# Event Schedule

## Events for the 3rd week of July 2021

2021-07-08

Sunday, July 11, 10:00- iTHEMS Science Outreach Workshop 2021

Friday, July 16, 12:30- Coffee Meeting

# Seminar Report

## iTHEMS Math Seminar by Mr. Mizuki Oikawa on July 2, 2021

2021-07-06

On July 2 Mizuki Oikawa gave a talk at the iTHEMS math seminar. He talked about the interaction among modular functions, conformal field theories and moonshine phenomena. Below is a recap of his talk. The j-invariant is an example of modular form. Its coefficients in the q-expansion is closely related to a certain sporadic simple group (the monster group), and the relation can be understood via the theory of vertex operator algebras (VOA), which is a mathematical model of conformal field theory (CFT). This gives an example of moonshine phenomena. On the other hand, there is another mathematical framework for CFT, called the conformal net, which depends on the theory of von Neumann algebras. Carpi-Kawahigashi-Longo-Weiner gave a correspondence between a certain class of VOAs (which includes the monstrous moonshine VOA) and that of conformal nets. Recently, Tener gave a geometric realization of some VOAs and the corresponding conformal nets via Segal CFT. The talk was highly stimulating, and the audience asked many questions that arise from both mathematical and physical sides.

Reported by Michiya Mori

An introduction to modular functions, conformal field theories, and moonshine phenomena

July 2 at 16:00 - 18:10, 2021

# Seminar Report

## iTHEMS Biology Seminar by Prof. Takahiro Sakaue on July 1, 2021

2021-07-06

On July 1st, Prof. Takahiro Sakaue (Aoyama Gakuin University) gave us a talk about chromatin dynamics in C. elegans embryos. He first introduced important factors for gene expression such as phase separation, topological constraints, and chromatin dynamics. After explaining how to see the chromatin dynamics under the microscope, he showed us interesting experimental results about the dependence of MSD on the nucleus radius. By considering polymer models, he showed that two kinds of typical length/time scales appear and discussed how the type of anomalous diffusion of chromatin is determined depending on the time/length scale. Moreover, he theoretically explained the observed nucleus-size dependence of MSD. We are grateful to Sakaue-san for the exciting talk!

Reported by Kyosuke Adachi

How nucleus size affects chromatin motion? - Experimental measurements and a polymer physics theory

July 1 at 10:00 - 11:00, 2021

# Upcoming Events

## Workshop

### iTHEMS Science Outreach Workshop 2021

July 11 - 12, 2021

RIKEN iTHEMS, an interdisciplinary Theoretical and Mathematical Sciences Program (RIKEN iTHEMS), was established in November 2016. RIKEN iTHEMS aims to use interdisciplinary methods with a focus on mathematics to elucidate the universe, matter and life, and to solve fundamental problems in society. Building on the achievements of the past exchanges through the Journalist in Residence Program, we will hold an outreach workshop to explore the relevance of the research of the RIKEN iTHEMS to society and to discuss how to build interactive relationships between journalists and researchers in the future. Like last year, this year's workshop will be held as a ZOOM workshop as the seminar house is closed.

Contact: Takashi Tsuboi (iTHEMS Deputy Director)

Venue: via Zoom

Event Official Language: Japanese

## Seminar

### Overview of Tensor Networks in Machine Learning

July 28 at 13:30 - 14:50, 2021

Dr. Qibin Zhao (Team Leader, Tensor Learning Team, RIKEN Center for Advanced Intelligence Project (AIP))

Tensor Networks (TNs) are factorizations of high dimensional tensors into networks of many low-dimensional tensors, which have been studied in quantum physics, high-performance computing, and applied mathematics. In recent years, TNs have been increasingly investigated and applied to machine learning and signal processing, due to its significant advances in handling large-scale and high-dimensional problems, model compression in deep neural networks, and efficient computations for learning algorithms. This talk aims to present a broad overview of recent progress of TNs technology applied to machine learning from perspectives of basic principle and algorithms, novel approaches in unsupervised learning, tensor completion, multi-task, multi-model learning and various applications in DNN, CNN, RNN and etc. We also discuss the future research directions and new trend in this area.

Venue: via Zoom

Event Official Language: English

# Person of the Week

## Self-introduction: Etsuko Itou

2021-07-02

I'm Etsuko Itou, a Postdoctoral Researcher (Concurrent) since July 2021. I'm interested in quantum field theories, in particular, quantum chromodynamics (QCD) in extreme regimes. Although QCD in the superfluid phase, which occurs in low-temperature and high-density regimes, is still an unsolved area due to the infamous sign problem, a theoretical understanding is urgently needed in relation to neutron star physics. I am working on various numerical approaches to understanding quantum field theories with the sign problem. For example, I utilize the conventional classical supercomputers to study qualitative properties of modified QCD without the sign problem, and I develop quantum computation algorithms based on a new formula where the sign problem does not emerge.

# Paper of the Week

## Week 2, July 2021

2021-07-08

Title: The maximal negative ion of molecules in Schrödinger, Hartree-Fock, and Müller theories

Author: Yukimi Goto

arXiv: http://arxiv.org/abs/2107.01826v2

Title: Positivity vs. Lorentz-violation: an explicit example

Author: Katsuki Aoki, Shinji Mukohyama, Ryo Namba

arXiv: http://arxiv.org/abs/2107.01755v1

Title: Effects of finite-light-speed correction for the Coulomb interaction on nuclear binding energies and radii in spherical nuclei

Author: Tomoya Naito

arXiv: http://arxiv.org/abs/2106.14270v1

Title: Goldstone Boson Scattering with a Light Composite Scalar

Author: T. Appelquist, R. C. Brower, K. K. Cushman, G. T. Fleming, A. Gasbarro, A. Hasenfratz, J. Ingoldby, X. Y. Jin, J. Kiskis, E. T. Neil, J. C. Osborn, C. Rebbi, E. Rinaldi, D. Schaich, P. Vranas, E. Weinberg, O. Witzel

arXiv: http://arxiv.org/abs/2106.13534v1

Title: Quantum hydrodynamics from local thermal pure states

Author: Shoichiro Tsutsui, Masaru Hongo, Shintaro Sato, Takahiro Sagawa

arXiv: http://arxiv.org/abs/2106.12777v2

Title: Modulus sheaves with transfers

Author: Shane Kelly, Hiroyasu Miyazaki

arXiv: http://arxiv.org/abs/2106.12837v1

Title: Unitary $p$-wave Fermi gas in one dimension

Author: Hiroyuki Tajima, Shoichiro Tsutsui, Takahiro M. Doi, Kei Iida

arXiv: http://arxiv.org/abs/2106.12909v1

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