Star formation is a fundamental process in astrophysics, which has been studied for decades. As of now, most of our knowledge is concentrated on the formation of stars of a few solar masses. If galaxies' total stellar mass is dominated by low-mass stars, their energy budget is exclusively controlled by the enormous luminosity and powerful feedback of massive stars (M > 8 Msun). Despite their importance, the mechanisms leading to the formation of high-mass stars remain a mystery in many aspects. From the theoretical point of view, low-mass star formation models are not directly transposable as they do not provide accretion rates in line with what is necessary for high-mass star formation. From the observational point of view, until the recent rise of large interferometers, little was known about the formation of massive stars due to their scarcity, and remoteness. Through my work with interferometers, I have proved that very dynamical processes (colliding flows) are at play in high-mass star-forming regions (HMSFR). On the other hand, recent studies have shown that magnetic fields are a key factor in the regulation of star-formation. I am convinced that the dynamical features observed in HMSFR coupled with the action of the magnetic fields could explain for the formation of high-mass stars. For this two-year project, I plan on studying the coupling of gas dynamics with magnetic fields. For this purpose, I present an innovative project that will study this coupling simultaneously from observational and numerical inquiries. I will use today's best instrument in radio-astronomy, ALMA, to trace both the kinematics of gas and the magnetic field morphology. This observational part relies on data that I have already acquired. For the numerical part, I will participate in the development of dedicated magneto-hydro-dynamical simulations together with P. Hennebelle to understand the physical processes that underlie the observational features.
Photoenzymes are rare biocatalysts that use the energy contained in photons to perform chemical reactions. To date, only one natural photocatalyst is known to have biotechnological applications; the Fatty Acid Photodecarboxylase (FAP), allowing the production of hydrocarbons from fatty acids. FAP belongs to a superfamily of enzymes called Glucose Methanol oxidoreductases (GMCox). Still, the FAP group is the only one known to perform photochemistry despite the high degree of structural similarity and presence of a photosensitive cofactor, Flavine Adenine Dinucleotide (FAD), in all GMCox. We reason that the GMCox family could have a latent photochemical function, and we would like to exploit it. Therefore, the objective of this project is to EXplore Photoinduced Enzyme pRomIscuity in the Glucose-Methanol-Choline oxidoreductase family to dEvelop New phoTocAtaLysts (EXPERIMENTAL). To this end, we will first test the photoinduced substrate promiscuity with different GMCox using an “accelerated serendipity” approach. In a second step, we will optimize the newly discovered photoenzymatic activity by directed evolution. Finally, the enzymatic mechanism will be characterized using different biophysics approaches, ranging from time-resolved spectroscopy to serial femtosecond crystallography. This project is inherently interdisciplinary, combining chemistry, biochemistry and biophysics to develop new photocatalysts for biotechnological purposes. For fundamental research these new photoenzymes will be an opportunity allowing the study of ultrafast processes that occur during catalysis and can only be observed with light-dependent enzymes such as electron and/or proton transfer, bond breaking ect. In fine, the goals of EXPERIMENTAL are to provide a better appreciation of the capabilities of enzymes and meet the demand for new and sustainable methods in organic synthesis by providing with the GMCox family a toolbox for the design of new light-driven reactions.
I propose to solve the Quantum Field Theory (QFT) describing the transition between plateaus of quantized Hall conductance in the Integer Quantum Hall Effect (IQHE). The existence of the plateaus and their topological origin are certainly well understood. In sharp contrast, the transition, which mixes the effects of disorder, magnetic field and possibly interactions, remains very mysterious. Numerical studies of lattice models are plagued by disorder. The QFT description involves physics at very strong coupling, and requires a non-perturbative solution before quantitative predictions can be made. Finding such a solution is very difficult because the QFT for the plateau transition is ‘non-unitary’ - it involves a non-Hermitian ‘Hamiltonian’. Non-unitary QFT is a challenging, almost unexplored topic, that must be first developed before the plateau transition can be addressed. I propose to carry out this task with a cross-disciplinary strategy that uses ideas and tools from conformal field theory, statistical mechanics, and mathematics. Key to this strategy is a new and powerful way of analyzing lattice regularizations of the QFTs by focussing on their algebraic properties directly on the lattice, with a mix of advanced representation theory and numerical techniques. The results - in particular, concerning conformal invariance and renormalization group flows in the non-unitary case - will then be used to solve the QFT models for the plateau transition in the IQHE and in other universality classes of 2D Anderson insulators. This will be a landmark step in our understanding of the localization/delocalization transition in two dimensions, and allow a long delayed comparison of theory with experiment. The results will, more generally, impact many other areas of physics where non-unitary QFT plays a central role - from disordered systems of statistical mechanics to the string theory side of the AdS/CFT duality, to the effective description of open quantum systems.