Coffee Meeting Log
2022-01-28
Determination of hadronic interactions from lattice QCD
Takuya Sugiura (Postdoctoral Researcher, iTHEMS)
The interactions between hadrons (such as proton and neutron) govern the structure of atomic nucleus. I will briefly discuss how we can define and quantify the hadronic interactions through numerical calculations of lattice QCD.
2022-01-21
From the thermonuclear supernova to the supernova remnant
Gilles Ferrand (Research Scientist, iTHEMS / Researcher, Astrophysical Big Bang Laboratory, RIKEN Cluster for Pioneering Research (CPR))
Type Ia supernovae (SNe) are believed to be the thermonuclear explosion of a white dwarf star, but their explosion mechanism(s) remain unclear. In this talk we make the connection with the subsequent phase, the supernova remnant (SNR), when the stellar ejecta interact with the interstellar medium. I will outline how simulations and observations can help test theoretical models, with an emphasis on our recent work based on the 3D morphology.
2022-01-14
Cosmic origin of r-process elements?
Nobuya Nishimura (Astrophysical Big Bang Laboratory, RIKEN Cluster for Pioneering Research (CPR))
The astronomical site of r-process nucleosynthesis has been a long-standing mystery in nuclear astrophysics studies. However, in recent years, there has been significant progress. We confirmed the r-process-driven transient "kilonova" associated with binary-neutron-star mergers. In this talk, I will discuss the possibility of the r-process in magneto-rotational supernovae, which are in the extreme class of core-collapse supernovae. Although this scenario is physically challenging and hypothetical, observational evidence appears to grow. Since this scenario is related to supernovae with many observational examples, we expect future direct/indirect observation. I will also discuss the theoretical perspective of observational properties.
2021-12-24
Quantum chaos, Entanglement and Black holes
Tomoki Nosaka (Research Part-time Worker Ⅰ, iTHEMS)
Quantum chaos is a notion to characterize the mechanism of how the time evolution of a quantum many body system, which should be in principle reversible, end up with the thermal equilibrium where the information of the initial condition is lost. This resembles the black hole information problem, which suggests that one can address various fundamental questions related to black holes through the study of quantum chaos. In this talk I will overview the notions of quantum chaos and black hole geometry, and then introduce an interesting phenomenon called revival where these notions are tightly entangled with each other.
2021-12-17
Dimensional regularization
Matthias Berwein (Postdoctoral Researcher, iTHEMS)
Dimensional regularization is one of the most important tools for analytic calculations in quantum field theory. I will explain, how the concept of integration over (integer) n variables can be extended to a continuous number D, the dimension, and how this can be used to make sense of the divergent parts of quantum corrections.
2021-12-10
Dispersal and organization of glioma cells
Gilberto Nakamura (Postdoctoral Researcher, iTHEMS)
Cell migration plays a pivotal role in modeling the invasiveness of gliomas (a type of brain cancer) while the formation of new tumors often relies on cell-cell adhesive forces. I will talk about motility-induced phase separation as an alternative explanation to tackle both cell migration and tumor formation.
2021-12-03
Machine leaning approaches for weather prediction
Shigenori Otsuka (Research Scientist, iTHEMS / Research Scientist, Data Assimilation Research Team, RIKEN Center for Computational Science (R-CCS))
Recently, many groups are applying deep learning techniques for weather prediction problems. In this talk, I would like to introduce our research activities at R-CCS. We have been developing an algorithm to integrate data-driven approaches and process-driven approaches for precipitation nowcasting.
2021-11-26
Evolution of core-collapse supernovae to their supernova remnants
Masaomi Ono (Research Scientist, iTHEMS / Research Scientist, Astrophysical Big Bang Laboratory, RIKEN Cluster for Pioneering Research (CPR))
Observations of nearby supernova remnants (SNRs) could potentially provide the clues to elucidate the dynamical evolution of core-collapse supernovae (CCSNe), chemical evolution of elements in the ejecta, explosion mechanisms, properties of neutron stars and progenitor stars. In this talk, our recent three-dimensional hydrodynamical models for the evolution of CCSNe to their SNR are introduced. Additionally, an attempt to model the molecule formation in the ejecta is also mentioned.
2021-11-19
A Tale of Two Spaces
Tsukasa Tada (Coordinator, iTHEMS / Vice Chief Scientist, Quantum Hadron Physics Laboratory, RIKEN Nishina Center for Accelerator-Based Science (RNC))
2021-11-05
Gravitational wave asteroseismology on protoneutron stars
Hajime Sotani (Research Scientist, iTHEMS / Research Scientist, Astrophysical Big Bang Laboratory, RIKEN Cluster for Pioneering Research (CPR))
Focusing on the supernova gravitational waves, we are considering to extract the EOS inofrmation for dense matter with asteroseismology.
2021-10-29
Nuclear physics from lattice QCD
Takumi Doi (Senior Research Scientist, iTHEMS / Senior Research Scientist, Quantum Hadron Physics Laboratory, RIKEN Nishina Center for Accelerator-Based Science (RNC))
The interactions between nucleons (and in general, hadrons) govern the structure of matter, such as nuclei and neutron stars. I will talk about first-principles calculations to determine the interactions from the fundamental theory of quarks and gluons, QCD.
2021-10-22
Physics of Relativistic Radiation Mediated Shocks
Hirotaka Ito (Research Scientist, iTHEMS / Research Scientist, Astrophysical Big Bang Laboratory, RIKEN Cluster for Pioneering Research (CPR))
2021-10-15
Annoucement of Super Smash Problems (SSP) workshop
Hiroyasu Miyazaki (Senior Research Scientist, iTHEMS)
I will make an annoucement of the forthcoming Super Smash Problems workshop on Novermber 24-26.
2021-10-08
Cooper triples in atomic fermi gas: Implication for dense quark matter
Shoichiro Tsutsui (Special Postdoctoral Researcher, Quantum Hadron Physics Laboratory, RIKEN Nishina Center for Accelerator-Based Science (RNC))
I propose a microscopic mechanism to reproduce the peak structure of the speed of sound of within a cold atomic model. This would be useful to understand equations of state of neutron star.
2021-09-24
GRB afterglows and you
Don Warren (Research Scientist, iTHEMS / Research Scientist, Astrophysical Big Bang Laboratory, RIKEN Cluster for Pioneering Research (CPR))
2021-09-17
Localization in the directions of Schrödinger equations
Keita Mikami (Research Scientist, iTHEMS)
For a particular class of Schrödinger equations, the solutions to the equation localize in the directions as time goes infinity. In this small talk, we review some known results on this subject.
2021-09-10
An invitation to algebraic quantum field theory
Mizuki Oikawa (Junior Research Associate, iTHEMS / Student Trainee, iTHEMS / Ph.D. Student, Graduate School of Mathematical Sciences, The University of Tokyo)
I am a new member of RIKEN iTHEMS and working on mathematics of conformal field theory. In this talk, noninteger dimensions in tensor categories and their relationship to algebraic quantum field theory will be introduced.
2021-08-27
Toward quantum computation of quantum field theory
Etsuko Itou (Postdoctoral Researcher, iTHEMS / Contract Researcher, Strangeness Nuclear Physics Laboratory, RIKEN Nishina Center for Accelerator-Based Science (RNC))
Public2021-08-06
Message-passing algorithms for graphical models
Yingying Xu (Special Postdoctoral Researcher, iTHEMS)
Inference problems like marginalization and maximization are NP-hard to solve exactly and approximately in a graphical model. The complexity can be reduced dramatically when the underlying factor graph has some special structure. One extreme case is that of tree factor graphs, in which marginals can be computed in a number of operations which grows linearly with number of notes. This can be done by a ‘dynamic programming’ procedure often called as message passing or belief propagation algorithms. The update rules have been discovered independently in several different contexts: statistical physics (‘Bethe-Peierls approximation’), coding theory (the ‘sum-product’ algorithm), and artificial intelligence (‘belief propagation’, BP). The time evolution of the message’s distributions is known under the name of ‘density evolution’, and the fixed-point analysis of them is done by the replica-symmetric cavity method.