The gravitational-wave signal GW250114 was observed by the two LIGO detectors with a network matched-filter signal-to-noise ratio of 80. The signal was emitted by the coalescence of two black holes with near-equal masses $m_1={33.6}_{-0.8}^{+1.2}{M}_{\odot }$ and $m_2={32.2}_{-1.3}^{+0.8}{M}_{\odot }$, and small spins ${\chi }_{1,2}\le 0.26$ (90% credibility) and negligible eccentricity $e\le 0.03$. Postmerger data excluding the peak region are consistent with the dominant quadrupolar $(\ell =|m|=2)$ mode of a Kerr black hole and its first overtone. We constrain the modes’ frequencies to $\pm 30\%$ of the Kerr spectrum, providing a test of the remnant’s Kerr nature. We also examine Hawking’s area law, also known as the second law of black hole mechanics, which states that the total area of the black hole event horizons cannot decrease with time. A range of analyses that exclude up to five of the strongest merger cycles confirm that the remnant area is larger than the sum of the initial areas to high credibility.

This Letter reports the first evidence of electroweak production of same-sign $W$ boson pairs where at least one of the $W$ bosons is longitudinally polarized and the most stringent constraint to date for the production of two longitudinally polarized same-sign $W$ bosons. The dataset used corresponds to an integrated luminosity of $140{\mathrm{fb}}^{-1}$ of proton-proton collisions at a center-of-mass energy of 13 TeV, collected with the ATLAS detector during run 2 of the Large Hadron Collider. The study is performed in final states including two same-sign leptons (electrons or muons), missing transverse momentum, and at least two jets with a large invariant mass and a large rapidity difference. Two independent fits are performed targeting the production of same-sign $W$ bosons with at least one, or two longitudinally polarized $W$ bosons. The observed (expected) significance of the production with at least one longitudinally polarized $W$ boson is 3.3 (4.0) standard deviations. An observed (expected) 95% confidence level upper limit of 0.45 (0.70) fb is reported on the fiducial production cross section of two longitudinally polarized same-sign $W$ bosons.

The natural van der Waals heterostructure $4H_b\text{−}{\text{TaS}}_2$ composed of alternating $1T$- and $1H\text{−}{\text{TaS}}_2$ layers serves as a platform for investigating the electronic correlations and layer-dependent properties of novel quantum materials. The temperature evolution of the conductivity spectra $\sigma (\omega )$ obtained through infrared spectroscopy elucidates the influence of band modifications associated with the charge-density-wave (CDW) superlattice on the $1T$ layer, resulting in a room-temperature energy gap, ${\mathrm{\Delta }}_{\mathrm{CDW}}\approx 0.35\mathrm{eV}$. Supported by density functional theory calculations, we attribute the behavior of interband transitions to the convergence of the layers, which amplifies the charge transfer from the $1T$ to the $1H$ layers, progressing as the temperature decreases. This phenomenon leads to an enhanced carrier density. The presence of an energy gap and the temperature-tunable charge transfer within the bulk of $4H_b\text{−}{\text{TaS}}_2$—driven by layer-dependent CDW states—contribute to a more comprehensive understanding of other complex compounds of transition-metal dichalcogenides.

Incoherent $J/\psi$ photoproduction in heavy ion ultraperipheral collisions (UPCs) provides a sensitive probe of localized, fluctuating gluonic structures within heavy nuclei. This Letter reports the first measurement of the photon-nucleon center-of-mass energy ($W_{\gamma \mathrm{N}}$) dependence of this process in PbPb UPCs at a nucleon-nucleon center-of-mass energy of 5.02 TeV, using $1.52{\mathrm{nb}}^{-1}$ of data recorded by the CMS experiment. The measurement covers a wide $W_{\gamma \mathrm{N}}$ range of $\approx 40–400\mathrm{GeV}$, probing gluons carrying a fraction $x$ of nucleon momentum down to an unexplored regime of $6.5\times {10}^{-5}$. Compared to baseline predictions neglecting nuclear effects, the measured cross sections exhibit significantly greater suppression at lower $x$. Additionally, the ratio of incoherent to coherent photoproduction is found to be constant across the probed $W_{\gamma \mathrm{N}}$ and $x$ range, disfavoring the establishment of the black disk limit. This Letter provides critical insights into the $x$-dependent evolution of fluctuating gluonic structures within nuclei and calls for further advancements in theoretical models incorporating nuclear shadowing and gluon saturation.

Excitons are bosonic quasiparticles with a variety of applications in optoelectronics, photosynthesis, and dissipationless informatics, and their lifetime can become sufficiently long to form a quantum condensate. While exciton condensation has been predicted to occur as a ground state of a solid, so-called an excitonic insulator, whose material realization has been elusive. Here we report the observation of direct photoemission signals from excitons in a ground state of a very recent excitonic insulator candidate ${\mathrm{Ta}}_2{\mathrm{Pd}}_3{\mathrm{Te}}_5$ below its metal-insulator transition temperature using orbital-selective angle-resolved photoemission spectroscopy. It is confirmed that the excitons have a lower energy than the valence band maximum to possibly drive the phase transition. This measurement further discloses the size and the unusual odd parity of the exciton wave function. The present finding opens an avenue toward applications of coherent excitons in solid systems and searching for exotic quantum phases of exciton condensates.

Despite exhibiting a similar $d_{x^2-y^2}$ band character to cuprates, infinite-layer nickelates host additional electron pockets that distinguish them from single-band cuprates. The elusive orbital origin of these electron pockets has led to competing theoretical scenarios. Here, using polarization-dependent and resonant angle-resolved photoemission spectroscopy, we determine the orbital character of the Fermi surfaces in ${\mathrm{NdNiO}}_2$. Our data reveal that the electronlike pocket arises predominantly from interstitial $s$ states, with negligible contributions from rare-earth $5d$ and $4f$ orbitals near the Fermi level. The observation of well-defined quantum-well states indicates a uniform distribution of these interstitial electrons throughout the film thickness. By comparing with electronic structure of ${\mathrm{LaNiO}}_2$, we find that the rare-earth element modulates the Ni-derived bands and hopping integrals through a chemical pressure effect. These findings clarify the role of rare-earth elements in shaping the low-energy electronic structure and establish the presence of electridelike interstitial $s$ states in a correlated oxide system, where electrons occupy lattice voids rather than atomic orbitals. The electridelike character offers new insight into the self-doping and superconductivity in infinite-layer nickelates.

Superradiance emerges from collective spontaneous emission in optically pumped gases, and is characterized by photon emission enhancements of up to $\frac{1}{4}{N}^2$ in an $N$ atom system. The gain mechanism derives from correlations developed within the decay medium rather than from stimulated emission as in lasing, so an analog of this process should be possible for fermionic final states. We introduce here the concept of superradiant neutrino emission from a radioactive Bose Einstein condensate, which can form the basis for a superradiant neutrino laser. A plausible experimental realization based on a condensate of electron-capture isotope ${}^{83}\mathrm{Rb}$ could exhibit effective radioactive decay rates accelerated from 86.2 days to minutes in viably sized rubidium condensates of ${10}^6$ atoms.

The strength-toughness trade-off in polymer glasses presents a fundamental challenge, as enhancing one property typically compromises the other. Moreover, efforts to enhance mechanical performance often lead to increased melt viscosity, which in turn hinders processability. Here, we demonstrate that incorporating single-chain nanoparticles (SCNPs) breaks this trilemma by simultaneously enhancing strength, toughness, and processability. Through a combined experimental and molecular dynamics simulation approach, we reveal that SCNPs with higher glass transition temperature than the matrix not only increase yield strength but also delay and homogenize crazing, leading to dramatically improved toughness in the glassy state. Importantly, the SCNPs reduce melt viscosity in the molten state, countering the conventional trend of viscosity increase in nanocomposites. This triple enhancement establishes a universal framework for designing high-performance polymer glasses that transcend traditional material property limitations.

Sea ice is a key component of Earth’s climate system, making its aging process an essential focus of current research. The age of sea ice is closely linked to its thermal and mechanical properties, which govern its interactions with the surrounding environment. In this study, we combine experimental techniques and modeling to explore the full dynamical process of mushy ice growth and spontaneous aging in saline water, within a natural convective flow system. We show that the aging of newly formed mushy ice in the present system, characterized by a gradual long-term reduction in porosity, is controlled by diffusion-driven desalination. Moreover, we observe that the system eventually transits into a dense freshwater ice layer adjacent to a well-mixed saline water region. The shape of the ice layer in this asymptotic state is well captured by numerical simulations of nonporous ice. Our findings improve the understanding of the complex physics governing phase changes in aqueous systems and provide a framework for studying sea ice aging in laboratory settings, with implications spanning diverse natural and industrial applications.

We present the first experimental evidence of stimulated Raman rescattering of a laser in plasma: The scattered light produced by the Raman instability is intense enough to scatter again through the same instability. Although never observed, rescattering processes have been studied theoretically and numerically for many years in the context of inertial confinement fusion, since the plasma waves they generate could bootstrap thermal electrons to high energies [B. J. Winjum et al., Phys. Rev. Lett. 110, 165001 (2013)], preheating the fuel and degrading ignition conditions. Our experimental results are obtained with a spatially smoothed laser beam consisting of many speckles, with an average intensity around ${10}^{14}\mathrm{W}/{\mathrm{cm}}^2$ and close to ${10}^{15}\mathrm{W}/{\mathrm{cm}}^2$ in the speckles, such as those usually used in direct-drive inertial confinement fusion. Kinetic and hydrodynamic simulations show good agreement with the observations.

Temporal evolution of Wigner functions representing fluctuation distribution of magnetization in ${\mathrm{Y}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}$ (YIG) at the moment of parametric oscillation onset has been investigated. Our newly developed time-resolved spectroscopy unmasks that highly distorted and stretched correlation of magnetization fluctuation leads the parametric oscillation, being consistent with numerical simulation incorporating nonlinear four-magnon scattering. The method offers a powerful tool for probing nonlinear dynamics in a variety of magnets.

The ability to quantify the directional flow of information is vital to understanding natural systems and designing engineered information-processing systems. A widely used measure to quantify this information flow is the transfer entropy. However, until now, this quantity could only be obtained in dynamical models using approximations that are typically uncontrolled. Here we introduce a computational algorithm called “transfer entropy-path weight sampling” (TE-PWS), which makes it possible, for the first time, to quantify the transfer entropy and its variants exactly for any stochastic model, including those with multiple hidden variables, nonlinearity, transient conditions, and feedback. By leveraging techniques from polymer and path sampling, TE-PWS efficiently computes the transfer entropy as a Monte Carlo average over signal trajectory space. We use our exact technique to demonstrate that commonly used approximate methods to compute transfer entropies incur large systematic errors and high computational costs. As an application, we use TE-PWS in linear and nonlinear systems to reveal how transfer entropy can overcome naive applications of the data processing inequality in the presence of feedback.

Breakthrough experiments have recently realized fractional Chern insulators (FCIs) in moiré materials. However, all states observed are Abelian; the possible existence of more exotic non-Abelian FCIs remains controversial both experimentally and theoretically. Here, we investigate the competition between charge density wave (CDW) order, gapless composite fermion liquid (CFL), and non-Abelian Moore-Read states at half filling of a moiré band. Although ground-state (quasi)degeneracies and spectral flow are not sufficient for distinguishing between charge order and Moore-Read states, we find evidence using entanglement spectroscopy that both these states of matter can be realized with Coulomb interactions. By further analyzing the graviton excitations of Moore-Read states, we unveil that the ground states exhibit a mixed behavior of Pfaffian and anti-Pfaffian, despite the weak breaking of particle-hole symmetry. In a double twisted bilayer graphene model, transitions between these phases can be driven by the coupling strength between the layers: at weak coupling there is a CFL phase and at strong coupling a CDW order emerges. Remarkably, however, there is compelling evidence for a non-Abelian Moore-Read FCI phase at intermediate coupling.

We study the hydrodynamics of a system of agents that optimize either their individual utility (self-interest) or the collective welfare (cooperation). When agents act selfishly, their interactions are nonreciprocal, driving the system out of equilibrium; by contrast, purely altruistic dynamics restore reciprocity and yield an equilibrium description. We investigate how mixtures of these two behaviors shape the macroscopic properties of the liquid of agents. For highly rational agents, we find that introducing a small fraction of altruists can suppress the suboptimal clustering induced by selfish dynamics. This phenomenon can be attributed to altruists localizing at interfaces and acting as effective surfactants, shedding a new light on earlier findings in fixed neighborhood-based models [Phys. Rev. Lett. 120, 208301 (2018)]. When agents are “boundedly rational,” we introduce a well-mixed approximation that reduces the two-population model to a single effective scalar field theory. This allows us to leverage state-of-the-art tools from active matter to analytically characterize how altruism modifies surface tension and nucleation dynamics.

Complexity is a hallmark of the human brain, emerging from the interaction of billions of neurons over time. Among various measures, the Hurst exponent ($H$) has been used to characterize temporal correlations in neuronal activity. Here, we introduce a method to estimate $H$ directly from binary spike train series and propose that the coefficient of variation (CV) of $H$, rather than $H$ itself, more accurately reflects neural complexity during organoid maturation. After validating the method on simulated data with embedded short- and long-range correlations, we applied it to cortical organoids derived from human-induced pluripotent stem cells, recorded via multielectrode arrays over 250 day. The analysis revealed a peak in complexity, as indicated by the CV of $H$, around the 100th day. At this stage, the organoids exhibited a wide repertoire of dynamic patterns, including both isolated spiking and highly synchronized network events. These results suggest that organoid activity undergoes a structured evolution in complexity and that CV of $H$ provides a robust metric to capture this transition. Our approach offers a scalable tool for quantifying neural complexity in the developing brain.

String breaking is a fundamental concept in gauge theories, describing the decay of a flux string connecting two charges through the production of particle–antiparticle pairs. This phenomenon is particularly important in particle physics, notably in quantum chromodynamics, and plays a crucial role in condensed matter physics. However, achieving a theoretical understanding of this nonperturbative effect is challenging, as conventional numerical approaches often fall short and require substantial computational resources. On the experimental side, studying these effects necessitates advanced setups, such as high-energy colliders, which makes direct observation difficult. Here, we report an experimental investigation of the string breaking mechanism in a one-dimensional U(1) lattice gauge theory using an optical lattice quantum simulator. By deterministically preparing initial states of varying lengths with fixed charges at each end, and adiabatically tuning the mass and string tension, we observed in situ microscopic confined phases that exhibit either string or broken-string states. Further analysis reveals that string breaking occurs under a resonance condition, leading to the creation of new particle–antiparticle pairs. These findings offer compelling evidence of string breaking and provide valuable insights into the intricate dynamics of lattice gauge theories. Our work underscores the potential of optical lattices as controllable quantum simulators, enabling the exploration of complex gauge theories and their associated phenomena.

Gravitational waves from merging binary black holes present exciting opportunities for understanding fundamental aspects of gravity, including nonlinearities in the strong-field regime. One challenge in studying and interpreting the dynamics of binary black hole collisions is the intrinsically geometrical nature of spacetime, which in many ways is unlike that of other classical field theories. By exactly recasting Einstein’s equations into a set of coupled nonlinear Maxwell equations closely resembling classical electrodynamics, we visualize the intricate dynamics of gravitational electric and magnetic fields during the inspiral, merger, and ringdown of a binary black hole collision.

A new measurement of the magnetic anomaly $a_{\mu }$ of the positive muon is presented based on data taken from 2020 to 2023 by the Muon $g-2$ Experiment at Fermi National Accelerator Laboratory (FNAL). This dataset contains over 2.5 times the total statistics of our previous results. From the ratio of the precession frequencies for muons and protons in our storage ring magnetic field, together with precisely known ratios of fundamental constants, we determine $a_{\mu }=1165920710(162)\times {10}^{-12}$ (139 ppb) for the new datasets, and $a_{\mu }=1165920705(148)\times {10}^{-12}$ (127 ppb) when combined with our previous results. The new experimental world average, dominated by the measurements at FNAL, is $a_{\mu }(\exp )=1165920715(145)\times {10}^{-12}$ (124 ppb). The measurements at FNAL have improved the precision on the world average by over a factor of 4.

Understanding many body systems is a key challenge in physics. Single atom resolved imaging techniques have unlocked access to microscopic correlations in ultracold quantum gases. However they cannot be used when the relevant length scales are obscured by the resolution of the detection technique. We present a matter wave magnification scheme, based on evolutions in optical potentials, tailored to magnify the wave function of atoms, such that all length scales can be resolved. To showcase this method, we image atoms in the strongly interacting regime, establishing a new way to characterize correlated systems.

Short-distance constraints from the operator product expansion in QCD play an important role in the evaluation of the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon. Holographic QCD has been shown to naturally incorporate the Melnikov-Vainshtein constraint on the longitudinal amplitude following from the triangle anomaly in the asymmetric limit, where one photon virtuality remains small compared to the others. This is saturated by an infinite tower of axial vector mesons, and their numerical contribution to the muon $g-2$ in AdS/QCD models agrees rather well with a recent dispersive analysis. However, in AdS/QCD, the longitudinal short-distance constraint where all virtualities are large turns out to be matched only at the level of 81%. In this Letter we show that tensor mesons, whose contribution to the muon $g-2$ has recently been found to be underestimated, can fill this gap because in holographic QCD their infinite tower of excited mesons only contributes to the symmetric longitudinal short-distance constraint. Numerically, they give rise to a sizeable positive contribution from the low-energy region below 1.5 GeV, a small one from the mixed region, and a negligible one from the high-energy region, which could explain the remaining gap between the most recent dispersive and lattice results for the complete hadronic light-by-light contribution.