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April 2023
Oleg Lisovyi: Semiclassical approach to form factors in the sinh-Gordon model
I will discuss a semiclassical approach to form factors in the sinh-Gordon field theory in the background of a radial classical solution that describes a heavy exponential operator placed at the origin. I will introduce and study new special functions which generalize the Bessel functions and have a nice interpretation in the Tracy–Widom theory of the Fredholm determinant solutions of the classical sinh-Gordon model. Unusual venue: F1 room, 1st floor
Find out more »Shane Kelly: Coherence and Scrambling in Quantum Circuits Coupled to a Monitored Environment
I will present our recent work on information transitions induced by coupling to an environmental. The first transition I will discuss occurs in a monitored random circuit where previously it was shown that a competition between unitaries and measurements can generate an entanglement transition. Instead here, we will show that an entanglement transition can instead be tuned by a competition between coherence generating and coherence destroying circuit elements. The second transition I will present occurs in a circuit that exchanges…
Find out more »May 2023
Kevin Kavanagh: Topological fingerprints in Liouvillian gaps
In quantum physics, topological properties usually emerge as a feature of equilibrium quantum states. We show that topological fingerprints can also manifest in the relaxation rates of open quantum systems. To demonstrate this we consider one of the simplest models that has two distinct topological phases in its ground state: the Kitaev model for the p-wave superconductor. After introducing dissipation to this model we estimate the Liouvillian gap in both strong and weak dissipative regimes. Our results show that a…
Find out more »Wilke van der Schee: A dynamical inflaton coupled to strongly interacting matter
In talk I will show how to self-consistently couple the Einstein-inflaton equations to a strongly coupled quantum field theory (QFT) as described by holography. We show that this can lead to an inflating universe, a reheating phase and finally a universe dominated by the QFT in thermal equilibrium. Special attention will be given to technical details that could be of relevance for modelling of more general holographic set-ups that for instance include charge.
Find out more »Scientific symposium in memory of Marko Medenjak (1990-2022)
On 12th and 13th 2023 will be held the symposium on Nonequilibrium many-body dynamics in memory of our colleague and friend Marko Medenjak who passed away last year. All talks will be given in the F1 room on the ground floor of the Faculty of Physics building, Jadranska 19. The symposium is open to all interested. Please find the program here.
Find out more »Marcello Porta: Edge transport in interacting quantum Hall systems
The bulk-edge correspondence is a remarkable duality in condensed matter physics, relating the value of bulk topological invariants to the emergence of gapless edge modes. In the case of the integer quantum Hall effect, the value of the Hall conductivity is equal to the sum of signed edge modes, taking into account their chirality. For noninteracting systems, this fact is by now understood in full mathematical rigor. For interacting models, in the last years there has been progress in the…
Find out more »July 2023
Nitin Gupta: Quantum Chaos and Quantum Phase Transitions
Quantum Complexity has emerged in the past few years as a candidate for quantum chaos diagnostic. This talk is based on a work that appeared last year, in which we show that a notion of quantum complexity (spread complexity / Krylov state complexity) is sensitive to Topological Phase Transitions - at least for the prototypical Kitaev chain. I'll give a brief overview of what we mean when we say "quantum” chaos, make connections with classical chaos and proceed to discuss…
Find out more »October 2023
Igor Poboiko: Theory of free fermions under random projective measurements
We develop a theory of measurement-induced phase transitions (MIPT) for d-dimensional lattice free fermions subject to random projective measurements of local site occupation numbers. Our analytical approach is based on the Keldysh path-integral formalism and replica trick. In the limit of rare measurements, \gamma << J (where \gamma is measurement rate per site and J is hopping constant), we derive a non-linear sigma model (NLSM) as an effective field theory of the problem. Its replica-symmetric sector is a U(2)/U(1) x…
Find out more »Lucas Sá : Symmetry Classification of Lindbladians
We discuss a unified and systematic symmetry classification of general (interacting) open quantum systems coupled to a Markovian environment, described by a Lindbladian superoperator. Our classification is based on the behavior of the matrix representation of the Lindbladian under antiunitary symmetries and unitary involutions. We find that Hermiticity preservation reduces the number of symmetry classes, while trace preservation and complete positivity do not, and that the set of admissible classes depends on the presence of additional unitary symmetries: in their…
Find out more »Vladimir Kravtsov: A renormalization group analysis of the Anderson localization problem in large and infinite dimensions
A celebrated one-parameter scaling of "Gang of four" was a guiding paradigm in the field of Anderson localization for decades. It was shown to work very well in three dimensions and was analytically proven in 2+\epsilon dimension using the renormalization group (RG) analysis of the non-linear supersymmetric sigma-model. However, its applicability to the Anderson localization problem on lattices of high dimensionality $d$ and for hierarchical graphs like Cayley tree and Random Regular Graph (RRG) has recently been put in question.…
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