Kazuki Sakurai, University of Warsaw
Natural and Unnatural SUSY in light of Proton Decay and Gauge Unification
I present the recent study on natural and unnatural SUSY in light of the proton decay and gauge unification. We show that the low energy SUSY mass spectrum is linked to the proton decay via the unification scale, and future nucleon decay experiments will provide a non-trivial upper bound on the superpartner masses. We also show that the mirage mediation provides a consistent picture of natural SUSY. For unnatural SUSY, we present a systematic study on split SUSY and predict a unique spectrum, which could be around the corner of discovery.
Aya Ishihara, Chiba U
Recent progresses on the neutrino astronomy from IceCube
IceCube is a cubic kilometer scale, deep-ice Cherenkov neutrino detector at the South Pole. IceCube’s cosmic neutrino searches cover an energy region all the way from TeV and less to EeV and higher. Following the first observation of PeV neutrino events and successful measurements of high energy extraterrestrial neutrino flux in the energy region between a few tens of TeV and PeV significantly above the atmospheric neutrino background flux by IceCube, the field of neutrino astrophysics is becoming more and more active. Also in the EeV energy region, a flux of ‘cosmogenic’ neutrinos generated by interactions of ultra-high energy cosmic rays on intervening radiation backgrounds is expected. The cosmogenic neutrinos will give us insight into the sources of the ultra-high energy cosmic- rays (UHECRs). In this talk, I review the recent results from IceCube on cosmic neutrino observations. In particular I highlight the multi-messenger observation using the neutrino as the trigger for the gamma-ray/x-ray/optical telescopes, and constraints on the UHECR sources from the observation of cosmogenic neutrinos. Finally I discuss the future prospects for such activities.
Ryuji Daido, Tohoku University
Enhanced axion-photon coupling in a GUT with hidden photon
We first review current status of QCD axion searches, which generically rely on interaction between the axion and SM photon. Next, we show that the axion-photon coupling is modified in the presence of massless hidden photon which has kinetic mixing with the SM photon. If the kinetic mixing and hidden gauge coupling are \mathcal{O}(1), the axion-photon coupling becomes several tens of times larger. Finally, we consider QCD axion in SU(5) GUT with massless hidden photon. Gauge coupling unification is determined by the size of kinetic mixing only, and requires relatively large kinetic mixing, which is naturally generated when hidden gauge coupling is large. We find enhancement factor of axion-photon coupling is about 20 in our model.
Yoshio Kikukawa, University of Tokyo
On the gauge invariant path-integral measure for the overlap Weyl fermions in 16 of SO(10)
We consider the lattice formulation of SO(10) chiral gauge theory with left-handed Weyl fermions in the sixteen dimensional spinor representation (16) within the framework of the Overlap fermion/the Ginsparg-Wilson relation. We propose a manifestly gauge invariant path-integral measure for the left-handed Weyl field using the whole components of the Dirac field, but the right-handed part of which is just saturated completely by inserting a suitable product of the SO(10)-invariant ‘t Hooft vertices in terms of the right-handed field. The definition of the measure applies to all possible topological sectors. The measure possesses all required transformation properties under lattice symmetries and the induced effective action is CP invariant. The global U(1) symmetry of the left-handed field is anomalous due to the non-trivial transformation of the measure, while that of the right-handed field is explicitly broken by the ‘t Hooft vertices. There remains the issue of locality in the gauge-field dependence of the Weyl fermion measure, but the question is well-defined and can be addressed in the weak gauge-coupling expansion at least using Monte Carlo methods without encountering the sign problem.
Yuhma Asano, Dublin Institute for Advanced Studie
Phase transitions in the BMN matrix model
Formulating string theory or M-theory by a gauge theory is an attractive idea which has been extensively studied. Especially, realisation of geometries from the lower dimensional gauge theory is an intriguing and challenging problem. The necessity of such emergent geometry suggests that there should be a phase transition in the gauge theory and that a geometry would appear as its temperature decreases. In this talk, we focus on the BMN matrix model, which is considered as a non-perturbative formulation of M-theory on the pp-wave geometry and also conjectured to have a gauge/gravity duality, which relates the vacua on the gauge theory side to bubbling geometries in the type IIA supergravity. Our preliminary results of Monte Carlo simulations show two phase transitions and one of them looks related with emergent geometry.
加藤政博, 自然科学研究機構分子科学研究所
[光渦についての特別セミナー] 自由電子による光渦の放射
通常の光は平面あるいは球面状の波面を持つ。これに対し約25年前に、螺旋状の波面を持つ奇妙な光（光渦）が存在し、スピン角運動量とは別に軌道角運動量を運ぶ、とする理論的な研究成果が発表された。その後、レーザー光を特殊な光学素子を通すことで光渦を生成す
る手法が確立し、情報通信、ナノテクノロジー、イメージングなど幅広い分野への応用を目指して活発に研究が行われている。
一方、自然界における光渦の存在、あるいはその役割は、これまでほとんど議論がなされてこなかった。このような奇妙な光が自然現象として放射されるとは認識されていなかったようである。しかし、最近、円軌道を描く電子からの放射が光渦の性質を持つことが理論的に示され、また、シンクロトロン放射を用いた実験的検証も行われた。円軌道放射は、サイクロトロン／シンクロトロン放射、円偏光コンプトン散乱などの基礎を成し、宇宙物理学・プラズマ物理学から加速器光源技術に至る幅広い分野で重要な役割を果たす。従って、光渦は、天体周辺の磁気圏から高エネルギー加速器まで、自然界や実験室の様々な状況で自然に放射され、その波長は物理的なパラメータに応じて電波からガンマ線に及ぶはずである。
本講演では、光渦とはどのようなものか、また、これまでの光渦に関する研究について短く概観した後、円軌道放射が螺旋状の波面を有し軌道角運動量を運ぶことを初等的な古典電磁気学で示し、その直感的な説明を試みる。また、高エネルギー電子が光渦を放射する実験的な証拠を紹介する。講演の終わりには、自然科学や物理学における光渦研究の様々な可能性について皆さんと議論させていただきたい。
梶田隆章, 東京大学
[第四回KEK連携コロキウム] 重力波の観測に挑むＫＡＧＲＡプロジェクト
現在岐阜県飛騨市神岡で、東大宇宙線研、高エネルギー加速器研究機構、国立天文台の協力のもと建設を進めているＫＡＧＲＡでは重力波を観測し、アメリカのＬＩＧＯやヨーロッパのＶｉｒｇｏなどと共に重力波の天文学を切り開きたいと考えています。本講演ではＫＡＧＲＡの現状と、ＫＡＧＲＡの目指すサイエンスについてお話しします。
Yoshiyuki Inoue, RIKEN
[Cosmophysics group seminar] Toward the understanding of magnetic fields in the vicinity of active supermassive black holes
Magnetic fields of active supermassive black holes have not been measured yet, although it is one of the most fundamental parameters in black hole physics such as for launching mechanism of relativistic jets and generation of hot coronae. In this talk, I will report our new measurements of magnetic fields in several tens Schwarzschild radii of central black holes. Utilizing ALMA and NuSTAR, we successfully detected coronal synchrotron emission. The estimated magnetic field strength is not strong enough to keep corona hot.
Naoki Yamamoto, Keio University
Chirality, Topology, and Astrophysics
Chirality of fermions has a topological nature. This microscopic property modifies the macroscopic hydrodynamic behavior and leads to unusual transport protected by topology in relativistic systems. We argue that these topological tranport phenomena should play important roles in the evolution of supernovae and could potentially solve the problems in astrophysics, such as the origins of supernova explosions and magnetars.
Matsuo Sato, Hirosaki University
弦幾何と弦理論の非摂動論的定式化
