Approximation methods of many-body theory
(by Nicolò Defenu)
Quantum many-body systems present some of the most challenging
problems in theoretical physics, as exact solutions are rarely attainable beyond a few special cases. To tackle this complexity, a wide range of approximation methods have been developed, each tailored to specific regimes and physical phenomena. In this proseminar cycle, we will explore the foundational principles behind these approximations, including mean-field approaches, perturbative expansions, variational techniques, Green’s function methods, and renormalization group strategies. We will examine their domains of validity, strengths and limitations, and how they connect to modern computational frameworks such as Dynamical Mean-Field Theory and Quantum Monte Carlo. The vast literature in this field will be organized thematically, starting from seminal articles and progressing to more recent research papers. Each presentation will be followed by interactive discussion sessions aimed at fostering a deeper understanding of the conceptual and practical aspects of these methods.
(6 Bachelor students, 12 Master students)
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Dark Matter
(by Achilleas Lazopoulos)
Dark Matter is estimated to make up approximately 25% of the energy density of the Universe and appears to be the sole strong evidence for physics beyond the Standard Model. Still, its nature remains a total mystery. In this proseminar cycle we will explore the existing evidence for Dark Matter, its typical distribution patterns, the viable theoretical ideas describing the way it has been produced, the proposed experimental approaches for its detection in the future, and the main paradigms of Dark Matter theory models, as well as alternatives to the Dark Matter hypothesis. The vast literature of this field will be organized thematically based on review articles and extending to state-of-the-art research papers. All presentations will be followed by lively discussion sessions as a means of shaping a deeper understanding of the topic.
(3 Bachelor students, 21 Master students)
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Cavity quantum electrodynamics
(by Chitra Ramasubramanian)
Cavity quantum electrodynamics (cavity QED) explores the fundamental interaction between quantized light fields and matter confined within high-finesse optical or microwave resonators. By enhancing and controlling light–matter coupling, cavity QED enables the exploration of a a wide variety of phenomena in many-body physics. When ensembles of atoms or molecules collectively couple to a cavity mode, they exhibit emergent behavior such as superradiant phase transitions, self-organized , supersolid phases, landau level polaritons etc. Multimode cavities further enable frustrated interactions and the realization of quantum-simulation models beyond those available in conventional materials. This seminar course will span the theoretical foundations of cavity QED, key experimental platforms and emergent physics in the regimes of strong and ultrastrong coupling. Students will engage with classic papers and current research to build an understanding of how engineered photonic environments shape quantum dynamics.
(6 Bachelor students,12 Master students)