Vasúti konfliktuskezelés adiabatikus kvantumszámítással
Inhomogeneous quantum quenches in the sine-Gordon theory
In this talk I review our recent results  on inhomogeneous quantum quenches in the attractive regime of the sine--Gordon quantum field theory. The system is prepared in an inhomogeneous initial state in finite volume by coupling the topological charge density operator to a Gaussian external field. After switching off the external field, time evolution is governed by the homogeneous sine-Gordon Hamiltonian. Varying either the interaction strength of the sine-Gordon model or the amplitude of the external source field, an interesting transition is observed in the expectation value of the soliton density. This affects both the initial profile of the density and its time evolution and can be summarised as a steep transition between behaviours reminiscent of the Klein-Gordon, and the free massive Dirac fermion theory with initial external fields of high enough magnitude. The transition in the initial state is also displayed by the classical sine-Gordon theory and hence can be understood by semi-classical considerations in terms of the presence of small amplitude field configurations and the appearance of soliton excitations, which are naturally associated with bosonic and fermionic excitations on the quantum level, respectively. Features of the quantum dynamics are also consistent with this correspondence and comparing them to the classical evolution of the density profile reveals that quantum effects become markedly pronounced during the time evolution. These results suggest a crossover between the dominance of bosonic and fermionic degrees of freedom whose precise identification in terms of the fundamental particle excitations can be rather non-trivial. Nevertheless, their interplay is expected to influence the sine-Gordon dynamics in arbitrary inhomogeneous settings.
 D. X. Horváth, M. Kormos, S. Sotiriadis, G. Takács, arXiv:2109.06869
Dc-current stimulated superfluid density in strongly disordered 2D-superconductors
Non-Hermitian Linear Response Theory
COVID-19: a multiscale problem
Budapest Kvantumszámítás Meetup
Symmetry breaking and Chern insulators in twisted graphene structures
Twisted bilayer graphene (tBG) and variants like twisted monolayer-bilayer graphene (tMBG) were proposed to be a platform for strongly correlated physics akin to the cuprate family. However, I will show that many of the observed interacting phenomena can be explained in terms of breaking of spin/valley symmetry. This can lead to a quantum anomalous Hall effect in the absence of a field, as I will show for tMBG . In large magnetic fields the same spin- valley symmetry breaking leads to a series of Chern insulator states . Finally, I will briefly discuss the possibility of genuine strong correlated physics in Moiré structures.
Complex physical systems and the Nobel Prize in Physics 2021
Syukoro Manabe, Klaus Hasselmann and Giorgio Parisi received the Nobel Prize in Physics from the Swedish Academy of Sciences in 2021 for their “groundbreaking contributions to the understanding of complex physical systems”. In the first half of the presentation, we briefly present the key results of the winners. We then discuss Parisi's findings on disordered systems in more detail. In this context we describe the different forms of fluctuations due to disorder and their role in the collective behavior of many-body systems. We pay special attention to the replica symmetry breaking conditions in spin glasses, which represent a new form of organization of matter.
Mikulás Fizika 2021
- Időpont: 2021. december 6., 17 óra
- A Mikulás Fizika honlapjának címe: http://jedlik.phy.bme.hu/mikulas/
- Youtube link: https://youtu.be/quaZo8ecNKY
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