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Physics

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Wednesday 24 June

Astrophysics of Galaxies

Wind Acceleration as a Driver of Detached Blueshifted Absorption in Quasar Disk Winds

Randall C. Dannen, Daniel Proga, Paola Rodríguez Hidalgo et al. (+4 more)

Active galactic nuclei (AGN) unification models often emphasize the viewing angle, $i$, but $i$ alone does not determine quasar properties. This is crucial for quasar outflows: UV absorption in Extremely High Velocity Outflow (EHVO) quasars can reach blueshifted velocities of $\sim0.2~c$. In disk-wind models, both $i$ and internal wind structure shape the emergent spectrum. We test their interplay using biconical quasar disk-wind models with different acceleration lengths, $R_v$, and generate synthetic spectra over a range of $i$. We use Monte Carlo radiative transfer to account for finite continuum sources, wind attenuation, scattering, reprocessing, and emission. Changing $R_v$ greatly alters the ionization structure, continuum shape, and absorption-line profiles. At intermediate viewing angles, sightlines pass through the fastest wind. Even there, highly detached and blueshifted \CIV\ absorption like that observed in EHVO quasars appears only in models with small $R_v$. In these models, the gas reaches high velocity before attaining the ionization and density conditions favorable for \CIV. Models with larger $R_v$ instead produce broader, less detached troughs, even when the terminal velocity is very high. Thus, highly detached and blueshifted absorption requires both a high terminal velocity and small $R_v$, making such features diagnostics of disk-wind acceleration and structure. EHVO quasars provide a clear example, but the same principle applies more broadly to highly detached and blueshifted absorption in quasar outflows. Our results support an extended disk-wind view of AGN unification: $i$ selects the observed wind region, while $R_v$ shapes the emergent spectrum and absorption morphology.
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All authors Randall C. Dannen, Daniel Proga, Paola Rodríguez Hidalgo, Kara Smith, Anna Ritchie, Liliana Flores, Morrigan Kalet

Solar and Stellar Astrophysics

DKIST Unveils Four-Lobed Stokes U Profiles in a Magnetically Complex Sunspot Penumbra

Ryan James Campbell and Sarah Jaeggli

We present DKIST spectropolarimetric observations of a sunspot penumbra revealing spatially coherent four-lobed Stokes U profiles that persist after polarimetric crosstalk correction. The observed Stokes vectors are well reproduced by stratified inversions containing gradients in velocity and magnetic parameters, including line-of-sight variation of the magnetic azimuth. Forward synthesis experiments in which the magnetic azimuth is artificially held constant with optical depth substantially modify the Stokes U morphology while leaving Stokes I, Q, and V comparatively unchanged, indicating that azimuthal variation is an important contributor to the observed linear polarisation signatures within the tested one-component atmospheres. We explored degeneracies using both two-component atmospheres and one-component constant-azimuth models: the former generally converged toward pathological solutions, while the latter provided a plausible degenerate explanation for much of the observed four-lobed Stokes U morphology. A supervised machine-learning classifier applied to Stokes V profiles shows that the associated magnetic complexity is spatially confined to the penumbra-light-bridge boundary where the four-lobed Stokes U profiles and reverse-polarity fields are observed. These results identify four-lobed Stokes U profiles as a potential spectropolarimetric signature of complex line-of-sight magnetic structuring in sunspot penumbrae, providing new observational constraints on fine-scale penumbral magnetic topology.
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Quantum Physics

Mechanisms governing photon-pair generation and emission directionality in quantum metasurfaces

Alberto Paniate, Ivano Ruo-Berchera and Francesco Monticone

Metasurfaces are emerging as a promising platform for photon-pair generation through spontaneous parametric down-conversion, thanks to their compactness, integrability, and intrinsic multifunctionality, which enables the engineering of complex quantum states. However, their full potential remains only partially exploited because the physical mechanisms governing key properties of the generated photon pairs, such as generation efficiency and emission directionality, are not yet fully understood. As a result, metasurface designs and experimental configurations are often optimized through trial-and-error procedures. Here, we theoretically investigate the main mechanisms that control photon-pair generation and detection by studying how different pump configurations and measurement geometries affect the generation efficiency, emission directionality, and collection efficiency of the emitted photon pairs. This framework allows us to interpret existing experimental results and to provide general guidelines for the design of metasurfaces and the choice of experimental configurations in future experiments. Finally, we show that substrate thickness and multilayer configurations represent additional degrees of freedom for quantum metasurface design and can be engineered to enhance the generation efficiency and control the emission directionality, providing a new route for the optimization of photon-pair sources based on metasurfaces.
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High Energy Physics (Theory)

Dirichlet, Neumann, Mixed and self-dual holography: (self-dual) Yang–Mills theory II

Evgeny Skvortsov and Richard Van Dongen

We consider Yang–Mills, Chalmers–Siegel and self-dual Yang–Mills (SDYM) theories within AdS/CFT correspondence. Bulk-to-bulk and boundary-to-bulk propagators are derived in various gauges and for Dirichlet, Neumann, mixed and self-dual boundary conditions. Three- and four-point holographic correlators are computed in the three theories to establish the relation between the observables thereof. This is a companion paper to [arXiv:2602.21658].
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High Energy Physics (Phenomenology)

Kinetic freeze-out and diffusion dynamics in small-system asymmetric collisions at sqrt(sNN)=200 GeV in light of a generalized Fokker-Planck distribution

M. Waqas, Wolfgang Bietenholz, Khusniddin K. Olimov et al. (+4 more)

A generalized Fokker-Planck solution is used to examine the transverse momentum ($p_{T}$) spectra of neutral pions generated in small-system asymmetric collisions, $p$-Al, $p$-Au, $d$-Au, and $^3$He-Au, at $\sqrt{s_{NN}}=200$ GeV. This framework provides a cohesive explanation of particle production over a broad range of transverse momenta. We extract the energy scale governing the transition between a thermal and a hard regime, the effective temperature ($T$), and the exponents determining the high-momentum falloff from fits to PHENIX data. $T$ increases systematically with the collision centrality and colliding system size, ranging from about 0.33 GeV in peripheral $p$-Al collisions to 0.45 GeV in central $^3$He-Au collisions. This increase is correlated with the average number of participant nucleons, $<N_{part}>$, and the charged-particle pseudorapidity density, $<dN_{ch}/d\eta >$, indicating that larger and more central collisions create a denser, more strongly interacting medium that freezes out at a higher temperature. The acquired transition scale and power-law exponents follow consistent patterns across systems and centralities, revealing details about the sharpness of the transition from thermal to hard processes, and the relative strength of momentum-space diffusion versus drag. Interestingly, when the gold target dominates the collision geometry in the largest system ($^3$He-Au), the transition scale becomes nearly independent of centrality, signifying saturation of the diffusion process. Our findings demonstrate that the generalized Fokker-Planck solution is a sensitive probe of transport properties and non-extensive dynamics in the quark-gluon plasma produced even in small-system relativistic collisions, and it consistently describes pion spectra in this set of collisions.
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All authors M. Waqas, Wolfgang Bietenholz, Khusniddin K. Olimov, Muhammad Ajaz, Jihane Ben Slimane, Laila A. Al-Essa, A. Haj Ismail

Instrumentation and Methods for Astrophysics

Indigenizing the Drake Equation: how Indigenous methods can help us understand life in the Milky Way Galaxy

Hilding R. Neilson

The Drake Equation is a thought experiment whose purpose is to understand the ingredients necessary for life and advanced technological civilizations to exist on other worlds in our galaxy. However, beyond reflecting on life on Earth, we have no knowledge of many of these ingredients, such as the number of planets that have life, the number with intelligent life, the number with advanced civilizations, and the lifetimes of these civilizations. In this work, I will review the Drake Equation and the biases that scientists have traditionally had in discussing this equation and how it has led to the current searches of biological and technological signatures. I will discuss how the Drake Equation looks different if we consider it through the lens of Indigenous methods and sciences and how these methods would lead to a dramatically different view of life in our Galaxy.
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Solar and Stellar Astrophysics

Constraints on Binarity for the Extreme Oe Variable Star AzV 493

M. S. Oey, Irene Vargas-Salazar, Edmund Hodges-Kluck et al. (+6 more)

The extreme Oe star AzV 493 is known to show unusual photometric and spectroscopic variability that suggest the presence of an unseen companion in a highly eccentric and long-period (7.3 or 14.6-year) orbit. We obtained a Chandra/ACIS observation near the putative periastron for the 7.3-year orbit to test for transient X-ray emission that would confirm its binary nature. Our data only place an upper limit to the X-ray luminosity of L_X < 2.5 x 10^33 erg/s based on the 0.5 - 8 keV flux limit. Additionally, we obtained 4 new spectroscopic observations with the M2FS spectrograph at Magellan and 20 archive FLAMES/GIRAFFE and X-Shooter spectra from ESO/VLT to further constrain the possibility of radial velocity (RV) variation. Statistical analysis of the RV measurements yields inconclusive results regarding the existence of variations. We discuss possible mass limits for a potential companion, which may be a black hole, in the event that the variations are real. The violet-to-red (V/R) Balmer ratio has also recently inverted, which may be a further indication of a companion.
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All authors M. S. Oey, Irene Vargas-Salazar, Edmund Hodges-Kluck, Norberto Castro, Michal K. Szymanski, Mario Mateo, Mathieu Renzo, Mark W. Suffak, Maxwell Moe

Instrumentation and Detectors

Production and installation of wavelength-shifting reflective light enhancers for the Short-Baseline Near Detector

R. Acciarri, L. Aliaga-Soplin, R. Alvarez-Garrote et al. (+194 more)

We report on the design, production, and installation of a wavelength-shifting reflective system on the cathode of the Short-Baseline Near Detector (SBND), a liquid argon time projection chamber located along the Fermilab Booster Neutrino Beam. To increase and homogenize scintillation-light collection, 64 double-sided plates were fabricated from FR4, laminated with specular reflector film and coated with 300 $\mu$g/cm$^2$ of tetraphenyl butadiene (TPB) wavelength shifter using controlled physical vapor deposition. The coating uniformity was validated through dedicated measurements of deposited mass and profilometry studies. Because exposure to ambient blue/UV light could degrade the TPB, protective filtering and controlled storage conditions were implemented during handling and installation. The coated plates were assembled between conductive meshes for high-voltage compatibility and installed in situ during detector integration. This system constitutes the largest TPB-coated area deployed in a neutrino detector. It operates in conjunction with SBND's photon detection system, which consists of photomultiplier tubes and X-ARAPUCAs. Early light-collection measurements show high uniformity and light response across the detector, supporting improved triggering, calorimetry, and position reconstruction in SBND.
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All authors R. Acciarri, L. Aliaga-Soplin, R. Alvarez-Garrote, D. Andrade Aldana, C. Andreopoulos, A. Antonakis, S. Balasubramanian, A. Barnard, V. Basque, J. Bateman, M. C. Bazetto, A. Beever, E. Belchior, M. Betancourt, A. Bhat, M. Bishai, A. Blake, B. Bogart, D. Brailsford, A. Brandt, S. Brickner, M. B. Brunetti, L. Camilleri, D. Caratelli, D. Carber, B. Carlson, M. F. Carneiro, W. Castiglioni, R. Castillo Fernandez, F. Cavanna, A. Chappell, H. Chen, S. Chung, R. Coackley, S. Cotton J. I. Crespo-Anadón, C. Cuesta, Y. Dabburi, O. Dalager, M. Dall'Olio, R. Darby, I. de Icaza, M. Del Tutto, Z. Djurcic, S. Dominguez-Vidales, M. Dubnowski, K. Duffy, S. Dytman, A. Ereditato, J. J. Evans, A. Ezeribe, C. Fan, A. Filkins, B. Fleming, W. Foreman, D. Franco, H. Frandini, G. Fricano, I. Furic, A. Furmanski, S. Gao, D. Garcia-Gamez, S. Gardiner, I. Gil-Botella, S. Gollapinni, O. Goodwin, P. Green, W. C. Griffith, L. Hagaman, P. Hamilton, B. Harris, C. Harrison, A. Hergenhan, M. Hernandez-Morquecho, P. Holanda, C. James, R. S. Jones, M. Jung, T. Junk, D. Kalra, G. Karagiorgi, L. Kashur, K. J. Kelly, W. Ketchum, M. King, J. Klein, L. Kotsiopoulou, S. Kr Das, T. Kroupová, V. A. Kudryavtsev, N. Lane, H. Lay, R. LaZur, J.-Y. Li, K. Lin, B. R. Littlejohn, L. Liu, W. C. Louis, X. Lu, X. Luo, A. Machado, P. Machado, C. Mariani, F. Marinho, J. Marshall, C. Martin-Morales, A. Mastbaum, K. Mavrokoridis, N. McConkey, B. McCusker, J. Mclaughlin, K. Mistry, M. Mooney, A. F. Moor, G. Moreno Granados, C. A. Moura, J. Mueller, S. Mulleriababu, A. Navrer-Agasson, M. Nebot-Guinot, V. C. L. Nguyen, F. J. Nicolas-Arnaldos, J. Nowak, S. B. Oh, N. Oza, O. Palamara, N. Pallat, V. Pandey, A. Papadopoulou, H. B. Parkinson, J. Paton, L. Paulucci, Z. Pavlovic, D. Payne, L. Pelegrina-Gutiérrez, O. L. G. Peres, V. L. Pimentel, J. Plows, G. Putnam, X. Qian, R. Rajagopalan, P. Ratoff, H. Ray, M. Reggiani-Guzzo, M. Roda, J. Romeo-Araujo, M. Ross-Lonergan, N. Rowe, P. Roy, A. Sanchez-Castillo, P. Sanchez-Lucas, D. W. Schmitz, A. Schneider, A. Schukraft, H. Scott, E. Segreto, M. Shaevitz, P. Singh, B. Slater, J. Smith, R. Soares, M. Soares-Nunes, M. Soderberg, S. Söldner-Rembold, F. Spagliardi, J. Spitz, M. Stancari, T. Strauss, A. M. Szelc, C. Thorpe, D. Totani, M. Toups, C. Touramanis, L. Tung, G. A. Valdiviesso, R. G. Van de Water, A. Vázquez-Ramos, L. Wan, M. Weber, H. Wei, T. Wester, A. White, A. Wilkinson, P. Wilson, T. Wongjirad, E. Worcester, M. Worcester, S. Yadav, E. Yandel, T. Yang, L. Yates, S. Yebes, B. Yu, H. Yu, J. Yu, B. Zamorano, J. Zennamo, C. Zhang

Solar and Stellar Astrophysics

Six decades of TIGRE and Mount Wilson chromospheric monitoring in the H and K lines: The quest for an understanding of solar-type activity

J. H. M. M. Schmitt, K.-P. Schröder, M. Mittag et al. (+3 more)

The combined time series of the consistently calibrated chromospheric activity indicator, the S-index – derived from Mount Wilson and TIGRE data – now spans more than five decades of monitoring observations of the Sun and of more than one hundred solar-like stars. For the first time, these data allow us to probe the long-term stability of solar-type magnetic cycles as well as their possible transition into other behavioral forms of stellar activity in the time domain. Such variability studies are an important input for solar-stellar connection research and for our empirical understanding of the long-term perspective of solar activity as well as of a wider empirical picture of the coevolution of magnetic activity with stellar structure. We here present and discuss a representative selection of cool main-sequence stars, for which such data are available. The excellent quality of our TIGRE data now more than doubles the number of known cyclic stars. Grading them (i.e., excellent, good, fair, and poor) and putting them into an evolutionary perspective, we find that stars more active than the Sun are also more likely to show cyclic variability than stars below solar activity. Furthermore, more active stars tend to have more regular cycles, while the solar mean S-value fits the lower end of the S-index range found for cyclic stars. This is consistent with the occurrence of solar Maunder minima episodes, hinting at a sometimes already unstable solar cycle. We find eighteen stars with even lower activity and lower variability than the Sun, which provide a preview into the latter's distant future.
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All authors J. H. M. M. Schmitt, K.-P. Schröder, M. Mittag, A. Hempelmann, J. N. González-Pérez, Dennis Jack

Instrumentation and Methods for Astrophysics

Low Thrust Electric Propulsion Mission Concepts For a 3-Meter Class Space Telescope

Yael M. Brynjegard-Bialik, Mohamed Nassif, Drew Latta et al. (+12 more)

Space-based telescopes benefit from operating in stable orbital environments with reduced exposure to radiation and thermal fluctuations in order to minimize cost and maximize time for high-quality observations. Finding this ideal environment proves beneficial particularly for exoplanet discovery and characterization; direct imaging requires sub-nanometer wavefront stability and multi-hour observations, and transit detection requires parts-per-million photometric accuracy. Our team at University of Arizona's Steward Observatory and the Wyant College of Optical Sciences is evaluating various mission concepts for a 3-meter class telescope design, flying on a spacecraft bus equipped with a low thrust propulsion system. The presented mission analysis focuses on obtaining suitable transfer trajectories to the desired science orbit as well as understanding the radiation environment during the transfer, which is relevant for low thrust missions. The science analysis explores different operating orbits with the purpose of yielding maximum scientific return for detecting exoplanets. In this paper, we evaluate the use of a 2:1 lunar resonant orbit and a Sun-Earth L2 halo orbit for our mission.
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All authors Yael M. Brynjegard-Bialik, Mohamed Nassif, Drew Latta, Neel Kunjur, Nicholas Rahaim, Paul DeTrempe, Abhi Tripathi, Isaac Saedi-Marghmaleki, Dillon O'Reilly, Justin Hom, Patrick Ingraham, Jeffrey Kingsley, Buell T. Jannuzi, S. Pete Worden, Ewan S. Douglas

High Energy Physics (Theory)

A Circle That Won't Return: The Fate of RR Fluxes and D-branes in Type 0A Tachyon Condensation

Ahmed Rakin Kamal

We study the closed-string tachyon and doubled Ramond-Ramond sector of type 0A in light of the proposed M-theory description on $S^1\vee S^1$-the wedge of two circles joined at a point. In this picture the two RR copies are associated with the two circle components, which we call branches, and tachyon condensation corresponds to shrinking one branch to the type IIA endpoint. From the type 0A equations of motion, we derive the branch-balance condition for a tachyon stationary point and identify the branch-odd RR fluctuation that sources the tachyon around a symmetric background. We then analyze the fate of the collapsing branch RR data as one branch of the wedge collapses to the type IIA endpoint. For an isolated unscreened collapsing-branch $D_p^-$ source, a Gauss-law estimate shows that the long-range RR field-energy cost scales inversely with the shrinking circle and thus becoming infinitely costly, generalizing the $D0^-$-brane decoupling in the original wedge picture. We describe the infrared screening of the relative RR field through an effective higher-form Stückelberg mechanism and distinguish this from a possible discharge of localized relative charge. Finally, using standard Wess-Zumino couplings of D-branes, we identify an effective relative-charge carrier and derive a parametric thin-wall criterion for when such a discharge channel $D_p^- \to D_p^+$ can be energetically favored.
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Astrophysics of Galaxies

The 10-15 GHz radio continuum survey of the Galactic Plane with SKAO

A. Traficante, C. Mininni, F. Cavallaro et al. (+63 more)

Star formation emerges from the complex interplay between gravity, turbulence, magnetic fields, and stellar feedback, all of which vary across spatial scales and Galactic environments. Over the past decades, extensive multiwavelength surveys of the Galactic Plane have progressively unveiled this complexity. Far-infrared and sub-millimetre surveys have identified and characterized tens of thousands of star-forming regions, revealing their mass, temperature, and evolutionary stage. Complementary molecular-line surveys, spanning several CO transitions and isotopologues, have mapped the gas kinematics from giant molecular clouds down to sub-parsec structures. The advent of interferometers such as ALMA has revolutionized this field, enabling systematic studies of gas dynamics, fragmentation, and collapse in dense clumps at scales of a few thousand astronomical units. At the same time, mid-infrared and radio surveys at frequencies 0.8 <= nu <= 5 GHz have traced ionised gas associated with the earliest and latest phases of massive-star evolution, including thermal radio jets, hypercompact and ultracompact HII regions, supernova remnants, planetary nebulae, and evolved massive stars. Yet, a uniform, Galaxy-wide census of ionised structures and feedback processes remains elusive. A transformational leap forward requires a sensitive, high-resolution radio survey of the Galactic Plane at 10-15 GHz, capable of resolving physical scales smaller than 0.05 pc at distances up to 20 kpc. This is precisely the goal of the SKA-Mid Galactic Plane survey, which will, with its unprecedented sensitivity, angular resolution, and mapping speed, provide the first panoptic view of ionised gas and stellar feedback across the Milky Way.
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All authors A. Traficante, C. Mininni, F. Cavallaro, G. Umana, C. Trigilio, S. Molinari, L. D. Anderson, M. Audard, C. Bordiu, C. S. Buemi, C. Carrasco-Gonzalez, L. Cerrigone, E. J. Chung, J. Dey, A. Ingallinera, I. Jimenez-Serra, P. Klaassen, S. Loru, K. Mallick, A. Nucara, M. Padovani, J. D. Pandian, K. L. J. Rygl, T. M. Rodríguez, G. Sabatini, S. Reissl, P. Suin, M. A. Thompson, T. L. Bourke, J. S.Urquhart, M. Valeille-Manet, F. Xu, A. Zavagno, M. Benedettini, E. Bianchi, A. Bracco, F. Bufano, C. Codella, N. Cunningham, J. Dawson, D. Galli, M. G. Guarcello, A. Karska, W.-J. Kim, P. Leto, B. Liu, B. Mookerjea, F. Motte, T. Nony, R. Paladini, A. Patel, L. Podio, A. J. T. Ramaila, B. Riaz, S. Riggi, D. A. Roshi, A. Ruggeri, Á. Sánchez-Monge, R. Schödel, O. M. Smirnov, J. D. Soler, S. Sottie, R. Unnikrishnan, A. Y. Yang, K. Wang, T. Wilson

High Energy Physics (Experiment)

Charged-lepton identification at Belle~II

Belle II Collaboration: M. Abumusabh, I. Adachi, A. Aggarwal et al. (+408 more)

Effective particle identification capabilities are a strategic priority for the physics program of the Belle~II experiment. We describe the algorithms used at Belle~II for identifying electrons and muons and separating them from charged hadrons. We present the performance obtained by the experiment during Run 1, which consists of 428 fb$^{-1}$ of data collected at the energy-asymmetric $e^+e^-$ collider SuperKEKB between 2019 and 2022 at center-of-mass energies near the mass of the $\Upsilon(4S)$.
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All authors Belle II Collaboration: M. Abumusabh, I. Adachi, A. Aggarwal, H. Ahmed, Y. Ahn, H. Aihara, M. Akdag, N. Akopov, S. Alghamdi, M. Alhakami, N. Althubiti, K. Amos, M. Angelsmark, N. Anh Ky, C. Antonioli, K. Arai, H. Atmacan, V. Aushev, R. Ayad, V. Babu, H. Bae, N. K. Baghel, P. Bambade, Sw. Banerjee, S. Bansal, M. Barrett, M. Bartl, J. Baudot, A. Beaubien, F. Becherer, J. Becker, G. F. Benfratello, J. V. Bennett, F. U. Bernlochner, V. Bertacchi, M. Bertemes, E. Bertholet, M. Bessner, S. Bettarini, V. Bhardwaj, B. Bhuyan, F. Bianchi, T. Bilka, D. Biswas, A. Bobrov, D. Bodrov, G. Bonvicini, A. Boschetti, A. Bozek, M. Bračko, P. Branchini, R. A. Briere, T. E. Browder, A. Budano, S. Bussino, F. Callet, Q. Campagna, M. Campajola, L. Cao, M. Carminati, G. Casarosa, C. Cecchi, P. Cheema, L. Chen, B. G. Cheon, C. Cheshta, H. Chetri, K. Chilikin, K. Chirapatpimol, H.-E. Cho, K. Cho, S.-J. Cho, S.-K. Choi, S. Choudhury, S. Chutia, J. Cochran, J. A. Colorado-Caicedo, I. Consigny, L. Corona, H. Crotte Ledesma, S. Cuccuini, J. X. Cui, E. De La Cruz-Burelo, S. A. De La Motte, G. De Nardo, G. De Pietro, R. de Sangro, M. Destefanis, S. Dey, R. Dhayal, A. Di Canto, J. Dingfelder, Z. Doležal, X. Dong, G. Dujany, P. Ecker, D. Epifanov, J. Eppelt, R. Farkas, P. Feichtinger, T. Ferber, T. Fillinger, C. Finck, G. Finocchiaro, F. Forti, A. Frey, B. G. Fulsom, A. Gabrielli, P. Gagneja, R. Garg, G. Gaudino, V. Gaur, V. Gautam, A. Gaz, A. Gellrich, G. Ghevondyan, D. Ghosh, H. Ghumaryan, R. Giordano, A. Giri, P. Gironella Gironell, A. Glazov, B. Gobbo, R. Godang, O. Gogota, W. Gradl, E. Graziani, D. Greenwald, Y. Guan, K. Gudkova, I. Haide, H. Haigh, Y. Han, K. Hayasaka, H. Hayashii, S. Hazra, M. T. Hedges, A. Heidelbach, G. Heine, I. Heredia de la Cruz, M. Hernández Villanueva, T. Higuchi, M. Hoek, M. Hohmann, R. Hoppe, P. Horak, X. T. Hou, C.-L. Hsu, T. Humair, T. Iijima, K. Inami, N. Ipsita, A. Ishikawa, R. Itoh, M. Iwasaki, P. Jackson, D. Jacobi, W. W. Jacobs, E.-J. Jang, S. Jia, Y. Jin, A. Johnson, K. K. Joo, H. Kakuno, D. Kalita, K. H. Kang, G. Karyan, T. Kawasaki, F. Keil, C. Kiesling, C. Kim, D. Y. Kim, H. Kim, J.-Y. Kim, K.-H. Kim, H. Kindo, K. Kinoshita, P. Kodyš, S. Kohani, A. Korobov, S. Korpar, E. Kovalenko, R. Kowalewski, P. Križan, P. Krokovny, T. Kuhr, Y. Kulii, J. Kumar, R. Kumar, K. Kumara, T. Kunigo, A. Kuzmin, Y.-J. Kwon, S. Lacaprara, Y.-T. Lai, T. Lam, J. S. Lange, T. S. Lau, R. Leboucher, H. Lee, M. J. Lee, P. Leo, P. M. Lewis, C. Li, L. K. Li, Q. M. Li, S. X. Li, W. Z. Li, Y. Li, Y. B. Li, Y. P. Liao, J. Libby, J. Lin, S. Lin, Z. Liptak, V. Lisovskyi, C. Liu, M. H. Liu, Q. Y. Liu, Z. Q. Liu, D. Liventsev, S. Longo, A. Lozar, C. Lyu, J. L. Ma, Y. Ma, M. Maggiora, R. Maiti, G. Mancinelli, R. Manfredi, E. Manoni, M. Mantovano, D. Marcantonio, M. Marfoli, C. Marinas, C. Martellini, A. Martens, T. Martinov, L. Massaccesi, M. Masuda, T. Matsuda, K. Matsuoka, D. Matvienko, S. K. Maurya, M. Maushart, J. A. McKenna, Z. Mediankin Gruberová, R. Mehta, F. Meier, D. Meleshko, M. Merola, C. Miller, M. Mirra, K. Miyabayashi, H. Miyake, G. B. Mohanty, S. Moneta, A. L. Moreira de Carvalho, H.-G. Moser, N. Mudgal, Th. Muller, H. Murakami, R. Mussa, K. R. Nakamura, Y. Nakazawa, Z. Natkaniec, A. Natochii, M. Neu, S. Nishida, R. Nomaru, A. Novosel, S. Ogawa, R. Okubo, H. Ono, Y. Onuki, G. Pakhlova, S. Pardi, J. Park, K. Park, S.-H. Park, A. Passeri, S. Patra, T. K. Pedlar, R. Pestotnik, L. E. Piilonen, P. L. M. Podesta-Lerma, T. Podobnik, L. Polat, A. Prakash, V. Prasad, C. Praz, S. Prell, E. Prencipe, M. T. Prim, S. Privalov, H. Purwar, P. Rados, S. Raiz, K. Ravindran, J. U. Rehman, M. Reif, S. Reiter, L. Reuter, D. Ricalde Herrmann, I. Ripp-Baudot, G. Rizzo, S. H. Robertson, J. M. Roney, A. Rostomyan, N. Rout, G. Russo, S. Saha, D. A. Sanders, S. Sandilya, L. Santelj, C. Santos, V. Savinov, B. Scavino, J. Schmitz, S. Schneider, K. Schoenning, C. Schwanda, Y. Seino, K. Senyo, J. Serrano, M. E. Sevior, C. Sfienti, W. Shan, C. P. Shen, X. D. Shi, T. Shillington, T. Shimasaki, J.-G. Shiu, D. Shtol, A. Sibidanov, F. Simon, J. B. Singh, J. Skorupa, A. Soffer, A. Sokolov, E. Solovieva, S. Spataro, K. Špenko, B. Spruck, M. Starič, P. Stavroulakis, S. Stefkova, R. Stroili, M. Sumihama, M. Takahashi, M. Takizawa, U. Tamponi, K. Tanida, A. Thaller, D. V. Thanh, T. Tien Manh, O. Tittel, R. Tiwary, E. Torassa, K. Trabelsi, F. F. Trantou, I. Tsaklidis, M. Uchida, I. Ueda, E. Uenlue, T. Uglov, K. Unger, Y. Unno, K. Uno, S. Uno, Y. Ushiroda, S. E. Vahsen, R. van Tonder, K. E. Varvell, M. Veronesi, A. Vinokurova, V. S. Vismaya, L. Vitale, V. Vobbilisetti, R. Volpe, M. Wakai, S. Wallner, M.-Z. Wang, X. L. Wang, A. Warburton, M. Watanabe, S. Watanuki, C. Wessel, X. P. Xu, B. D. Yabsley, S. Yamada, W. Yan, W. P. Yan, J. Yelton, K. Yi, J. H. Yin, K. Yoshihara, C. Z. Yuan, J. Yuan, L. Yuan, Y. Yusa, L. Zani, F. Zeng, M. Zeyrek, B. Zhang, X. Zhao, V. Zhilich, Q. D. Zhou, X. Y. Zhou, L. Zhu, R. Žlebčík

Fluid Dynamics

Droplet Fusion as a Relaxation Process: Comparison with Shape Recovery of Newtonian and Viscoelastic Droplets

Mohammad Moein Naderi, Zhangli Peng and Huan-Xiang Zhou

Biomolecular condensates formed by phase separation often exhibit viscoelastic behavior, yet their shape recovery and fusion dynamics are frequently interpreted using purely viscous models. Here, we develop a unified theoretical and computational framework to quantify how viscoelasticity governs these two processes. We combine analytical theory for small-deformation shape recovery with axisymmetric finite-element simulations based on the Oldroyd-B constitutive model to systematically investigate both shape recovery and droplet fusion under comparable conditions. Our results show that, although both processes are driven by capillary forces, they are fundamentally distinct in their underlying physics. Shape recovery is governed by global viscocapillary relaxation of a single connected interface and follows single- or multi-exponential decay depending on the relative magnitude of the viscocapillary timescale and the stress relaxation time. In contrast, droplet fusion is intrinsically a multistage process involving localized curvature-driven neck formation, rapid bridge expansion, and a transition to global relaxation. We demonstrate that viscoelasticity introduces an additional intrinsic timescale that governs the competition between capillary driving and stress relaxation, characterized by the Deborah number. This leads to enhanced intermediate-stage fusion dynamics and modified relaxation behavior compared to Newtonian droplets. Furthermore, we show that the presence of an exterior fluid introduces additional hydrodynamic dissipation, significantly slowing the fusion process. Finally, we compare the computationally predicted droplet fusion in the Newtonian and viscoelastic cases with a stretched-exponential empirical formula. Deviations observed in viscoelastic regimes highlight the limitations of purely viscous descriptions and the need for models incorporating stress relaxation.
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Optics

Routes to Chaos in Class-B laser Dimer Necklaces

J. Diaz-Avila, A. A. Macias Infante, B. R. Jaramillo-Avila et al. (+1 more)

Linear $\mathcal{PT}$-symmetric dimer necklaces use cyclic coupling to organize phase-locked modes, while class-B laser–resonator dimers use carrier inversion to destabilize gain–loss dynamics and produce routes to chaos. We study a cyclic necklace of class-B laser–resonator dimers to determine how inter-dimer coupling and cyclic phase constraints modify carrier-mediated instabilities. The carrier inversion turns the necklace into an amplitude–phase–carrier system whose active-site gain controls intensities, while the linewidth-enhancement factor shifts phases. We derive the real dynamical equations, identify uniform fixed points above threshold, and classify their phase configurations under cyclic closure. Even necklaces support full synchronization, a uniform $\pi$ shift, and two alternating phase configurations; odd necklaces support only the first two. Linear stability of these configurations partitions the coupling plane into sixteen possible regions, including one region with no stable uniform fixed point. Long-time simulations for representative two- and three-dimer necklaces show stable lasing, multistability, and irregular lasing controlled by pump ratio and coupling strengths. Increasing the pump ratio expands stable domains and suppresses the region without stable uniform fixed points.
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All authors J. Diaz-Avila, A. A. Macias Infante, B. R. Jaramillo-Avila, B. M. Rodriguez-Lara

Materials Science

Challenging the $p$-type Paradigm: Intrinsic $n$-type Mobility in Antiferromagnetic Cr$_2$O$_3$

Á. A. Carrasco Álvarez and S. Poncé

Chromium oxide (Cr$_2$O$_3$) is widely considered a $p$-type transparent conducting oxide despite ongoing debate regarding its intrinsic transport character. Here, we resolve this question by computing phonon-limited electron and hole mobilities using the ab initio Boltzmann transport equation. We find that electron mobility systematically exceeds hole mobility over a wide temperature range, demonstrating that Cr$_2$O$_3$ is intrinsically $n$-type. Analysis of scattering mechanisms reveals that scattering with phonons affects electrons and holes similarly, and that the mobility asymmetry originates from the electronic structure, namely the larger effective mass and multi-valley character of the valence band. The intrinsic $n$-type character, combined with moderate hole mobility, enables bipolar transport and revises the role of Cr$_2$O$_3$ in transparent electronics. Additionally, our results on mobility complement previous studies on defect formation indicating that the commonly observed $p$-type behavior is extrinsic. These insights provide a complete chemical-transport paradigm for Cr$_2$O$_3$, re-evaluating its role in functional transparent electronic and magneto-optoelectronic applications
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Instrumentation and Methods for Astrophysics

A nonrelativistic radiative transfer module for Idefix

Nicolas Scepi and Geoffroy Lesur

Radiation magnetohydrodynamic (RMHD) simulations are essential for comparisons with observations, particularly in the regime where fluids and radiation are dynamically coupled. Although computationally expensive, RMHD is becoming increasingly accessible with the advent of exascale computing. However, only a few public RMHD codes are currently able to fully exploit the diversity of modern accelerated architectures. We present a nonrelativistic radiative transfer module for the public magnetohydrodynamic code IDEFIX; it is built on the Kokkos library to ensure performance portability. Our goal is to provide a user-friendly RMHD code capable of running efficiently on current and future exascale supercomputers. The radiative transfer module is based on the M1 approximation and implemented using a split explicit-implicit scheme. A reduced speed of light approximation is employed to alleviate the timestep constraint imposed by radiation. The module supports several radiation Riemann solvers and Cartesian, cylindrical, and spherical geometries in one, two, and three dimensions. The implicit step relies on a simple matrix inversion, ensuring both robustness and high performance. Users can choose between built-in opacity models or supply tabulated opacities and custom user-defined functions. The radiative module of IDEFIX demonstrates excellent performance on accelerated architectures, including the AMD MI250X and MI300 partitions of the AdAstra supercomputer. On MI250X nodes, it achieves up to $7.\times 10^8$ cell updates per second per node, at a computational cost only 1.6 times higher than a pure magnetohydrodynamic simulation. These results establish IDEFIX as a fast, robust, and portable RMHD code suitable for the wider community.
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Quantum Physics

Complex frequency-dependent quadrature squeezing in semiconductor lasers

Daniele Nello, Giuseppe Patera and Lorenzo Columbo

We present a comprehensive study of quadrature squeezing in a quantum well laser based on a fully quantum Langevin approach. We compute the frequency-resolved squeezing map of the laser field and identify optimal squeezing curves, revealing, for the first time to our knowledge, both frequency-dependent squeezing and complex or hidden squeezing in a semiconductor laser. We further analyse the role of the linewidth enhancement factor (alpha-factor) in the emergence of these features. Our results establish semiconductor lasers as a platform for the generation of non-classical light and open new perspectives for their application in quantum communication and sensing.
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Astrophysics of Galaxies

Quantifying the inside-out formation of disk galaxies at $1.5 \le z \le 3.0$

Laura DeGroot, Swara Ravindaranath, Karmellah Buttler et al. (+1 more)

We examine the properties of galaxies at $1.5\le z\le3.0$ in the Extended Groth Strip (EGS) field to explore inside-out disk growth. We take advantage of the high-resolution James Webb Space Telescope (JWST) imaging and imaging from the Hubble Space Telescope (HST) to measure rest-frame optical and rest-frame UV half-light radii of the galaxies at comparable spatial resolution. We also examine the relation between structural properties and star formation rates, mass, and dust attenuation. While previous studies have inferred inside-out disk formation via the comparison of rest-optical and rest-UV radii using HST images, this study advances this knowledge by using the unprecedented resolution of JWST. We find evidence of inside-out disk formation from, on average, larger UV sizes than optical for galaxies across all redshifts. While previous studies suggested that this could be accounted for due to dust, we find that measurements with the improved resolution of the JWST support this size difference, after accounting for dust attenuation. We also observe that majority of galaxies with clumpy morphologies ($n < 0.5$) exhibit larger UV sizes than rest-optical because the star formation is distributed in multiple star forming clumps or mergers. We observe correlations in both the optical and UV for the size-mass relation, which are consistent with previous results but we find lower values for the slope of the power-law relation of the rest-optical fit, based on robust measurements from JWST images compared to the low resolution HST images used in previous studies.
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All authors Laura DeGroot, Swara Ravindaranath, Karmellah Buttler, Taliah Lansing

High Energy Physics (Theory)

Charged and rotating near-horizon geometries in five dimensions

Alex Colling and Jun Liu

We present new charged and rotating near-horizon geometries in five-dimensional Einstein-Maxwell theory in closed analytic form. The solutions can be parametrised by the charge and two independent angular momenta. We also generalise these near-horizon geometries to theories with an additional Chern-Simons term in the action multiplied by an arbitrary coupling constant. The new solutions have the same entropy relations as expected for charged versions of extremal Myers-Perry black holes and for rotating versions of extremal Reissner-Nordström-Tangherlini black holes, but they do not reduce to the Myers-Perry horizon in the vacuum limit. The horizon cross-sections are spherical and carry a Sasakian structure. We exploit this structure to prove a characterisation of our solutions: without any symmetry assumptions, they are the most general rotating extremal horizons for which the co-rotating electric field is a (non-zero) constant. We further extend this construction to higher dimensions, where we show that any Sasaki-Einstein manifold generates a two-parameter family of charged and rotating horizons.
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Solar and Stellar Astrophysics

A Stellar Role Reversal: Multiple Features in the Mass and Mass Ratio Distributions of Merging Binary Black Holes from Stable Mass Transfer

Gina Chen, Katelyn Breivik and Lieke A. C. van Son

Observations of gravitational wave events have enabled the measurement of the merging binary black hole (BBH) mass function. This mass function encodes the physical interactions which shape the formation and evolution of BBHs. In this work we investigate how the stable mass transfer (SMT) channel of BBH formation imprints onto the BBH primary mass and mass ratio distributions. We use both an analytic framework and binary population synthesis to show how assumptions about mass transfer accretion efficiency and mass transfer stability affect the BBH mass distribution. Under the assumption of conservative mass transfer, we find that the SMT channel produces two observationally distinct subpopulations: a high primary mass, near equal mass ratio population formed through mass ratio reversal (MRR), and a low primary mass non-MRR subpopulation. The mass range where MRR occurs is determined by assumptions about binary SMT. In particular, we find that the stability criteria for mass transfer at different stellar evolutionary stages carve out complementary regions in the primary-mass–mass-ratio plane, separating the MRR and non-MRR populations into distinct peaks at high and low primary mass respectively. Our results imply that the physics of SMT creates distinct features in gravitational wave populations which current and near future gravitational wave detectors may be able to resolve.
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Superconductivity

Fluctuation-Induced Magnetoelectric Effect in Noncentrosymmetric Superconductors

Jaglul Hasan, Daniel Shaffer, Maxim Dzero et al. (+1 more)

We study the effect of superconducting fluctuations on the spin susceptibility and NMR relaxation rate in noncentrosymmetric two-dimensional materials above the superconducting transition temperature, considering arbitrary strength of impurity scattering. Employing a microscopic model with linear Rashba spin-orbit coupling, we show that superconducting fluctuations give rise to a direct contribution to the spin susceptibility through fluctuation-induced Cooper pairs. This fluctuation-driven magnetoelectric effect is possible even for purely $s$-wave singlet pairing, a mechanism that is forbidden in centrosymmetric systems. It competes with the reduction of the susceptibility below the Pauli value arising from the combined effects of the suppression of the density of states and quantum-interference localization processes. In contrast, superconducting fluctuations enhance the NMR relaxation rate above its normal-state Korringa value, with spin-orbit coupling providing an additional amplification of this effect.
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All authors Jaglul Hasan, Daniel Shaffer, Maxim Dzero, Alex Levchenko

Solar and Stellar Astrophysics

Cepheids with giant companions III. Evolutionary modeling of nine binary double Cepheids from the Milky Way and Magellanic Clouds

F. Espinoza-Arancibia, B. Pilecki, M. Catelan et al. (+3 more)

Binary double (BIND) Cepheids are systems comprising two Cepheid components. This feature provides important constraints that allow us to reveal the origin of Cepheids, trace their evolution, and test pulsation theory. Ten BIND Cepheids are now known, with only one having its parameters determined. We aim to estimate the physical parameters of the components of nine BIND Cepheids in the Magellanic Clouds and the Milky Way, investigate their evolutionary configurations, and formation scenarios. We also expand the parameter space of characterized individual Cepheids in mass, radius, period, and metallicity. We extended the recently introduced $q$-PED method to BIND Cepheids, combining observational constraints with theoretical pulsation and evolutionary models. We considered all consistent configurations (first-crossing, blue-loop, and mixed) as viable solutions. Probabilistic and observational constraints, including spectroscopic mass ratios for two systems, were then used to discriminate between them. We obtained new $q$-PED estimates of mass, radius, temperature, luminosity, and age for 18 Cepheids with previously unknown physical parameters. For one Galactic system, the spectroscopic mass ratio $q_s=0.84\pm0.04$ indicates a first-crossing plus a blue-loop Cepheid solution. This mass ratio, along with the predicted mass ratios lower than unity for two other systems, suggests past binary interactions and a likely merger origin for one component. We derive a new period–mass–radius relation and mass–luminosity relation covering the mass range $2.3-4.6$ M$_\odot$. This work provides the first mass estimates for Cepheids in the SMC, extending the lower Cepheid mass limit down to 2.3 M$_\odot$. Binary interactions in the past evolution of Cepheids may be common, affecting up to 40% of our systems with two clear cases and two more if blue loop Cepheids are preferred.
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All authors F. Espinoza-Arancibia, B. Pilecki, M. Catelan, V. Hocdé, I. B. Thompson, W. Gieren

Superconductivity

New Superconductors in the PtPb$_3$Bi Structure Type

Lior Verbitsky, Amira Merino, Scott B. Lee et al. (+8 more)

The quest for new superconductors is of both fundamental and technological importance. Recently, an artificial intelligence method correctly predicted PtPb$_3$Bi to be a superconductor. In this work, we find superconductivity in the newly synthesized $M$Pb$_{4-x}$Bi$_x$ ($M$ = Au, Pd, and Rh), of which PtPb$_3$Bi is a member. When $M$ = Ni, whose radius is considerably smaller, the structure instead collapses into the different, Pb-substituted NiBi$_3$ type. Interestingly, the stoichiometric parameter $x$ shifts across the three compounds to keep the total valence electron count close to 20 per formula unit. The superconducting transitions occur at 4.9, 4.2, and 3.4 K, for $M$ = Au, Pd, and Rh, respectively. Using electrical resistivity, magnetization, and specific heat measurements, we establish the bulk nature of the superconducting state and determine the critical fields, characteristic length scales, and anisotropy ratios. All three compounds are moderately anisotropic type-II superconductors, with modest upper critical field anisotropies of $H_{c2}^{\parallel c}/H_{c2}^{\perp c} \approx 1.2$ to $1.5$. These results establish $M$Pb$_{4-x}$Bi$_x$ as a family of anisotropic superconductors and a platform for studying how site disorder and Pb-Bi mixing govern superconductivity in heavy-element intermetallics.
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All authors Lior Verbitsky, Amira Merino, Scott B. Lee, Jaime M. Moya, Sigalit Aharon, Fatmagül Katmer, Sudipta Chatterjee, Grigorii Skorupskii, Josh Leeman, Gabrielle Carrel, Leslie M. Schoop

Mathematical Physics

The Colored Hofstadter Butterfly as a Many-Body Quantum Hall Phase Diagram

Giovanna Marcelli, Tadahiro Miyao, Domenico Monaco et al. (+2 more)

We prove that the colored Hofstadter butterfly has a many-body interpretation for a broad class of weakly interacting lattice fermion systems. Starting from a spectral gap of a Hofstadter-like one-particle Hamiltonian at arbitrary magnetic flux $b$, we construct an open region in the three-dimensional parameter space $(b,\mu,\lambda)$ of magnetic field, chemical potential, and interaction strength on which the infinite-volume interacting system has locally unique gapped ground states. The construction combines quasi-adiabatic continuation in the interaction strength with denominator-independent magnetic perturbation estimates, and therefore covers both commensurate and incommensurate fluxes, where no finite magnetic unit cell exists. On connected uniformly gapped regions meeting the non-interacting plane $\lambda=0$, we prove a many-body gap-labeling theorem: the Hall conductivity appearing in the macroscopic Ohm's law is constant and quantized, satisfying $2\pi\sigma^{\mathrm{H}}\in\mathbb{Z}$. Thus the integer colors of the non-interacting Hofstadter butterfly persist as Hall-conductivity labels of interacting quantum Hall phases.
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All authors Giovanna Marcelli, Tadahiro Miyao, Domenico Monaco, Stefan Teufel, Marius Wesle

Quantum Physics

A Survey of Quantum Programming Languages

Quan Do, Hersh Gupta, Xiyuan Cao et al. (+5 more)

Quantum computing has seen multiple recent breakthroughs and is getting closer to demonstrations of an exponential advantage over classical computing for certain problems. Programmers will require high-level, general-purpose, executable programming languages to express quantum solutions clearly and effectively, and the field has already produced a wide variety of such languages. This paper presents a language classification framework and uses it to survey ten popular quantum programming languages. The findings include conceptual and experimental comparisons that result in a list of challenges for future language design.
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All authors Quan Do, Hersh Gupta, Xiyuan Cao, Aarav Pabla, Pranav Singamsetty, Evan O'Grady, Keli Huang, Jens Palsberg

High Energy Physics (Phenomenology)

Thermal Emission of Dark Photons from Earth's Core

Hooman Davoudiasl

Dark photons in the sub-eV regime may be produced by the Earth's hot core, representing a much less extreme environment than stellar cores. We consider this possibility and estimate constraints on the kinetic mixing parameter $\varepsilon$ that governs dark photon coupling to charged particles, using Earth core cooling arguments and via dark matter direct detection experiments. Our estimates do not find new constraints on the relevant parameter space from these considerations. Depending on the underlying parameters governing the thermal production of dark photons in the Earth, either core cooling or a future experiment, like Oscura with 30 kg-yr of exposure, can constrain $\varepsilon$ about one order of magnitude above the current astrophysical bounds, over the dark photon mass range $\sim 10^{-4}-0.1$~eV.
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Astrophysics of Galaxies

Cluster vs Field: Clear Evidence for a Morphology-Density Relation in All Environments at $z\sim1.6$

Westley Brown, Adam Muzzin, Jasleen Matharu et al. (+6 more)

We explore the relationship between galaxy structure, stellar mass, and local galaxy density in three SpARCS clusters at $z\sim1.6$ and compare with field galaxies from the 3D-HST survey. Our cluster and field data include: 1) unprecedented multiband photometry, allowing for accurate stellar mass estimates; 2) extensive slit and grism spectroscopy targeting both star-forming and quiescent galaxies, allowing for high-accuracy local density measurements; and 3) deep imaging in F160W, allowing for accurate rest-frame optical morphologies. Using Sérsic index measured in rest-frame R-band, we classify galaxies as disk-like, bulge-like, and intermediate. Our sample includes 111 cluster galaxies and 458 field galaxies with reliable Sérsic measurements. We find that a morphology-density relation is already in-place in both cluster and field galaxies at $z\sim1.6$, such that as local density increases, the fraction of bulge-like galaxies increases and disk-like galaxies decreases. Both samples show similar positive trends between median Sérsic index and local density. Additionally, we find a general positive relationship between Sérsic index and stellar mass. The majority of galaxies remain disk-like until reaching stellar masses above $10^{10.25} M_\odot$ in the cluster or $10^{10.8} M_\odot$ in the field, however, we cannot conclude whether the differences in stellar mass trends are significant. Overall, our results show clear morphology-density and morphology-mass relations in place at $z\sim1.6$ and oppose the idea that cluster-specific processes are solely responsible the morphology-density relation. Our data further suggest that the morphology-density relation may be independent of global environment at this epoch.
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All authors Westley Brown, Adam Muzzin, Jasleen Matharu, Gillian Wilson, Julie B. Nantais, Ben Forrest, Ricardo Demarco, Allison Noble, Tracy Webb

High Energy Physics (Phenomenology)

Supercool with PPO: Exploring Supercooled Phase Transitions via Reinforcement Learning

Wan-Zhe Feng, Zong-Huan Ye and Zi-Hui Zhang

Gravitational waves from cosmological first-order phase transitions provide a powerful probe of hidden sectors and beyond the Standard Model physics. However, identifying phenomenologically relevant benchmark points remains computationally challenging, since viable and detectable signals typically occupy only a small fraction of the scanned parameter space. In this work, we introduce a reinforcement learning strategy based on Proximal Policy Optimization (PPO) to accelerate the search for gravitational wave signals from supercooled phase transitions in a minimal dark $U(1)_x$ sector. We construct a numerical reinforcement learning environment that maps the microscopic model parameters to the corresponding phase transition and gravitational wave observables, using a gauge-independent low-temperature formulation of the effective action. Several reward designs are developed to guide the agent toward parameter regions producing large gravitational wave amplitudes, broad frequency coverage, and detector sensitive benchmark points. We compare the PPO scans with conventional Monte Carlo scans in both narrow and broad windows of the $U(1)_x$ vacuum expectation value. Our results demonstrate that PPO provides an efficient goal-directed search strategy for gravitational wave phenomenology and offers a broadly applicable framework for learning-assisted exploration of high-dimensional scientific parameter spaces.
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Solar and Stellar Astrophysics

Prediction for IMAP: Revealing the Role of the Solar Magnetic Field in the Heliotail

M. Kornbleuth and M. Opher

The classic paradigm of the heliosphere considered the solar magnetic field as having a passive role in the heliosheath, yet Opher et al. (2015) and Drake et al. (2015) suggested that the solar magnetic field plays an active role by collimating the solar wind plasma. Previous work has suggested that high-latitude lobes observed by IBEX-Hi energetic neutral atom (ENA) maps are solely due to the fast/slow solar wind profile, yet other works have found that the solar magnetic field may play a role in organizing the lobes as well. Here, using an MHD solution with and without the solar magnetic field, we find that the fast/slow wind profile largely dictates the ENA profile up to $\sim$10-18 keV. Beyond this energy, the collimation effects are more prominent and the fast/slow solar wind profile no longer organizes the maps. The collimation creates two high latitude lobes. By 80 keV, the heliosphere with collimation yields an enhancement of ENAs of the high-latitude tail lobes compared to the low-latitude region by a factor of $\gtrsim$ 1.3, whereas the uncollimated heliosphere yields a ratio $<$ 1. Therefore, IMAP should be able to identify whether the solar magnetic field collimates the solar wind in the deep heliotail.
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