A-CUHK402/19
Fermi Energy Tuning in Topological Materials

Hong Kong Principal Investigator: Prof Goh Swee-kuan (The Chinese University of Hong Kong)
French Principal Investigator: Prof Pourret Alexandre (PHELIQS CEA/University Grenoble Alpes)

This joint project aims to investigate the electronic states of a wide range of topological materials through a careful experimental tuning of the Fermi energy. Topological quantum materials host Dirac points in the electronic band structure. The electronic properties are sensitively dependent on the precise location of the Fermi energy, which can be controlled by hydrostatic pressure, uniaxial pressure, chemical doping, electric field and dimensionality. Unconventional behavior related to massless chiral fermions occurs only if the Fermi energy is close to these Dirac points. This project seeks to achieve such systematic tuning of the Fermi energy by employing multiple tuning parameters, and to probe the underlying electronic structure via high magnetic field straddling the quantum limit. The formation of the CUHK-Grenoble consortium will pull together first-class resources, which are already available in the laboratories in Hong Kong and Grenoble, for a concerted, ambitious, and systematic investigation of topological materials via Fermi energy tuning. The project will involve synthesis of materials, design of the experiment for band structure tuning, and measurements of the resultant systems using electrical and thermal transports at millikelvin temperatures and high magnetic field up to 36 T. These efforts offer the prospect of extracting fundamental physics and the functionalization of these exciting materials. The results of this project will be of interest to the community of condensed matter physics and device engineering.

A-HKBU203/19
ALLOWAP: Algorithms for large-scale optimization of wave propagation problems

Hong Kong Principal Investigator: Dr Kwok Wing Hong Felix (Hong Kong Baptist University)
French Principal Investigator: Prof Halpern Laurence (Université Paris 13)

The goal of this project is to design and develop large-scale parallel algorithms for dealing with optimization problems involving wave phenomena. Such problems arise in many practical applications: two examples are in seismic inversion, where one tries to deduce the geology of rock formations that best fits the available seismic data, and in wave localization, which can be used to improve the efficiency of wireless charging devices. To make the optimization tractable, parallel computers must be used to cope with the large amounts of data and intensive computation inherent to these problems. In the last decade, parallel-in-time methods have made enormous progress: for parabolic problems, a near-optimal scaling with respect to the number of processors has been achieved (scalability). For wave propagation, there has been no such success.

To achieve our goal of developing innovative, space-time parallel methods for solving such optimization problems, we will consider three interrelated aspects. The first aspect is the direct simulation of wave-type systems, which must be done repeatedly over the course of the optimization. The second aspect is the optimization over bounded time horizons, which is at the heart of both data assimilation and wave localization problems. Here, our approach is to split the full optimality system into many subsystems in time and in space, and to use transmission conditions to ensure consistency with the global solution. We will then exploit the control structure and use the discrete Hilbert Uniqueness Method to derive optimal transmission conditions. Approximating these conditions by local, easy-to-implement conditions will then lead to highly efficient methods. The third aspect concerns the assimilation of infinite streams of data, where one cannot benefit from adjoint techniques. We will tackle this problem by combining parallel simulation with observer approaches, so that the time integration benefits from the space-time parallel methods mentioned above. Our methods will be used to tackle two concrete problems, namely wave localization in complex geometries and data assimilation in geophysical and environmental systems.

A-HKU704/19
Understanding FGF signaling to treat spinal defects (FANTASIA)

Hong Kong Principal Investigator: Prof Chan Danny (The University of Hong Kong)
French Principal Investigator: Dr Legeai-Mallet Laurence (Institut Imagine)

Spinal defects associated with short statures are genetic skeletal disorders that pose major socio economic burdens. Defects in FGFR3 signalling are common causes of short statures. Impaired growth of long bones due to excessive activation of FGFR3 signalling are well studied, but not for spinal defects such as lordosis, kyphosis, and stenosis. Recently, we have identified defects in the structure of the intervertebral discs and vertebral bodies that relate to abnormal chondrocyte proliferation and differentiation. These data are consistent with our novel findings that chondrocytes from the endplate cartilage contributes to the homeostasis of the intervertebral disc. Deciphering the molecular mechanisms of FGF signaling of skeletal development, growth, and aging is critical for the design of effective therapies for children and adult patients with short stature. The Paris and Hong Kong team has the combined synergistic expertise and resources in realizing the goal of FANTASIA.