vol. 69 | iTHES

Vol. 69, February 23rd, 2015


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

Paper of the week

Valenti Bosch-Ramon, Maxim Barkov and Manel Perucho.


"Orbital evolution of colliding star and pulsar winds in 2D and 3D; effects of: dimensionality, EoS, resolution, and grid size"

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.


Article on iTHES in RIKENETIC Online
A special report, "How does Google translate? " is now posted in the Feb. (2015) issue of RIKENETIC which is an English-language in-house newsletter published monthly by the Global Relations Office and distributed to all RIKEN campuses. Take a look at the report and the photo from http://rikenetic.intra.riken.jp/?p=2913

Dr. Robert Johansson who is an ithes researcher (ithes-cond team) since the fall of 2013 is leaving for the company RAKUTEN ( http://en.wikipedia.org/wiki/Rakuten ).
Robert has been an active member both as the organizer and the participant of the ithes seminars, colloquiums, coffee-meetings etc.
The photo was taken at the time of his farewell speech in the ithes coffee meeting on Feb..20, 2015.
We all hope that Robert will enjoy his new job in RAKUTEN and hopefully come back to RIKEN to give a talk at
iTHES academic-industrial lecture in the near future.

Upcoming Events

Mini-symposium on "Theoretical Biology"
Feb. 23 (Mon), 13:30-16:45, 2015
13:30-15:00 Prof. Yoh Iwasa (Kyushu University).
"Cultural evolutionary dynamics: illustrated by Hinoeuma superstition in Japan and illegal logging of tropical forests"
15:15-16:45 Prof. Nanako Shigesada (Nara Women’s University)
"Travelling waves of invasive species in periodic patchy environments: effects of diffusion, taxis and population pressure"
Place: Large meeting room in the 2nd floor of the main cafeteria, RIKEN

iTHES Seminar
Feb.26 (Thurs.) 13:30-
H. Tsukaya (Univ. Tokyo)
"Unsolved enigmas on mechanisms of unifacial leaf morphogenesis" (in Japanese)
Place: RIKEN Wako Campus, Bioscience building S406

Feb. 27 (Fri.), 14:00-
Title: "An electromechanical Ising Machine"
Speaker: Dr. Imran Mahboob (NTT Basic Research Labs)
Place: Main Research Building Seminar room 535-537 (located in the Fifth Floor)
Ref.:I. Mahboob, et al., Two-Mode Thermal-Noise Squeezing in an Electromechanical Resonator, Phys. Rev. Lett. 113, 167203 (2014)

iTHES international workshop
April 7 - 10, 2015
iTHES-NCBS 2nd Joint Meeting on "Theoretical Biology"
Venue: RIKEN Wako Campus
A. Mochizuki (ithes-bio), Y. Sugita (ithes-bio), T. Hatsuda (ithes-phys), M.Thattai (NCBS)
Contact: A. Mochizuki (mochi@riken.jp)
Sponsors: RIKEN iTHES and Simons Centre at NCBS (http://theory.ncbs.res.in/)

Event report

On 16th Feb., Dr. Tomoya Takiwaki who is an iTHES associate presented a talk on supernova explosion using K-Computer at the Google company in Roppongi, Tokyo. About 50 people including 13 from iTHES attended the seminar making the seminar room full of people. Takiwaki-san succeed to have a good relation with the googlers because:
(1) We understood the atmosphere of google.
We found that many of googlers have Master Degrees and some have Ph.D. So we
could enjoy lots of scientific questions and answers. Especially, they are interested
in algorithm, data representation, and code writing. 
(2) We can share interest.
The Google company has cloud server service. Googlers wanted to know whether the
Supernova simulations can be run in the server.
Takiwaki-san also reported the exciting event in his facebook. Then he got nice responses such as:
(A) 43 people said “it’s nice!”.
(B) A president of a venture company invited him to present a talk.
We will keep in touch with Google, and we will have a TV meeting very soon on possible collaborations between iTHES & Google, using Google Hangout.

Paper of the week

"Orbital evolution of colliding star and pulsar winds in 2D and 3D; effects of: dimensionality, EoS, resolution, and grid size"
Valenti Bosch-Ramon, Maxim Barkov and Manel Perucho.
submitted to A&A

The structure formed by the shocked winds of a massive star and a non-accreting pulsar in a binary system suffers periodic and random variations of orbital and non-linear dynamical origin. The characterization of the evolution of the two-wind interaction region is necessary to understand the rich phenomenology of these sources. For the first time, we simulate in 3 dimensions the interaction of isotropic stellar and relativistic pulsar winds along one full orbit, on scales well beyond the binary size. We also investigate the impact of grid resolution and size, and of different state equations.
We carry out, with the code PLUTO, relativistic hydrodynamical simulations in 2 and 3 dimensions of the interaction of a slow dense wind, and a mildly relativistic wind with Lorentz factor 2, along one full orbit in a region up to $\sim 100$ times the binary size. The 2-dimensional simulations are carried out with equal and larger grid resolution and size, and one of them is done with a more realistic equation of state, than in 3 dimensions. The simulations in 3 dimensions confirm previous results in 2 dimensions, showing: a strong shock induced by Coriolis forces that terminates the pulsar wind, closing it in all directions; strong bending of the shocked-wind structure against the pulsar motion; and the generation of turbulence. The shocked flows are also subject to a faster development of instabilities in 3 dimensions, which enhances the presence of shocks, two-wind mixing, and large-scale disruption of the shocked-wind structure. In 2 dimensions, higher resolution simulations confirm lower resolution results, simulations with larger grid sizes strengthen the case for the loss of global coherence of the shocked-wind structure, and simulations with two different equations of state yield very similar results. In addition to the Kelvin-Helmholtz instability, discussed in the past, the Richtmyer-Meshkov and the Rayleigh-Taylor instabilities are likely acting together on the shocked flow evolution. Simulations in 3 dimensions (See fig.1) confirm that the interaction of stellar and pulsar winds yields structures that evolve non-linearly and get strongly entangled. The evolution is accompanied by strong kinetic energy dissipation, rapid changes in flow orientation and speed, and turbulent motion. The results of this work strengthen the case for the loss of global coherence of the shocked-wind structure on large scales.


Prof. Adam Miranowicz (Adam Mickiewicz University, Poland)
Quantum Information, Quantum and Atom Optics, Nanoscience, Entanglement Theory, Non-classicality
January 10th to March 10th, 2015.
Main Research Building 3F, room 308 (ex. 3352).