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余震にそなえて、しばらくの間、セミナーのほとんどは4号館1階のピロティで行われます。

今後2週間の予定

→カレンダーはこちら
※下記のセミナーの他に新着論文紹介のセミナー(30分)が、月曜日(10:00-10:30)、水曜日(12:00-12:30)、金曜日(10:00-10:30)にあります。場所は4号館ピロティです。

2020-10-26 (月) 観測的宇宙論速報
    UTAPwiki/セミナー/観測的宇宙論速報
    担当者:Hayashi
    時間 :10:30-12:00
    場所 :理学部4号館ピロティ前セミナー室
    内容:添付ファイル [添付] 参照

2020-10-26 (月) 初期宇宙・相対論速報
    UTAPwiki/セミナー/初期宇宙・相対論速報 Topic 1: Baryon isocurvature perturbations from non-helical magnetic fields † ↑Topic 2: Saddle-point solutions from gradient flow † ↑Fumio Uchida † The first topic: The origin of the baryon asymmetry of the universe is a fundamental problem in cosmology. Among many proposed mechanisms that could solve it, baryogenesis from helical magnetic fields is characteristic in that it relates baryon asymmetry directly to the cosmic magnetic fields. In the scenario, the chiral anomaly in the Standard Model converts hypermagnetic helicity into baryon number. The observed baryon-to-entropy ratio gives conditions on the strength and the coherence length of the magnetic fields, and the generation of baryon isocurvature perturbations gives another constraint because it affects the big-bang nucleosynthesis. Counterintuitively, while the net baryon asymmetry is produced only from the helical part, the baryon isocurvature perturbations are generated from both helical and non-helical parts of the magnetic power spectrum. In the seminar, I focus on and explain how even non-helical magnetic fields can generate baryon isocurvature perturbations. The second topic: In most of the scenarios of baryogenesis, sphalerons play an important role because they violates baryon number. However, when one wants to find a sphaleron solution and estimate its energy, a difficulty sometimes arises because sphalerons are not local minima but saddle-points. Also, when one studies vacuum decay, to find bounce configurations is an important problem. In this case, one has to overcome the same difficulty because bounce solutions are saddle-points. However, a method that is intuitively understandable to find these solutions is proposed recently. In the seminar, I introduce the methodology and prove its validity, mainly following [3]. The seminar will be organized as follows. The first 40 min is devoted to the first topic, based on [1,2], then 10 min break, and the next 40 min to the second, based on [3,4]. References:
    [1] M. Giovannini, and M. E. Shaposhnikov, PRD57, 2186 (1998)
    [2] K. Bamba, PRD74, 123504 (2006); T. Fujita, and K. Kamada, PRD93, 083520 (2016); K. Kamada, and A. J. Long, PRD94, 063501 (2016); K. Kamada, and A. J. Long, PRD94, 123509 (2016)
    [3] S. Chigusa, T. Moroi, and Y.Shoji, PLB800, 135115 (2020)
    [4] R. Sato, PRD101, 016012 (2020); Y. Hamada, and K. Kikuchi, PRD101, 096014 (2020).

2020-11-02 (月) 観測的宇宙論速報
    UTAPwiki/セミナー/観測的宇宙論速報
    担当者:Moriwaki
    時間 :10:30-12:00
    場所 :理学部4号館ピロティ前セミナー室
    内容:添付ファイル 20201019_MondaySeminar_TilmanHartwig.pdf 参照


セミナー週間予定

10111213141516
新着論文@ピロティ観測的宇宙論速報初期宇宙・相対論速報
新着論文@ピロティ
ランチセミナー昼食会宇宙物理学セミナー
新着論文@ピロティ天体核・素粒子物理速報?


須藤研ゼミ週間予定

10111213141516
大地(13:30-15:00)Yuxin (15:30-17:00)
柏木4年生理論演習(13:30-16:00)
天文学ゼミ(10:30-12:00)
岡(10:30-12:00)



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