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Physics

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Friday 26 June

High Energy Astrophysical Phenomena

Dual AGN and Multiple SMBH Systems in the Era of SKAO

Q. D'Amato, L. Cui, R. Deane et al. (+23 more)

We present a radio-oriented review of current strategies for the detection and characterization of dual active galactic nuclei (DAGN) and supermassive black hole binaries (SMBHBs), emphasizing the crucial role of radio interferometry in advancing this field. We discuss how high-resolution radio imaging - particularly through very long baseline interferometry (VLBI) - provides a unique, dust-unbiased tool to identify multiple accreting SMBHs, disentangle AGN-related emission from star formation, and trace components from tens of kpc to sub-parsec scales. We summarize current observational limitations, such as insufficient sensitivity-resolution combination and area coverage. We then outline how the SKAO will overcome these constraints through its unprecedented combination of sensitivity, survey speed, imaging fidelity and angular resolution, enabling the discovery and characterization of dual and binary SMBHs from the nearby Universe to the epoch of reionization. Several science cases are presented, including radio follow-ups of optical/infrared-selected DAGN, direct blind radio selection of DAGN, studies of compact bound SMBHBs, and the link between SMBHB orbital evolution and low-frequency gravitational wave emission. We further emphasize the synergy between SKAO observations and modern and upcoming facilities such as the James Webb and Euclid space telescopes, Rubin Observatory, and gravitational wave detectors including the Laser Interferometer Space Antenna and pulsar timing arrays. These combined capabilities will allow SKAO to enable the first comprehensive radio census of dual and binary SMBH systems, bridge the gap between electromagnetic and gravitational wave observations, and provide a statistically significant view of SMBH pairing, accretion, and merger-driven feedback throughout cosmic history.
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All authors Q. D'Amato, L. Cui, R. Deane, S. Komossa, C. Pillay, A. Tripathi, P. Kharb, H. Guo, S. Nandi, K. Rubinur, S. Anton, T. An, S. Bonoli, N. Chang, R. Dave, A. De Rosa, M. Habouzit, F. Mannucci, I. Prandoni, P. Severgnini, M. Scialpi, C. Spingola, C. Vignali, W. Xu, X. Yan, Y. Zhang

High Energy Physics (Theory)

Orientifolds of Gepner models without Kähler moduli

Miguel Morros, Johannes Walcher and Qi You

One of the main challenges in string theory Calabi-Yau compactifications to four dimensions is the stabilization of the massless complex structure and Kähler moduli. In type IIB string theory, complex structure moduli can be stabilized perturbatively by turning on fluxes on the internal space, while there is no perturbative mechanism for Kähler moduli stabilization. Since every Calabi-Yau manifold has at least one Kähler modulus (the overall volume), there is no hope to stabilize all moduli perturbatively. A way out is given by Landau-Ginzburg/Gepner models string vacua which can have no Kähler moduli. To identify the most promising candidates for fully stabilized perturbative string vacua, we provide an exhaustive list of Landau-Ginzburg orientifold models with no Kähler moduli, and compute for each model the number of complex structure moduli together with the tadpole charge. From this, we can identify which of these models are genuine candidates for phenomenologically relevant string vacua.
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Strongly Correlated Electrons

Vortex-enhanced photovoltaic current in disordered topological materials

Pavlo Sukhachov, Penghao Zhu, Ella Banyas et al. (+2 more)

In disordered topological materials, real-space crystalline defects interplay with momentum-space wave function singularities to enhance the bulk photovoltaic current. What's singular is the interband Berry phase, or equivalently the phase of the optical dipole matrix element, which has a vortex structure in momentum space. Such optical vorticity is guaranteed to exist in all topological materials associated with nontrivial Chern numbers. These vortices enhance electron-impurity skew scattering, which manifests as a ballistic photovoltaic current that is sensitive to (a) the topological material class, (b) the symmetry class of crystalline defects, and (c) the light polarization. This sensitivity manifests in two ways: firstly, by (a-c)-dependent frequency exponents for the photovoltaic current $\propto \omega^{\text{exponent}}$ in topological semimetals, with $\omega$ the frequency of the light source. Secondly, by (a-c)-dependent constraints of the bulk photovoltaic tensor, which are explainable only by emergent, magnetic symmetries of time-reversal-invariant topological materials. These ideas are concretized by case studies on multifold fermions, 3D $m$-order Weyl semimetals and 2D $n$-order Dirac systems, which include $n$-layer rhombohedral graphene, transition metal dichalcogenides, and topological surface states. Theoretical guidance is provided for a tri-pronged experimental program that combines frequency-tuned photoconductivity measurements, defect characterization and defect engineering.
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All authors Pavlo Sukhachov, Penghao Zhu, Ella Banyas, Liang Z. Tan, A. Alexandradinata

Materials Science

Microscopic and macroscopic characterization: MBE-grown versus sputter-deposited Au/Co/Au thin films for CISS and MIPAC effect studies

Lokesh Rasabathina, Thi Ngoc Ha Nguyen, Aleksandr Kazimir et al. (+12 more)

Chirality-induced spin selectivity (CISS) enables spin-dependent transport at chiral molecule/Au(111) interfaces and is used in spintronics when combined with ferromagnetic thin films in spin-valve-type hybrids. However, the influence of substrate microstructure on CISS and the related magnetization induced by the proximity of adsorbed chiral molecules (MIPAC) effect is still not well understood. In this study, we compare the effects of the adsorption of L-chiral alpha-helical alanine-rich peptides on Au/Co/Au ferromagnetic thin films fabricated by molecular beam epitaxy (MBE) and magnetron sputtering. X-ray reflectivity and X-ray diffraction show sharper interfaces and a narrower Au(111) rocking-curve width for the MBE-grown sample. However, atomic force microscopy and scanning tunneling microscopy images reveal that both sample types have locally smooth Au(111) surface regions suitable for peptide adsorption, despite clear differences in larger-scale morphology. Microscopic scanning tunneling spectroscopy after peptide exposure yields similar magnetization-direction-dependent tunneling currents in both sample types, confirming a similar magnitude CISS effect on the molecular scale. In contrast, macroscopic magneto-optical Kerr effect hysteresis loops and effect microscopy reveals that only sputter-deposited samples show slight coercivity enhancements and a consistent reduction in domain wall velocity after peptide exposure. These results suggest that microscopic CISS signatures are robust for both sample types, whereas macroscopic MIPAC-type magnetic responses are more sensitive to the substrate microstructure.
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All authors Lokesh Rasabathina, Thi Ngoc Ha Nguyen, Aleksandr Kazimir, Rico Ehrler, Julia Krone, Franziska Schölzel, Zihao Liu, Peter Heinig, Markus Gößler, Irene Coin, Christina Lamers, Georgeta Salvan, Lech Tomasz Baczewski, Christoph Tegenkamp, Olav Hellwig

High Energy Astrophysical Phenomena

Twin Peaks: Resolving Features in the Binary Black Hole Mass Function with COSMIC-METISSE

Duncan B. Maclean, Poojan Agrawal, Katelyn Breivik et al. (+4 more)

Gravitational waves from inspiraling binary black holes (BBHs) provide insights into the lives and deaths of massive stars. Population synthesis allows us to model these binaries through isolated binary evolution, but its predictive power is limited by difficulties in varying the stellar models and their associated uncertainties. We present a new grid of stellar tracks computed with the open-source stellar evolution code MESA, spanning metallicities $10^{-3} \le Z/Z_{\odot} \le 7$. We vary two stellar physics parameters: wind-driven mass loss and the convective boundary mixing (CBM) mechanism. We pair these models with the Method of Interpolation for Single Stellar Evolution (METISSE) and binary population synthesis code COSMIC to obtain synthetic populations of merging BBHs in the local Universe. We find a maximum in the primary mass spectrum near $10M_\odot$ which in most model variations is composed of two sub-populations at $\approx8M_{\odot}$ and $\approx13 M_\odot$, with the higher-mass population dominated by BBHs whose progenitors underwent a mass ratio reversal (MRR). This population also suggests an anticorrelation between higher primary masses and mass ratio, as BBHs with $m_1\gtrapprox10M_\odot$ preferentially undergo MRR and prefer a final mass ratio of $q\approx0.7$. However, the location and relative strength of these two sub-populations is sensitive to our assumed stellar physics: varying both the wind and CBM treatments can merge the MRR and non-MRR populations into a single peak near $9M_\odot$. Variations in our stellar tracks, especially CBM, lead to a factor of $\approx6$ difference in the rate, primarily due to modulation of the common envelope formation channel.
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All authors Duncan B. Maclean, Poojan Agrawal, Katelyn Breivik, Alexandra G. Guerrero, Michael Zevin, Mathieu Renzo, Carl L. Rodriguez

Quantum Physics

Dissipative Effects in Transmission Line Analogues of Hawking Radiation

Elián Urtubey, Fernando C. Lombardo and Paula I. Villar

Hawking radiation is a fundamental result of quantum field theory in curved spacetime, yet its direct observation remains beyond current experimental capabilities. Circuit quantum electrodynamics provides a practical platform for realizing analogue systems where Hawking-like radiation may be studied under controlled laboratory conditions. In this work, we analyze two superconducting-circuit analogues of Schwarzschild black holes: a tunable dc-SQUID transmission line and a SNAIL-based transmission line supporting solitonic solutions of the KdV equation. We investigate the conditions under which these architectures can generate an observable Hawking temperature and study the impact of dissipation and thermal noise using an open quantum systems approach. To assess the observability of the Hawking signal, we propose complementing particle number measurements with estimates of the Hilbert-Schmidt distance to the thermal bath. Our analysis establishes practical detectability thresholds and shows that Hawking temperatures above approximately 73 mK remain distinguishable under realistic experimental conditions. While the tunable transmission line architecture can reach temperatures of about 113 mK and therefore appears more viable, the solitonic model requires further optimization and more demanding experimental conditions.
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Solar and Stellar Astrophysics

Euclid: The convective-transition gap of 47 Tuc

M. Libralato, M. Griggio, R. Gerasimov et al. (+140 more)

We report the first detection of the `convective-transition gap' (also known as `M-dwarf gap') in the globular cluster 47 Tuc (NGC 104) thanks to Euclid data. This feature, linked to a change in the physical properties of late-type dwarfs, has remained elusive, with only two detections so far. Leveraging the large number of stars, high resolution, and photometric precision enabled by Euclid, we detect a statistically significant, sharp discontinuity in the main-sequence luminosity function of 47 Tuc at $I_{\rm E} \approx 22.9$, which we identify as the convective-transition gap. We compare the observed properties of the gap in 47 Tuc with theoretical models, showing how the gap can be a powerful diagnostic to probe the internal chemical structure of globular clusters, and their multiple stellar populations. Following its initial discovery in the metal-poor cluster NGC 6397, the identification of a convective gap in the metal-rich 47 Tuc suggests that this feature might be more general than previously thought. These results demonstrate that Euclid can be transformative well beyond cosmology, with impact across multiple areas of astrophysics, including resolved stellar populations.
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All authors M. Libralato, M. Griggio, R. Gerasimov, L. R. Bedin, I. McDonald, B. Altieri, J. Anderson, F. Annibali, E. Balbinot, G. Battaglia, A. Bellini, P. Casenove, J.-C. Cuillandre, E. Dalessandro, A. M. N. Ferguson, H. R. A. Jones, K. Kuijken, F. Z. Majidi, D. Massari, A. Mohandasan, F. Niederhofer, G. Polenta, J. D. Sakowska, F. Soldano, C. Zerbinati, S. Andreon, N. Auricchio, H. Aussel, C. Baccigalupi, M. Baldi, A. Balestra, P. Battaglia, A. Biviano, E. Branchini, M. Brescia, S. Camera, V. Capobianco, C. Carbone, J. Carretero, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, M. Cropper, H. Degaudenzi, G. De Lucia, H. Dole, F. Dubath, X. Dupac, M. Farina, R. Farinelli, F. Faustini, S. Ferriol, M. Frailis, E. Franceschi, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, S. V. H. Haugan, H. Hoekstra, W. Holmes, I. M. Hook, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, S. Kermiche, A. Kiessling, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, E. Medinaceli, S. Mei, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, L. Moscardini, R. Nakajima, R. C. Nichol, S.-M. Niemi, C. Padilla, S. Paltani, F. Pasian, W. J. Percival, V. Pettorino, M. Poncet, L. A. Popa, F. Raison, A. Renzi, J. Rhodes, G. Riccio, F. Rizzo, E. Romelli, M. Roncarelli, R. Saglia, Z. Sakr, D. Sapone, M. Schirmer, P. Schneider, T. Schrabback, A. Secroun, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, L. Stanco, P. Tallada-Crespí, A. N. Taylor, I. Tereno, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, J. Valiviita, T. Vassallo, Y. Wang, J. Weller, D. Scott

Biological Physics

Effect of environmental variation on the benefits of learning

Xiao Zhou and BingKan Xue

Signal recognition plays a critical role in species interactions and can be enhanced by learning signal characteristics through experience. In brood parasitism, host species may use visual cues to recognize and reject parasite eggs from their nests; because egg appearances vary within and between host individuals, a host can improve recognition by learning a tailored template of its own eggs. Nevertheless, constitutive and induced costs of learning may inhibit an extended learning period. We use a simple model of signal detection and learning to study how the benefits of learning are affected by different sources of variation in the learning signal. We find that phenotypic variation in egg appearances within a host hinders learning by adding noise to the signals, whereas genotypic variation between individuals promotes learning by carrying more information in the signals. Moreover, we consider environmental variation that can cause egg appearances to fluctuate across clutches over time. We find that such environmental variation reduces the fitness of learning hosts by distorting the signals, creating an effective cost that can offset the benefits of learning. Our results imply that learning or even a brief period of imprinting may be evolutionarily disfavored in homogeneous populations and variable environments.
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Cosmology and Nongalactic Astrophysics

Reheating matters: Starobinsky inflation in light of joint CMB+BAO results and gravitational-wave forecasts

Gláuber C. Dorsch, Lucas P. C. Leão, Lucas M. B. Alves et al. (+2 more)

It has been noted in the literature that, if post-inflationary reheating is dominated by a stiff fluid with equation of state (EoS) $p>\rho/3$, then the predictions of Starobinsky inflation for the scalar spectral index could be made to agree with measurements from the combined CMB+BAO datasets performed by the Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT) collaborations. However, a side-effect of such a stiff epoch is the blue-tilting of the primordial gravitational-wave (GW) spectrum. In this work, we explore the observational consequences of this blue-tilting in three scenarios: (i) a purely stiff-dominated reheating, (ii) a more realistic case where reheating is first dominated by a matter-like fluid (corresponding to inflaton oscillations around the bottom of a quadratic potential well) later followed by a stiff epoch, and (iii) a case analogous to the previous one, but with an earlier radiation-dominated instead of matter-dominated epoch. We show that in all cases the $1\sigma$ region allowed by recent CMB+BAO data is already excluded by constraints on the amount of radiation present during Big Bang Nucleosynthesis (BBN). Moreover, in a considerable fraction of the remaining $2\sigma$ region we find that the blue-tilting would be severe enough to make the primordial spectrum detectable in future interferometers such as Einstein Telescope, LISA, DECIGO, and BBO, thus rendering these scenarios testable by these experiments.
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All authors Gláuber C. Dorsch, Lucas P. C. Leão, Lucas M. B. Alves, Luiz C. A. Miranda, Beatriz M. D. Sena

Cosmology and Nongalactic Astrophysics

A hierarchical Bayesian framework for cosmology using Type 1 AGN variability

Júlia Laguna-Miralles, Vasily Belokurov and Miles Cranmer

Independent luminosity-distance probes beyond the Type Ia supernova range are needed to test cosmic expansion at high redshift. Type 1 AGN are abundant at \(z>2\), but their use for cosmology requires standardizable observables with controlled scatter, redshift dependence, and measurement uncertainty. We present a hierarchical Bayesian framework for cosmology using AGN variability, based on the empirical anti-correlation between optical/UV variability amplitude and luminosity. The method targets the moderate-baseline regime of current wide-field time-domain surveys, where individual light curves cannot typically identify the full long-timescale stochastic process, but can constrain finite-window brightness and short-lag variability. Each light curve is fitted independently to obtain posterior samples of these summaries, which are then importance-reweighted under a population model relating variability to luminosity, rest-frame wavelength, intrinsic scatter, and the assumed distance-redshift relation. This framework propagates object-level uncertainty while avoiding repeated light-curve likelihood evaluations during cosmological inference, making catalogue-scale analyses feasible. Using Gaia DR3-like G-band simulations matched to real Gaia cadences, noise properties, and quality cuts, we show that finite-baseline light curves are more robustly summarized by window-averaged brightness and short-lag variability than by the separate long-timescale parameters of stochastic models. End-to-end closure tests recover the injected variability-luminosity relation, intrinsic scatter, and distance-redshift parameters up to the expected calibration degeneracies. This Gaia G-band analysis establishes a proof of concept for AGN-variability distances in the moderate-baseline survey regime, with the main gains expected from Gaia DR4, ZTF, DESI-selected AGN samples, and Rubin/LSST-era data.
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High Energy Physics (Phenomenology)

New Energy-Loss Constraints on Dark Sectors from Deeply Inelastic Scattering with Initial State Radiation

Justin Cammarota, John Carlton and Susan Gardner

We employ the joint QED and QCD factorization of deeply inelastic, electron-proton scattering with generic initial state radiation to probe the possibility of exotic particle emission – i.e., of weakly coupled particles originating from a dark or hidden sector – through anomalous energy loss. We leverage this possibility through the consideration of phase-space-limited kinematic regions, for which the emission of an additional, undetected particle can particularly impact the associated cross-section. In this first paper, as a proof of principle, we focus on radiation from the incoming electron, considering the modification of the lepton distribution function from the emission of particles, that could have spin of up to 2 and various, well-motivated electron couplings. We illustrate the sensitivity of our approach through the computation of the modified cross-sections for the emission of MeV-GeV mass-scale, spin 0 particles in kinematics chosen for their sensitivity to initial state electron radiation and suitable to the forward-backward detection sensitivity of the ePIC detector at the EIC.
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High Energy Astrophysical Phenomena

Stochastic Variability of Binary Accretion

Akhil Nair and Jonathan Zrake

We measure the power spectral density (PSD) of the accretion rate time series in an unequal mass (q = 0.2) binary surrounded by a circumbinary gas disk, using very high-resolution 2D hydrodynamics simulations. Our aim is to identify new signposts of supermassive black hole (SMBH) binaries in active galactic nuclei (AGN), based on the shape of the continuum PSD, to complement well-studied line features in the PSD (periodicities). We find that the continuum PSD is a broken power-law, transitioning from flat (white noise) to a slope of -4 at a break frequency generically ~5 times the binary orbital frequency. This form is expected when (a) delivery of gas from the circumbinary disk to the individual "minidisks" is a damped random walk with correlation time equal to binary orbital period and (b) the minidisks function as low-pass filters acting at the Kepler frequency of the outer edge of the smaller black hole's minidisk; we show numerical evidence for both. The broken power-law PSD is attained in a limit where the secondary black hole is much smaller than its minidisk, realized numerically by a sufficiently small "sink" region; larger sinks lead to excess high-frequency noise seen as accretion rate spikes, and we argue these should be regarded as artificial when the black holes themselves are smaller than the sink regions. The broken power-law PSD is reminiscent of stochastic variability in ordinary AGN, inviting the conjecture that canonical AGN variability could result from widespread binarity, however pulsar timing experiments may exclude this possibility.
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High Energy Physics (Phenomenology)

Defining a Minimum Resolution for Unbinned Analyses

Manuel Szewc

Collider analyses combine rigorous statistical techniques with state-of-the-art Machine Learning models. However, when the latter are used directly to estimate the likelihood function of the background, hard to quantify systematic effects may bias the estimation of the relevant signal parameters. To address this problem, we present the Minimum Resolution Likelihood (MRL) method, which defines a Fiducial Signal Region that aims to turn systematic effects into statistical uncertainties. We show with examples that the resulting signal strength estimation has a reduced bias, with the effect depending on the sample size and type of signal considered. We consider both toy examples and a realistic application based on the HI-SIGMA technique applied to di-Higgs searches.
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Astrophysics of Galaxies

Stellar discs and intermediate-mass black holes in galactic nuclei I. Fragmenting the disc in an isotropic stellar potential

Taras Panamarev, Xiang Zou and Bence Kocsis

The origin of the complex orbital structure of young massive stars at the Galactic centre remains an open question. If these stars formed in a single episode from a gaseous accretion disc, they may initially have constituted a single, coherently rotating stellar disc. We investigate whether perturbations from an unseen intermediate-mass black hole (IMBH) could fragment and/or disrupt such a disc into the multiple orbital components observed today. First, we derive a theoretical criterion for when and where the IMBH's torque overcomes the disc's self-torque and tears it apart. We then test this picture with direct $N$-body simulations of a stellar disc interacting with an inclined IMBH around a central supermassive black hole. We find that the outcome depends strongly on the IMBH's orbit and mass. A prograde IMBH rapidly aligns with the stellar disc, while a massive retrograde IMBH ($m_{\bullet} \simeq 0.67\,M_{\rm d}$) anti-aligns relative to the radially overlapping stars and efficiently fragments the original disc into three components in angular-momentum space: an inner disc, a misaligned overlapping region, and an unperturbed outer disc. The IMBH also excites eccentricities in the overlapping region, driving stars away from initially circular orbits. These features emerge for an IMBH mass of $2000\,{\rm M}_{\odot}$ and a disc mass of $3000\,{\rm M}_{\odot}$ within 10–20 Myr, a timescale comparable to the age of the young Galactic centre stellar population, and provide a plausible explanation for the observed multiple orbital planes, warped geometry, and broad eccentricity distribution.
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High Energy Physics (Phenomenology)

Polarization interference in exclusive $V+$jets at all orders in $\alpha_s$

Trina Basu and Richard Ruiz

Using new methods for computing helicity amplitudes with intermediate helicity-polarized gauge bosons, we revisit the transverse-longitudinal polarization interference in the $pp\to V+{\rm jets}$ process for $V=\gamma^*,Z^{(*)},W^{(*)}$ decaying to massless leptons. At each order of the strong coupling constant $\alpha_s$ and remaining exclusive with respect to jet kinematics, we show that the polarization interference in $\gamma^*\to\ell^+\ell^-$ vanishes after phase-space integration over the kinematics of $\ell^\pm$, thereby extending well-known results for the inclusive process. Due to parity violation, cancellations are softened for the $W$ and $Z$ bosons. We give a simple formula to account for fiducial cuts. We comment on the implications for multiboson processes, and the applicability of our results to chiral gauge bosons in new physics scenarios and to polarization measurements of weak bosons in heavy ion collisions.
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Strongly Correlated Electrons

Monotonic and non-Nonmonotonic Impurity Entropy flows in a $\mathscr{PT}$-Symmetric Kondo Model

Pradip Kattel, Abay Zhakenov and Natan Andrei

Quantum impurity models provide a paradigmatic setting for studying Kondo screening, boundary criticality, and impurity entropy. While these phenomena are well understood in unitary systems, their fate in non-Hermitian many-body settings remains largely unexplored. We study a $\mathscr{PT}$-symmetric quantum impurity model consisting of a unitary SU(2)$_1$ Wess–Zumino–Witten bulk attached to two impurity spins through complex-conjugate Kondo couplings. Using an integrable lattice realization solved by the Bethe Ansatz and benchmarked against finite-temperature matrix-product-state calculations, we determine the impurity free energy, entropy, and the corresponding $g$-function. We identify three distinct impurity phases. In the Kondo-screened phase, the spectrum remains real and the impurity entropy decreases monotonically from $\ln 4$ in the ultraviolet to $0$. Remarkably, this monotonic flow persists despite the nonunitary boundary interaction, beyond the standard domain of the $g$-theorem. The Yu–Shiba–Rusinov phase instead exhibits spontaneous $\mathscr{PT}$-symmetry breaking and loss of boundary conformal invariance, while the local-moment phase displays cyclic renormalization-group flow, with identical impurity entropy and $g$-value in the ultraviolet and infrared limits.
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High Energy Physics (Phenomenology)

Soft Contributions Stabilize NNLO QCD Corrections to Quarkonium Production and Decay

Luca Maxia, Hua-Sheng Shao, Lukas Simon et al. (+1 more)

Next-to-next-to-leading order (NNLO) QCD corrections to quarkonium production and decay are known to exhibit perturbative instabilities within non-relativistic QCD. We identify the origin of this problem and propose a simple remedy. Applying our approach to $S$-wave color-singlet quarkonium processes, we achieve substantially improved perturbative convergence and agreement with experimental data.
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All authors Luca Maxia, Hua-Sheng Shao, Lukas Simon, Guoxing Wang

Instrumentation and Methods for Astrophysics

The Role of Artificial Intelligence in the SKA Era

Philipp Denzel, Frank-Peter Schilling and Elena Gavagnin

The Square Kilometre Array Observatory (SKAO) will usher in an era of unprecedented data complexity and scientific opportunity in radio astronomy, producing petabyte-scale datasets and terabit-per-second streams that challenge traditional analysis paradigms. Artificial Intelligence (AI) stands at the forefront of this transformation, offering scalable, adaptive solutions to the most pressing problems in radio astronomy and astrophysics. This chapter explores the pivotal role of AI in the SKA era, from real-time operations to scientific discovery. We examine how deep learning models enable automated source detection, radio-frequency interference mitigation, anomaly detection, and parameter inference, while generative approaches accelerate sky simulations, calibration, and imaging. Reinforcement learning promises dynamic scheduling and autonomous system control, and federated learning could address the distributed nature of SKA data. Beyond performance, we emphasize the necessity of explainability, uncertainty quantification, and physics-informed inductive biases to ensure scientific integrity. By mapping SKAO's core challenges - data volume, complexity, and interpretability - onto modern AI methodologies, we review how deep learning, self-supervised frameworks, and probabilistic models can unlock new frontiers in cosmology, galaxy evolution, and time-domain astrophysics. AI is not merely an automation tool for coping with scale. It is a catalyst for discovery, redefining how we observe, model, and understand the Universe.
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High Energy Physics (Phenomenology)

Propagating data noise through the fit: the Monte Carlo replica distribution

Mark N. Costantini

The Monte Carlo (MC) replica method quantifies parameter uncertainties in global fits of parton distribution functions (PDFs) and Standard Model Effective Field Theory (SMEFT) Wilson coefficients by fitting a model to many noise-perturbed copies of the data and taking the empirical distribution of the best-fit parameters as the uncertainty. The method reproduces the Bayesian posterior exactly only when the model is linear in its parameters, and departs from it in the nonlinear case. We derive the leading-order distribution the method produces and compare it with the Laplace approximation of the Bayesian posterior: the two differ by a single computable matrix, the residual-weighted Hessian of the model at the best fit, whose sign and magnitude set the over- or under-estimation of the parameter uncertainties. This closed-form expression quantifies when and by how much the MC method departs from Bayesian inference. We illustrate it on two single-parameter examples solvable in closed form and point to its evaluation in full PDF and SMEFT fits as a natural next step.
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High Energy Physics (Phenomenology)

A directional force template for quadratically coupled ultralight dark matter

Dawid Brzeminski and Aaron Pierce

Quadratic couplings between ultralight scalar dark matter and Standard Model fields can produce a distorted dark-matter field profile around the Earth. Gradients in the field induce a non-radial, composition-dependent force that can be suppressed at the Earth's surface while remaining accessible to space-based experiments. The MICROSCOPE satellite, which searched for violations of the equivalence principle, can constrain this force, but existing results assume a radial force, and they cannot be directly translated into an optimal bound in the anisotropic regime. We develop a signal template for this regime by organizing the force into radial and polar multipole coefficients and projecting the force onto the MICROSCOPE measurement axis. We use this template to recast the published MICROSCOPE constraint using the component of the signal that overlaps with the radial-force template. We estimate the sensitivity gain that would be provided by an analysis utilizing the additional non-overlapping signal. Such an analysis could improve sensitivity to the couplings of quadratically coupled scalar dark matter by more than an order of magnitude relative to the radial-force recast for dark matter masses $\gtrsim 10^{-9}$ eV.
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Quantum Physics

The subthreshold issue of fusion-based quantum computing

Matthias C. Löbl, Love A. M. Pettersson, Jan Dragašević et al. (+2 more)

Fusion-based quantum architectures are the leading approach to photonic quantum computing. However, the sub-threshold regime, where logical error rates must reach the levels required by useful applications, has received little attention. We show that in this regime, fusion failure imposes a noise floor on the logical error rate that prevents all-linear-optics architectures from reaching the required rates at low overhead. For fusion-based architectures using quantum emitter spins, we show that the noise floor is reduced by orders of magnitude at a lower overhead.
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All authors Matthias C. Löbl, Love A. M. Pettersson, Jan Dragašević, Susan X. Chen, Oliver A. D. Sandberg

Astrophysics of Galaxies

pop-cosmos: Galaxy size evolution across structural and star-formation classifications in COSMOS-Web

Madalina N. Tudorache, Hiranya V. Peiris, Stephen Thorp et al. (+7 more)

Galaxy sizes are correlated with stellar mass and redshift, as characterised by size scaling relations. The inferred forms of these scaling relations are sensitive to how galaxies are classified – either by their star formation activity (e.g. specific star-formation rate, sSFR) or by their morphology markers (e.g. bulge-to-total ratio, Sérsic index). We combine stellar mass and sSFR estimates from pop-cosmos (a generative model trained on COSMOS2020 Spitzer IRAC $\textit{Ch.1} <26$) with size and morphology measurements from COSMOS-Web, obtaining $99,369$ galaxies. By investigating the size-mass and the size-redshift relations, we show that: (i) the sSFR/morphology splits give quantitatively different slopes, intercepts, and intrinsic scatter behaviour; (ii) intrinsic scatter depends on structural morphology but not on sSFR, which constrains the galaxy-halo connection; (iii) the quiescent and bulge-dominated size-mass relations both show double-power law breaks, but at different pivot masses, indicating that quenching and structural transformation occur on different time-scales; (iv) the morphology-dependent trends are only recoverable from space-based imaging. Further, the quiescent pivot mass $M_{\ast} \sim 10^{10.7}~\mathrm{M}_{\odot}$ coincides with the mass scale at which active galactic nuclei (AGN, infrared torus) bolometric luminosity fraction peaks in transitioning galaxies, while the bulge-dominated pivot mass $M_{\ast} \sim 10^{11.1}~\mathrm{M}_{\odot}$ coincides with the halo mass at which AGN-driven baryonic redistribution peaks, which may trace the interval over which AGN feedback ramps from quenching onset to structural transformation.
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All authors Madalina N. Tudorache, Hiranya V. Peiris, Stephen Thorp, Sinan Deger, Daniel J. Mortlock, Gurjeet Jagwani, Anik Halder, Boris Leistedt, Benedict Van den Bussche, Joel Leja

Cosmology and Nongalactic Astrophysics

Dark energy from neutrino interactions in Unimodular Gravity

Alejandro Gil-Ocaranza, Josue De-Santiago, Mauricio Lopez-Hernandez et al. (+1 more)

We investigate a dark energy scenario generated by neutrino interactions mediated by a light scalar field, in which finite-temperature corrections induce an effective neutrino mass that evolves with the thermal history of the Universe. Within the framework of Unimodular Gravity, these interactions give rise to a non-conservation current, leading to dynamical dark energy. We study one- and two-neutrino realizations of the model. In the one-neutrino case, the dark energy density evolves monotonically, whereas in the two-neutrino scenario it can reach a maximum at intermediate redshifts before decreasing at late times. Using late time cosmological datasets, we constrain the effective interaction strength for lightest-neutrino masses in the range $0.05 \,{\rm meV}\le m_1 \le 1 \,{\rm meV}$. We find preferred interaction scales of order $G_s\sim10^{12} \, {\rm eV}^{-2}$ with a significance of $2 \sigma$, with the inferred coupling decreasing as the assumed neutrino mass increases. Assuming neutrino couplings of order unity, this $G_s$ value corresponds to an ultralight mediator with mass $m_\phi\sim10^{-6} \, {\rm eV}$. We further assess the impact of Planck distance-prior, finding a noticeable reduction in parameter degeneracies and a reconstructed dark energy evolution closer to that of a cosmological constant. Our results show that neutrino interactions can generate both monotonic and non-monotonic dark energy evolutions while remaining compatible with current cosmological observations. The inferred interaction strengths remain consistent with non-zero values for part of the explored neutrino-mass range, supporting neutrino-induced dark energy dynamics as a viable phenomenological extension of $\Lambda$CDM at the background level.
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All authors Alejandro Gil-Ocaranza, Josue De-Santiago, Mauricio Lopez-Hernandez, Jorge L. Cervantes-Cota

High Energy Physics (Theory)

Calabi-Yau Metrics with Full Moduli Dependence

Andrei Constantin, Seung-Joo Lee, Andre Lukas et al. (+1 more)

Recent advances in numerical and machine-learning methods have enabled highly accurate constructions of Ricci-flat metrics on compact Calabi-Yau three-folds. For phenomenological applications it is crucial to understand how these metrics vary across moduli space. In this work, we construct approximate analytic expressions for Ricci-flat Calabi-Yau metrics with explicit complex-structure and Kähler moduli dependence by combining machine-learned numerical data with symbolic regression. Our approach is based on an explicit Ansatz for the Kähler potential with moduli-dependent coefficients. Fitting this Ansatz to numerical data and applying symbolic regression allows us to reconstruct analytic formulae for these coefficients, thereby obtaining approximate Ricci-flat metrics with explicit moduli dependence. We apply the construction to a one-parameter family of bi-cubic three-folds in $\mathbb{P}^2 \times \mathbb{P}^2$, achieving percent-level agreement with the underlying numerical data.
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All authors Andrei Constantin, Seung-Joo Lee, Andre Lukas, Luca A. Nutricati

Disordered Systems and Neural Networks

Spectral phase transitions and trainability in neural network learning dynamics

Chanju Park, Dario Bocchi, Francesco D'Amico et al. (+2 more)

The emergence of low-dimensional structures in the spectra of neural network weight matrices is a common empirical feature of trained models, but the dynamical origin of this phenomenon during learning remains an open problem. We formulate neural network training as the stochastic evolution of an initially random matrix ensemble, driven by stochastic gradient descent (SGD) updates that reshape the spectral bulk while amplifying signal strength. This induces a Baik-Ben Arous-Péché (BBP) transition during training, where isolated eigenvalues detach from the random bulk distribution, providing a dynamical framework for representation formation in high-dimensional learning dynamics. We demonstrate this in a solvable linear teacher-student model, where spectral evolution is analytically tractable and a phase diagram of trainability governed by the step size (or learning rate) and initial weight variance is obtained, and subsequently extend our formalism beyond the linear regime to nonlinear and stochastic settings. Numerical simulations in realistic settings support this picture, showing robust emergence of spectral alignment during training. Our results suggest that spectral analysis may provide a unified perspective of stochastic learning dynamics, linking trainability, optimisation hyperparameters, spectral phase transitions, and representation learning in neural networks.
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All authors Chanju Park, Dario Bocchi, Francesco D'Amico, Biagio Lucini, Gert Aarts

High Energy Physics (Theory)

Geometric pairing of Nambu–Goldstone modes in spacetime symmetry breaking

Aleksander Głódkowski

We identify a geometric pairing mechanism in systems with spontaneously broken spacetime symmetries, whereby pairs of Goldstone fields become canonically conjugate and hybridize into a single type-B Nambu–Goldstone mode (NGM). The mechanism originates from deformations of the local spacetime volume element induced by Goldstone fluctuations, which endow the Goldstone manifold with a Berry curvature. Integrating this pairing with existing reductions, we propose a general counting formula for the number of gapless NGMs in many-body systems. We demonstrate the mechanism in a microscopic model of a two-component Bose–Einstein condensate, where the dilaton and the $U(1)$ Goldstone field combine into a single NGM with quadratic dispersion.
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High Energy Physics (Theory)

Subregion observer rules from generalized entanglement wedges

Lana Bozanic, Kenneth Higginbotham and Chris Waddell

We consider rules for modifying holographic tensor networks proposed in two independent contexts: by the Colorado (CO) group in 2503.09681 to incorporate observers in holographic maps, and by Kaya-Rath-Ritchie (KRR) in 2506.10064 to derive the Bousso-Penington generalized entanglement wedge proposal. Interestingly, these two sets of tensor network rules are exactly equivalent. This suggests a more general connection between these Abdalla-Antonini-Iliesiu-Levine (AAIL) inspired observer rules and generalized entanglement wedges. To pursue this connection, we first use KRR's analogous rules for the gravitational path integral (based on fixed geometry states) to generalize AAIL's path integral rules to include observers occupying a bulk subregion. Additionally, we leverage the connection in the opposite direction by using the AAIL rules to derive the Bousso-Penington proposal for pointlike bulk regions in JT gravity.
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Quantum Physics

Quantum Fourier Generative Models Trainable at Large Scale

Cenk Tüysüz, Oleksandr Kyriienko and Michele Grossi

We propose an algorithmic framework for building and training quantum generative models corresponding to multivariate probability distributions. Our model uses parallel Fourier feature maps for embedding continuous-valued variables combined with a forrelation-type quantum circuit for tuning Fourier coefficients of the quantum model. Crucially, we develop a distinct training strategy where training is enabled at large scale by log-likelihood loss with unbiased Monte Carlo estimator based on Parseval's identity. Unlike prior work that relied on maximal mean discrepancy (MMD) loss, our approach goes beyond matching just low frequency moments, while enabling efficient classical training. Once the model is trained, we use inverse quantum Fourier transforms to map it into a separate sampling circuit in the computational basis. We demonstrate the efficiency of the suggested framework by validating loss estimation at the scale of over 1000 qubits on a single GPU. We show that univariate and bivariate models with highly non-trivial structure can be trained to low total variation distance, while fine-tuned IQP models with MMD loss show poor performance. Comparing to classical baselines represented by normalizing flow and diffusion models, we show that our approach avoids oversmoothing and preserves multi-modal structure of the target. Finally, we have deployed the trained models on superconducting quantum devices, successfully sampling distributions with per-sample execution times of approximately $300\,\mu\mathrm{s}$. Our work shows that quantum generative models with the train-on-classical deploy-on-quantum approach can provide both high-quality structure at increased scale and fast sampling access needed for inference.
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Cosmology and Nongalactic Astrophysics

Strongest constraints on dark acoustic oscillations from the Lyman-alpha forest

Zhihan Yuan, Caleb Gemmell, Keir K. Rogers et al. (+4 more)

We set the first constraints on a small-scale dark acoustic oscillation (DAO) in the linear matter power spectrum arising from dark sector interactions, with a full forward model of the Ly-$\alpha$ forest. No more than 30% of dark matter can form DAOs if they peak at wavenumbers $< 50\,h\,\mathrm{Mpc}^{-1}$ (95% c.l.), probing scales $25 \times$ smaller than the cosmic microwave background (CMB). Given the complex covariance of DAO and nuisance parameters, we use a deep kernel learning emulator of hydrodynamical simulations to capture imprints of linear oscillations in the Ly-$\alpha$ forest.
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All authors Zhihan Yuan, Caleb Gemmell, Keir K. Rogers, Jared Barron, Sandip Roy, David Curtin, Norman Murray

High Energy Physics (Phenomenology)

Background-Induced Forces from Quadratically Coupled Ultralight Dark Matter

Thomas Bouley, Xucheng Gan, Hailin Xu et al. (+1 more)

Quadratically coupled ultralight scalar dark matter behaves as a coherent classical field whose interactions with matter can induce a composition-dependent force through the dark matter background. We present a complete calculation of this background-induced force beyond the spherically symmetric approximation. Using a partial-wave treatment of dark-matter scattering, we determine its angular dependence and derive an analytic description valid even when the dark-matter wavelength is much smaller than the Earth's radius. We show for the first time that Earth screening generates a characteristic frequency-band structure, splitting the signal into multiple sidebands that provide a distinctive experimental signature. We further show that the relative amplitudes of these sidebands vary annually as the satellite's Sun-synchronous orbital plane precesses in step with the Earth's revolution around the Sun, allowing us to construct a complete signal template. As an application of these results, we re-evaluate constraints from the MICROSCOPE mission, which currently provides the strongest laboratory limits on equivalence-principle violations from ultralight dark matter. We further show that proposed space-based equivalence-principle experiments, such as Galileo Galilei and STE-QUEST, can significantly enhance their sensitivity to ultralight scalar dark matter by incorporating the full frequency-band information.
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All authors Thomas Bouley, Xucheng Gan, Hailin Xu, Tien-Tien Yu