# Event Schedule

## Events for the 2nd week of December 2021

2021-12-02

Wednesday, December 8, 16:00– 18:00 iTHEMS Math Seminar

Thursday, December 9, 10:00– 11:00 iTHEMS Biology Seminar

Friday, December 10, 12:30- Coffee Meeting

# Seminar Report

## iTHEMS Biology Seminar by Prof. Catherine Beauchemin on October 14, 2021

2021-11-30

Defective interfering virus particles (DIPs) are viruses that are defective in a very specific way that allows them to out-compete standard, non-defective virus. It is difficult to count DIPs because they can look too similar to standard virus. So instead, people are counting them based on their effect on suppressing the standard virus population. In this talk, C. Beauchemin explained the basic biology of virus replication, what are DIPs, and how they compete with standard virus. She presented her group's mathematical model (ordinary differential equation) that describes co-infection competition with DIPs and standard virus. She also showed applications of the mathematical model to show how experiments to count DIPs can give incorrect results, and proposed some solutions.

Understanding the effect of defective, interfering influenza virus

October 14 at 10:00 - 11:00, 2021

# Seminar Report

## ABBL/iTHEMS Astro Seminar by Dr. Hirotaka Yoshino on November 12, 2021

2021-12-01

Dr. Yoshino gave us a talk on his recent work on axions around rotating black holes. He showed results of his numerical simulations of so-called “superradiant instability” in which an axion field around a rotating black hole extracts the energy of the black hole. These results suggest that every astrophysical black hole is expected to wear a cloud of the axion.

Reported by Akira Mizuta (ABBL, RIKEN)

Axions around rotating black holes

November 12 at 14:00 - 16:00, 2021

# Seminar Report

## Quantum Matter SG seminar by Prof. Harshman Nathan on November 17, 2021

2021-11-30

From American University, Prof. Nathan Harshman gave a seminar talk about topological exchange statistics in one spatial dimension on Nov. 17th, 2021. To introduce exchange statistics as done in the literature, he started with statistics for bosons and fermions and extended fractional and non-abelian exchange statistics. Then, the speaker raised questions about particle exchange in 1D and the collisions of the particles. Can a collision and an exchange at all be distinguished in one dimension? Is it reasonable to include points of coincidence in the configuration space? The way to resolve these problems is to introduce orbifolds. After pedagogically explaining the concepts of the orbifolds, he began to use the orbifold topological approach to study exchange statistics for any dimension. This approach offers great chances for novel abelian and nonabelian anyons in effectively 1D cold atom and condensed matter systems.

Reported by Thore Posske (University of Hamburg, Germany) and Ching-Kai Chiu

# Seminar Report

## Information Theory SG Seminar by Dr. Enrico Rinaldi on November 29, 2021

2021-11-30

In the first part, he introduced the concept of simulation-based inference (SBI), which is inference methods driven by machine learning, and show some examples. In the later part, he showed some preliminary results of SBI on a biological neural circuit. We had a great discussion during Enrico’s talk. Thanks again for the fantastic talk, Enrico! We look forward to working with you.

Reported by Akinori Tanaka

Simulation-based inference for multi-type cortical circuits

November 29 at 13:30 - 15:00, 2021

# Upcoming Events

## Seminar

### The Conley index of topological dynamical systems

December 3 at 16:00 - 18:00, 2021

Prof. Yosuke Morita (Assistant Professor, Department of Mathematics, Kyoto University)

The study of topological dynamical systems, i.e. continuous self-homeomorphisms (or continuous flows) on topological spaces, is important in both pure mathematics and applications. To each isolated invariant subset of a topological dynamical system, we can assign an invariant called the Conley index, which is (roughly speaking) a based space that describes the dynamics around the isolated invariant subset. It is used not only in the study of topological dynamical systems themselves but also in Manolescu’s construction of the Seiberg-Witten-Floer homotopy type (a spectrum-valued (3+1)-dimensional TQFT). In this talk, I am planning to explain a new construction of Conley indices, which is entirely non-homotopical and uses only basic general topology.

*Please contact Keita Mikami or Hiroyasu Miyazaki's mailing address to get access to the Zoom meeting room.

Venue: via Zoom

Event Official Language: English

## Seminar

### Generalized Bernoulli process and computation of proportional areas for Venn diagram

December 8 at 16:00 - 18:00, 2021

Dr. Ryosuke Iritani (Research Scientist, iTHEMS)

*For detailed information about the seminar, please refer to the email.

Venue: via Zoom

Event Official Language: English

## Seminar

### Selective inference for testing trees and edges in hierarchical clustering and phylogeny

December 9 at 10:00 - 11:00, 2021

Prof. Hidetoshi Shimodaira (Professor, Graduate School of Informatics, Kyoto University / Team Leader, Mathematical Statistics Team, RIKEN Center for Advanced Intelligence Project (AIP))

Bootstrap resampling is quite useful for computing “confidence values” or “p-values” of trees and edges. However, they are biased and may lead to false positives (too many wrong discoveries) or false negatives (too few correct discoveries) depending on the “curvature” of the boundary surface of a hypothesis region in the data space. In addition, we face the issue of selection bias because we tend to use the dataset twice for hypothesis selection and its evaluation. I will explain these two types of bias and show methods to adjust the confidence values.

Venue: via Zoom

Event Official Language: English

## Seminar

### The FASER experiment

December 15 at 17:00 - 18:00, 2021

Prof. Hidetoshi Otono (Assistant Professor, Research Center for Advanced Particle Physics, Kyushu University)

FASER, the ForwArd Search ExpeRiment, is an experiment dedicated to searching for light, extremely weakly-interacting particles at the LHC. Such particles may be produced in the LHC’s high-energy collisions and then decay to visible particles in FASER, which is placed 480 m downstream of the ATLAS interaction point. FASER, also includes a sub-detector, FASER$\nu$, designed to detect neutrino’s produced in the LHC collisions and to study their properties. This seminar will describe the physics motivations, detector design, expected performance of FASER, and current status, as well as the physics prospects.

Venue: via Zoom

Event Official Language: English

# Paper of the Week

## Week 1, December 2021

2021-12-02

Title: Flavor number dependence of QCD at finite density by the complex Langevin method

Author: Yusuke Namekawa, Yuhma Asano, Yuta Ito, Takashi Kaneko, Hideo Matsufuru, Jun Nishimura, Asato Tsuchiya, Shoichiro Tsutsui, Takeru Yokota

arXiv: http://arxiv.org/abs/2112.00150v1

Title: Emergence of the rho resonance from the HAL QCD potential

Author: Yutaro Akahoshi, Sinya Aoki, Takumi Doi

arXiv: http://arxiv.org/abs/2111.15138v1

Title: Color superconductivity in a small box: a complex Langevin study

Author: Shoichiro Tsutsui, Yuhma Asano, Yuta Ito, Hideo Matsufuru, Yusuke Namekawa, Jun Nishimura, Asato Tsuchiya, Takeru Yokota

arXiv: http://arxiv.org/abs/2111.15095v1

Title: Perturbative predictions for color superconductivity on the lattice

Author: Takeru Yokota, Yuhma Asano, Yuta Ito, Hideo Matsufuru, Yusuke Namekawa, Jun Nishimura, Asato Tsuchiya, Shoichiro Tsutsui

arXiv: http://arxiv.org/abs/2111.14578v1

Title: QHC21 equation of state of neutron star matter -- in light of 2021 NICER data

Author: Toru Kojo, Gordon Baym, Tetsuo Hatsuda

arXiv: http://arxiv.org/abs/2111.11919v1

Title: Flux tube profiles in two-color QCD at low temperature and high density

Author: Katsuya Ishiguro, Kei Iida, Etsuko Itou

arXiv: http://arxiv.org/abs/2111.13067v1

# Person of the Week

## Self-introduction:Tomoki Nosaka

2021-11-29

My name is Tomoki Nosaka. I have joined RIKEN iTHEMS as a research part-time worker in November 2021. My research field is the theoretical physics. I have been trying to reveal new aspects of M-theory, which is supposed to be the theory of everything though still being mysterious, by means of the supersymmetric gauge theories, matrix models and their integrability. Recently I am also interested in the quantum information theory and the various notions of chaos in quantum many-body systems which are found to be closely related to the black hole physics. I am looking forward to interacting with people in iTHEMS working with various research interests and finding a new direction of research out of it.

If you would like to cancel your subscription or change your email address,

please let us know via our contact form.