The Heisenberg limit to laser coherence $\mathfrak{C}$—the number of photons in the maximally populated mode of the laser beam—is the fourth power of the number of excitations inside the laser. We generalize the previous proof of this upper bound scaling by dropping the requirement that the beam photon statistics be Poissonian (i.e., Mandel’s $Q=0$). We then show that the relation between $\mathfrak{C}$ and sub-Poissonianity ($Q<0$) is win-win, not a tradeoff. For both regular (non-Markovian) pumping with semiunitary gain (which allows $Q\to -1$), and random (Markovian) pumping with optimized gain, $\mathfrak{C}$ is maximized when $Q$ is minimized.

Pairing of composite fermions provides a possible mechanism for fractional quantum Hall effect at even denominator fractions and is believed to serve as a platform for realizing quasiparticles with non-Abelian braiding statistics. We present results from fixed-phase diffusion Monte Carlo calculations which predict that substantial Landau level mixing can induce a pairing of composite fermions at filling factors $\nu =1/2$ and $\nu =1/4$ in the $l=-3$ relative angular momentum channel, thereby destabilizing the composite-fermion Fermi seas to produce non-Abelian fractional quantum Hall states.

We study a simple electron-phonon model on square and triangular versions of the Lieb lattice using an asymptotically exact strong coupling analysis. At zero temperature and electron density $n=1$ (one electron per unit cell), for various ranges of parameters in the model, we exploit a mapping to the quantum dimer model to establish the existence of a spin-liquid phase with ${\mathbb{Z}}_2$ topological order (on the triangular lattice) and a multicritical line corresponding to a quantum critical spin liquid (on the square lattice). In the remaining part of the phase diagram, we find a host of charge-density-wave phases (valence-bond solids), a conventional $s$-wave superconducting phase, and with the addition of a small Hubbard $U$ to tip the balance, a phonon-induced $d$-wave superconducting phase. Under a special condition, we find a hidden pseudospin $SU(2)$ symmetry that implies an exact constraint on the superconducting order parameters.

Perovskite rare earth nickelates exhibit remarkably rich physics in their metal-insulator and antiferromagnetic transitions, and there has been a long-standing debate on whether their magnetic structures are collinear or noncollinear. Through symmetry consideration based on the Landau theory, we discover that the antiferromagnetic transitions on the two nonequivalent Ni sublattices occur separately at different Néel temperatures induced by the O breathing mode. It is manifested by two kinks on the temperature-dependent magnetic susceptibilities with the secondary kink being continuous in the collinear magnetic structure but discontinuous in the noncollinear one. The prediction on the secondary discontinuous kink is corroborated by an existing magnetic susceptibility measurement on bulk single-crystalline nickelates, thus strongly supporting the noncollinear nature of the magnetic structure in bulk nickelates, thereby shedding new light on the long-standing debate.

Interfaces of phase-separated systems roughen in time due to capillary waves. Because of fluxes in the bulk, their dynamics is nonlocal in real space and is not described by the Edwards-Wilkinson or Kardar-Parisi-Zhang (KPZ) equations, nor their conserved counterparts. We show that, in the absence of detailed balance, the phase-separated interface is described by a new universality class that we term $|\mathbf{q}|\mathrm{KPZ}$. We compute the associated scaling exponents via one-loop renormalization group and corroborate the results by numerical integration of the $|\mathbf{q}|\mathrm{KPZ}$ equation. Deriving the effective interface dynamics from a minimal field theory of active phase separation, we finally argue that the $|\mathbf{q}|\mathrm{KPZ}$ universality class generically describes liquid-vapor interfaces in two- and three-dimensional active systems.

We present the finite-size Kuramoto model analytically continued from real to complex variables and analyze its collective dynamics. For strong coupling, synchrony appears through locked states that constitute attractors, as for the real-variable system. However, synchrony persists in the form of complex locked states for coupling strengths $K$ below the transition $K^{(\mathrm{pl})}$ to classical phase locking. Stable complex locked states indicate a locked subpopulation of zero mean frequency in the real-variable model and their imaginary parts help identifying which units comprise that subpopulation. We uncover a second transition at $K^{\prime }<K^{(\mathrm{pl})}$ below which complex locked states become linearly unstable yet still exist for arbitrarily small coupling strengths.

We demonstrate that for a rigid and incompressible network in mechanical equilibrium, the microscopic stress and strain follows a simple relation, $\sigma =p\mathbf{E}$, where $\sigma$ is the deviatoric stress, $\mathbf{E}$ is a mean-field strain tensor, and $p$ is the hydrostatic pressure. This relationship arises as the natural consequence of energy minimization or equivalently, mechanical equilibration. The result suggests not only that the microscopic stress and strain are aligned in the principal directions, but also microscopic deformations are predominantly affine. The relationship holds true regardless of the different (foam or tissue) energy model considered, and directly leads to a simple prediction for the shear modulus, $\mu =⟨p⟩/2$, where $⟨p⟩$ is the mean pressure of the tessellation, for general randomized lattices.

Hydrodynamic interactions can give rise to a collective motion of rotating particles. This, in turn, can lead to coherent fluid flows. Using large scale hydrodynamic simulations, we study the coupling between these two in spinner monolayers at weakly inertial regime. We observe an instability, where the initially uniform particle layer separates into particle void and particle rich areas. The particle void region corresponds to a fluid vortex, and it is driven by a surrounding spinner edge current. We show that the instability originates from a hydrodynamic lift force between the particle and fluid flows. The cavitation can be tuned by the strength of the collective flows. It is suppressed when the spinners are confined by a no-slip surface, and multiple cavity and oscillating cavity states are observed when the particle concentration is reduced.

In broad classes of inflationary models the period of accelerated expansion is followed by fragmentation of the inflaton scalar field into localized, long-lived, and massive oscillon excitations. We demonstrate that matter dominance of oscillons, followed by their rapid decay, significantly enhances the primordial gravitational wave (GW) spectrum. These oscillon-induced GWs, sourced by second-order perturbations, are distinct and could be orders of magnitude lower in frequency than the previously considered GWs associated with oscillon formation. We show that detectable oscillon-induced GW signatures establish direct tests independent from cosmic microwave background radiation for regions of parameter space of monodromy, and logarithmic and pure natural (plateau) potential classes of inflationary models, among others. We demonstrate that oscillon-induced GWs in a model based on pure natural inflation could be directly observable with the Einstein Telescope, Cosmic Explorer, and DECIGO. These signatures offer a new route for probing the underlying inflationary physics.

By respecting the conformal symmetry of the dual conformal field theory, and treating the conformal factor of the Anti-de Sitter boundary as a thermodynamic parameter, we formulate the holographic first law that is exactly dual to the first law of extended black hole thermodynamics with variable cosmological constant but fixed Newton’s constant.

We search for lepton-flavor-violating ${\tau }^{-}\to e^{-}\alpha$ and ${\tau }^{-}\to {\mu }^{-}\alpha$ decays, where $\alpha$ is an invisible spin-0 boson. The search uses electron-positron collisions at 10.58 GeV center-of-mass energy with an integrated luminosity of $62.8{\mathrm{fb}}^{-1}$, produced by the SuperKEKB collider and collected with the Belle II detector. We search for an excess in the lepton-energy spectrum of the known ${\tau }^{-}\to e^{-}{\overline{\nu }}_e{\nu }_{\tau }$ and ${\tau }^{-}\to {\mu }^{-}{\overline{\nu }}_{\mu }{\nu }_{\tau }$ decays. We report 95% confidence-level upper limits on the branching-fraction ratio $\mathcal{B}({\tau }^{-}\to e^{-}\alpha )/\mathcal{B}({\tau }^{-}\to e^{-}{\overline{\nu }}_e{\nu }_{\tau })$ in the range $(1.1–9.7)\times {10}^{-3}$ and on $\mathcal{B}({\tau }^{-}\to {\mu }^{-}\alpha )/\mathcal{B}({\tau }^{-}\to {\mu }^{-}{\overline{\nu }}_{\mu }{\nu }_{\tau })$ in the range $(0.7–12.2)\times {10}^{-3}$ for $\alpha$ masses between 0 and $1.6\mathrm{GeV}/c^2$. These results provide the most stringent bounds on invisible boson production from $\tau$ decays.

We study $B^{+}\to {\pi }^{+}{\pi }^0{\pi }^0$ using $711{\mathrm{fb}}^{-1}$ of data collected at the $\mathrm{\Upsilon }(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We measure an inclusive branching fraction of $(19.0\pm 1.5\pm 1.4)\times {10}^{-6}$ and an inclusive $CP$ asymmetry of $(9.2\pm 6.8\pm 0.7)\%$, where the first uncertainties are statistical and the second are systematic, and a $B^{+}\to \rho (770{)}^{+}{\pi }^0$ branching fraction of $(11.2\pm 1.1\pm 0.9_{-1.6}^{+0.8})\times {10}^{-6}$, where the third uncertainty is due to possible interference with $B^{+}\to \rho (1450{)}^{+}{\pi }^0$. We present the first observation of a structure around $1\mathrm{GeV}/c^2$ in the ${\pi }^0{\pi }^0$ mass spectrum, with a significance of $6.4\sigma$, and measure a branching fraction to be $(6.9\pm 0.9\pm 0.6)\times {10}^{-6}$. We also report a measurement of local $CP$ asymmetry in this structure.

Propagation of high-current relativistic electron beam (REB) in plasma is relevant to many high-energy astrophysical phenomena as well as applications based on high-intensity lasers and charged-particle beams. Here, we report a new regime of beam-plasma interaction arising from REB propagation in medium with fine structures. In this regime, the REB cascades into thin branches with local density a hundred times the initial value and deposits its energy 2 orders of magnitude more efficiently than that in homogeneous plasma, where REB branching does not occur, of similar average density. Such beam branching can be attributed to successive weak scatterings of the beam electrons by the unevenly distributed magnetic fields induced by the local return currents in the skeletons of the porous medium. Results from a model for the excitation conditions and location of the first branching point with respect to the medium and beam parameters agree well with that from pore-resolved particle-in-cell simulations.

Topological insulator-based methods underpin the topological classification of gapped bands, including those surrounding semimetallic nodal defects. However, multiple bands with gap-closing points can also possess nontrivial topology. We construct a general wave-function-based “punctured-Chern” invariant to capture such topology. To show its general applicability, we analyze two systems with disparate gapless topology: (1) a recent two-dimensional fragile topological model to capture the various band-topological transitions and (2) a three-dimensional model with a triple-point nodal defect to characterize its semimetallic topology with half integers that govern physical observables such as anomalous transport. This invariant also gives the classification for Nexus triple points ($\mathbb{Z}\times \mathbb{Z}$) with certain symmetry restrictions, which is reconfirmed by abstract algebra.

The fractional quantum Hall effect (FQHE) is known to host anyons, quasiparticles whose statistics is intermediate between bosonic and fermionic. We show here that Hong-Ou-Mandel (HOM) interferences between excitations created by narrow voltage pulses on the edge states of a FQHE system at low temperature show a direct signature of anyonic statistics. The width of the HOM dip is universally fixed by the thermal time scale, independently of the intrinsic width of the excited fractional wave packets. This universal width can be related to the anyonic braiding of the incoming excitations with thermal fluctuations created at the quantum point contact. We show that this effect could be realistically observed with periodic trains of narrow voltage pulses using current experimental techniques.

We present a numerically exact steady-state inchworm Monte Carlo method for nonequilibrium quantum impurity models. Rather than propagating an initial state to long times, the method is directly formulated in the steady state. This eliminates any need to traverse the transient dynamics and grants access to a much larger range of parameter regimes at vastly reduced computational costs. We benchmark the method on equilibrium Green’s functions of quantum dots in the noninteracting limit and in the unitary limit of the Kondo regime. We then consider correlated materials described with dynamical mean field theory and driven away from equilibrium by a bias voltage. We show that the response of a correlated material to a bias voltage differs qualitatively from the splitting of the Kondo resonance observed in bias-driven quantum dots.