STAMP Seminar

Potential Toolkit to Attack Nonperturbative Aspects of QFT －Resurgence and related topics－

September 7 (Mon) - 25 (Fri), 2020

Aleksey Cherman (University of Minnesota, USA)
Gerald Dunne (University of Connecticut, USA)
Mithat Unsal (North Carolina State University, USA)
Toshiaki Fujimori (Keio University)
Yasuyuki Hatsuda (Rikkyo University)
Masazumi Honda (Assistant Professor, Yukawa Institute for Theoretical Physics, Kyoto University)
Okuto Morikawa (Ph.D. Student, Kyushu University)
Naohisa Sueishi (Nagoya University)
Masahito Yamazaki (Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), The University of Tokyo)

Recently, there have been significant developments in theoretical techniques/frameworks to tackle non-perturbative aspects of quantum field theory (QFT) such as the resurgence theory, the Lefschetz thimble method, ’t Hooft anomaly matching, and novel lattice setups. Such developments are still growing very rapidly and making fruitful connections not only among physicists involved in fields with broad energy scales but also with mathematicians. These developments would enable us to unveil rich and exciting physics of QFT in the non-perturbative regime. It is of primary importance to hold a workshop for researchers in various fields related to the topics to get together and overview/share the recent progresses, to discuss future directions, and to seek for possible new collaborations bridging various fields of physics/mathematics. For more information, please see on the related link.

Venue: YITP (Kyoto University), Zoom, and Mozilla hubs

Event Official Language: English

Introduction to quantum many-body system

September 5 (Thu) - 6 (Fri), 2019

Hosho Katsura (Associate Professor, Department of Physics, Graduate School of Science, The University of Tokyo)

Venue: #535-537, Main Research Building / #435-437, Main Research Building

Event Official Language: Japanese

Large scale dynamics of integrable systems

July 12 (Fri) at 16:00 - 17:00, 2019

Takato Yoshimura (King's college London, UK)

Hydrodynamics has been a universal tool to study the large scale (long-wavelength) dynamics of interacting many-body systems. It had not been, however, applied to integrable systems until 2016 when two papers, one of which is ours [Physical Review X 6 (4), 041065, (2016)], provided a first legitimate hydrodynamic theory of integrable systems that incorporates the anomalous number of conserved quantities in those systems. The key idea of the theory rests upon the use of thermodynamic Bethe ansatz that allows us to express the essential ingredients in hydrodynamics, densities and currents average of conserved charges, in terms of the quasi-particle basis. In this talk I will review this new hydrodynamic theory, coined generalized hydrodynamics (GHD). I will first introduce the basics of GHD, highlighting the difference with the conventional hydrodynamics (i.e. hydrodynamics for non-integrable systems). I will then present some recent developments in the theory, such as the exact computation of the Drude weight and hydrodynamic correlation functions.

Venue: Building 14 #213, Yagami campus, Keio University

Event Official Language: English

Spintronics in Non-Inertial Frames

November 15 (Thu) at 13:00 - 18:00, 2018

Mamoru Matsuo (University of Chinese Academy of Sciences, China)

Venue: Seminar Room #160

Event Official Language: Japanese

Non-Hermitian phase transition from a polariton Bose-Einstein condensate to a photon laser

September 28 (Fri) at 13:30 - 17:00, 2018

Ryo Hanai (Osaka University)

Venue: Seminar Room #160

Event Official Language: Japanese

Introduction to topological band structure

July 6 (Fri) at 10:30 - 17:30, 2018

Tomoki Ozawa (Senior Research Scientist, iTHEMS)

In this seminar, I give an introduction to topological band structures. Topological band structure is the fundamental idea to understand phenomena such as the quantum Hall effect, topological insulators, and topological superconductors. Although originally found in fermionic electron systems, topological band structure is essentially a single-particle property, and thus the same phenomenon can arise also in bosonic systems. In fact, topological band structure does not even need quantum mechanics; topological band structure can arise in classical waves inside a periodic medium, such as electromagnetic waves or classical mechanical waves. In this seminar, I first give a brief introduction to key concepts in topological band structures, such as Berry curvature, Chern number, bulk-edge correspondence, and ten-fold way classification of topological insulators. I then explain how topological band structure can arise in classical systems, giving a brief introduction to the field of topological photonics and topological mechanics.

Venue: Seminar Room #160

Event Official Language: Japanese

Introduction to spin-boson model

June 22 (Fri) at 10:30 - 17:30, 2018

Takeo Kato (The Institute for Solid State Physics (ISSP), The University of Tokyo)

10:30-12:30 Introduction to spin-boson model @DR3 (14th Building 213) 14:00-15:30 Kondo effect @DR7 (14th Building 217) 16:00-17:30 Detail of NIBA formalism @DR7 (14th Building 217)

Venue: Yagami Campus, Keio University

Event Official Language: Japanese

1-form Lieb-Schultz-Mattis theorem and anomaly matching in quantum dimer model

June 8 (Fri) at 13:30 - 17:00, 2018

Yuta Kikuchi (RBRC Researcher, Theory Group, RIKEN BNL Research Center, RIKEN Nishina Center for Accelerator-Based Science (RNC))

The Lieb-Schultz-Mattis theorem dictates that a trivial symmetric insulator in lattice models is prohibited if lattice translation symmetry and U(1) charge conservation are both preserved. In this talk, we discuss the generalization of the Lieb-Schultz-Mattis theorem to systems with higher-form symmetries, which act on extended objects of dimension n > 0. The prototypical lattice system with higher-form symmetry is the pure abelian lattice gauge theory whose action consists only of the field strength. We first construct the higher-form generalization of the Lieb-Schultz-Mattis theorem with a proof. We then apply it to the U(1) lattice gauge theory description of the quantum dimer model on bipartite lattices. Finally, using the continuum field theory description in the vicinity of the Rokhsar-Kivelson point of the quantum dimer model, we diagnose and compute the mixed ’t Hooft anomaly corresponding to the higher-form Lieb-Schultz-Mattis theorem.

Venue: SUURI-COOL (Kyoto)

Event Official Language: Japanese

Abelian-Higgs dualities in quantum defect-mediated melting phase transitions

April 27 (Fri) at 14:30 - 17:30, 2018

Aron Beekman (Keio University)

In the study of zero-temperature quantum phase transitions, instead of looking how symmetry is broken, it is often useful to see how symmetry can be restored by the condensation of topological defects. Through a duality mapping, Nambu-Goldstone modes are represented as gauge bosons, mediating long-range interactions between topological defects. When the latter condense, those bosons get as mass via the Anderson-Higgs mechanism, which signals the loss of rigidity and the restoration of symmetry. I will first review the best-studied case: the 2+1D superfluid-insulator transitions where the defects are U(1) vortices. Consecutively several extensions are discussed: going to 3+1D where the defects are not point particles but strings, and quantum elasticity, which studies breaking of spatial translations and rotations.

Venue: Seminar Room #160

Event Official Language: English

Resurgence Theory for Non-Perturbative Quantum Analysis

March 28 (Wed) at 13:00 - 15:00, 2018

Tatsuhiro Misumi (Visiting Scientist, iTHEMS / Lecturer, Akita University)

Venue: Seminar Room #160

Event Official Language: English

Introduction to exact WKB analysis

March 27 (Tue) at 10:00 - 12:00, 2018

Kohei Iwaki (Nagoya University)

Venue: Seminar Room #160

Event Official Language: English

Anomaly matching for spin chains

March 19 (Mon) at 14:00 - 16:00, 2018

Yuya Tanizaki (Special Postdoctoral Researcher, Theory Group, RIKEN Nishina Center for Accelerator-Based Science (RNC))

Venue: Seminar Room #160

Event Official Language: English