سخنران: رضا جعفری، پژوهشگاه دانش های بنیادی

26 شهریور 1399
11:00 تا 12:00

Meeting's link: https://www.skyroom.online/ch/ipm-particles/school-of-particles-and-accelerators-weekly-meeting

Indico: https://indico.particles.ipm.ir/indico/event/379

سخنران: ,

26 شهریور 1399
15:30 تا 17:30

سخنران: س.ن. رسولی، دانشگاه رشت و پژوهشکده فیزیک

26 شهریور 1399
14:00 تا 15:00

Abstract:

A driven fan that spins to create a flow of air would conversely rotate, if we turn it off, and subject it to a strong external flow. This is a classic example of reciprocity between cause and effect, in a life scale experiment. In small scale hydrodynamics, however, when the Reynolds number is quite low, a swimmer (pump) would generate a net motion (flow) only if its constructing parts non-trivially follow a pattern of motion which breaks time reciprocity. Here, considering a simple and well-controlled system of two micron-sized beads, we investigate if the mentioned exchange of physical cause and effect also holds at the low Reynolds number situations. Two suspending microbeads, each held by an optical trap, are subjected to an external fluid flow. Apart from their local fluctuations, the two beads interact with each other through hydrodynamic interactions. We successfully verify that the external flow, causes the two beads to imitate the very motion they had when intended to produce a net fluid flow. Extending this exploration to a chain of many beads, i.e. a flexible polymer, we successfully confirm that the aforementioned reciprocity in physical causes and effect even for a more complicated system, like a polymer chain. Finally, we observe that the onset of external flow results in a non-trivial flow of heat along the chain! The coupling between fluid flow and the heat flow, leads us to investigate if Onsager’s reciprocal relations also hold for such a system of suspending beads/polymer in an external fluid flow.



Date: Wednesday, September 16, 2020 / چهارشنبه، ۲۶ شهریور ۱۳۹۹

Time: 14:00-15:00

To join the webinar, please follow this link:
https://www.skyroom.online/ch/schoolofphysics/condensed-matter-and-statistical-physics
and log in as guest.

Organized by: Condensed Matter and Statistical Physics Group, School of Physics (IPM)

سخنران: ندا افضلیان ، پژوهشگاه دانشهای بنيادی

26 شهریور 1399
16:00 تا 19:00

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سخنران: V. Toomani, Max Planck institute for Mathematics in Sciences

25 شهریور 1399
14:00 تا 15:00

Abstract:
In this talk, I report on a new method for obtaining a solution to the sourced Maxwell equations in Kerr in a radiation gauge. The basic structure of the solution consists of a "reconstructed part", which is given in terms of a Hertz potential, and a "corrector". The Hertz potential is a solution to a suitable Teukolsky equation.
As we demonstrate, unlike in vacuum, the corrector is in general necessary, but it can be obtained by integrating a simple transport equation. Thus, our method can be seen as a generalization of the well-known Cohen-Kegeles-Chzarnowski method to the case of source, which has been a long standing and unsolved problem.


Date: Tuesday, 8 September - ۱۸ شهریور
2 p.m. - 3 p.m.

Skyroom Link: https://www.skyroom.online/ch/schoolofphysics/hepco-group


Skype link for emergency:
https://join.skype.com/cm7iyEUWJVCf