We derive basic scaling equations for relativistic magnetic reconnection in the general case of asymmetric inflow conditions and obtain predictions for the outflow Lorentz factor and the reconnection rate. Kinetic particle-in-cell simulations show that the outflow speeds as well as the nonthermal spectral index are constrained by the inflowing plasma with the weaker magnetic energy per particle, in agreement with the scaling predictions. These results are significant for understanding nonthermal emission from reconnection in magnetically dominated astrophysical systems, many of which may be asymmetric in nature. The results provide a quantitative approach for including asymmetry on reconnection in the relativistic regime.

Strong coupling between resonant states is usually achieved by modulating intrinsic parameters of optical systems, e.g., the refractive index of constituent materials or structural geometries. Externally introduced chiral enantiomers may couple resonances, but the extremely weak chirality of natural enantiomers largely prevents the system from reaching strong coupling regimes. Whether weak chirality could induce strong coupling between resonant states remains an open question. Here, we realize strong coupling between quasibound states in the continuum of a high-$Q$ metasurface, assisted with externally introduced enantiomers of weak chirality. We establish a chirality-involved Hamiltonian to quantitatively describe the correlation between the coupling strength and the chirality of such systems, which provides an insightful recipe for enhancing the coupling of resonant states further in the presence of quite weak chirality. Consequently, high-sensitivity chiral sensing is demonstrated, in which the circular dichroism signal is enhanced 3 orders higher than the case without strong coupling. Our findings present a distinct strategy for manipulating optical coupling between resonances, revealing opportunities in chiral sensing, topological photonics, and quantum optics.

We study many-body localization (MBL) for interacting one-dimensional lattice fermions in random (Anderson) and quasiperiodic (Aubry-Andre) models, focusing on the role of interaction range. We obtain the MBL quantum phase diagrams by calculating the experimentally relevant inverse participation ratio (IPR) at half-filling using exact diagonalization methods and extrapolating to the infinite system size. For short-range interactions, our results produce in the phase diagram a qualitative symmetry between weak and strong interaction limits. For long-range interactions, no such symmetry exists as the strongly interacting system is always many-body localized, independent of the effective disorder strength, and the system is analogous to a pinned Wigner crystal. We obtain various scaling exponents for the IPR, suggesting conditions for different MBL regimes arising from interaction effects.

The current response to an electromagnetic field in a Weyl or Dirac semimetal becomes nonlocal due to the chiral anomaly activated by an applied static magnetic field. The nonlocality develops under the conditions of the normal skin effect and is related to the valley charge imbalance generated by the joint effect of the electric field of the impinging wave and the static magnetic field. We elucidate the signatures of this nonlocality in the transmission of electromagnetic waves. The signatures include enhancement of the transmission amplitude and its specific dependence on the wave’s frequency and the static magnetic field strength.

It has recently been reported that bacteria, such as Escherichia coli Bhattacharjee and Datta, Nat. Commun. 10, 2075 (2019). and Pseudomonas putida Alirezaeizanjani et al., Sci. Adv. 6, eaaz6153 (2020)., perform distinct modes of motion when placed in porous media as compared to dilute regions or free space. This has led us to suggest an efficient strategy for active particles in a disordered environment: reorientations are suppressed in locally dilute regions and intensified in locally dense ones. Thereby the local geometry determines the optimal path of the active agent and substantially accelerates the dynamics for up to 2 orders of magnitude. We observe a nonmonotonic behavior of the diffusion coefficient in dependence on the tumbling rate and identify a localization transition, either by increasing the density of obstacles or by decreasing the reorientation rate.

The surface bond nature of face centered cubic metals has been controversial between hardening and softening theoretically because of the lack of precise measurement. Here, we precisely measured the size dependence of Young’s modulus of gold [111] nanocontacts with a clean surface by our in situ TEM-frequency modulation force sensing method in ultrahigh vacuum at room temperature. Young’s modulus gradually decreased from ca. 80 to 30 GPa, as the nanocontact width decreased below 2 nm, which could be explained by surface softening; Young’s modulus of the outermost atomic layer was estimated to be approximately 22 GPa, while that of the other part was almost the same with the bulk.

The singly Cabibbo-suppressed decay ${\mathrm{\Lambda }}_c^{+}\to n{\pi }^{+}$ is observed for the first time with a statistical significance of $7.3\sigma$ by using $3.9{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected at center-of-mass energies between 4.612 and 4.699 GeV with the BESIII detector at BEPCII. The branching fraction of ${\mathrm{\Lambda }}_c^{+}\to n{\pi }^{+}$ is measured to be $(6.6\pm 1.2_{\mathrm{stat}}\pm 0.4_{\mathrm{syst}})\times {10}^{-4}$. By taking the upper limit of branching fractions of ${\mathrm{\Lambda }}_c^{+}\to p{\pi }^0$ from the Belle experiment, the ratio of branching fractions between ${\mathrm{\Lambda }}_c^{+}\to n{\pi }^{+}$ and ${\mathrm{\Lambda }}_c^{+}\to p{\pi }^0$ is calculated to be larger than 7.2 at the 90% confidence level, which disagrees with most predictions of the available phenomenological models. In addition, the branching fractions of the Cabibbo-favored decays ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{\pi }^{+}$ and ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^0{\pi }^{+}$ are measured to be $(1.31\pm 0.08_{\mathrm{stat}}\pm 0.05_{\mathrm{syst}})\times {10}^{-2}$ and $(1.22\pm 0.08_{\mathrm{stat}}\pm 0.07_{\mathrm{syst}})\times {10}^{-2}$, respectively, which are consistent with previous results.

We investigate the limits of thermometry using quantum probes at thermal equilibrium within the Bayesian approach. We consider the possibility of engineering interactions between the probes in order to enhance their sensitivity, as well as feedback during the measurement process, i.e., adaptive protocols. On the one hand, we obtain an ultimate bound on thermometry precision in the Bayesian setting, valid for arbitrary interactions and measurement schemes, which lower bounds the error with a quadratic (Heisenberg-like) scaling with the number of probes. We develop a simple adaptive strategy that can saturate this limit. On the other hand, we derive a no-go theorem for nonadaptive protocols that does not allow for better than linear (shot-noise-like) scaling even if one has unlimited control over the probes, namely, access to arbitrary many-body interactions.

The driven-dissipative Dicke model features normal, superradiant, and lasing steady states that may be regular or chaotic. We report quantum signatures of chaos in a quench protocol from the lasing states. Within the framework of a classical mean-field perspective, once quenched, the system relaxes either to the normal or to the superradiant state. Quench from chaos, unlike quench from a regular lasing state, exhibits erratic dependence on control parameters. In the quantum domain, this sensitivity implies an effect that is similar to universal conductance fluctuations.

We investigate the structure of many-body wave functions of 1D quantum circuits with local measurements employing the participation entropies. The leading term in system size dependence of participation entropy indicates a model-dependent multifractal scaling of the wave functions at any nonzero measurement rate. The subleading term contains universal information about measurement-induced phase transitions and plays the role of an order parameter, being constant nonzero in the error-correcting phase and vanishing in the quantum Zeno phase. We provide robust numerical evidence investigating a variety of quantum many-body systems and provide an analytical interpretation of this behavior expressing the participation entropy in terms of partition functions of classical statistical models in 2D.

The thermodynamic uncertainty relation expresses a seemingly universal trade-off between the cost for driving an autonomous system and precision in any output observable. It has so far been proven for discrete systems and for overdamped Brownian motion. Its validity for the more general class of underdamped Brownian motion, where inertia is relevant, was conjectured based on numerical evidence. We now disprove this conjecture by constructing a counterexample. Its design is inspired by a classical pendulum clock, which uses an escapement to couple the motion of an oscillator to another degree of freedom (a “hand”) driven by an external force. Considering a thermodynamically consistent, discrete model for an escapement mechanism, we first show that the oscillations of an underdamped harmonic oscillator in thermal equilibrium are sufficient to break the thermodynamic uncertainty relation. We then show that this is also the case in simulations of a fully continuous underdamped system with a potential landscape that mimics an escaped pendulum.

We consider the effective field theory of gravity around black holes, and show that the coefficients of the dimension-8 operators are tightly constrained by causality considerations. Those constraints are consistent with—but tighter than—previously derived causality and positivity bounds and imply that the effects of one of the dimension-8 operators by itself cannot be observable while remaining consistent with causality. We then establish in which regime one can expect the generic dimension-8 and lower order operators to be potentially observable while preserving causality, providing a theoretical prior for future observations. We highlight the importance of “infrared causality” and show that the requirement of “asymptotic causality” or net (sub)luminality would fail to properly diagnose violations of causality.

The relative abundance of cosmic ray nickel nuclei with respect to iron is by far larger than for all other transiron elements; therefore it provides a favorable opportunity for a low background measurement of its spectrum. Since nickel, as well as iron, is one of the most stable nuclei, the nickel energy spectrum and its relative abundance with respect to iron provide important information to estimate the abundances at the cosmic ray source and to model the Galactic propagation of heavy nuclei. However, only a few direct measurements of cosmic-ray nickel at energy larger than $\sim 3\mathrm{GeV}/\mathit{n}$ are available at present in the literature, and they are affected by strong limitations in both energy reach and statistics. In this Letter, we present a measurement of the differential energy spectrum of nickel in the energy range from $8.8$ to $240\mathrm{GeV}/\mathit{n}$, carried out with unprecedented precision by the Calorimetric Electron Telescope (CALET) in operation on the International Space Station since 2015. The CALET instrument can identify individual nuclear species via a measurement of their electric charge with a dynamic range extending far beyond iron (up to atomic number $Z=40$). The particle’s energy is measured by a homogeneous calorimeter (1.2 proton interaction lengths, 27 radiation lengths) preceded by a thin imaging section (3 radiation lengths) providing tracking and energy sampling. This Letter follows our previous measurement of the iron spectrum [O. Adriani et al. (CALET Collaboration), Phys. Rev. Lett. 126, 241101 (2021).], and it extends our investigation on the energy dependence of the spectral index of heavy elements. It reports the analysis of nickel data collected from November 2015 to May 2021 and a detailed assessment of the systematic uncertainties. In the region from $20$ to $240\mathrm{GeV}/\mathit{n}$ our present data are compatible within the errors with a single power law with spectral index $-2.51\pm 0.07$.

Axionlike particles (ALPs) are predicted in many extensions of the standard model, and their masses can naturally be well below the electroweak scale. In the presence of couplings to electroweak bosons, these particles could be emitted in flavor-changing $B$ meson decays. We report herein a search for an ALP, $a$, in the reaction $B^{\pm }\to K^{\pm }a$, $a\to \gamma \gamma$ using data collected by the BABAR experiment at SLAC. No significant signal is observed, and 90% confidence level upper limits on the ALP coupling to electroweak bosons are derived as a function of ALP mass, improving current constraints by several orders of magnitude in the range $0.175\mathrm{GeV}<m_a<4.78\mathrm{GeV}$.

Given current discrepancy in muon $g-2$ and future dedicated efforts to measure muon electric dipole moment (EDM) $d_{\mu }$, we assess the indirect constraints imposed on $d_{\mu }$ by the EDM measurements performed with heavy atoms and molecules. We notice that the dominant muon EDM effect arises via the muon-loop induced “light-by-light” $CP$-odd amplitude $\propto \mathbf{B}{\mathbf{E}}^3$, and in the vicinity of a large nucleus the corresponding parameter of expansion can be significant, $e{E}_{\mathrm{nucl}}/m_{\mu }^2\sim 0.04$. We compute the $d_{\mu }$-induced Schiff moment of the ${}^{199}\mathrm{Hg}$ nucleus, and the linear combination of $d_e$ and semileptonic $C_S$ operator (dominant in this case) that determine the $CP$-odd effects in the ThO molecule. The results, $d_{\mu }({}^{199}\mathrm{Hg})<6\times {10}^{-20}e\mathrm{cm}$ and $d_{\mu }(\mathrm{ThO})<2\times {10}^{-20}e\mathrm{cm}$, constitute approximately threefold and ninefold improvements over the limits on $d_{\mu }$ extracted from the Brookhaven National Laboratory muon beam experiment.

We report the first measurement of the parity-violating elastic electron scattering asymmetry on ${}^{27}\mathrm{Al}$. The ${}^{27}\mathrm{Al}$ elastic asymmetry is $A_{\mathrm{PV}}=2.16\pm 0.11(\mathrm{stat})\pm 0.16(\text{syst})\mathrm{ppm}$, and was measured at $⟨Q^2⟩=0.02357\pm 0.00010{\mathrm{GeV}}^2$, $⟨{\theta }_{\mathrm{lab}}⟩=7.61°\pm 0.02°$, and $⟨E_{\mathrm{lab}}⟩=1.157\mathrm{GeV}$ with the ${\mathrm{Q}}_{\mathrm{weak}}$ apparatus at Jefferson Lab. Predictions using a simple Born approximation as well as more sophisticated distorted-wave calculations are in good agreement with this result. From this asymmetry the ${}^{27}\mathrm{Al}$ neutron radius $R_n=2.89\pm 0.12\mathrm{fm}$ was determined using a many-models correlation technique. The corresponding neutron skin thickness $R_n-R_p=-0.04\pm 0.12\mathrm{fm}$ is small, as expected for a light nucleus with a neutron excess of only 1. This result thus serves as a successful benchmark for electroweak determinations of neutron radii on heavier nuclei. A tree-level approach was used to extract the ${}^{27}\mathrm{Al}$ weak radius $R_w=3.00\pm 0.15\mathrm{fm}$, and the weak skin thickness $R_{\mathrm{wk}}-R_{\mathrm{ch}}=-0.04\pm 0.15\mathrm{fm}$. The weak form factor at this $Q^2$ is $F_{\mathrm{wk}}=0.39\pm 0.04$.

Differential cross sections for Compton scattering from the proton have been measured at scattering angles of 55°, 90°, and 125° in the laboratory frame using quasimonoenergetic linearly (circularly) polarized photon beams with a weighted mean energy value of 83.4 MeV (81.3 MeV). These measurements were performed at the High Intensity Gamma-Ray Source facility at the Triangle Universities Nuclear Laboratory. The results are compared to previous measurements and are interpreted in the chiral effective field theory framework to extract the electromagnetic dipole polarizabilities of the proton, which gives ${\alpha }_{E1}^p=13.8\pm 1.2_{\mathrm{stat}}\pm 0.1_{\mathrm{BSR}}\pm 0.3_{\mathrm{theo}},{\beta }_{M1}^p=0.2\mp 1.2_{\mathrm{stat}}\pm 0.1_{\mathrm{BSR}}\mp 0.3_{\mathrm{theo}}$ in units of ${10}^{-4}{\mathrm{fm}}^3$.