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Visiting Scientists

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Visiting Scientists

The actions to pursue the objectives of the DdE are also supported by a program of invitations of visiting scientists from foreign research institutions. The visiting scientists contribute to highly qualified teaching with cycles of seminars and lessons for PhD students and Master's students.

Below we report a list of visiting scientists whose visit has been scheduled, and of those who have already visited the Department, with information relative to the activity carried out.

Upcoming visits

Elena Pierpaoli

(University of Southern California, Pasadena)
23 June - 13 July 2024
Research line: HPC-BD-ML

Anna Bergamaschi

(PSI - Zurigo, CH)
February 2025
Research Line: LEA

Peter Skands

(Monash Univ., Melbourne)
May-June 2025
Research Line: LEA

Francisco Villaescusa-Navarro

(Simons Foundation, Center for Computational Astrophysics, New York)
between mid-June and mid-July 2025
Research Line: HPC-BD-ML

Past visits

Prof. Robert Alicki

International Center for Theory of Quantum Technologies (ICTQT), University of Gdansk (Poland)

March 4, 2024 - March 8, 2024

Research Line: STQ

Colloquium:
"Cosmology without epicycles"

The four puzzles of cosmology, namely the origin of inflation and its termination, baryogenesis, acceleration of expansion and dark matter composition, are addressed within a new model which does not involve "epicycles" like inflaton fields with fine-tuned potentials or dark energy concept. The main assumption, motivated by the analysis of the reduced dynamics of open quantum systems embedded in the de Sitter space, is that the corresponding vacuum can be treated as a real, physical heat bath at the Gibbons-Hawking temperature proportional to the Hubble constant. This leads to the modified Friedmann equations for the Friedmann-Lemaitre-Robertson-Walker universe which predict the new mechanism of inflation and its graceful exit, mathematically similar to the model of superfluorescence in quantum optics, and additionally, a viable baryogenesis mechanism via gravitational anomaly. The same equations applied to the late Universe show inevitability of acceleration of expansion which in turn puts very specific limits on the particle spectrum beyond the Standard Model relevant for dark matter particles.

Prof. Dariusz Chruscinski

Institute of Physics, Nicolaus Copernicus University, Torun (Poland)

February 19, 2024 - February 23, 2024

Research Line: STQ

Colloquium:
"Universal properties of relaxation rates for the irreversible dynamics of open quantum systems"

Open quantum systems, namely quantum systems in weak interaction with their environment, evolve irreversibly as manifested by typical relaxation rates, a general property of which is reviewed. It turns out that for a fairly large class of irreversible quantum dynamics, relaxation rates satisfy an intricate constraint which provides a generalization of the well known relation between transversal and longitudinal rates for 2-level systems. It is conjectured that this constraint is universal, i.e., it is valid for all quantum dynamical semigroups. The conjecture is strongly supported by numerical analysis. Moreover, it is shown that the conjectured constraint is tight. Since relaxation rates (or equivalently relaxation times) are often measured in the laboratory, this universality may be considered as a physical manifestation of complete positivity, a structural request necessary for physical consistency. The conjecture has also interesting implications: it provides a universal constraint for the spectra of quantum channels and gives rise to necessary conditions for Markovian channels.

Prof. Lajos Diósi

Wigner Research Center for Physics & Eötvös Loránd University (Hungary)

October 16, 2023 - October 21, 2023

Research Line: STQ

Seminar:
"Will quantum theory be different in the macro-world?"

Quantum theory was invented for the microscopic world, and proved accurate there. Is it valid in the macroscopic world as well? Is quantum theory universal from particle physics to cosmology? We might like to think so. Except that the experimental evidences are lacking, the relevant theories limp along, and there are crippling conceptual problems. It is therefore not impossible that quantum theory will be different when it reaches the macro-world. But how different will it be? In quantum theory, the micro-world only affects the macro-world when a measurement is made on the micro-world. Wouldn't there exist certain spontaneous measurements, acting universally everywhere and everytime, negligibly weak in the micro-world and amplified in the macro-world? What does such a theory of spontaneous measurement (i.e., spontaneous wavefunction collapse) look like and what is it good for?

Prof. Alberto Imparato

Department of Physics and Astronomy, Aarhus University (Denmark)

August 27, 2023 - September 02, 2023

Research Line: FSC

Seminar:
"Modelli di motori termici autonomi in prossimità di un punto critico: dinamica e termodinamica stocastica"

In a system at equilibrium near a critical point, the response to a change in an external field is significantly high. Starting from this consideration, I will discuss the properties of systems of microscopic motors in the vicinity of a second-order phase transition. In particular I will consider a 2D lattice rotor model in contact with baths at different temperatures and an out-of-equilibrium Frenkel--Kontorowa model. Both models behave like heat engines, converting the heat currents between the baths into rotational or linear motion. In my seminar I will show that the optimal operating regime is found when the temperature gradient is applied on a system near a phase transition.