Flat-band materials have attracted substantial interest for their intriguing quantum geometric effects. Here we investigate how singular flat bands (SFBs) respond to a static, uniform electric field in the weak-field regime and whether they can support single-particle dc transport. By constructing a minimal two-band lattice model, we show that away from the singular band crossing point (BCP), the Wannier-Stark (WS) spectrum of the flat band is well captured by an intraband Berry phase ${\mathrm{\Phi }}_{\mathrm{B}}$. The associated WS eigenstates are exponentially localized along the field direction, precluding dc transport. In contrast, near the BCP the interband Berry connection becomes prominent and drives Landau-Zener tunneling, which bends the flat-band WS ladder and delocalizes the SFB wave functions. Remarkably, this regime is governed solely by the maximal quantum distance $d$ through two geometric phases $(\theta ,\phi )$: $\theta$ characterizes the tunneling rate, while $\phi$ acts as a generalized Berry phase that reduces to the Berry phase away from the BCP. These results highlight the essential role of quantum geometry in enabling transport signatures in SFBs.

We introduce an $\mathrm{SU}(N)$ symmetric two-dimensional quantum spin model, the $X\text{−}Q$ model, which hosts a ground state transition between Néel antiferromagnetic and spontaneously dimerized states. The $Q$ terms are products of two adjacent singlet projectors on nearest-neighbor sites, as in the often studied $J\text{−}Q$ model (where $J$ is the Heisenberg exchange), while the $X$ terms are products of two permutation operators on second-neighbor sites. Quantum Monte Carlo simulations reveal close proximity to a deconfined quantum critical point for $N=2$, as in the $J\text{−}Q$ model. However, for $N>2$ the transition becomes strongly first order, contrary to conventional expectations that increasing $N$ should weaken discontinuities. We attribute this behavior to the inability of the $X$ term to induce U(1) fluctuations of the dimer pattern, while those from the $Q$ term are suppressed by $1/N$. These results provide insights into the interactions that support deconfined criticality.

The unique properties of two-dimensional moiré systems have been widely studied from many perspectives. However, relatively little work has investigated how the real-space structure of moiré systems can directly engender novel properties and functionalities. In this Letter, we explore how intriguing cooperative optical effects can emerge from the real-space superlattice formed by moiré excitons. Particularly, we show that the collective moiré exciton states can have either strongly enhanced (superradiant) or suppressed (subradiant) radiative decay rates, depending on their in-plane wave vector. These super- and subradiant states can be efficiently switched by a gate-induced electric field gradient. Moreover, the cooperative transmittance $T$ of the atomically thin moiré system can be switched from $T\approx 0$ (opaque) to $T\approx 1$ (transparent) with $\lesssim 1\%$ heterostrain or a 1° adjustment in the twist angle $\theta$. These features are robust against nonradiative losses and disorders, making the moiré system a highly versatile platform for cooperative quantum optics with potential applications in, e.g., single photon storage and switching.

Information-theoretic phase transitions, such as the measurement-induced phase transition (MIPT), characterize the robustness of quantum dynamics to local monitoring and are naturally formulated in terms of trajectories conditioned on typical measurement outcomes, which are naively accessible only through postselection. Here, we implement forced measurements to investigate how explicit postselection alters the nature of the transition. We find that postselection fundamentally alters the universality class by reweighting trajectories that are otherwise rare. In particular, we obtain a correlation-length exponent $\nu \approx 2.1$ larger than that of the standard MIPT and a negative effective central charge $c_{\mathrm{eff}}\approx -0.35$. We also compare the postselected MIPT to the entanglement transition of random tensor networks, and demonstrate that their universality class is the same. This setup further allows time-periodic, translationally invariant circuits with postselected weak measurements. In both models, we find that an on-site dimension of at least 3 (qutrits but not qubits) is necessary to induce a transition.

Baryonic effects such as AGN feedback can significantly impact the matter clustering, are harder to model from first principles, and emerge as a severe limiting factor in weak lensing cosmology. To tackle this issue, we propose a generic relation of mapping the observed matter clustering to its counterpart in a dark-matter-only universe. We verify this relation to be accurate at better than 1% level at $k<1h/\mathrm{Mpc}$ and $z\in [0,3]$ in both TNG and Illustris simulations, demonstrating its model independence to the underlying baryonic physics. Implementing this relation in observations will be made possible by the specifically designed cross-correlation statistics and baryon census (ionized diffuse gas through localized fast radio bursts, stellar mass through galaxy surveys, and neutral hydrogen through 21 cm mapping). It is capable of correcting the baryonic effect not only in the matter power spectrum, but also at the field level, as demonstrated by tests on the scattering transform statistics. This approach paves the way for constructing the dark-matter-only counterpart of the observed Universe, establishing an ideal cosmological laboratory for probing the dark universe.

Baryonic feedback is a leading contaminant in studying dark matter using cosmic shear. This has meant omitting much of the data during cosmological inference, or forward modeling the spatial distribution of gas around dark matter halos using models for baryonic feedback, which introduces nuisance parameters and raises questions of potential model misspecification. We propose a novel method of “baryon nulling” using cross-correlations between shear maps and fast radio burst (FRB) dispersion measures. We use the FLAMINGO suite of hydrodynamical simulations, whose power spectra span a wide yet realistic range of feedback variations, to demonstrate that our nulling procedures reduce sensitivity to feedback at $k\approx 1{\mathrm{Mpc}}^{-1}$ by a factor of a few, offering a valuable model-independent alternative to standard forward modeling procedures, which often assume a family of feedback models. Sensitive FRB surveys such as CHORD and the DSA-2000, and wide area surveys like Rubin, Roman, and Euclid, may enable the megaparsec-scale clustering of dark matter to be precisely constrained without a baryonic prior.

We employ a single worldline effective field theory in a Schwarzschild-Tangherlini background to compute the gravitational Compton amplitude up to third post-Minkowskian order. After excising the infrared divergences associated with the Weinberg phase, we establish a direct and exact map to results in black hole perturbation theory with a natural resummation and regularization of the forward divergences of the Compton amplitude. We also outline possible applications of this useful computational bridge for Compton amplitudes that include spin and tidal effects.

We present a complete calculation of radiative corrections to the inverse beta decay reaction, ${\overline{\nu }}_e+p\to e^{+}+n$, at reactor antineutrino energies using heavy-baryon chiral perturbation theory. Our analysis consistently incorporates quantum electrodynamics, chromodynamics, and electroweak contributions for the first time within this framework. We provide updated, high-precision cross-section predictions with a full error budget and present the positron energy spectrum, including radiative effects. The results are essential for normalizing the reactor antineutrino flux, determining neutrino oscillation parameters with subpercent accuracy, and searching for new physics at nuclear power plants.

The color-octet (CO) mechanism is a cornerstone of nonrelativistic QCD, yet knowledge of its long-distance matrix elements remains limited, preventing stringent tests of the theory. We demonstrate that the Artru-Collins asymmetry in hadronic decays of the $P$-wave bottomonium state ${\chi }_{b2}$ provides a direct probe of CO dynamics. At leading order, the asymmetry arises exclusively from the CO decay channel, whereas the color-singlet (CS) contribution affects only the unpolarized rate, so that a nonzero signal constitutes unambiguous evidence of the CO mechanism. This observable provides a novel way to extract the ratio ${\rho }_8$ between CO and CS matrix elements. Focusing on $e^{+}{e}^{-}\to \mathrm{\Upsilon }(2S)\to \gamma {\chi }_{b2}$ at Belle, we show that the asymmetric beam configuration preserves the asymmetry in the laboratory frame and avoids the strong suppression present in the center-of-mass frame. With the Belle II dataset, ${\rho }_8$ could be determined with sufficient precision to address the long-standing discrepancy between the lattice calculations and phenomenological determinations.

Hyperfine constant $A$ is a key parameter of the hyperfine structure and underpins precision spectroscopy and metrology. In this Letter, we develop a magnetic-field-calibration-free method for determining the ground-state hyperfine constant $A$ in an ultracold ${}^{40}\mathrm{K}$ Fermi gas by utilizing a pair of magnetically insensitive (“clock”) transitions. This overcomes the stringent magnetic-field calibration requirements of conventional methods. We measure the frequencies of these two magnetically insensitive transitions with Hz-level resolution over a range of magnetic fields and obtain the ground-state hyperfine constant $A=-h\times 285.730536(2)\mathrm{MHz}$, corresponding to an absolute uncertainty of about 2 Hz. Our value reduces the uncertainty by nearly 3 orders of magnitude compared with previous determinations, providing a substantially improved reference for high-precision spectroscopy and metrology with ${}^{40}\mathrm{K}$.

Thermal radiation is inherently broadband and incoherent, limiting its utility in applications requiring spectral selectivity such as molecular spectroscopy and free-space optical communications. Bound states in the continuum (BICs) provide a powerful route to confine light in open photonic systems and realize resonances with extremely high quality factors. Here we demonstrate high-$Q$ light emission from a photonic-phononic nonlocal metasurface composed of monocrystalline silicon on a 4H-SiC substrate. The platform supports BIC-enabled ultranarrow band emission for both TE and TM polarizations; specifically, we identify an off-$\mathrm{\Gamma }$ Friedrich-Wintgen BIC and a $\mathrm{\Gamma }$-point symmetry-protected BIC for TE polarization and a $\mathrm{\Gamma }$-point symmetry-protected BIC for TM polarization. Under TM polarization, coupling between the photonic mode of the metasurface and surface phonon polaritons in the SiC substrate produces strong field localization and a symmetry-enforced complementarity between the photonic and phononic resonances, in which the photonic $Q$ factor diverges while the phononic mode radiates maximally at the $\mathrm{\Gamma }$ point. Using a bonding-based fabrication approach that integrates monocrystalline silicon with SiC through an optically ultrathin interlayer, we experimentally realize a quasi-BIC thermal emitter with a measured $Q$ factor of 181. This represents the highest reported $Q$ factor for thermal emitters operating at wavelengths longer than $7\mathrm{\mu }\mathrm{m}$ and establishes photonic-phononic nonlocal metasurfaces as a platform for coherent and spectrally selective midinfrared thermal radiation.

Based on $e^{+}{e}^{-}$ annihilation data collected with the BESIII detector at center-of-mass energies from 4.600 to 4.699 GeV, corresponding to an integrated luminosity of $4.5{\mathrm{fb}}^{-1}$, we present the first measurement of the longitudinal polarization of $\mathrm{\Lambda }$ hyperon produced in the inclusive decay ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }X$, where $X$ denotes any allowed final states. The polarizations are determined to be ${\mathcal{P}}_{\mathrm{\Lambda }}=-0.393\pm 0.055_{\mathrm{stat}}\pm 0.020_{\mathrm{syst}}$ and ${\mathcal{P}}_{\overline{\mathrm{\Lambda }}}=0.288\pm 0.056_{\mathrm{stat}}\pm 0.017_{\mathrm{syst}}$. A search for $CP$ violation is performed using an asymmetry constructed from the $\mathrm{\Lambda }$ polarization and the $\mathrm{\Lambda }\to p{\pi }^{-}$ decay asymmetry parameter, and ${\mathcal{A}}_{CP}^{\mathrm{pol}}=0.15\pm 0.12_{\mathrm{stat}}\pm 0.03_{\mathrm{syst}}$ was obtained. Furthermore, an updated measurement of the absolute branching fraction is reported as $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }X)=(38.07\pm 0.38_{\mathrm{stat}}\pm 0.49_{\mathrm{syst}})\%$, representing a fourfold precision improvement over the previous BESIII measurement. A search for $CP$ violation in the decay rate yields ${\mathcal{A}}_{CP}^{\mathrm{dir}}=(1.5\pm {1.0}_{\mathrm{stat}}\pm {1.0}_{\mathrm{syst}})\%$. No evidence for $CP$ violation is observed in this inclusive charm baryon decay. The subscripts ‘stat’ and ‘syst’ denote statistical and systematic uncertainties, respectively.

The cytoplasm of eukaryotic cells is a complex fluid that harbors a variety of membrane-enveloped organelles with distinct spatial distributions and duties. Peroxisomes, for example, are vesicular entities with radii in the sub-micron range, dispersed all over the cytoplasm to provide oxidative reaction vessels across the cell. Here, we have tracked peroxisomes as biologically relevant tracer particles to explore the local structure of the cytoplasm. Focusing on the vast majority of (sub)diffusively moving peroxisomes, we show that these display a significant motion anisotropy even in the absence of intact actin filaments and microtubules or when the endoplasmic reticulum (ER) is disrupted. In untreated cells, the local preference direction aligns with a global axis that correlates with the cell’s long axis; disrupting the cytoskeleton or the ER progressively randomizes this alignment. Altogether, our data indicate that the cytoplasm features a weak nematic substructure rather than being an isotropic fluid.