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Physics

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Sunday 2 August

General Relativity and Quantum Cosmology

Fully global numerical evolutions of the linearised spin-2 equation

Merlyn Barrer, Jörg Frauendiener, Jörg Hennig et al. (+3 more)

We study the linearised spin-2 field on conformally compactified Minkowski spacetime. Initial data are prescribed on past null infinity $\mathscr{I}^-$, and the system is evolved through the cylinder at spatial infinity to future null infinity $\mathscr{I}^+$. To avoid the development of logarithmic singularities and thereby preserve smooth peeling behaviour, we derive explicit conditions on the freely specifiable ingoing gravitational radiation $\psi_0$ at $\mathscr{I}^-$ that ensure regular initial data. For compactly supported data, we obtain necessary and sufficient integral conditions guaranteeing regularity and compact support of the full system. In the simplest cases, we construct examples of exact initial data, while for the general case, we present a numerical procedure that computes the remaining $\psi_k$ to obtain a full initial data set. We perform numerical evolutions using two gauges corresponding to compactification of either a neighbourhood of spatial infinity or the entire Minkowski spacetime, and demonstrate stable propagation of the system from $\mathscr{I}^-$ to $\mathscr{I}^+$. These results provide a step towards a framework for fully global simulations of gravitational radiation and clarify the role of initial data on $\mathscr{I}^-$ in determining asymptotic structure.
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All authors Merlyn Barrer, Jörg Frauendiener, Jörg Hennig, Oliver Markwell, Chris Stevens, Jed Thompson-Fawcett

Instrumentation and Methods for Astrophysics

Hard X-Ray Focal-Plane Compton Spectro-Polarimeter: Detector Development and Sensitivity Evaluation

Abhay Kumar, Tanmoy Chattopadhyay, Santosh V. Vadawale et al. (+1 more)

The scientific potential of X-ray polarimetry has long been recognized, yet the challenges of measuring polarization have left it largely unexplored, mainly in the hard X-ray regime. With the advent of hard X-ray focusing optics, sensitive focal-plane Compton polarimeters are now feasible. An early example is CXPOL (Compton X-ray Polarimeter), developed at Physical Research Laboratory (PRL), India, which demonstrated 20 - 80 keV polarimetric capabilities using a plastic scatterer and a CsI(Tl) absorber array. The CXPOL prototype demonstrated polarimetric capabilities in the 20 - 80 keV range, establishing a foundation for further development. Building on this concept, we evaluate a hard X-ray spectro-polarimeter employing a position-sensitive plastic scatterer surrounded by position-sensitive absorber detectors. This geometry enables efficient reconstruction of Compton events and allows combined polarimetric and spectroscopic measurements via interaction positions and deposited energies in the detectors. We evaluate key performance parameters of the revised configuration of the second version of the CXPOL. Using Geant4 simulations, we assess key performance parameters, including modulation factor, polarimetric efficiency, and expected sensitivity with modern hard X-ray optics. We also present the characterization results of first prototype of a 100x20x5 mm3 NaI(Tl) absorber read out on both ends by silicon photomultiplier (SiPM) array operating in coincidence, evaluating energy and position resolution and light-output variation along the detector. The coincidence readout also reduces SiPM background by an order of magnitude. The results demonstrate the strong potential of a position-sensitive Compton- based focal-plane instrument for next-generation hard X-ray spectro-polarimetry.
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All authors Abhay Kumar, Tanmoy Chattopadhyay, Santosh V. Vadawale, N. P. S. Mithun

Instrumentation and Methods for Astrophysics

In orbit background for hard X-ray CubeSat polarimeters: case study of the CUSP mission in low-earth orbit

Abhay Kumar, Giovanni Lombardi, Riccardo Campana et al. (+45 more)

The CUbesat Solar Polarimeter (CUSP) project aims to measure the linear polarization of solar flares in the 25 - 100 keV hard X-ray band using a Compton scattering polarimeter. CUSP is a project in the framework of the Alcor Program of the Italian Space Agency aimed to develop innovative CubeSat technologies and missions. As part of CUSPs Phase B study, initiated in December 2024 and closed on July 2nd, 2026, estimating the in orbit background to optimize the signal-to-background ratio was one of the key objectives. In low-Earth orbit, the instrument is exposed to cosmic and albedo X-ray backgrounds, charged particles, and secondary radiation from the spacecraft and atmosphere. Simulating these contributions enables optimization of detector geometry and shielding to maximize signal-to-noise performance. We present initial in orbit background estimates for CUSP using a Geant4-based simulator. A detailed mass model of the CUSP has been implemented to simulate background components and estimate the background count rate in the CUSP orbit.
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All authors Abhay Kumar, Giovanni Lombardi, Riccardo Campana, Giovanni De Cesare, Sergio Fabiani, Ettore Del Monte, Andrea Alimenti, Enrico Costa, Mauro Centrone, Nicolas De Angelis, Sergio Di Cosimo, Giuseppe Di Persio, Pasqualino Loffredo, Gabriele Minervini, Fabio Muleri, Paolo Romano, Alda Rubini, Emanuele Scalise, Enrico Silva, Paolo Soffitta, Giovanni Cucinella, Vito Di Bari, Simone Di Filippo, Andrea Negri, Massimo Perelli, Dario Modenini, Andrea Curatolo, Nicolas Gagliardi, Daniele Pecorella, Alice Ponti, Paolo Tortora, Andrea Del Re, Davide Albanesi, Valerio Campamaggiore, Giulia de Iulis, Adam Ebrahim, Paolo Leonetti, Marco Schepis, Alessandro Zambardi, Ilaria Baffo, Pierluigi Fanelli, Costantino Zazza, Valerio Vagelli, Daniele Brienza, Immacolata Donnarumma, Matteo Merge, Emanuele Zaccagnino, Alessandro Turchi

Other Condensed Matter

Integer-Graded Reciprocal Skin Effect from Internal Rotation

Kin Hung Fung and C. T. Chan

A prominent class of reciprocal non-Hermitian skin effects has a $\Z_{2}$ topological classification, characterized by a parity invariant protected by reciprocity. We show that conserved internal rotation refines this classification into an unbounded integer-graded hierarchy. Every angular momentum channel is an exactly solvable asymmetric chain with its own integer point-gap winding, while conjugate channels accumulate at opposite edges so that reciprocity is preserved globally. For conserved channels, the classification contains one integer per conjugate pair, with the number of independent integers determined by the internal multiplet. Half-integer spin realizes the symplectic class AII$^{\dagger}$, whose $\Z_{2}$ index is recovered as the parity of the grading. Conjugate-channel mixing destroys the grading and leaves a critical, scale-free skin effect. A cyclic three-site lattice and a passive array of lossy resonators provide minimal realizations.
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Physics and Society

The Production of Policy Knowledge in the United States

Taegyoon Kim, Alexander Furnas and Dashun Wang

Policymaking relies on institutions that translate expertise into politically actionable knowledge. Yet little is known about how such knowledge is created, structured, and politically polarized, or how science shapes these processes. Using 2 million U.S. policy documents and nearly 1 million scientific citations from more than 200 think tanks and 100 government organizations, we analyze the supply side of science in policymaking: the production of policy knowledge. We find that think tanks are the dominant suppliers of science-based policy knowledge to government, but that this production has become increasingly politically polarized, driven primarily by growing insularity among left-leaning institutions. We further find that science is linked to lower polarization, as policy documents grounded in scientific evidence, especially those citing high-impact science, are less ideologically segregated and occupy more central positions in policy knowledge networks. These results reveal the potential of scientific expertise to shape and, at times, bridge the ideological landscape of policy knowledge production. Amid rising political polarization and the growing role of science in policymaking, understanding how policy knowledge is produced and how scientific expertise relates to its ideological structure is essential to strengthening the informational foundations of democratic governance.
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Astrophysics of Galaxies

Dust Seeding Molecules in a Massive Protostar – Detection of TiO in Orion Source I

Ziwei E. Zhang, Nami Sakai, Marcelino Agundez et al. (+16 more)

We report the first detection of TiO in star-forming regions based on Atacama Large Millimeter/submillimeter Array observations of Orion Source I, a well-characterized massive protostar. Multiple rotational transitions are identified, with emission spatially resolved within $\sim 50$ au, showing a compact distribution with a velocity structure consistent with the base of a rotating outflow. The spatial and velocity distributions of TiO are consistent with those of AlO, with both species being key dust seeding refractory molecules. The column density of TiO is derived to be $(3.0 \pm 0.4)\times10^{15}\ {\rm cm^{-2}}$, corresponding to $X_{\rm TiO/SiO} \sim 12.8 \pm 1.7 \times10^{-3}$, higher than CI chondrites and indicative of efficient dust-to-gas conversion near the protostar. The detection of TiO, a key dust seeding species, offers important constraints on refractory chemistry and the formation environments of primitive minerals, linking astrochemical processes in protostellar systems to the earliest stages of Solar System material formation.
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All authors Ziwei E. Zhang, Nami Sakai, Marcelino Agundez, Linda Podio, Claudio Codella, Tomoya Hirota, Adam Ginsburg, Brett McGuire, Nadia M. Murillo, Yuki Okoda, Yoko Oya, Giovanni Sabatini, Aki Takigawa, Kei E. I. Tanaka, Yichen Zhang, Qiuyi Luo, Yu Cheng, Izaskun Jimenez-Serra, Shogo Tachibana

Materials Science

Updated Tkatchenko Scheffler method and assessment of dispersion methods for alkali-containing systems

Aaron M. Schankler, Ruyi Song, Sampreeti Bhattacharya et al. (+5 more)

The Tkatchenko-Scheffler (TS) pairwise method to calculate dispersion interactions is a widely used approach to incorporate missing long-range van der Waals contributions in semilocal and hybrid density functional calculations. Despite subsequent many-body extensions, this formulation remains widely used. In 2018, Fedorov et al. reported updated van der Waals radii to the seminal work published in 2009. The present work examines the accuracy of the TS method with updated van der Waals radii (TS_2018), coupled with the semilocal Perdew-Burke-Ernzerhof density functional, for structural predictions of semiconducting and insulating materials. Special attention is paid to materials containing alkali elements, for which the TS_2009 method exhibits a large overbinding, associated with potentially large errors in predicted atomic structures. We also consider a narrower reformulation (TS_alkali) where only the the alkali atoms are corrected, so the method remains otherwise compatible with TS_2009. We compare these methods with a broader set of dispersion corrections–the DFT-D3 method, the exchange-hole dipole moment method, and the beyond-pairwise, nonlocal many-body dispersion method–for ionic and alkali-containing systems more generally. We examine equilibrium geometry predictions for 45 inorganic solid compounds as well as three Cs-containing halide perovskites, CsPb$X_3$ ($X$ = Cl, Br, I). Our results show that the updated van der Waals radii in the TS_2018 and TS_alkali methods resolve the overbinding that is present with TS_2009 in alkali-containing systems, bringing predictions into closer agreement with other dispersion methods. For the halide perovskites, method-dependent differences in predicted cell volumes and shapes persist, and no approach performs with perfect accuracy on all metrics for all three materials.
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All authors Aaron M. Schankler, Ruyi Song, Sampreeti Bhattacharya, Ela Lucas, Lee Hampton III, Alexandre Tkatchenko, Yosuke Kanai, Volker Blum

High Energy Physics (Phenomenology)

Search for active-sterile neutrino transitions using Pierre Auger Observatory data

The Pierre Auger Collaboration: A. Abdul Halim, P. Abreu, M. Aglietta et al. (+347 more)

We investigate the sensitivity of the Pierre Auger Observatory to physics beyond the Standard Model arising from magnetic-moment-induced transitions between active and heavy sterile neutrinos. Such dipole portal interactions can enhance neutrino-nucleon cross sections above a kinematic threshold set by the sterile neutrino mass, leading to observable modifications of neutrino detection rates at ultrahigh energies (UHE). We estimate the impact of these interactions on both down-going and Earth-skimming neutrino detection channels, the contrasting responses of which enable discrimination between an enhanced neutrino flux and a modified interaction cross section. Using the non-observation of UHE neutrino candidates, we derive neutrino-flux-dependent constraints with 90% confidence-level on the transition magnetic moment for sterile neutrino masses in the range 1 TeV-100 TeV. Under the assumed flux scenarios, the resulting flavor-independent limits extend existing bounds into previously unexplored parameter space.
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All authors The Pierre Auger Collaboration: A. Abdul Halim, P. Abreu, M. Aglietta, M. Ahmed, I. Allekotte, K. Almeida Cheminant, R. Aloisio, J. Alvarez-Muñiz, A. Ambrosone, J. Ammerman Yebra, L. Anchordoqui, B. Andrada, L. Andrade Dourado, L. Apollonio, C. Aramo, J.C. Arteaga Velázquez, P. Assis, G. Avila, E. Avocone, A. Bakalova, Y. Balibrea, A. Baluta, F. Barbato, A. Bartz Mocellin, O. Batalla Cruz, J.P. Behler, C. Berat, M.E. Bertaina, M. Bianciotto, P.L. Biermann, V. Binet, K. Bismark, T. Bister, J. Biteau, J. Blazek, J. Blümer, M. Boháčová, D. Boncioli, C. Bonifazi, N. Borodai, J. Brack, P.G. Brichetto Orquera, S. Buitink, A. Bwembya, T.R. Caba Pineda, K.S. Caballero-Mora, S. Cabana-Freire, L. Caccianiga, J. Caraça-Valente, R. Caruso, A. Castellina, F. Catalani, G. Cataldi, L. Cazon, M. Cerda, B. Čermáková, A. Cermenati, K. Cerny, J.A. Chinellato, J. Chudoba, L. Chytka, R.W. Clay, A.C. Cobos Cerutti, R. Colalillo, R. Conceição, A. Condorelli, G. Consolati, M. Conte, F. Convenga, D. Correia dos Santos, P.J. Costa, C.E. Covault, M. Cristinziani, C.S. Cruz Sanchez, S. Dasso, K. Daumiller, B.R. Dawson, R.M. de Almeida, E.-T. de Boone, B. de Errico, J. de Jesús, S.J. de Jong, J.R.T. de Mello Neto, I. De Mitri, D. de Oliveira Franco, F. de Palma, V. de Souza, E. De Vito, A. Del Popolo, O. Deligny, N. Denner, K. Denner Syrokvas, L. Deval, A. di Matteo, C. Dobrigkeit, J.C. D'Olivo, L.M. Domingues Mendes, T. Dominguez, Y. Dominguez Ballesteros, Q. Dorosti, R.C. dos Anjos, J. Ebr, F. Ellwanger, R. Engel, M. Erdmann, A. Etchegoyen, C. Evoli, H. Falcke, G. Farrar, A.C. Fauth, T. Fehler, F. Feldbusch, A. Fernandes, M. Fernández Alonso, B. Fick, J.M. Figueira, P. Filip, A. Filipčič, B. Flaggs, A. Franco, M. Freitas, T. Fujii, A. Fuster, C. Galea, B. García, C. Gaudu, P.L. Ghia, U. Giaccari, M. Giammarco, C. Glaser, F. Gobbi, F. Gollan, G. Golup, P.F. Gómez Vitale, J.P. Gongora, N. González, D. Góra, A. Gorgi, M. Gottowik, F. Guarino, G.P. Guedes, Y.C. Guerra, L. Gülzow, S. Hahn, P. Hamal, M.R. Hampel, P. Hansen, V.M. Harvey, A. Haungs, M. Havelka, T. Hebbeker, C. Hojvat, J.R. Hörandel, P. Horvath, M. Hrabovský, T. Huege, A. Insolia, P.G. Isar, M. Ismaiel, P. Janecek, V. Jilek, K.-H. Kampert, B. Keilhauer, V.V. Kizakke Covilakam, H.O. Klages, M. Kleifges, A. Klingel, J. Köhler, F. Krieger, M. Kubatova, N. Kunka, B.L. Lago, N. Langner, N. Leal, M.A. Leigui de Oliveira, Y. Lema-Capeans, A. Letessier-Selvon, I. Lhenry-Yvon, L. Lopes, M. Mallamaci, S. Mancuso, D. Mandat, P. Mantsch, A.G. Mariazzi, C. Marinelli, I.C. Mariş, G. Marsella, D. Martello, S. Martinelli, O. Martínez Bravo, A. Martínez-Mendez, M.A. Martins, H.-J. Mathes, J. Matthews, G. Matthiae, E. Mayotte, S. Mayotte, P.O. Mazur, G. Medina-Tanco, D. Melo, A. Menshikov, C. Merx, S. Michal, M.I. Micheletti, L. Miramonti, M. Mogarkar, S. Mollerach, F. Montanet, L. Morejon, K. Mulrey, R. Mussa, W.M. Namasaka, S. Negi, L. Nellen, K. Nguyen, G. Nicora, M. Niechciol, D. Nitz, D. Nosek, A. Novikov, V. Novotny, L. Nožka, A. Nucita, L.A. Núñez, S.E. Nuza, J. Ochoa, M. Olegario, C. Oliveira, L. Östman, M. Palatka, J. Pallotta, G. Parente, T. Paulsen, M. Pech, J. Pękala, R. Pelayo, C. Pérez Bertolli, L. Perrone, S. Petrera, T. Pierog, M. Pimenta, M. Platino, P. Privitera, C. Priyadarshi, M. Prouza, K. Pytel, S. Querchfeld, J. Rautenberg, D. Ravignani, J.V. Reginatto Akim, M.Z. Rennó, A. Reuzki, J. Ridky, F. Riehn, M. Risse, V. Rizi, B. Rocha Moldes, E. Rodriguez, G. Rodriguez Fernandez, J. Rodriguez Rojo, S. Rossoni, M. Roth, E. Roulet, A.C. Rovero, A. Saftoiu, M. Saharan, F. Salamida, H. Salazar, G. Salina, P. Sampathkumar, N. San Martin, J.D. Sanabria Gomez, F. Sánchez, F.M. Sánchez Rodriguez, E. Santos, F. Sarazin, R. Sarmento, R. Sato, P. Savina, V. Scherini, H. Schieler, M. Schimp, D. Schmidt, O. Scholten, H. Schoorlemmer, P. Schovánek, F.G. Schröder, J. Schulte, T. Schulz, S.J. Sciutto, M. Scornavacche, A. Sedoski, S. Sehgal, S.U. Shivashankara, G. Sigl, K. Simkova, F. Simon, R. Šmída, S. Soares Sippert, P. Sommers, S. Stanič, J. Stasielak, P. Stassi, S. Strähnz, M. Straub, T. Suomijärvi, A.D. Supanitsky, Z. Svozilikova, Z. Szadkowski, F. Tairli, A. Tapia, C. Taricco, C. Timmermans, O. Tkachenko, P. Tobiska, C.J. Todero Peixoto, B. Tomé, A. Travaini, P. Travnicek, C. Trimarelli, M. Tueros, M. Unger, R. Uzeiroska-Geyik, L. Vaclavek, M. Vacula, I. Vaiman, J.F. Valdés Galicia, L. Valore, P. van Dillen, E. Varela, V. Vašíčková, A. Vásquez-Ramírez, D. Veberič, I.D. Vergara Quispe, S. Verpoest, V. Verzi, J. Vicha, S. Vorobiov, J.B. Vuta, A.A. Watson, A. Weindl, M. Weitz, L. Wiencke, H. Wilczyński, B. Wundheiler, B. Yue, A. Yushkov, E. Zas, D. Zavrtanik, M. Zavrtanik

Instrumentation and Methods for Astrophysics

MiraSOL: a DMD-based spectrograph for resolved solar spectroscopy

Christian Robles, Suvrath Mahadevan and Lawrence Ramsey

We present the science motivation, preliminary design requirements, device laboratory testing and a prototype for an new experimental platform for solar observations, MiraSOL. MiraSOL will use digital micromirror technology to actively select regions on the solar disk for spectroscopic observation to determine the spatially dependent radial velocity signatures of stellar variability, and can create transits on the solar disk to probe the effects of stellar contamination on exoplanet transmission spectra. MiraSOL uses the Texas Instruments DLP801RE as a spatial light modulator to allow a mask, with 3 arcsecond spatial sampling per micromirror, capable of resolving features on the solar disk. This instrument will have a fiber output which can then be coupled with state-of-the-art extreme precision radial velocity (EPRV) spectrometers, such as HPF or NEID, for high resolving power, stable spectra of sunspots and plage, or a low resolution spectrometer for studies of stellar contamination in transit spectra. We discuss a 60 Hz flicker signal we discovered, likely due to the commercial off-the-shelf (COTS) evaluation board of the digital micromirror device electronics. We also build a proof-of-concept prototype and demonstrate imaging and pixel-level control of the full solar disk to demonstrate the feasibility of this technology.
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Physics Education

The First Variational Formula and the Ostrogradsky Formalism

Drew Watson, Matthew Pontius and Charles Torre

We present a derivation at a level suitable for undergraduates of the Ostrogradsky formalism for Lagrangians in classical mechanics that depend upon an arbitrary number of time derivatives of the configuration. From the boundary term in the first variation of the Lagrangian we derive the Ostrogradsky formulas that define the Hamiltonian formulation of mechanical systems. Worked examples, exercises, and applications to the literature are also provided. An accompanying computer program that implements the formalism is discussed in the Supplementary Materials, and code for computing Hamiltonians via the Ostrogradsky formalism is provided in the Supplementary Materials and in a GitHub repository.
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High Energy Physics (Phenomenology)

What are the consequences of independent factorization and renormalization scales?

T.C. Rogers and R.M. Whitehill

It is common for separate factorization and renormalization scales to be discussed in connection with phenomenological applications of QCD factorization theorems. We observe that simultaneously preserving renormalization group invariance, Ward identities, and the basic sum rules in the definitions of parton densities forces these scales to be equal. The statement applies to generalized pole subtraction schemes that use dimensional regularization and to collinear factorization theorems for basic processes like deep inelastic scattering. We discuss implications for estimating the effects of scale sensitivity in phenomenological calculations, consistent extractions of Standard Model parameters alongside parton densities in global QCD analyses, and generally connecting phenomenologically extracted parton densities to first principles non-perturbative techniques like lattice QCD.
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Disordered Systems and Neural Networks

Griffiths phase in clique percolation in random geometric graphs

Vasilii Tiselko, Olga Valba and Alexander Gorsky

In this study, we discuss the clique percolation in the ensembles of random geometric graphs with different kernels that quantify the geometrical constraints. For the sharp cut-off we find the wide Griffiths phase of extended criticality with the power-law behavior. One boundary of the Griffiths phase is the generalization of a percolation critical point for the ER ensemble when the percolation within the large but finite cluster emerges. The second boundary corresponds to the point in the parameter space when the percolation in the entire clustered system becomes available. For the power-law kernel, richer behavior with a clique-size-dependent boundary between the effective ER and geometric regimes has been identified. The Griffiths phase in this case exists as well. Finally, the pattern with the exponential kernel has been analyzed. We briefly discuss the possible applications of our findings.
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Quantum Physics

Non-Hermitian photon number filtering using N00N state Bloch oscillations

Sean Crowe, Joanna Ptasinski, Melvin Pascoguin et al. (+1 more)

We explore Bloch oscillations of $N=1$ and $N=2$ photonic N00N states, using an array of linearly growing effective index waveguides with a simulated asymmetric loss profile. Starting with equal probability input $N=1$ and $N=2$ N00N states, and siphoning off a portion of the waveguides near the half Bloch period, we selectively output specific photon number states. Tuning the input phase, we achieve dynamic switching between 2-photon dominated (80% of the output) and 1-photon dominated (90% of the output) cases. This offers a path to improved state preparation in photonic circuits used in computing and networking.
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All authors Sean Crowe, Joanna Ptasinski, Melvin Pascoguin, Stefan Evans

Quantum Physics

Spatial-Order Hierarchy of Time-Dependent Exchange-Correlation Potential

Naoki Negishi

Exact time-dependent density-functional theory (DFT) separates the exchange-correlation potential into interaction and kinetic-correlation components, but the structural relation between them remains unclear. We establish a representability constraint based on the off-diagonal expansion of the one-electron reduced density matrix (1RDM) relative to a chosen reference dynamics. A non-zero linear off-diagonal term of the 1RDM generates a current density beyond the representable space of the reference, while a nontrivial quadratic off-diagonal structure activates the kinetic-correlation component. The resulting hierarchy provides a criterion for assessing, from the spatial locality of electronic correlation, whether a given exchange-correlation functional or a more general electron-correlation approximation remains adequate. In a one-dimensional two-electron correlation quench, retaining the exact interaction component while setting the kinetic component to zero suppresses the density broadening of the exact evolution. These results establish a spatial-order hierarchy among the force components governing the density dynamics and provide an exact constraint for the construction and assessment of nonadiabatic approximations.
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Quantum Physics

Surface adsorbates suppress low-frequency noise for shallow nitrogen-vacancy centers

Zhiyang Yuan, David A. Fehr, Kalliope Zervas et al. (+5 more)

Shallow nitrogen-vacancy (NV) centers in diamond are promising nanoscale quantum sensors, yet their coherence is strongly limited by surface-induced noise. Surface adsorbates are widely believed to be a major source of decoherence. Here, we test this assumption by characterizing shallow single NV centers under ultrahigh vacuum (UHV) conditions, where the diamond surface is kept free of adsorbates, and comparing their behavior to ambient conditions. Surprisingly, we observe a ~4x reduction in the Hahn echo coherence time T2 in UHV. By combining Hahn echo measurements in the single-quantum (SQ) and double-quantum (DQ) bases, we separate contributions from different noise sources and find that both electric and magnetic noise are enhanced in UHV. In contrast, T1 measurements reveal an increased DQ T1 in UHV, indicating suppressed electric field noise in the ~100 MHz frequency regime. These results point to a modification of the surface noise spectrum upon adsorbate removal, with different frequency regimes arising from distinct microscopic mechanisms. Specifically, we find that the low frequency noise is consistent with increased surface charge in UHV that can be compensated by surface adsorbates in ambient conditions. Our findings highlight a complex and previously underappreciated role of surface adsorbates in shaping the noise environment of shallow NV centers, with important implications for nanoscale quantum sensing.
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All authors Zhiyang Yuan, David A. Fehr, Kalliope Zervas, Sorawis Sangtawesin, Lila V. H. Rodgers, Patryk Gumann, Michael E. Flatte, Nathalie P. de Leon

General Relativity and Quantum Cosmology · Cross-listed from math.NA

An analytical-numerical approach to the Emden-Fowler equation

Mihai Halic

We investigate the Emden-Fowler equation $u''=-x^ru^p, u(0)=1, u'(0)=0$, with roots in astrophysics, and study the qualitative and quantitative dependence of its solution on the parameters; the analytical work is paralleled by numerical simulations. A special attention is given to estimating the first zero $x_0$ of $u$ in terms of $r, p$. The results are used to address two apparently new issues: first, we solve EF backwards starting from $x_0$; second, we transform it into an overdetermined boundary value problem and decide when is this solvable.
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High Energy Physics (Phenomenology)

The CKM sector of the exceptional-Jordan programme: finite-Dirac mass moduli, two conditional angle estimates, and the weak-to-mass bridge

Tejinder P. Singh

The Standard Model does not determine quark masses or the CKM matrix. In the exceptional-Jordan programme, square-root masses occupy short $\operatorname{Sym}^{3}(\mathbf{3})$ chains. Compressing the symmetric-cube lift onto occupied nodes gives a root-mass operator whose square yields the proposed mass ratios, packaging that spectrum and relative left frames in one finite Dirac operator without deriving the frames. Conditional on the transport, virtual-node-amplitude, real-$(2,3)$ and balanced-quadrature choices, the no-fit layer gives $|V_{us}|=0.2371$ ($5.3\%$ high) and $|V_{cb}|=0.0422$ ($0.8\%$ high) at $M_Z$. The relation $|V_{ub}|/|V_{cb}|=\sqrt{m_u/m_c}$ is a factor two low; one complex long edge is fitted. The two balanced orientations give branches $(\varepsilon,\omega)=(0.002079,288.2^\circ)$ and $(0.005358,202.2^\circ)$, so the former $\varepsilon$ ratio is not robust and raw $\omega$ is convention-dependent. For an adopted $F_1$–$F_2$ family embedding, we construct an exact Peirce-changing Albert lift in $\mathfrak f_4(\mathbb C)$, reproducing conjugate up/anti-down transport and $\varphi_{12}=-2\chi$. For an adopted cyclic Majorana placement and real-linear projection, its completion has real $(e_4,e_3,e_6)$ support while the $e_1$ quadrature vanishes; $J_\ell=0$ and $\delta^\ell_{CP}=0$ or $\pi$ are compatibility results in this class. The minimal radial-quartic cyclic truncation has equal-magnitude full-rank extrema or a flat direction; a mixed Albert cubic gives stable alignment only in a chosen three-edge subspace. Six diagonal mass links plus three directed Peirce links would form a connected one-cycle nine-link graph if the Yukawa block is linear in the projected bridge. This is a candidate Arkani-Hamed et al. texture skeleton, not a derivation: family-vacuum selection, chiral projection and right-frame locking remain open.
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Quantum Physics

Automated Construction and Verification of Unextendible Product Bases

Zicheng Han, Wanchen Zhang, Fei Shi et al. (+1 more)

Unextendible product bases (UPBs) are important structures in quantum information theory, with applications to completely entangled subspaces, bound entanglement, and local indistinguishability. Since many properties and applications of UPBs are closely related to their cardinalities, one of the central problems in the study of UPBs is to determine whether UPBs of prescribed sizes exist in a given multipartite system. In this paper, we introduce a SAT-assisted framework based on decompositions of the \(N\)-dimensional hypercube. We define \(O_N\)-tile decompositions and prove a tile-to-UPB theorem: every \(O_N\)-tile decomposition induces a UPB through a construction based on tile-wise Fourier product bases and a global stopper state. We then encode the search for such decompositions as a Boolean satisfiability (SAT) problem and use SAT solvers to generate explicit instances. In terms of verification, we also implement a UPB verification algorithm based on local orthogonality graphs and unsaturated subspaces. The algorithm can be used to determine whether an arbitrary finite set of product states forms a UPB. Using this framework, we obtain UPBs of several sizes in some tripartite and quadripartite systems, including sizes \(13,14,\ldots,23\) in \(\mathbb C^3\otimes\mathbb C^3\otimes\mathbb C^3\). Moreover, the small-dimensional instances obtained here can serve as seed UPBs for recursive constructions, leading to further examples in larger multipartite systems.
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All authors Zicheng Han, Wanchen Zhang, Fei Shi, Xiande Zhang

Materials Science · Cross-listed from cs.AI

PolymerGPT: Multi-property Optimization with a Decoder-Based GPT Model for Generative Polymer Design

Charlie Pyle, Adarsh Gadari, C. Adrian Figg et al. (+3 more)

Polymer property prediction and inverse generative design targeting desired properties are two crucial tasks in machine learning-assisted polymer design. While the former has received considerable attention, there have been limited methods developed for the latter. Existing methods focus on single-property optimization in the generative process, whereas accurate prediction of macroscopic material behavior requires simultaneous control of multiple physical properties. In this paper, we provide a transformative framework for direct optimization of a large collection of polymer properties. We propose PolymerGPT, a decoder-based GPT model that incorporates up to 37 commonly used polymer properties into the generative process via learned conditioning prefixes. It also supports a scaffold condition that specifies a desired scaffold for predicted structures. Our experimental results demonstrate that PolymerGPT achieves exceptional performance for unconditional and conditional generation while maintaining high validity, uniqueness, and novelty. Conditioning on five key properties yields generated structures whose predicted values closely match all target properties simultaneously.
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All authors Charlie Pyle, Adarsh Gadari, C. Adrian Figg, Zhenquan Jia, Yaohang Li, Chunjiang Zhu

Mathematical Physics · Cross-listed from math.FA

Dense Hamiltonians at the Parseval Limit: The Noncommutative BH Constant is Exponential and the Quantum FEI Conjecture is False

Joseph Slote

For each $d\geq 1$ we construct a norm-1 Hermitian operator whose Pauli expansion contains $N(d)=\exp(\Omega(d^2))$ terms, each of degree $d$ and magnitude $1/\sqrt{N(d)}$ - the largest magnitude permitted by Parseval's identity. For comparison, if a bounded diagonal operator (or equivalently, a bounded degree-$d$ function on the Boolean cube) has $N(d)$ Pauli coefficients, all of magnitude $\Omega(1/\sqrt{N(d)})$, then $N(d)\leq \exp(\widetilde{O}(d^{1.5}))$. This construction implies the noncommutative Bohnenblust–Hille (BH) constant satisfies $\mathrm{BH}_{M_2}(d)\geq\exp(\Omega(d))$. Together with the upper bounds proved in prior work, this settles the asymptotic growth of $\mathrm{BH}_{M_2}(d)$ as exponential. Our lower bound also asymptotically separates $\mathrm{BH}_{M_2}(d)$ from the (classical) hypercube BH constant $\mathrm{BH}_{\{\pm 1\}}(d)$, which in turn is known to be subexponential: $\mathrm{BH}_{\{\pm 1\}}(d)\leq C^{\sqrt{d \log d}}$. Our Hamiltonians are also unitary and thus quantum Boolean functions in the sense of Montanaro and Osborne (2010). As such they refute the quantum Fourier Entropy-Influence conjecture of Bu et al. (2024), a natural generalization of the classical Fourier Entropy-Influence conjecture due to Friedgut and Kalai (1996).
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High Energy Astrophysical Phenomena

Spectral decoherence without depolarization in curvature radiation

A. G. Tevzadze and N. L. Shatashvili

Context: Fast radio bursts often exhibit strong linear polarization together with pronounced spectral structure. Yet in coherent curvature radiation, spectral decoherence and depolarization are not necessarily simultaneous. Aims: We investigate spectral and polarization coherence in curvature radiation from extended ultrarelativistic sources. Methods: Using the coherency matrix formalism together with an asymptotic phase expansion for a uniformly emitting extended source, we derive the spectral and polarization coherence properties of curvature radiation. Results: We show that spectral decoherence and depolarization are governed by distinct physical conditions and therefore develop on separate scales. Retardation phase variations suppress spectral coherence, whereas polarization remains largely preserved across the relativistic beaming cone, naturally producing a broad polarized but spectrally decoherent regime whose extent increases toward higher frequencies and larger Lorentz factors. Conclusions: Spectral decoherence without strong depolarization naturally arises in ultrarelativistic curvature radiation and may explain highly polarized fast radio bursts with strong spectral modulation or narrow band structure.
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High Energy Astrophysical Phenomena

Signatures of Lorentz violation in the bright ring for Sgr A* images from radiatively inefficient accretion flows

Cuiyu Zhao, Songbai Chen and Jiliang Jing

We have investigated the effects of Lorentz violation (LV) on the bright ring in Sgr A* images illuminated by the 230 GHz thermal synchrotron emission from radiatively inefficient accretion flows around a rotating LV black hole within the low-energy Hořava gravity framework. Our results reveal that the LV parameter reduces the bright ring diameter yet increases its width, luminosity, azimuthal asymmetry and orientation angle. A higher spin parameter strengthens the LV-induced effects on the bright ring properties. Increasing disk thickness reduces the ring diameter and enhances the LV parameter's effects on this diameter. The ring width shows no systematic dependence on the disk thickness. These quantities of the bright ring display similar trends against the black hole spin and the LV parameter for the rotating LV black hole. Using EHT observational data of Sgr A*, we find that, at fixed disk thickness, the parameter-space map illustrates that the bounded range of the LV parameter first broadens and then contracts with the growing black hole spin, and shifts toward smaller LV parameter values. In addition, the LV parameter narrows the bounded range of black hole spin: negative LV parameter values shift this range to a higher spin, while positive values shift it to a lower spin. Finally, we probe effects of the LV parameter on the peak position value and the width of the primary image and the $n=1$ photon ring for the rotating LV black hole. The peak positions and their widths nearly always decrease with the LV parameter. The peak position differences for various LV parameters are more pronounced for a purely Keplerian accretion flow. In addition, the primary image and the $n=1$ photon ring produced by purely radially free-falling flows are broader than their counterparts generated by purely Keplerian flows.
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Solar and Stellar Astrophysics

Cross-Calibration of Chandrayaan-2 XSM with INSPIRESat-1 DAXSS and GOES-16 XRS

N. P. S. Mithun, Santosh V. Vadawale, Asif M. Mandayapuram et al. (+9 more)

X-ray spectroscopic observations of the solar corona and flares provide crucial diagnostics of plasma properties and are essential for understanding the physical processes responsible for coronal heating and solar eruptive activity. The Chandrayaan-2 Solar X-ray Monitor (XSM) provides disk-integrated spectra of the Sun in the 1–15~keV soft X-ray band, enabling modeling of the thermal X-ray emission from the corona across quiet phases to intense solar flares. XSM has been operational for about seven years, starting from the last solar minimum and covering the maximum of the current Solar Cycle. The Dual-zone Aperture X-ray Solar Spectrometer (DAXSS) instrument on board INSPIRESat-1 covers the solar X-ray spectra in a similar energy range as XSM and was operational during 2022–2026. With multiple instruments simultaneously observing the Sun in X-rays, there is scope to compare measurements across instruments. Here, we present the cross-calibration of XSM with DAXSS and a broadband X-ray flux monitor, the GOES-16 X-ray Sensor (XRS). Comparisons of XSM and DAXSS spectra reveal an unaccounted attenuation in the XSM low-energy response. Supported by laboratory measurements, we attribute this difference to the effective detector beryllium window thickness being 25 microns rather than the previously assumed 8 microns. Incorporating this revision into the XSM calibration significantly improves the agreement between the two instruments, with flux measurements agreeing within ~10% in the 1–8 Angstrom band. Comparison with GOES-16 XRS measurements over a broad range of solar activity levels further demonstrates consistency, with a median flux difference of less than 10%.
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All authors N. P. S. Mithun, Santosh V. Vadawale, Asif M. Mandayapuram, M. Shanmugam, Soumya Kohli, Mehul R. Pandya, Anil Bhardwaj, Robert Sewell, Bennet Schwab, Amir Caspi, Thomas N. Woods, Janet L. Machol

High Energy Astrophysical Phenomena

Probing strange quark matter objects with future space-based gravitational wave detectors DECIGO and BBO

Abdusattar Kurban, Xia Zhou, Na Wang et al. (+9 more)

The Strange Quark Matter (SQM) hypothesis posits that objects composed of SQM could exist across a wide mass range, from strange planets (SPs) to strange stars (SSs). It has been proposed that gravitational waves (GWs) emitted by inspiraling SS-SP systems may be detectable by ground-based GW observatories such as advanced LIGO and the Einstein Telescope. Nevertheless, such a system may undergo an extended period of orbital evolution in a close configuration before entering the inspiraling phase. During this time, it can generate continuous GW signals at frequencies ranging from milli-hertz (mHz) to deci-hertz (dHz). The detailed characteristics of these GWs have not yet been thoroughly explored. In this study, we delve into the continuous GW features of SS-SP systems, with a focus on exploring the physically viable parameter space. We compared the GW signals emitted by these systems to the sensitivity curves of next-generation space-based GW detectors like the Deci-hertz Interferometer Gravitational wave Observatory (DECIGO) and the Big Bang Observer (BBO). Our analyses demonstrate that both the DECIGO and BBO detectors are capable of detecting continuous GWs from SS-SP systems across a broad parameter space. These GWs carry important information for testing the SQM hypothesis, as well as for advancing our understanding of supernovae and compact star merger processes.
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All authors Abdusattar Kurban, Xia Zhou, Na Wang, Yong-Feng Huang, Wenming Yan, Jianping Yuan, Ali Esamdin, Rai Yuen, Jin-Hong Chen, Xiao-Fei Dong, Zhigang Wen, Yu-Bin Wang

General Relativity and Quantum Cosmology

How does geometry shape quantum emission in rotating bumblebee gravity?

A. A. Araújo Filho

We compare propagation and static emission estimates in a rotating metric geometry and a stationary metric-affine bumblebee geometry. Their distinct constructions and spatial asymptotics are kept, and normalized Killing times define the physical frequencies and angular velocities. Direct invariant calculations identify the metric-affine outer root and open exterior axes as curvature singularities for generic rotation. The obstruction at bifurcation surface poles concerns the smoothness of the bumblebee field independently. Its mixed meridional component couples angular channels; finite transverse energy fixes the adopted axial condition and defines a self adjoint stationary operator on bounded exterior annuli. For the metric geometry, we construct normalized radiative scalar modes with specified Unruh data, evaluate the horizon frequency transformation, and include spontaneous superradiant emission through the radial scattering map. We prove positivity of the axisymmetric potential and compute numerical transmission factors and a partial scalar energy spectrum alongside an analytical lower bound. The static emission estimates use the stated Stefan-Boltzmann model.
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Instrumentation and Methods for Astrophysics

Design and modeling of an oblique incidence dichroic mirror for a high contrast imaging system

Joanna Rosenbluth, Ramya Anche, Kyle Van Gorkom et al. (+4 more)

The proposed Habitable Worlds Observatory (HWO) aims to detect and characterize Earth-like planets around Sun-like stars from the ultraviolet to the infrared using high-contrast imaging. A dichroic mirror is a natural choice for splitting light between multiple wavelength channels in such a system, but the coating must introduce minimal polarization aberrations and chromatic wavefront errors (WFE) to avoid limiting contrast. We present the design of a long-pass dichroic mirror operated at a $7^\circ$ angle of incidence that provides high reflection in the short-wavelength band, high transmission in the long-wavelength band, and a sharp cut-on near 550~nm. A multilayer thin-film design process was used to meet these spectral requirements while reducing polarization aberrations and chromatic WFE sensitivity. Reflected phase optimization was also incorporated to reduce sensitivity to manufacturing-induced layer-thickness variations, which can produce wavelength-dependent WFE and degrade coronagraph performance. The resulting coating-induced WFE was propagated through simulations of a vector vortex coronagraph to assess contrast performance. Simulations predict dark-hole contrast residuals at the $10^{-12}$ level, indicating that the optimized dichroic mirror does not limit coronagraph performance.
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All authors Joanna Rosenbluth, Ramya Anche, Kyle Van Gorkom, Nikoli Cooper, William Melby, Daewook Kim, Ewan Douglas

Instrumentation and Methods for Astrophysics

Towards optimal photometric calibration of digital astronomical plates with deep learning

Mingyang Ma, Haibo Yuan, Lin Yang et al. (+8 more)

Photometric calibration of digitized photographic plates is commonly modeled with separable magnitude-, color-, and position-dependent terms, but this separability can break down when image quality varies across the field in a magnitude-dependent way, leaving coupled spatial systematics in the residuals. We introduce a deep-learning calibration framework, the Multi-Feature Fused Network (MFF-Net), which takes instrumental magnitude, color, and pixel coordinates as input and learns a single nonlinear correction that jointly captures their coupled dependencies. Tests on 1{,}200 digitized Chinese plates show that MFF-Net consistently outperforms the MYX25 method (Ma et al. 2025), improving the 5th–95th percentile precision from 0.11–0.26~mag to 0.08–0.18~mag and delivering an approximately factor-of-two gain for bright sources. The learned correction largely removes the magnitude–position coupling seen in post-calibration residual maps, enabling higher-precision plate photometry and more reliable use of large historical plate archives.
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All authors Mingyang Ma, Haibo Yuan, Lin Yang, Kai Xiao, Bowen Huang, Shiyin Shen, Zhengjun Shang, Yong Yu, Meiting Yang, Zhenghong Tang, Jianhai Zhao

Plasma Physics

Sub-sonic compressible magnetohydrodynamic turbulence I. Alfvénic and fast-magnetosonic injection, amplitude dependence, and compressibility effects

Eleonora Puzzoni, Silvio Sergio Cerri, Dimitri Laveder et al. (+2 more)

We investigate how sub-sonic compressible magnetohydrodynamic (MHD) turbulence properties that are relevant for cosmic-ray (CR) transport in the Galaxy are affected by the nature and amplitude of initial fluctuations, and by the plasma compressibility $\beta$. We perform 3D simulations of decaying compressible ideal-MHD turbulence at $1024^3$ resolution with the PLUTO code. The level of density fluctuations in fully developed turbulence is insensitive to whether this state is reached starting from Alfvénic or fast-magnetosonic perturbations. Fast-magnetosonic injection is characterized by an early phase of rapid shock dissipation, followed by a turbulence-dominated decay with a rate comparable to that of the Alfvénic case. The contribution of fast-magnetosonic fluctuations in fully developed turbulence remains relevant only when the initial injection consists exclusively of fast modes. Large-amplitude turbulence ($\delta B/B_0>1$) is characterized by a nearly isotropic Kolmogorov or Iroshnikov-Kraichnan spectrum for Alfvénic or fast-magnetosonic injection, respectively. At low amplitudes ($\delta B/B_0\ll1$), both initial Alfvénic and mixed-wave perturbations lead to strongly anisotropic turbulence with spectra $\propto k_\perp^{-5/3}$ and $\propto k_z^{-2}$ (becoming steeper at $\beta\gg1$), whereas fast-magnetosonic perturbations produce a turbulent state populated by shocks with a nearly isotropic $k^{-2}$ spectrum. Magnetic-field curvature and mirror structures are strongly sensitive to fluctuation amplitude and plasma $\beta$. The predicted -2.5 power-law scaling emerges only in the large-amplitude regime at high $\beta$. This work highlights that features of sub-sonic compressible MHD turbulence that may affect CR transport are sensitive to large-scale conditions and to the plasma $\beta$. Their effect on CR diffusion and field-line random walk is the object of Paper II.
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All authors Eleonora Puzzoni, Silvio Sergio Cerri, Dimitri Laveder, Thierry Passot, Pierre-Louis Sulem

General Relativity and Quantum Cosmology

A geometrical-optics analogy for gravitational lensing using axicon-type lenses

Santiago Hernández-Díaz and Ángel S. Sanz

Gravitational lensing is often introduced through the bending of light by mass, but its geometrical nature can be difficult to visualize without invoking the full machinery of general relativity. We present a geometrical-optics analogy in which selected lensing-like image morphologies are generated by ray tracing through axicon-type lenses. In contrast with analogies based on a spatially varying refractive index, the present model uses optical elements with a constant refractive index; the redistribution of rays is produced by the geometry of the refracting surfaces. After deriving the ray-tracing equations for a general two-surface axicon, we apply the model to conical and exponential profiles. Axially symmetric configurations generate ring-like images, misaligned incidence produces partial arcs, and broken axial symmetry leads to four-image patterns reminiscent of an Einstein cross. The model is not intended as a physical substitute for a relativistic lens equation, but as a computational and pedagogical tool for exploring how surface geometry and symmetry control ray deflection, redistribution, and image multiplicity.
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High Energy Physics (Theory) · Cross-listed from math.RT

Residue construction of quantized Coulomb branches

Daniil Klyuev

We describe the image of a quantized BFN Coulomb branch $\mathcal{A}_{G,N}^{\hbar=1}$ under localization (abelianization) map for any $G,N$. In most cases, such as quiver gauge theories without loops, this description works for any flavors, sometimes we need to take generic or formal flavor parameters. The answer is given by a roots and residue condition similar to Ginzburg—Kapranov—Vasserot construction of DAHA arXiv:alg-geom/9512017. As a corollary, for any quantized conical Coulomb branch (and zero or small flavors) we provide a mathematical construction of the sphere trace introduced by Gaiotto and Okazaki arXiv:1911.11126.
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