On April 28, Prof. Yoshihiko Hasegawa (Associate Professor, The University of Tokyo) gave us a talk on the thermodynamic uncertainty relation (TUR).
In the first part of his talk, he started from a motivation to consider trade-off relations between energy and cost, showing biological examples. After reviewing general theory of stochastic thermodynamics and TUR for classical Markovian systems, he presented two recent works of him: one is to derive the TUR from information-theoretic method (i.e., the Cramer-Rao bound) and the second is to derive it from the fluctuation theorem.
In the second part, he discussed quantum version of the TUR. After the review of quantum dynamics under measurement, he showed the quantum TUR for general open systems. He applied his theory to continuously measured systems and explained its physical meaning.
There were a lot of interactive discussions during and after the talk. We really thank Prof. Hasegawa for his great talk.
Reported by Ryusuke Hamazaki
On April 21st, Dr. Se Kwon Kim from KAIST gave a talk about unconventional spin transport in quantum materials. First, he gave an overview of spintronic physics. The advancements in spintronic techniques can potentially lead to new applications, such as quantum information science.
Then, he showed the realization of magnonic topological insulators, which are Chern insulators with spin current but without electron charge current. Furthermore, he predicted that spin transport induces vortex flow in superconductors. We thank Dr. Kim for giving a wonderful talk.
Reported by Ching-Kai Chiu
May 12 at 10:00 - 11:00, 2021
Dr. Takahiro Nishimichi (Yukawa Institute for Theoretical Physics, Kyoto University)
Recent developments in observational technologies open exciting opportunities to map out the detailed structure of the universe. Remarkably, the unique combination of imaging and spectroscopic galaxy surveys is now becoming well established as a standard analysis methodology for precision cosmology. While the former can access directly the underlying clustering of mass dominated by dark matter projected on the sky through the weak gravitational lensing effect, the latter provides us with the three dimensional map of the structure traced by galaxies. One can mitigate the galaxy-bias uncertainty, which has been the major obstacle for cosmology based on galaxy surveys, by jointly analyzing these effects. We still need, however, a robust and versatile theoretical and statistical framework to interpret these datasets. The Dark Quest project, launched in 2015, is a structure formation simulation campaign precisely
for this purpose. We have developed an emulation tool, dubbed as Dark Emulator, based on a large database of simulated dark matter halos in virtual universes with different cosmologies efficiently sampled in six-dimensional parameter space. Dark Emulator employs a simple machine-learning architecture with Gaussian process at its core. It makes predictions of various statistical measures of dark matter halos, both lensing and clustering observables, for a given cosmological parameters in a few seconds on laptop computers without running a new simulation. This AI-aided tool, once supplemented with recipes for the halo-galaxy connection, is therefore applicable to real-data analyses as the theoretical template, which typically requires hundreds of thousands of function calls in the course of parameter inference. I will introduce this project and report the status of its application to Subaru HSC data.
We are looking forward to seeing you online.
Venue: via Zoom
Event Official Language: English
May 12 at 17:00 - 18:15, 2021
Prof. Christopher Bourne (Visiting Scientist, iTHEMS / Assistant Professor, Advanced Institute for Materials Research (AIMR), Tohoku University)
Key features of topological insulators and superconductors such as stable edge modes have been found in an increasingly broad class of materials and systems. In this talk, I will introduce a mathematical framework to study Hamiltonians and topological phases on a general class of (aperiodic/random) point atterns. Using techniques from noncommutative geometry, we then show how bulk topological invariants and the bulk-boundary correspondence can be rigorously established in such generic systems.
This is based on joint work with Emil Prodan and Bram Mesland.
*Detailed information about the seminar refer to the email.
Venue: via Zoom
Event Official Language: English
May 6 - 7, 2021
Visiting Scientist, iTHEMS / Assistant Professor, Department of Physics, Faculty of Science, University of Toyama
Research fields: Dark Matter, High Energy Astrophysics
Visiting Place: RIKEN Wako Campus
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