本帖最後由 iheby 於 2017-5-20 11:56 編輯
香港中文大學物理系學生會議 @香港中文大學物理系
CUHK Physics Student Conference
Plenary talks
物理系學生會議：一閃一閃混星星，我奇怪你是怎樣滅亡的
Plenary talks:- Twinkle twinkle dirty stars, how I wonder how you die
In the standard theory of stellar evolution, stars die and become white dwarfs, neutron stars, or black holes, depending on their masses. Many stars go through spectacular explosion and become supernovae before their final deaths. However, this standard theory ignores possible admixture of dark matter – invisible matter that interact only gravitationally and maybe weakly - and their effects on the stellar structure, even though dark matter is known to be the dominant form of matter in the universe. the speaker will briefly introduce work done in CUHK investigating dark matter admixed stars, particularly how they die!
時間：2017.05.20(六) 09:30 ~ 10:00
地點：香港中文大學 科學館LT4
講者：朱明中 教授
語言：英語
物理系學生會議：多尺度磁場定向及其觀測
Invited talks:- Multi-scale Magnetic Field Orientation and its Observation
The role of magnetic fields is an important problem in star formation. We investigate the orientations of magnetic fields at different spatial scales by comparing the optical data with the single dish and interferometer data. We found that the magnetic field orientations are well correlated from 300 pc to 0.1-1 pc, and show a bimodal distribution when deep into ~0.01pc. In order to verify this result and further investigate the field morphology problem, our group is constructing a polarimeter, APol which will allow us to do experiment and get our own data.
時間：2017.05.20(六) 11:15 ~ 11:40
地點：香港中文大學 科學館LT4
講者：Yapeng Zhang
語言：英語
Parallel session
銀河尺度內量子效應 - 模糊暗物質宇宙模擬及大尺度結構
Talk:- Quantum Effect in Galactic Scale: Fuzzy Dark Matter Cosmological Simulation and Large Scale Structure
The Ultra-Light Axion (ULA) is a dark matter candidate with mass o(10^-22) eV and de Broglie wavelength of order kpc. Such an axion, also called the Fuzzy Dark Matter (FDM), thermalizes via the gravitational force and forms a Bose-Einstein condensate. Recent studies suggested that the quantum pressure from the FDM can significantly affect the structure formation in small scales, thus alleviating the so-called “small-scale crisis”. We develop a new technique to discretize the quantum pressure and illustrate the interactions among FDM particles in the N-body simulation. With our highly efficient algorithm, the largest scale cosmological simulation of FDM model has been performed. The non-trivial effect of quantum pressure on Large Scale Structure (LSS) has been revealed. The constraints from recent Lyman-alpha Forest observations are discussed.
時間：2017.05.20(六) 13:30 ~ 13:45
地點：香港中文大學 科學館LT4
講者：Jiajun Zhang
語言：英語
速旋中子星循雙曲軌道接近大質量黑洞之動力學
Talk:- Dynamics of Fast Spinning Neutron Stars in a Hyperbolic Orbit near a Massive Black Hole
The trajectory of a non-spinning test particle is given by the geodesics equations. However, when the test particle is spinning, it’s spin interacts with the orbit and the background curvature, giving rise to interesting dynamical behaviors, which in turn can probe the background space-time structure. In this research, we study a fast spinning pulsar orbiting in a hyperbolic orbit around a massive black hole. Millisecond pulsars are very accurate “clock” in the universe. Their abundant existence is predicted by various studies, which however, are not verified, due to the limit of pulsar timing techniques and the complicated pulse profiles of a accelerating pulsar. In this research, the spin problem in relativity and the dynamical features of such system were reviewed and studied. An orbital shift of ~100km and a velocity shift of ~1 km/s are observed, and the former will correspond to a shift of arrival time of pulse ~100μs, while the latter is related to the gravitational wave memory effect. The result of this study will provide useful insights for both the gravitational wave detector LISA, and the pulsar timing array SKA.
時間：2017.05.20(六) 13:45 ~ 14:00
地點：香港中文大學 科學館LT4
講者：Jiale Kaye Li
語言：英語
貝氏變分法到參數估算重力波天文學
Talk:- Variational Bayesian to Parameter Estimation in Gravitational Wave Astronomy
The traditional way of conducting parameter estimation in gravitational-wave data analysis is done by obtaining the posterior and evidence through Markov-Chain Monte Carlo methods. These computational methods are time consuming as they rely on wandering randomly in parameter spaces of high dimensions. Instead of randomly sampling, variational Bayesian makes use of an approximated probability distributions, which resembles the true distribution. Minimizing the differences between the true and approximated distributions can then be a more directional way of conducting parameter estimation. In this presentation, we will discuss the possibility of implementing variational Bayesian to parameter estimation in gravitational-wave data analysis.
時間：2017.05.20(六) 14:00 ~ 14:15
地點：香港中文大學 科學館LT4
講者：Adrian, K.W. Chung
語言：英語
通過緻密雙星的重力波研究其潮汐變形能力 - 包含合併前階段的效應
Talk:- Studying the Tidal Deformability of Compact Stars Through Gravitational Wave from Binary Mergers: The Effect of Including Post-Merger Phase
The recent discoveries of binary black holes by gravitational-wave detection hint at the opportunity of detecting gravitational-wave signals from binaries consisting of compact stars. Binaries typically undergo three stages during coalescence: inspiral, merger and post-merger. Information on the compact stars’ matter is encoded throughout the gravitational-wave signal, detections of the signal can constrain the equation of state of ultradense matter. The feasibility of constraining the equation of state through gravitational-wave detections by second and future generation detectors have been studied using the inspiral and post-merger stages separately. We present the effect and the possible improvement in constraining the equation of state by using a toy model of binary mergers, which consists of inspiral and post-merger.
時間：2017.05.20(六) 14:15 ~ 14:30
地點：香港中文大學 科學館LT4
講者：Peter, Tsun Ho Pang
語言：英語
從併合中的高質量雙黑洞尋找重力波
Talk:- Searching for Gravitational Waves from the Coalescence of High Mass Black Hole Binaries
GstLAL is a search pipeline used by LIGO to search for gravitational waves from the coalescence of compact binaries (neutron stars and/or black holes), which can be operated in on-line and/or off-line configuration. Before the second observing run (O2), the parameter space covered by GstLAL consisted of binaries with component masses m1,m2 ≥ 1M⊙ (M⊙ is the solar mass) and total mass 2M⊙ ≤ M1+M2 ≤ 100M⊙. In this project, we aim to increase the upper bound of the total mass to 600M⊙ to search for gravitational waves from intermediate mass black holes (IMBH). Simulated signal injections with real noises were used to evaluate the sensitivity of GstLAL when decreasing the lower frequency cut-off to observe signals from IMBH since they merge at a lower frequency. We experimented various techniques such as different bank splitting and h(t) gating schemes to optimize the performance and sensitivity after the inclusion of IMBH signals in a search. This would enable us to detect more gravitational wave signals from the coalescence of black holes with higher masses in real time gravitational wave detection.
時間：2017.05.20(六) 14:30 ~ 14:45
地點：香港中文大學 科學館LT4
講者：Ka Lok Lo
語言：英語
磁場作為恆星形成的指揮 - 一個觀測角度
Talk:- Magnetic field as a Conductor in Star Formation - An Observational Perspective
The role of the magnetic field, among other mechanisms (gravity & turbulence) in star formation remain uncertain. However, within the last decade, multi-scales observational studies have started to show that magnetic field has an important role in regulating star formation environment from Cloud through the filament to core scale and consequence star forming properties. In this presentation, we briefly review observational signatures of the dynamically important magnetic field at large/small scales. We will also briefly present multi-scale observational evidence.
時間：2017.05.20(六) 14:45 ~ 15:00
地點：香港中文大學 科學館LT4
講者：
●Law Chi Yan
●Li Hua Bai
●Leung Po Kin
●Gu Qilao
●Zhang Yapeng
語言：英語
探測中等質量黑洞的可能途徑 - 經重力透鏡效應的重力波
Talk:- A Possible Way to Probe Intermediate Mass Black Hole – Gravitational Lensing of Gravitational Wave
Existence of intermediate mass black hole is a mystery in astronomy. Theoretically it should exist, but it hasn’t been confirmed by observation yet. Since intermediate mass black hole is a possible candidate of gravitational lens, its lensing effect on gravitational wave in diffraction limit could be a direct observational evidence. Basic analysis shows the lensing effect is observable within LIGO detectability. Serious Bayesian analysis is ongoing to investigate under what circumstances we can confirm that the signal indicates an intermediate mass black hole.
時間：2017.05.20(六) 15:15 ~ 15:30
地點：香港中文大學 科學館LT4
講者：Lai Kwun Hang 及 Otto Hannuksela
語言：英語
磁場方向與恆星形成率之間的聯繫
Talk:- The Link between Magnetic-Field Orientations and Star Formation Rates
Star formation rates (SFR) is a key component in modern star-formation models, which mainly involve gravity, turbulence and, in some cases, magnetic fields (B-fields). But the connection between B-fields and SFR has never been observed. A comparison between the survey of SFR and a study of cloud-field alignment – which revealed a bimodal (parallel or perpendicular) alignment – shows that clouds with lower SFR per solar mass are tend to perpendicular to the B-fields. This might be an evidence of B-fields being a primary regulator of SFR. We used B-fields data from starlight method and 353 GHz dust thermal emission, which comes from by Planck mission’s all sky survey.
時間：2017.05.20(六) 15:30 ~ 15:45
地點：香港中文大學 科學館LT4
講者：GU Qilao
語言：英語
磁場方向在絲狀雲中恆星形成率的效應
Talk:- The Effect of Magnetic Field Orientation on Star Formation Rate in Filament Clouds
With the rapid growth of computational power, numerical simulation has become more and more important in astrophysical researches in the last few decades. In this presentation, we will briefly introduce the simulation we are adopting in our group, as well as one of the currently undergoing simulation projects, aiming to reveal the effect of magnetic field orientation and other effects on star formation rate in filament clouds. The importance of magnetic field orientation in star formation has been gradually realised in the recent decades. However, the effect of different orientations on star formation rate in particular types of filaments is still yet to be understood, which will be the central topic of the project.
時間：2017.05.20(六) 15:45 ~ 16:00
地點：香港中文大學 科學館LT4
講者：GUO Zitan
語言：英語
教科書編成《NSS Physics Insight - A Short Introduction to Special Relativity》
Talk:- NSS Physics Insight - A Short Introduction to Special Relativity
We have developed a textbook (NSS Physics Insight – A short introduction to Special Relativity) teaching Secondary Senior Form students Special Relativity. There are 6 major chapters about Special Relativity included, together with 4 supplementary chapters providing required mathematics skills, like limits and differentiation, integration, vectors and matrices, for students to tackle Special Relativity problems. Time dilation, length contraction, Lorentz transformation and the application of Spacetime diagrams are included in the textbook. We adopted the example-based approach in the textbook, that is, we provided examples for students to follow and some follow-up challenges for them to apply what they have learnt. To arouse interest of the readers, we also made use of comics and dialogues to exemplify the physics concepts and theories. Problem sets are available at the end of each chapter, in which students can test their understanding. It is notable that most of the problems in the textbook were originally designed, with extra features like problems are implemented based on novels, increasing difficulty of problems of similar situations. A full solution manual is also available for students to check their answers and steps. Supplementary notes and explanation are also provided in the manual.
時間：2017.05.20(六) 16:00 ~ 16:15
地點：香港中文大學 科學館LT4
講者：Li Ka Yue Alvin 及 Pang Yiu Yung
語言：英語
具有限化學勢的大質量中微子於宇宙擴張史及大尺度結構的影響
Talk:- Influence of Massive Neutrinos with a Finite Chemical Potential on the Cosmic Expansion History and Large Scale Structure
Due to their high abundance, massive cosmic neutrinos would have a significant influence on cosmology, especially in terms of large scale structure. Ever since the discovery of neutrino oscillation, which confirmed that neutrinos have finite masses, many efforts have been made to constrain neutrino masses from cosmology. However, none of them has considered the possibility of a finite chemical potential, if the neutrinos are not majorana fermions. The work would be the first one to analyse the combined effect of masses and chemical potentials of neutrinos on matter power spectrum of large scale structure, through two physical processes, their influence on the cosmic expansion history, and the neutrino free-streaming. The result would serve as a correction to the constraints of neutrino masses from large scale structure.
時間：2017.05.20(六) 16:15
地點：香港中文大學 科學館LT4
講者：
●Zhichao Zeng
●Shek Yeung
●Ming Chung Chu
語言：英語
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