# News

185 news in 2020

2020-12-24

## Information Theory SG by Dr. Yukimi Goto on December 23, 2020

This week, Dr. Yukimi Goto gave us an introduction to the Lieb-Robinson bound. After reviewing several important preliminaries, such as Liouvillians for open quantum systems, she discussed the Lieb-Robinson bound, which is a theorem for the bound on speed of information propagation. She then explained two notable applications of the bound, i.e., correlation decay and the entanglement area law for a gapped ground state in isolated quantum systems. We thank Goto-san for her great talk!

2020-12-23

## Biology Seminar by Dr. Shingo Iwami on December 22, 2020

In his seminar Dr. Iwami (Kyushu University) presented his mathematical model for coronavirus (新型コロナウイルス) in patients. The aim of the project was to determine why some papers disagreed on the efficacy of certain antiviral drugs to treat the coronavirus. Because the available data was limited, only a simple mathematical model was considered. The mathematical model only represents the fraction of cells remaining to be infected and the amount of virus. The curve for the virus in the model was fitted to the data of virus in the nasal swab of patients. From this analysis, Dr. Iwami's group could separate the patients into 3 types: with either slow, medium or fast decay of virus. He showed that in his model, only early treatment can be effective for all decay types. This can be one reason why two different clinical trials can find different results: if one trial includes late treatment then it can appear that the treatment is not effective. From the mathematical model, he suggested some changes in the criteria for patient inclusion into clinical trials to improve the ability to detect statistically significant effects for the antiviral drug. The seminar was very well attended, with many questions and discussions. Thank you Dr. Iwami for your great talk! - Catherine Beauchemin (iTHEMS)

2020-12-18

## Biology Seminar by Akane Hara on December 17, 2020

In today's biology seminar, we invited Akane Hara, a PhD student at Kyushu University, to have her talk about how pathogen infection can cause autoimmune diseases. Normally, the immune systems attack germs like viruses and bacteria to prevent their growth within the body. However, these germs may mimic themselves to our body system so that they can avoid the attack. As a result, the immune system is not able to tell the germs from our body parts, and so even after the removal of the germs, it harms our body mistakenly. Wondering why - or when - this is the case, she considered ordinary differential equations of the compartment models for virus, helper cells, and memory T cells, by explicitly considering cross immunity. She presented a mathematical condition for which autoimmune diseases may be present and/or severe. We discussed possible extensions of the mathematical models. Thank you so much for the great talk, Akane! Personally, I was a colleague with her at Kyushu University and so feel a bit emotional that she's completing her PhD very soon! -Ryosuke Iritani

2020-12-18

## iTHEMS-phys seminar by Takeru Yokota on December 17, 2020

On December 17, the iTHEMS-phys seminar entitled "Classical liquids and functional renormalization group" given by Dr. Takeru Yokota (ISSP, U. Tokyo) was held. He has been working for the functional-renormalization-group-aided density functional theory (FRG-DFT) for several years. Recently, he is applying this method to classical liquid. As a benchmark calculation, he applied to a one-dimensional exactly solvable system. The exact solution was sucessfully reproduced by the method. The seminar was held via the Zoom online conference systems. More than 20 people, including outside from iTHEMS, attended the seminar. The discussion was quite lively, and it was continued several hours even after the seminar.

2020-12-18

## Math-Phys Joint Seminar by Dr. Naotaka Kubo on December 14, 2020

His talk was on the test of non-perturbative dynamics of three-dimensional gauge theories from the perspective of brane dynamics in string theory. In the first half of his talk, he explained important ideas in quantum field theory at an elementary level, such as renormalization group (RG) flow, supersymmetry (SUSY), and world-volume theory on branes in string/M-theory. Combining these fundamental ideas, he moved on to the discussion of duality cascades in quantum gauge theories in four and three dimensions. Using branes in string theory, he demonstrated that the duality cascades in M2-brane world-volume theories can be understood from the brane dynamics in type IIB string theory, which is the so-called Hanany-Witten move/transition. In particular, he mentioned that after the sequence of the Hanany-Witten transitions, one may predict if the original gauge theories have SUSY breaking under the RG flow. Then he concluded that all the world-volume theories related by the Hanany-Witten transitions would flow to the same IR theory, and SUSY will be broken if anti-D3-branes are created. In the latter part of the talk, he argued the non-perturbative tests of duality cascades in three-dimensional supersymmetric gauge theories using partition functions of the theories. He first introduced the notion of partition functions of quantum field theories on S^3 and rephrased the conclusion given in the first part in the language of partition function. He then illustrated the general idea to exactly compute the partition function of supersymmetric gauge theories, which is an analogue of Duistermaat-Heckman formula and is called supersymmetric localization. He gave a dictionary between the viewpoint of brane configuration and the partition function of supersymmetric gauge theories. With such a dictionary, the Hanany-Witten transition of branes was rewritten by an equality between the partition functions. Moreover, one can directly check the duality cascades and SUSY breaking by calculating the partition functions. Finally, he showed the duality cascades and SUSY breaking in supersymmetric gauge theories by an explicit evaluation of partition functions, with comments on Fermi gas formalism and residue computation.

2020-12-17

## Week 3 of December

Title: Phase transitions in the frustrated Ising ladder with stoquastic and non-stoquastic catalysts Author: Kabuki Takada, Shigetoshi Sota, Seiji Yunoki, Bibek Pokharel, Hidetoshi Nishimori, Daniel A. Lidar arXiv: http://arxiv.org/abs/2012.07144v1

2020-12-17

## Biology Seminar by Dr. Yuri Kominami on November 27, 2020

In iTHEMS Biology Seminar on November 27th, Dr. Yuri Kominami from University of Tokyo gave us a talk about her experimental study on population dynamics of rotifer. It is often difficult to understand population dynamics of animals because the population is reflected by complex environmental conditions. In her study, by using rotifer as a model organism, she has succeeded in measuring the laboratory population size, the birth rate, and the life span in a controlled condition. In this seminar, she showed some of nontrivial results of her experiment. Her discoveries were very exciting for theoretical biologists, and we enjoyed active discussion. Thank you so much, Kominami-san! -Shingo Gibo

2020-12-16

## Information Theory SG by Dr. Ryusuke Hamazaki on December 16, 2020

In the journal club of Information Theory Study Group held on December 16th, Dr. Ryusuke Hamazaki (CPR/iTHEMS) gave us a talk about recent proposals of a quantum version of the Wasserstein distance. He first reviewed the commonly used quantities expressing the distance between probability distributions, i.e., the total variation distance and the relative entropy. After pointing out certain problems with these quantities, he introduced the classical Wasserstein distance of order 1 as a better definition of the distance and explained its representative properties like transportation inequality and tensorization property. Next, he introduced a quantum counterpart of the Wasserstein distance, which can apply to spin-1/2 quantum systems. In contrast to the total variation distance, the quantum Wasserstein distance has interesting properties like the invariance under permutation or local unitary transformation. Lastly, he explained an application of the quantum version of transportation inequality to the eigenvalue distribution. Reflecting the interdisciplinary subject of the talk, there were several questions and comments from both mathematical and physical viewpoints. We are grateful to Ryusuke for the great talk! Kyosuke Adachi (BDR/iTHEMS)

2020-12-16

## Information Theory SG by Dr. Koichiro Yoshino on December 16, 2020

As the first seminar speaker of the Information Theory study group, we invited Koichiro Yoshino (Teamleader of Robotics Project, RIKEN) to give a talk on natural language processing. First, he explained the statistical language model's basis, e.g. language model, distributed representations, etc, and then discussed his own works: 1) attribute transfer in word embedding space, 2) modeling sentence structure. Natural language processing is one of the good applicants of information theory, and we enjoyed his clear talk and discussions. Akinori Tanaka (iTHEMS/AIP)

2020-12-15

## Math Seminar by Dr. Hideki Inoue on December 7, 2020

On December 7, there was a math seminar by Dr. Hideki Inoue. His talk aims to introduce Levinson's Theorem and its recent progress. In the first part, he gave a brief survey talk on Levinson's theorem and its formulation. He then explained that Levinson's theorem, which can be proved analytically. He then introduced abstract scattering theory and operator algebras and how they applied to Levinson's theorem study. In the second part, he explained his recent results on Levinson's theorem. He showed a straightforward representation formula of the wave operator, a significant research target in the scattering theory. With this formula, he proved that one could prove Levinson's theorem by abstract theory. He also explained similar results on discrete operators.

2020-12-14

## Season's Greetings from Dr. Tetsuo Hatsuda, iTHEMS Director

Season's Greetings and Best Wishes for the New Year Thank you very much for sharing the joys of excellent science as well as your patience under COVID-19 during 2020. We wish you a good holiday season and a safe new year 2021 with happiness, prosperity, and novel scientific perspectives. Tetsuo Hatsuda, iTHEMS Director

2020-12-11

## "Do you really know what the black hole is?" was held on December 6, 2020

The academist event "Do you really know what the black hole is?" was held on December 6 via YouTube, and iTHEMS members Shigehiro Nagataki (Deputy Program Director), Yoshiyuki Inoue (Senior Visiting Scientist), and Yuki Yokokura (Senior Research Scientist) gave an easy-to-understand explanation of how black holes are born, how to search for black holes, and the inner workings of black holes, mentioning the achievements of the 2020 Nobel Prize in Physics. Please check out the video from RELATED LINKS below.

2020-12-10

## Week 2 of December

Title: Universality of active and passive phase separation in a lattice model Author: Kyosuke Adachi, Kyogo Kawaguchi arXiv: http://arxiv.org/abs/2012.02517v1 Title: Variational optimization of quantum annealing schedule for the Lechner-Hauke-Zoller scheme Author: Yuki Susa, Hidetoshi Nishimori arXiv: http://arxiv.org/abs/2012.01694v1 Title: Systematic Study of Acceleration Efficiency in Young Supernova Remnants with Nonthermal X-ray Observations Author: Naomi Tsuji, Yasunobu Uchiyama, Dmitry Khangulyan, Felix Aharonian arXiv: http://arxiv.org/abs/2012.01047v1

2020-12-10

## Biology Seminar by Dr. Euki Yazaki on December 10, 2020

In iTHEMS Biology Seminar on December 10th, Dr. Euki Yazaki (iTHEMS) talked about recent techniques and problems in obtaining the large-scale sequence data of eukaryotes. He first mentioned the importance of identifying and comparing the genome sequence in biology. Then, he illustrated the two representative sequencing methods, Sanger sequencing and next-generation sequencing (NGS). He clearly explained the features of these methods, highlighting the advantages of NGS in exploring large-scale or novel sequences. In the latter part, he introduced a method using the graph theory to reconstruct the large-scale genome data from the fragments of a sequence obtained by NGS. He lastly pointed out some problems in the current reconstruction method, and we discussed possible ideas to mitigate them after the talk. We are grateful to Euki for the stimulating talk! Kyosuke Adachi (BDR/iTHEMS)

2020-12-09

## Math Seminar by Dr. Tianfeng Hou on November 13, 2020

On November 13, Tianfeng Hou, a new member of the team, gave a math seminar on the Monte Carlo study. In the first part, the speaker focuses on quasi-Monte Carlo method and its probabilistic assessments. In the second part, the speaker explained reduced-order models and how they work in the hygrothermal model. He first showed his model works efficiently in the linear scenario. On the other hand, he explained that his model is not so efficient in some nonlinear scenario.

2020-12-09

## RIKEN iTHEMS Launches "Useless Prototyping Studio" Project to Inspire the Human Mind with Seemingly Useless Prototypes

RIKEN iTHEMS Launches "Useless Prototyping Studio" Project to inspire the human mind with seemingly useless prototypes. The prototypes based on the theories/hypotheses of scientists embody the potential to transform the future. The first trailer "Can the black hole be an information storage in the future?" on the teaser site Published today. RIKEN iTHEMS will launch the "Useless Prototyping Studio", a project to inspire the human mind with seemingly useless prototypes on Wednesday, December 9. We also publish a project overview and a preview of the first prototype "Can the black hole be an information storage in the future?" on the teaser site, which is available on the same day. Project Overview "Useless Prototyping Studio" is a design studio that aims to create new relationships between science and the society by creating prototypes that look useless at first glance but inspire the human mind. Based on scientific theories/hypotheses derived from the "curiosity for the unknown" of scientists, we imagine the possibility of these theories/hypotheses to change the future, and visualize the potential of science for the future by materializing the prototypes. The studio will be led by RIKEN iTHEMS, with the creative boutiques "SCHEMA" and "addict" as initial partners. As the project progresses, the number of partners and participating members will be expanded. - Overview of "Useless Prototyping Studio" - [Name] Useless Prototyping Studio [URL] https://uselessprototyping.jp [Launch date] December 9, 2020 (Wednesday) to launch the teaser site [Theme] The theme of the first prototype: "What's inside the black hole?" [Prototype first announced] Scheduled for early March 2021 [Project Participation Members] RIKEN iTHEMS SCHEMA addict

2020-12-08

## Information Theory SG by Dr. Akinori Tanaka on December 8, 2020 (Continuation of last week)

Continued from last week, Dr. Akinori Tanaka (Senior Research Scientist of iTHEMS and AIP) gave us a talk about the connection between the thermodynamic law and the algorithms of deep learning. He first reviewed the second law of thermodynamics in Langevin systems and the representation of stochastic gradient descent algorithms using Gaussian fluctuation. He then explained about Generative Adversarial Networks (GAN), which can be used in producing near realistic fake images. Based on mathematical correspondence, he discussed a possible application of the modified thermodynamic law to the algorithms of GAN. We are thankful to him for the exciting talk! Kyosuke Adachi (BDR/iTHEMS)

2020-12-07

## First Information Theory SG by Dr. Akinori Tanaka on December 1, 2020

Kicking off the study group of information theory, Akinori Tanaka (Senior Research Scientist of iTHEMS and AIP) talked about the connection between Langevin equation and deep neural networks. He first showed that by analyzing Langevin equations one can derive the second law of thermodynamics which posits that the total entropy of the system should increase. He then delved into stochastic gradient descent (SDG) and showed how to apply it to train the neural network in general. We discussed too enthusiastically for him to finish his talk, and so we'll organize the second part next week (08 December 2020). We are all looking forward to discussing more, and thank you so much for the elegant talk! -Ryosuke Iritani (iTHEMS)

2020-12-07

## Math Seminar by Dr. Martin Skrodzki on November 30, 2020

Our colleague Martin Skrodzki gave a farewell-talk in iTHEMS Math seminar on November 30. The title of the talk was “Flat and spherical surface approximations”. He talked about two approaches to approximate surfaces by using flat objects and spherical objects. In the first part, he explained the approximation using flat objects. Naively, there are two approaches to approximate surfaces. One is local and the other is global. In local approach, we need to get extremely many samples. In global approach, it will produce extreme torsion of surfaces. To remedy these problems, we should think of medium approach, i.e., patching of small simple flat objects (like covering of manifolds). This is called Variational Shape Approximation (VSA). The VSA has three steps: seeding, flooding and updating (and we iterate these recursively). This method gives us a very nice approximation of surfaces, but it still has some defects. Indeed, The recursive process does not always converge, the result depends on initial random choice of seeding, and it also depends on the artificial choice of the number of proxies we use. Therefore, Martin and his collaborators refined the VSA, by adding new steps called “splitting”, “Merging” and “Switching”. These steps avoids all defects above. In the second part, he explained his project on approximating surfaces using spheres. He shows some extreme examples of surfaces which are not relevant for spherical approximation: cone and toilet paper. If you imagine a needle-shaped cone, then its intersection with a ball will be very small. On the other hand, if you thing of rolled paper, then its intersection with a ball have too large area. However, if the surface we want to approximate satisfies a relevant condition, we can obtain a condition on the radius of the ball we use to approximate the surface. During the lecture, he proposed an interesting question on the maximum/minimal area of the intersection of the ball and the surface, and there was an exciting discussion including the audience.

2020-12-07

## DMWG seinar by Dr. Naka: Directional Direct Detection Experiments

Among the kinds of dark matter (DM) candidates, Weakly Interacting Massive Particle (WIMP) shows a strong model motivation. It achieves the current DM density naturally via the so-called thermal freeze-out mechanism. The strength of the interaction between WIMP and the standard model particles should be finite, and various direct detection experiments have already excluded a large part of the favored parameter space. We are now in the phase to consider the next strategy. There are several directions to proceed. For example, annual and/or diurnal modulation of the event rate of the DM-nucleon scattering. However, the expected modulation amplitude is so small that a few percent for annual modulation and less than 1% for the diurnal case. Kinds of on-going experiments intensively search the modulation signature now, however, it is still difficult to confirm. Another possibility is to make use of directional information. One important advantage of the directional search is its power for background rejection. The DM signal should be more frequently found in the direction corresponding to the Galactic Center while the backgrounds are in different directional distributions. These differences enable us to reduce the number of scattering events required for claiming the detection from O(1e4) to O(100), compared to the conventional direct detection cases. Furthermore, it could potentially provide us with information about the velocity distribution function, of which precise understanding is a key to any kinds of direct detection experiments, as well as the scenarios explaining the evolution of our Galaxy. Hence, the directional search is an attractive idea to probe the nature of DM. Recently, such projects are launched, and still some technical issues to solve remain. We have to achieve the O(1e-9)m scale resolution of the particle track, to confirm the scalability and stability, and to understand the ultra-low background. Many projects are now tackling these problems. The new era for direct DM search now begins!

2020-12-03

## Week 1 of December

Title: Consistent description for cluster dynamics and single-particle correlation Author: Naoyuki Itagaki, Tomoya Naito arXiv: http://arxiv.org/abs/2011.12642v1

2020-12-03

## Farewell message from Dr. Martin Skrodzki

When my scholarship program first notified me that I would be able to spend a year, working in the RIKEN iTHEMS program, I was extremely happy for this great interdisciplinary and intercultural opportunity. Now, this year has ended and I will return to Germany to continue my research there and possibly at other locations in Europe. I arrived at RIKEN iTHEMS on January 20. While I expected the year to be very exciting, I did not at all imagine what 2020 had in store for all of us. After my first talk in the math seminar, we went to an Izakaya and had a Nomikai there. From the current perspective, this appears quite unreal to me. The Covid-19 pandemic caused this year to be run quite different from any other year. We all had to get used to working from home, working online, and even enjoying each other’s company during online coffee as well as online parties. Despite these restrictions, I tremendously enjoyed my stay in Wako and in Japan in general. Several aspects at iTHEMS contribute to a very friendly and positive atmosphere in the program. For instance, the coffee afternoons were a great way throughout my first couple of weeks to get to know many members of the workgroup. Also the all-hands coffee meetings on Friday are a great installment to stay in touch with each other. Furthermore, the dedicated math seminars were great for me to get new input, learn new mathematics, and chat with the colleagues. The organizers of the math seminar, but also all other chairs and the speakers, made the seminars very enjoyable events. Aside from these events, I was very happy to pursue my own research projects. As I am in the first phase of my postdoctoral career, this was a great opportunity to sharpen my research foci. Thus, I would like to close by thanking everyone for making my stay at RIKEN iTHEMS as enjoyable as it was. Once the global situation has settled down, I would love to return for a short visit or even another extended research stay. Let’s stay in touch!

2020-11-30

## Biology Seminar by Dr. Hidenori Tanaka on November 20, 2020

In iTHEMS Biology Seminar on November 20th, Dr. Hidenori Tanaka (Physics & Informatics Laboratories, NTT Research) gave us an exciting talk about physics principles in neural networks. He first reviewed the basic scheme of deep learning using neural networks. Then, he presented three questions regarding both neural science and machine learning and explained his recent works which address these questions. He stressed how physics principles like symmetry and conservation laws are useful in extracting minimal features of biological circuit models, improving algorithms to simplify neural networks, and predicting learning dynamics of neural networks. As his talk was clear and kind to both specialists and non-specialists, there were various questions from the audience. Hidenori is a very active researcher, and I was happy to invite him as a guest speaker. Kyosuke Adachi (BDR/iTHEMS)

2020-11-26

## Week 4 of November

Title: Motives with modulus, III: The categories of motives Author: Bruno Kahn, Hiroyasu Miyazaki, Shuji Saito, Takao Yamazaki arXiv: http://arxiv.org/abs/2011.11859v1 Title: Scale setting the M{ö}bius Domain Wall Fermion on gradient-flowed HISQ action using the omega baryon mass and the gradient-flow scale w0 Author: Nolan Miller, Logan C Carpenter, Evan Berkowitz, Chia Cheng Chang, Ben Hörz, Dean Howarth, Henry Monge-Camacho, Enrico Rinaldi, David A. Brantley, Christopher Körber, Chris Bouchard, M. A. Clark, Arjun Singh Gambhir, Christopher J. Monahan, Amy Nicholson, Pavlos Vranas, André Walker-Loud arXiv: http://arxiv.org/abs/2011.12166v1 Title: The Julia Line of a Riemann-Type Functional Equation {\footnotesize -- Counting Formulae, Dirichlet Polynomial Approximations, and a Weak Gram Law --} Author: Athanasios Sourmelidis, Jörn Steuding, Ade Irma Suriajaya arXiv: http://arxiv.org/abs/2011.10692v1 Title: Thermalization of Yang-Mills theory in a (3+1) dimensional small lattice system Author: Tomoya Hayata, Yoshimasa Hidaka arXiv: http://arxiv.org/abs/2011.09814v1 Title: Replica wormholes for an evaporating 2D black hole Author: Kanato Goto, Thomas Hartman, Amirhossein Tajdini arXiv: http://arxiv.org/abs/2011.09043v1

2020-11-26

## Dr. Euki Yazaki received "2020 The Encouragement Award for Young Protistologists"

It is our great pleasure to inform you that our iTHEMS colleague, Euki Yazaki received "2020 The Encouragement Award for Young Protistologists" (日本原生生物学会奨励賞) from "Japan Society of Protistology (日本原生生物学会) for "Revealing of the evolution and diversity of eukaryotes through large-scale sequence data analyses" (大規模配列データ解析による真核生物の進化・多様性の解明). The award ceremony was held at Japan Society of Protistology Meeting on Nov.22-23, 2020. Many congratulations, Euki !

2020-11-24

## Math Seminar by Dr. Takahiro Kitayama on November 16, 2020

On November 16, professor Takahiro Kitayama from University of Tokyo gave a talk entitled “Representations of fundamental groups and 3-manifold topology” at the iTHEMS math seminar. In the first part, he introduced a central motivation of 3-manifold topology: classify all 3-manifolds up to diffeomorphisms. As one of the important tools, he introduced the fundamental groups of spaces. He reviewed several known results of the fundamental groups of manifolds. Next, he focused on essential surfaces and introduced Haken 3-manifolds as an important class of 3-manifolds. In particular, he introduced several examples of Haken and non-Haken manifolds. At the end of the first talk, he explained SL(2,C)-representation spaces (character varieties) of the fundamental groups of 3-manifolds. He mentioned that the representation space has been used as a fundamental tool to classify knots and 3-manifolds. In the second part, he first mentioned Culler-Shalen, Morgan-Shalen’s theorem which says that an ideal point of the SL(2,C)-character variety of a given 3-manifold M gives an essential surface of M. Friedl, Hara, Kitayama, and Nagel developed C-S and M-S’s theory for the Lie group SL(n,C). He explained the main idea to obtain all essential surfaces from ideal points of SL(n,C)-character variety. In particular, he introduced the tautological representation depending on some affine curve of the SL(2,C)-character variety, and an action of the fundamental group on some contractible simplicial complex called the Bruhat-Tits building. Then by a standard argument of topology, he constructed some simplicial map f from the universal covering space of a given 3-manifold to the Bruhat-Tits building. By taking the inverse image of f(after ignoring trivial parts and dividing by the fundamental group of the 3-manifold), he finally constructed an essential surface. Next, he also told us about a relation between (homotopy types of) boundary loops of essential surfaces of knot complements and slopes of sides of the Newton polygon obtained from A-polynomials. He said an essential idea of the result, which can detect whether the boundary of an essential surface obtained from an ideal point is boundary parallel or not. At the end of the second talk, as the leading coefficients of torsion functions, he gave a function c_{M, ψ} on the SL(n, C)-character variety. After explaining Dunfield-Friedl-Jackson’s conjecture, he gave a partial solution of the conjecture which is related to the finiteness of c_{M, ψ} on the ideal points.

2020-11-19

## Week 3 of November

Title: Classification of Magnetic Vortices by Angular Momentum Conservation Author: Kenji Fukushima, Yoshimasa Hidaka, Ho-Ung Yee arXiv: http://arxiv.org/abs/2011.06981v1 Title: Variational Shape Approximation of Point Set Surfaces Author: Martin Skrodzki, Eric Zimmermann, Konrad Polthier arXiv: https://arxiv.org/abs/2005.01003v2 Title: Firewall From Effective Field Theory Author: Pei-Ming Ho, Yuki Yokokura arXiv: https://arxiv.org/abs/2004.04956v3 Title: Parity of the neutron consistent with neutron-antineutron oscillations Author: Kazuo Fujikawa, Anca Tureanu arXiv: https://arxiv.org/abs/2009.12843v2 Title: Distance between collapsing matter and trapping horizon in evaporating black holes Author: Pei-Ming Ho, Yoshinori Matsuo, Yuki Yokokura arXiv: https://arxiv.org/abs/1912.12863v3 Title: Test of Eigenstate Thermalization Hypothesis Based on Local Random Matrix Theory Author: Shoki Sugimoto, Ryusuke Hamazaki, Masahito Ueda arXiv: https://arxiv.org/abs/2005.06379v3 Title: Liouvillian Skin Effect: Slowing Down of Relaxation Processes without Gap Closing Author: Taiki Haga, Masaya Nakagawa, Ryusuke Hamazaki, Masahito Ueda arXiv: https://arxiv.org/abs/2005.00824v2 Title: Relativistic density functional theory with finite-light-speed correction for the Coulomb interaction: a non-relativistic-reduction based approach Author: Tomoya Naito, Ryosuke Akashi, Haozhao Liang, Shinji Tsuneyuki arXiv: https://arxiv.org/abs/1911.10670v2 Title: Griffiths-McCoy singularity on the diluted Chimera graph: Monte Carlo simulations and experiments on the quantum hardware Author: Kohji Nishimura, Hidetoshi Nishimori, Helmut G. Katzgraber arXiv: https://arxiv.org/abs/2006.16219v2 Title: Absence of fast scrambling in thermodynamically stable long-range interacting systems Author: Tomotaka Kuwahara, Keiji Saito arXiv: https://arxiv.org/abs/2009.10124v2

2020-11-19

## The longest "rulers" in the universe -- Gamma-Ray Bursts associated with Kilonovae are the new standard candles

An international collaborative research group led by Maria Dinotti (Senior Research Scientist, iTHEMS) and Shigehiko Nagataki (Deputy Program Director, iTHEMS) has discovered that gamma-ray bursts (GRBs), which occur simultaneously with kilonovae, are effective as standard candles for measuring the distance of the universe. The results of this research show the potential to make use of GRBs for cosmology in the near future, to estimate the amount of dark energy and dark matter in the universe.

2020-11-16

## Math-Phys joint Seminar by Dr. Naoto Shiraishi on November 10, 2020

On November 10, Dr. Naoto Shiraishi from Gakushuin University gave a talk entitled “Mathematics of thermalization in isolated quantum systems” at the iTHEMS Math-Phys joint seminar. In the first part, he reviewed some results and problems of quantum thermalization. Besides, he explained the typicality of equilibrium states, the relaxation caused by large effective dimensions, and the weak/strong eigenstate thermalization hypothesis mathematically. In the second part, the speaker discussed the difficulty of the thermalization problems and some of his results. Mainly, he showed the absence of local conserved quantities in the S=1/2 XYZ chain with a magnetic field. The talk had many participants from in and out iTHEMS and many stimulating discussions.

2020-11-13

## Dark-matter candidate could display stringy effects in the lab

-Calculations show how theoretical ‘axionic strings’ could create odd behavior if produced in exotic materials in the lab- A hypothetical particle that could solve one of the biggest puzzles in cosmology just got a little less mysterious. A RIKEN physicist and two colleagues have revealed the mathematical underpinnings that could explain how so-called axions might generate string-like entities that create a strange voltage in lab materials[1].

2020-11-12

## Week 2 of November

Title: The maximal excess charge in reduced Hartree-Fock molecule Author: Yukimi Goto arXiv: http://arxiv.org/abs/2002.11864v6 Title: The maximum energy of shock-accelerated electrons in a microturbulent magnetic field Author: Donald C. Warren, Catherine A. A. Beauchemin, Maxim V. Barkov, Shigehiro Nagataki arXiv: http://arxiv.org/abs/2010.06234v2 Title: Quantification of Ebola virus replication kinetics in vitro Author: Laura E. Liao, Jonathan Carruthers, Sophie J. Smither, CL4 Virology Team, Simon A. Weller, Diane Williamson, Thomas R. Laws, Isabel Garcia-Dorival, Julian Hiscox, Benjamin P. Holder, Catherine A. A. Beauchemin, Alan S. Perelson, Martin Lopez-Garcia, Grant Lythe, John Barr, Carmen Molina-Paris arXiv: http://arxiv.org/abs/2010.09898v1 Title: Self-learning Monte-Carlo for non-abelian gauge theory with dynamical fermions Author: Yuki Nagai, Akinori Tanaka, Akio Tomiya arXiv: http://arxiv.org/abs/2010.11900v1 Title: Spin-orbital magnetic response of relativistic fermions with band hybridization Author: Yasufumi Araki, Daiki Suenaga, Kei Suzuki, Shigehiro Yasui arXiv: http://arxiv.org/abs/2011.00882v1 Title: Diabatic quantum annealing by counter-diabatic driving Author: Luise Prielinger, Andreas Hartmann, Yu Yamashiro, Kohji Nishimura, Wolfgang Lechner, Hidetoshi Nishimori arXiv: http://arxiv.org/abs/2011.02691v1 Title: Estimating the nuclear saturation parameter via low-mass neutron star asteroseismology Author: Hajime Sotani arXiv: http://arxiv.org/abs/2011.03167v1 Title: From supernova to supernova remnant: comparison of thermonuclear explosion models Author: Gilles Ferrand, Donald C. Warren, Masaomi Ono, Shigehiro Nagataki, Friedrich K. Roepke, Ivo R. Seitenzahl, Florian Lach, Hiroyoshi Iwasaki, Toshiki Sato arXiv: http://arxiv.org/abs/2011.04769v1 Title: Ab initio construction of the energy density functional for electron systems with the functional-renormalization-group aided density functional theory Author: Takeru Yokota, Tomoya Naito arXiv: http://arxiv.org/abs/2010.07172v2 Title: Distribution of Energy-Momentum Tensor around a Static Quark in the Deconfined Phase of SU(3) Yang-Mills Theory Author: Ryosuke Yanagihara, Masakiyo Kitazawa, Masayuki Asakawa, Tetsuo Hatsuda arXiv: http://arxiv.org/abs/2010.13465v1 Title: Wigner functions and quantum kinetic theory of polarized photons Author: Koichi Hattori, Yoshimasa Hidaka, Naoki Yamamoto, Di-Lun Yang arXiv: http://arxiv.org/abs/2010.13368v1

2020-11-11

## Ceremony for RIKEN President's Certificates of Appreciation via online

Dr. Y. Kubota, Dr. R. Iritani and Dr. T. Okada received RIKEN President's certificates of appreciation from Dr. Shigeo Koyasu (RIKEN Executive Director) via online on October 22. These certificates are for 2020 Takebe Katahiro Prize for Encouragement of Young Researchers from The Mathematical Society of Japan (Dr. Kubota) and for 15th Young Scientist Award from Japanese Society for Mathematical Biology (Dr. Iritani and Dr. Okada). Many congratulations!

2020-11-09

## Online event "Do you really know what the black hole is?" (iTHEMS x academist)

On December 6, 2020, iTHEMS and academist will have an online event "Do you really know what the black hole is?" Forefront physicists will explain theories and observations of blackholes behind the 2020 Nobel Prize in Physics.

2020-11-09

## Biology Seminar by Dr. Takahiro Sakamoto on November 5, 2020

On November 5th, Takahiro Sakamoto from SOKENDAI gave a talk at the iTHEMS Biology Seminar. First, he gave a very nice introduction about the basics of population genetics, and then, he talked about his theoretical study about how genetic divergence proceeds when there is migration between two locally adapted sub-populations. He did very well in explaining his research, which is actually quite complicated, to non-experts, and because of that there were many questions and fruitful discussions. Takahiro is a student from my previous lab and I had in mind to invite him at some point because I knew he is good at giving talks and that his research should be interesting to iTHEMS people. So I was pleasantly surprised that Okada-san invited him, and I was very glad to see that many people enjoyed his talk. Jeffrey Fawcett

2020-11-09

## Biology Seminar by Dr. Jeffrey Fawcett on October 29, 2020

In iTHEMS biology seminar on October 29, Jeffery Fawcett (RIKEN iTHEMS) gave us a talk on genomic data analysis. He started from explaining basic concepts of evolution and explained a couple of important quantities in population genetics, such as nucleotide diversity and the site frequency spectrum, which can be used to infer an underlying evolutionary process from sampled DNA sequences. He also explained statistical methods to study population structures and illustrated one of the methods in a study of the history of Japanese populations, which was very interesting. He made a great effort into his presentation. His talk was very educational and informative, and both experts and non-experts enjoyed his talk. Besides, the next biology seminar on 11/5 was on theoretical population genetics (I was actually the host), and Jeff helped us to prepare for the next week's seminar. Thank you very much, Jeff! - Takashi Okada

2020-11-05

## Self-introduction: Tianfeng Hou

My name is Tianfeng Hou and I joined iTHEMS in November 2020. I am originally from a city in the east of China. After I finished my undergraduate study, I moved to the Netherlands (Leiden University) to study applied mathematics. And after that I moved to Belgium (KU Leuven) to continue with my PhD career. Recently, I finished my PhD with a title ’Efficient Probabilistic Assessment of Hygrothermal Performance: sequential Monte Carlo and decomposition methods’. Particularly, two tasks are included in this research. First, a faster surrogate model is developed in order to replace the current time-consuming building simulation models. Second, an efficient sampling strategy that can minimize the needed simulations in the framework of Monte Carlo based probabilistic analysis is set up. All in all, I think mathematics is fun, and I am very enthusiastic about the use of mathematics to solve different engineering problems. During my stay in iTHEMS I hope I can have the opportunity to cooperate with researchers from different disciplines and explore more about the beauty of mathematics.

2020-10-30

## iTHEMS Theoretical Physics Seminar on October 23, 2020

The iTHEMS Theoretical Physics Seminar is held on October 23, 2020. The speaker is Dr. Masanori Hanada in Department of Mathematics, the University of Surrey. The title is ”Toward simulating Superstring/M-theory on a Quantum Computer”. He present a framework for simulating superstring/M-theory on a quantum computer, based on holographic duality. Because holographicduality maps superstring/M-theory to quantum field theories (QFTs), we can study superstring/M-theory if we can put such QFTs on a quantum computer --- but it still looks like a complicated problem, if we use a usual lattice regularization. Here he propose an alternative approach, which turns out to be rather simple: we map the QFT problems to matrix models, especially the supersymmetric matrix models such as the Berenstein-Maldacena-Nastase (BMN) matrix model. Supersymmetric matrix models have natural applications to superstring/M-theory and gravitational physics, in an appropriate limit of parameters. Furthermore, for certain states in the Berenstein-Maldacena-Nastase (BMN) matrix model, several supersymmetric quantum field theories dual to superstring/M-theory can be realized on a quantum device. It is straightforward to put the matrix models on a quantum computer, because they are just quantum mechanics of matrices, and the construction of QFTs is mapped to the preparation of certain states. He show the procedures are conceptually rather simple and efficient quantum algorithms can be applied. In addition, as a (kind of) byproduct, he provide a new formulation of pure Yang-Mills on quantum computer. The seminar was held via the Zoom online conference systems, and more than 15 people including outside of iTHEMS attended the seminar.

2020-10-27

## Established RIKEN SUURI CORPORATION with investment from RIKEN, RIKEN Innovation Co., Ltd., and JSOL

-Building a New Innovation Platform through Collaboration between Academia and Business- RIKEN, RIKEN Innovation Co., Ltd. and JSOL Corporation have jointly established RIKEN SUURI CORPORATION, effective October 1, 2020. This is RIKEN's first investment in a venture. RIKEN, Japan's only research institute for the natural sciences, has a wealth of research and development capabilities that have been cultivated over its more than 100-year history, the first product to be brought to the market by RIKEN's investment was neither state-of-the-art equipment nor a drug, but "the best brains in the mathematical sciences itself". RIKEN SUURI CORPORATION aims to be a company that maximizes the use of mathematical sciences to solve the fundamental problems of society.

2020-10-27

## Research Collaboration Agreement Signed to Expand the Field of Multi-Messenger - RIKEN CPR, iTHEMS and ICRR The University of Tokyo

By October 22, RIKEN Cluster for Pioneering Research, iTHEMS and Institute for Cosmic Ray Research concluded a research collaboration agreement to further promote research cooperation in the field of multi-messenger cosmic ray physics, including joint research and personnel exchanges.

2020-10-23

## iTHEMS Theoretical Physics Seminar by Dr. Tokuro Fukui on October 22, 2020

On October 22, the iTHEMS-phys seminar entitled "Realistic shell model and chiral three-body force” given by Dr. Tokuro Fukui (YITP, Kyoto U.) was held. He and his collaborators proposed the way to calculate matrix elements of the three-body nuclear force, and showed the importance and effects of the three-body nuclear force in medium-heavy nuclei, such as calcium and nickel isotopes, starting from the chiral nuclear force using the shell model calculation. During his seminar, he introduced their works from the introduction to state-of-art results. The seminar was held via the Zoom online conference systems, and more than 25 people including outside of iTHEMS attended the seminar.

2020-10-22

## Biology Seminar by Dr. Christos Merkatas on October 21, 2020

On October 21st, Dr. Christos Merkatas from Aalto University in Finland gave a talk at the iTHEMS Biology Seminar. His talk was entitled, “Bayesian Nonparametric Estimation of Random Dynamical Systems”. Suppose that the observed time series is small, and the noise process is non-Gaussian. How can we reconstruct and predict the behavior of the system? Dr. Merkatas showed that the proposed Bayesian approach enables us to reconstruct and predict the system by inferring the number of unknown components and their variances. According to him, the method can be applied to the problems in physics, biology, and economy. Since some of the audiences including me were not familiar with his method, we asked many basic questions. The talk by Dr. Merkatas was great and also educative. Gen Kurosawa

2020-10-22

## Coffee Meeting on October 9, 2020

At the weekly coffee meeting on October 9th (Fri.), Dr. Jeremy Riousset (Florida Institute of Technology) gave a nice description on the properties of "Planetary lightning". After his talk, Dr. Shigehiro Nagataki (Deputy Program Director, iTHEMS) gave an explanation on this year's Nobel Prize in Physics "the discovery that black hole formation is a robust prediction of the general theory of relativity”.

2020-10-21

## DMWG seminar by Dr. Rinaldi: Towards the cosmological signature of composite DM

There are lots of dark matter (DM) candidates of particles and/or non-particles. One important requirement is that DM should be massive. When we consider the main origin of the visible mass in the Universe, it is the proton, i.e. a composite of three-quarks bound by the strong interaction. Then we can realize the DM mass naturally if we introduce similar dynamics in the dark sector. The interaction between the dark and the standard model sector is different from that of DM self-interaction, hence it is also safe under the cosmological requirements. Among the varieties of composite DM models, the stealth DM scenario is a well-motivated one with minimal assumptions. It is different from other baryonic composite DM since it is developed for solving the problem of DM rather than for another mystery in the standard model. Let's consider the signatures in cosmological observations which we could expect for the stealth DM scenario. Since the structure of the stealth DM is similar to that of the standard model baryons, they should experience the confined-unconfined phase transition in the early Universe. If the phase transition is of the 1st order, numerous vacuum babbles are produced in the transition from the false- to the true vacuum. The collision of these bubbles sources the low-frequency gravitational waves (GWs) of a ~nHz-mHz range. However, it is difficult to calculate the physics around the phase transition. Indeed, it is not obvious whether the phase transition occurs in the 1st order or not. When it is of the 1st order, the gravitational wave spectrum is determined using the temperature of the Universe at the phase transition. Dr. Rinaldi and the members of the Lattice Strong Dynamics collaboration have investigated the phase transition in the stealth DM scenario by applying the sophisticated calculation techniques developed for the strongly-interacting sector in the standard model. They reveal that the lower bound of the 1st order phase transition temperature for the scenario, which is then directly converted to the lower bound on the frequency of the GW. The technique should enable us to study DM from multiple aspects as is shown in this talk. Furthermore, this is the beginning of a new interdisciplinary study in which DM becomes the portal to connect the strong dynamics and GW cosmology, which could further enhance our understanding of this world!

2020-10-15

## Week 2 & 3 of October

Title: Seiberg-Witten Floer homotopy contact invariant Author: Nobuo Iida, Masaki Taniguchi arXiv: http://arxiv.org/abs/2010.02132v1 Title: The groups of diffeomorphisms and homeomorphisms of 4-manifolds with boundary Author: Hokuto Konno, Masaki Taniguchi arXiv: http://arxiv.org/abs/2010.00340v1 Title: Global 3-group symmetry and 't Hooft anomalies in axion electrodynamics Author: Yoshimasa Hidaka, Muneto Nitta, Ryo Yokokura arXiv: http://arxiv.org/abs/2009.14368v1

2020-10-07

## Math-Phys Joint Seminar by Toshihiro Ota on October 2, 2020

On October 2, Toshihiro Ota gave a talk at the iTHEMS Math-Phys Joint Seminar. His whole talk was on the interrelation among integrable lattIce models, quiver gauge theories, and hidden TQFT structure. His first talk was a sort of lecture on TQFT and integrable lattice model at an elementary level. At the beginning of the first talk, he explained quantum mechanics (QM). Then as a variant of QM, he introduced an axiomatic definition of topological quantum field theory as a special class of quantum field theory. He also introduced lattice model which can be seen as a discrete version of quantum field theories. In particular, he mentioned the integrability of the 1-dimensional Ising model. In the second talk, he focused on the correspondence between Wilson-'t Hooft lines in a class of quantum gauge theories and transfer matrices in the corresponding integrable lattice models. At first, he gave an explanation of “classical integrability” and “quantum integrability” for field theories. In the case of 2-dimensional lattice model, he explained that the integrability is described by the Yang-Baxter equation. Then he moved on to the details of the correspondence. In the lattice model side of the correspondence, he described the transfer matrix in terms of n-copies of L-operators. Moreover, in order to compare to the gauge theory side, he took the trigonometric limit and rewrote the transfer matrix by “more fundamental” L-operators. The gauge theory side is in particular given by 4d N=2 n-node circular quiver theory. The theory is defined on a 4d twisted spacetime S^1 xε R^2 x R, and he gave an expression of the Wilson-'t Hooft line wrapping the circle S^1. As the main result of his joint work with Kazunobu Maruyoshi and Junya Yagi, he gave a relation between these Wilson-’t Hooft lines and transfer matrices. Finally, he gave several comments related to integrability from TQFT in extra dimension.

2020-10-06

## Self-introduction: Maria Giovanna Dainotti

I am originally from a city in South of Italy. After my PhD at the University of Rome La Sapienza in 2008 I moved to Jagiellonian University in 2009 as a research assistant and I have been Visiting Scholar in several places all around the globe. I here mention a few: I was already at RIKEN with the JSPS Fellowship in November 2014-January 2015 in the ABBL group under the direction of Nagataki-san and as a visiting researcher in January and February 2019. I was in US at Stanford University with the Fulbright, Marie Curie’ and the American Astronomical Society Fellowship from 2012-2013, and 2015-2018. In all these years I have been studying Gamma-Ray Bursts, selection biases in treating GRB correlations, their application as cosmological tools and as a tool to discriminate among theoretical physical models. More recently I have started working on machine learning for redshift extraction of GRBs and Active Galactic Nuclei and on the selection effects in SNe cosmology in collaboration with Hatsuda-san and Nagataki-san. Last year I started collaborating with Don Warren and Gilles Ferrand to a project that aims to include virtual reality to show GRBs correlations to a broader audience.

2020-10-02

## JST/CRDS Seminar "Series of seminars on the collaboration of mathematics, science and ergonomics" Notice of Registration

The Japan Science and Technology Agency (JST) is pleased to announce that it will hold a seminar titled "Series of Seminars on collaboration between Mathematics, Science and Engineering". There will be 16 sessions in total, covering topics ranging from machine learning to quantum computing, simulation, data science and many more. For more details, please refer to the related link.

2020-10-02

## DMWG seminar by Dr. Ishiyama: a spectacular cosmological N-body simulation

Visible components of our Universe, such as galaxies, show hierarchical structures. Such structures are always embedded in DM structures called "halos". In the early Universe, there exist small density fluctuations that eventually collapse to halos at some points by their self-gravity. Then, halos grow to form larger structures again by self-gravity and this is the origin of the structure of the current Universe. The large-scale structure of halos as well as their inner structures contain information about the nature of the DM particle. Cosmological N-body simulation is a powerful computational method to follow that structure formation, by solving multi-body problems numerically. A halo, which is a clump of elementary DM particles, is treated as one smooth particle in N-body simulation. Its prediction power is so strong that the calculation corresponding to the upcoming cosmological survey, for example, has long been awaited. However, its computational costs scale as the square of the particle number N (or N log N when some reduction methods are adopted) and it is almost impossible to cover everything we need. There are two strategies in the calculation: simulating a large volume with large particle mass, or a small volume with small particle mass. The former is suitable for studies that deal with the large-scale structure while the latter has advantages in studying the properties of each halo. His group has conducted a large high-resolution simulation project which enables us to study both of them. The Uchuu simulation, which uses the cubic of 12800 particles in a 2 Gpc-scale simulation box, enables us to study large-scale structures. The Shin-Uchuu simulation in the same project, which uses the cubic of 6400 particles in a 140 Mpc-scale box, is provided aiming to study the inner structure of DM halos. Analyzing the simulated structure and halo properties, the matter power spectrum covering from the largest to the non-linear regime is obtained. Also, the so-called mass-concentration relation in a wide halo mass range is now available thanks to the project. There is another good news for DM hunters: the results of the simulation are open to the public. This should boost the DM study from many aspects!

2020-10-01

## Week 1 of October

Title: Gabor frames and Wannier bases from groupoid Morita equivalences Author: Chris Bourne, Bram Mesland arXiv: http://arxiv.org/abs/2009.13806v1 Title: Parity of the neutron consistent with neutron-antineutron oscillations Author: Kazuo Fujikawa, Anca Tureanu arXiv: http://arxiv.org/abs/2009.12843v1 Title: Wilson-'t Hooft lines as transfer matrices Author: Kazunobu Maruyoshi, Toshihiro Ota, Junya Yagi arXiv: http://arxiv.org/abs/2009.12391v1 Title: Integer Programming from Quantum Annealing and Open Quantum Systems Author: Chia Cheng Chang, Chih-Chieh Chen, Christopher Koerber, Travis S. Humble, Jim Ostrowski arXiv: http://arxiv.org/abs/2009.11970v1 Title: Two-nucleon S-wave interactions at the SU(3) flavor-symmetric point with mud≃mphyss: a first lattice QCD calculation with the stochastic Laplacian Heaviside method Author: Ben Hörz, Dean Howarth, Enrico Rinaldi, Andrew Hanlon, Chia Cheng Chang, Christopher Körber, Evan Berkowitz, John Bulava, M. A. Clark, Wayne Tai Lee, Colin Morningstar, Amy Nicholson, Pavlos Vranas, André Walker-Loud arXiv: http://arxiv.org/abs/2009.11825v1

2020-10-01

## Dr. Shingo Gibo received the Best Poster Award of the Japanese Society of Chronobiology

Dr. Shingo Gibo received the Best Poster Award of the Japanese Society of Chronobiology. The title of the poster is "Analysis of the circadian period and phase synchronization based on waveform". Congratulations! This is an abstract of the awards: The circadian clocks are based on gene-activity rhythms with approximately 24-hour period, and its temporal waveforms are of various shapes. We theoretically showed that the waveform distortion contributes to the circadian period stability to temperature and entrainment to the environment cycles. Furthermore, by using the renormalization group method, which is developed in theoretical physics, we found that this relation between waveform and period holds not only for the circadian clock but also for many types of nonlinear oscillator models, including van der Pol and Lotka-Volterra model. This study is collaborated with physicists, Drs. Teiji Kunihiro (Kyoto University) and Tetsuo Hatsuda (iTHEMS).

185 news in 2020