vol. 86 | iTHES

Vol. 86, June 29th, 2015


  • Announcement
  • Upcoming Events
  • Event report
  • Paper of the week

Paper of the week

Tachikawa M. and Mochizuki A.


Nonlinearity in cytoplasm viscosity can generate an essential symmetry breaking in cellular behaviors

From the Office

The office of iTHES assistant, Ms.Chikako Oota is situated at the second floor of the main research building, room # 246. The extension number is 3261. She will be at the office from 10 a.m. to 16 p.m.


Press Release (2015/6/26)

The paper "Quantum spin Hall effect of light", Science, vol. 348 (2015) 1448,
by Konstantin Y. Bliokh, Daria Smirnova, and Franco Nori,
was press released on June 26, 2015.

Konstantin is a former ithes research fellow (now he is in CEMS) and Franco Nori is currently the team leader of ithes cond-mat team.

Maxwell’s equations, formulated 150 years ago, ultimately describe properties of light, from classical electromagnetism to quantum and relativistic aspects. The latter ones result in remarkable geometric and topological phenomena related to the spin-1 massless nature of photons. By analyzing fundamental spin properties of Maxwell waves, we show that free-space light exhibits an intrinsic quantum spin Hall effect surface modes with strong spin-momentum locking. These modes are evanescent waves that form, for example, surface plasmon-polaritons at vacuum-metal interfaces. Our findings illuminate the unusual transverse spin in evanescent waves and explain recent experiments that have demonstrated the transverse spin-direction locking in the excitation of surface optical modes. This deepens our understanding of Maxwell’s theory, reveals analogies with topological insulators for electrons, and offers applications for robust spin-directional optical interfaces.

Upcoming Events

iTHES Colloquium
July 6 (Mon) 15:30-
"Thermodynamics of Information Processing"
Prof. Takahiro Sagawa (Dept. of Applied Phys., Univ. of Tokyo)
place: Nishina Hall (Building 13, E-4 area in the following map)
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.

Event report

iTHES-Google Joint seminar on June 22, 2015.

Dr. Masato Taki (ithes research fellow) gave a talk at the iTHES-Google joint seminar held at Google Japan in Roppongi.
This is the 3rd seminar of this series.

He gave a talk on his recent paper,
"Optical Lattice Model Towards Nonreciprocal Invisibility Cloaking",
by Tomohiro Amemiya, Masato Taki, Toru Kanazawa, Takuo Hiratani, Shigehisa Arai, IEEE journal quantum electronics, Vol. 51, No. 3, pp.6100110, doi: 10.1109/JQE.2015.2389853, which was press released in

Title of his talk was "Invisibility cloaking, curved space and optical lattice", with the following abstract. In this talk I give an overview on recent progress on designing invisibility cloaking devices. Such a device first designed by utilizing the physical theory for electromagnetic dynamics on curved space. This idea has been widely studied and generalized, however, almost all proposed devices are symmetric in the space that cloaked person is also separated from outside and cannot see exterior. After reviewing these backgrounds, I explain our proposal for a design theory of asymmetric invisibility cloaking for an optical camouflage device with unidirectional transparency in which a person in the cloak can see the outside but cannot be seen from the outside. Existing theories of designing invisibility cloaks so far cannot be used for this purpose. To realize nonreciprocal cloaking, we employ the theory of effective electromagnetic field for photons, which is an extended version of the theory of effective magnetic field for photons.

More than 30 Googlers attended the seminar from 3pm at the 27F of the Mori Tower. Many questions and lively discussions took place during the seminar. After the talk, iTHESers (M. Taki (RIKEN), T. Hatsuda (RIKEN), Herman Lee (JAXA), T. Amemiya (TIT)) dropped by the Google Cafe in the 27F and enjoyed good espresso and coffee.

The photo taken in front of the Google Cafe is M. Taki (left) from iTHES and Yoshikiyo Kato (right) from Google who was in charge of the seminar this time.

Image Recognition Technology

Dr. Takeshi Nagata (Mizuho Information & Research Institute)
gave an ithes lunch talk on "Forefront Image Recognition Technology" from 12:30- on June 26, 2015 at our ithes common room 248 in the main research building.

After a self-introduction about his background (Ph.D in theoretical nuclear physics), he explained the essential idea of the Image Recognition with Deep Leaning. Then he showed several examples of its application; the defect detection of the accelerating cavity for ILC, the defect detection of the automobile's cast components, simulations of the aging effects of the wanted person's photo, and the image reconstruction from blurred photos.

There were many questions asked by the ithes members during and after his talk from various points of view (astronomy, biology, particle physics etc). Further questions, requests for more information etc? can be sent to Dr. Nagata directly, takeshi.nagata_at_mizuho-ir.co.jp.

Paper of the week

Cytoplasm of cells are highly viscous, and sometimes show nonlinear response to deformations. How can the nonlinearity relate to the cellular functions In this paper, we focus on the locomotion of an amoeboid cell and investigate the relation with the nonlinear viscosity.
Plasmodium of Physarum polycephalum is a huge amoeboid cell. Gel state cytoplasm of the cell forms a large network of branching tubes, and sol state cytoplasm flows in the tubes. The tube radius is about 0.1 mm and the expanse of the cell can grow up to one meter. Each peripheral of the network periodically contracts, which acts as a pump to generate shuttle streaming of cytoplasm sol flow.
Imagine a dumbbell shaped cell (Fig. 1); two pumps are connected with one straight tube. In this paper we show that if two pumps are identical and only the phases of oscillations are different, nonlinear viscus cytoplasm sol can be transported one pump to the other depending on the phase difference. This transport is not generated with linear viscus cytoplasm. Thus, this is the nonlinearity induced symmetry breaking in the cytoplasm transport. Since the cytoplasm transport determines the direction of the cell migration, we conclude that the nonlinearity in cytoplasm viscosity can control the cellular locomotion.

Fig. 1 Shape of a dumbbell formed cell (A) and time averaged flow of cytoplasm sol against the phase difference between two periodic pumps (B).

Tachikawa M. and Mochizuki A. (2015) Nonlinearity in cytoplasm viscosity can generate an essential symmetry breaking in cellular behaviors. J. Theor. Biol. 364, 260-265.