On Existence of Static Metric Extensions in General Relativity

Motivated by problems related to quasi-local mass in general relativity, we study the static metric extension conjecture proposed by R. Bartnik \cite{Bartnik_energy}. We show that, for any metric on $\bar{B}_1$ that is close enough to the Euclidean metric and has reflection invariant boundary data, there always exists an asymptotically flat and scalar flat {\em static} metric extension in $M = \R^3 \setminus B_1$ such that it satisfies Bartnik's geometric boundary condition \cite{Bartnik_energy} on $\partial B_1$.Comment: 20 page

Towards an exact treatment of exchange and correlation in materials: Application to the "CO adsorption puzzle" and other systems

It is shown that the errors of present-day exchange-correlation (xc) functionals are rather short ranged. For extended systems the correction can therefore be evaluated by analyzing properly chosen clusters and employing highest-quality quantum chemistry methods. The xc correction rapidly approaches a universal dependence with cluster size. The method is applicable to bulk systems as well as to defects in the bulk and at surfaces. It is demonstrated here for CO adsorption at transition-metal surfaces, where present-day xc functionals dramatically fail to predict the correct adsorption site, and for the crystal bulk cohesive energy.Comment: slightly revised version: 4 pages including 3 figures; related publications can be found at http://www.fhi-berlin.mpg.de/th/th.htm

Developing Public Rental Housing on Rural Collective Construction Land in Shanghai Suburbs: A Case of Cao’an Village in Jiading Industrial District

Since the 1990s, it is an obvious feature of Shanghai suburbs that the spatial urbanization lags behind the industrialization, with thriving demands for housing from domestic immigrant workers. By contrast, thevillages surrounding the industrial area undergo an aging process continuously, with the youth moving out of the village and many rural houses left vacant, expecting new developing opportunities and vitality urgently. If the demands from both sides can not be coordinated or guided, the indigenous villagers would likelyconstruct or enlarge the owner-occupied houses illegally arbitrarily and rent them to the immigrants, resulting in the deterioration of the living environment and social conflicts in the village. In 2017, the national policy "Pilot Scheme for Building Rental Houses on the Collective construction land" was released, in which Shanghai was selected as a pilot city. In this background, this paper aims to examine the necessity and feasibility of building public rental houses (abbr. PRH) on the rural collective construction land1 (abbr. CCL) in Shanghai suburbs and propose appropriate strategies for it. The paper first summarizesrelevant experience from villages in Dongguan and Beijing via documentation. Then combined with the author's practice of Master-planning in Jiading Industrial Zone in Shanghai, with a local village named Cao'an as the case, this paper evaluates the necessity and feasibility of constructing public rental houses in Cao'an village respectively from the village's status quo of development and the opportunities offered by its special location. Finally, drawing on the experience of Dongguan and Beijing, corresponding strategiesregarding the construction of housing-supply-system and subsequent development are proposed. This paper aims to discuss whether it's possible to, and how to use rural land reasonably to resolve the supply-demand contradiction of housing in the context of rapid industrialization of suburbs in developing countries, guide the orderly construction of suburbs, and prevent villages from becoming informal settlements

Impacts of different SNLS3 light-curve fitters on cosmological consequences of interacting dark energy models

We explore the cosmological consequences of interacting dark energy (IDE) models using the SNLS3 supernova samples. In particular, we focus on the impacts of different SNLS3 light-curve fitters (LCF) (corresponding to "SALT2", "SiFTO", and "Combined" sample). Firstly, making use of the three SNLS3 data sets, as well as the Planck distance priors data and the galaxy clustering data, we constrain the parameter spaces of three IDE models. Then, we study the cosmic evolutions of Hubble parameter $H(z)$, deceleration diagram $q(z)$, statefinder hierarchy $S^{(1)}_3(z)$ and $S^{(1)}_4(z)$, and check whether or not these dark energy diagnosis can distinguish the differences among the results of different SNLS3 LCF. At last, we perform high redshift cosmic age test using three old high redshift objects (OHRO), and explore the fate of the Universe. We find that, the impacts of different SNLS3 LCF are rather small, and can not be distinguished by using $H(z)$, $q(z)$, $S^{(1)}_3(z)$, $S^{(1)}_4(z)$, and the age data of OHRO. In addition, we infer, from the current observations, how far we are from a cosmic doomsday in the worst case, and find that the "Combined" sample always gives the largest 2$\sigma$ lower limit of the time interval between "big rip" and today, while the results given by the "SALT2" and the "SiFTO" sample are close to each other. These conclusions are insensitive to a specific form of dark sector interaction. Our method can be used to distinguish the differences among various cosmological observations.Comment: 12 pages, 7 figures, 2 tables, accepted for publication in Astronomy and Astrophysic

Wide Bandgap Organo‐lead Trihalide Perovskites for Solar Cells

Methylammonium lead trihalide perovskite (MAPbX3, where MA is methylammonium, and X is a halide)-based solar cells have been extensively investigated recently, with a demonstrated and certified solar power conversion efficiency (PCE) exceeding 20%. To further boost the PCE beyond the Schockley–Queisser limit, tandem structured solar cells have been investigated based on integrating MAPbX3 and the lower bandgap solar cells. Although the best reported efficiency for this type of tandem cells is not close to the theoretically achievable value, mixed-halide perovskite MAPbBrxI3–x is still one of the most promising candidates as the wide-bandgap light absorber for the tandem application to match the bandgap of silicon, considering its continuously tunable bandgap from 1.6 eV to 2.3 eV with different bromide incorporation ratio. However, the application of the wide-bandgap lead mixed halide perovskite based solar cells has been reported to face several challenges including high intensity of defects, light instability, phase separation, etc. This thesis aims to provide the recent work during my master program involved in the understanding of (1) the characterization of the optoelectronic property of wide-bandgap organolead mixed halide perovskite (MAPbX3), (2) bandgap tunable control of the thin film fabrication process and film post-treatment, (3) device interface and charge transport layers that dramatically influence the efficiency in the MAPbX3 devices, (4) the stability of the MAPbX3 thin films. Advisor: Jinsong Huan