Seminář Ústavu teoretické fyziky

Seminář se koná v úterky v 10:40 v posluchárně ÚTF na 10. patře katedrové budovy v Tróji, V Holešovičkách 2, Praha 8

Příští semináře:

13. října 2026: The Catalan Problem; doc. RNDr. Martin Klazar, Dr.; Department of Applied Mathematics, MFF Charles University; (seminář v angličtině); In 1844, E. Catalan conjectured that the only solution of the equation a^b - c^d = 1 in natural numbers greater than 1 is 3^2 - 2^3 = 1. This was eventually proven by P. Mihailescu in 2004. I will review history of the Catalan problem and present proofs of some particular cases.
20. října 2026: Quantum Walks; doc. Ing. Martin Štefaňák, Ph.D.; Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague; (seminář v angličtině); Quantum walks represent a generalization of a random walk to coherent evolution of a quantum particle on a graph or a lattice. We provide an overview of the concept, focusing on the discrete-time quantum walk, and illustrate their applications in quantum simulations and quantum computation. In particular, we discuss the quantum walk search algorithm and its modification to quantum state transfer. Finally, we introduce a very successful experimental implementation of quantum walks based on photonic time-multiplexing and review some of the experiments.
27. října 2026: Messengers from Imaginary Time: Instantons, Topology and the Hidden Structure of Complex Time; Mgr. Tomáš Sýkora, Ph.D.; Institute of Particle and Nuclear Physics, MFF Charles University; (seminář v angličtině); Standard QFT perturbation theory expands around one saddle point of the path integral. Other saddle points include instantons, exact Euclidean solutions that dominate tunnelling between topologically distinct vacua. They can be viewed as messengers from imaginary time, t → −iτ, carrying news from the complex domain into real-world physics. Starting from a particle in a double well, I follow them into gauge theory, where they account for facts no Feynman diagram can give: the η′ mass, the near-vanishing strong CP angle, electroweak baryon-number violation. The mathematics along the way — homotopy, the index theorem, moduli spaces, Lefschetz thimbles, resurgence — is part of the message. A solvable family of potentials then shows the instanton continued back to real time: regular, periodic, its action climbing a staircase. Finally, can these messengers be seen? The obstacle is the instanton size: controlled where rare, common where uncontrolled. HERA found no signal, with a limit five times below the standard prediction; the LHC is trying; the Electron–Ion Collider can count the instanton's strangeness. Prospects remain open for detection in the next decade.

Minulé semináře:

6. října 2026: [ seminář se nekoná, setkání s bakalářskými studenty ]; doc. RNDr. Karel Houfek, Ph.D.; (seminář v češtině)
29. září 2026: [ seminář se nekoná, setkání s magisterskými studenty ]; doc. RNDr. Karel Houfek, Ph.D.; (seminář v češtině)

David Heyrovský <david.heyrovsky@matfyz.cuni.cz>; Jiří Horáček <jiri.horacek@matfyz.cuni.cz>

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