The QCD axion needs not be an exact pseudoscalar for solving the strong $CP$ problem. Its imperfectness can play a profound role cosmologically. We propose effective operators, where the Peccei-Quinn field linearly couples to standard model particles, provide a dynamical solution to the domain wall problem that prevails in postinflationary axion models with discrete symmetry. Such interactions generate a thermal potential that drives the axion field to a universal value throughout the Universe at high temperatures thus preventing the birth of domain walls when the QCD potential switches on. We discuss generic conditions for this mechanism to work and several concrete examples. Combining with existing electric dipole moment and fifth force constraints, a lower bound on the axion mass is obtained around ${10}^{-5}\mathrm{eV}$. Our findings make a strong case for complementary axion searches with both quality preserving and violating interactions.

The first observation of the singly Cabibbo-suppressed ${\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{K}^{+}$ and ${\mathrm{\Omega }}_c^0\to {\mathrm{\Xi }}^{-}{\pi }^{+}$ decays is reported, using proton-proton collision data at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$, collected with the LHCb detector between 2016 and 2018. The branching fraction ratios are measured to be $\frac{\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{K}^{+})}{\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{\pi }^{+})}=[6.08\pm 0.51(\mathrm{stat})\pm 0.40(\mathrm{syst})]\%,\frac{\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Xi }}^{-}{\pi }^{+})}{\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{\pi }^{+})}=[15.81\pm 0.87(\mathrm{stat})\pm 0.44(\mathrm{syst})\pm 0.16(\mathrm{ext})]\%.$ In addition, using the ${\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{\pi }^{+}$ decay channel, the ${\mathrm{\Omega }}_c^0$ baryon mass is measured to be $M({\mathrm{\Omega }}_c^0)=2695.28\pm 0.07(\mathrm{stat})\pm 0.27(\mathrm{syst})\pm 0.30(\mathrm{ext})\mathrm{MeV},$ improving the precision of the previous world average by a factor of 4.

We demonstrate a silicon-based electron accelerator that uses laser optical near fields to both accelerate and confine electrons over extended distances. Two dielectric laser accelerator (DLA) designs were tested, each consisting of two arrays of silicon pillars pumped symmetrically by pulse front tilted laser beams, designed for average acceleration gradients 35 and $50\mathrm{MeV}/\mathrm{m}$, respectively. The DLAs are designed to act as alternating phase focusing (APF) lattices, where electrons, depending on the electron-laser interaction phase, will alternate between opposing longitudinal and transverse focusing and defocusing forces. By incorporating fractional period drift sections that alter the synchronous phase between $\pm 60°$ off crest, electrons captured in the designed acceleration bucket experience half the peak gradient as average gradient while also experiencing strong confinement forces that enable long interaction lengths. We demonstrate APF accelerators with interaction lengths up to $708\mathrm{\mu }\mathrm{m}$ and energy gains up to $23.7\pm 1.07\mathrm{keV}$ FWHM, a 25% increase from starting energy, demonstrating the ability to achieve substantial energy gains with subrelativistic DLA.

We report results from the first radiative particle-in-cell simulations of strong Alfvénic turbulence in plasmas of moderate optical depth. The simulations are performed in a local 3D periodic box and self-consistently follow the evolution of radiation as it interacts with a turbulent electron-positron plasma via Compton scattering. We focus on the conditions expected in magnetized coronae of accreting black holes and obtain an emission spectrum consistent with the observed hard state of Cyg X-1. Most of the turbulence power is transferred directly to the photons via bulk Comptonization, shaping the peak of the emission around 100 keV. The rest is released into nonthermal particles, which generate the MeV spectral tail. The method presented here shows promising potential for ab initio modeling of various astrophysical sources and opens a window into a new regime of kinetic plasma turbulence.

The use of finite entanglement scaling with matrix product states (MPS) has become a crucial tool for studying one-dimensional critical lattice theories, especially those with emergent conformal symmetry. We argue that finite entanglement introduces a relevant deformation in the critical theory. As a result, the bipartite entanglement Hamiltonian defined from the MPS can be understood as a boundary conformal field theory with a physical and an entanglement boundary. We are able to exploit the symmetry properties of the MPS to engineer the physical conformal boundary condition. The entanglement boundary, on the other hand, is related to the concrete lattice model and remains invariant under this relevant perturbation. Using critical lattice models described by the Ising, Potts, and free compact boson conformal field theories, we illustrate the influence of the symmetry and the relevant deformation on the conformal boundaries in the entanglement spectrum.

Driven by the expected contribution of two-dimensional multiferroic systems with strong magnetoelectric coupling to the development of multifunctional nanodevices, here we propose, by means of first-principles calculations, vanadium-halide monolayers as a new class of spin-chirality-driven van der Waals multiferroics. The frustrated 120-deg magnetic structure in the triangular lattice induces a ferroelectric polarization perpendicular to the spin-spiral plane, whose sign is switched by a spin-chirality change. It follows that, in the presence of an applied electric field perpendicular to the monolayers, one magnetic chirality can be stabilized over the other, thereby allowing the long-sought electrical control of spin textures. Moreover, we demonstrate the remarkable role of spin-lattice coupling on magnetoelectricity, which adds to the expected contribution of spin-orbit interaction determined by an anion. Indeed, such compounds exhibit sizeable spin-driven structural distortions, thereby promoting the investigation of multifunctional spin-electric-lattice couplings.

Trade-off relations place fundamental limits on the operations that physical systems can perform. This Letter presents a trade-off relation that bounds the correlation function, which measures the relationship between a system’s current and future states, in Markov processes. The obtained bound, referred to as the thermodynamic correlation inequality, states that the change in the correlation function has an upper bound comprising the dynamical activity, a thermodynamic measure of the activity of a Markov process. Moreover, by applying the obtained relation to the linear response function, it is demonstrated that the effect of perturbation can be bounded from above by the dynamical activity.

We introduce and study the discrete-time version of the quantum East model, an interacting quantum spin chain inspired by simple kinetically constrained models of classical glasses. Previous work has established that its continuous-time counterpart displays a disorder-free localization transition signaled by the appearance of an exponentially large (in the volume) family of nonthermal, localized eigenstates. Here we combine analytical and numerical approaches to show that (i) the transition persists for discrete times, in fact, it is present for any finite value of the time step apart from a zero measure set; (ii) it is directly detected by following the nonequilibrium dynamics of the fully polarized state. Our findings imply that the transition is currently observable in state-of-the-art platforms for digital quantum simulation.

Quantum information scrambling is a unitary process that destroys local correlations and spreads information throughout the system, effectively hiding it in nonlocal degrees of freedom. In principle, unscrambling this information is possible with perfect knowledge of the unitary dynamics [B. Yoshida and A. Kitaev, arXiv:1710.03363.]. However, this Letter demonstrates that even without previous knowledge of the internal dynamics, information can be efficiently decoded from an unknown scrambler by monitoring the outgoing information of a local subsystem. We show that rapidly mixing but not fully chaotic scramblers can be decoded using Clifford decoders. The essential properties of a scrambling unitary can be efficiently recovered, even if the process is exponentially complex. Specifically, we establish that a unitary operator composed of $t$ non-Clifford gates admits a Clifford decoder up to $t\le n$.

Based on data samples collected with the BESIII detector at the BEPCII collider, the process $e^{+}{e}^{-}\to {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-}$ is studied at center-of-mass energies $\sqrt{s}=2.3960$, 2.6454, and 2.9000 GeV. Using a fully differential angular description of the final state particles, both the relative magnitude and phase information of the ${\mathrm{\Sigma }}^{+}$ electromagnetic form factors in the timelike region are extracted. The relative phase between the electric and magnetic form factors is determined to be $\sin \mathrm{\Delta }\mathrm{\Phi }=-0.67\pm 0.29(\mathrm{stat})\pm 0.18(\mathrm{syst})$ at $\sqrt{s}=2.3960\mathrm{GeV}$, $\mathrm{\Delta }\mathrm{\Phi }=55°\pm 19°(\mathrm{stat})\pm 14°(\mathrm{syst})$ at $\sqrt{s}=2.6454\mathrm{GeV}$, and $78°\pm 22°(\mathrm{stat})\pm 9°(\mathrm{syst})$ at $\sqrt{s}=2.9000\mathrm{GeV}$. For the first time, the phase of the hyperon electromagnetic form factors is explored in a wide range of four-momentum transfer. The evolution of the phase along with four-momentum transfer is an important input for understanding its asymptotic behavior and the dynamics of baryons.

Optical atomic clocks based on trapped ions suffer from systematic frequency shifts of the clock transition due to interaction with blackbody radiation from the environment. These shifts can be compensated if the blackbody radiation spectrum and the differential dynamic polarizability is known to a sufficient precision. Here, we present a new measurement scheme, based on quantum logic that allows a direct transfer of precision for polarizability measurements from one species to the other. This measurement circumvents the necessity of calibrating laser power below the percent level, which is the limitation for state-of-the-art polarizability measurements in trapped ions. Furthermore, the presented technique allows one to reference the polarizability transfer to hydrogenlike ions for which the polarizability can be calculated with high precision.

We predict novel topological phases with broken time-reversal symmetry supporting the coexistence of opposite chiral edge states, which are fundamentally different from the photonic spin-Hall, valley-Hall, and higher-order topological phases. We find a fine-grained categorization of Chern insulators, their band topologies characterized by identical Chern numbers are completely different. Furthermore, we prove that different topologies cause zeros in their Bloch wave function overlaps, which imprint the band gap closing and appear at the degenerate points of topological phase transition. The Bloch wave function overlaps predict the reflection and refraction at a topological time boundary, and the overlap zeros ensure the existence of vanishing revival amplitude at critical times even though different topologies before and after the time boundary have identical Chern numbers. Our findings create new opportunities for topological metamaterials, uncover the topological feature hidden in the time boundary effect as a probe of topology, and open a venue for the exploration of the rich physics originating from the long-range couplings.

Convective dissolution, one of the main mechanisms for geological storage of ${\mathrm{CO}}_2$, occurs when supercritical or gas ${\mathrm{CO}}_2$ dissolves partially into an aqueous solution, thus triggering downward convection of the denser ${\mathrm{CO}}_2$-enriched liquid. Chemical reaction in the liquid can greatly enhance the process. Here, experimental measurements of convective flow inside a cylinder filled with a sodium hydroxide (NaOH) solution show that the plume’s velocity can be increased tenfold as compared to a situation with no NaOH. This tremendous effect is predicted by a model with no adjusting parameters.

Electron thermal diffuse scattering is shown to be sensitive to subtle changes in atomic vibrations and shows promise in assessing lattice dynamics at nanometer resolution. Here, we demonstrate that machine-learned interatomic potentials (MLIPs) and path-integral molecular dynamics can accurately capture the potential energy landscape and lattice dynamics needed to describe electron thermal diffuse scattering. Using ${\mathrm{SrTiO}}_3$ as a test bed at cryogenic and room temperatures, we compare electron thermal diffuse scattering simulations using different approximations to incorporate thermal motion. Only when the simulations are based on quantum mechanically accurate MLIPs in combination with path-integral molecular dynamics that include nuclear quantum effects is there excellent agreement with experiments.

Chiral anomaly bulk states (CABSs) can be realized by choosing appropriate boundary conditions in a finite-size waveguide composed of two-dimensional Dirac semimetals, which have unidirectional and robust transport similar to that of valley edge states. CABSs use almost all available guiding space, which greatly improves the utilization of metamaterials. Here, free-boundary-induced CABSs in elastic twisted kagome metamaterials with $C_{3v}$ symmetry are experimentally confirmed. The robust valley-locked transport and complete valley state conversion are experimentally observed. Importantly, the sign of the group velocity near the $K$ and $K^{\prime }$ points can be reversed by suspending masses at the boundary to manipulate the onsite potential. Moreover, CABSs are demonstrated in nanoelectromechanical phononic crystals by constructing an impedance-mismatched hard boundary. These results open new possibilities for designing more compact, space-efficient, and robust elastic wave macro- and microfunctional devices.