The sustainable development of modern society necessitates technologies that harness earth-abundant metals and organic resources, minimizing reliance on scarce materials. This presentation will introduce our recent efforts towards this goal. We have developed sustainable organic synthesis using sodium dispersion, a molybdenum-quinone species for the diazo-free generation of carbene species from stable and readily available compounds, and a SpiroBpy ligand that enables the site-selective functionalization of arenes under remote steric control. I will also share some of the challenges we face in developing these reactions in order to ensure reproducibility.

(The speaker is also a professor at University of Amsterdam & QuSoft. This is a joint seminar with the iTHEMS Quantum Computation Study Group.)

One of the major challenges in computer science is to establish lower bounds on the resources, typically time, that are needed to solve computational problems, especially those encountered in practice. A promising approach to this challenge is the study of fine-grained complexity, which employs special reductions to prove time lower bounds for many diverse problems based on the conjectured hardness of key problems.
For instance, the problem of computing the edit distance between two strings, which is of practical interest for determining the genetic distance between species based on their DNA, has an algorithm that takes O(n^2) time. Through a fine-grained reduction, it can be demonstrated that a faster algorithm for edit distance would imply a faster algorithm for the Boolean Satisfiability (SAT) problem. Since faster algorithms for SAT are generally considered unlikely to exist, this implies that faster algorithms for the edit distance problem are also unlikely to exist. Other problems used for such reductions include the 3SUM problem and the All Pairs Shortest Path (APSP) problem.
The quantum regime presents similar challenges; almost all known lower bounds for quantum algorithms are defined in terms of query complexity, which offers limited insight for problems where the best-known algorithms take super-linear time. Employing fine-grained reductions in the quantum setting, therefore, represents a natural progression. However, directly translating classical fine-grained reductions to the quantum regime poses various challenges.
In this talk, I will present recent results in which we overcome these challenges and prove quantum time lower bounds for certain problems in BQP, conditioned on the conjectured quantum hardness of, for example, SAT (and its variants), the 3SUM problem, and the APSP problem. This presentation is based on joint works with Andris Ambainis, Bruno Loff, Florian Speelman, and Subhasree Patro.

In recent years, we have gone from databases that store the genetic differences observed between hundreds of thousands of sequenced people to using this information to build the actual genetic trees that relate individuals through their shared ancestors back in time. These genetic trees describe how our genomes have evolved up to millions of years into the past. Additionally, sequencing of DNA from ancient human bone has enabled the direct observation of genomic change over past millennia and has unlocked numerous previously hidden genetic histories. In this talk, I will illustrate how we can unearth the human past from these data, ranging from ancient migrations out of Africa and subsequent mixtures with now extinct Neanderthals to waves of ancestry transformations in a nation’s recent past.

14:45-15:00 Teatime discussion
15:00-16:00 Talk by Dr. Wataru Morita (Researcher, Department of Anthropology, National Museum of Nature and Science / Associate Professor, Department of Biological Sciences, Graduate School of Science, The University of Tokyo)
16:15-17:20 2024 Study Group introduction session
17:30-18:30 Discussion

In this RIKEN DAY, we will introduce various phenomena in the world (all things in the universe) that are understood using "mathematics” and the use of "mathematics", including the latest research, while looking at the annual S&T poster for everyone titlled “Mathematics: One S&T poster for Every Household”.

For details, please see the related links.

While the basic evolution of stars has been understood for many decades, there are still major uncertainties in our overall understanding of how stars end their lives, both in the context of low- and intermediate-mass stars (including the Sun) and massive stars. I will first review some of key principles that govern the structure and evolution of stars and then present recent progress that has been made for both groups of stars. I will argue and present numerical simulations that show that all stars become dynamically unstable when they become large giant stars, which leads to sporadic, dynamical mass ejections. Low- and intermediate-mass stars may lose all of their envelopes as a consequence, leaving white-dwarf remnants. More massive stars experience core collapse, leaving a neutron-star or black-hole remnant, possibly associated with a supernova explosion. I will show how the dramatic recent progress on understanding the core-collapse process, for the first time, allows us to connect the late evolution of massive stars with the resulting supernova explosions and the final remnants and discuss how observations with current gravitational-wave detectors (such as LIGO) will allow us to test this theoretical connection.

We will learn about nuclear fusion and related subjects, such as turbulence in astronomy and astrophysics, from experts and discuss possible interdisciplinary collaborations in the near future. Some researchers will visit RIKEN iTHEMS from the National Institute for Fusion Science (NIFS) and other universities and research institutes for the workshop. We will have the workshop in a hybrid style so that many researchers in Japan can hear the presentations even remotely. This workshop is supported by Moonshot Goal 10 (Program Director Yoshida Zensho (NIFS)).

Program
Session１
9:00-9:35 (25+10: 25 mins for Presentation, 10 mins for Q&A)：Shinya Maeyama
9:35-10:10 (25+10): Naoki Sato
10:10-10:45 (25+10): Yohei Kawazura
10:45-11:15 Coffee Break
Session２
11:15-11:50 (25+10): Takanobu Amano
11:50-12:25 (25+10): Yosuke Matsumoto
12:25-13:00 (25+10): Akira Mizuta
13:00-14:00 Lunch Break
Session３
14:00-14:35 (25+10): Chiho Nonaka
14:35-15:10 (25+10): Takeo Hoshi
15:10-15:45 (25+10): Motoki Nakata
15:45-16:15 Coffee Break
Session ４
16:15-16:50 (25+10): Kumiko Hori
16:50-17:25 (25+10): Yutaka Ohira
17:25-18:00 (25+10): Camilia Demidem (TBC)
18:30-20:30: Dinner in the Main Research Building.

iTHEMS Cosmology Forum Workshop is a series of short workshops, each focused on an emerging topics in cosmology. The targeted audience is cosmologists, high-energy physicists and astronomers interested in learning about the subject, not just those who have already worked on the topic. The goal of the workshop is to provide working knowledge of the topic and leave dedicated time for discussions to encourage mutual interactions among participants.

The first workshop is devoted to cosmic birefringence, a newly establishing cosmological probe of the nature of our universe. Cosmic birefringence is the rotation of the linear polarization plane of the cosmic microwave background (CMB) radiation and, thanks to its origin, inherently measures the degree of parity violation in the cosmic history. This one-day workshop gathers both the observational and theoretical aspects of this growing topic.

The workshop will be in English. The venue is on RIKEN Wako Campus, and the exact room is yet to be determined, depending on the number of registered participants.

The workshops are organised by the iTHEMS Cosmology Forum working group, which is the successor of the Dark Matter Working Group at RIKEN iTHEMS.

Important dates:
30th April - Registration deadline
14th May - Workshop Day

Invited Speakers:
Toshiya Namikawa (Kavli IPMU)
Maresuke Shiraishi (Suwa University of Science)
Fuminobu Takahashi (Tohoku University)

Organisers:
Kohei Hayashi, Nagisa Hiroshima, Derek Inman, Amaury Micheli, Ryo Namba

Drawing from a thought experiment that we conduct, we propose that a virtual graviton gives rise to a black hole geometry when its momentum surpasses a certain threshold value on the Planck scale. This hypothesis implies that the propagator of a virtual graviton, that possesses momentum surpassing this threshold, vanishes. Consequently, a Feynman diagram containing this type of graviton propagator does not add to the overall amplitude. This mechanism suggests the feasibility of formulating an ultraviolet-finite four-dimensional quantum gravitational theory. The elementary particles including the gravitons are treated as point particles in this formulation.

Thanks to intensive research efforts, topology has been established as a fundamental concept in physics. For closed quantum systems, the classification of gapped topological phases has matured. Moreover, the importance of topology is not limited to isolated quantum systems. Recently, the topology of non-Hermitian Hamiltonians, which effectively describe systems with dissipation, has attracted much attention worldwide. This fascination is exemplified by topological phases and topological phenomena unique to non-Hermitian systems.

Against this background, the primary purpose of this workshop is to bring together researchers working on topological phases and to discuss (i) open questions in topological phases of closed quantum systems and (ii) the role of topology in open quantum systems and measurements.