## Colloquium

24th iTHES/iTHEMS Colloquium

Date: 15:00 ~ December 19th (Tue.)

Venue: Okochi Hall + TV at R511, AICS & S704, Kobe)

Lecturer: Prof. Jun'ichi YOKOYAMA (RESCEU, The University of Tokyo)

Title: Approaches to inﬂationary cosmology

Abstract:

Inﬂation in the early universe is an indispensable ingredient of modern cosmology which not only solves long standing problems such as horizon, ﬂatness, and monopole/unwanted relics problems but also provides the origin of tiny density ﬂuctuations which have evolved to the observed large-scale structures. Now the standard paradigm of inﬂation is that the accelerated expansion is realized when a scalar ﬁeld, dubbed as the inﬂaton, slowly rolls over its potential down to a global minimum in a time scale longer than the cosmic expansion time. The remarkable feature of the slow-roll inﬂation is that it can not only explain the global properties of the observed Universe, but also provide seeds of density and curvature ﬂuctuations out of the quantum ﬂuctuations of the inﬂaton ﬁeld in exponentially expanding space.

In fact, the slow-roll inﬂation driven by a potential is not the only inﬂation scenario prevailing today, and there are two alternatives. One is models realizing inﬂation without introducing any inﬂaton ﬁeld but modifying gravity from the Einstein's general relativity. Starobinsky was the ﬁrst to show that quasi-exponential expansion and graceful exit therefrom could be realized by incorporating higher-order curvature terms in the action based on quantum corrections. Nowadays its simpler version including square scalar curvature term besides the Einstein action is referred to as the Starobinsky model. The other alternative is models which make use of a scalar ﬁeld with a higher-order kinetic function. If we can realize a state with a constant canonical kinetic function its energy density can have the same equation of state as the cosmological constant to drive exponential inﬂation. Such models are referred to as k-inﬂation.

All these models can be regarded as a subclass of the generalized G-inﬂation model which is the most general theory of single-ﬁeld inﬂation with its ﬁeld equations given by second-order diﬀerential equations as with most of the other theories of fundamental physics.

Turning back to the potential-driven models, in order to realize inﬂation with proper amplitude of ﬂuctuations, we must have a suﬃciently ﬂat potential. The conventional way to protect this ﬂatness against quantum correction has been to make use of supersymmetry. Recently, however, we have shown that higher-order derivative interactions typical in generalized G-inﬂation can also make the potential eﬀectively ﬂat even though they contain much larger values of parameters than usually assumed. This provides another arena for model building of realistic inﬂation.

I will introduce these new trends in inﬂationary cosmology.

23rd iTHES/iTHEMS Colloquium

Date: 15:00 ~ October 30th (Mon.)

Venue: 2F Large mtg. rm, RIBF Bldg., + TV at R511 (AICS, Kobe)

Lecturer: Prof. Hiroshi Suito (Tohoku Univ.)

Title: Simulations and machine learning going hand in hand for clinical medicine

Abstract:

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.”

22nd iTHES/iTHEMS Colloquium

Date: 15:00 ~ July 28th (Fri.)

Venue: Suzuki Umetaro Hall, + TV at R511 (AICS, Kobe)

Lecturer: Prof. Zhenghan Wang (UCSB)

http://web.math.ucsb.edu/~zhenghwa/

Title: Introduction to topological quantum computing

Abstract:

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.

21th iTHES Colloquium

May 18th (Thur.) 15:30-

"Shapes of discrete groups"

Prof. Takashi Tsuboi

(University of Tokyo & RIKEN iTHEMS)

http://www.ms.u-tokyo.ac.jp/teacher/tsuboi.html

https://ithems.riken.jp/about/deputy-program-director-takashi-tsuboi/

Place: Suzuki Umetaro Hall (Bldg. S01, Wako) + TV at 305-2(AICS, Kobe), S704(IIB, Kobe)

20th iTHES Colloquium

April 13th (Thur.) 15:00-

"General relativity and gravitational waves"

Prof. Takahiro Tanaka (Dept. of Physics, Kyoto University)

http://www2.yukawa.kyoto-u.ac.jp/~takahiro.tanaka/index.html

Place: Okochi Hall (Bldg. C32, Wako) + TV at 6F Lecture Hall(AICS, Kobe), S704(IIB, Kobe)

19th iTHES Colloquium

January 27th (Fri.) 15:00-

"Quantum computing by quantum annealing"

Prof. Hidetoshi Nishimori (Tokyo Institute of Technology)

http://www.stat.phys.titech.ac.jp/nishimori/index-j.html

Place: Okochi Hall (Bldg. C32, Wako) + TV at 6F Lecture Hall(AICS, Kobe)

18th iTHES Colloquium

October 21st (Fri.) 15:30-

"Olfactory Computations in the Brain"

Dr. Hokto Kazama (RIKEN Brain Science Institute)

http://www.brain.riken.jp/en/faculty/details/23

Place: Okochi Hall (Bldg. C32, Wako) + TV at Room 511 AICS (Kobe)

Abstract: All living organisms make decisions and actions according to the sensory information collected from the environment. Sensory information is encoded by neurons in the periphery and processed progressively in neuronal circuits in the brain. In this talk, I will focus on the sense of smell and discuss computations in the olfactory circuit that may underlie innate and experience-dependent perception of odors.

17th iTHES Colloquium

Date: July 14 (Thu.), 2016, 15:00-

"Topological Phases in Condensed Matter"

Prof. Shuichi Murakami (Tokyo Institute of Technology)

Place: Okouchi Hall

http://www.stat.phys.titech.ac.jp/murakami/etop.html

16th iTHES Colloquium

Date: April 19 (Tues.) 15:00~

"Exploring the world of microswimmers: a theoretical approach"

Dr. Kenta Ishimoto (RIMS, Kyoto Univ.)

http://www.kurims.kyoto-u.ac.jp/~ishimoto/en/Home.html

Place: Okouchi Hall

Abstract:

Under the microscope, we can observe a large variety of swimming microbles rich in morphological and ecological diversity. The swimming is a vital concern for such primitive organisms to survive, and they appear to adapt to the environmental constraints of hydrodynamics at low Reynolds number. This can be highlighted by the scallop theorem, a consequence of the symmetry in the equations of the system, where the inertia is negligible as in Aristotelean physics. In this talk, after a brief introduction to the hydrodynamics in the microworld, I will show how the theory works in the biological microswimmers such as bacteria, planktons and spermatozoa. Further examples will be provided in our recent studies on cell boundary accumulation phenomena and sperm guidance in mammalian fertilisation.

15th iTHES Colloquium

Date: March 17th (Thu.) 13:00-

"Modeling the transmission dynamics of Middle East respiratory syndrome (MERS) in the Repubic of Korea"

Prof. Hiroshi Nishiura (University of Tokyo)

Place: Nishina Hall (E02)

Abstract: A multi-hospital outbreak of Middle East respiratory syndrome (MERS) occurred in the Republic of Korea from May-July 2016. Committed to maintaining regional security, the epidemiological modeling team at the University of Tokyo, including Hiroshi Nishiura, responded to the epidemic through research activities, elucidating the natural history and transmission dynamics. Multitudes of research question were answered in two month period with eight independent submissions and these research outcomes were provided shared in real-time. This talk briefly introduces each modeling study and its contribution to public health, thereby helping the author to overview future research tasks to be achieved anticipating similar events of emerging infectious diseases in Japan.

14th iTHES Colloquium

January 7th (Thu.) 15:00-

"Sparse modeling and data-driven science"

Prof. Masato Okada (University of Tokyo)

Place: Okochi Hall (C32)

Abstract:

I introduce a project, called “the Initiative for High-dimensional Data-Driven Science through Deepening of Sparse Modeling ”. The aim of this project is to establish a novel framework to make the tight connection of information science to the original purpose of data analysis derived from various scientific disciplines, namely, data-driven science. We consider sparse modeling as a key technology of the data-driven science. In this talk, I mention basic concept of the sparse modeling, and concretely explain that sparse modeling promotes extraction of latent structure in electrophysiological data. Through the project, we have become convinced that the three levels pointed out by David Marr give a novel insight into data-driven science, and propose three levels of data-driven science [1].

[1] Igarashi, Nagata, Kuwatani, Omori, Nakanishi-Ohno and Okada, “Three Levels of Data-Driven Science”, submitted to *Proc. of HD3-2015*, 2015.

13th iTHES Colloquium

November 10th (Tue.) 15:00-

"Complex Systems Modeling and its Applications"

Prof. Kazuyuki Aihara (The University of Tokyo)

http://www.sat.t.u-tokyo.ac.jp/aihara/

Place: 2F Large mtg.rm, Main Cafeteria (Bldg. C61)

Abstruct:

In this talk, I review our recent reseach on complex systems modeling and its transdisciplinary applications. First, I explain about a platform for mathematical modeling of complex systems, based on complex systems control theory, complex network theory, and big data analysis. Second, I illustrate examples of its transdisciplinary applications such as dynamical network biomarkers for preemptive medicine, transitive dynamics of the primate prefrontal cortex, and an electronic AD converter with beta expansion.

**iTHES Colloquium**

September 15th (Tue.) 15:00-

"Numerical Weather Prediction: Chaos, Predictability and Data Assimilation"

Dr. Takemasa Miyoshi (RIKEN AICS)

Place: 2F Large mtg.rm, Main Cafeteria (Bldg. C61)

Abstract:

Contemporary weather forecasting is based on numerical simulations with supercomputers, i.e., numerical weather prediction (NWP). The weather system is chaotic, and data assimilation plays a central role in predicting the chaotic weather by synchronizing a numerical simulation with the real world. Data assimilation integrates simulations (i.e., virtual world on computers) and real-world data based on statistical mathematics and dynamical systems theory, and brings synergy. Although data assimilation for large-scale computational problems has been evolving extensively in the field of NWP, data assimilation is a general approach potentially applied to a wide range of simulation studies. This lecture provides an introduction to NWP and data assimilation, and discusses the future perspectives of data assimilation research in the forthcoming “Big Data” and “Big Simulation” era.

**iTHES Colloquium**

July 6 (Mon) 15:30-

"Thermodynamics of Information Processing"

Prof. Takahiro Sagawa

(Dept. of Applied Phys., Univ. of Tokyo)

http://noneq.c.u-tokyo.ac.jp/index_e.html

place: Nishina Hall

(Building 13, E-4 area in the following map)

http://www.riken.jp/~/media/riken/access/wako-map/map2_p_150105.pdf

abstract:

In this decade, thermodynamics of information has attracted renewed attentions in light of modern nonequilibrium statistical mechanics, leading to a new field of "information thermodynamics." This topic is related to the foundation of the second law of thermodynamics, which dates back to the thought experiment of "Maxwell's demon" in the nineteenth century. In this talk, I will review the recent progress in information thermodynamics, in both terms of theory and experiment. Theoretically, I will focus on the generalization of the second law of thermodynamics to information processing, where information contents and thermodynamic variables are treated on an equal footing. I will also talk about our experimental realization of Maxwell's demon with a single electron. Moreover, I will talk about our recent result on an application of information thermodynamics to biological signal transduction of E. Coli chemotaxis.

iTHES Colloquium

April 8, 2015, 16:00 -

Prof. Madan Rao (Simons Centre, NCBS)

"Active Composite Cell Surface : Implications to molecular organization, shape and information processing"

web page: http://ncbs-theobio2.riken.jp/Organizers:

place: 2nd floor of the main cafeteria ( http://ncbs-theobio2.riken.jp/access/ )

**iTHES Colloquium**

Title: Cell Mechanics: from single cell to multi-cellular dynamics

Date and time: 2pm-, Jan. 8 (Thur.), 2015

Place: Suzuki Umetaro Hall

Lecturer: Prof. M. Sano (Univ. of Tokyo)

http://daisy.phys.s.u-tokyo.ac.jp/index.htm

WITH

H. Liang (iTHES-phys)

R. Johansson (iTHES-cond)

T. Okada (iTHES-bio)

Geometry before Euclid: How Life Explored and Conquered the Dimensionality of 3-Space"

delivered by Robert Sinclair

on June 18th, 2014

"Hanbury Brown--Twiss Intensity Interferometry: from stars to nuclei to atoms and electrons"

delivered by Gordon Baym

on April 8th, 2014

"An answer to the "diversity-stability debate" in community ecology"

delivered by Kei Tokita

on January 31st, 2014

"The Quantum Universe"

delivered by Hitoshi Murayama

on December 4th, 2013

"From Origin of life to systematization of Astrobiology "

delivered by Shigenori Maruyama

on November 5th, 2013

"Physics of quantum measurement and its applications"

delivered by Masahiro MORIKAWA

on July 9th, 2013

"Quantum information processing for coherent communication"

delivered by Akira FURUSAWA

on May 31st, 2013

"First principles simulation for photo-excitation and carrier splitting in condensed matters"

delivered by Yoshiyuki MIYAMOTO

on January 7th, 2013

"Structured hybrid models and Hilbert's thirteenth problem"

delivered by Bernold FIEDLER

on October 4th, 2012

"Momentum transfer in non-equilibrium steady states"

delivered by Ken SEKIMOTO

on September 6th, 2011

"New multiconductor transmission-line and the mechanism of noise reduction"

delivered by Hiroshi TOKI

on June 29th, 2011

"Information Geometry and Its Applications"

delivered by Shun-ichi AMARI

on March 9th, 2011

"Symmetry and asymmetry in quantum transport"

delivered by Seth Lloyd

on January 12th, 2011

**"How the superstring works"**

delivered by Hisao SUZUKI

on December 8th, 2010

"Fine Structure Constant, Electron Anomalous Magnetic Moment and Quantum Electrodynamics"

delivered by Toichiro Kinoshita

on November 17th, 2010

"On the development of human body simulator for the next-generation supercomputer"

delivered by Shu Takagi

on July 14th, 2010

"Recent Advances in Molecular Theory"

delivered by Kimihiko Hirao

on May 12th, 2010

"Gamma-ray Signal from Earth-mass Dark Matter Microhalos"

delivered by Toshikazu Ebisuzaki

on January 20th, 2010

"Spontaneous breaking of supersymmetry"

delivered by Hiroshi Suzuki

on Novermber 18th, 2009

"Structure of regulatory networks and dynamics of bio-molecules"

delivered by Atsushi Mochizuki

on June 17th, 2009

"Symmetry breaking and phase transition in nuclei"

delivered by Takashi Nakatsukasa

on April 15th, 2009

"Topological Insulators"

delivered by Akira Furusaki

on February 4th, 2009

"All-atom molecular dynamics simulations of membrane proteins in lipid bilayer"

delivered by Yuji Sugita

on October 15th, 2008

"The Frontiers of Superstring Theory:

D-branes and new perspective of our world"

delivered by Koji Hashimoto

on June 18th, 2008

"Superconducting qubits: Quantum Circuits as Artificial Atoms"

delivered by Franco Nori

on April 16th, 2008