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Full-polarization millimeter wavelength variability of Sagittarius A* during the 2018 EHT campaign

2026-05-12T00:30:59Z

Title: Full-polarization millimeter wavelength variability of Sagittarius A* during the 2018 EHT campaign Author(s): Albentosa-Ruiz, Ezequiel; Washington, Jasmin E.; Marchili, Nicola; Marti-Vidal, Ivan; Goddi, Ciriaco; Wielgus, Maciek; Mus, Alejandro; Ricarte, Angelo; Marrone, Daniel P.; Salas, Leon D. S.; Iwata, Yuhei; Carlos, Douglas F.; Tetarenko, Alexandra J.; Moriyama, Kotaro; Dhruv, Vedant; Akiyama, Kazunori; Alberdi, Antxon; Alef, Walter; Algaba, Juan Carlos; Anantua, Richard; Asada, Keiichi; Azulay, Rebecca; Bach, Uwe; Baczko, Anne-Kathrin; Ball, David; Balokovic, Mislav; Bandyopadhyay, Bidisha; Barrett, John; Baubock, Michi; Benson, Bradford A.; Bintley, Dan; Blackburn, Lindy; Blundell, Raymond; Bouman, Katherine L.; Bower, Geoffrey C.; Bremer, Michael; Brissenden, Roger; Britzen, Silke; Broderick, Avery E.; Broguiere, Dominique; Bronzwaer, Thomas; Bustamante, Sandra; Carlstrom, John E.; Chael, Andrew; Chan, Chi-kwan; Chang, Dominic O.; Chatterjee, Koushik; Chatterjee, Shami; Chen, Ming-Tang; Chen, Yongjun; Cheng, Xiaopeng; Christian, Pierre; Cho, Ilje; Conroy, Nicholas S.; Conway, John E.; Crawford, Thomas M.; Crew, Geoffrey B.; Cruz-Osorio, Alejandro; Cui, Yuzhu; Curd, Brandon; Dahale, Rohan; Davelaar, Jordy; De laurentis, Mariafelicia; Deane, Roger; Dempsey, Jessica; Desvignes, Gregory; Dexter, Jason; Dihingia, Indu K.; Doeleman, Sheperd S.; Dzib, Sergio A.; Eatough, Ralph P.; Emami, Razieh; Falcke, Heino; Farah, Joseph; Fish, Vincent L.; Fomalont, Edward; Ford, H. Alyson; Foschi, Marianna; Fuentes, Antonio; Fraga-Encinas, Raquel; Freeman, William T.; Friberg, Per; Fromm, Christian M.; Galison, Peter; Gammie, Charles F.; Garcia, Roberto; Gentaz, Olivier; Geertsema, Gertie; Georgiev, Boris; Gold, Roman; Gomez, Jose L.; Gomez-Ruiz, Arturo I.; Gu, Minfeng; Gurwell, Mark; Hada, Kazuhiro; Haggard, Daryl; Hesper, Ronald; Heumann, Dirk; Ho, Luis C.; Ho, Paul; Honma, Mareki; Huang, Chih-Wei L.; Huang, Lei; Hughes, David H.; Ikeda, Shiro; Impellizzeri, C. M. Violette; Inoue, Makoto; Issaoun, Sara; James, David J.; Jannuzi, Buell T.; Janssen, Michael; Jeter, Britton; Jiang, Wu; Jimenez-Rosales, Alejandra; Johnson, Michael D.; Jones, Adam C.; Jorstad, Svetlana; Joshi, Abhishek V.; Jung, Taehyun; Karuppusamy, Ramesh; Kawashima, Tomohisa; Keating, Garrett K.; Kettenis, Mark; Kim, Dong-Jin; Kim, Jae-Young; Kim, Jongsoo; Kim, Junhan; Kino, Motoki; Koay, Jun Yi; Kocherlakota, Prashant; Kofuji, Yutaro; Koch, Patrick M.; Koyama, Shoko; Kramer, Carsten; Kramer, Joana A.; Kramer, Michael; Krichbaum, Thomas P.; Kuo, Cheng-Yu; La Bella, Noemi; Lee, Sang-Sung; Levis, Aviad; Li, Zhiyuan; Lico, Rocco; Lindahl, Greg; Lindqvist, Michael; Lisakov, Mikhail; Liu, Jun; Liu, Kuo; Liuzzo, Elisabetta; Lo, Wen-Ping; Lobanov, Andrei P.; Loinard, Laurent; Lonsdale, Colin J.; Lowitz, Amy E.; Lu, Ru-Sen; MacDonald, Nicholas R.; Mao, Jirong; Marko, Sera; Marscher, Alan P.; Matsushita, Satoki; Matthews, Lynn D.; Medeiros, Lia; Menten, Karl M.; Mizuno, Izumi; Mizuno, Yosuke; Montgomery, Joshua; Moran, James M.; Moscibrodzka, Monika; Mulaudzi, Wanga; Mueller, Hendrik; Mueller, Cornelia; Musoke, Gibwa; Myserlis, Ioannis; Nagai, Hiroshi; Nagar, Neil M.; Nair, Dhanya G.; Nakamura, Masanori; Narayanan, Gopal; Natarajan, Iniyan; Nathanail, Antonios; Fuentes, Santiago Navarro; Neilsen, Joey; Ni, Chunchong; Nowak, Michael A.; Oh, Junghwan; Okino, Hiroki; Sanchez, Hector Raul Olivares; Oyama, Tomoaki; Ozel, Feryal; Palumbo, Daniel C. M.; Paraschos, Georgios Filippos; Park, Jongho; Parsons, Harriet; Patel, Nimesh; Pen, Ue-Li; Pesce, Dominic W.; Pietu, Vincent; PopStefanija, Aleksandar; Porth, Oliver; Prather, Ben; Principe, Giacomo; Psaltis, Dimitrios; Pu, Hung-Yi; Ramakrishnan, Venkatessh; Rao, Ramprasad; Rawlings, Mark G.; Rezzolla, Luciano; Ripperda, Bart; Roder, Jan; Roelofs, Freek; Romero-Canizales, Cristina; Ros, Eduardo; Roshanineshat, Arash; Rottmann, Helge; Roy, Alan L.; Ruiz, Ignacio; Ruszczyk, Chet; Rygl, Kazi L. J.; Sanchez, Salvador; Sanchez-Arguelles, David; Sanchez-Portal, Miguel; Sasada, Mahito; Satapathy, Kaushik; Saurabh; Savolainen, Tuomas; Schloerb, F. Peter; Schonfeld, Jonathan; Schuster, Karl-Friedrich; Shao, Lijing; Shen, Zhiqiang; Silpa, Sasikumar; Small, Des; Sohn, Bong Won; SooHoo, Jason; Souccar, Kamal; Stanway, Joshua S.; Sun, He; Tazaki, Fumie; Tiede, Paul; Tilanus, Remo P. J.; Titus, Michael; Toma, Kenji; Torne, Pablo; Toscano, Teresa; Traianou, Efthalia; Trent, Tyler; Trippe, Sascha; Turk, Matthew; van Bemmel, Ilse; van Langevelde, Huib Jan; van Rossum, Daniel R.; Vos, Jesse; Wagner, Jan; Ward-Thompson, Derek; Wardle, John; Weintroub, Jonathan; Wharton, Robert; Wiik, Kaj; Witzel, Gunther; Wondrak, Michael F.; Wong, George N.; Wu, Qingwen; Yadlapalli, Nitika; Yamaguchi, Paul; Yfantis, Aristomenis; Yoon, Doosoo; Young, Andre; Younsi, Ziri; Yu, Wei; Yuan, Feng; Yuan, Ye-Fei; Zeng, Ai-Ling; Zensus, J. Anton; Zhang, Shuo; Zhao, Guang-Yao; Zhao, Shan-Shan Abstract: Context. Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, provides a unique laboratory to study accretion dynamics and plasma processes near the event horizon. Aims. We investigated the variability and polarization properties of Sgr A* using ALMA observations during the 2018 Event Horizon Telescope campaign. Methods. We analyzed high-cadence full-polarization light curves from ALMA at millimeter wavelengths, performed time-series analysis, and investigated the temporal behavior during an X-ray flare observed by Chandra on 2018 April 24. The variability characteristics are compared with expectations from standard accretion flow models. Results. We find low variability in total intensity (sigma/mu < 10%), but significantly higher variability in linear and circular polarization ( similar to 30% and similar to 50%, respectively). A time-series analysis reveals red-noise variability, with power spectral densities between 2 and 3 across all Stokes parameters. Polarized intensity shows stable intra-day timescales, while total intensity exhibits more variable timescales, suggesting distinct emission regions, with polarization likely arising from a coherent structure. On April 24, a statistically significant inter-band delay in polarized intensity coincides with a near-simultaneous X-ray and millimeter peak that deviates from the typical delayed flare scenario. This event also features enhanced millimeter variability and coherent polarization loop evolution. The observed simultaneity challenges standard models of transient synchrotron emission with cooling delays, favoring instead a scenario of continuous energy injection in an optically thin region. Conclusions. Our results offer new constraints on the physical mechanisms driving variability in Sgr A*, and provide key observational input for refining theoretical models of accretion and plasma behavior in the vicinity of supermassive black holes.

Epitaxial n-ZnO/MoS2/p-GaN Heterostructure Light-Emitting Diodes

2026-05-06T05:30:18Z

Title: Epitaxial n-ZnO/MoS2/p-GaN Heterostructure Light-Emitting Diodes Author(s): Rahmatulloh, Imasda; Dalayoan, Daryll J. C.; Ali, Asad; Shin, Soobeom; Nguyen, Anh T. D.; Kwon, Taenam; Behera, Satyabrat; Lee, Jaehyun; Kim, Heekyeong; Jeong, Hu Young; Namgung, Seon; Yi, Gyu-Chul; Chung, Kunook Abstract: We investigated an epitaxial strategy for fabricating MoS2 light-emitting diodes (LEDs). A full-coverage MoS2 active layer was grown on p-type GaN, and n-type ZnO nanorods were then vertically aligned on the MoS2 to form a p-n junction with negligible damage to the MoS2. All materials have nearly matched hexagonal structures, enabling single-crystal alignment. Although the continuous MoS2 film formed multiple layers (MLs), the ZnO/MoS2/GaN heterostructure yielded favorable optical characteristics of the ML-MoS2, including internal quantum efficiency comparable to that of the single-layer MoS2. The ZnO/MoS2/GaN LED exhibited stable A and B exciton emissions, which imply direct bandgap transition with spin-orbit coupling. Without mechanically exfoliated or transferred 2D films, this epitaxial approach satisfies the key requirements for fabricating 2D-based optoelectronic and quantum light sources. The strength of epitaxy, such as large-scale scalability and multiple quantum-well formation, will further advance 2D optoelectronics, making them more practical and efficient.

Current-Driven Symmetry Breaking and Spin−Orbit Polarization in Chiral Wires

2026-05-11T01:00:11Z

Title: Current-Driven Symmetry Breaking and Spin−Orbit Polarization in Chiral Wires Author(s): Jeong, Uiseok; Hill, Daniel; Sisakht, Esmaeil Taghizadeh; Yan, Binghai; Rubio, Angel; Ullrich, Carsten A.; Park, Noejung Abstract: The spin dynamics of electrons in chiral molecular systems remains a topic of intense interest, particularly regarding whether geometric chirality inherently induces spin polarization in current-carrying electrons. In this work, we employ ab initio real-time time-dependent density functional theory (rt-TDDFT) to directly simulate the interplay among charge current, spin, and orbital. This real-time tracking extends beyond perturbative treatments, and we analyze how nonequilibrium currents effectively lift the symmetry constraints of screw rotation and time-reversal symmetry. We find that the emergence of spin and orbital angular momenta is dynamically correlated with a concomitant loss of translational (linear) momentum, which we interpret as an intrinsic consequence of current-driven symmetry lowering. The implications of this mechanism for chirality-induced spin selectivity and spintronics device design are discussed.

Identification of low-energy kaons in the ProtoDUNE-SP detector

2026-04-29T00:00:02Z

Title: Identification of low-energy kaons in the ProtoDUNE-SP detector Author(s): Abbaslu, S.; Chung, Moses; DUNE Collaboration Abstract: The Deep Underground Neutrino Experiment (DUNE) is a next-generation neutrino experiment with a rich physics program that includes searches for the hypothetical phenomenon of proton decay. Utilizing liquid-argon time-projection chamber technology, DUNE is expected to achieve world-leading sensitivity in the proton decay channels that involve charged kaons in their final states. The first DUNE demonstrator, ProtoDUNE Single-Phase, was a 0.77 kt detector that operated from 2018 to 2020 at the CERN Neutrino Platform, exposed to a mixed hadron and electron test-beam with momenta ranging from 0.3 to 7 GeV/c. We present a selection of low-energy kaons among the secondary particles produced in hadronic reactions, using data from the 6 and 7 GeV/c beam runs. The selection efficiency is 1% and the sample purity 92%. The initial energies of the selected kaon candidates encompass the expected energy range of kaons originating from proton decay events in DUNE (below ∼200 MeV). In addition, we demonstrate the capability of this detector technology to discriminate between kaons and other particles such as protons and muons, and provide a comprehensive description of their energy loss in liquid argon, which shows good agreement with the simulation. These results pave the way for future proton decay searches at DUNE.