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Scanning protocol influence on relative electron Density-CT number calibrations and radiotherapy dose calculation for a Halcyon Linac

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Radiation physics and Chemistry 2025年

作者： Thanh Tai, Duong Nhu Tuyen, Pham Duc Tuan, Hoang Hung, Hoang T.P. Kandemir, Recep Omer, Hiba Sulieman, Abdelmoneim Bradley, David Chow, James C.L. Department of Medical Physics Faculty of Medicine Nguyen Tat Thanh University 298-300A Nguyen Tat Thanh Street Ward 13 District 4 Ho Chi Minh City Viet Nam Department of Radiation Oncology University Medical Shing Mark Hospital Dong Nai 810000 Viet Nam Danang Irradiation Facility Research and Development Center for Radiation Technology VINATOM 550000 Da Nang Viet Nam Dokuz Eylül University Institute of Health Sciences Department of Medical Physics Izmir Turkey Dokuz Eylül University Vocational School of Health Services The Program of Radiotherapy Izmir Turkey Department of Radiological Sciences College of Applied Medical Sciences Imam Abdulrahman Bin Faisal University P. O. Box 1982 Dammam34212 Saudi Arabia Department of Radiological Sciences College of Applied Medical Sciences King Saud Bin Abdulaziz University for Health Sciences Al Ahsa Saudi Arabia Imaging Physics Section Research and Innovation Department King Faisal Specialist Hospital & Research Center Riyadh Saudi Arabia Applied Radiation Physics and Technologies Group Sunway University 46150 PJ Malaysia School of Mathematics and Physics University of Surrey GuildfordGU2 7XH United Kingdom Department of Radiation Oncology University of Toronto TorontoONN5T 1P5 Canada Radiation Medicine Program Princess Margaret Cancer Centre University Health Network ONM5G 1X6 Canada

Tissue Relative Electron Density (RED), typically determined via computation of CT-based Hounsfield unit (HU) values, has an accuracy which is affected by the choice of CT scanning parameters. The influence of these on the RED-CT number calibration curves is of importance, not least concerning variations in CT x-ray tube voltage and current. The purpose of this study was to examine the effect of variations in CT x-ray tube voltage and current on the calibration curves of RED - CT number conversion, with the aim of improving the accuracy of dose calculation in radiotherapy treatment planning. An electron density phantom CIRS have been conducted at 200 mAs, for tube voltages of 80, 110, and 130 kVp, corresponding images being calibrated in terms of RED-CT number conversion curves. Subsequent treatment plans have been generated, identified in terms of the applied tube voltages, the 130 kVp plan being designated the reference plan. The remaining plans have been compared to the reference plan via analysis of isodose distribution and dose. The influence of tube voltage were being found to be greatest for high-density substances such as bone in comparison to low-density materials. Conversely, the CT number of a titanium rod has been consistent, regardless of the choice of tube voltage or current. The effect of tube current variation on the calibration curves has been minor at higher tube voltages but more pronounced using lower voltages and current. The presence in the phantom of plugs of high-density materials has resulted in beam hardening artefacts, impacting on the RED values for other plugs. In achieving accurate dose calculation for radiotherapy treatment plans the work underscores the need to account for effects of CT scanning parameters on the RED-CT number conversion curves. Further emphasized is the importance of careful selection of imaging protocols in seeking to minimize beam hardening artefacts and to ensure accurate determination of RED. The study demonstrat

关键词： X ray tubes

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Amplification without inversion:mUnderstanding probability amplitudes, quantum interference, and Feynman rules in a strongly driven system

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Physical Review A 1997年第5期55卷 3900-3900页

作者： J. L. Cohen P. R. Berman 1Applied Physics Program Department of Physics University of Michigan Ann Arbor Michigan 48109-1120 2Department of Physics University of Michigan Ann Arbor Michigan 48109-1120

Density-matrix calculations provide the steady-state conditions for probe amplification or lasing between atomic levels with an uninverted population, but additional insight into the underlying physics is given by a probability amplitude approach. In this paper we derive the gain coefficient from the Feynman diagrams for a probe-laser incident on a resonantly pumped, V-type system using time-dependent perturbation theory in a dressed basis. The connection is made to density-matrix calculations for this model, which have been used recently to describe experiments in Rb [A. S. Zibrov et al., Laser Phys. 5, 553 (1995); Phys. Rev. Lett. 75, 1499 (1995)]. In the density-matrix calculation the overall gain is possible because the pump-induced coherence of a strongly driven transition leads to probe amplification, despite the lack of inversion on the probe transition. In our amplitude approach we associate a specific physical process with each of the scattering channels for the probe and show how amplification without inversion can be achieved. The amplitude calculation reveals a distinction between stepwise and two-quantum processes. Interference is shown to result from the two-quantum processes, constructive for the amplification channels and destructive for the absorption. Terms appearing in the gain coefficient are traced to different sources in the amplitude and density-matrix approaches. The physical origin of each term is discussed and compared for both approaches. Terms that arise from coherences in the density-matrix approach are shown to correspond to noninterfering stepwise contributions in the amplitude approach. In deriving these results, we find that the Feynman rules that we construct for forming the probability amplitude for an arbitrary scattering process of the electromagnetic field from the coupled atom-strong pump system are consistent with Rayleigh-Schrödinger perturbation theory in the quantum dressed basis. In addition, the spontaneously emitted phot

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Tracking X-Ray Variability in Next-generation EHT Low-luminosity Active Galactic Nucleus Targets

arXiv

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arXiv 2025年

作者： Ford, Nicole M. Nowak, Michael Ramakrishnan, Venkatessh Haggard, Daryl Dage, Kristen Nair, Dhanya G. Chan, Chi-Kwan Department of Physics McGill University 3600 Rue University MontrealQCH3A 2T8 Canada Trottier Space Institute 3550 Rue University MontréalQCH3A 2A7 Canada Department of Physics Washington University in Saint Louis MSC 1105-109-02 One Brookings Drive St. LouisMO63130-4899 United States Finnish Centre for Astronomy with ESO University of Turku TurkuFI-20014 Finland Aalto University Metsähovi Radio Observatory Metsähovintie 114 KylmäläFI-02540 Finland International Centre for Radio Astronomy Research Curtin University GPO Box U1987 PerthWA6845 Australia Astronomy Department Universidad de Concepción Casilla Concepción160-C Chile Max Planck Institute for Radio Astronomy Auf dem Hügel 69 Bonn53121 Germany Steward Observatory Department of Astronomy University of Arizona 933 N. Cherry Avenue TucsonAZ85721 United States Data Science Institute University of Arizona 1230 N. Cherry Avenue TucsonAZ85721 United States Program in Applied Mathematics University of Arizona 617 N. Santa Rita TucsonAZ85721 United States

We present a 5 month NICER X-ray monitoring campaign for two low-luminosity active galactic nuclei (LLAGNs)—NGC 4594 and IC 1459—with complementary Swift and NuSTAR observations. Utilizing an absorbed power-law and thermal source model combined with NICER’s SCORPEON background model, we demonstrate the effectiveness of joint source–background modeling for constraining emission from faint, background-dominated targets. Both sources are dominated by nuclear power-law emission with photon indices Γ ∼ 1.5–2, with NGC 4594 being slightly harder than IC 1459. The thermal contribution in both sources is fainter, but constant, with kT ∼ 0.5 keV (∼5 × 106 K). The power-law flux and Γ are strongly anticorrelated in both sources, as has been seen for other LLAGNs with radiatively inefficient accretion flows. NGC 4594 is the brighter source and exhibits significant aperiodic variability. Its variability timescale with an upper limit of 5–7 days indicates emission originating from ≾100 rg, at the scale of the inner accretion flow. A spectral break found at ∼6 keV, while tentative, could arise from synchrotron/inverse Compton emission. This high-cadence LLAGN X-ray monitoring campaign underlines the importance of multiwavelength variability studies for a sample of LLAGNs to truly understand their accretion and outflow physics. © 2025, CC BY.

关键词： Active Galactic Nuclei

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Resting Energy Expenditure in a Controlled Group of Young Arab Females: Correlations with Body Composition and Agreement with Prediction Equations

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Food and Nutrition Sciences 2013年第4期4卷 385-391页

作者： Abdelmonem Hassan Aalaa Mahdi Lara Hamade Abdelhamid Kerkadi Adel Yousif Department of Mathematics Statistics and Physics Qatar University Doha Qatar Human Nutrition Program Department of Health Sciences Qatar University Doha Qatar Human Nutrition Program Department of Health Sciences Qatar University Doha Qatar 2Department of Mathematics Statistics and Physics Qatar University Doha Qatar

Objectives: To assess correlates of body compositions measures and resting energy expenditure (REE) in young Arab females, and to compare measured REE values with values calculated from REE predictive equations. Methods: Seventy nine healthy women, aged 18 - 30 years, were recruited for the study. All volunteers fasted for 8 hours, abstained from vigorous physical activity, smoking and caffeinated beverages for twelve hours before measuring body composition and REE. Resting energy expenditure was measured by indirect calorimetry and body composition was measured by a bioelectrical impedance analysis. Results: Measured-REE was significantly correlated with body fat mass, fat free mass, skeletal muscle mass, and soft lean mass (R2 ranges 0.498 - 0.592;p p ?101.9 kcal, p p > 0.05). Mean measured REE varied significantly with BMI (p Conclusion: All body composition measures were significantly correlated with REE measured. Mifflin-St. Jeor equation showed the closest estimate to the measured REE in predicting REE of participants who had a normal weight or were overweight. Harris-Benedict equation significantly overestimated REE and Owen significantly underestimated REE.

关键词： Resting Energy Expenditure Indirect Calorimetry Body Composition Young Arab Women

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Reduced modeling of transitional exact coherent states in shear flow 15

Reduced modeling of transitional exact coherent states in sh...

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15th European Turbulence Conference, ETC 2015

作者： Beaume, Cédric Chini, Greg P. Julien, Keith Knobloch, Edgar Department of Aeronautics Imperial College London LondonSW7 2AZ United Kingdom Department of Mechanical Engineering and Program in Integrated Applied Mathematics University of New Hampshire DurhamNH03824 United States Department of Applied Mathematics University of Colorado at Boulder BoulderCO80309 United States Department of Physics University of California BerkeleyCA94720 United States

In parallel shear flows, the lower branch solution follows simple streamwise dynamics. A decomposition of this solution into Fourier modes in this direction yields modes whose amplitudes scale with inverse powers of the Reynolds number. We use this scaling to derive a reduced model for exact coherent structures in general parallel shear flows. The reduced model is regularized by retaining higher order viscous terms. Both lower branch and upper branch solutions are captured and studied. © TU Delft.

关键词： Shear flow

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An optical experiment towards the analogic simulation of the betatronic motion

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AIP Conference Proceedings 2001年第1期581卷 211-220页

作者： A. Bazzani P. Freguglia L. Fronzoni G. Turchetti 1Department of Physics University of Bologna and INFN Sezione di Bologna 2Department of Pure and Applied Mathematics University of L’Aquila and Domus Galilaeana (Pisa) 3Department of Physics University of Pisa INFM and CISSC of the University of Pisa

We present the first experiment results of an experiment that simulates the betatronic motion in a FODO cell by using an optical device. The analogy between the hamiltonian mechanics and the geometric optics is discussed in order to define a project of an optical FODO cell. We consider also the possibility of representing an optical path by means of a sequence of quaternion numbers. The experimental results are compared with the simulations of a ray tracing program.

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Supercoiling bacterial filaments

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AIP Conference Proceedings 1999年第1期487卷 271-278页

作者： Thomas R. Powers Raymond E. Goldstein Chris H. Wiggins 1Division of Engineering and Applied Sciences Harvard University Cambridge Massachusetts 02138 2Department of Physics and Program in Applied Mathematics University of Arizona Tucson Arizona 85712 3Courant Institute of Mathematical Sciences New York University New York New York 10012

Cells of mutant strains of the bacterium B. subtilis fail to separate upon dividing, and form long fibers. A given fiber is initially straight, but once it grows to around 100 microns, it buckles and writhes. Soon after this initial instability the fiber rapidly braids up into a plectoneme. Modeling a fiber as a twisted elastic filament in a viscous fluid, we exploit the “natural” frame of space curves to formulate the dynamics of the filament’s shape and twist density. The resulting coupled nonlinear equations are used to display a remarkable nonlinear phenomenon: geometric untwisting of open filaments, in which twist strain relaxes through a transient writhing instability without axial rotation. Experimentally observed motions of the fibers of B. subtilis may be examples of this twisting process.

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Multiplicity-dependent jet modification from di-hadron correlations in pp collisions at = 13 TeV

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Journal of High Energy physics 2025年第3期2025卷 1-32页

作者： Acharya, S. Agarwal, A. Aglieri Rinella, G. Aglietta, L. Agnello, M. Agrawal, N. Ahammed, Z. Ahmad, S. Ahn, S. U. Ahuja, I. Akindinov, A. Akishina, V. Al-Turany, M. Aleksandrov, D. Alessandro, B. Alfanda, H. M. Alfaro Molina, R. Ali, B. Alici, A. Alizadehvandchali, N. Alkin, A. Alme, J. Alocco, G. Alt, T. Altamura, A. R. Altsybeev, I. Alvarado, J. R. Alvarez, C. O. R. Anaam, M. N. Andrei, C. Andreou, N. Andronic, A. Andronov, E. Anguelov, V. Antinori, F. Antonioli, P. Apadula, N. Aphecetche, L. Appelshäuser, H. Arata, C. Arcelli, S. Arnaldi, R. Arneiro, J. G. M. C. A. Arsene, I. C. Arslandok, M. Augustinus, A. Averbeck, R. Averyanov, D. Azmi, M. D. Baba, H. Badalà, A. Bae, J. Baek, Y. W. Bai, X. Bailhache, R. Bailung, Y. Bala, R. Balbino, A. Baldisseri, A. Balis, B. Banoo, Z. Barbasova, V. Barile, F. Barioglio, L. Barlou, M. Barman, B. Barnaföldi, G. G. Barnby, L. S. Barreau, E. Barret, V. Barreto, L. Bartels, C. Barth, K. Bartsch, E. Bastid, N. Basu, S. Batigne, G. Battistini, D. Batyunya, B. Bauri, D. Bazo Alba, J. L. Bearden, I. G. Beattie, C. Becht, P. Behera, D. Belikov, I. Bell Hechavarria, A. D. C. Bellini, F. Bellwied, R. Belokurova, S. Beltran, L. G. E. Beltran, Y. A. V. Bencedi, G. Bensaoula, A. Beole, S. Berdnikov, Y. Berdnikova, A. Bergmann, L. Besoiu, M. G. Betev, L. Bhaduri, P. P. Bhasin, A. Bhattacharjee, B. Bianchi, L. Bielčík, J. Bielčíková, J. Bigot, A. P. Bilandzic, A. Biro, G. Biswas, S. Bize, N. Blair, J. T. Blau, D. Blidaru, M. B. Bluhme, N. Blume, C. Boca, G. Bock, F. Bodova, T. Bok, J. Boldizsár, L. Bombara, M. Bond, P. M. Bonomi, G. Borel, H. Borissov, A. Borquez Carcamo, A. G. Botta, E. Bouziani, Y. E. M. Bratrud, L. Braun-Munzinger, P. Bregant, M. Broz, M. Bruno, G. E. Buchakchiev, V. D. Buckland, M. D. Budnikov, D. Buesching, H. Bufalino, S. Buhler, P. Burmasov, N. Buthelezi, Z. Bylinkin, A. Bysiak, S. A. Cabanillas Noris, J. C. Cabrera, M. F. T. Cai, M. Caines, H. Caliva, A. Calvo Villar, E. Camacho, J. M. M. Camerini, P. Canedo, F. D. M. Cantway, S. L. Carabas, M. Carballo, A. A. Car Université Clermont Auvergne CNRS/IN2P3 LPC Clermont-Ferrand France Variable Energy Cyclotron Centre Homi Bhabha National Institute Kolkata India European Organization for Nuclear Research (CERN) Geneva Switzerland Dipartimento di Fisica dell’Università and Sezione INFN Turin Italy Dipartimento DISAT del Politecnico and Sezione INFN Turin Italy Dipartimento di Fisica e Astronomia dell’Università and Sezione INFN Bologna Italy Department of Physics Aligarh Muslim University Aligarh India Korea Institute of Science and Technology Information Daejeon Republic of Korea Faculty of Science P.J. Šafárik University Košice Slovak Republic Frankfurt Institute for Advanced Studies Johann Wolfgang Goethe-Universität Frankfurt Frankfurt Germany Research Division and ExtreMe Matter Institute EMMI GSI Helmholtzzentrum für Schwerionenforschung GmbH Darmstadt Germany INFN Sezione di Torino Turin Italy Central China Normal University Wuhan China Instituto de Física Universidad Nacional Autónoma de México Mexico City Mexico University of Houston Houston United States Sungkyunkwan University Suwon City Republic of Korea Department of Physics and Technology University of Bergen Bergen Norway INFN Sezione di Cagliari Cagliari Italy Institut für Kernphysik Johann Wolfgang Goethe-Universität Frankfurt Frankfurt Germany INFN Sezione di Bari Bari Italy Physik Department Technische Universität München Munich Germany High Energy Physics Group Universidad Autónoma de Puebla Puebla Mexico Horia Hulubei National Institute of Physics and Nuclear Engineering Bucharest Romania University of Derby Derby United Kingdom Universität Münster Institut für Kernphysik Münster Germany Physikalisches Institut Ruprecht-Karls-Universität Heidelberg Heidelberg Germany INFN Sezione di Padova Padova Italy INFN Sezione di Bologna Bologna Italy Lawrence Berkeley National Laboratory Berkeley United States SUBATECH IMT Atlantique Nantes Université CNRS-IN2P3 Nantes France Laboratoire

Short-range correlations between charged particles are studied via two-particle angular correlations in pp collisions at $$ \sqrt{s} $$ = 13 TeV. The correlation functions are measured as a function of the relative azimuthal angle ∆φ and the pseudorapidity separation ∆η for pairs of primary charged particles within the pseudorapidity interval |η| < 0.9 and the transverse-momentum range 1 < pT < 8 GeV/c. Near-side (|∆φ| < 1.3) peak widths are extracted from a generalised Gaussian fitted over the correlations in full pseudorapidity separation (|∆η| < 1.8), while the per-trigger associated near-side yields are extracted for the short-range correlations (|∆η| < 1.3). Both are evaluated as a function of charged-particle multiplicity obtained by two different event activity estimators. The width of the near-side peak decreases with increasing multiplicity, and this trend is reproduced qualitatively by the Monte Carlo event generators PYTHIA 8, AMPT, and EPOS. However, the models overestimate the width in the low transverse-momentum region (pT < 3 GeV/c). The per-trigger associated near-side yield increases with increasing multiplicity. Although this trend is also captured qualitatively by the considered event generators, the yield is mostly overestimated by the models in the considered kinematic range. The measurement of the shape and yield of the short-range correlation peak can help us understand the interplay between jet fragmentation and event activity, quantify the narrowing trend of the near-side peak as a function of transverse momentum and multiplicity selections in pp collisions, and search for final-state jet modification in small collision systems.

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Roadmap on Nonlocality in Photonic Materials and Metamaterials

arXiv

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arXiv 2025年

作者： Monticone, Francesco Mortensen, N. Asger Fernández-Domínguez, Antonio I. Luo, Yu Tserkezis, Christos Khurgin, Jacob B. Shahbazyan, Tigran V. Chaves, André J. Peres, Nuno M.R. Wegner, Gino Busch, Kurt Hu, Huatian della Sala, Fabio Zhang, Pu Ciracì, Cristian Aizpurua, Javier Babaze, Antton Borisov, Andrei G. Chen, Xue-Wen Christensen, Thomas Yan, Wei Yang, Yi Hohenester, Ulrich Huber, Lorenz Wubs, Martijn de Liberato, Simone Gonçalves, P.A.D. de Abajo, F. Javier García Hess, Ortwin Tarasenko, Illya Cox, Joel D. Jelver, Line Dias, Eduardo J.C. Sánchez, Miguel Sánchez Margetis, Dionisios Gómez-Santos, Guillermo Stauber, Tobias Tretyakov, Sergei Simovski, Constantin Pakniyat, Samaneh Gómez-Díaz, J. Sebastián Bondarev, Igor V. Biehs, Svend-Age Boltasseva, Alexandra Shalaev, Vladimir M. Krasavin, Alexey V. Zayats, Anatoly V. Alù, Andrea Song, Jung-Hwan Brongersma, Mark L. Levy, Uriel Long, Olivia Y. Guo, Cheng Fan, Shanhui Bozhevolnyi, Sergey I. Overvig, Adam Prudêncio, Filipa R. Silveirinha, Mário G. Gangaraj, S. Ali Hassani Argyropoulos, Christos Huidobro, Paloma A. Galiffi, Emanuele Yang, Fan Pendry, John B. Miller, David A.B. School of Electrical and Computer Engineering Cornell University IthacaNY14853 United States POLIMA Center for Polariton-driven Light–Matter Interactions University of Southern Denmark Campusvej 55 Odense MDK-5230 Denmark D-IAS—Danish Institute for Advanced Study University of Southern Denmark Campusvej 55 Odense MDK-5230 Denmark Departamento de Física Teórica de la Materia Condensada Universidad Autónoma de Madrid MadridE-28049 Spain Universidad Autónoma de Madrid MadridE-28049 Spain School of Electrical and Electronic Engineering Nanyang Technological University Singapore639798 Singapore Key Laboratory of Radar Imaging and Microwave Photonics Ministry of Education College of Electronic and Information Engineering Nanjing University of Aeronautics and Astronautics Nanjing211106 China Department of Electrical and Computer Engineering Johns Hopkins University BaltimoreMD21218 United States Department of Physics Jackson State University JacksonMS39217 United States Department of Physics Aeronautics Institute of Technology SP So Jos dos Campos12228-900 Brazil Departamento de Física Universidade do Minho BragaP-4710-057 Portugal Av Mestre José Veiga Braga4715-330 Portugal Max-Born-Institut Berlin12489 Germany Humboldt-Universität zu Berlin Institut für Physik AG Theoretische Optik and Photonik Berlin12489 Germany Center for Biomolecular Nanotechnologies Istituto Italiano di Tecnologia Via Barsanti 14 Arnesano73010 Italy Via Monteroni Campus Unisalento Lecce73100 Italy School of physics Huazhong University of Science and Technology Luoyu Road 1037 Wuhan430074 China Donostia International Physics Center DIPC Donostia-San Sebastián20018 Spain Ikerbasque Basque Foundation for Science Bilbao48009 Spain Department of Electricity and Electronics University of the Basque Country Leioa48940 Spain Department of Applied Physics University of the Basque Country Donostia20018 Spain Université Paris-Saclay CNRS Institut des Scienc

Photonic technologies continue to drive the quest for new optical materials with unprecedented responses. A major frontier in this field is the exploration of nonlocal (spatially dispersive) materials, going beyond the local, wavevector-independent assumption traditionally made in optical material modeling. On one end, the growing interest in plasmonic, polaritonic and quantum materials has revealed naturally occurring nonlocalities, emphasizing the need for more accurate models to predict and design their optical responses. This has major implications also for topological, nonreciprocal, and time-varying systems based on these material platforms. Beyond natural materials, artificially structured materials—metamaterials and metasurfaces–can provide even stronger and engineered nonlocal effects, emerging from long-range interactions or multipolar effects. This is a rapidly expanding area in the field of photonic metamaterials, with open frontiers yet to be explored. In the case of metasurfaces, in particular, nonlocality engineering has become a powerful tool for designing strongly wavevector-dependent responses, enabling enhanced wavefront control, spatial compression, multifunctional devices, and wave-based computing. Furthermore, nonlocality and related concepts play a critical role in defining the ultimate limits of what is possible in optics, photonics, and wave physics. This Roadmap aims to survey the most exciting developments in nonlocal photonic materials, highlight new opportunities and open challenges, and chart new pathways that will drive this emerging field forward–toward new scientific discoveries and technological advancements. Copyright © 2025, The Authors. All rights reserved.

关键词： Nanocrystals

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Mahakala: A Python-based Modular Ray-tracing and Radiative Transfer Algorithm for Curved Spacetimes

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Astrophysical Journal 2025年第1期985卷 40-40页

作者： Sharma, Aniket Medeiros, Lia Wong, George N. Chan, Chi-Kwan Halevi, Goni Mullen, Patrick D. Stone, James M. Indian Institute of Science Education and Research Mohali. Sector 81 SAS Nagar PO Manauli Punjab Mohali 140306 India Center for Gravitation Cosmology and Astrophysics Department of Physics University of Wisconsin-Milwaukee P.O. Box 413 Milwaukee 53201 WI United States Department of Astrophysical Sciences Peyton Hall Princeton University Princeton 08544 NJ United States School of Natural Sciences Institute for Advanced Study 1 Einstein Drive Princeton 08540 NJ United States Princeton Gravity Initiative Princeton University Princeton 08544 NJ United States Steward Observatory Department of Astronomy University of Arizona 933 N. Cherry Avenue Tucson 85721 AZ United States Data Science Institute University of Arizona 1230 N. Cherry Avenue Tucson 85721 AZ United States Program in Applied Mathematics University of Arizona 617 N. Santa Rita Tucson 85721 AZ United States Department of Physics Illinois Institute of Technology Chicago 60616 IL United States Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) Northwestern University Evanston 60201 IL United States CCS-2 Los Alamos National Laboratory Los Alamos NM United States Center for Theoretical Astrophysics Los Alamos National Laboratory Los Alamos NM United States

We introduce Mahakala, a Python-based, modular, radiative ray-tracing code for curved spacetimes. We employ Google’s JAX framework for accelerated automatic differentiation, which can efficiently compute Christoffel symbols directly from the metric, allowing the user to easily and quickly simulate photon trajectories through non-Kerr spacetimes. JAX also enables Mahakala to run in parallel on both CPUs and GPUs. Mahakala natively uses the Cartesian Kerr-Schild coordinate system, which avoids numerical issues caused by the pole in spherical coordinate systems. We demonstrate Mahakala’s capabilities by simulating 1.3 mm wavelength images (the wavelength of Event Horizon Telescope observations) of general relativistic magnetohydrodynamic simulations of low-accretion rate supermassive black holes. The modular nature of Mahakala allows us to quantitatively explore how different regions of the flow influence different image features. We show that most of the emission seen in 1.3 mm images originates close to the black hole and peaks near the photon orbit. We also quantify the relative contribution of the disk, forward jet, and counterjet to 1.3 mm images. © 2025. The Author(s). Published by the American Astronomical Society.

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