Seminar
615 events

Topological Photonics and the fourdimensional quantum Hall effect
July 3 (Tue) at 15:00  17:00, 2018
Tomoki Ozawa (Senior Research Scientist, iTHEMS)
In this seminar, I will give an introduction to topological photonics, that is, the study of topological band structures and resulting topological phenomena in photonic systems. I will first review basic concepts of topological band structures, and then explain what it means to realize topological band structures in photonic systems. I will particularly emphasize some important differences with respect to solidstate electron systems. I then present some of my own works in topological photonics, such as the synthetic dimensions in photonic systems, which allows one to explore models and phenomena in high dimensions including the fourdimensional quantum Hall effect.
Venue: 1F Meeting Room, AIMR Main Building
Event Official Language: English

Seminar
Denso IT Lab. and RIKEN Joint Innovation Seminar
June 29 (Fri) at 16:00  17:40, 2018
16:0017:00 Denso IT Laboratory "About Denso IT lab." H. Iwasaki (Denso) "HumanCar interface" H. Tsukahara (Denso) "Math in machine leaning and computer vision" K. Ishikawa (Denso) 17:0017:40 RIKEN "Math bridging between classical and quantum physics: quantum hall effect in classical system" T. Ozawa (RIKEN) "DiOmega: a new particle predicted by Kcomputer with mathematical science" S. Gongyo (RIKEN)
Venue: Common Room #246248
Event Official Language: Japanese

Seminar
Introduction to spinboson model
June 22 (Fri) at 10:30  17:30, 2018
Takeo Kato (The Institute for Solid State Physics (ISSP), The University of Tokyo)
10:3012:30 Introduction to spinboson model @DR3 (14th Building 213) 14:0015:30 Kondo effect @DR7 (14th Building 217) 16:0017:30 Detail of NIBA formalism @DR7 (14th Building 217)
Venue: Yagami Campus, Keio University
Event Official Language: Japanese

Relative and equivariant Lagrangian Floer homology and AtiyahFloer conjecture
June 19 (Tue) at 14:30  16:00, 2018
Kenji Fukaya (Senior Visiting Scientist, iTHEMS / Permanent Member, Simons Center for Geometry and Physics, Stony Brook University, New York, USA)
AtiyahFloer conjecture concerns a relationship between Floer homology in Gauge theory and Lagrangian Floer homology. One of its difficulty is that the symplectic manifold on which we consider Lagrangian Floer homology is in general singular. In this talk I will explain that, by using relative and equivariant version of Lagrangian Floer homology, we can resolve this problem and can at least state the conjecture as rigorous mathematical conjecture. Supported by RIKEN iTHEMS and Tuesday Seminar on Topology (Graduate School of Mathematical Sciences, The University of Tokyo).
Venue: Room 056, Graduate School of Mathematical Sciences, The University of Tokyo
Event Official Language: Japanese

Seminar
1form LiebSchultzMattis 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 AcceleratorBased Science (RNC))
The LiebSchultzMattis 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 LiebSchultzMattis theorem to systems with higherform symmetries, which act on extended objects of dimension n > 0. The prototypical lattice system with higherform symmetry is the pure abelian lattice gauge theory whose action consists only of the field strength. We first construct the higherform generalization of the LiebSchultzMattis 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 RokhsarKivelson point of the quantum dimer model, we diagnose and compute the mixed ’t Hooft anomaly corresponding to the higherform LiebSchultzMattis theorem.
Venue: SUURICOOL (Kyoto)
Event Official Language: Japanese

Seminar
AbelianHiggs dualities in quantum defectmediated melting phase transitions
April 27 (Fri) at 14:30  17:30, 2018
Aron Beekman (Keio University)
In the study of zerotemperature 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, NambuGoldstone modes are represented as gauge bosons, mediating longrange interactions between topological defects. When the latter condense, those bosons get as mass via the AndersonHiggs mechanism, which signals the loss of rigidity and the restoration of symmetry. I will first review the beststudied case: the 2+1D superfluidinsulator 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

Seminar
Thermodynamic of a onedimensional Bose gas at low temperature & superfluidity in neutronstar matter
April 24 (Tue) at 15:30  16:30, 2018
Giulia De Rosi (The Institute of Photonic Sciences, Barcelona, Spain)
Ultracold atomic gases and neutronstar matter play a paramount importance in manybody physics, by exhibiting important analogies and differences. One of the most interesting phenomena shared by both systems is provided by superfluidity. In the first part of the talk, I will show that the chemical potential of a onedimensional (1D) interacting Bose gas exhibits a nonmonotonic temperature dependence which is peculiar of superfluids. The effect is a direct consequence of the phononic nature of the excitation spectrum at large wavelengths exhibited by 1D Bose gases. For low temperatures T, I demonstrate that the coefficient in the $T^2$ expansion of the chemical potential is defined by the zerotemperature density dependence of the sound velocity and it has been calculated along the crossover between the Bogoliubov weaklyinteracting gas and the TonksGirardeau gas of impenetrable bosons. The theoretical predictions along the crossover are confirmed by comparison with the exactly solvable YangYang model in which the finitetemperature equation of state is obtained numerically by solving Betheansatz equations. In the second part of the talk, I will show the results of a study of the superfluid gap in pure neutron matter, associated with the formation of Cooper pairs in the $^1S_0$ channel. The interaction responsible of the onset of superfluidity is an effective interaction coming from a nuclear Hamiltonian strongly constrained by phenomenology and obtained from the correlated basis function (CBF) perturbation theory and the formalism of cluster expansions. The calculations have been carried out using an improved version of the CBF effective interaction, in which threenucleon forces are taken into account using a microscopic model. Our results show that the superfluid transition occurs at values of densities corresponding to the neutronstar inner crust.
Venue: Seminar Room #160
Event Official Language: English

Numerical analysis of point vortex dynamics by the method of fundamental solutions
April 17 (Tue) at 16:00  17:30, 2018
Koya Sakakibara (ProgramSpecific Assistant Professor, Graduate School of Science, Kyoto University)
iTHEMS / KUAMS Joint Seminar
Venue: Maskawa Hall, 1F, Maskawa Building for Education and Research
Event Official Language: Japanese

Seminar
Including an ocean mixing model in atmospheric data assimilation: a case of Typhoon Soudelor 2015
April 17 (Tue) at 15:00  15:30, 2018
Kohei Takatama (Postdoctoral Researcher, Data Assimilation Research Team, RIKEN Center for Computational Science (RCCS))
Venue: Maskawa Hall, 1F, Maskawa Building for Education and Research
Event Official Language: English

Resurgence Theory for NonPerturbative 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

Seminar
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

Seminar
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 AcceleratorBased Science (RNC))
Venue: Seminar Room #160
Event Official Language: English

Seminar
Several identities related to the degenerate Bernoulli polynomials and numbers
February 24 (Sat) at 16:00  17:00, 2018
Takao Komatsu (Professor, Wuhan University, China)
In this talk we demonstrate some relations in degenerate Bernoulli polynomials, which may be expressed as a general convolution identity. We also show some properties of hypergeometric degenerate Bernoulli polynomials and numbers.
Venue: Seminar Room #160
Event Official Language: English

Seminar
Diophantine Frobenius Problems — counting theory, generating function and zeta functions
February 23 (Fri) at 16:00  17:00, 2018
Takao Komatsu (Professor, Wuhan University, China)
When a_1, ...,a_m are relatively prime positive integers, the number of solutions of the linear Diophantine equation a_1 x_1 + … + a_m x_m = b in nonnegative integers x_1, ...,x_m, for any integer b, is our concern. We show several formulas to give the largest integer b without solution. Then we discuss the generating function of the number of solutions. Finally, we derive an explicit expression for an inverse power series over the gaps values of numerical semigroups generated by two integers. It implies a set of new identities for the Hurwitz zeta function.
Venue: Seminar Room #160
Event Official Language: English

Statistical mechanics of tissue homeostasis
January 22 (Mon) at 14:00  15:00, 2018
Kyogo Kawaguchi (The University of Tokyo)
Adult tissues undergo rapid turnover as mature cells are continuously lost and new cells arise through cell division. The balance between the gain and loss of cells must be finely orchestrated to maintain tissues, but how this balance is achieved remains largely unknown. Previous works [1] have used universal scaling laws to claim that the fate choice of stem cells (division or differentiation) are made strictly cellautonomously. However, we recently recorded every stem cell fate choice within the mouse skin epidermal regions over one week and found that, far from being cellautonomous, stem cell loss by differentiation is compensated by direct neighboring division [2]. In this talk, I will describe a model of tissue homeostasis using a macroscopic nonequilibrium setup, and explain how the coarsegraining of this model will lead to the effective dynamics of the voter model (DP2). I will show how we can use the property of dynamical crossover in the model from the cellautonomous regime (critical birthdeath model) to the fatecoordinated regime (voter model) to measure the length and time scales of stem cell coordination. I will then explain the pitfall in twodimensions of using scaling relations for the clonal fate trace of cells, and present the workaround we used in the data analysis to definitively show the existence of celltocell fate correlation.
Venue: Common Room #246248
Event Official Language: English

Compactstar phenomena and equation of state
December 28 (Thu) at 10:30  11:30, 2017
Shun Furusawa (Special Postdoctoral Researcher, iTHEMS)
Venue: SUURICOOL (Kyoto)
Event Official Language: English

Theoretical study on the universality in biological clock and its speciesspecificity
December 27 (Wed) at 16:00  17:00, 2017
Gen Kurosawa (Research Scientist, iTHEMS / Research Scientist, Theoretical Biology Laboratory, RIKEN)
Venue: SUURICOOL (Kyoto)
Event Official Language: English

Mathematical Modeling of Retinal Cellular Mosaic Pattern Formation
December 27 (Wed) at 13:30  14:30, 2017
Noriaki Ogawa (Postdoctoral Researcher, Interdisciplinary Theoretical Science Research Group (iTHES), RIKEN)
Venue: SUURICOOL (Kyoto)
Event Official Language: English

Topology of linear operators and topological insulators
December 27 (Wed) at 10:30  11:30, 2017
Yosuke Kubota (Research Scientist, iTHEMS)
Venue: SUURICOOL (Kyoto)
Event Official Language: English

Chiral Phases in Frustrated 2D Antiferromagnets and Fractional Chern Insulators
December 21 (Thu) at 11:00  12:00, 2017
Eduardo Fradkin (University of Illinois, USA)
Venue: #535537, 5F, Main Research Building
Event Official Language: English
615 events
Events
Categories
series
 iTHEMS Colloquium
 MACS Colloquium
 iTHEMS Seminar
 iTHEMS Math Seminar
 DMWG Seminar
 iTHEMS Biology Seminar
 iTHEMS Theoretical Physics Seminar
 Information Theory SG Seminar
 Quantum Matter Seminar
 ABBLiTHEMS Joint Astro Seminar
 MathPhys Seminar
 Quantum Gravity Gatherings
 RIKEN Quantum Seminar
 Quantum Computation SG Seminar
 NEW WG Seminar
 LabTheory Standing Talks
 QFTcore Seminar
 STAMP Seminar
 QuCoIn Seminar
 Number Theory Seminar
 BerkeleyiTHEMS Seminar
 iTHEMSRNC Meson Science Lab. Joint Seminar
 AcademicIndustrial Innovation Lecture
 RIKEN Quantum Lecture
 Theory of Operator Algebras
 iTHEMS Intensive CourseEvolution of Cooperation
 Introduction to PublicKey Cryptography
 Knot Theory
 iTHES Theoretical Science Colloquium
 SUURICOOL Seminar
 iTHES Seminar