pipe at different axial positions. For dense suspensions (${\varphi }_0>0.5$), we found a different behavior compared to the known cases of lower ${\varphi }_0$. Our experimental results demonstrate compaction within the jammed region (characterized by a zero macroscopic shear rate) from the jamming limit ${\varphi }_m\approx 0.58$ at its outer boundary to the random close packing limit ${\varphi }_{\text{rcp}}\approx 0.64$ at the center. Additionally, we show that $\varphi$ and velocity profiles can be fairly well captured by a frictional rheology accounting for both further compaction of jammed regions as well as normal stress differences.