We show that heavy primordial black holes may originate from much lighter ones if the latter are strongly clustered at the time of their formation. While this population is subject to the usual constraints from late-time universe observations, its relation to the initial conditions is different from the standard scenario and provides a new mechanism to generate massive primordial black holes even in the absence of efficient accretion, opening new scenarios, e.g., for the generation of supermassive black holes.

We consider minimal type-A higher-spin (HS) gravity in four dimensions, at tree level. We propose new diagrammatic rules for this theory, involving both Fronsdal fields and Didenko-Vasiliev particles—linearized versions of HS gravity’s “BPS black hole.” The vertices include a standard minimal coupling between particle and gauge field, the Sleight-Taronna cubic vertex for HS fields, and a recently introduced vertex coupling two HS fields to a Didenko-Vasiliev particle. We show how these ingredients can be combined to reproduce all $n$-point functions of the theory’s holographic dual—the free $O(N)$ vector model. Our diagrammatic rules interpolate between the usual diagrammatic rules of field theory and those of string theory. Our construction can be viewed as a bulk realization of HS algebra.

The phonon magnetochiral effect (MChE) is the nonreciprocal acoustic and thermal transports of phonons caused by the simultaneous breaking of the mirror and time-reversal symmetries. So far, the phonon MChE has been observed only in a ferrimagnetic insulator ${\mathrm{Cu}}_2{\mathrm{OSeO}}_3$, where the nonreciprocal response disappears above the Curie temperature of 58 K. Here, we study the nonreciprocal acoustic properties of a room-temperature ferromagnet ${\mathrm{Co}}_9{\mathrm{Zn}}_9{\mathrm{Mn}}_2$ for unveiling the phonon MChE close to room temperature. Surprisingly, the nonreciprocity in this metallic compound is enhanced at higher temperatures and observed up to 250 K. This clear contrast between insulating ${\mathrm{Cu}}_2{\mathrm{OSeO}}_3$ and metallic ${\mathrm{Co}}_9{\mathrm{Zn}}_9{\mathrm{Mn}}_2$ suggests that metallic magnets have a mechanism to enhance the nonreciprocity at higher temperatures. From the ultrasound and microwave-spectroscopy experiments, we conclude that the magnitude of the phonon MChE of ${\mathrm{Co}}_9{\mathrm{Zn}}_9{\mathrm{Mn}}_2$ mostly depends on the Gilbert damping, which increases at low temperatures and hinders the magnon-phonon hybridization. Our results suggest that the phonon nonreciprocity could be further enhanced by engineering the magnon band of materials.

We address the sliding thermodynamics of van der Waals-bonded bilayers by continuum electromechanics. We attribute the robustness of the ferroelectricity recently observed in h-BN and ${\mathrm{WTe}}_2$ bilayers to large in-plane stiffness of the monolayers. We compute the electric susceptibility and specific heat in a mean-field self-consistent phonon approximation. We compare critical temperatures and electric switching fields with the observed values.

Usually, sufficient supercooling of a liquid is employed to bypass the free energy barrier and speed up crystallization. However, lowering the temperature $T$ induces new issues competing with the crystallization, e.g., slow particle motion, geometric frustration, and the glass formation, which complicates our understanding of crystal growth. Here we systematically study the low-temperature nucleation kinetics discriminated by the maximum nucleation rate temperature $T_d$ and the glass transition temperature $T_g$. At $T_d$, the ratio of the precursor and geometrically frustrated particles reaches the maximum. When $T_g<T<T_d$, nucleation kinetics is characterized by the subdiffusive slow particle motion, the high degrees of geometric frustration, and the saturation of precursors. In this regime, nucleation can proceed through the diffusionless-like ordering of precursors. Near $T_g$, there is a crossover regime, where geometrically frustrated particles percolate and the glass formation strongly slows down the nucleation. When $T<T_g$, diffusionless nucleation is obstructed due to the weak vibrational motion and the mechanical stability of the glassy state.

We report results on the instantaneous drag force on plates that are accelerated in a direction normal to the plate surface, which show that this force scales with the square root of the acceleration. This is associated with the generation and advection of vorticity at the plate surface. A new scaling law is presented for the drag force on accelerating plates, based on the history force for unsteady flow. This scaling avoids previous inconsistencies in using added mass forces in the description of forces on accelerating plates.

We introduce a family of entanglement witnesses for continuous variable systems, which rely on the sole assumption that their dynamics is that of coupled harmonic oscillators at the time of the test. Entanglement is inferred from the Tsirelson nonclassicality test on one of the normal modes, without any knowledge about the state of the other mode. In each round, the protocol requires measuring only the sign of one coordinate (e.g., position) at one among several times. This dynamic-based entanglement witness is more akin to a Bell inequality than to an uncertainty relation: in particular, it does not admit false positives from classical theory. Our criterion detects non-Gaussian states, some of which are missed by other criteria.

Fisher information is a key notion in the whole field of quantum metrology. It allows for a direct quantification of the maximal achievable precision of the estimation of the parameters encoded in quantum states using the most general quantum measurement. It fails, however, to quantify the robustness of quantum estimation schemes against measurement imperfections, which are always present in any practical implementations. Here, we introduce a new concept of Fisher information measurement noise susceptibility that quantifies the potential loss of Fisher information due to small measurement disturbance. We derive an explicit formula for the quantity, and demonstrate its usefulness in the analysis of paradigmatic quantum estimation schemes, including interferometry and superresolution optical imaging.

Nuclear burning plays a key role in a wide range of astrophysical stellar transients, including thermonuclear, pair instability, and core collapse supernovae, as well as kilonovae and collapsars. Turbulence is now understood to also play a key role in these astrophysical transients. Here, we demonstrate that turbulent nuclear burning may lead to large enhancements above the uniform background burning rate, since turbulent dissipation gives rise to temperature fluctuations, and in general the nuclear burning rates are highly sensitive to temperature. We derive results for the turbulent enhancement of the nuclear burning rate under the influence of strong turbulence in the distributed burning regime in homogeneous isotropic turbulence, using probability distribution function methods. We demonstrate that the turbulent enhancement obeys a universal scaling law in the limit of weak turbulence. We further demonstrate that, for a wide range of key nuclear reactions, such as ${\mathrm{C}}^{12}({\mathrm{O}}^{16},\alpha ){\mathrm{Mg}}^{24}$ and $3\text{−}\alpha$, even relatively modest temperature fluctuations, of the order of 10%, can lead to enhancements of 1–3 orders of magnitude in the turbulent nuclear burning rate. We verify the predicted turbulent enhancement directly against numerical simulations, and find very good agreement. We also present an estimation for the onset of turbulent detonation initiation, and discuss implications of our results for stellar transients.

We obtain a closed formula for the Kähler potential of a broad class of four-dimensional Lorentzian or Euclidean conformal “Kähler” geometries, including the Plebański-Demiański class and various gravitational instantons such as Fubini-Study and Chen-Teo. We show that the Kähler potentials of Schwarzschild and Kerr are related by a Newman-Janis shift. Our method also shows that a class of supergravity black holes, including the Kerr-Sen spacetime, is Hermitian. We finally show that the integrability conditions of complex structures lead naturally to the Weyl double copy.

Identifying the flavor of reconstructed hadronic jets is critical for precision phenomenology and the search for new physics at collider experiments, as it allows one to pinpoint specific scattering processes and reject backgrounds. Jet measurements at the LHC are almost universally performed using the anti-$k_T$ algorithm; however, no approach exists to define the jet flavor for this algorithm that is infrared and collinear safe. We propose a new approach, a flavor-dressing algorithm, that is infrared and collinear safe in perturbation theory and can be combined with any definition of a jet. We test the algorithm in an $e^{+}{e}^{-}$ environment and consider the $pp\to Z+b\text{−}\text{jet}$ process as a practical application at hadron colliders.

Non-Hermitian systems generically have complex energies, which may host topological structures, such as links or knots. While there has been great progress in experimentally engineering non-Hermitian models in quantum simulators, it remains a significant challenge to experimentally probe complex energies in these systems, thereby making it difficult to directly diagnose complex-energy topology. Here, we experimentally realize a two-band non-Hermitian model with a single trapped ion whose complex eigenenergies exhibit the unlink, unknot, or Hopf link topological structures. Based on non-Hermitian absorption spectroscopy, we couple one system level to an auxiliary level through a laser beam and then experimentally measure the population of the ion on the auxiliary level after a long period of time. Complex eigenenergies are then extracted, illustrating the unlink, unknot, or Hopf link topological structure. Our work demonstrates that complex energies can be experimentally measured in quantum simulators via non-Hermitian absorption spectroscopy, thereby opening the door for exploring various complex-energy properties in non-Hermitian quantum systems, such as trapped ions, cold atoms, superconducting circuits, or solid-state spin systems.

Following the removal of axial confinement the momentum distribution of a Tonks-Girardeau gas approaches that of a system of noninteracting spinless fermions in the initial harmonic trap. This phenomenon, called dynamical fermionization, has been experimentally confirmed in the case of the Lieb-Liniger model and theoretically predicted in the case of multicomponent systems at zero temperature. We prove analytically that for all spinor gases with strong repulsive contact interactions at finite temperature the momentum distribution after release from the trap asymptotically approaches that of a system of spinless fermions at the same temperature but with a renormalized chemical potential which depends on the number of components of the spinor system. In the case of the Gaudin-Yang model we check numerically our analytical predictions using the results obtained from a nonequilibrium generalization of Lenard’s formula describing the time evolution of the field-field correlators.

The collective absorption and emission of light by an ensemble of atoms is at the heart of many fundamental quantum optical effects and the basis for numerous applications. However, beyond weak excitation, both experiment and theory become increasingly challenging. Here, we explore the regimes from weak excitation to inversion with ensembles of up to 1000 atoms that are trapped and optically interfaced using the evanescent field surrounding an optical nanofiber. We realize full inversion, with about 80% of the atoms being excited, and study their subsequent radiative decay into the guided modes. The data are very well-described by a simple model that assumes a cascaded interaction of the guided light with the atoms. Our results contribute to the fundamental understanding of the collective interaction of light and matter and are relevant for applications ranging from quantum memories to sources of nonclassical light to optical frequency standards.

We demonstrate the formation of a condensate in a dark state of momentum states, in a pumped and shaken cavity-BEC system. The system consists of an ultracold quantum gas in a high-finesse cavity, which is pumped transversely by a phase-modulated laser. This phase-modulated pumping couples the atomic ground state to a superposition of excited momentum states, which decouples from the cavity field. We demonstrate how to achieve condensation in this state, supported by time-of-flight and photon emission measurements. With this, we show that the dark state concept provides a general approach to efficiently prepare complex many-body states in an open quantum system.

Using discrete element method simulations, we show that the settling of frictional cohesive grains under ramped-pressure compression exhibits strong history dependence and slow dynamics that are not present for grains that lack either cohesion or friction. Systems prepared by beginning with a dilute state and then ramping the pressure to a small positive value $P_{\text{final}}$ over a time ${\tau }_{\mathrm{ramp}}$ settle at packing fractions given by an inverse-logarithmic rate law, ${\varphi }_{\text{settled}}({\tau }_{\mathrm{ramp}})={\varphi }_{\text{settled}}(\infty )+A/[1+B\ln (1+{\tau }_{\mathrm{ramp}}/{\tau }_{\mathrm{slow}})]$. This law is analogous to the one obtained from classical tapping experiments on noncohesive grains, but crucially different in that ${\tau }_{\mathrm{slow}}$ is set by the slow dynamics of structural void stabilization rather than the faster dynamics of bulk densification. We formulate a kinetic free-void-volume theory that predicts this ${\varphi }_{\text{settled}}({\tau }_{\mathrm{ramp}})$, with ${\varphi }_{\text{settled}}(\infty )={\varphi }_{\mathrm{ALP}}$ and $A={\varphi }_{\text{settled}}(0)-{\varphi }_{\mathrm{ALP}}$, where ${\varphi }_{\mathrm{ALP}}\equiv .135$ is the “adhesive loose packing” fraction found by Liu et al. [Equation of state for random sphere packings with arbitrary adhesion and friction, Soft Matter 13, 421 (2017)].

Recent experiments have shown an indication of a hydrodynamic magnon behavior in ultrapure ferromagnetic insulators; however, its direct observation is still lacking. Here, we derive a set of coupled hydrodynamic equations and study the thermal and spin conductivities for such a magnon fluid. We reveal the drastic breakdown of the magnonic Wiedemann-Franz law as a hallmark of the hydrodynamics regime, which will become key evidence for the experimental realization of an emergent hydrodynamic magnon behavior. Therefore, our results pave the way toward the direct observation of magnon fluids.