# Press Release

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

2020-11-19

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.

# Research News

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

2020-11-13

-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].

# Seminar Report

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

2020-11-16

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.

Mathematics of thermalization in isolated quantum systems

November 10 at 16:00 - 18:10, 2020

# Upcoming Events

## Colloquium

### The Unreasonable Effectiveness of Quantum Theory in Mathematics

November 26 at 10:00 - 11:30, 2020

Prof. Robbert Dijkgraaf (Director, Institute for Advanced Study in Princeton, USA)

November 26 at 10:00-11:30, 2020 (JST)

November 25 at 20:00-21:30, 2020 (EST)

The physical concepts of quantum theory, in particular of quantum gravity and string theory, have proven to be extremely powerful in addressing deep problems in pure mathematics, from knot invariants to algebraic geometry. Is there such a thing as “quantum mathematics”? Should we add Feynman diagrams, strings, branes and black holes to the language of mathematics?

Venue: via Zoom

Event Official Language: English

## Lecture

### Toward the Practical Use of Quantum Computers

December 4 at 10:30 - 12:00, 2020

Dr. Shunji Matsuura (Visiting Scientist, iTHEMS / Fundamental Researcher, Quantum Simulation Division, 1QBit, Canada)

量子コンピュータは古典コンピュータとは異なる原理に基づいて動いており、自然科学を含む様々な分野において大きな変化をもたらすと考えられている。特にこの数年の進展は著しく、量子計算の古典計算に対する優位性が実験的に初めて示されるなど、期待されているマイルストーンが着実に達成されていっている。一方で量子コンピュータの発展において常に障害となっているのがノイズである。量子状態はノイズの影響を受けやすく、現在の量子コンピュータにおいては量子ゲート操作を行うごとに状態の精度が減衰していってしまう。そのため、量子コンピュータにかける負担をできるだけ減らすようなアルゴリズムの開発や、計算結果からエラーを取り除く方法、観測回数をできるだけ減らす方法等、様々な研究が行われている。本講義ではこれら量子コンピュータの実用化に向けた最近の研究と今後の課題について話す。

Venue: via Zoom

Event Official Language: Japanese

## External Event

### Presented by iTHEMS & academist - Do you really know what the black hole is?

December 6 at 14:00 - 16:00, 2020

Dr. Shigehiro Nagataki (Deputy Program Director, iTHEMS / Chief Scientist, Astrophysical Big Bang Laboratory, RIKEN Cluster for Pioneering Research (CPR))

Dr. Yoshiyuki Inoue (Senior Visiting Scientist, iTHEMS / Associate Professor, Department of Earth and Space Science, Graduate School of Science, Osaka University)

Dr. Yuki Yokokura (Senior Research Scientist, iTHEMS)

–From the latest theories and observations to the explanation of the Nobel Prize in Physics! An introduction to black holes from active physicists–

The 2020 Nobel Prize in Physics was awarded to Sir Roger Penrose, Prof. Dr. Reinhard Genzel and Prof. Andrea Ghez for their contributions to the theory and observation of black holes. Black holes have continued to provide hot topics in recent years, such as gravitational waves from black hole coalescence and black hole imaging, but do you really know what black holes are? Three cutting-edge black hole researchers will explain its identity and mystery.

Venue: via Online

Event Official Language: Japanese

# Paper of the Week

## Week 3 of November

2020-11-19

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

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