iTHES Theoretical Science Colloquium

Approaches to inflationary cosmology

December 19 (Tue) at 15:00 - 16:30, 2017

Jun'ichi Yokoyama (The University of Tokyo)

The 24th iTHES Theoretical Science Colloquium

Venue: Okochi Hall

Event Official Language: English

Simulations and machine learning going hand in hand for clinical medicine

October 30 (Mon) at 15:00 - 16:30, 2017

Hiroshi Suito (Professor, Advanced Institute for Materials Research (AIMR), Tohoku University)

The 23rd iTHES Theoretical Science Colloquium Recent rapid progress of AI technologies has strongly affected the medical community, profoundly enhancing medical image analysis as well as improving decision-making in clinical practice. Nevertheless, black-box systems cannot be accepted easily in clinical medicine because of issues related to accountability and incorporation of new and rapidly developing medical technologies. This talk presents a bilateral approach to cardiovascular problems consisting of (1) machine learning approach for estimation of fluid dynamical forces such as wall shear stress and oscillatory shear index by using geometrical information of the vessels; and (2) simulation approach for understanding physical mechanisms, from vessel geometry to wall forces distributions via flow patterns, using fluid–structure interaction analysis based on partial differential equations. This work was conducted as part of our JST-CREST project: "New challenges for mathematical modeling in clinical medicine."

Venue: 2F Large Meeting Room, RIBF Building, RIKEN Wako Campus

Broadcast:R511, Computational Science Research Building

Event Official Language: English

Introduction to topological quantum computing

July 28 (Fri) at 15:00 - 16:30, 2017

Zhenghan Wang (University of California Santa Barbara, USA)

The 22nd iTHES Theoretical Science Colloquium Topological quantum computing is a paradigm to build a quantum computer with topological phases of matter. Majorana physics is the best example of topological physics besides quantum Hall. I will give an introduction to building a topological quantum computer with Majorana zero modes.

Venue: Suzuki Umetaro Hall

Event Official Language: English

Shapes of discrete groups

May 18 (Thu) at 15:30 - 17:00, 2017

Takashi Tsuboi (Deputy Program Director, iTHEMS)

The 21st iTHES Theoretical Science Colloquium I will talk about several attempts to understand infinite groups. The group structure appears almost everywhere in mathematics. Groups describe the symmetry of mathematical objects. A discrete group is a space with usually countably many points which is not an interesting topological space. But people began distinguishing shapes of different groups. For example, the free group on two generators and the free abelian group of rank two should have different shapes. One may think that the shape of the free group on two generators is infinite four valent tree while the shape of the free abelian group of rank two is the lattice on the Euclidean plane. The idea of geometric group theory has been developed to describe the properties of discrete groups. For a finitely presented group, Gromov defined the hyperbolicity of it by looking at its Cayley graph and showed that the hyperbolic groups have many nice properties and it looks like free groups. When we need to investigate groups, first we may look at its abelianization, and then, for example, we may look at its nilpotent approximation. If its abelianization is the trivial group, however, then we should find another way. In this case, we have the commutator length function on the group. Bavard established the notion of stable commutator length and relate it to the space of homogeneous quasimorphisms. We can also look at the conjugation invariant norms. My interest on these invariants came from the study on diffeomorphism groups of manifolds. The identity connected components of diffeomorphism groups of compact connected manifolds have been known to be simple. I could show that for manifolds of dimensions other than 2 and 4, the commutator length function is bounded. There are many interesting infinite simple groups with unbounded commutator length functions, and it would be very interesting to find new methods to describe their shapes.

Venue: Suzuki Umetaro Hall

Event Official Language: English

General Relativity and Gravitational Waves

April 13 (Thu) at 15:00 - 16:30, 2017

Takahiro Tanaka (Professor, Division of Physics and Astronomy, Graduate School of Science, Kyoto University)

The 20th iTHES Theoretical Science Colloquium A hundred years have passed since general relativity was proposed by A. Einstein. This beautiful theory passed all experimental tests so far but almost always in a week gravity regime where perturbative expansion around flat spacetime gives a good approximation. Recent direct detection of gravitational waves by LIGO opened up a new window to test general relativity in a strong gravity regime. At the same time, cosmological observations are getting more and more accurate, which also gives a ground to test the validity of general relativity. I'd like to discuss the progress of this area in the past and what will happen in near future.

Venue: Okochi Hall

Event Official Language: English

Quantum computing by quantum annealing

January 27 (Fri) at 15:00 - 16:30, 2017

Hidetoshi Nishimori (Professor, Tokyo Institute of Technology)

The 19th iTHES Theoretical Science Colloquium Quantum annealing is a generic platform to solve a class of computational problems using quantum mechanical effects. D-Wave Systems in Canada has built hardware to realize quantum annealing and has sold several of their machine to Google, NASA, Los Alamos National Laboratory, and Lockheed-Martin, which raised a good amount of interest not just from scientific communities but also from a wider public. In this talk, I will explain the basic theoretical framework of quantum annealing, overview the current status of hardware and theoretical developments, and discuss its impact on the society in general.

Venue: Okochi Hall

Event Official Language: English