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Physics

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Thursday 25 June

Cosmology and Nongalactic Astrophysics

Forward-modelling the Tolman and distance-duality tests with IllustrisTNG

Harry Desmond, Tariq Yasin, Richard Stiskalek et al. (+1 more)

The Tolman surface-brightness test and the angular-size distance-duality test are two complementary probes of the same underlying relation between luminosity and angular-diameter distance, $D_L = (1+z)^2 D_A$, as holds in any metric theory of gravity where photon number is conserved. Both tests have recently delivered a priori surprising signals: JWST/ASTRODEEP measurements yield a surface brightness scaling with redshift much flatter than the expected value, and ultracompact radio sources also appear to follow a flatter $D_L/D_A$ scaling with redshift. These results have been suggested to support non-expanding cosmologies, however they are also sensitive to astrophysical and instrumental effects. We test whether these results indicate genuine departures from standard cosmology by forward-modelling observed surface-brightness evolution in the IllustrisTNG cosmological hydrodynamical simulation, with an empirical mock-spectroscopic selection trained on ASTRODEEP. We show that the astrophysical evolution relevant for both tests may be effectively parametrised as a single power-law exponent for the luminosity density as a function of redshift, for which the simulation gives $\gamma=2.23\pm0.20$ across realistic aperture conventions. This value is approximately sufficient to explain both the Tolman and distance-duality signals within standard cosmology and galaxy formation physics, with a small discrepancy for the latter suggesting that radio AGN evolve slightly more strongly than bright galaxies.
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All authors Harry Desmond, Tariq Yasin, Richard Stiskalek, Sebastian von Hausegger

Cosmology and Nongalactic Astrophysics

Redshift-Dependent Intrinsic Dispersion in the Quasar UV/X-ray Luminosity Relation

Jiaze Gao, Jianping Hu, Yun Chen et al. (+2 more)

Accurate modeling of the intrinsic dispersion in the quasar UV/X-ray luminosity relation is essential for reliable cosmological inference. We investigate its redshift dependence using luminosity distances reconstructed from cosmic chronometer and baryon acoustic oscillation measurements through Gaussian-process (GP) regression. Bayesian model comparison and posterior constraints show that the intrinsic dispersion is not well described by a single redshift-independent constant over $0.7<z<2.6$. It remains approximately constant at $0.7<z<1.6$, but shows an overall decreasing trend in the higher-redshift interval $1.6<z<2.6$, where the redshift-dependent intrinsic-dispersion model is decisively favored. This conclusion remains qualitatively robust against changes in the scaling-relation parameterization, GP kernel, and redshift binning scheme. We further examine its impact on cosmological inference in the flat $\Lambda$CDM model and find that, under the adopted calibration setup, the redshift-dependent intrinsic-dispersion model shifts the posterior median of $\Omega_{\rm m0}$ by $\Delta\Omega_{\rm m0}\simeq 0.025$. This indicates that intrinsic-dispersion modeling is a non-negligible component of the systematic-error budget for quasar cosmology and should be accounted for in future precision analyses.
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All authors Jiaze Gao, Jianping Hu, Yun Chen, Bowen Zhao, Lixin Xu

Chaotic Dynamics · Cross-listed from q-bio.QM

Deep learning model emulators for marine biogeochemistry forecasting from days to decades

Jozef Skakala, Ieuan Higgs and David Moffat

Deep-learning emulators have emerged as a promising approach for reducing the computational cost of Earth System Models while potentially improving forecasting skill. Here, we demonstrate the successful emulation of a high-complexity marine biogeochemistry model within a simplified one-dimensional water-column framework. We explore two emulator architectures: Long Short-Term Memory (LSTM) neural networks that emulate a selected subset of variables at daily resolution, and physics-informed one-dimensional Convolutional Neural Networks (1D CNNs) that emulate the full pelagic system throughout the water column also at daily resolution. Using ocean physics simulator inputs, both emulators remain largely stable over multi-decadal timescales and accurately reproduce the parent model in both decadal climate projections and short-range (10-day) forecasting applications. The former includes the ability to predict the timing of phytoplankton Spring blooms several years in advance. When trained on reanalysis data, the emulators substantially outperform the parent model's forecast skill score for several key ecosystem variables, including phytoplankton and zooplankton. If similar performance can be achieved in three-dimensional regional applications, these emulators could provide substantially higher-quality predictions at a fraction of the computational cost. We further apply novel explainability techniques to identify key drivers of emulator behaviour and gain insights into emergent ecosystem dynamics. Performance is evaluated using a range of metrics, including the reproduction of daily variability and extreme events. These approaches have considerable potential for future applications in operational forecasting, climate-scale simulations, and marine autonomous systems.
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Mesoscale and Nanoscale Physics

Phase-Shifted Planar Hall and Magnetoresistive Responses in Weyl Semimetals

Sandip Bera and Sudhansu S. Mandal

The planar Hall resistivity and magnetoresistivity of Weyl semimetals are conventionally expected to exhibit $\sin 2\phi$ and $\cos2\phi$ angular dependences, respectively, where $\phi$ is the angle between electric and magnetic fields. However, experiments reveal shifted extrema in the planar Hall signal and sign reversals in magnetoresistivity at $\phi < \pi/4$. Here, using a diagrammatic Kubo-formula approach, we identify an intrinsic quadratic magnetic-field contribution to the planar transport response that is absent in conventional semiclassical description. This contribution introduces an additional term proportional to $\cos 2 \phi$ and $\sin 2\phi$, respectively, in transverse and longitudinal conductivities. Consequently, both planar Hall and magnetoresistive responses acquire a phase-shifted form $\sin 2(\phi+\phi_r)$ and $\cos 2(\phi+\phi_r)$, respectively. The same phase shift extracted independently from longitudinal and transverse responses quantitatively describes available experimental data. Our results establish a microscopic origin of the anomalous angular dependence observed in Weyl semimetals.
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High Energy Physics (Experiment)

High Multiplicity Trigger for Long-Lived Particles in CMS detector

M. Abbott, D. Acosta, D. Aebi et al. (+100 more)

Searches for long-lived particles (LLPs) at the CMS experiment often involve unconventional event topologies that are difficult to efficiently select using standard trigger strategies. To improve sensitivity to such signatures during LHC Run~3 operation, a dedicated High Multiplicity Trigger (HMT) has been developed and deployed in the CMS trigger system. The trigger targets events containing unusually large numbers of hits in the CMS cathode strip chamber (CSC) muon detectors, a characteristic signature of several LLP scenarios involving displaced decays in the muon system. The HMT implementation, trigger logic, rate dependence with pileup, and operational stability are described. Optimized hit multiplicity thresholds are used to maintain acceptable trigger rates under high-luminosity and high-pileup conditions while preserving high efficiency across a broad range of LLP lifetimes and kinematic regimes. The trigger performance is evaluated using both simulated event samples and proton-proton collision data collected during Run~3 of the LHC. The HMT substantially extends the CMS sensitivity to non-standard signatures associated with LLP decays and provides a flexible platform for future searches for physics beyond the Standard Model.
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All authors M. Abbott, D. Acosta, D. Aebi, M. Ahmad, A. Albert, A. Apresyan, C. Arbour, C. Aruta, K. Banicz, V. Barashko, E. Barberis, L. Benato, A. Bolshov, J. Bonilla, R. Breedon, K. Bunkowski, H. Cai, C. Campagnari, J. Carlson, V. Cherepanov, M. Chen, R. Clare, R. Clark, P.T. Cox, R. De Los Santos, S. Dildick, M. Dittrich, X. Dong, L.S. Durkin, R. Erbacher, P. Fernández Manteca, P. Flanagan, E. Fontanesi, C. Galloni, Y. Gao, J. Gilmore, A. Greshilov, Y. Haddad, Y. Han, Z. Hao, J. Hauser, E. Hazen, H. He, J. Heikkilae, M. Herndon, C. Hill, T. Huang, M. Ignatenko, M.A. Iqbal, I. Israr, M. Jeitler, S. Jindariani, E. Juska, T. Kamon, V. Karjavine, H. Kim, J. Kim, A. Korytov, O. Kukral, K.H.M. Kwok, E. Kuznetsova, J. Liu, W. Liu, C. Lo, A. Madorsky, N. Manganelli, M. Matveev, H. Mei, N. Menendez, G. Mitselmakher, G. Mocellin, S. Mondal, D.M. Morse, M. Mulhearn, B.P. Padley, V. Palichik, A. Peck, C. Pena, V. Perelygin, D. Rabady, N. Rawal, J. Richman, A. Safonov, P. Siddireddy, M. Spiropulu, I. Suarez, N. Terentyev, M. Tripathi, N. Turner, V. Valuev, C. Wang, J. Wang, Y. Wang, Z. Wang, D. Wenzl, D. Wood, S. Xie, X. Yang, E. Yigitbasi, H. Zhang, Y. Zhang, J. Zheng, X. Zuo

High Energy Physics (Phenomenology)

StringSpinner 2.0: Enabling quark spin effects in PYTHIA for $e^+e^-$ annihilation

A. Kerbizi and L. Lönnblad

The StringSpinner package, which implements quark spin effects in the PYTHIA event generator using the string+${}^3P_0$ model of hadronization, is extended to handle the process $e^+e^-\rightarrow q\bar{q} \rightarrow hadrons$ at leading order. The correlations between the spin states of the $q\bar{q}$ pair produced in the reaction are described by a joint spin density matrix. The spin correlations are propagated along the string fragmentation chain by using the rules of the string+${}^3P_0$ model and are implemented for the production of pseudoscalar and vector mesons. The new version of the package can be used to simulate spin effects in $e^+e^-$ annihilation like the Collins and the Artru-Collins asymmetries. It can also be applied to the study of other spin effects in hadronization predicted by the string+${}^3P_0$ model with a user-defined joint spin density matrix of the $q\bar{q}$ pair. To showcase the usage of the package the polar angle dependence of the Collins asymmetries for back-to-back pions is studied and compared with the available data.
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Computational Physics

Real Quantum Chemistry With Complex Orbitals

Hugo Åström and Susi Lehtola

We follow up our study of basis set truncation errors for atoms in magnetic fields [Åström and Lehtola, J. Phys. Chem. A, 2023, 127, 10872]. Our previous study employed an approximate real-valued model. In this work, we implement a scheme to allow the use of complex basis functions and the true, complex Hamiltonian with linear molecules in a parallel magnetic field within the usual real-basis machinery of quantum chemistry. Our method performs additional unitary transformations before and after a conventional Fock build, thus allowing the reuse of existing software methods and algorithms. We apply our approach to calculations on low-lying configurations of the atoms $Z \leq 18$ in static magnetic fields up to 0.6 $B_0$. The calculations employ the uncontracted aug-cc-pVTZ and the benchmarking quality AHGBSP3-9 Gaussian-type orbital basis sets. We compare total energies obtained with real and complex orbitals using these basis sets to fully numerical ones at the complete basis set limit. We see that the states of the real-valued Hamiltonian are superpositions of the true eigenstates that are correctly captured by the complex calculations. Our results show that the complex basis machinery is necessary for targeting states with the correct symmetry for the studied range of magnetic field strengths. The novel tool is key for future work where we aim to optimize basis sets for finite-field calculations.
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Quantum Physics

Loss-aware pulse sequence optimization for generating photonic Fock states

Benjamin Stodd, Priyanshu Tiwari, René Sondenheimer et al. (+2 more)

We investigate the preparation of frequency-tunable photonic Fock states in a hybrid cavity system consisting of a nonlinear medium and a two-level system. Employing a gradient-based optimization approach, we construct multipulse driving protocols that control the system dynamics through pulse amplitudes, phases, and inter-pulse delays. Assuming unitary dynamics, the optimized sequences enable near-deterministic preparation of low-photon-number Fock states. We extend the optimization framework to open-system dynamics by modeling atomic decay and photon loss within the Lindblad master equation. This allows us to identify pulse sequences that exhibit enhanced robustness against dissipation compared to those optimized under idealized assumptions. Furthermore, we find that optimal pulse sequences obey strict constraints on relative phases, which are limited to values of 0 or $\pi$. These phase restrictions are supported by an analytical study that investigates a simple two-pulse sequence treating the second pulse perturbatively.
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All authors Benjamin Stodd, Priyanshu Tiwari, René Sondenheimer, Sina Saravi, Martin Gärttner

Nuclear Theory

Rapidity-even directed flow splitting of protons and antiprotons as a probe of baryon stopping in relativistic heavy-ion collisions

Tribhuban Parida and Sandeep Chatterjee

We compare the rapidity-even directed flow $v_1^{\rm even}$ in Au+Au collisions at Beam Energy Scan (BES) energies for baryons and anti-baryons within a (3+1)-dimensional viscous relativistic hydrodynamics coupled to hadronic transport framework. The double-junction baryon stopping picture motivates a rapidity-even component in the baryon deposition in the initial state. We demonstrate that the split in the $v_1^{\rm even}$ of protons and anti-protons is sensitive to the rapidity extension of the baryon deposition that we associate with the double junction baryon stopping. Particularly, we find that the mid-rapidity curvature $\frac{d^2 \Delta v_1^{\rm even} (p-\bar{p})}{dy^2}\vert_{y=0}$ is a robust discriminator of the initial state baryon rapidity profiles. A simultaneous measurement of $\Delta v_1^{\rm even}$ and its curvature at mid-rapidity could constrain both the baryon diffusion strength and the baryon stopping profile, providing access to the physics of baryon stopping in relativistic heavy ion collisions.
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Physics and Society

On the Effects of Decentralized Moderation on Network Robustness and Information Diffusion in Mastodon

Beatriz Arregui-García, Lucio La Cava, Anees Baqir et al. (+3 more)

Decentralized online social networks such as Mastodon distribute moderation power across thousands of independently governed servers, raising fundamental questions about how local block decisions shape global structure and information flow. In this paper, we analyze Mastodon at the instance level by constructing a signed, directed, temporal network in which positive edges aggregate inter-instance follow relationships and negative edges encode daily block actions. Using one year of data, we show that despite continuous moderation activity and changing roles among instances, the network exhibits strong structural stability: signed dyadic motifs and degree distributions display highly persistent dynamics, and aggregated transition matrices satisfy Markovian equilibrium conditions over intermediate time scales. Building on the marked asymmetry between instances that predominantly issue bans and those that are mostly banned, we then study information diffusion on the positive network via a hybrid contagion model that combines simple contagion within groups and complex contagion across groups. We find that information originating in the minority of moderating instances spreads more efficiently, both internally and toward the majority, while the opposite direction is fragile and sensitive to contagion parameters. Echo-chamber effects emerge even in a globally balanced signed network and become stronger under stricter contagion conditions. Together, these results show that decentralized moderation in Mastodon generates a stable macroscopic configuration that both structures and constrains information exchange, effectively isolating norm-violating domains without centralized control.
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All authors Beatriz Arregui-García, Lucio La Cava, Anees Baqir, Andrea Tagarelli, Riccardo Gallotti, Sandro Meloni

Instrumentation and Methods for Astrophysics

Frequency Phase Transfer for Future Millimetre Arrays with Arbitrary Frequency Ratios

Senkhosi Simelane, Athol Kemball and Roger Deane

Non-dispersive tropospheric turbulence-induced phase delays enforce significant, often dominant, limitations to the imaging fidelity and dynamic range in (sub-)millimetre astronomy. Frequency Phase Transfer (FPT), which removes such delays from high-frequency data using simultaneous lower-frequency observations, has become increasingly viable with the advent of shared-optical-path multi-band receivers and is a key motivator of the Event Horizon Telescope Collaboration's ambitions to add 86-GHz and 345-GHz bands alongside its existing 230-GHz band. However, existing FPT algorithms break down for non-integer frequency ratios, leaving jump discontinuities in the residual phases. We introduce a new FPT algorithm, phase-wrap counting (PWC), which works for any frequency ratio and clarifies the nature and source of the jump discontinuities left by previous FPT approaches. Using the newly developed High-frequency Inter-band Transfer of Phase Solutions (HITOPS) software package, we apply PWC to a simulated dual-band observation with the Event Horizon Telescope and demonstrate its effectiveness under realistic atmospheric conditions and thermal noise levels. The method successfully calibrates the 230-GHz phases using the 86-GHz phase solutions, outperforming the conventional phase calibration approach in both coherence and peak flux recovery. This result indicates that PWC has the potential to enable the calibration of the 230-GHz band using the 86-GHz band in future EHT operations.
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High Energy Physics (Phenomenology)

Hard-Region Fermion Self-Energy and Fermion–Photon Vertex in Thermal QED through Two Loops

Ali Hataei

We compute hard-region contributions to the fermion self-energy and the off-shell fermion–photon vertex in massless thermal QED in a covariant \(R_\xi\) gauge. The calculation includes the one-loop next-to-leading-power and two-loop leading-power terms in the expansion in soft external momenta, together with the zero-temperature counterterms required to remove ultraviolet subdivergences. In the real-time formalism, we first derive symmetry constraints on the two-fermion–\(N\)-photon amplitudes, which lead to distinct selection rules in the soft-momentum expansion. The fermion–photon vertex is decomposed into Dirac-vector and axial-vector coefficients. The former satisfies the Ward–Takahashi identity, while the latter is transverse to the photon momentum. These relations are verified at the integrand level. The hard self-energy corrections computed here produce no finite contribution to the fermion damping rate. Our results provide previously unavailable two- and three-point hard-region data for higher-order analyses of fermion mass shifts and inclusive rates, as well as for the construction of a next-to-leading-order fermionic effective action.
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Mathematical Physics · Cross-listed from math.DG

Homogeneity actions, N-manifolds, and the Frobenius theorem

Janusz Grabowski and Asier López-Gordón

This paper is devoted to $\mathbb{N}$-graded supermanifolds $\mathcal{M}$ whose grading is induced by a homogeneity action, i.e., a smooth action $\mathbb{R}\ni t\mapsto h_t$ of the multiplicative monoid of real numbers on $\mathcal{M}$. We show that the map $h_0$ is a smooth retraction onto a submanifold $M=h_0(\mathcal{M})$, and that $h_0:\mathcal{M}\to M$ is a fiber bundle with typical fiber $\mathbb{R}^{m|n}$. Using this homogeneity approach, we obtain a simple proof of a homogeneous version of the Frobenius theorem. If, in addition, $h_{-1}$ acts as the parity operator on $\mathcal{M}$, we provide a geometric characterization equivalent to the recent definition of $\mathbb{N}$-manifolds due to Bursztyn, Cueca, and Mehta in terms of sheaves of graded algebras with prescribed local models. As a consequence, the homogeneous Frobenius theorem for $\mathbb{N}$-manifolds proved by these authors appears as a special case of our more general result.
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Soft Condensed Matter

Unraveling Internal Friction in a Coarse-Grained Protein Model

Carlos Monago, J. A. de la Torre, Rafael Delgado-Buscalioni et al. (+1 more)

Understanding the dynamic behavior of complex biomolecules requires simplified models that not only make computations feasible but also reveal fundamental mechanisms. Coarse-graining (CG) achieves this by grouping atoms into beads, whose stochastic dynamics can be derived using the Mori-Zwanzig formalism, capturing both reversible and irreversible interactions. In liquid, the dissipative bead-bead interactions have so far been restricted to hydrodynamic couplings. However, friction does not only arises from the solvent but notably, from the internal degrees of freedom missing in the CG beads. This leads to an additional ”internal friction” whose relevance is studied in this contribution. By comparing with all-atom molecular dynamics (MD), we neatly show that in order to accurately reproduce the dynamics of a globular protein in water using a coarse-grained (CG) model, not only a precise determination of elastic couplings and the Stokesian self-friction of each bead is required. Critically, the inclusion of internal friction between beads is also necessary for a faithful representation of protein dynamics. We propose to optimize the parameters of the CG model through a self-averaging method that integrates the CG dynamics with an evolution equation for the CG parameters. This approach ensures that selected quantities, such as the radial distribution function and the time correlation of bead velocities, match the corresponding MD values.
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All authors Carlos Monago, J. A. de la Torre, Rafael Delgado-Buscalioni, Pep Español

Materials Science

Connection between the GKSL master equation and the Landauer formula

Misa Nozaki and Takatoshi Fujita

We derive a current formula within the Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) master equation formalism for a non-interacting system, and identify the conditions under which it reduces to the Landauer formula.

Quantum Physics

Rate-2/3 Girth-8 (3,18)-Regular Quantum LDPC Codes from Two-Branch Finite-Field Bases and CPM Lifts

Koki Okada and Kenta Kasai

We construct a rate-$2/3$ quantum low-density parity-check (LDPC) code from a $(3,18)$-regular two-branch finite-field base and a circulant-permutation-matrix (CPM) lift of degree $P=101$. The resulting code is a Calderbank–Shor–Steane (CSS) code with parameters $[[34542,23032,18]]$. Its distance is established by a computer-assisted proof: an explicit nontrivial logical operator gives the upper bound, and a complete symmetry-reduced enumeration excludes every nonzero vector of weight below 18 in both parity-check kernels. We also prove that every affine-in-$t$ CPM lift of the same base satisfying CSS orthogonality has distance at most 18 for every prime lift degree $P>19$. The construction has row weight 18 and column weight 3, and the Tanner graphs of $H_X$ and $H_Z$ separately have girth 8. Decoder experiments with log-likelihood-ratio (LLR) joint belief propagation (BP) and deterministic post-processing show no failures in $10^8$ trials at $p=0.01$, and a finite-length frame error rate (FER) sweep estimates the transition near $p=0.029$.
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Data Analysis and Statistics · Cross-listed from cs.LG

Kolmogorov Arnold networks (KAN) for aerodynamic prediction: a comparison with MLPs and GNNs

Miguel Jaraiz, Fermin Gutierrez, Pablo Yeste et al. (+4 more)

Kolmogorov Arnold networks (KAN) have recently been introduced as a (deep) neural network architecture whose trainable parameters adapt the activation functions, instead of the coefficients of the affine transformations at the core of traditional architectures such as deep multilayer perceptrons (MLPs). This architecture builds on the Kolmogorov-Arnold theorem, which endows it with universal approximation properties. While the advent of KANs has been received with excitement, there is a current debate about the possible KAN supremacy over deep multilayer perceptrons (MLPs) for classic fields such as symbolic regression, generic-purpose machine learning, natural language processing or computer vision. Here we assess the performance of KANs –and its nuanced comparison against MLPs and graph neural networks (GNNs)– in the realm of fluid dynamics surrogate modelling. To that aim, we consider the task of predicting the surface pressure distribution over subsonic and transonic airfoils, a canonical task in aerodynamics. Our results show that KAN models show good performance in predicting the whole pressure coefficients and is able to interpolate across Mach numbers and angles of attack, however its performance is comparable –marginally inferior– to a suitably trained MLP, where best performance is achieved by a GNN at the expense or requiring lengthier training. While the optimal KAN model have typically much lower complexity than MLP and GNN –hence resulting in faster training–, we find that KANs suffer from training instabilities, and their performance is highly dependent on a proper hyperparameter optimisation.
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All authors Miguel Jaraiz, Fermin Gutierrez, Pablo Yeste, Miguel Sánchez-Domínguez, Eusebio Valero, Gonzalo Rubio, Lucas Lacasa

Mathematical Physics

The Ising Model Coupled to 2D Gravity: Critical Partition Function

Maurice Duits, Nathan Hayford and Seung-Yeop Lee

We prove that the differential of the log of the partition function for the $2$-matrix model with quartic interactions converges in a certain double-scaling regime to the differential of the $\boldsymbol{\tau}$-function for the $(3,4)$ string equation. This confirms the convergence of the critical Ising model on random surfaces to the $(3,4)$ topological minimal model, which was stated in the works of Douglas and Shenker, Brézin and Kazakov, and Gross and Migdal. Our analysis is based on a steepest-descent analysis of a Riemann-Hilbert problem associated to a family of biorthogonal polynomials. New features in the matching problem in the construction of local parametrices appear.
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Mesoscale and Nanoscale Physics

Magnetoresistance in chiral systems driven by inter-band spin-orbit coupling

Misa Nozaki and Takatoshi Fujita

Chiral-induced spin selectivity (CISS), in which electrons transmitted through nonmagnetic chiral materials exhibit strong spin-dependent transport, has attracted growing interest for spintronic applications. However, a quantitative understanding of CISS remains elusive, partly because most previous studies rely on single-band models. In this work, we theoretically investigate multi-band effects on magnetoresistance (MR)-CISS, which is typically observed in experiments using magnetic conductive atomic force microscopy. To evaluate the spin polarization in MR-CISS, we simulate the nonequilibrium steady-state current using the Gorini-Kossakowski-Sudarshan-Lindblad master equation. We find that spin polarization exceeding 25% can be achieved for realistic inter-band spin-orbit coupling strengths in the presence of on-site Coulomb interactions. These findings highlight the crucial role of inter-band spin-orbit coupling in the mechanism of CISS.
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Quantum Physics

Efficient foundation decoders for fault-tolerant quantum computing

Ge Yan, Shanchuan Li, Shiyi Xiao et al. (+4 more)

Foundation decoders, a class of high-capacity neural decoders, are leading candidates for fault-tolerant quantum computing, with accurate and efficient decoding at large code distances. However, their construction often faces a steep scaling barrier, as larger code distances rapidly amplify the cost of syndrome generation and neural optimization. To address this bottleneck, here we devise neural transfer unification (NTU), a unified framework for efficient foundation decoders. A central feature of NTU is its ability to align decoding tasks across code distances via algebraic structures shared by scalable code families, which enables knowledge learned on smaller codes to accelerate large-scale decoder training. We instantiate NTU as NTU-Transformer, a transformer-based neural decoder tailored for planar surface codes and bivariate bicycle codes. For planar surface codes under circuit-level noise, NTU-Transformer outperforms correlation-aware matching on the $[\![361,1,19]\!]$ code and further scales to the $[\![625,1,25]\!]$ code, where it exceeds standard matching through transfer adaptation. For the bivariate bicycle code with $[\![72,12,6]\!]$, it surpasses Relay-BP in the low-physical-error regime. These results establish our proposal as a scalable route to amortized cross-distance training of foundation decoders for fault-tolerant quantum processors.
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All authors Ge Yan, Shanchuan Li, Shiyi Xiao, Pengyue Ma, Hanyan Cao, Feng Pan, Yuxuan Du

Cosmology and Nongalactic Astrophysics

Clustering of high-redshift quasars with DESI DR2

M. Charles, P. Martini, A. J. Ross et al. (+46 more)

We present clustering measurements for high-redshift quasars using data from the Dark Energy Spectroscopic Instrument Data Release 2. Our sample consists of quasars with $2.0 < z < 3.5$ in the luminosity range $M_{1450} \leq -19.94$\,mag. We measure the mean quasar bias $b_Q(\bar{z} = 2.48) = 3.61 \pm 0.01$ for the full sample of $\sim 715,000$ quasars and quantify the redshift evolution of quasar bias by dividing the sample into four equal redshift bins. There is strong evolution of the quasar bias with redshift that is well fit by the function $b_Q(z) = a [(1 + z)^2 - 6.565] + b$ with $a=0.230 \pm 0.007$ and $b=2.394 \pm 0.035$, and this fit is also a good match to lower redshift measurements in the literature. This bias evolution is consistent with a characteristic halo mass of $\bar{M}_{\mathrm{h}} \sim 10^{12}\,\mathrm{M_\odot}$ that does not vary significantly with redshift. The inferred duty cycles for quasars in our sample are $f_{\mathrm{duty}} \sim 10^{-2}$, staying mostly constant over redshifts. We investigate the luminosity dependence of quasar clustering by dividing each of our four redshift bins into three luminosity bins. The size of our quasar sample permits the first statistically significant measurement of the luminosity dependence of quasar bias at these redshifts. We measure weak dependence of quasar bias on luminosity at fixed redshift, inconsistent with no dependence, but weaker than predicted by a model in which quasar luminosity is tightly correlated with halo mass. These clustering measurements provide a stringent test for models of active black hole light curves and the black hole-halo connection at high redshift.
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All authors M. Charles, P. Martini, A. J. Ross, D. H. Weinberg, J. Aguilar, S. Ahlen, D. Bianchi, D. Brooks, F. J. Castander, T. Claybaugh, A. Cuceu, A. de la Macorra, P. Doel, S. Ferraro, A. Font-Ribera, J. E. Forero-Romero, S. Gontcho A Gontcho, G. Gutierrez, J. Guy, C. Hahn, H. K. Herrera-Alcantar, K. Honscheid, C. Howlett, M. Ishak, R. Joyce, D. Kirkby, A. Kremin, M. Landriau, L. Le Guillou, M. E. Levi, M. Manera, A. Meisner, R. Miquel, J. Moustakas, A. D. Myers, S. Nadathur, N. Palanque-Delabrouille, W. J. Percival, F. Prada, I. Pérez-Ràfols, G. Rossi, L. Samushia, E. Sanchez, D. Schlegel, M. Schubnell, D. Sprayberry, G. Tarlé, B. A. Weaver, R. Zhou

High Energy Astrophysical Phenomena · Cross-listed from math.NA

An Arbitrary-Lagrangian-Eulerian solver for relativistic detonation waves

Sara Rinaldi, Olindo Zanotti and Michael Dumbser

In this paper we study the dynamics of relativistic detonation waves theoretically and numerically. The reaction is physically accounted for by an extra term in the definition of the total energy density and by an additional equation for the evolution of the mass fraction of the reactant, while leaving formally unmodified the equations of mass and energy-momentum conservation. In this way, the Rankine-Hugoniot relations maintain the same formal structure of the inert version. For the numerical solution we use a finite volume ALE scheme with a second order TVD space-time reconstruction for the homogeneous part of the system, where the mesh velocity is chosen equal to the shock speed, and we combine it through operator splitting with a locally implicit algorithm for the potentially stiff reaction source terms that arise in the equation of the reactant. We furthermore propose a particularly efficient algorithm for the conversion from the conserved to the primitive variables, which for the relativistic Euler equations is known to be nontrivial. Following this approach, we can successfully solve the Zel'dovich-von Neumann-Doering profile of a relativistic detonation wave, up to Lorentz factors of the shock front $\gamma_s\sim 7$. Our analysis allowed us to highlight a new special relativistic effect, which has remained unnoticed so far. While in Newtonian detonations the Zel'dovich pressure jump decreases monotonically with the mass flux through the shock front, in the relativistic case it shows a minimum and then rises monotonically as a function of the mass flux. This may have interesting physical implications on the amount of energy that can be extracted from a relativistic detonation wave.
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Astrophysics of Galaxies

Probing Anomalous Microwave Emission with the Square Kilometre Array

Matías Vidal, Simón Casassus, Roke Cepeda-Arroita et al. (+15 more)

Anomalous microwave emission (AME) represents an excess of radiation in the 10-60 GHz range, distinct from synchrotron, free-free, or thermal dust emission. Although most commonly attributed to electric dipole radiation from rapidly rotating small dust grains (spinning dust), alternative mechanisms such as magnetic dipole emission (MDE) remain plausible. The detection of AME across diverse environments, from diffuse interstellar clouds to protoplanetary disks and external galaxies, suggests that multiple physical processes or carriers may contribute to its origin. Understanding AME is essential for both Galactic astrophysics and cosmology, as it constitutes a significant foreground for cosmic microwave background (CMB) studies, potentially biasing measurements. This chapter reviews current theoretical frameworks and observational evidence for AME, highlighting the key outstanding questions concerning its emission mechanisms, carriers, and polarization properties. We discuss how the Square Kilometre Array Observatory (SKAO), through its unprecedented sensitivity, angular resolution, and frequency coverage, will transform AME studies. SKA observations will enable detailed mapping of AME morphology, precise characterisation of its spectral energy distribution, and the identification of its carriers in Galactic and extragalactic environments. By combining SKA-mid data with higher-frequency observations from ALMA and other facilities such as SPHEREx, it will be possible to disentangle competing models and exploit AME as a diagnostic probe of interstellar grain physics and the small-scale structure of the interstellar medium.
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All authors Matías Vidal, Simón Casassus, Roke Cepeda-Arroita, Miguel Cárcamo, Stuart E. Harper, Thiem Hoang, J. A. Rubiño-Martín, Kieran A. Cleary, Clive Dickinson, R. T. Génova-Santos, Gabriel A. Hoerning, Melis O. Irfan, A. Lazarian, Hauyu Baobab Liu, Eric J. Murphy, M. W. Peel, Nathalie Ysard, Zheng Zhang

Plasma Physics

A possible approach to overcome the saturation of the neutron yield in a Plasma Focus and to achieve breakeven

Andrea Di Vita

Saturation of the neutron yield with increasing energy of the condenser bank in a Plasma Focus led to the shutdown of PF research focussed on controlled nuclear fusion in the past. We review available models of saturation and develop further the model of Lee S., Applied Phys. Lett. 95, 151503, 2009. This model relies on the well-known and generally accepted model of Lee S., J. Fusion Energy 2014, 33, 319 of Plasma Focus discharges and describes saturation in terms of the dynamic resistance, i.e. the rate of change of PF inductance due to the motion of the plasma sheath during rundown. A model of this sheath discussed in Di Vita A., J. Plasma Physics, 1993, 50, 1 shows that its spontaneous filamentation rules the dynamic resistance, spoiling the power supply from the condenser bank to the plasma at the values of condenser bank energy above 0.5 MJ values which are relevant to a fusion reactor. Together, these two models lead to the conclusion that suppression of such filamentation prevents saturation, multiplies the PF drive parameter by a factor 3 at least and allows breakeven in a 224 kV, 10 MJ Plasma Focus working with DT. We can suppress filamentation by superimposing a radial magnetic field to the interelectrode region of the Plasma Focus where rundown occurs. A conservative estimate shows that a 1.4 T radial magnetic field is enough to suppress many known filamentation instabilities. Suitably located magnets can generate this field. Their layout resembles the layout of the sources of radial magnetic field in the cylindrical geometry of a Hall thruster for space propulsion. For high temperature superconducting magnets, the required current density is too small to trigger quenching.
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Earth and Planetary Astrophysics

The ESO SupJup Survey XI. Atmospheric properties of six isolated M- and L-type dwarfs with CRIRES+

C. R. Malcolm, N. Grasser, I. A. G. Snellen et al. (+9 more)

The distinct formation pathways of brown dwarfs and giant exoplanets may be encoded in their atmospheric composition. We present atmospheric retrievals for six isolated brown dwarfs of spectral types M7-L2.5 from the ESO SupJup Survey, aiming to constrain their thermal structures, chemical compositions, and isotope ratios. We analyse CRIRES+ K-band spectra, coupling the radiative transfer code petitRADTRANS with the nested sampling algorithm PyMultiNest under both free and equilibrium chemistry frameworks. The L0 dwarf 2MASS J09532126-1014205 emerges as one of the fastest-rotating ultracool dwarfs known, with $v\sin i = 85.9\pm0.5$ km s$^{-1}$. H$_2$O is strongly detected in all six targets and $^{12}$CO in five, with a marginal $^{12}$CO detection in the ultra-fast L0 rotator consistent with severe rotational broadening. $^{13}$CO is significantly detected in DENIS J060852.8-275358 and tentatively in three further targets. Retrieved compositions are consistent with isolated brown dwarfs: near-solar C/O ratios ($0.51$-$0.63$), predominantly near-solar metallicities, and $^{12}$C/$^{13}$C ratios of ~91-155, at or above the local ISM value, with constraints for the two fastest rotators resting on the spectral fit but not corroborated by a $^{13}$CO cross-correlation peak. The M7 dwarf 2MASS J04341527+2250309 shows discrepant gravity and metallicity values between chemistry frameworks. Apparent H$_2^{18}$O constraints for two targets are found to be spurious, and their H$_2^{(16)}$O/H$_2^{18}$O ratios are presented as lower limits, demonstrating the importance of cross-correlation validation for minor species detections. The near-solar C/O ratios and metallicities, with $^{12}$C/$^{13}$C ratios at or above the ISM value, support a molecular cloud fragmentation origin for the sample. The agreement of $^{12}$C/$^{13}$C between chemistry frameworks supports the robustness of these ratios.
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All authors C. R. Malcolm, N. Grasser, I. A. G. Snellen, S. de Regt, D. González Picos, Y. Zhang, T. Stolker, S. Gandhi, P. Mollière, E. Nasedkin, R. Landman, A. Y. Kesseli

Quantum Physics

Witness expansion: A unified framework for analytical and measurable mixed-state resource detection

Yifan Tang, Chengkai Zhu, Yuzhen Zhang et al. (+6 more)

Quantum information science aims to harness different kinds of quantum resources to accomplish specific information-processing tasks. These resources also play an increasingly important role in addressing fundamental questions concerning quantum phases and dynamics. Therefore, developing powerful and practical methods for identifying and detecting quantum resources is of great significance, with applications ranging from benchmarking quantum devices to understanding the fundamental structure of quantum theory. In this work, we propose witness expansion, a unified framework for constructing nonlinear criteria for detecting quantum resources that are associated with a well-defined group of free unitaries. These criteria apply to both pure and mixed quantum states and are based on polynomial functions of the target state, which can be estimated experimentally using multiple copies of the state and evaluated analytically in certain physical models. We show how several well-known resource-detection quantities naturally emerge from our framework, including the $l_2$ norm of coherence, partial-transpose moments for entanglement, stabilizer entropy for nonstabilizerness (quantum magic), and fermionic antiflatness for fermionic non-Gaussianity. Beyond recovering these existing structures, our framework also yields new criteria for detecting qubit and qudit magic states, substantially enhancing witness-based detection capabilities. In addition, it gives, to the best of our knowledge, the first analytical criterion for detecting mixed-state fermionic non-Gaussianity with respect to the convex hull of pure fermionic Gaussian states that remains nontrivial for arbitrary numbers of qubits, demonstrating the broad applicability and conceptual unifying power of the framework.
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All authors Yifan Tang, Chengkai Zhu, Yuzhen Zhang, Jens Eisert, Zi-Wen Liu, Ingo Roth, Otfried Gühne, Xin Wang, Zhenhuan Liu

Mesoscale and Nanoscale Physics

Low-energy model for doped graphene nanoribbons

J. Ferrer, A. García-Fuente, Y. Yang et al. (+2 more)

We analyse in this article the many-body behavior of free-standing doped graphene nanoribbons where the chemical potential lies inside the bulk single-particle bands. We perform an exact mapping from both an extended and an on-site Hubbard model of the ribbons to a Kanamori model, which includes ferromagnetic exchange and pair-hopping interactions. We determine the resulting Coulomb matrix elements analytically, and identify their scaling behavior as a function of ribbon width and length. We propose a low-energy version of the Kanamori Hamiltonian to address the response of the ribbons to external fields, with a view to their use as transport channels in nanoelectronics. We find that the model and the proposed ribbon parameters can produce open-shell, high-spin many-body states that can lead to shell- and spin-blockade responses.
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All authors J. Ferrer, A. García-Fuente, Y. Yang, S. Volosheniuk, H.S.J. van der Zant

High Energy Physics (Theory)

Approximating Feynman integrals using complete monotonicity and Stieltjes properties

Sara Ditsch, Johannes M. Henn and Prashanth Raman

We present two novel approaches for the numerical evaluation of Feynman integrals based on their universal analytic properties related to positivity, namely complete monotonicity (CM) and Stieltjes properties. Building on recent results, we exploit the fact that scalar Feynman integrals in the Euclidean region are completely monotonic functions, meaning that all their derivatives have a fixed sign. Building on this observation, the CM bootstrap allows one to reconstruct integrals from differential equations without explicit boundary data, yielding rigorous bounds. The second method is based on a refinement of CM. We prove that Feynman integrals, within a certain range of parameters, are not only CM but in fact Stieltjes functions. This enables the use of Padé approximants with provable convergence properties in the cut complex plane, providing an efficient method for analytic continuation and fast numerical evaluation. We illustrate the method with simple examples such as the massive bubble integral and discuss applications to multi-loop integrals, including the 20-loop banana integral. Finally, we comment on a number of extensions of these novel avenues for computing Feynman integrals.
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Optics

Neural Networks for Inverse Design of Cascaded-Mode Near-Field Landscapes

Wannes Luts De Martelaere, Joeri Lenaerts and Vincent Ginis

Structuring optical near-fields is important for applications in microscopy and nanoparticle manipulation. Traditionally, near-fields are structured using antenna nanostructures that locally convert propagating far-fields into bound near-fields. Recently, a remote structuring approach was proposed using cascaded mode interference in a multimode waveguide. However, determining the complex coefficients of the optimal modal combination needed to obtain specific near-fields remains a challenge. We address this inverse design problem using artificial neural networks. We model the relationship between the design parameters and near-field landscapes using multilayer neural networks. After training, these networks are used for gradient-based optimization to reconstruct target near-field profiles. We implement this methodology to design longitudinal and lateral field variations. Our approach designs simple and complex longitudinal landscapes, demonstrating accurate prediction and flexibility. Lateral field reconstruction is more challenging but improved with training data selection and augmentation. This work establishes deep learning as an efficient and scalable framework for cascaded-mode near-field inverse design.
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Astrophysics of Galaxies

Start of orbit librations and the bar growth timescale

Ekaterina N. Podzolkova and Anna M. Melnik

We study a dynamical model of the Galaxy with an analytical bar that reproduces the radial velocity $V_R$ profiles as a function of the Galactocentric distance $R$ obtained from the Gaia DR3 data. The model radial velocity profiles show a periodic increase in $V_R$ caused by orbits trapped into libration near the outer Lindblad resonance (OLR). To determine the moment when the librations start, we built a set of additional models differing only in the bar growth time $T_g$. The temporal dependences of the radial velocity $V_R$ in the models with different $T_g$ retain their shape but are shifted relative to each other in time $t$. The shift providing the best agreement between the model dependences is proportional to $T_g$ with the coefficient $k = 0.54 \pm 0.02$. Orbit librations do not start when the bar reaches its full strength, but when it attains only 54% of its maximum strength. Since the maximum bar strength in the models is $Q_b = 0.314$, the librations start when the bar strength reaches $Q_b = 0.170$.
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