Propositions for M1S2 tutored project

M1 students have the possibility to carry out their optional tutored project with the GeQS. The project’s subject should respect the guidelines imposed by the Faculty, but within these limits, we allow a great freedom in the subject’s choice and we propose to build the project in continued collaboration with the student.

The subjects specified below are examples rather than an exhaustive list. You can come up with your own subject, based on personal ideas or in connection with any of our research topics. In accordance with the GeQS’ objectives, the propositions below are research subjects that necessitate a thorough preliminary bibliographical search.

In the ideal case, the tutored student would begin their project by this bibliographical search, whose outcome is their oral examination at the end of the semester, and then would carry out the associated research in close collaboration with GeQS members, resulting in the publication of a paper, either in the Strasbourg Students Physical Letters if the material is too thin or in an exterior journal if sufficiently interesting new results have been obtained.

Please contact Loris Delafosse for any question, or if you are interested in following a tutored project with the GeQS.

All propositions are classified into one or several of the three following classes: (1) biophysics and soft condensed matter; (2) quantum physics, quantum condensed matter and solid state physics; (3) subatomic physics, astrophysics and cosmology.

Your internship and your tutored project cannot belong to the same class. Many of the subjects can be classified into two different classes, changing the colouration of the project.

Subject examples listed below:

Time reversal symmetry

Possible colourations: quantum physics (2) or high-energy physics (3)

Most microscopic physical processes are symmetric under time reversal. More often than not, irreversibility is an emergent property of large systems, justified by statistical considerations. However, considering “T-symmetry” as a fundamental symmetry of nature raises questions: for instance, how is it compatible with causality? Maxwell’s theory of electromagnetism is not symmetric under time reversal since it only considers electromagnetic waves propagating forward in time (retarded solutions of the d’Alembert equation). The Wheeler-Feynman absorber symmetrizes the theory by also taking into account the waves propagating backward in time (advanced solutions of the d’Alembert equation). Remarkably, the advanced waves can be “recast” in terms of retarded waves, making the absorber theory equivalent to Maxwell’s theory, and so T-symmetry can be reconciled with causality.

What happens if we try to describe other fields (electrons, for instance) with this kind of symmetric formalism? Can the backward waves be interpreted as antiparticles? Can we recast these antiparticles in terms of particles? The absorber theory also strongly inspired the transactional interpretation of quantum mechanics where retarded and advanced wavefunctions are considered. Again, can these advanced wavefunctions be interpreted as antiparticles?

T-symmetry is however not a fundamental symmetry of the Standard Model, since it is violated by weak interaction. Why? How? And since it is not possible to effectively reverse time in a laboratory, how can we measure T-symmetry violation?

Applications of the Bohr-Sommerfeld semi-classical theory

Possible colourations: quantum physics (2), high-energy physics (3) or cosmology (3)

Semi-classical methods yield astonishingly good results for a number of useful systems and can deepen our understanding of Quantum Mechanics. Among the most notorious semi-classical quantization schemes, we can cite the Bohr-Sommerfeld rule which, despite its mathematical simplicity, correctly describes the energy gaps of the infinite well, the harmonic oscillator, the hydrogen atom, etc. Is it possible to apply the Bohr-Sommerfeld theory to more complicated systems, are what are its limits? Can we describe electron correlations in many-body systems? light-matter couplings? quantum chromodynamics? quantum gravity?

Primordial black holes and baryogenesis

Possible colourations: high-energy physics (3) or cosmology (3)

Baryogenesis, the unknown process that provoked the matter/antimatter asymetry in the early universe, remains to this day one of the most elusive mysteries of cosmology and high-energy physics, in spite of the identification of the three famous Sakharov conditions that it must satisfy. A number of models predict the existence of small black holes in the same early universe. Such primordial black holes should be short-lived because they lose energy by Hawking radiation, that is quantum fluctuations around their event horizon. We propose to investigate the possibility that Hawking radiation from primordial black holes may have produced more particles than antiparticles, thus leading to baryogenesis.

The ADM formalism of General relativity and its connection to twistor theory

Colouration: cosmology (3)

The ADM formalism is a formulation of General Relativity (GR) in which spacetime is sliced into space-like hypersurfaces, reintroducing a clear separation between “space” (the hypersurfaces) and “time” (a parameter describing a sequence of space-like hypersurfaces). There seems to be a deep connection between this point of view and twistor theory, a (now largely abandoned) program proposed by Roger Penrose a few decades ago that describes spacetime not as a set of events, but as being generated by the light rays. Light rays are themselves described as twistors, objects composed of two spinors, thus formulating GR in a language shared by Quantum Mechanics. For a while, physicists hoped twistors could be the key to Quantum Gravity, but the program never came to fruition. Twistor theory is nevertheless still used nowadays, in string theory for example, as it facilitates some mathematical derivations.