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Abstract: We use the surface detector of the Pierre Auger Observatory to search for air showers initiated by photons with an energy above 10[sup]19 eV. Photons in the zenith angle range from 30 deg. to 60 deg. can be identified in the overwhelming background of showers initiated by charged cosmic rays through the broader time structure of the signals induced in the water-Cherenkov detectors of the array and the steeper lateral distribution of shower particles reaching ground. Applying the search method to data collected between January 2004 and June 2020, upper limits at 95% CL are set to an E[sup]-2 diffuse flux of ultra-high energy photons above 10[sup]19 eV, 2 × 10[sup]19 eV and 4 × 10[sup]19 eV amounting to 2.11 × 10[sup]-3, 3.12 × 10[sup]-4 and 1.72 × 10[sup]-4 km-2 sr-1 yr-1, respectively. While the sensitivity of the present search around 2 × 10[sup]19 eV approaches expectations of cosmogenic photon fluxes in the case of a pure-proton composition, it is one order of magnitude above those from more realistic mixed-composition models. The inferred limits have also implications for the search of super-heavy dark matter that are discussed and illustrated.
Keywords: ultra-high-energy cosmic rays, UHE photons, Pierre Auger Observatory, extensive air showers, water Cherenkov detectors
Published in RUNG: 18.08.2023; Views: 790; Downloads: 8
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Keywords: visokoenergijski fotoni, gravitacijski valovi, observatorij P. Auger
Published in RUNG: 21.07.2023; Views: 862; Downloads: 4
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Abstract: Strojno učenje in umetna inteligenca (UI) v računalništvu nista nova pojava, je pa zlasti UI v lanskem letu prestopila s področja stroke v najširše družbeno dogajanje in kaže, da bo imela na celotno družbo še nesluten, a zagotovo izjemno močan vpliv. Sklop tehnoloških in hkrati družbenih vprašanj in vizij zadeva tudi polje umetnosti. Delo Vuka Ćosića Nacija – Kultura kot enega svojih ključnih elementov uporablja UI. Kako je zastavljena, kako deluje, kako je sposobna iz kratkega tvita razviti sonetu podobno besedilo? Delovanje UI v okviru umetniškega dela je predstavil njen programer, Marko Plahuta. 12. januar 2023, Muzej sodobne umetnosti Metelkova, Ljubljana, Slovenija. Jezik: slovensko. Trajanje: 108' 51". Posnetek predstavitve z vprašanji in odgovori. Kamera in Montaža: Urša Rahne. Avtorske pravice za video: BY-NC-SA.
Keywords: novomedijska umetnost, umetna inteligenca, MSUM
Published in RUNG: 13.07.2023; Views: 1204; Downloads: 11
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Abstract: A deep survey of the Large Magellanic Cloud at ∼ 0.1−100 TeV photon energies with the Cherenkov Telescope Array is planned. We assess the detection prospects based on a model for the emission of the galaxy, comprising the four known TeV emitters, mock populations of sources, and interstellar emission on galactic scales. We also assess the detectability of 30 Doradus and SN 1987A, and the constraints that can be derived on the nature of dark matter. The survey will allow for fine spectral studies of N 157B, N 132D, LMC P3, and 30 Doradus C, and half a dozen other sources should be revealed, mainly pulsar-powered objects. The remnant from SN 1987A could be detected if it produces cosmic-ray nuclei with a flat power-law spectrum at high energies, or with a steeper index 2.3−2.4 pending a flux increase by a factor > 3−4 over ∼ 2015−2035. Large-scale interstellar emission remains mostly out of reach of the survey if its > 10 GeV spectrum has a soft photon index ∼ 2.7, but degree-scale 0.1 − 10 TeV pion-decay emission could be detected if the cosmic-ray spectrum hardens above >100 GeV. The 30 Doradus star-forming region is detectable if acceleration efficiency is on the order of 1 − 10% of the mechanical luminosity and diffusion is suppressed by two orders of magnitude within < 100 pc. Finally, the survey could probe the canonical velocity-averaged cross section for self-annihilation of weakly interacting massive particles for cuspy Navarro-Frenk-White profiles.
Keywords: very-high energy (VHE) gamma-rays, Cherenkov Telescope Array Observatory, Large Magellanic Cloud, pulsar wind nebulas, galaxiesstar-forming regions, cosmic rays, dark matter
Published in RUNG: 02.06.2023; Views: 1156; Downloads: 1
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Keywords: slovenščina, netožilniški glagoli, sekundarni nedovršniki, morfem, tematski vokal
Published in RUNG: 21.03.2023; Views: 1004; Downloads: 3
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