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Activity > Colloquium

Colloquiums and Seminars(2022)

ASIAA Colloquium is usually held on Wednesdays at 2:20-3:20 pm in Room 1203 of the Astronomy-Mathematics Building, NTU. All scientists are welcome to attend. Seminars on more specialized topics are also held on a regular basis.

The ASIAA-NTU joint colloquium series aims to bring to the physics/astronomy/cosmology community in ASIAA/NTU world renown researchers who will talk about the forefront development of physical sciences.

Contact: Colloquium Committee (talks_replace2@_asiaa.sinica.edu.tw)

NEXT Colloquium: 2022-02-16 Wed 14:20~15:20 [R1203]
Speaker:Chung-Yuan Mou
Topic:Water: medium of life
No. Time/Place Speaker Topic / Abstract
download PDF: download talk PDF file
12022-04-13 Wed
14:20~15:20
R1203
Frédéric Deschamps
[IEAS]
Colloquium
22022-03-16 Wed
14:20~15:20
R1203
C. Y. Cyrus Chu
[IEAS]
Colloquium
32022-02-16 Wed
14:20~15:20
R1203
Chung-Yuan Mou
[NTU]
Colloquium
Water: medium of life
42022-01-27 Thu
14:20~15:20
Online
Junsup Shim
[SNU]
Colloquium
The cosmic evolution of critical point clustering and its cosmological implication
Abstract

Critical points are special objects of a density field where the gradient of the field vanishes. They encode the topological information on the underlying density field and typically are the formation sites of large-scale structures of the cosmic web. Hence, the clustering of critical points provides information on the statistical properties of a given density field and the spatial organization of physical structures anchored to these points. In this talk, I will discuss the cosmic evolution of the clustering properties of peak-, filament-, wall-, void-type critical points focusing on both small separations and baryonic acoustic oscillation scales. A qualitative comparison with the corresponding theory for Gaussian random fields will be also discussed. Finally, I will summarize the cosmological implication of our findings and relate them to the cosmic standard rulers. Link to the talk: http://meet.google.com/ezw-onwu-zns

52022-01-19 Wed
10:00~11:00
online
Dhruba Dutta Chowdhury
[Yale]
Colloquium
Constraining Dark Matter through Gravitational Heating and Cooling Processes
Abstract

Fuzzy Dark Matter (FDM), consisting of ultralight bosons, is an intriguing alternative to Cold Dark Matter (CDM). Unlike in CDM, FDM halos consist of a central solitonic core, surrounded by an envelope of order unity density fluctuations. The envelope density fluctuations also interact with the soliton causing it to wobble and oscillate. Using novel, high-resolution numerical simulations of an FDM halo, corresponding to a particular boson mass, I will demonstrate that the gravitational potential fluctuations associated with the soliton's wobble, its oscillations, and the envelope density fluctuations dynamically heat nuclear objects (e.g., central star clusters and supermassive black holes) and galaxies. As a result, nuclear objects, initially located at rest at the soliton center, migrate outwards over time until the outward motion is counteracted by dynamical friction and an equilibrium is reached. Similarly, a galaxy undergoes significant size expansion and central density reduction over a Hubble time. Generalizing these results for other halo and boson masses and comparing them with observations (such as galaxy size-age relation, measured offsets of supermassive black holes and nuclear star clusters from the centers of their host galaxies) will be able to constrain the boson mass. After discussing FDM, I will also briefly present my work on the peculiar galaxy NGC 1052-DF2 and show what we can learn about its mass distribution from the dynamical friction-induced orbital decay of its globular clusters. Link to the talk: http://meet.google.com/kyg-mjsu-eja

62022-01-12 Wed
14:20~15:20
online
Jeremy Smallwood
[NCTS]
Colloquium
Stellar Flybys Exciting Spiral Arms in Protoplanetary Discs
Abstract

I will give an overview of the mechanics of flyby encounters and how these unbound perturbers can affect the structure of protoplanetary discs. Depending on the density of stellar clusters, stars with gaseous and dusty discs have up to a ~ 30% chance to encounter a flyby event within the first million years. The perturber will excite spiral arms during these flyby events. The spirals have a finite lifetime since the perturber is unbound. I simulate a parabolic encounter interacting with a gaseous protoplanetary disc utilizing three-dimensional smoothed particle hydrodynamical simulations. I find that the spirals can survive even when the perturber has passed periastron and is no longer interacting with the disc. Analyzing the dynamics of these excited spirals can shed light on observations of spirals in protoplanetary discs with no observed companion. *Link to the colloquium: http://meet.google.com/kyg-mjsu-eja

TEL: 886-2-3365-2200 FAX: 886-2-2367-7849
General: asiaa_replace2@_asiaa.sinica.edu.tw Media Request: epo_replace2@_asiaa.sinica.edu.tw
11F of AS/NTU Astronomy-Mathematics Building, No.1, Sec. 4, Roosevelt Rd, Taipei 10617, Taiwan, R.O.C.