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宇宙物理学セミナーアーカイブ


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2021/1/21 (木)

UTAPwiki/セミナー/宇宙物理学セミナー

Speaker 1: Minori Shikauchi (n.b. slides and oral presentation will be in English)

Title: On the use of CHIME to Detect Long-Duration Radio Transients from Neutron Star Mergers

Abstract:
A search for afterglows with radio telescope Canadian Hydrogen Intensity Mapping Experiment (CHIME) will provide an alternative measurement of the BNS merger rate relying on entirely different physical process and so will be an important confirmation of the GW-measured rate. Using a more specific detection algorithm based on likelihood ratio statistics, we estimated 155 afterglows per year can be detected with CHIME and 95 % of them are off-axis afterglow. Our result leads to the prediction of a slightly smaller event rate than previous work (Feng+2014), but confirms the essential conclusion of the earlier analysis, namely that using CHIME to search for synchrotron afterglows will be effective at constraining the astrophysical merger rate as well as orphan afterglow search.

Speaker 2: Fumio Uchida (n.b. slides and oral presentation will be in Japanese)

Title: Generation of baryon isocurvature perturbations from primordial magnetic fields and its cosmological consequence (初期磁場によるバリオン等曲率揺らぎの生成とその宇宙論的帰結)

Abstract:
Magnetic fields are ubiquitous in the universe, and even in the voids, where few astrophysical objects that could amplify seed fields through e.g., the galactic dynamo exist, lower bounds of the strength of the so-called intergalactic magnetic fields are observationally suggested. A possibility is that such cosmological magnetic fields originate in the very early universe. In the talk, I assume primordial magnetic fields before the electroweak symmetry breaking and argue that such fields unavoidably generate baryon isocurvature perturbations through a conversion from magnetic helicity to baryon number through the chiral anomaly in the Standard Model. For a successful big-bang nucleosynthesis is a constraint put on the baryon isocurvature perturbations, and hence we can constrain the properties of the primordial magnetic fields. The condition is so strong that the intergalactic magnetic fields cannot be purely primordial and that some mechanisms of amplification or generation of magnetic fields after the electroweak symmetry breaking are needed.

2021/1/28 (木)

UTAPwiki/セミナー/宇宙物理学セミナー

Speaker: Naoto Kuriyama

2021/2/4 (木)

UTAPwiki/セミナー/宇宙物理学セミナー

Speaker: Koh Ueno

2021/2/11 (木)

UTAPwiki/セミナー/宇宙物理学セミナー
No seminar (National Holiday)



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