Lab-Theory Standing Talks #1

March 16 (Thu) at 13:00 - 13:30, 2023

Dr. Hideshi Ooka (Research Scientist, Biofunctional Catalyst Research Team, RIKEN Center for Sustainable Resource Science (CSRS))

Venue: 3rd floor public space, Main Research Building

Event Official Language: English

Towards S-matrix theory of unstable particles

March 15 (Wed) at 13:30 - 15:00, 2023

Dr. Katsuki Aoki (Research Assistant Professor, Yukawa Institute for Theoretical Physics, Kyoto University)

The S-matrix is one of the central objects in quantum field theory and gains renewed interest recently to understand the possible structures of low-energy effective field theories and quantum gravity. However, most of the particles have finite decay widths and thus do not appear in asymptotic states. Therefore, the standard S-matrix arguments may not be directly applied to scatterings of such unstable particles and we need to formulate “the S-matrix theory of unstable particles” to properly understand the availability of the S-matrix arguments in realistic systems. In this talk, I will talk about the first steps towards this goal. In particular, I will discuss non-perturbative consequences of unitarity in a scattering amplitude of unstable particles and its analytic properties.

Venue: Hybrid Format (Common Room 246-248 and Zoom)

Event Official Language: English

Neutrinos from the big bang: probing cosmic gravitational inhomogeneities & magnetic fields in the early universe

March 13 (Mon) at 13:30 - 15:00, 2023

Prof. Gordon Baym (Professor Emeritus, University of Illinois, USA)

Primordial neutrinos from the Big Bang are about 100 times more prevalent than solar neutrinos, and at least two-thirds of them are now non-relativistic. These relic neutrinos, which have never been detected, decoupled in the early universe predominantly in helicity eigenstates. As I will discuss, their subsequent propagation through gravitational inhomogeneities and even background gravitational radiation, as well as cosmic and galactic magnetic fields partially flips their helicities, and can produce noticeable effects in their eventual detection. I will briefly mention future detection of relic neutrinos.

Venue: Common Room #246-248 (Main Venue) / via Zoom

Event Official Language: English

Cosmic magnetism and its effects on the observed properties of ultra high-energy cosmic rays

March 10 (Fri) at 14:00 - 15:00, 2023

Dr. Ellis Owen (JSPS International Research Fellow, Theoretical Astrophysics Group, Department of Earth and Space Science, Graduate School of Science, Osaka University)

Ultra high-energy (UHE) cosmic rays (CRs) from distant sources interact with intergalactic radiation fields, leading to their spallation and attenuation through photo-hadronic processes. Their deflection and diffusion in large scale intergalactic magnetic fields (IGMFs), in particular those associated with Mpc-scale structures, alter the cumulative cooling and interactions of a CR ensemble to modify their spectral shape and composition observed on Earth. In this talk, I will demonstrate the extent to which IGMFs can affect observed UHE CRs, and show that source population models are degenerate with IGMF properties. Interpretation of observations, including the endorsement or rejection of any particular UHE CR source classes, needs careful consideration of the structural properties and evolution of IGMFs. Future observations providing tighter constraints on IGMF properties will significantly improve confidence in assessing UHE CR sources and their intrinsic CR production properties.

Venue: via Zoom / Common Room #246-248

Event Official Language: English

Feynman’s proof of integrability of Calogero system from a modern point of view

March 10 (Fri) at 10:00 - 11:30, 2023

Dr. Yehao Zhou (Project Researcher, Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), The University of Tokyo)

In his last year of life Feynman was interested in integrable system, and in his study of Calogero models he came up with his own proof of the commutativity of integrals of motions of these models, which remains unpublished until it was transcribed by Polychronakos in 2018. His idea is to organize integrals of motions of a Calogero model into a generating function of differential operators which look like a correlation function in a certain free theory, then he showed that the generating function of differential operators commute for all spectral values, which leads to a proof of commutativity of integrals of motions. He commented on his proof “I learn nothing, no real clue as to why all this works, and what it means”. Recently in a joint work with Davide Gaiotto and Miroslav Rapcek we identify Feynman’s generating function as the correlation function of Miura operators in a W-algebra of type A, and in the rational and trigonometric cases we show that they equal to certain elements in the Dunkl representation of corresponding spherical Cherednik algebras in type A, which make the commutativity self-evident. This progress is a byproduct of a project in the study of M2-M5 brane junction in the M-theory.

Venue: Common Room #246-248 / via Zoom

Event Official Language: English

Reproductive interference can affect trait diversity of closely related animal species

March 9 (Thu) at 16:00 - 17:00, 2023

Mr. Keiichi Morita (Ph.D. Student, School of Advanced Sciences Department of Evolutionary Studies of Biosystems, SOKENDAI, the Graduate University for Advanced Studies)

Previous theoretical studies have considered that evolution driven by resource competition is important for the creation and maintenance of biodiversity. Recently, reproductive interference caused by misrecognition of sexual traits such as calling between closely related species has been increasingly important for the creation and maintenance of diversity, but the impact of reproductive interference on trait diversity between closely related species remains unresolved. In this study, we combined population dynamics model with reproductive interference in two closely related species with an evolutionary model of traits related to reproduction to examine the impact of reproductive interference on the evolutionary consequences of reproductive traits in the two closely related species. The model assumed a trade-off in which reproductive interference weakens as reproductive traits diverge between the two species, but predation pressure increases as the reproductive traits diverge from their optimum traits in their habitat. For simplicity, we assumed that only one species evolves. Our model analysis revealed that convergence and divergence of traits of two closely related species occurs depending on initial trait divergence. Also, under the parameter condition where trait convergence occurs, large mutation makes trait divergence possible. Our model will provide a new framework for understanding evolutionary dynamics in ecological communities containing closely related species.

Venue: via Zoom

Event Official Language: English

RIKEN-Nara Women's University Joint Diversity Promotion Workshop

March 7 (Tue) at 13:30 - 13:00, 2023

The RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS) and the Faculty of Science at Nara Women's University are promoting a project to foster female researchers under the auspices of the RIKEN Diversity Promotion Office. As part of the program, 17 undergraduate and graduate students from Nara Women's University will visit several laboratories on the RIKEN Wako campus to ask questions about their research, hold workshops with iTHEMS researchers, and present their own research. Organizers: RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program Faculty of Science, Nara Women's University Program: Tuesday, March 7 13:30-14:00 Opening remarks by Tetsuo Hatsuda (iTHEMS) 14:00-15:30 Erika Kawakami Laboratory (RQC) (S51, Chemistry and Materials Physics Bldg.) 15:30-17:00 Zhaomin Hou Laboratory (CSRS) (S51, Chemistry and Materials Physics Bldg.) 17:00-18:30 RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS) (C01, Main Research Bldg.) 18:30-21:00 Research Presentations by Nara Women's University Students (C01, Main Research Building) Wednesday, March 8 9:00-10:30 Nishina Center RIBF Facility (RNC) (E01, Nishina RIBF Bldg.) 10:30-12:00 Atsushi Miyawaki Laboratory (CBS) (C51, Brain Science Central Bldg.) 12:00-13:00 Lunch (C61, Welfare and Conference Bldg.) 13:00 Closing

Topological Kondo superconductors

March 2 (Thu) at 17:00 - 18:15, 2023

Dr. Yung-Yeh Chang (Postdoctoral Researcher, National Center for Theoretical Sciences & National Chiao Tung University, Taiwan)

Spin-triplet p-wave superconductors are promising candidates for topological superconductors. They have been proposed in various heterostructures where a material with strong spin-orbit interaction is coupled to a conventional s-wave superconductor by proximity effect. However, topological superconductors existing in nature and driven purely by strong electron correlations are yet to be studied. Here we propose a realization of such a system in a class of Kondo lattice materials in the absence of proximity effect. Therein, the odd-parity Kondo hybridization mediates ferromagnetic spin-spin coupling and leads to spin-triplet resonant-valence-bond (t-RVB) pairing between local moments. Spin-triplet p±p’ wave topological superconductivity is reached when Kondo effect co-exists with t-RVB [1]. We identify the topological nature by the non-trivial topological invariant and the Majorana zero modes at edges. Our results on the superconducting transition temperature, Kondo coherent scale, and onset temperature of Kondo hybridization not only qualitatively but also quantitatively agree with the observations for UTe2, a U-based ferromagnetic heavy-electron superconductor. *This work is supported by the National Science and Technology Council, Taiwan. Field: condensed matter physics Keywords: strongly correlated systems, topological superconductor, Kondo effect, resonant valence bond, heavy-fermion compounds

Venue: via Webex

Event Official Language: English

How to sit Maxwell and Higgs on the boundary of AdS

February 28 (Tue) at 13:30 - 15:00, 2023

Dr. Matteo Baggioli (Associate Professor, School of Physics and Astronomy, Shanghai Jiao Tong University, China)

Within the holographic correspondence, boundary conditions play a fundamental role in determining the nature of the dual field theory. In this talk, I will show how to exploit mixed boundary conditions to obtain dynamical electromagnetism in the boundary theory. This is necessary to apply AdS-CFT to many real-world applications, e.g., magnetohydrodynamics, plasma physics, superconductors, etc. where dynamical gauge fields and Coulomb interactions are fundamental. As a proof of concept, I will show two emblematic cases. First, I will prove that the results from the 4-dimensional Einstein-Maxwell bulk theory with these deformed boundary conditions are in perfect agreement with relativistic magneto-hydrodynamics in 2+1 dimensions. Second, I will discuss the collective excitations of a bona-fide holographic superconductor and prove the existence of the Anderson-Higgs mechanism therein.

Venue: Room 6209, Korakuen Campus, Chuo University (Main Venue) / via Zoom

Event Official Language: English

Interdisciplinary Science Conference in Okinawa (ISCO 2023)

February 27 (Mon) - March 3 (Fri), 2023

The scientific method of studying the natural world has persisted over the centuries. The key to its longevity and progression lies in sharing and building upon accumulated knowledge. Physics, which explores the origin of the universe and matter; biology, which studies living organisms, and their functions and evolution; and medicine, which explores health based on the structure and function of living organisms: all have made enormous advancements that impact all aspects of our lives. As the scientific study progresses, however, additional challenges have arisen which are increasingly difficult to solve. Many of the challenges that humanity faces are in achieving sustainable development. These include environmental changes due to climate change, food crises caused by the gap between population growth and food production, and pandemics caused by the spreading of resistant bacteria and viruses. To rise to these new challenges, it is important to reassess the issues from a broader perspective: to combine the knowledge and methods of different scientific fields and to look for new approaches that can bridge the boundaries and work across multiple fields The purpose of ISCO 2023 is to bring together leading researchers in their respective fields, explore methods for solving issues through the fusion of different fields, and form a new network of researchers. The workshop will bring together speakers from Japan and abroad in the fields of space science, particle and nuclear physics, quantum computing, life sciences, and medicine to discuss the challenges they face and the latest advancements in their respective fields. We call for presentations from fields related to those subjects mentioned above and on the sustainable development of humankind. In addition, we plan to hold a poster session to facilitate a wide range of discussions. We hope that the knowledge gained at this workshop will lead to the creation of new research fields that will not only advance basic science but will also help solve the various new challenges that humanity faces.

Venue: OIST Auditorium / via Zoom

Event Official Language: English

Algebra of symmetry in BF-like models in 3d and 4d

February 22 (Wed) at 14:00 - 15:30, 2023

Dr. Christophe Goeller (Humboldt Fellow, Ludwig-Maximilians-Universität München, Germany)

In this talk, I will discuss the construction of the boundary symmetry algebra for BF-like theories in 3D and 4D. In the 3D case, the theory corresponds to (an extension of) 3D gravity allowing for a source of curvature and torsion. I will show how the study of the current algebra and its associated Sugawara construction allows for two notions of quadratic charges (the usual diffeomorphism and its "dual") independently of boundary conditions. I will discuss their resulting algebra and its relation with the usual construction of the asymptotic boundary algebra. In the 4D case, a similar yet fundamentally different construction is possible, similarly resulting in multiple quadratic charges. I will discuss their constructions and their possible relations to 4D gravity.

Venue: Hybrid Format (Common Room 246-248 and Zoom)

Event Official Language: English

The Electron-Ion Collider: the Ultimate Electron Microscope

February 20 (Mon) at 15:00 - 16:30, 2023

Prof. Gordon Baym (Professor Emeritus, University of Illinois, USA)

How does the nucleon get its mass? Certainly not from the Higgs -- the rest masses of the quarks it contains add up to only one percent of the nucleon mass. Rather the remaining 99% comes from the zero-point energy of the quarks, antiquarks and gluons localized in the nucleon. How do nuclei differ from being a simple collection of nucleons? How are the gluons, for example, distributed in nuclei? Do they stick out, or are they clumped towards the center of the nucleon? Gluons, like dark matter unseen but playing the crucial role in gluing matter together, are strongly interacting. Do such gluons form new emergent quantum states in nuclei, as in condensed matter physics? And how is the spin of the proton -- the key to NMR imaging -- put together from the spin and orbital motion of the quarks and gluons in the proton?

Venue: Okochi Hall (Main Venue) / via Zoom

Event Official Language: English

Connecting the hierarchies: from cosmos to life

February 20 (Mon) at 10:00 - 16:45, 2023

Dr. Yuki Yokokura (Senior Research Scientist, iTHEMS)
Dr. Etsuko Itou (Senior Research Scientist, iTHEMS)
Prof. Catherine Beauchemin (Deputy Program Director, iTHEMS)

As each research field in modern science has matured and become more sophisticated and deepened, it has also created the problem that it has become too fragmented from the perspective of the field as a whole. On the other hand, looking at individual research themes, research that connects different hierarchical structures, such as cosmogenesis and particle theory, neutron stars and nuclear theory, large-scale structure of the universe and formation of galaxies, stars, and planets, turbulent phenomena over a wide range of scales, life and non-equilibrium phenomena, etc., is progressing, and efforts to understand physical phenomena from an integrated perspective is spreading. The term "hierarchy" can also be interpreted as a hierarchy of theories, different principles and perspectives. Therefore, in this TJR workshop, we invite relevant lecturers from external institutes to give talks focusing on how they are striving to link different hierarchies in their respective research fields, with the aim of broadening our research perspectives and inspiring future research. Of course, the purpose is also to inform and inspire the younger generation about cross-disciplinary research topics.

Venue: Nambu Hall, Toyonaka Campus, Osaka University / via Zoom

Coherent sheaves, quivers, and quantum groups

February 17 (Fri) at 14:00 - 16:00, 2023

Dr. Gufang Zhao (Senior Lecturer, University of Melbourne, Australia)

This talk aims to illustrate symmetries in geometry. The first half surveys a few examples of parametrizing coherent sheaves on a variety and how quantum groups control the symmetry of parametrization space. The second half aims to illustrate some special cases when the variety is a local toric 3-Calabi-Yau.

Venue: Hybrid Format (Common Room 246-248 and Zoom)

Event Official Language: English

String theory, N=4 SYM and Riemann hypothesis

February 16 (Thu) at 14:00 - 16:10, 2023

Dr. Masazumi Honda (Assistant Professor, Yukawa Institute for Theoretical Physics, Kyoto University)

We discuss new relations among string theory, four-dimensional N=4 supersymmetric Yang-Mills theory (SYM) and the Riemann hypothesis. It is known that the Riemann hypothesis is equivalent to an inequality for the sum of divisors function σ(n). Based on previous results in literature, we focus on the fact that σ(n) appears in a problem of counting supersymmetric states in the N=4 SYM with SU(3) gauge group: the Schur limit of the superconformal index plays a role of a generating function of σ(n). Then assuming the Riemann hypothesis gives bounds on information on the 1/8-BPS states in the N=4 SYM. The AdS/CFT correspondence further connects the Riemann hypothesis to the type IIB superstring theory on AdS5×S5. In particular, the Riemann hypothesis implies a miraculous cancellation among Kaluza-Klein modes of the supergravity multiplet and D3-branes wrapping supersymmetric cycles in the string theory. We also discuss possibilities to gain new insights on the Riemann hypothesis from the physics side. This talk is based on a collaboration with Takuya Yoda (arXiv:220317091).

Venue: Hybrid Format (Common Room 246-248 and Zoom)

Event Official Language: English

Quantum groups and cohomology theories

February 15 (Wed) at 14:00 - 16:00, 2023

Dr. Yaping Yang (Senior Lecturer, University of Melbourne, Australia)

In the first half of my talk, I will review quantum groups at roots of unity and their representation theory. In the second half, I will explain a construction of new quantum groups using cohomology theories from topology. The construction uses the so-called cohomological Hall algebra associated to a quiver and an oriented cohomology theory. In examples, we obtain the Yangian, quantum loop algebra and elliptic quantum group, when the cohomology theories are the cohomology, K-theory, and elliptic cohomology respectively.

Venue: Hybrid Format (Common Room 246-248 and Zoom)

Event Official Language: English

Kyoto Univ. MACS Program x RIKEN iTHEMS Collaborative Research Forum

February 13 (Mon) at 13:00 - 18:00, 2023

RIKEN iTHEMS and the SACRA Interdisciplinary Research Division of the Graduate School of Science, Kyoto University signed a joint research agreement on the task "Creation of new fields and solution of various problems in science using mathematical-based interdisciplinary methods", which started in 2018, and the two institutions have been strengthening collaboration over the past five years. During this period, various collaborative activities in both research and education have been carried out and results have been achieved, including the holding of research symposia, joint lectures across universities, the establishment of visiting lectures, and educational activities in the MACS Study Group. At this forum, we would like to present the results of these five years of joint research and to link them to the start of further collaboration in the future. In particular, many undergraduate and graduate students have participated in the "MACS Study Group 2022-SG5 Pipeline Connecting RIKEN and MACS", and have been actively engaged in research activities with RIKEN researchers. The results of these SG5 activities will be presented by the students.

Venue: 4F, South Tower, School of Science Bldg. No.6, Kyoto University (Main Venue) / via Zoom

Event Official Language: Japanese

Entanglement in non-Hermitian quantum systems and non-unitary conformal field theories

February 9 (Thu) at 17:00 - 18:15, 2023

Dr. Chang Po-Yao (Assistant Professor, Department of Physics, National Tsing Hua University, Taiwan)

Time: 5pm ~ 6:15pm (JST); 9am ~ 10:15am (CET); 4pm ~ 5:15pm (Taiwan) Entanglement is a powerful tool to diagnose many-body quantum systems. One example is the critical system where the low energy property can be described by conformal field theories (CFTs), and the central charge which uniquely characterizes the CFT can be perfectly extracted from the entanglement entropy. However, the entanglement properties for non-unitary CFTs are not well understood. Moreover, the entanglement properties in many-body microscopic models which can be described by non-unitary CFTs have not been explored. In this talk, I would like to demonstrate several non-Hermitian systems which can be described by non-unitary CFTs, and show their entanglement properties can be correctly obtained by the proposed generic entanglement entropy. Field: Condensed Matter Physics Keywords: non-Hermitian systems, conformal field theory, many-body systems, entanglement entropy

Venue: via Webex

Event Official Language: English

Elasticities of population growth and their significance to evolutionary biology

February 9 (Thu) at 16:00 - 17:00, 2023

Dr. Stefano Giaimo (Postdoc, Department for Evolutionary Theory, Max Planck Institute for Evolutionary Biology, Germany)

The elasticity of population growth to a demographic parameter quantifies the proportional sensitivity of population growth to such parameter. In this talk, I will illustrate some cases where elasticities of population growth to demographic parameters acquire a special importance to evolutionary biology. In particular, I will discuss the relevance of these elasticities in studying the evolution of aging, their role in the computation of the generation time and their relationship to some trade-offs organisms may face as they optimise their fitness.

Venue: via Zoom

Event Official Language: English

Boltzmann or Bogoliubov? A Case of Gravitational Particle Production

February 9 (Thu) at 13:30 - 15:00, 2023

Dr. Kunio Kaneta (Lecturer, Graduate School of Science, Tokyo Woman's Christian University)

Despite its weakness, gravity is the primordial source of particle production in the early Universe. All the particles, including dark matter, can inevitably be created after the end of inflation through gravity. To study this production channel, two different approaches have commonly been considered, one of which is based on the Boltzmann equation, and the other is based on the Bogoliubov transformation. The former approach has widely been used in phenomenological studies of dark matter, while the latter has been developed to describe particle production in curved spacetime. I will discuss when these two approaches are equivalent and when they are not by considering the pure gravitational production of a scalar particle.

Venue: Hybrid Format (Common Room 246-248 and Zoom)

Event Official Language: English