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2604.09221 2026-04-13 math.AG cs.CG math.CO

Fast Isotopy Computation for T-Curves

Zoe Geiselmann, Michael Joswig, Lars Kastner, Konrad Mundinger, Sebastian Pokutta, Christoph Spiegel, Marcel Wack, Max Zimmer

Comments 9 pages, 3 figures

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英文摘要

A T-curve of degree $d$ is given by a regular unimodular triangulation of $d \cdot Δ_2$ together with a sign distribution on its lattice points. By Viro's Patchworking Theorem, this determines the ambient isotopy type (a.k.a. real scheme) of a smooth real plane projective algebraic curve of the same degree. We present a near-quadratic time algorithm for extracting that isotopy type from the triangulation and the signs. Through a GPU-accelerated implementation, this allows one to compute billions of real schemes per second, enabling exhaustive enumeration at scale. This algorithm was essential for our recent construction of all 121 real schemes of degree seven by T-curves.

2604.09219 2026-04-13 quant-ph

Thermodynamical aspects of optically pumped dense atomic medium

A. F. Sousa, C. H. S. Vieira, H. M. Florez

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英文摘要

Optically Pumped Magnetometers use light to drive an atomic vapor into a Non-Equilibrium Steady State for sensing. This kind of state is achieved when spin-exchange collisions, together with optical pumping, dominate the relaxation dynamics, redistributing the atomic populations and thereby shaping the steady-state configuration. Despite the rapid advancement of atomic magnetometer technology, a comprehensive thermodynamic analysis of the state preparation is largely unexplored. We apply a thermodynamic framework to alkali atoms in a vapor cell, modeling their interactions with the pump laser and their relaxation via spin-exchange and spin-destruction collisions. We analyze how the pump rate and light polarization determine the non-equilibrium steady state, quantifying irreversibility via entropy production, assessing useful energy via ergotropy, and defining the spin-polarization efficiency. Finally, we establish a connection between metrological performance and the Quantum Fisher Information (QFI), demonstrating that a higher thermodynamic efficiency directly translates into an improved fundamental bound on magnetometer sensitivity. These results provide insights for optimizing state preparation in quantum sensors.

2604.09218 2026-04-13 math.OC

A priority-driven constructive heuristic for assigning and scheduling spontaneous volunteers in disaster response

Martina Sperling

Comments 33 pages, 7 figures. Computational study with up to 10,000 volunteers and 3,200 instances

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Large-scale disaster response operations frequently involve spontaneous volunteers who arrive independently at disaster sites and must be coordinated under severe time pressure. Assigning such volunteers to relief activities constitutes a complex workforce assignment and scheduling problem with heterogeneous capabilities, dynamic arrivals, and operational constraints. Recent work formulated the spontaneous volunteer coordination problem (SVCP) as a lexicographic multi-objective mixed-integer optimization model. However, solving this model to optimality becomes computationally challenging in large-scale and rolling-horizon disaster response settings. This paper proposes a problem-specific constructive heuristic for the SVCP that explicitly leverages the lexicographic objective hierarchy, capability scarcity among volunteers, and workload balancing across activities. A large-scale computational study based on empirically grounded disaster response scenarios derived from the 2013 flood response in Halle (Germany) evaluates the proposed approach. Across 3200 simulated instances with up to 10000 volunteers and more than 4000 activity-time combinations, the heuristic closely approximates optimal solutions for the primary objectives while achieving a median runtime speedup of approximately 28x. Whereas the exact solver exceeds operational decision time limits in more than 60% of instances, the heuristic consistently produces solutions within minutes, enabling real-time decision support for spontaneous volunteer coordination.

2604.09217 2026-04-13 cond-mat.mtrl-sci physics.chem-ph

Linking Calendar and Cycle Ageing in Lithium-Ion Batteries through Consistent Parameterisation of an Electrochemical-Thermal-Degradation Model

Ganesh Madabattula

Comments 40 pages

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英文摘要

Parameterisation of coupled degradation mechanisms in lithium-ion batteries is a major challenge. Interactions between the mechanisms depend on usage conditions: C-rate, rest state-of-charge (SoC), depth-of-discharge (DoD) and temperature. This work presents a framework to consistently parameterise key degradation modes--solid-electrolyte interphase (SEI) growth, lithium plating, and active material loss in both electrodes--using insights derived from degradation mode analysis data. The work predicts capacity fade trajectories of a NMC-based lithium-ion cell under both calendar and combined calendar-cyclic ageing, using a P2D electrochemical-thermal-degradation model. The work predicts state-of-health (SoH), remaining-useful-life (RUL) and internal degradation modes of the cell--under 81 combinations of temperature (10$^o$C, 25$^o$C, 40$^o$C), C-rate (0.1 C, 0.3 C and 1.0 C), rest SoC (10%, 60%, and 100%) and DoD (50%, 70%, and 90%)--using PyBaMM. The predicted cycle-life varies between 0.8 to 14 years to reach 75% of SoH. The work provides mechanistic insights into competing effects between calendar and cyclic ageing, during cycling. The model demonstrates sub-linear, linear, and sup-linear/accelerated capacity fade based on the usage conditions. The simulated dataset for all the cases is made available.

2604.09216 2026-04-13 math.AG

Surfaces with canonical map of odd degree

Margarida Mendes Lopes, Rita Pardini, Roberto Pignatelli

Comments 28 pages, comments are welcome

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英文摘要

Let $S$ be a smooth complex minimal surface of general type with $p_g:=h^0(K_S)\ge 4$ whose canonical map is generically finite of odd degree $d>1$ onto a surface $Σ$. We assume that the general canonical curve of $S$ is smooth and that $Σ$ is ruled by lines, and we prove: - $p_g\le d+2$ - $Σ$ is a cone over the rational normal curve of degree $p_g-2$ in ${\mathbb P}^{p_g-1}$ - $p_g=d+2$ can occur only for $d=3,9,11$. As a byproduct, we refine previous results by Beauville and Xiao by proving that if one drops the assumption that $Σ$ is ruled by lines then $d\le 5$ if $p_g\ge 112$. The case $d=3$ being completely classified by the first two named authors, we focus on $d=5$, showing that $p_g\le 5$ and that for $p_g=5$ the surface $S$ has a pencil $|C|$ with $C^2=1$ and $K_SC=5$. These results suggest that the answer to the question whether the surfaces with canonical map of odd degree $d>1$ have bounded invariants could be positive, in sharp contrast with the case of even degree.

2604.09215 2026-04-13 cs.CE

Phase-Field Peridynamics

Kai Partmann, Christian Wieners, Michael Ortiz, Kerstin Weinberg

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Peridynamics formulates the balance of linear momentum as an integro-differential equation, making it naturally suited for fracture modeling without special treatment of discontinuities. The bond-associated correspondence formulation provides a highly accurate peridynamic framework by computing bond-wise deformation gradients that are free of zero-energy modes and yield accurate results even near boundaries. However, the traditional fracture approach based on irreversible bond deletion can compromise this formulation, as the progressive removal of bonds degrades the nonlocal approximation of the deformation gradient and can lead to numerical instabilities. In this work, a novel phase-field peridynamics approach is introduced that avoids these instabilities. Instead of deleting bonds, the energetic contribution of each bond is continuously degraded through a bond phase-field parameter, while a separate kinematic degradation function preserves the accuracy of the nonlocal deformation gradient approximation. The normalization constant ensuring thermodynamic consistency with Griffith's fracture theory is derived analytically for general spherical kernel functions as a ratio of two one-dimensional integrals. Numerical examples including mode I and mode II fracture, the boundary tension test with different kernel functions and horizon ratios, and the Kalthoff-Winkler experiment demonstrate the stability, accuracy, and consistency of the proposed approach.

2604.09211 2026-04-13 astro-ph.HE astro-ph.GA astro-ph.SR

The evolution of the mid-infrared spectrum of SN 1987A observed with the JWST/MIRI-MRS

P. J. Kavanagh, M. J. Barlow, C. Fransson, J. Larsson, M. Matsuura, B. Sargent, O. C. Jones, M. Meixner, R. Wesson, J. A. D. L. Blommaert, P. Bouchet, A. Coulais, R. Gastaud, R. D. Gehrz, N. Habel, A. S. Hirschauer, J. Jaspers, R. P. Kirschner, L. Lenkic, O. Nayak, S. Rosu, T. Temim

Comments 35 pages, 20 figures, accepted for publication in ApJ

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Supernova (SN) 1987A provides a unique laboratory for investigating many aspects of SN physics and evolution. An observation at Day 12927 (35.4 yr) since the explosion with the Mid-Infrared Instrument (MIRI) Medium Resolution Spectrometer (MRS) on the James Webb Space Telescope (JWST) provided the first spatially resolved spectroscopic study of SN 1987A in the mid-IR, yielding insights into the evolution of dust, the ejecta, the equatorial ring (ER), and shocks in the system. Here we present a second epoch with MIRI/MRS at Day 13311 (36.4 yr) allowing the mid-IR spatially resolved spectroscopic temporal evolution of SN 1987A to be probed for the first time. Analysis of the ER-dominated dust continuum showed little evolution between Days 12927 and 13311. However, a spatial analysis reveals the inner ER to be fading while the outermost regions are brightening. Broad ejecta emission lines detected at Day 12927 are evolving rapidly, driven by the recent onset of the ejecta/equatorial ring interaction in the northeast and southwest of the ER. Most lines from the ER show no change during the 384 days between the epochs, though some such as [Ne II] and [Ar II] have faded. We identify mid-IR H2 emission associated with the ejecta for the first time. Using the near- and mid-IR [Fe II] lines as density and temperature diagnostics of the ejecta in the interaction region we find it likely that the dense inner Fe-rich ejecta has now reached the reverse shock. Continued monitoring of SN 1987A is essential to observe the evolving ejecta/ER interaction and dust components.

2604.09209 2026-04-13 astro-ph.GA

An automated method for planetary nebula detection with SIGNALS: first applications to NGC 4214 and NGC 4449

Nancy Yang, Johanna Hartke, Martin Bureau, Chiara Spiniello, Louis-Simon Guité, Guy Flint, Magda Arnaboldi, Ana Inés Ennis, R. Pierre Martin, Thomas Martin, Carmelle Robert, Laurie Rousseau-Nepton, Lucas M. Valenzuela, Sébastien Vicens-Mouret

Comments 21 pages, 19 figures, Accepted for publication in MNRAS

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Utilising the optical imaging Fourier transform spectrograph SITELLE, the Star-formation, Ionized Gas and Nebular Abundances Legacy Survey (SIGNALS) is designed to study the connection between star-forming regions and their environments. Targeting $31$ local star-forming galaxies, its data products also lend themselves to planetary nebula (PN) surveys. We present here a new pipeline to find PNe using automated emission-line diagnostics and morphology tests, that is able to distinguish PNe from contaminants with an accuracy similar to that of past visual methods. We also perform thorough completeness tests using mock PNe inserted into the data cubes with full spectra. We apply these tools to a pilot sample of two dwarf irregular galaxies from the SIGNALS survey, NGC 4214 and NGC 4449, with other galaxies to follow. For these two galaxies, we identify $25$ PNe (including $6$ new discoveries) and $23$ PNe (including $13$ new discoveries), respectively, and calculate PN luminosity function distances of $3.09^{+0.25}_{-0.46}$ and $3.91^{+0.33}_{-0.52}$ Mpc, respectively, the latter consistent with previous estimates. We also calculate the bolometric PN specific frequency of our galaxies ($α_\mathrm{bol}$), as well as a newly defined $V$-band PN specific frequency ($α_\mathrm{V}$) based solely on the galaxies' total luminosities in that band.

2604.09207 2026-04-13 hep-ph math-ph math.MP

A Levinson's theorem for particle form factors

Francesco Rosini, Simone Pacetti

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We present and demonstrate a version of Levinson's theorem especially dedicated to the asymptotic behavior of form factor phases. Indeed, as required by analyticity, form factors are multi-valued complex functions of a square four-momentum defined in the complex plane with a cut along the positive real axis. Their phases evaluated on the upper edge of this cut, i.e., on the time-like region, tend asymptotically to integer multiples of $π$ radians. The Levinson's theorem establishes a univocal relation between such multiples and properties of form factors related to the dynamics of the electromagnetic interaction of the corresponding hadrons.

2604.09205 2026-04-13 astro-ph.SR

Tracing the s-Process: Spectroscopic Insights into Chemical Abundances in O- and C-rich Evolved Stars

Sophie Van Eck, Carlos Abia, Inma Dominguez

Comments 36 pages, 7 figures, accepted in European Physical Journal A, Topical Collection dedicated to Roberto Gallino

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Oxygen and carbon-rich AGB stars - and objects directly polluted by them - are excellent laboratories to investigate the nucleosynthesis and mixing processes occurring during the later phases of the of low- and intermediate-mass star evolution. The determination of the abundances of several s-elements is a key tool for constraining theoretical AGB models. This contribution discusses the main results, recent advances, and current problems on this subject.

2604.09204 2026-04-13 cond-mat.mtrl-sci

Phase Equilibria of the Al-Ti-Nb-Zr-Ta System

Jiří Kozlík, František Lukáč, Mariano Casas-Luna, Jozef Veselý, Eliška Jača, Kateřina Ficková, Stanislav Šašek, Kristína Bartha, Adam Strnad, Tomáš Chráska, Josef Stráský

Comments 15 figures, 2 tables, 5 supplementary material sections

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Phase equilibria in the Al-Ti-Nb-Zr-Ta refractory complex concentrated alloy system were investigated using a high throughput experimental approach. A pseudo-ternary section of the quinary compositional space was prepared by a honeycomb type powder metallurgy design, consolidated by spark plasma sintering and subsequently homogenized at 1400 °C for 168 h. Phase constitution and chemical partitioning were characterized by SEM/EDS, XRD, EBSD, and TEM, supported by a custom EDS phase clustering workflow. Equilibrium microstructures consisting primarily of BCC, B2, and secondary phases were identified across the sampled compositions, with nanoscale precipitates forming in Zr and Ta rich regions. Measured phase compositions were compared with CALPHAD predictions, revealing both agreements and systematic deviations linked to CALPHAD database limitations. The results provide new experimental insight into phase stability and microstructural trends in Al-Ti-Nb-Zr-Ta alloys and demonstrate the effectiveness of high throughput combinatorial approaches for mapping complex multicomponent systems.

2604.09203 2026-04-13 physics.chem-ph

Experimental proof of strong $Π$-$Σ$ mixing in the Renner-Teller and Pseudo-Jahn-Teller affected CCH$^+$ ($^3Π$) ion

Kim Steenbakkers, P. Bryan Changala, Weslley G. D. P. Silva, John F. Stanton, Filippo Lipparini, Jürgen Gauss, Oskar Asvany, Gerrit C. Groenenboom, Britta Redlich, Stephan Schlemmer, Sandra Brünken

Comments 24 pages, 5 figures. Supplementary information can be found on the journal webpage. In press in The Journal of Physical Chemistry Letters

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The ethynyl radical cation, CCH$^+$ ($^3Π$), offers a unique system for fundamental spectroscopic studies of non-adiabatic effects due to its open-shell linear structure and the presence of a low-lying $^3Σ^-$ state, which induces notable perturbations in the (ro-)vibrational spectrum. To probe these effects, we recorded the broadband vibrational spectrum of CCH$^+$ from 350-3450 cm$^{-1}$ using leak-out spectroscopy. The spectrum reveals a complex splitting pattern in the CCH bending mode, attributed to Renner-Teller and pseudo-Jahn-Teller coupling effects between the $^3 Π$ and $^3 Σ^-$ electronic states. A three-state diabatic model, validated here against high-resolution IR data of the CH stretching mode, facilitated assignments within the broadband infrared (IR) spectrum, including an additional $Π$ vibronic feature observed in the aforementioned high-resolution spectrum. Our results highlight a pronounced sensitivity of the splitting pattern to the $Π$-$Σ$ energy gap, with couplings so large that even the zero-point vibrational motion of the bending vibration is sufficient to disrupt the vibronic structure of this ion. This compact ion, with strong coupling effects and high-quality spectroscopic data, serves as an exemplary system for evaluating non-adiabatic models.

2604.09193 2026-04-13 cond-mat.mtrl-sci

The hidden ferroelectric chiral ground state of silver niobate

Safari Amisi, Fernando Gómez-Ortiz, Eric Bousquet, Philippe Ghosez

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Silver niobate is a conventional perovskite oxide compound, known to exhibit a rich polymorphism. Although often classified as antiferroelectric, its low-temperature structure remains unclear. Here, first-principles calculations reveal a previously overlooked and unusual rhombohedral ferroelectric phase with $R3$ symmetry that emerges as the thermodynamic ground state despite its close energetic competition among previously proposed structures. Remarkably, this phase is structurally chiral, with chirality emerging improperly from the coupling between polarization and in-phase rotations of the oxygen octahedra along [111], producing a ferri-chiral state with incomplete cancellation of local chiral motifs. As a consequence, the phase exhibits significant natural optical activity comparable to that of quartz. Although energetically favored, its experimental observation may be hindered by kinetic limitations, potentially contributing to the ongoing controversy surrounding the low-temperature structure of silver niobate.

2604.09192 2026-04-13 quant-ph

Order structure and signalling in higher order quantum maps

Anna Jenčová

Comments 31 pages, a continuation of arxiv:2411.09256. Comments welcome

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We study the signalling structure of higher order quantum maps from an order-theoretic perspective, building on the combinatorial characterization of higher order types by Bisio and Perinotti. We have shown in a previous work arxiv:2411.09256 that types are represented by boolean functions called type functions, and that each such function is characterized by a related structure poset. We characterize the distributive lattice generated by all type functions with fixed indices of input and output systems - whose elements we call regular subtypes - by a monotonicity condition. Unlike the set of type functions, the lattice of regular subtypes is closed under the one-way signalling product, moreover, it is generated by a specific family of causally ordered types. We then study signalling relations for maps belonging to a regular subtype, showing that the no-signalling conditions between an input and an output system are determined by a single evaluation of the corresponding function. For higher order types specifically, we show that all signalling relations can be read off directly from the structure poset via a rank parity condition. Finally, we study relations between the structure poset of a type and its normal forms, that is, expressions of the type in terms of causally ordered types. We illustrate construction of normal forms on some examples, demonstrating the possibility that the normal form can be systematically derived from maximal chains of the poset and signalling relations between them.

2604.09191 2026-04-13 physics.flu-dyn

Role of particle volume fraction on particulate suspension droplet evolution, transition and Hysteresis

Kishorkumar Sarva

Comments 16 pages, 9 figures

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We study the transitional dynamics of the non-Brownian particulate Newtonian liquid jet for different particle volume fractions ($ϕ$). We focus on the influence of particle volume fraction on the critical inflow velocity at which the dripping-jetting (i.e., dripping to jetting and jetting to dripping) transition occurs for the ratio of the nozzle diameter to the particle diameter ($D_n/D_p$=20). The experiments were conducted by increasing (forward sweep) and decreasing (reverse sweep) the flow rate. These experiments were repeated for different volume fractions. We observe, with an increase in particle volume fraction, the transition from the dripping to the jetting regime occurs through a chaotic dripping regime. With an increase in the particle volume fraction, the jetting regime has occurred at early flow rates during dripping to jetting transition (in forward sweep), and the jetting to dripping transition (reverse sweep) occurred at a lower flow rate than the forward sweep. The particle volume fraction impacts the hysteresis observed for the Newtonian fluid. Due to the changes in the critical flow rate where transition occur, the widening of the hysteresis loop of flow rate with the pinchoff length is observed. The transition from dripping to jetting is observed to have the recurrent escape of the pinchoff mechanism as the jet length changes, influencing the droplet size distribution. The frequency of droplet pinchoff and droplet size have decreased as the particle volume fraction has increased. As the particle volume fraction increases, the size distribution between the dripping and jetting regimes decreases.

2604.09190 2026-04-13 cond-mat.mtrl-sci

The effect of pressure in the crystal and magnetic structure of FeWO4

Oscar Fabelo, Javier Gonzalez-Platas, Stanislav Savvin, Pablo Botella, Daniel Errandonea

Comments 22 pages, 9 figures, 2 tables

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Journal ref
J. Appl. Phys. 136, 175901 (2024)
英文摘要

The temperature dependence of the structural and magnetic properties of wolframite-type FeWO4 were studied in situ by high pressure neutron diffraction. Neutron diffraction measurements were performed at the XtremeD instrument at the Institut Laue Langevin up to a maximum pressure of 8.7(4) GPa and a minimum temperature of 30.0(5) K. The diffraction data were analyzed via Rietveld refinements. We found that despite of producing a contraction of 5% of the volume, the maximum pressure applied in this study does not modify the Shubnikov space group below magnetic order. However, the orientation of magnetic moments and the Néel temperature, are slightly modified with the pressure, which is expected according to the preexistent understanding of magnetism in wolframites. We also determined a pressure-volume equation of state of FeWO4 at 300 K, which is compared with previous X-ray diffraction studies and density-functional theory calculations.

2604.09187 2026-04-13 econ.GN physics.soc-ph q-fin.EC q-fin.GN

The Geoeconomics of Venture Capital An Economic Complexity Approach to Emerging Technological Sovereignty

Benjamin Leroy, Davi Marim, El Ghali Benjelloun, Arthur Rozan Debeaurain, Jean-Michel Dalle

Comments 12 pages, 2 figures

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We explore a quantitative approach to emerging technological sovereignty and geoeconomic power by assessing the relative positioning of countries with economic complexity methods applied to the structure of national venture-capital (VC) portfolios and their associated Revealed Venture Advantage (RVA) metrics. Using Crunchbase firm- and deal-level data, we map venture-backed startups to 18 emerging technology domains via a probabilistic multi-label large-language-model classifier, and construct an RVA-based country-technology specialization matrix for the 17 countries with the highest aggregate VC funding. From this matrix, we derive two eigenvector-based measures: a Geoeconomic Complexity Index (GCI) that ranks countries by the composition of their venture specializations, and an Emerging Technology Geoeconomic Complexity Index (ETGCI) that ranks domains by the extent to which specialization is concentrated among high-GCI countries. Empirically, Cloud Computing, Cybersecurity Tools, and Medtech exhibit the highest ETGCI values, reflecting concentration of specialization in a small set of leading countries. The United States and Israel consistently occupy a marked "high-diversity/low-ubiquity" position and lead the GCI ranking, followed by China, France, Japan, and Germany; both country and domain rankings are stable from 2021-2024. Finally, relatedness-based simulations identify, when it exists, for each country the Simplest Single Sovereignty Enhancing Technology (SSSET), i.e., the most feasible single new technological direction associated with the largest expected improvement in relative geoeconomic positioning.

2604.09184 2026-04-13 astro-ph.EP astro-ph.IM

Terrestrial planet formation in the era of GPU computing

Simon L. Grimm, Joachim G. Stadel

Comments Chapter accepted for publication in the NCCR PlanetS Legacy Book: Benz, W. et al. (Eds), The National Center for Competence in Research, PlanetS: A Swiss-wide network expanding planetary sciences. Springer (2026)

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In this chapter, we summarize the underlying numerical methods needed for efficient $N$-body integration of planetary systems. We discuss how symplectic integrators have been developed to tackle the complementary problems of long-term orbital integration and short-term collisional interactions. The public code GENGA, a parallel GPU/CPU planet formation and orbital dynamics simulation code, was developed to unify these methods and take full advantage of the newest available computing hardware. We present state-of-the-art N-body simulations performed with GENGA in a comparative study regarding the basic properties that emerge during the late stages of the terrestrial planet formation process. We show that in modern N-body simulations the commonly used acceleration factor f, used to speed up the collisional growth of planets in simulations, should be avoided since it can lead to distorted chemical composition of the planets. We make a detailed comparison of low to high-resolution simulations, showing that the formation time scale depends on the size of the initial planetesimals. These simulations also show that terrestrial planets can form resonant chains without the need of orbital migration due to gas effects.

2604.09183 2026-04-13 math.NA cs.NA physics.comp-ph

Restoring Convergence Order in Explicit Runge-Kutta Integration of Hyperbolic PDE with Time-Dependent Boundary Conditions

Giorgio Maria Cavallazzi, Miguel Pérez Cuadrado, Alfredo Pinelli

Comments 22 pages, 13 figures

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Explicit Runge-Kutta (RK) integration of hyperbolic initial-boundary value problems with time-dependent Dirichlet data often displays order reduction: the observed convergence order falls below the nominal order because the stage structure interacts with asymmetric near-boundary spatial closures. This paper develops a purely spatial remedy that preserves the time integrator while redesigning only the first two boundary-adjacent derivative operators. For an arbitrary explicit $s$-stage RK method applied to linear advection, the one-step truncation error at the boundary-adjacent nodes is shown to admit a tableau-dependent decomposition whose cancellation yields explicit algebraic conditions on the boundary weights. A solvability coefficient $R(\mathbf{b},\mathbf{c},A)$ determines whether a spatial compensation mechanism exists; the result is specialised to SSP-RK3, for which closed-form conditions are derived. Constrained differential evolution then identifies 5-point closures that, coupled to a 5th-order upwind interior stencil, recover third-order convergence from the degraded second-order behaviour of classical Taylor closures. A stability-aware variant augments the optimisation with an eigenvalue penalty, exposing the trade-off between order recovery and CFL robustness. Validation covers linear advection, manufactured-solution Burgers flow, and dimensionally split two-dimensional advection. The analysis clarifies why weak-stage-order temporal fixes do not resolve the finite-difference boundary problem, and indicates how the framework extends to non-uniform meshes.

2604.09182 2026-04-13 astro-ph.IM astro-ph.HE

Fast and Scalable Production of Stacked Prism X-ray Lenses for Astrophysics Using Two-Photon Polymerization

Filip af Malmborg, Chloé Delmotte, Kian Shaker, Mark Pearce

Comments 33 pages, 16 figures

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Journal ref
Journal of Astronomical Telescopes, Instruments, and Systems, Vol. 12, Issue 1, 015002 (January 2026)
英文摘要

Stacked prism lenses (SPLs) are a type of refractive X-ray optics currently under development with the potential to greatly improve on current X-ray telescope optics in terms of focal length, angular resolution, efficiency and scalability. For this work, SPLs are manufactured using two-photon polymerization (2PP), with production being significantly faster and with higher geometric fidelity than previous methods. Preliminary laboratory tests show improved efficiency compared to previous manufacturing methods and promising optical capabilities. Two-photon polymerization is shown to be a reliable method for producing SPLs, and when challenges around printing time and assembly are addressed, the path towards an SPL X-ray telescope lies open.

2604.09180 2026-04-13 cond-mat.stat-mech cond-mat.quant-gas cond-mat.str-el quant-ph

Eigenstate entanglement entropy in Bose-Hubbard models

G. Medoš, L. Vidmar

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While the eigenstate entanglement entropy has been extensively studied for fermionic systems, much less is known about bosonic systems. Here, we study the entanglement entropy of mid-spectrum eigenstates of Bose-Hubbard models, focusing on weakly disordered models with and without particle-number conservation, and contrasting them with the translationally-invariant model. We analyze the volume-law and O(1) contributions to the entanglement entropy via the averages over mid-spectrum eigenstates and the corresponding distributions. We derive the volume-law coefficient of the entanglement entropy by generalizing the mean-field approach from [Phys. Rev. Lett. 119, 220603 (2017)] to many-body systems with a tunable local bosonic cutoff, which agrees with previous analytical and numerical results from [Phys. Rev. B 110, 235154 (2024)]. We show that the volume-law contribution to the entanglement entropy does not change upon breaking translational invariance via on-site disorder. We then numerically study the role of the subleading O(1) contribution to the entanglement entropy. We find that, in the particle-number conserving case, it exhibits a nontrivial dependence on the particle-number density and the local bosonic cutoff, while without particle-number conservation, results suggest the emergence of a universal O(1) contribution beyond the random pure state predictions.

2604.09179 2026-04-13 eess.SY cs.SY math.DS

Discrete-Time Model of a Two-Speed PowerShift suitable for Real-Time Control and Simulation

Riccardo Morselli, Davide Tebaldi, Roberto Zanasi

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In this paper, a new discrete-time approach to model the clutches engagement/disengagement in a two-speed powershift is proposed. The core idea is the development of a model for the computation of the exact torque needed to achieve the clutches engagement, including both the cases of single clutch engagement and of simultaneous clutch engagement (full lock condition). Based on this, the control logic for the clutches engagement and disengagement phases is also developed. The advantages in terms of real-time applicability with respect to the continuous-time version are shown through extensive simulation results.

2604.09178 2026-04-13 cond-mat.mes-hall cond-mat.mtrl-sci

Topology-constrained spin-wave modes of asymmetric antibimerons and their clusters

Pavel A. Vorobyev, Daichi Kurebayashi, Oleg A. Tretiakov

Comments 11 pages, 6 figures

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Collective modes are a defining signature of coupled degrees of freedom, forming a bridge between understanding of interactions in condensed-matter systems and emergent functionality. Topological magnetic textures provide a natural platform to realize and control such collective modes at the nanoscale. Here we theoretically identify and characterize low-energy collective spin-wave excitations of isolated asymmetric antibimerons and their clusters in ultrathin ferromagnetic films. We demonstrate that an isolated asymmetric antibimeron supports a discrete spectrum of localized modes, reflecting its internal degrees of freedom. When multiple asymmetric antibimerons form a cluster, inter-texture coupling leads to the splitting of these modes into $N$-fold multiplets, where $N$ denotes the number of asymmetric antibimerons. To rationalize these findings, we introduce an effective coupled-oscillator model based on meron pairs that captures the essential collective dynamics of the system. This emergent classical mechanics description reveals that the motion of asymmetric antibimeron clusters can be understood in terms of well-defined normal modes governed by topology-constrained particle-like degrees of freedom. These results establish coupled asymmetric antibimerons as a tunable platform for spin-wave based nano-oscillators, whose normal-mode spectrum is controllable through cluster size, thus providing a programmable set of low-lying resonances for these nano-oscillators.

2604.09177 2026-04-13 astro-ph.GA

The Cliff: A Metal-Poor Little Red Dot Hosting an Overmassive Black Hole at $z = 3.55$

Lucy R. Ivey, Francesco D'Eugenio, Roberto Maiolino, Yuki Isobe, Ignas Juodžbalis, Sophie Koudmani, Michele Perna, Saiyang Zhang, Volker Bromm, Andrew J. Bunker, Stefano Carniani, Andrew C. Fabian, Kohei Inayoshi, Xihan Ji, Gareth C. Jones, Boyuan Liu, Robert Pascalau, Pierluigi Rinaldi, Brant Robertson, Jan Scholtz, Sandro Tacchella

Comments 20 pages, 17 figures. Submitted to MNRAS

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JWST has revealed a large population of massive black holes (BHs) in the early Universe with unusual properties which mark them as distinct from low-redshift active galactic nuclei. Such findings have prompted the development of new models of BH formation and growth, and of their co-evolution with host galaxies. Linking the gas-phase metallicity of BH environments to seed masses is key to understanding which evolutionary pathways could explain the population of JWST-discovered BHs. We present new high-resolution JWST NIRSpec/IFU observations covering the rest-frame optical emission lines of a Little Red Dot (LRD) at $z=3.55$, known as The Cliff, from the `Red Unknowns: Bright Infrared Extragalactic Survey' (RUBIES). We find evidence for low metallicity ($Z=0.017\pm0.004 \ Z_\odot$) based on the low narrow-line [OIII]$\lambda5007$/H$β$ ratio, supported by the non-detection of low-ionisation emission lines such as [OII]$λ\lambda3727,3729$ and [NII]$λ\lambda6548,6583$. We find that the observed properties of The Cliff, including its overmassive BH, can be reproduced by some simulations of black hole growth and evolution down to $z\sim3.5$. However, these simulation runs require high seed masses ($10^4 - 10^5\ M_\odot$) and appear as rarely in the simulation volume as in the RUBIES survey volume over redshifts $3<z<4$, highlighting the unusual nature of The Cliff. Future simulations and numerical models will help to uncover how such a metal poor system managed to develop a massive black hole and persist to such low redshift.

2604.09176 2026-04-13 math.CO

Sharp threshold for reconstructing points on the line

Georgii Zakharov

Comments 47 pages, 8 figures

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英文摘要

For a set of $n$ points $V \subseteq \mathbb{R}$ let $G(V, p)$ be the random graph on $V$ where each possible edge is present independently with probability $p$. We call a subset $U \subseteq V$ {\emph {reconstructible}} if every injection $φ:V\to \mathbb{R}$ that preserves the distances along the edges of $G(V, p)$ also preserves all pairwise distances in $U$. How large is the size $\mathsf{R}$ of a largest reconstructible subset? Girão, Illingworth, Michel, Powierski and Scott conjectured that the answer is linear whp when $p = (1+\varepsilon)/n$ for every $\varepsilon > 0$. In this paper, we show that for every $\varepsilon>0$ whp there exists a reconstructible subset $U$ of the largest component $\mathcal{C}$ of the 2-core satisfying $|U| = |V(\mathcal{C})|(1-o(1))$, proving a stronger form of the conjecture. The bound is asymptotically best possible, since for $V \subseteq \mathbb{R}$ linearly independent over $\mathbb{Q}$ it is straightforward to verify that $\mathsf{R} \leq \max(2, |V(\mathcal{C})|)$. Furthermore, we extend these results to every $\varepsilon:= \varepsilon(n)$ satisfying $\varepsilon = ω(1/\ln n)$.

2604.09172 2026-04-13 cond-mat.supr-con

Nonmonotonic Evolution of the Superconducting Transition Temperature and Robust Multigap Extended s-wave + s-wave Pairing in Zn-Substituted FeSe Single Crystals

Han-Shu Xu, Changhao Ding, Guanyin Gao, Xin Zhang, Xinyu Yin, Xucai Kan, Jiaping Hu, Wen Xie, Wensen Wei, Yuxiao Hou, Keyu An, Haoxiang Li, Kaibin Tang, Yu-Yan Han

Comments 16 pages,6 figures

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英文摘要

We report a systematic study of superconductivity on Fe1-xZnxSe single crystals synthesized over a broad Zn doping range (x = 0-0.023). High-quality single crystals across all compositions range exhibit superconducting transitions, while the transition temperature Tc shows a pronounced nonmonotonic dependence on Zn doping concentration, indicating that the underlying mechanism govering Tc its evolution cannot be explained solely by simple impurity pair breaking alone. Magnetization and transport measurements confirm the bulk behavior of superconductivity and reveal enhanced scattering effects with Zn doping. Low-temperature specific heat is consistently described by a two-gap scenario composed of an isotropic s-wave gap and an anisotropic extended s-wave gap, whereas single-gap and alternative pairing symmetries fail to describe the data. The nearly unchanged relative weights of the two gap components suggest the weak interband scattering induced by Zn substitution, thereby preserving multiband superconductivity. These results demonstrate the robustness of multigap superconductivity in FeSe and impose stringent constraints on candidate pairing mechanisms, highlighting the role of multiband electronic structure and anisotropic gap formation.

2604.09171 2026-04-13 cs.SE

SHIFT: Sigmoid-Based Heuristic Invertible Fitness-Landscape Transformation for Accelerating SBST

Jeongjin Han, Seunghoon Sim, Jian Lee, Seongyoon Park

Comments 32 pages, 17 figures. Code available at https://github.com/Jeong-jin-Han/SHIFT-SBST

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英文摘要

Search-Based Software Testing (SBST) automates test input generation but is frequently hindered by challenging fitness landscapes characterized by numerous deceptive local optima that impede search progress, as well as extended plateaus where informative fitness signals are scarce. To address this bottleneck, we propose SHIFT (Sigmoid-Based Heuristic Invertible Fitness-Landscape Transformation for Accelerating SBST), a method designed to compress local landscapes and facilitate escape from stagnant regions without altering global semantics. By systematically contracting dense regions where search points cluster, the approach preserves mapping invertibility while enabling optimization algorithms to traverse more effectively toward global coverage with the same step size. When evaluated against established baselines, including pure hill climbing and genetic algorithms, under a normalized experimental protocol, the proposed technique yields consistent improvements in convergence speed and search efficiency. These results demonstrate that sigmoid compression constitutes a lightweight yet effective mechanism for achieving more reliable coverage discovery in complex testing environments.

2604.09170 2026-04-13 hep-th astro-ph.CO gr-qc

Covariant scalar-tensor theories beyond second derivatives

Mohammad Ali Gorji, Pavel Petrov, Karim Noui

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英文摘要

We propose a covariant, gauge-independent construction of foliation-based scalar-tensor theories, yielding diffeomorphism-invariant operators involving only gradients on the hypersurfaces where the scalar field is constant, assumed to be spacelike. This defines a basis of independent invariants up to four derivatives of $ϕ$, including the first nontrivial parity-odd pseudoscalar at this order, with a straightforward extension to higher derivatives. Our framework goes beyond degenerate higher-order scalar-tensor (DHOST) theories and provides a nonlinear extension of U-DHOST (where $\nabla_μϕ$ is supposed to be timelike) directly in covariant form, without using unitary gauge as a starting point or imposing degeneracy a priori. After minimal coupling to gravity, we analyze the theory through its Hamiltonian constraint structure and linear cosmological perturbations about an FLRW background, and show that it propagates three physical degrees of freedom.

2604.09165 2026-04-13 cs.PL cs.CR cs.LO

A Deductive System for Contract Satisfaction Proofs

Arthur Correnson, Haoyi Zeng, Jana Hofmann

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英文摘要

Hardware-software contracts are abstract specifications of a CPU's leakage behavior. They enable verifying the security of high-level programs against side-channel attacks without having to explicitly reason about the microarchitectural details of the CPU. Using the abstraction powers of a contract requires proving that the targeted CPU satisfies the contract in the sense that the contract over-approximates the CPU's leakage. Besides pen-and-paper reasoning, proving contract satisfaction has been approached mostly from the model-checking perspective, with approaches based on a (semi-)automated search for the necessary invariants. As an alternative, this paper explores how such proofs can be conducted in interactive proof assistants. We start by observing that contract satisfaction is an instance of a more general problem we call relative trace equality, and we introduce relative bisimulation as an associated proof technique. Leveraging recent advances in the field of coinductive proofs, we develop a deductive proof system for relative trace equality. Our system is provably sound and complete, and it enables a modular and incremental proof style. It also features several reasoning principles to simplify proofs by exploiting symmetries and transitivity properties. We formalized our deductive system in the Rocq proof assistant and applied it to two challenging contract satisfaction proofs.

2604.09163 2026-04-13 cs.DB

Evaluating Data Quality Tools: Measurement Capabilities and LLM Integration

Tobias Rehberger, Thomas Hütter, Lisa Ehrlinger, Wolfram Wöß

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英文摘要

High data quality is critical for reliable analytics and operational efficiency. A growing ecosystem of tools has emerged to support data quality management, ranging from lightweight open-source libraries to comprehensive enterprise platforms. This paper evaluates six data quality tools: Great Expectations, Deequ, Evidently, Informatica, Experian, and Ataccama. The evaluation criteria cover rule definition, duplicate detection, metric aggregation, and uncertainty handling, and were derived from real-world use cases of company partners. We further examine to what extent these tools integrate Large Language Models (LLMs). Our findings show that proprietary tools offer more comprehensive measurement features and emerging LLM-based assistance, while open-source tools provide flexibility at the cost of higher implementation effort. Across all tools, LLM integration remains limited to rule creation workflows. Direct data validation through LLMs is not yet supported by any of the evaluated tools.