High Energy Astrophysical Phenomena
Chana: A GPU-Accelerated AMR GRRMHD Code
Tianshu Wang
This paper presents Chana, a GPU-accelerated, block-structured adaptive-mesh code for general relativistic magnetohydrodynamics, multigroup M1
neutrino transport, and dynamical spacetime
evolution using the Z4c formulation. Each physical module uses independently selected spatial discretizations and ghost-zone widths to balance accuracy and computational cost. Stiff radiation-matter interactions are treated implicitly, with Jacobians calculated analytically from the chain-rules. The code is written in C++20 and it uses MPI and Kokkos 5 for distributed-
memory and performance-portable parallelism. The code is validated through a number of GRMHD, radiation transport, and dynamic spacetime tests. For a representative core-collapse
supernova configuration with three
neutrino species and 12 energy groups per species, the code achieves approximately $1.1 \times 10^6$
cell updates per GPU second on NVIDIA A100 GPUs using four-stage RK4 integration. Weak-scaling efficiency remains above 85% up to 256 GPUs on Perlmutter.
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Mathematical Physics · Cross-listed from math.AP
Quantitative Stability Of Aggregation-Diffusion Under Local Attraction
Yunhong Deng
In this note, we establish quantitative stability of aggregation-
diffusion energy for compactly supported data. Our consideration focuses on the degenerate
diffusion with local attraction that are asymptotically flat at infinity, such as Riesz kernels. We characterize the spectrum lower-bound of the Wasserstein Hessian at steady states. Assumptions are kept as minimal as that needed for uniqueness.
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General Relativity and Quantum Cosmology
Gravitational-Wave Propagation in Quadratic Einstein–Cartan–Dirac Gravity: A Conditional Tensor-Sector Analysis
Zhi-Fu Gao, Biao-Peng Li, Na Wang et al. (+4 more)
We study leading tensor propagation in a specified first-order Einstein–Cartan–Dirac theory with the parity-even quadratic torsion invariant $\zeta T_{\lambda\mu\nu}T^{\lambda\mu\nu}$. Eliminating the nondynamical Lorentz connection on the regular algebraic branch gives a metric description containing the Einstein–
Hilbert term, the Dirac action, and a $\zeta$-dependent axial–axial
fermion contact interaction. We evaluate the transverse-traceless (TT) Hessian under an explicit factorized mean-field closure, with vanishing connected-current TT response, vanishing first- and second-order TT response of the factorized current scalar, and zero intrinsic TT anisotropic stress. Under these imposed conditions, the leading two-derivative tensor action has $Q_T=M_{\rm Pl}^{2}$ and $c_T=1$, with no leading dispersion or propagation-induced polarization splitting. These conditions do not follow from isotropy of the one-point axial current, and the present calculation does not derive them from a microscopic fermionic state. The result is therefore conditional and does not establish a general Einstein–Cartan–Dirac no-go
theorem. We identify the connected-current TT response that must be calculated to extend the result beyond this closure. Published NANOGrav summaries are used only to check consistency with the GR-like prediction; no new timing-data likelihood or constraint on $\zeta$ is obtained.
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All authors Zhi-Fu Gao, Biao-Peng Li, Na Wang, Hui Wang, Guo-Qiang Jin, Zhoujian Cao, Luiz C. Garcia de Andrade
Quantum Physics
The parliament of observers - Against the observable axiom of quantum mechanics
Markus Frembs and Andreas Döring
The 'unreasonable effectiveness of mathematics in the natural sciences' may at times give the impression that natural science, especially modern theoretical physics, is all but a formal apparatus. However, a key challenge of physics remains to align everyday notions of experience – be it directly or mediated through instruments of arbitrary sophistication – with their mathematical formalisation. This applies in particular to
quantum theory, arguably the most successful theory of physics ever invented. One of its core assumptions postulates: $Observables\ correspond\ with\ self-adjoint\ operators.$ Here, we argue that already this most basic premise about the
quantum formalism falls apart under careful scrutiny, at least when understood for all observables at once. In other words, we challenge the role of the noncommutative
algebra of bounded operators as an adequate formalisation of the '
algebra of observables', understood as (equivalence classes of) measurement procedures that admit a coherent empirical interpretation.
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Quantum Physics
Resource-Aware Grover Search for Minimum Vertex Cover
Beilei Jiang, Harry Fu, Pavan Krishna Yarlagadda et al. (+3 more)
The Minimum Vertex Cover (MVC) problem is a fundamental NP-hard combinatorial optimization problem with applications in network analysis and resource allocation. Grover's
algorithm provides a quadratic reduction in query complexity for unstructured search, but existing Grover-based MVC formulations can incur substantial
quantum resource overhead due to costly vertex-counting
circuits and complex oracle constructions. We develop and evaluate several encoding and oracle-design strategies for reducing the
qubit count,
circuit depth, and gate complexity of Grover-based MVC search. First, we construct a Dicke-Parallel formulation that restricts the search to fixed-cardinality subsets, eliminating explicit vertex counting, together with a parallel edge-verification oracle that reduces feasibility-checking overhead. We then develop an Edge-Counting formulation that replaces per-edge auxiliary storage with a logarithmic-size counting register, substantially reducing ancillary-
qubit requirements. Finally, we propose an Edge-Centric encoding that represents endpoint selections directly and derives vertex-selection states through incident-edge Boolean operations, enabling more depth-efficient oracle construction. Our resource analysis reveals complementary trade-offs among
qubit width,
circuit depth, gate count, and Grover iteration count. Edge-Counting is particularly attractive under tight
qubit constraints, while Edge-Centric can reduce both
circuit depth and Grover iteration count when the graph has a moderate edge count and sufficient representation multiplicity. Dicke-Parallel provides a more robust choice when such multiplicity is limited or graph density makes the edge-based search space large. These results provide practical guidance for selecting Grover-based MVC formulations according to hardware constraints and graph structure.
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All authors Beilei Jiang, Harry Fu, Pavan Krishna Yarlagadda, Alexander Shan, Yunhe Feng, Song Fu
Quantum Physics
Pauli Error Composition Determines the Multipartite Advantage in Conference Key Agreement
Ryder Carlson, Lochlan Fitzgerald, Kidus Peter et al. (+1 more)
GHZ-based conference key agreement distributes a shared key to $N$ parties in one network use, whereas pairwise BB84 needs $N-1$. The survival of that advantage has been studied against party number, loss, and
topology, but almost always with the channel fixed at depolarizing. Simulating both protocols exactly for $N = 3, 4, 5$ under dephasing, amplitude damping, and depolarizing noise, we find the crossover is set by the channel's Pauli error composition, not its identity: normalized to average infidelity, amplitude damping and depolarizing agree to within about 1% at each group size, while dephasing can tolerate roughly $2.4\times$ more at $N = 3$. We derive a closed-form rate for arbitrary per-party Pauli noise and use it to prove that concentrating a fixed noise budget on one arm is strictly worse than spreading it, and that giving the dealer role to the cleanest arm improves the rate by roughly 18%. One structural fact drives every result: the phase-error term is a product over all $N$ arms, while the bit-error term stays local to a pair.
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All authors Ryder Carlson, Lochlan Fitzgerald, Kidus Peter, Wilson Smith
Cosmology and Nongalactic Astrophysics
Lensing in the Blue IV: The First Weak Gravitational Lensing Maps from the Stratosphere
Sayan Saha, Maya Amit, Jacqueline E. McCleary et al. (+42 more)
The Super-Pressure Balloon-borne Imaging
Telescope (SuperBIT) completed its science flight in April 2023, obtaining imaging data for 30
galaxy clusters. In this work, we present the first weak-
lensing convergence maps from these observations, using six clusters selected from the 30 targets. We construct background-
galaxy catalogs using SuperBIT's three-band photometry and a color-color-based method to separate foreground and background
galaxies, and use the calibrated
galaxy shapes presented in
Lensing in the Blue III to reconstruct the weak-
lensing convergence field using Kaiser-Squires inversion. We compare the convergence signal-to-noise maps for the six clusters with independent tracers, including X-ray emission and red-sequence cluster-member number-density maps. These results demonstrate the first successful weak-
lensing mass mapping with imaging from a sub-orbital astronomical observatory.
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All authors Sayan Saha, Maya Amit, Jacqueline E. McCleary, Georgios N. Vassilakis, Emaad Paracha, Giulia Cerini, Spencer W. Everett, Leila Ohashi, Eric M. Huff, Gavin Leroy, Leo W.H. Fung, Richard Massey, Steven J. Benton, William C. Jones, Thuy Vy T. Luu, Ajay S. Gill, Mohamed M. Shaaban, Philippe Voyer, Adam Field, Adam Aoua, Anthony M. Brown, Paul Clark, Matthew Craigie, Christopher J. Damaren, Tim Eifler, David Harvey, Eric Habjan, John W. Hartley, Bradley Holder, Mathilde Jauzac, David Lagattuta, Jason S.-Y. Leung, Lun Li, Johanna M. Nagy, C. Barth Netterfield, Susan F. Redmond, Jason D. Rhodes, Andrew Robertson, L. Javier Romualdez, Jürgen Schmoll, Ellen Sirks, Sut Ieng Tam, Karuna Tarafdar, André Z. Vitorelli, Alfredo Zenteno
Quantum Physics
Quantum Machine Learning for Few-Shot Impersonation Detection in Digital Account Opening
Javiera Canales, Jose Ortega and Maximiliano Araya
Identity impersonation fraud may emerge only after digital account opening, requiring an early post-onboarding approach based on behavioral and transactional signals observed shortly after activation. Confirmed cases remain rare, creating extreme class imbalance and material operational risk for digital banks. We evaluate
quantum machine learning (QML) against classical one-class methods in this setting using a real 2025 cohort of 3,419 digital account openings from Banco de Creditos e Inversiones (BCI), Chile, including 8 confirmed impersonation-fraud cases (0.23% prevalence). The data were provided through an industry-research collaboration between BCI and CoreDevX LABTAV under operational constraints. The best-performing configuration used only 2
qubits and was executed on CoreDevX's SpinQ Triangulum II, a 3-
qubit nuclear magnetic resonance (NMR) device, enabling hardware validation beyond classical simulation. The
quantum one-class classifier based on Automatic
Quantum Feature Mapping (AQFM) achieves 88% recall (7 of 8 frauds detected) and 9.21% precision, corresponding to approximately 70% fewer false positives than the best-performing classical baseline at comparable recall. When its 2025-calibrated decision threshold is applied unchanged to the independent 2026 cohort, AQFM detects 20 of 31 frauds (64.5% recall) with 8.81% precision and remains the best-performing model among those evaluated.
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High Energy Astrophysical Phenomena
Radial Modes of Hot Neutrino-Trapped Hybrid Stars
Peter B. Rau, Andrea Sabatucci and Armen Sedrakian
We study the fundamental radial oscillation mode of hot hadronic and hybrid
stars under conditions relevant to proto-
neutron stars and
neutron-
star merger remnants. The
stellar backgrounds are constructed from finite-temperature equations of state with a covariant density functional for hadronic matter and three-
flavor 2SC
quark matter at high density. We consider two isentropic configurations in both
neutrino-transparent matter and with trapped electron
neutrinos at fixed electron-
lepton fraction. For trapped matter we compare a Gibbs-type construction with global electron-
lepton-number conservation to a locally constrained Maxwell-type prescription; in both cases the fixed-
entropy stellar equation of state contains an extended coexistence region and no sharp interface requiring conversion rate-dependent junction conditions. We find that the fundamental radial frequency follows the corresponding purely hadronic sequence up to the onset of deconfinement and then decreases relative to it.
Neutrino trapping shifts this dynamical signature to larger
stellar masses and central pressures, reflecting the delayed appearance of
quark matter. The Maxwell-type prescription moves the onset of deconfinement to still higher central pressure and produces a more rapid decrease of the mode frequency near the stability limit. We quantify the deconfinement effect through the fractional frequency shift between hybrid and hadronic
stars at equal gravitational mass. These results show that the fundamental radial mode provides a sensitive dynamical probe of the interplay among
entropy,
lepton trapping, phase-transition construction, and
quark deconfinement in hot compact
stars.
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Fluid Dynamics
Well-posed by Design: Learning Constitutive Laws from Velocity Data using Convex Neural Network Potentials
Gonzalo G. de Diego and Georg Stadler
Learning constitutive laws of complex fluids from velocity data (i.e. indirect observations) is a PDE-constrained inverse problem in which expressive neural parameterizations risk breaking the well-posedness of the forward physics model. We address this tension by learning, rather than the constitutive law itself, the dissipation potential: a scalar function whose convexity, frame-indifference, and dissipativity propagate into the underlying continuum mechanics and guarantee the structural properties needed for a well-posed and generalizable forward PDE. We introduce ICNNE, an input-convex neural architecture that exactly enforces convexity, frame-indifference, and evenness in the second strain-rate invariant via symmetrization, alleviating the numerical instabilities that occur at small strain rates in standard formulations. By weakly enforcing zero gradients in the origin of the potential via penalization, ICNNE also satisfies the dissipativity property. The loss objective and its gradient are computed using a combination of finite element and neural network methods, coupling the Firedrake and PyTorch libraries. We evaluate on four problems spanning compressible and incompressible regimes: compressible Navier-Stokes, Herschel-Bulkley yield-stress flow, Hibler's viscous-plastic sea-ice model, and discrete-element-method data with no known constitutive law. We show that the learned potentials (i) recover ground-truth physics where it is known, (ii) transfer accurately to geometries unseen during training, and (iii) succeed in regimes where unstructured methods diverge. These results suggest that
embedding mathematical structure into the parameterization, rather than into the loss, is a robust path to learning physics from indirect data.
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Optics
Recoil-heating modulation in levitated optomechanics through optical wavefront shaping
Hugo Marot, Joel Love Nanfack, Murad Abuzarli et al. (+3 more)
Optical levitation relies on light forces to trap mesoscopic objects in a
vacuum and assemble pristine oscillators, whose mechanical properties are commonly tamed through
laser-intensity modulation–e.g., to provide leverage over the stiffness or engineer
quantum states. When approaching the
quantum regime at low pressure, the oscillator's dynamics is governed by
recoil heating, which stems from the backaction of scattered
photons and whose control is highly desirable. Here, we demonstrate that spatial degrees of freedom accessible within the trapping-light field can be harnessed to modulate
recoil heating. Specifically, we introduce an optimization routine that spatially shapes the optical field's wavefront to either maximize or minimize the
recoil-heating rate independently of other parameters like the mechanical stiffness. Importantly, this approach can serve to devise sequences of patterns providing smooth and deep modulations. Implementable into common experimental setups, this work leads the way to the dynamic modulation of optomechanical coupling in optical levitation.
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All authors Hugo Marot, Joel Love Nanfack, Murad Abuzarli, Yann Louyer, Mathias Perrin, Nicolas Bachelard
High Energy Physics (Theory)
Geometry of massive loops in gravitational scattering: Maximal cut, Riemann's bilinear relations and genus drop
Arpan Bhattacharyya and Saptaswa Ghosh
We study a representative two-loop family of worldline
quantum field theory integrals relevant for classical gravitational scattering with a massive mediator and investigate the
geometric structure of its maximal cut. We find that, unlike the massless case, the massive loops already give rise to an
elliptic maximal cut at two loops, which degenerates into a nodal curve in the massless limit and in the static limit. In the global Baikov representation, two successive integrations reduce the maximal cut to a period of an
elliptic curve. We further establish five primary consequences of this study: (a) The integration-by-parts method generates five master integrals, which, under reflection, split into a three-dimensional
elliptic block and a two-dimensional polylog block. We derive the differential equation in two ways, one by Laporta reduction and subsequently by intersection theory in two cocycle bases, and construct the rational map between them. (b) The period
matrices in arbitrary dimension have been computed in terms of Appell and Beta functions. Furthermore, we derive twisted Riemann period relations that yield nine quadratic identities among them. (c) We study the global monodromy relation of the differential system that satisfies Riemann's bilinear relation. (d) We explicitly derive the function space of the iterated integrals in terms of
elliptic multiple polylogs. (e) In impact-parameter space, the
Fourier-transformed cut is a Bessel-twisted differential on the
elliptic curve, which we show has extra involution
symmetries. Thus, the parity of the differential further decides which quotient - rational or
elliptic its periods live on. All results presented concern the maximal cut and, therefore, the homogeneous solutions, but they open an important pathway to tackling the full massive two-loop integral.
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High Energy Physics (Phenomenology)
Toward N$^3$LO CT global PDF analyses: The SACOT-$\chi$ scheme in DIS and DGLAP evolution at partial N$^3$LO
Marco Guzzi, Yao Fu, Casey Hampson et al. (+5 more)
We discuss three aspects of the ongoing efforts of the CTEQ–TEA group toward global parton distribution function (PDF) analyses beyond NNLO accuracy in QCD. First, we present a realization of the SACOT-$\chi$ general-mass variable
flavor number scheme for deep-inelastic scattering (DIS) at the partial next-to-next-to-next-to-leading order (pN$^3$LO) in QCD. We numerically illustrate how this SACOT-$\chi$ theory prediction captures the dependence of DIS structure functions on masses of heavy
quarks with inclusion of the available $O(\alpha_s^3)$ contributions. Second, we discuss a preliminary pN$^3$LO CT25 fit that implements such contributions. Third, we extend the Candia
algorithm for solving DGLAP
evolution equations for unpolarized parton distribution functions (PDFs) in $x$ space to N$^3$LO in QCD. The
algorithm is based on logarithmic expansions of the solution and can be extended to all orders in QCD. An expansion equivalent to the exact DGLAP solution at N$^3$LO is presented in the non-singlet sector. We show results for approximate N$^3$LO PDFs evolved using the most recent approximations to the 4-loop splitting functions in QCD.
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All authors Marco Guzzi, Yao Fu, Casey Hampson, Pavel Nadolsky, Maximiliano Ponce-Chavez, Tanishq Sharma, Keping Xie, C.-P. Yuan
Materials Science
Effect of Source-to-Substrate Distance on the Optical and Electrical Properties of Thermally Deposited CdTe, CdSe and Sb$_2$S$_3$ Thin Films
Himanshu Sharma Pathok and Prasanta Kumar Saikia
In this work, cadmium telluride (CdTe), cadmium selenide (CdSe), and antimony sulfide (Sb\(_2\)S\(_3\)) thin films were deposited using the thermal evaporation technique by varying the source-to-substrate distance (SSD) from 15 to 24 cm (15, 18, 21, and 24 cm). The influence of the SSD on the structural, compositional, optical and electrical properties of the deposited films was systematically investigated. XRD analysis revealed the polycrystalline nature of the CdTe and CdSe thin films, whereas the Sb$_2$S$_3$ thin films exhibited an amorphous nature. EDX spectroscopy confirmed the presence of the constituent elements in the deposited films. Optical analysis revealed a marginal variation in the optical band gap with increasing SSD, while the film thickness, determined using the envelope method, decreased with increasing SSD. The optical band gap energies of CdTe and CdSe were found to be below 2 eV, whereas Sb$_2$S$_3$ exhibited a relatively higher band gap. The relatively low band gap energies and high absorption coefficients of the CdTe and CdSe films make them promising candidates for absorber layer applications in thin film
solar cells (TFSCs). The films exhibited relatively low optical transmittance, which is desirable for efficient light absorption in absorber layers. Electrical characterization confirmed the semiconducting nature of all the deposited thin films. Overall, the results demonstrate that the optical and electrical properties of CdTe, CdSe and Sb$_2$S$_3$ thin films can be effectively modified by varying the SSD. The findings indicate that, in addition to the well established CdTe absorber, CdSe thin films show potential for application as absorber materials in TFSCs.
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Quantum Physics
Open-System Probe Selection and Optimal Measurements for Dispersive Coupling Metrology
Achal Vinod, Da-Wei Luo and Ting Yu
We investigate how
photon loss and environmental
memory affect probe selection and measurement sensitivity for estimating the dispersive coupling strength in a cavity
qubit system. Using density operator and
quantum state
diffusion approaches, we examine the
quantum Fisher information for representative separable and entangled initial states in Markovian and non Markovian regimes. The results show that closed system generator variance alone does not determine open system performance. The survival of parameter sensitive coherences and the influence of environmental
memory also play important roles. Within the single
photon preparations examined, a separable probe can outperform the entangled family considered. Comparisons of selected coherent and squeezed
vacuum preparations at equal mean
photon number further illustrate how
photon number statistics and
qubit preparation affect sensitivity. For the parameters studied, finite environmental
memory can enhance and prolong sensitivity and yield nonzero QFI for a probe whose Markovian QFI vanishes. We also numerically identify a fixed Hermitian observable whose error propagation uncertainty remains close to the
quantum Cramer Rao bound over a prescribed coupling interval in the Markovian regime. These findings clarify the interplay between probe preparation, environmental dynamics, and measurement choice in dispersive
quantum metrology.
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Plasma Physics
An Implicit, Moment-Conserving Low-Rank Tensor Method for the Hybrid Kinetic-Ion Fluid-Electron Plasma Model
Stephen R. White, Adam J. Stanier, Luis Chacón et al. (+2 more)
Quasi-neutral hybrid models for simulating
plasmas, with kinetic ions and fluid electrons, have shown great promise for approaching the multi-scale nature of
plasmas. In this paper we present a novel hybrid scheme for electromagnetic settings that conserves mass, momentum, and energy, employing a low-rank tensor method utilizing the Tensor Train decomposition to avoid the \enquote{curse of dimensionality.} Electrons are simulated as a continuous fluid, while the kinetic ions are modeled as a distribution function governed by the Vlasov equation. The Vlasov equation is updated with the implicit midpoint method. We use a modified version of a conservative truncation method to guarantee conservation of mass, momentum, and energy throughout the method, which corrects the truncated distribution function without needing to advance a separate set of fluid-moment equations. A series of electrostatic and electromagnetic test problems is used to demonstrate the correctness of the method and its conservation properties.
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All authors Stephen R. White, Adam J. Stanier, Luis Chacón, Will T. Taitano, Isaac A. Castro
Chemical Physics
Many-body Interactions in Ultrafast Spectroscopy
Diego Florio, Alessandro Baserga, Sofia Bertuetti et al. (+5 more)
Nonlinear spectroscopy is widely used to probe ultrafast dynamics in matter. Signals of higher nonlinear orders encode valuable many-body dynamics but only recently have become individually retrievable. However, their physical interpretation in terms of double-sided Feynman diagrams is cumbersome and non-intuitive. Here, we establish an alternative framework that connects them to the underlying excitation conditions and many-body interactions. This approach predicts two classes of dynamic nonlinearities, due either to direct many-body interactions or to saturable kinetic channels. The method provides a direct physical interpretation of the retrieved signals, explaining their sign, magnitude, and dynamics. It also enables model-free reconstruction of the dynamics of a sub-ensemble of particles starting with a given number of
excitons, which we demonstrate to be especially insightful. We validate the framework using colloidal CdSe/CdS core/shell
quantum dots, which enable us to model nonlinearities of both classes in isolation and also combined.
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All authors Diego Florio, Alessandro Baserga, Sofia Bertuetti, Federico Visentin, Adar Levi, Uri Banin, Giulio Cerullo, Franco V. A. Camargo
Mesoscale and Nanoscale Physics
Contact-Governed Macroscopic Signatures of Strain-Induced Valley Sorting in MoS$_2$ Field-Effect Transistors
Suhas Suresh Bharadwaj
Strain engineering is a leading route to control valley-selective transport in monolayer transition metal dichalcogenides. Whether this
quantum effect survives inside a fully contacted device remains an open question.
Quantum transport models capture the underlying valley deflection but are limited to isolated nanoscale fragments, leaving it unclear if a full device registers strain-induced valley sorting in the bulk, at the contacts, or at all. Here, the
quantum valley-deflection tensor of strained monolayer MoS$_2$ is embedded directly into a macroscopic Poisson-drift-
diffusion model, extending this physics to a complete, contact-inclusive device. Applying this framework to a 300~nm monolayer MoS$_2$ transistor with a 3~nm HfO$_2$ gate dielectric at 77~K, under a localized 6.14~T pseudo-
magnetic strain field, shows the resulting 63.6% suppression of the ON-state current is not a bulk property. It is set almost entirely by the source and drain metal-
semiconductor interfaces. The full suppression is reproduced when only the 15~nm contact regions are strained and nearly vanishes when the channel interior alone is strained, identifying the metal contact as the dominant site of strain-induced valley physics. Observing it requires tunneling-transparent, degenerately-doped contacts, since classical Ohmic barriers overwhelm the topological signal. A transmission-line analysis reduces this behavior to a single valley-topological contact resistance ($R_{c,V}$) and a predictive inverse-length scaling law. This framework applies to any strain-engineered 2D-material
heterostructure and can be tested with standard multi-length contact structures. Ultimately, these results identify the metal-
semiconductor interface as the decisive location for engineering and detecting valley-selective transport in real 2D-material devices.
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Earth and Planetary Astrophysics
Exploring the ultrahot Neptune LTT 9779 b with CRIRES+. Non-detection of helium transmission spectra and detection of H$_2$O on the dayside
S. Liu, F. Yan, L. Nortmann et al. (+15 more)
Ultrahot Neptunes reside in the most extreme irradiation regime of the hot Neptune desert and remain challenging targets for atmospheric characterization because of their low
planet-to-
star flux ratios. We present high-resolution transit and dayside thermal emission spectroscopy of the ultrahot Neptune LTT 9779 b obtained with CRIRES$^+$, to probe atmospheric escape and dayside molecular emission. No significant absorption is detected in the metastable He I $\lambda 1083$ nm triplet during transit, yielding a $3\sigma$ upper limit of 0.45% on the excess helium absorption depth and supporting previous non-detections that suggest weak ongoing atmospheric escape. For the dayside emission spectra in the $K$ band, our cross-correlation analysis reveals an $\mathrm{H_2O}$ absorption signal and a tentative $\mathrm{CO}$ feature, with the combined signal reaching a detection significance of $4.8\sigma$. Both the CRIRES$^+$ and previous JWST data favor a non-inverted temperature structure, providing no evidence of a thermal inversion on the planetary dayside. We further perform a joint atmospheric
retrieval combining the CRIRES$^+$ high-resolution spectra with JWST/NIRISS SOSS secondary-eclipse observations. The joint
retrieval yields a low $\mathrm{H_2O}$ abundance, while the $\mathrm{CO}$ abundance remains weakly constrained. The inferred planetary equatorial rotational velocity, $v_{\rm eq}=4.9^{+4.4}_{-3.0}~\mathrm{km\,s^{-1}}$, is consistent within $1\sigma$ with the synchronous rotation velocity expected for a tidally locked
planet ($\sim2.8~\mathrm{km\,s^{-1}}$). However, the large uncertainties prevent us from placing strong constraints on the
planet's rotation state. Future phase-resolved CRIRES$^+$ observations with broader orbital-phase coverage and higher signal-to-noise ratios would improve the abundance constraints and probe the atmospheric dynamics of this rare ultrahot Neptune.
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All authors S. Liu, F. Yan, L. Nortmann, B. Guo, D. Cont, F. Lesjak, D. Shulyak, A. Reiners, N. Piskunov, A. P. Hatzes, U. Seemann, A. Lavail, A. D. Rains, H. L. Ruh, L. Boldt-Christmas, M. Rengel, O. Kochukhov, T. Marquart
Chemical Physics
Is there a density-gradient expansion for the electronic exchange energy?
John P. Perdew, Timo Lebeda, Rohan Maniar et al. (+3 more)
An old but recurring question in ground-state density functional theory, relevant to the construction of density functional approximations, is the existence of a second-order gradient expansion for the exchange energy that is exact for densities that vary slowly over space. Here we will argue that there is such an expansion, with a gradient coefficient 10/7 of Sham's, as suggested by theoretical/mathematical derivations and by numerical calculations on model slowly-varying metallic densities, although some standard derivations do not quite capture the correct gradient coefficient. We also discuss long-range anomalies in the gradient expansions for the exchange and correlation holes around an electron. It is plausible that, as suggested earlier and recently, standard derivations are still correct for the coefficient of the second-order gradient expansion for exchange and correlation together, in which case the correct gradient coefficient for correlation is $C_{\mathrm{c}}$ = $C_{\mathrm{xc}}$ - $C_{\mathrm{x}}$. We propose possible numerical evaluations of $C_{\mathrm{xc}}$ and $C_{\mathrm{x}}$ that are free from long-range anomalies, and discuss implications for density functional approximations. Axel Becke's 1988 generalized gradient approximation (the B88 GGA) for the exchange energy brought density functional theory into chemistry, with a gradient coefficient for exchange that is optimal at the GGA level for atoms and molecules but too large for solids. Meta-GGAs seem to work as well for molecules as for solids, but may not be perfected yet. The article concludes with a few
memories that the first author has of discussions with Axel Becke.
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All authors John P. Perdew, Timo Lebeda, Rohan Maniar, Chandra Shahi, Adrienn Ruzsinszky, Jianwei Sun
General Relativity and Quantum Cosmology
Where the Gauss–Bonnet coupling enters the Bondi–Sachs hierarchy
Maickol Muñoz-Palma, Alvaro Restuccia and Francisco Tello-Ortiz
We integrate the Bondi–Sachs hierarchy of scalar–Gauss–Bonnet
gravity with an arbitrary coupling function $f(\Phi)$ and a radiating massless scalar, and determine the first order in $1/r$ at which the coupling $\lambda$ becomes visible in each field equation. We obtain the asymptotic falloff of the effective Gauss–Bonnet stress tensor together with its leading coefficients in covariant form on the sphere: every component decays between one and three powers of $1/r$ faster than the slowest falloff compatible with a smooth null infinity. As a consequence, (i) the Bondi mass-loss formula and the
evolution equation of the angular-momentum aspect are those of the minimally coupled Einstein–scalar system, a statement that is exact in $\lambda$ under the assumption of a smooth expansion; (ii) the coupling generates no logarithmic terms through the orders considered, even though the Horndeski representation of the theory involves logarithmic functionals; and (iii) the coupling first enters a dynamical equation in the
evolution of the $O(r^{-3})$ coefficient of the angular metric, through the cross term $-2\lambda f'(\vp_0)\,\vp_1\,\partial_u N_{AB}$ between the asymptotic scalar charge aspect and the time derivative of the news. In Newman–Penrose form, the
evolution equation of the leading coefficient of $\Psi_0$ acquires the source $-12\lambda f'(\vp_0)\,\vp_1\bar\Psi_4^0$, while those of $\Psi_1$ and $\Psi_2$ are unchanged. The Gauss–Bonnet invariant decays as $r^{-6}$ and affects the scalar hierarchy only from the
evolution of the $r^{-5}$ coefficient onward. For
vacuum black-hole spacetimes, where the scalar is sourced by the coupling itself, all these effects are of order $\lambda^2$; if $f'(\vp_0)=0$ they are pushed one further order in $1/r$.
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Instrumentation and Detectors
The CosmicWatch Desktop Muon Detector (v3X): Prototype Design and Adaptation for Spaceflight
Anvay Ajmera and Spencer N. G. Axani
The CosmicWatch Desktop
Muon Detector (v3X) is a compact and low-cost scintillator-based instrument designed to detect ionizing radiation, including
cosmic-ray
muons. Built around a plastic scintillator, a silicon photomultiplier (SiPM), and a dual-core Raspberry Pi Pico microcontroller, the v3X achieves a 400 microsecond dead time per event, sustained event logging at 700 Hz, and two-detector coincidence triggering for more accurate counts. This paper first summarizes the design, firmware, and demonstrated performance of the v3X prototype. It then outlines the design changes needed to prepare the detector for operation aboard a satellite, including a passive copper thermal strap that conducts heat from the microcontroller to the spacecraft chassis, a dedicated flight enclosure, material changes to meet outgassing standards, and a Controller Area Network (CAN) bus interface to connect the detector to the host spacecraft. The flight unit is targeted for launch via Oligo Space.
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Quantum Physics
Learning Disentangled Representations with Quantum Variational Autoencoders
Gaoyuan Wang, Jerry Tan and Mark Gerstein
Variational autoencoders are powerful representation learning models that map complex data into low-dimensional latent spaces, enabling the discovery of interpretable and disentangled factors. Such representations can facilitate the interpretation and controllable generation of data describing complex scientific systems. Understanding how these factors are organized and encoded in latent space is therefore important for developing reliable representation learning models. Recently,
quantum variational autoencoders (QVAEs) have been proposed as
quantum representation models, demonstrating informative latent representations and improved latent-space occupancy through
quantum regularization. However, it remains unclear whether and how QVAEs can learn disentangled and interpretable latent factors. A key challenge in investigating
quantum latent factors is that a small number of
qubits spans an exponentially large
Hilbert space, making the notion of an individual
quantum latent dimension nontrivial. Here, we investigate what constitutes an individual
quantum latent dimension and whether it can encode a distinct factor. We develop theoretical insights into
quantum latent dimensions and support them with empirical studies on representative synthetic problems, including MNIST variants. Across three
datasets, we demonstrate that QVAEs can discover factorized and semantically interpretable latent representations, with individual
qubits functioning as meaningful latent factors. These results establish a foundation for understanding
quantum latent spaces and their potential for structured and interpretable representation learning.
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High Energy Physics (Phenomenology)
Unitarity limits on HH production from VBF mediated channels
A. Dobado, D. Domenech, M. Herrero et al. (+1 more)
In this work we study the unitarity constraints on double
Higgs production from Vector
Boson Fusion mediated channels, specifically in $f_1 f_2 \to f_3 f_4 H_5 H_6$ scattering, where $f$ refers generically to either
fermion or anti-
fermion, and both cases with
quarks and
leptons will be considered. We focus on the beyond Standard Model contributions from anomalous quartic couplings of two electroweak gauge
bosons and two
Higgs bosons ($VVHH$ with $VV=WW, ZZ$) from effective operators containing four derivatives. These four derivative operators appear in the two most popular effective field theories, SMEFT (at canonical dimension 8) and HEFT (at
chiral dimension 4), and their corresponding $VVHH$ effective vertices can be easily related for the considered processes here. The aim of this work is to derive jointly the unitarity constraints on these related effective vertices using the peculiarities of the VBF mediated channels with four particles in the final state while keeping the propagation of the internal $VV$ pairs being off-shell as it must be for these channels. We also discuss the relevance of the obtained constraints for $f_1 f_2 \to f_3 f_4 H_5 H_6$ at high energy
colliders.
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All authors A. Dobado, D. Domenech, M. Herrero, R. A. Morales
Optics
Dual-channel metasurfaces for refractometric and spatial heterogeneity sensing
Zhongjun Jiang, Nicolas Gomez, Soyaib H Sohag et al. (+1 more)
Nanophotonic sensors amplify analyte-induced optical signals through resonantly enhanced light-matter interactions. While effective for refractometric sensing, conventional sensing platforms typically collapse spatial variations in analyte distributions into ensemble-averaged readouts, thereby obscuring local heterogeneity. Here we present a dual-channel metasurface sensor capable of detecting both net analyte loading and nanoscale spatial inhomogeneity at deep-subwavelength scales. The device supports two distinct high-Q modes with deeply structured near-field profiles of opposite parity. Their complementary modal responses decouple analyte perturbations into bulk and differential components, which are encoded into two spectrally resolvable channels. We demonstrate these sensing modalities across analyte configurations exhibiting diverse forms of nanoscale heterogeneity, achieving a refractometric sensitivity of 357 nm/RIU and inhomogeneity detection below $\lambda/10$. This dual-channel capability, which extends nanophotonic sensing from analyte quantity to its spatial variation, opens a new avenue for multidimensional analysis of biological and material systems.
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All authors Zhongjun Jiang, Nicolas Gomez, Soyaib H Sohag, You Zhou
Astrophysics of Galaxies
Hierarchical Black Hole Mergers at High Redshift: Predictions for LISA and LGWA from SEEDZ
Daxal H. Mehta, Lewis R. Prole, John A. Regan et al. (+13 more)
We investigate the hierarchical assembly of black holes (BHs) in the early Universe using the next-generation SEEDZ cosmological zoom-in simulations. Our suite follows two independent regions (Rarepeak and Normal1) evolved with three BH feedback prescriptions: no feedback (NoFB), weak feedback (WeakFB), and standard thermal isotropic feedback (FidBH). Focusing on BH mergers at $z \geq 10$, we explore merger-driven BH growth and detectability with next-generation gravitational-wave observatories. We find that stronger AGN feedback models dramatically suppress hierarchical BH assembly compared to weaker feedback implementations. In the NoFB simulations, BHs frequently undergo repeated mergers, with some experiencing more than 50 merger events within a few hundred Myr and gaining over $10^8,\mathrm{M_{\odot}}$ through mergers alone. In contrast, BHs in the FidBH simulations rarely undergo more than three mergers. NoFB therefore represents an upper limit to BH merger-driven growth beyond what is expected in the Universe. The suppression of BH mergers in the FidBH case is not driven by differences in
galaxy assembly, BH occupation fractions, or BH seed abundances, which remain broadly similar across the simulation suites. Instead, feedback disrupts the dense gas surrounding newly formed BH seeds, suppressing their early
accretion-driven growth and preventing them from entering runaway hierarchical merger pathways. Our results demonstrate that early-Universe feedback prescriptions strongly influence hierarchical BH growth through both mergers and
accretion, producing distinct high-
redshift merger populations. Coupled with seeding choices and other BH subgrid prescriptions, this introduces multiple degeneracies that will need to be broken in advance of LISA and other next-generation GW facilities.
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All authors Daxal H. Mehta, Lewis R. Prole, John A. Regan, Rüdiger Pakmor, Sophie Koudmani, Ricarda S. Beckmann, Michael Tremmel, John H. Wise, Martin A. Bourne, Ralf S. Klessen, Simon C. O. Glover, Martin G. Haehnelt, John Brennan, Pelle Van De Bor, Debora Sijacki, Paul C. Clark
Astrophysics of Galaxies
Spectroscopic Confirmation of the Milky Way Satellites Boötes V and Leo Minor I and the LMC Satellite DELVE 2: Three Small Ultra-Faint Dwarf Galaxies
W. Cerny, M. Geha, J. D. Simon et al. (+22 more)
We present the first multi-object spectroscopy of Boötes V, Leo Minor I, and DELVE 2 – three small (20 pc $\le r_{1/2}\le$ 26 pc), ultra-faint ($-3.2\le M_V\le-2.1$)
stellar systems in the outer
Galactic halo (71 kpc $\le D_\odot\le$ 102 kpc) with heretofore ambiguous classifications. Leveraging at least two epochs of Keck/DEIMOS or Magellan/IMACS observations targeting each satellite, we identify 13, 7, and 7 spectroscopic members in the three systems, respectively. We tentatively resolve a $\sigma_v=2.1^{+1.5}_{-0.9}$ km s$^{-1}$ velocity dispersion for DELVE 2 but place upper limits of $\sigma_v<2.7$ km s$^{-1}$ and $\sigma_v<7.8$ km s$^{-1}$ for Boötes V and Leo Minor I. We find that all three systems are very metal-poor, with mean iron abundances $-2.85\le\overline{\rm [Fe/H]}\le-2.15$. Both Boötes V and Leo Minor I display unambiguous
metallicity spreads ($\sigma_{\rm [Fe/H]}=0.46^{+0.18}_{-0.12}$ dex and $\sigma_{\rm [Fe/H]}=0.57^{+0.23}_{-0.18}$ dex), while DELVE 2 displays a modestly significant spread ($\sigma_{\rm [Fe/H]}=0.52^{+0.29}_{-0.25}$ dex) across three
stars. Based primarily on these
metallicity measurements, we confidently classify Boötes V and Leo Minor I as
dwarf galaxies and determine that DELVE 2 is most likely a
dwarf galaxy as well. We explore the orbit of each satellite in a joint Milky Way + LMC potential, confirming for the first time that DELVE 2 is a long-term bound satellite of the LMC. Finally, we review the empirical Milky Way satellite classification landscape and find that nearly every spectroscopically characterized satellite with azimuthally averaged half-light radius $r_{1/2}>15$ pc and surface brightness $\mu_{V,1/2}>26.5$ mag arcsec$^{-2}$ is likely a
dwarf galaxy. This result can guide initial probabilistic classifications for satellites discovered by $\textit{Rubin}$, $\textit{Roman}$, and $\textit{Euclid}$.
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All authors W. Cerny, M. Geha, J. D. Simon, T. S. Li, A. B. Pace, R. P. van der Marel, N. Kallivayalil, A. P. Ji, A. Drlica-Wagner, D. Crnojević, G. Limberg, N. E. D. Noël, A. H. Riley, D. J. Sand, G. S. Stringfellow, Y. Choi, P. S. Ferguson, C. E. Martínez-Vázquez, P. Massana, G. E. Medina, B. Mutlu-Pakdil, J. D. Sakowska, C. Y. Tan, A. K. Vivas, J. Bruce
Earth and Planetary Astrophysics
Enhancing the Interpretability of Radial Velocity Analysis Using Leave-one-out Cross-validation
Matthew C. Nixon, Ritvik Basant, Rafael Luque et al. (+2 more)
Radial velocity (RV) observations are reaching increasingly high precision, enabling the targeting of low-amplitude signals. Assessing results obtained at the limits of our capabilities requires understanding the relationship between data, models and inference. Leave-one-out cross-validation (LOO-CV) has become an increasingly popular tool for interpretable model criticism in astronomical data analysis. In this work, we demonstrate how LOO-CV can provide insight into the RV analysis of exoplanetary systems through three case studies. We first investigate the anomalously high mass of HD 119130 b inferred from CARMENES RVs, later revised significantly downward after follow-up observations with other instruments. We show that this high mass was strongly driven by two individual measurements, whose removal significantly reduces the tension between data sets. Next, we use LOO-CV as a model selection tool for the GJ 4276 system. Here, LOO-CV prefers an eccentric single-
planet model over a two-
planet model, and identifies the orbital phases at which follow-up observations would best discriminate between them. Finally, we extend LOO-CV to models with correlated noise, applying it to the GJ 357 system, whose RVs are modeled with a Gaussian process. We find no predictive support for a fourth planetary signal that is moderately favored by the
Bayesian evidence, strengthening the interpretation of a three-
planet architecture previously reported in the literature. We provide practical guidance for implementing LOO-CV in RV analysis, together with an online tutorial. Such methods will become ever more important as future RV surveys push the limits of
planet detection and characterization.
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All authors Matthew C. Nixon, Ritvik Basant, Rafael Luque, Luis Welbanks, Pierrot Lamontagne
Mesoscale and Nanoscale Physics
Adjoint-State Identifiability of Piezo-Tunable Valley Splitting in 2D Magnetic Heterostructures
Suhas Suresh Bharadwaj
Controlling valley degrees of freedom with mechanical strain is a promising approach for solid-state information processing. Current theoretical literature routinely predicts strain-tuned valley splitting at the microscopic level but rarely evaluates whether these
quantum predictions remain statistically recoverable in realistic macroscopic devices. This manuscript establishes a fully classical, partial differential equation-constrained multiscale inverse framework for quantifying the device-level identifiability of predicted strain-tunable valley effects in two-dimensional
magnetic heterostructures, demonstrated here for a molybdenum disulfide and chromium tribromide
heterostructure. First-principles structural relaxations confirm a
chiral $C_3$ point-group
symmetry which mathematically reduces the relevant exchange-strain coupling tensor to a single scalar. A partial differential equation-constrained adjoint-state architecture successfully bridges continuum elastodynamics to valley-resolved anomalous
Hall transport. Density functional theory yields a coupling estimate of $\eta \approx -0.07$ meV whose 95% confidence interval is consistent with zero. Evaluating this specific coupling magnitude against established thermal noise and velocity saturation limits defines a safe operating window bounded between 262.0 and 22,337.6 V/cm. Rather than asserting a confirmed nonzero material property this bounded operational window functions as a precise diagnostic threshold. Deploying this rigorous statistical identifiability framework provides a necessary mathematical filter to determine the true experimental viability of theoretically predicted two-dimensional materials before complex physical fabrication.
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Astrophysics of Galaxies
Molecular hydrogen formation on dust: The impact of gas-dust drift on formation efficiency
Stefan Reissl, Simon C. O. Glover, Ralf S. Klessen et al. (+2 more)
Molecular hydrogen is predominantly formed on
dust-grain surfaces in the interstellar medium, where relative gas-
dust motion can arise in dynamically active environments. While the dependence of H$_2$ formation on grain temperature and surface properties is well studied, the impact of gas-
dust drift has received little
attention. We investigate how gas-
dust drift modifies H$_2$ formation, focusing on the competition between the drift-enhanced H-atom collision rate and reduced sticking at higher impact energies. We use an event-driven kinetic Monte Carlo model that follows individual H atoms on spherical silicate and carbonaceous grains, including adsorption, surface migration, thermal desorption, and Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) reactions. Drift is described by a shifted Maxwellian velocity distribution, and we compare constant and impact-energy-dependent sticking probabilities. Drift produces increasingly anisotropic distributions of adsorbed H and H$_2$ formation across the grain surface. Assuming constant sticking, increasing drift enhances H$_2$ formation through the higher collision rate, with efficiencies up to $\epsilon=0.3-0.4$. With energy-dependent sticking, strong drift instead suppresses formation on both materials, reducing efficiencies to $\epsilon=0.01-0.03$. Carbonaceous grains remain efficient to higher
dust temperatures than silicate grains. ER reactions dominate over most of the investigated parameter space and become increasingly important at strong drift as the reduced surface population suppresses LH reactions. Thus, enhanced collision rates under gas-
dust drift do not necessarily increase H$_2$ formation. Models of dynamically active environments should account for both relative gas-
dust velocities and their effects on sticking.
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All authors Stefan Reissl, Simon C. O. Glover, Ralf S. Klessen, Liam S. Morrissey, Mordecai-Mark Mac Low