Numerous theories beyond the standard model of particle physics propose the existence of ultralight hypothetical bosons, which are prominent dark-matter candidates. One of the most promising approaches to search for these bosons is through precision measurements. The basic principle is to measure energy shifts of standard-model particles induced by hypothetical bosons with ultrahigh energy resolution. Here we develop a sensitive magnetometer based on noble-gas nuclear magnetic resonance, achieving an energy resolution of $\sim {10}^{-23}\mathrm{eV}$. Using this magnetometer, we measure the energy shifts of nuclear spins induced by anomalous $Z^{\prime }$ boson-mediated spin-spin interactions. The null results set the most stringent constraints on anomalous neutron-neutron and neutron-proton spin couplings in the $Z^{\prime }$-boson mass ranges of 6.0–157.4 and $<129.6\mathrm{\mu }\mathrm{eV}$, respectively. Notably, our constraints surpass previous ones by up to 17 orders of magnitude in aforementioned mass ranges. Our experiments further set the most stringent constraints on neutron-proton spin couplings mediated by massless ${\gamma }^{\prime }$ paraphotons, surpassing previous constraints by at least 25 orders of magnitude. Our technique paves the way for intriguing future directions in the search for various anomalous spin-spin interactions, including those mediated by axions with projected sensitivity surpassing astrophysical limits.

The nonlocality arising in a multiparty network involving multiple independent sources radically differs from the standard multipartite Bell nonlocality involving a single source. The notion of the full network nonlocality (FNN) [A. Pozas-Kerstjens et al., Full network nonlocality, Phys. Rev. Lett. 128, 010403 (2022)] characterizes the quantum correlations that cannot be reproduced by a local-nonlocal model featuring one local source and the rest of nonlocal no-signaling sources. However, the demonstration of FNN was limited to bilocal and trilocal star-shaped network scenarios involving three or two dichotomic measurements for edge parties. In this Letter, we first demonstrate that a large class of prevailing network inequalities does not exhibit FNN. We then introduce an elegant set of arbitrary-party and unbounded-input network inequalities in star-shaped and linear-chain networks whose optimal quantum violation exhibits FNN, certifying that the nonlocality is genuinely distributed to the entire network. Contrasting to existing demonstrations of FNN that inevitably require fixed-input and four-output elegant joint measurements for the central party, our generalized inequalities are more experimentally friendly, requiring only two output measurements. Moreover, our derivation of optimal quantum violation is fully analytic and devoid of assuming the dimension of the quantum system, thereby showcasing its potential for device-independent self-testing.

Exact solutions for excited states in nonintegrable quantum Hamiltonians have revealed novel dynamical phenomena that can occur in quantum many-body systems. This work proposes a method to analytically construct a specific set of volume-law entangled zero-energy exact excited eigenstates in a large class of spin Hamiltonians. In particular, we show that all spin chains that satisfy a simple set of conditions host exact volume law entangled zero-energy eigenstates in the middle of their spectra. Examples of physically relevant spin chains of this type include the transverse-field Ising model, PXP model, spin-$S$ $XY$ model, and spin-$S$ Kitaev chain. Although these eigenstates are highly atypical in their structure, they are thermal with respect to local observables. Our framework also unifies many recent constructions of volume-law entangled eigenstates in the literature. Finally, we show that a similar construction also generalizes to spin models on graphs in arbitrary dimensions.

Long-range interactions are essential for large-scale quantum computation and quantum interconnections. Cavities provide a promising avenue to achieve long-range interaction by enhancing the coupling of remote qubits through shared cavity modes. In this Letter, we investigate a spin array coupled to a ring cavity supporting two counterpropagating modes, focusing on the system’s eigenstates and spin dynamics in the low-excitation regime. We show that, under specific spatial configurations, the spins naturally self-organize into two groups, within which exciton transport is confined. This spin-grouping mechanism preserves coherence between spins across the two groups, and is leveraged to deterministically transfer entangled states between remote spin pairs with additional dynamical addressing. We further propose feasible implementations using atomic qubits or solid-state platforms. Our scheme enables entangling remote spins within a cavity, highlighting potential applications in scalable quantum information processing.

Collective oscillations in dense neutrino gases (flavor waves) are notable for their instabilities that cause fast flavor conversion. We develop a quantum theory of interacting neutrinos and flavor wave quanta, which are analogous to plasmons but also carry flavor. The emission or absorption of such flavor plasmons $\psi$, or “flavomons,” changes the neutrino flavor. When an angular crossing occurs, the process ${\nu }_{\mu }\to {\nu }_e+\psi$ is more rapid than its inverse along the direction of the crossing, triggering stimulated $\psi$ emission and fast instability. Calculating the rate via Feynman diagrams matches the fast instability growth rate. Our novel $\nu$ and $\psi$ kinetic equations, corresponding to quasilinear theory, describe instability evolution without resolving the small scales of the flavomon wavelength, potentially overcoming the main challenge of fast flavor evolution.

We construct the first binary black hole solutions of Einstein-Maxwell theory in asymptotically anti–de Sitter space. The attractive force between the two black holes is balanced by the addition of a background electric field, sourced at the conformal boundary. There is a continuous family of bulk solutions for a given boundary profile and temperature, suggesting there is continuous nonuniqueness. We investigate the charges of the solutions and numerically verify that they satisfy a first law of black hole mechanics relation.

The convergence of scalar-tensor gravity to general relativity, or the departure from it, is described in a new analogy with heat dissipation in a viscous fluid. This new thermal picture is applied to cosmology, shedding light on whether gravity deviates from general relativity early on and approaches it later in the cosmic history.

We performed the longest numerical-relativity neutrino-radiation magnetohydrodynamics simulation for a binary neutron star merger that extends to $\approx 1.5\mathrm{s}$ after the merger. We consider the binary model that undergoes the prompt collapse to a black hole after the merger with asymmetric mass $1.25M_{\odot }$ and $1.65M_{\odot }$ and SFHo equation of state. We find the Poynting flux-driven collimated outflow as well as the gravitational wave emission, neutrino emission, dynamical mass ejection, and postmerger mass ejection facilitated by magnetorotational instability-driven turbulent viscosity in a single self-consistent binary neutron star merger simulation. A magnetosphere dominated by the aligned global magnetic field penetrating the black hole develops along the black-hole spin axis after the turbulence in the remnant disk is enhanced. A jet with the Poynting flux with isotropic-equivalent luminosity of $\sim {10}^{49}\mathrm{erg}/\mathrm{s}$ is launched, and the duration of the high luminosity is expected to be $O(1)\mathrm{s}$.

As analogues of compact objects, solitons have attracted significant attention. We reveal that cylindrical Q strings exhibit a dynamical instability to perturbations with wavelengths exceeding a threshold $\lambda >{\lambda }_c$. This instability can destroy the invariance in the cylindrical direction, as a generation mechanism for Q balls, similar to the formation of droplets. As the interface of Q strings approaches a thin wall, this long-wavelength instability degenerates into the Rayleigh-Plateau instability with a threshold related only to the geometric radius ${\lambda }_c=2\pi R$. Such results indicate that Q strings, like black strings, resemble low-viscosity fluids with surface tension.

We propose a numerical method to estimate one-point functions and the free-energy density of conformal field theories at finite temperature by solving the Kubo-Martin-Schwinger condition for the two-point functions of identical scalars. We apply the method for the critical $\mathrm{O}(N)$ model for $N=1$, 2, 3 in $3\le d\le 4$. We find agreement with known results from Monte Carlo simulations and previous results for the 3D Ising model, and we provide new predictions for $N=2$, 3.

To explain the baryon asymmetry in the early universe via leptogenesis, quantum corrections to new particles are commonly invoked to generate the necessary $CP$ asymmetry. We demonstrate, however, that a large $CP$ asymmetry can already arise from standard model leptons. The mechanism relies on resummation of soft leptons at finite temperatures. The $CP$ asymmetry, which is kinematically forbidden in vacuum, can be resonantly enhanced from thermally resummed leptons by seven orders of magnitude. Contrary to the resonance from exotic particles, we show that the resonant enhancement from soft leptons is protected by controlled widths under finite-temperature perturbation theory. We quantify such $CP$ asymmetries in leptogenesis with secluded flavor effects and comment on the significance and application. The mechanism exploits the maximal role of leptons themselves, featuring low-scale leptogenesis, minimal model buildings, and dark matter cogenesis.

Nanolasers operating at low power levels are strongly affected by intrinsic quantum noise, influencing both intensity fluctuations and laser coherence. Starting from semiclassical rate equations and making a simple hypothesis for the phase of the laser field, a simple stochastic model for the laser quantum noise is suggested. The model is shown to agree quantitatively with quantum master equations for microscopic lasers with a small number of emitters and with classical Langevin equations for macroscopic systems. In contrast, neither quantum master equations nor classical Langevin equations adequately address the mesoscopic regime. The stochastic approach is used to calculate the linewidth throughout the transition to lasing, where the linewidth changes from being dominated by the particlelike nature of photons below threshold to the wavelike nature above threshold, where it is strongly influenced by index fluctuations enhancing the linewidth.

We study the relaxation process of two driven colloidal suspensions in contact, to a joint steady state, similar to the process of thermalization. First, we study a single suspension, subjecting it to random driving forces via holographic optical tweezers, which agitate it to a higher effective temperature. Interestingly, the effective temperature of the suspension, defined by the Einstein relation, exhibits a nonmonotonic dependence on the driving frequency. Next, we follow the flux of particles between two such suspensions in diffusive contact, starting from a uniform density and relaxing to a state with zero net particle flux. At high driving frequencies, we show that the density distribution at steady state is determined by equating the ratio of the chemical potential to the effective temperature in both systems, reminiscent of the thermal equilibrium behavior.

We report a direct determination of the cubic dielectric spectra of a realistic polar molecule, glycerol, from molecular dynamic (MD) simulations. From the liquid state to the mildly supercooled regime, we observed the emergence and growth of a hump in the cubic modulus, traditionally associated with collective effects in the dynamics. Its evolution follows that of dynamical correlations probed by the four-point susceptibility and that of the activation energy of the relaxation time. In particular, its appearance at high temperature coincides with the onset of superactivation. We show that, for this system, the shape of cubic spectra is only weakly affected by dipolar cross-correlations. The good agreement with experimental observations, despite the difference in temperature range, demonstrates the relevance of this approach to help get an insight into the intricate effects probed by nonlinear dielectric spectroscopy.

Ultralight dark photons are compelling dark matter candidates, but their allowed kinetic mixing with the standard model photon is severely constrained by requiring that the dark photons do not collapse into a cosmic string network in the early Universe. Direct detection in minimal production scenarios for dark photon dark matter is strongly limited, if not entirely excluded; discovery of sub-meV dark photon dark matter would therefore point to a nonminimal dark sector. We describe a model that evades such constraints, capable of producing cold dark photons in any parameter space accessible to future direct detection experiments. The associated production dynamics yield additional signatures in cosmology and small-scale structure, allowing for possible positive identification of this particular class of production mechanisms.