# 中國科學家提出利用宇宙大尺度結構的形態學特徵來檢驗重力理論

【圖：互聯網；文：節錄自中國科學技術大學網頁；新聞訊息由林景明提供】研究全文刊登在已經出版的《物理評論快報》

# 教科書編成《NSS Physics Insight》

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.

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# 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.

●Zhichao Zeng
●Shek Yeung
●Ming Chung Chu

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# 磁場方向在絲狀雲中恆星形成率的影響

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.

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# 探測中等質量黑洞的可能途徑

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.

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# 磁場方向與恆星形成率之間的關聯

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.

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# 磁場作為恆星形成的指揮

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.

●Law Chi Yan
●Li Hua Bai
●Leung Po Kin
●Gu Qilao
●Zhang Yapeng

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# 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.

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# 通過緻密雙星的重力波研究其潮汐變形能力

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.

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# 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.

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