本文章最後由 iheby 於 2017-1-9 14:42 編輯
一旋等距同構在3+1維度洛倫茲愛因斯坦流形 @香港科技大學高等研究院
SEMINAR:- On 3+1 Lorentzian Einstein Manifolds with One Rotational Isometry
Differentiable manifolds whose Ricci curvature is proportional to the metric are called Einstein manifolds. Such manifolds have been central objects of study in differential geometry and Einstein's theory for general relativity, with some strong recent results.
In this talk, the speaker shall focus on positively curved 3+1 Lorentzian Einstein manifolds with one spacelike rotational isometry. After performing the dimensional reduction to a 2+1 dimensional Einstein’s equations coupled to ‘shifted’ wave maps, the speaker shall prove two explicit positive mass theorems: i) for CMC slices in expanding region, and ii) for maximal slices in stationary region.
時間：2016.12.13(二) 15:00 ~ 16:30
地點：香港科技大學 李兆基校園 盧家驄薈萃樓4樓 高研院4042室
講者：Dr Nishanth Gudapati (Yale University)
語言：英語
多模開放弦與多分枝勢 @香港科技大學高等研究院
SEMINAR:- Open String Moduli and Multi-branched Potentials
In this talk we consider type II string compactifications on Calabi-Yau orientifolds with fluxes and D-branes and analyse the F-term scalar potential that simultaneously involves closed and open string modes. We focus on the cases of type IIA orientifolds with D6-branes and type IIB orientifolds with D7-branes. In type IIA models with D6-branes this potential can be directly computed by integrating out Minkowski three-forms showing therefore a multi-branched structure along the space of lifted open string moduli in which discrete shifts of brane moduli are compensated by changes in the RR flux quanta. To obtain the correct form of the scalar potential we find strong constraints on the Kähler potential implying some interesting no-scale relations obeyed by the Kähler metric. Importantly the addition of open string moduli breaks the factorisation between complex structure and Kähler moduli spaces. We conclude by discussing the mirror dual picture of type IIB flux compactifications with D7-brane Wilson lines.
時間：2016.12.13(二) 14:00
地點：香港科技大學 李兆基校園 盧家驄薈萃樓2樓 高研院2042室
講者：Dr Gianluca Zoccarato (香港科技大學高等研究院)
語言：英語
從模擬大型強子對撞機黑洞事件為大額外維度設限 @香港科技大學高等研究院
SEMINAR:- Bounds on Large Extra Dimensions from the Simulation of Black Hole Events at the LHC
Large extra dimensions were originally proposed to solve the hierarchy problem of the Standard Model of elementary particle physics. The presence of large extra dimensions dilutes gravity, lowering the Planck scale. If large extra dimensions exist and they are large enough, the Planck scale may be as low as a few TeV’s, so that the hierarchy problem is solved. A smaller Planck scale will bring about numerous phenomenological consequences; in particular, microscopic black holes may be produced in high-energy particle collisions at this energy scale. The decay of black holes, via the Hawking effect, into elementary particles enables the detection of the black hole events, which can be used to infer the existence of large extra dimensions. In this talk, the speaker will present the simulation of microscopic black hole formation at the Large Hadron Collider with the black hole event generator CATFISH, and comparison on the simulation results with the experimental data published by the Compact Muon Solenoid collaboration in 2013 at a center of mass energy of 8 TeV. The absence of observed black hole events in the experimental data allows researchers to set lower bounds on the Planck scale and black hole masses for a number (3 - 6) of large extra dimensions. He will also introduce the physics of microscopic black holes and present the various bounds related to the black hole physics.
時間：2016.12.02(五) 16:00 ~ 17:00
地點：香港中文大學 科學館L2演講廳
講者：侯紹齊 博士 Dr Shaoqi Hou (中國武漢華中科技大學)
語言：英語
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