Papers

Electron-phonon coupling is generally expected to suppress band topology, driving a topological band insulator into a trivial phase. Here we show that, using the prototypical Haldane-Holstein model at partial filling of a topological band, strong electron-phonon coupling can instead stabilize topological phases of matter. The electron-phonon coupling plays a double role: it generates the longer-range interactions that correlate the carriers and, in the attractive channel, also binds them into bosonic pairs. For spinful electrons, it pairs opposite spins into charge-$2e$ bipolarons that form a bosonic fractional Chern insulator (FCI) at filling $\nu=1/2$ with charge-$e$ semionic excitations. Tuning the band topology and the coupling strength maps out a rich phase diagram containing this bosonic FCI, superconductors condensed at the $M$ and $K$ points, and several charge-ordered solids. For spin-polarized electrons, strong coupling instead stabilizes a $C=2$ quantum anomalous Hall crystal (QAHC) at $\nu=1/3$. Electron-phonon coupling thus emerges as a route to, rather than an obstruction against, topology in partially filled Chern bands.

The homogeneous form associated with a symmetric tensor, restricted to the sphere, is the objective of the best rank-one approximation problem and, with random coefficients, the energy of a mean-field spin glass. Its critical points have been studied extensively, but the global organization of the landscape they form is far less understood. We study this global structure for positive orthogonally decomposable tensors. We determine the persistent homology of the sublevel and superlevel filtrations in closed form, for every homological dimension $q$, every ambient dimension $D$ and every tensor order $k$, via a recurrence in the ambient dimension. Taking the coefficients to be random, we further prove laws of large numbers for the resulting persistence diagrams at dimension $0$ and $D-2$, giving an exact description of the typical global topology of a spin-glass-like energy landscape. We illustrate our results with numerical computations and simulations.

Axial chiral phonons, which carry angular momentum and exhibit unusually large magnetic moments, provide a new degree of freedom for controlling the time-reversal symmetry and magnetic properties of quantum materials. While infrared-active axial phonons are efficiently excited to large amplitudes by circularly polarized terahertz pulses, their application may be constrained by short lifetimes, small penetration depths, low spatial resolution, and limited availability of optical sources. Here, we report that an axial Raman-active phonon mode in CeF3 exhibits a significant magnetic moment and an exceedingly long lifetime that more closely matches the paramagnetic spin dynamics. The axial phonon population is resonantly driven by a near-infrared laser pulse with rotating linear polarization, known as an optical centrifuge, a coherent control scheme never applied to solids before. The phonon-driven magnetization observed by time-resolved Faraday rotation scales quadratically with incident power and rapidly decreases at high temperatures, consistent with phonon inverse Faraday effect from many-body spin-phonon coupling. Our findings open a new avenue for using shaped laser pulses from widely accessible light sources to manipulate coherent axial chiral phonons and ultrafast spintronics.

Let $\mathcal{A}^{\bf z}_{\mathfrak{g}}$ be the Gaudin algebra for the general linear Lie (super)algebra $\mathfrak{g}$ with respect to a sequence ${\bf z} \in \mathbb{C}^\ell$ of pairwise distinct complex numbers, and let $\mathbb{L}$ be any $\ell$-fold tensor product of (infinite-dimensional) unitarizable highest weight $\mathfrak{g}$-modules. Fix a singular weight $\xi$ of $\mathbb{L}$. We show that the singular weight space $\mathbb{L}^\text{sing}_\xi$ is a cyclic $\mathcal{A}^{\bf z}_{\mathfrak{g}}$-module, and that the Gaudin algebra $(\mathcal{A}^{\bf z}_{\mathfrak{g}})_{\mathbb{L}^\text{sing}_\xi}$ for $\mathbb{L}^\text{sing}_\xi$ is a Frobenius algebra. We also show that $(\mathcal{A}^{\bf z}_{\mathfrak{g}})_{\mathbb{L}^\text{sing}_\xi}$ is diagonalizable with a simple spectrum for a generic ${\bf z}$. Furthermore, we establish a super version of the Bethe ansatz for $\mathcal{A}^{\bf z}_{\mathfrak{g}}$ on $\mathbb{L}^\text{sing}_\xi$.

How much can a magnetic field change before a quantum spin texture loses its skyrmion charge? For a triangulated spin-$s$ texture on $N$ quantum sites, we determine the smallest change in its local moments that makes the reconstructed topological charge ill-defined, allowing unequal error bounds and fixed boundary moments. Combined with spectral perturbation theory, this geometric threshold yields explicit magnetic-field intervals that preserve the ground-state charge, scaling as $1/N$ when the gap and geometric margin have positive limits. We apply the bounds to finite spin-$1/2$ systems with exchange and Dzyaloshinskii-Moriya interactions. In a rigorously verified seven-spin example the charge changes at a single certified field, while the excitation gap and all local spin polarizations remain bounded away from zero; there the geometric margin vanishes linearly.

Scale-invariant avalanche dynamics are commonly associated with criticality and robust, universal size exponents. Dissipation is generally expected to drive the system away from the critical point, progressively suppressing large events. The Olami–Feder–Christensen (OFC) model challenges this picture: in its non-conservative regime, the avalanche-size exponent is non-universal and can exceed the mean-field value $\tau=3/2$, while system-spanning events persist even at large dissipation. Here, we show that these apparently anomalous features are also observed experimentally in a two-dimensional granular system displaying scale-invariant avalanche dynamics. By increasing interparticle friction, and therefore dissipation, the avalanche-size exponent increases from $\tau=1.58$ to $\tau=1.83$, while the upper cutoff remains proportional to the system size. We further identify similarities between experiment and the OFC model in their memory effects, local dynamics, and the emergence of better-than-random predictability of large events. The latter indicates that the system does not remain permanently critical, but instead evolves through configurations with different propensities to generate extreme events. Our results suggest that OFC-like dynamics are not merely an anomalous feature of a particular model, but may provide a relevant framework for understanding scale-invariant dynamics with $\tau>3/2$ in real dissipative systems.

In the context of the AdS/CFT correspondence, the Jafferis-Lewkowycz-Maldacena-Suh (JLMS) formula relates the boundary modular Hamiltonian to the HRT area operator and the corresponding bulk modular Hamiltonian. In standard discussions of a holographic code built from perturbative excitations on a fixed classical background, the $A/4G$ term dominates over the bulk modular Hamiltonian in the limit $G \to 0$. However, this setup is insufficient to describe the action of boundary modular flows that change the classical background. In contrast, our recent discussion of `large' codes provides a useful framework to obtain a JLMS formula that relates bulk and boundary modular flows acting on appropriate states in the code. Here, one sees that the bulk modular Hamiltonian is not in fact subdominant when the modular flow defined by one state acts on another state peaked around a sufficiently different classical background. Instead, the bulk modular Hamiltonian can be of order $1/G$ and can dominate over the $A/4G$ term. Nevertheless, we show that if the two states have the same classical background except for data conjugate to the HRT area then, under mild assumptions and over a large range of flow parameters, the modular-flowed state is described by a classical background given by the HRT-area flow alone.

Magnetic particle spectroscopy (MPS) enables sensitive detection of magnetic nanoparticles (MNPs) and characterization of their dynamic magnetization through higher-order harmonics. Here, we synthesized citrate-functionalized, 30 nm cubic Zn0.4Fe2.6O4 (ZFO) MNPs and investigated their association with SKOV3 ovarian cancer cells using MPS. The ZFO MNPs exhibited a crystalline spinel structure, a mean hydrodynamic diameter of 39.4 nm, strong room-temperature magnetization, low coercivity, and citrate-associated surface functional groups. Live/Dead imaging indicated good cytocompatibility after 24 h exposure at concentrations up to 0.5 mg/mL, while bright-field microscopy showed concentration-dependent cell-associated nanoparticle accumulation. Two MPS drive fields were compared using ZFO MNPs dispersed in DI water and agar as relatively unrestricted and strongly confined reference states. The 7.75 kHz, 20 mT condition retained more higher-order harmonics than 11.37 kHz and 10 mT and produced a larger and order-dependent spectral separation between the two states; it was therefore selected for the cellular measurements. After ZFO exposure and removal of unbound nanoparticles, MPS detected cell-associated MNPs in samples containing 0.1, 1, and 2x10^6 SKOV3 cells. The 3rd-, 5th-, and 7th-harmonic amplitudes increased proportionally with cell number, with power-law exponents of 1.03-1.09. We also report that most normalized harmonic ratios from the 1- and 2x10^6-cell samples fell between the water and agar references, indicating partial restriction of Brownian rotation in the cellular environment. These findings demonstrate that MPS can detect cell-associated MNPs while providing complementary spectral information about their ensemble-averaged physical confinement, supporting its application in magnetic cell labeling and cell-tracking studies.

The ringdown of a black hole following a merger is a potential candidate for revealing the signatures of quantum gravity in the emerging gravitational waves. In quantum theory, black holes are expected to have a discrete area and energy spectrum, which conflicts with the classical notion of an horizon that absorbs all infalling perturbations. We propose that the quantum black hole dissipates the energy it cannot absorb by emitting “soft” gravitons that carry away the energy difference between the energy of the infalling perturbation and the quantum transition energy. We find that the ringdown spectrum is consequently enriched with low-frequency components, and that there exists a weak low-frequency flux that persists for a timescale much longer than the ringdown itself.

The Scharnhorst effect in quantum electrodynamics predicts a superluminal velocity shift $\delta c>0$ at low photon frequencies due to vacuum fluctuations between two mirrors. Although theoretically robust (no causality violation), the effect is extraordinarily small ($\delta c/c\approx 10^{-32}$ for mirrors $1\,\mu{\rm m}$ apart) and outside current experimental reach. Here we propose a condensed matter analogue, replacing the photons in the electromagnetic vacuum by phonon excitations of a Bose-Einstein condensate. In an idealized geometry, the two-dimensional surface of a cylinder (circumference $L$) at zero temperature, the axial speed of sound is increased due to zero-point fluctuations of the condensate by $\delta c/c\simeq 5\times 10^{-3}\,\tilde{g}$ at $L\simeq 2\,\xi$, to first order in the dimensionless interaction constant $\tilde{g}\simeq 10^{-1}$ of the Bose gas of healing length $\xi\simeq 1\,\mu{\rm m}$. This is 28 orders of magnitude larger than the photonic effect, basically because phonons have a self-interaction while photons only interact via massive electrons. We discuss the prospects for observation of the acoustic Scharnhorst effect, the main restriction being the low-temperature requirement.

The population of extragalactic black holes has been significantly expanded and better understood since the first detection of gravitational waves. Over the past decade, approximately 290 events have been confirmed to involve at least one black hole. In contrast, the galactic black hole population has grown at a much slower pace, with only 42 systems possessing mass estimates, while the vast majority remain as candidates. In this work, we present the first update of a Bayesian analysis of the mass distribution of galactic black holes since 2011, previously based on a sample of 15 low-mass X-ray binaries and 5 high-mass X-ray binaries. Our update includes 28 low-mass X-ray binaries, 6 high-mass X-ray binaries, 7 detached binaries and 1 isolated black hole, also present in the living catalog CatNoir which we introduce. We apply a Bayesian framework using five parametric models – Gaussian, two-Gaussian, log-normal, power-law, and decaying exponential – and compare their performance in fitting the observed data. Furthermore, we inspect the effect of removing model-dependent systems from the sample. Our results suggest that the power law better describes the Combined sample, while the Gaussian is preferred for the LMXB-only sample, closely followed by the two-Gaussian and log-normal. We derive the $1\%$-quantile of the preferred model's posterior predictive distribution to access information about the lower mass gap. For the Combined and LMXB Samples, we find $M_{1\%} > 4.06\,M_\odot$ and $M_{1\%} > 2.56\,M_\odot$ (at $90\%$ C.I.), respectively. The LMXB result allows for the existence of a sparsely populated Gap, instead of a completely empty one.

Programmable photonic integrated circuits are emerging as increasingly large and versatile interferometric processors operating at room temperature. However, their native operations are linear, while many computational tasks require nonlinear input-output transformations that typically rely on nonlinear optical materials or resonant devices. Here, we establish a direct mapping between quantum signal processing (QSP) and the native two-mode operations of programmable interferometric photonic integrated circuits, showing that the $SU(2)$ structure required by QSP can be realized through programmable phase control and mode mixing. We experimentally demonstrate this correspondence using dual-rail single-photon encoding on a 24-mode programmable photonic integrated circuit, realizing QSP sequences up to depth $L=11$ and synthesizing STEP, ReLU and SELU functions through programmable phase control. The optical transformation remains linear, while repeated encoding of the input variable and coherent interference produce a nonlinear dependence of the output probabilities on the encoded variable. Across all accessible circuit depths, the measured responses follow the programmed QSP transformations, with hardware-induced mean squared errors between $10^{-3}$ and $10^{-2}$, all remaining below the intrinsic finite-depth approximation error. These results establish an algorithm-to-hardware mapping of QSP on programmable photonic processors. They also demonstrate an algorithmic route to programmable nonlinear functions of encoded variables on linear photonic hardware.

The historical record of low-latitude aurorae is essentially a poorly sampled record of the largest space weather events (SWEs). Its use for the identification of individual solar cycles is hindered by the low event rate and by the fact that the solar cycle profile of the occurrence of SWEs does not closely follow the variation of sunspot numbers. Based on recent studies of the solar cycle dependence of the occurrence rates of large SWEs, here we construct Monte-Carlo simulations of a large number of activity cycles to identify the optimal procedure to infer the characteristics of underlying solar cycles from the sparse record. We find that a reliable reconstruction of the cycle phase ($>90$% of reconstructed minima corresponding to actual minima within $\pm 2$ years) is possible whenever the long-term mean event rate (annual mean number of space weather events resulting in low-latitude auroral sightings) reaches or exceeds a value around 3. This condition is found to be satisfied during most of the the Early Modern Active Period (EMAP), a century-long period of normal solar activity between the Spörer and Maunder Minima. For the numbering of solar cycles in the EMAP we introduce the "telescopic era", where T$n$ denotes the $n$th cycle from the first telescopically observed cycle, T$0$, ongoing in 1610. Using our optimal procedure we reconstruct a series of 8 solar activity cycles from T$-5$ to T$2$ (1560-1640). Earlier cycles starting from 1540 can be reconstructed with a somewhat lower degree of reliability. Comparing our results with radionuclide-based reconstructions and sunspot observations we find a good overall correspondence, with the exception of the last cycle before the Maunder Minimum.

Expected sensitivity calculations in frequentist analysis using neural simulation-based inference often require large simulated samples to approximate an unbinned Asimov dataset. We construct a finite weighted reference sample, for analyses based on learned density ratios, for which the generating parameters globally maximize the weighted likelihood. A toy example with five-dimensional observable space based loosely on high-energy physics models shows that an Asimov dataset consisting of as few as 256 weighted reference events closely reproduce the expected test statistic scans obtained with two million simulated reference events. The resulting test statistic distributions are also shown to agree with independent simulator-based pseudo-experiments. We note that this agreement with the simulator depends on the accuracy of the learned ratios and must be validated explicitly.

Hidden-free-fermion (HFF) Hamiltonians exhibit free-fermion spectra despite lacking an explicit quadratic representation, yet their algebraic provenance and periodic-boundary behavior remain open questions. Here we establish that a broad class of HFF models arises from distinct Lax operator realizations of a twisted multistate Perk–Schultz \(R\) matrix. Its reflected degeneration generates a closed finite hierarchy of mutually commuting transfer matrices, whose functional relations determine the complete many-body spectrum. As a decisive example, we solve the inhomogeneous free-fermions-in-disguise (FFD) chain, which exhibits HFF, nested HFF, or interacting spectra, depending on its coupling. The homogeneous FFD chain with both one-wrap and periodic boundary conditions exhibits an emergent cubic finite-size gap while retaining the exact \(z=3/2\) bulk behavior. The construction extends to higher-state and face-type realizations, providing a common algebraic framework for coupling-dependent spectral organization and multiscale behavior in interacting quantum systems.

A new methodology is developed for quantum machine learning which enables variational quantum circuits to learn linear and non-linear solution operators to differential equations. This is devised by extending the framework of the DeepONet, a technique for modeling differential equations. The branch and trunk neural networks are replaced by variational quantum circuits, leveraging the quantum universal approximation theorem. The methodology is tested on several differential equations and yields low approximation & generalization errors even with shallow circuit depths. In addition, it does not encounter barren plateaus during training. The model displays improved error and parameter scaling relative to the classical DeepONet. This is due to the intrinsic property that the approximation error depends on the dimension of the input function space, rather than the number of sensor locations. A theoretical framework is established in the form of explicit error bounds, which measure the contributions of the truncation, branch, and trunk circuit errors to the total operator approximation error. Full derivations for the error bounds are developed in the norms $L^2$, $L^p$, $C^0$, and Sobolev $H^k$, along with a classical-quantum comparative analysis (as Supplemental Materials).

We develop the first time-domain reduced order quadrature for gravitational waves in the early inspiral period, motivated by the need for dataset compression in the presence of gaps, uneven sampling, and dense covariance matrices. A single reduced basis with 1290 elements can represent inspirals from supermassive black hole binary sources with chirp masses between $10^7-10^{10}$ $M_\odot$, but in the presence of non-stationary noise $\sim 1290^2$ reduced order quadrature weights must be stored. We are able to reduce the stored weights by a factor of two by partitioning our parameter space by GW frequency, with relative waveform/likelihood accuracies remaining below $10^{-5}$/$10^{-3}$ after partition. Finally, we point out that heterodyning can be combined with reduced order methods with no loss in accuracy. Our reduced order quadrature makes inspiral searches in the time domain feasible for both pulsar timing arrays and relative stellar astrometry.

We investigate exact spherically symmetric and static black hole solutions in a non-minimally coupled Einstein–Maxwell theory of the $Y(R)F^2$ type, extended by a minimally coupled real scalar field and an anisotropic matter distribution. The Maxwell field is coupled to the spacetime curvature through an arbitrary function of the Ricci scalar, while the scalar field is described by a kinetic term and a scalar potential. We obtain exact solutions for power-law and logarithmic forms of the non-minimal coupling function and analyze the corresponding spacetime geometries. In particular, we identify a special $\beta=-1/3$ case for which the general power-law solution becomes singular and derive a new logarithmic metric by solving the field equations independently. The resulting configurations are asymptotically flat and exhibit modified gravitational properties associated with the interplay between the scalar field, anisotropic matter, and non-minimal electromagnetic coupling. We further show that the magnetic solutions admit electrically charged counterparts through an electromagnetic duality transformation, under which the metric and scalar sector remain invariant while the non-minimal coupling function is inverted. The obtained solutions provide a useful framework for investigating black hole horizons, thermodynamic properties, geodesic motion, and astrophysical phenomena such as galactic rotation curves in curvature-dependent electromagnetic theories.

A ferroelectric surface in contact with an ionic or molecular reservoir is intrinsically a ferroionic state in which polarization and compensating surface charge are thermodynamically coupled. Surface chemical compensation is known to control the magnitude and sign of ferroelectric polarization, yet the competing instability toward domain formation has usually been treated separately. Here we develop a static theory in which polarization, electrochemical surface charge, and finite-wave-vector domain formation are analyzed within a single thermodynamic framework for uniaxial polarization orientation. The central quantity is the differential chemical capacitance, which determines how strongly the surface charge can respond to a spatial modulation of polarization and therefore differs fundamentally from the equilibrium screening charge. We derive the homogeneous equation of state, the finite-wave-vector stability kernel, analytical domain-onset wavelengths and thickness scalings, and weakly nonlinear stripe and checkerboard solutions for both second- and first-order ferroelectrics. For a first-order transition, a finite-amplitude stripe state can become thermodynamically favorable before the homogeneous linear spinodal when the effective quartic coefficient is negative; this pre-spinodal window closes as the biased background polarization increases. Dense numerical phase maps confirm the analytical structure and show how chemical potential and film thickness reorganize weakly polar, monodomain, and polydomain states. Numerical analysis for BaTiO3 realization illustrates the corresponding temperature, oxygen-pressure, and thickness scales and identifies experimentally testable regimes in which chemical screening stabilizes the homogeneous state against the columnar 180{\deg} instability considered here or domain formation becomes the preferred route for depolarization-energy reduction.

Quantum algorithms for topological data analysis compute Betti numbers, the ranks of the homology groups of a simplicial complex, which can be read off from the kernel of a combinatorial Laplacian. Deciding whether a Betti number of a clique complex is nonzero is $QMA_1$-hard, and remains so under a spectral gap promise on vertex-weighted graphs. Integral homology, however, contains information inaccessible to the Laplacian spectrum. A new part that appears in integral homology is torsion: cycles that become boundaries only after being traversed several times, as in a projective plane or a Klein bottle. We provide a simple reduction that allows us to establish the first hardness results for the problem of detecting torsion. We attach to an arbitrary clique complex a fixed $31$-vertex triangulation of the projective plane. The $k$th mod-$2$ Betti number of the input then reappears as $2$-torsion two degrees up, while all rational homology disappears and every combinatorial Laplacian acquires a constant spectral gap. We conclude that detecting torsion in clique complexes of unweighted graphs is $NP$-hard, even under a constant gap promise, and that it is $QMA_1$-hard if mod-$2$ clique homology is.

A collection of evidence is presented showing that the conjectured reverse isoperimetric inequality (RII) for asymptotically anti-de Sitter (AdS) as well as de Sitter (dS) black holes, ${\cal R}_\text{RII} \ge 1$, is of fundamental importance and its violation (${\cal R}_\text{RII} < 1$) gives rise to either thermodynamic instabilities, or physically unreasonable solutions, or naked singularities. We show that AdS black holes violating reverse isoperimetric inequality, known as superentropic black holes, satisfy neither mechanical stability requirement of ${\kappa _T} \geqslant {\kappa _S} \geqslant 0$ nor thermal stability requirement of ${C_P} \geqslant {C_V} \geqslant 0$. This property makes them thermodynamically unstable for the whole range of parameter space and explains all the diverse behaviors so far reported. We conjecture this statement holds for all superentropic black holes. We confirm that there is no counterexample to the thermodynamic instability conjecture of superentropic black holes and extend this to dS space by presenting the first example of superentropicity in dS space. By bringing evidence, we then propose two other conjectures: 1) there is no asymptotically flat limit of superentropic black holes, and 2) there exist two stronger versions of Penrose isoperimetric inequality (PII) for asymptotically flat black holes; the first is the asymptotically flat limit of the RII and the second is a new inequality in terms of the ADM mass and the thermodynamics volume, that we call thermo-volumetric inequality, obtained via insights from the $\Lambda \to 0$ limit of extended black hole thermodynamics in AdS. We show that the Penrose isoperimetric inequality (PII) is weaker than the reverse isoperimetric inequality (RII), as demonstrated explicitly for $D=4,5$ and for all black hole families we have examined.

We study the thermodynamics of asymptotically flat five dimensional Einstein Gauss Bonnet black holes within the framework of the extended generalized uncertainty principle (EGUP). The geometry dependent localization scale is fixed by requiring the undeformed relation to reproduce the surface gravity temperature. The resulting expression consistently recovers the GUP, EUP, and semiclassical limits, while imposing a joint constraint on the minimum length and minimum momentum parameters. Due to the nonmonotonic behavior of the effective localization scale, the reality condition does not generically yield a unique minimum horizon radius. Depending on the parameter values, the admissible domain may remain connected, develop a degenerate critical radius, or split into two disconnected branches. We derive the entropy, heat capacity, and Helmholtz free energy, and analyze their behavior numerically. The Gauss Bonnet coupling shifts and suppresses the near horizon temperature maximum, whereas the EUP sector induces a temperature minimum followed by linear growth at large radius. In the two branch regime, the outer endpoint exhibits finite temperature and vanishing heat capacity but is approached from the locally unstable side, and should therefore be interpreted as a limiting thermodynamic configuration rather than a dynamically established remnant. Finally, we show that the perturbative entropy deviates from the exact result at large radius, and that the leading GUP entropy correction persists in the Einstein gravity limit.

Metallic altermagnets remain rare, particularly in low-symmetry three-dimensional crystals where spin-split electronic bands and chiral magnon excitations can coexist. We report a family of metallic $d_{yz}$-wave altermagnets in the orthorhombic ternary borides XCoB$_2$ (X = Ta, Zr, Hf), which crystallize in the centrosymmetric $Pnma$ structure with G-type collinear magnetic order. Symmetry analysis within the magnetic space group $Pnm'a'$ (BNS No.~62.447) predicts a nonrelativistic spin splitting proportional to $k_yk_z$, with symmetry-enforced degeneracy on the $k_y$ and $k_z$ nodal planes, consistent with first-principles calculations. On the $k_x=0$ plane, the momentum-averaged spin splitting reaches 88.4, 52.3, and 70.6~meV at the Fermi level in TaCoB$_2$, ZrCoB$_2$, and HfCoB$_2$, respectively, with maxima exceeding 200~meV in all three compounds. Exchange analysis shows that the altermagnetic magnon splitting originates from symmetry-inequivalent sixth-neighbour inter-sublattice interactions. The chirality splitting reaches 1.51, 2.03, and 3.10 meV below 50 meV in TaCoB$_2$, ZrCoB$_2$, and HfCoB$_2$, respectively, making it accessible to inelastic neutron scattering. Monte Carlo simulations yield N'eel temperatures of $67\pm1.1$, $330\pm5.7$, and $307\pm5.0$~K, placing ZrCoB$_2$ and HfCoB$*2$ above room temperature. With spin-orbit coupling included, all three compounds host symmetry-protected Weyl points near the Fermi level, Fermi-arc surface states and sizable intrinsic anomalous Hall conductivities $\sigma*{zx}$ of $+342$, $-392$, and $-221$~S/cm at the Fermi level, reaching maximum magnitudes of $763$, $942$, and $924$~S/cm for TaCoB$_2$, ZrCoB$_2$, and HfCoB$_2$, respectively. $X$CoB$_2$ therefore provides a single compensated platform carrying both magnonic and electronic chirality, one in the spin waves and the other in the Berry curvature, without any stray field.

A contiguous cartogram is a map whose area is proportional to a quantity such as population. The defining condition, that the Jacobian determinant of the deformation equals the density, is one equation for two unknown functions, so every cartogram method adds a tie-breaker, usually implicitly. Optimal transport makes the tie-breaker explicit: among all density-equalising maps of the frame onto itself, take the one that moves the population least in the mean-square sense. By Brenier's theorem that map is the gradient of a convex potential, so it has no local rotation anywhere and cannot fold. We compute this map for the world population of 2025 on a 4096 by 4096 Mercator grid (10 km cells) from the GHS-POP raster, using the fixed-point Monge-Ampère iteration of Benamou, Froese and Oberman with spectral Poisson solves, continuation in the population share and an ocean-only buffer, on a laptop GPU. Against a Gastner-Newman diffusion cartogram of the same density we find the same transport cost to within 0.4 per cent and density errors of a few per cent for both, but a median local rotation of 8.8 degrees for diffusion against 0.01 for transport, and a median anisotropy of 6.30 against 3.93. The construction extends to local refinement, by transporting a city's 100 m population onto the area measure the global map assigns to it, and to a semi-discrete counterpart: 8,192 Laguerre cells of 1.00 million people each. Code, data provenance and every figure's inputs are public.

We fit the circular velocity data, derived from weak lensing observations of isolated galaxies selected from the KiDS survey in four baryonic mass bins, using three different dark matter profiles. These include NFW, Burkert, and pseudo-isothermal profile. We find that the NFW and Burkert profiles cannot adequately fit the circular velocity data for all the four baryonic mass bins, whereas only the pseudo-isothermal profile can fit the data for all the four bins.

Rapid reset and readout of qubit states are essential for quantum error correction, yet accelerating these operations through stronger coupling to a dissipative environment inevitably increases qubit decay via the Purcell effect. Here we present a broadband Purcell filter that decouples the reset and readout paths, enabling both operations to be independently optimized without compromising qubit coherence. The filter employs two engineered notches - an intrinsic notch and a bandstop notch - to provide broadband Purcell protection, together with an additional reset stub that creates a reset mode below the protected band. To enable fast reset while suppressing filter-mediated interactions between qubits, we couple each qubit to a dedicated reset resonator. We experimentally demonstrate Purcell-limited relaxation times exceeding 1 ms across a 1.2 GHz bandwidth, simultaneously with 500 ns readout without a Josephson parametric amplifier and 100 ns reset with 99.6% efficiency. The reset resonator is designed with a deliberate kappa-chi mismatch, which suppresses photon-shot-noise-induced dephasing by a factor of 70 compared to the readout resonator. Our work provides a scalable hardware solution that resolves the traditional trade-off between fast qubit operations and qubit protection, advancing the prospects for fault-tolerant quantum computing.

We present the first dark matter density profile derived directly from James Webb Space Telescope JADES Data Release~3 NIRSpec observations of $N = 587$ galaxies spanning the cosmic noon epoch $1.5 \leq z \leq 3.5$. From each NIRSpec G235M/G395M spectrum we extract the H$\alpha$ emission-line velocity dispersion $\sigma_{\rm ha}$, stack galaxies in four redshift bins of $\Delta z = 0.5$, and reconstruct representative group rotation curves within the General Theory of Relativity. Fitting the four-parameter modified exponential model and deriving the exact GTR energy density, we reduce the profile to a compact $[2/3]$ Padé approximant with all coefficients determined in closed form from JWST observations. The profile is cusp-free, fully analytic, and redshift-dependent. Energy conditions, causality, and orbital stability are all satisfied. Most strikingly, the central density $\rho(0)$ varies by less than $15\%$ across $z = 1.5$–$3.5$ despite a $35\%$ decline in the asymptotic rotation velocity, revealing a universal dark matter core saturation density at cosmic noon decoupled from baryonic evolution.

Cutting stock problems are of large relevance to a variety of industry branches. Here, we present a linear programming formulation for a restricted version of the multistage 2D cutting stock problem with Guillotine cuts and test it on published benchmark instances. After this, we derive a non-exact reformulation in quadratic unconstrained binary optimization (QUBO) form via unbalanced penalization, which we show to have possible benefits in modeling the problem with usable leftovers. This work mainly considers the restricted formulation, in which the dimensions of each cut are determined by those of a single required piece. We further discuss how the approach can be extended to the unrestricted problem, which allows more general cutting patterns involving cuts with dimensions of multiple required pieces and naturally gives rise to quadratic terms in the inequalities of the problem formulation. We showcase solutions via a Simulated Annealing solver for the restricted problem class, where we mainly study the performance of the iterative augmented Lagrangian method. We also discuss possible applications of Quantum Annealing in this setting, as a strong motivation to research QUBO formulations.

The dispersion spectrum of a fluid-loaded elastic waveguide is a non-Hermitian system with eigenmodes on a two-sheeted Riemann manifold. Although exceptional points (EPs) organize avoided crossings, the topological rules by which fluid loading restructures the observable spectrum (both physically admissible modes and their connectivity) remain unknown, and conventional solvers fail to recover complete branches. Here we establish these rules. We prove that, for real elastic moduli and real fluid parameters, EPs obey a conjugate-pair symmetry, and that a pair on the physical sheet enforces an avoided crossing of real wavenumbers between the two modes it controls, yielding a topological criterion for mode identification. We then identify two independent reconstruction mechanisms. First, the physical observation space expands continuously: a mode observable above its vacuum cut-off can extend downward to the sound line, admitting solutions in a frequency band empty in vacuum; vacuum-anchored seeds above cut-offs continued downward capture such branches systematically. Second, EP migration rewires mode connectivity: as fluid density increases, conjugate pairs leaving the physical sheet (signaled by a sign reversal of the imaginary part of either the in-plane or the vertical wavenumber) leave the two previously coupled physical branch segments unconnected by any EP within the observation space; they become independent curves that may intersect freely on the real frequency axis, with the narrowest veerings losing their topological protection first. Mirror-symmetry breaking births additional EPs generically in the trapped regime but only conditionally in the leaky regime. Numerical computations on symmetric and asymmetric composite laminates under single- and double-sided water loading validate the framework, recovering multiple leaky branches missed by standard solvers.

Buckled colloidal monolayers constitute a versatile soft-matter platform for engineering artificial spin lattices, with each particle serving as a single Ising spin. While the average Ising coupling energy has been approximately derived for perfect particle lattices, extracting the complete set of coupling parameters from real samples remains inaccessible. Here, we apply an inverse method to reconstruct all nearest-neighbor effective Ising coupling energies from measured colloidal spin configurations. We design multiple experimental protocols to control the thermodynamic state of the colloidal system, from isotropic compression and shear deformation to modulation of interparticle attraction, each giving rise to distinct spin configurations. Using spin configuration data, we reconstruct all nearest-neighbor effective Ising coupling energies using maximum likelihood estimation. To assess inference reliability without ground-truth model parameters, we propose to use the convergence of the standard deviation of the estimated couplings as a practical, ground-truth-free criterion, and validate its reliability using simulation data with known parameters. The extracted spatially resolved couplings reveal how each control protocol influences the sign, magnitude, statistical distribution, and spatial arrangement of the microscopic coupling parameters: isotropic compression strengthens antiferromagnetic couplings and enhances quenched disorder; shear deformation generates direction-dependent anisotropic couplings; and increased interparticle attraction drives a crossover from antiferromagnetic to paramagnetic and then to ferromagnetic couplings. This work establishes a practical inference framework for estimating effective model parameters of colloidal artificial spin lattices.