RIKEN Interdisciplinary Theoretical and
Mathematical Sciences Program

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Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS) is an international research program at RIKEN. It facilitates close collaborations among researchers from different disciplines in theoretical, mathematical and computational sciences. The ultimate goal of iTHEMS is to unravel the mystery of the Universe, matter, and life, as well as to solve key problems in modern society through interdisciplinary approaches.

About iTHEMS

Upcoming Events


iTHEMS Colloquium

Finding Gravitational Waves from the Early Universe

September 27 at 16:00 - 17:30, 2021

Prof. Eiichiro Komatsu (Director, Max Planck Institute for Astrophysics, Germany)

The Cosmic Microwave Background (CMB) gives a photographic image of the Universe when it was still an “infant”. We have been using it to test our ideas about the origin of the Universe. The CMB research told us a remarkable story: the structure we see in our Universe such as galaxies, stars, planets, and eventually ourselves originated from tiny quantum fluctuations in the period of the early Universe called cosmic inflation. While we have accumulated strong evidence for this picture, the extraordinary claim requires extraordinary evidence. The last prediction of inflation that is yet to be confirmed is the existence of primordial gravitational waves whose wavelength can be as big as billions of light years. To this end we have proposed to JAXA a new satellite mission called LiteBIRD, whose primary scientific goal is to find signatures of gravitational waves in the polarisation of the CMB. In this presentation we describe physics of gravitational waves from inflation, and the LiteBIRD proposal.

Venue: via Zoom

Event Official Language: English

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Seeking a Postdoctoral Researcher or Research Scientist (W21003)

Deadline: Open until filled

Postdoctoral Researcher or Research Scientist, a few positions. In particular, the applicant(s) are expected to spend at least 50% of their time carrying out original research developing numerical models to describe biological systems, such as the spread of virus in a cell culture, in collaboration with Dr. Catherine Beauchemin.

Seeking a Female Research Scientist or a Female Senior Research Scientist (W21071)

Deadline: Open until filled

Female Research Scientist or Female Senior Research Scientist, a few positions. Seeking a female researcher or a female senior researcher to conduct theoretical research in the fields of natural sciences, mathematical sciences, or humanities and social sciences.

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Latest News


Hot Topic

Mathematics and Physics: Topology, Insulators and My Research Life

Dr. Tomoki Ozawa (Visiting Scientist, iTHEMS) writes on the website "SURI-JOSHI" about topological insulators and his research life and daily life. Please see the related link for the article.


Research News

A New Mechanism to Explain Multispecies Coexistence in Plants - Evolutionary Rescue Caused by the Evolution of Self-Fertilization before Flowering

Koki Katsuhara (Assistant Professor, Okayama University; at the time: Kobe University), Yuuya Tachiki (Assistant Professor, Tokyo Metropolitan University), Ryosuke Iritani (Research Scientist, iTHEMS; at the time: University of California, Berkeley, University of Exeter) and Atsushi Ushimaru (Professor, Kobe University) performed simulations using an individual-based model and found that in two plant species that share the same species of pollinator and are in competition, evolutionary rescue occurs in which the evolution of higher self-fertilization rates in the rarer species results in an increase in population size, thereby promoting long-term coexistence between the two species. The results of this study add a new theory to explain why multiple flowering species can coexist in the same place, and also provide a new perspective for the evolution of diverse reproductive strategies in plants. Understanding the mechanisms that create and maintain plant diversity, which supports the basis of terrestrial ecosystems, is essential not only for understanding the origin of biodiversity, but also for forming a sustainable society in harmony with ecosystems, and is an important knowledge in both basic and applied aspects. For more information, please visit the Okayama University website at the related link.


Paper of the Week

Week 3, September 2021

Title: Equation of state of neutron star matter and its warm extension with an interacting hadron resonance gas Author: Yuki Fujimoto, Kenji Fukushima, Yoshimasa Hidaka, Atsuki Hiraguchi, Kei Iida arXiv: http://arxiv.org/abs/2109.06799v1

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