Bernardo Spagnolo
Bernardo Spagnolo is Associate Professor of Theoretical Physics at the Palermo University. National Scientific Habilitation for Full Professor of: a) Theoretical Physics of Condensed Matter (2013); b) Applied Physics (2013); c) Theoretical Physics of Fundamental Interactions (2014).
Visiting Scientist and Visiting Professor at “Radiophysics Department”, Lobachevsky State University of Nishny Novgorod (Russia) (2001–2017); Humboldt-University in Berlin (2004); Lomonosov State University of Moscow (Russia), (2004 – 2006); Nicolaus Copernicus University, Torun (Poland), (2006); Max-Planck Institut fur Physik Komplexer Systeme, Dresden, Germany, (2006); Jagellonian University, Max Kak, (2011–2012).
His research field is: Nonequilibrium Statistical mechanics and Physics of Complex Systems in Interdisciplinary applications.
Awards and Recognitions: a) Outstanding Referees of the Physical Review and Physical Review Letters, American Physical Society, 2014; b) Member of the Scientific and Methodological Council of PhD School “Vibrational and wave processes in natural and artificial environments” at the Lobachevsky State University of Nizhni Novgorod, National Research University of Russia, since 2014.
He is Designed Editor for the Interdisciplinary Physics Section of Cogent Physics, Taylor & Francis Group (since 2014); and Editor of Chaos, Solitons & Fractals, Elsevier Ed. (since 2015).
International PhDs: Chairman of the International PhD in Applied Physics (2010-2016); Vice-Coordinator of the Int. PhD in Physical Sciences, since 2013.
Chairman of International Congresses.
Driven quantum metastable states: stabilization by dissipation and resonant activation
Normally, quantum fluctuations enhance the escape from metastable states in the presence of dissipation. We show first that dissipation can enhance the stability of a quantum metastable system, consisting of a particle moving in a strongly asymmetric double well potential, interacting with a thermal bath. We find that the escape time from the metastable region has a nonmonotonic behavior versus the system-bath coupling and the temperature, producing a stabilizing effect. We also find that the behavior of the escape time versus the temperature is nonmonotonic, and in particular is characterized by the presence of a minimum. Therefore, as the temperature increases, an enhancement of the escape time is observed, increasing the stability of the metastable state. These results shed new light on the role of the environmental fluctuations in stabilizing quantum metastable systems.
We investigate then, how the combined effects of strong Ohmic dissipation and monochromatic driving affect the stability of a quantum system with a metastable state. We find that, by increasing the coupling with the environment, the escape time makes a transition from a regime in which it is substantially controlled by the driving, displaying resonant peaks and dips, to a regime of frequency-independent escape time with a peak followed by a steep fall off. The quantum noise enhanced stability phenomenon is observed in the system investigated.
Thirdly, we analyze the resonantly activated escape from a quantum metastable state by tunneling in the spin-boson model at strong Ohmic dissipation in the presence of fluctuating and periodical driving fields. Resonant activation, the presence of a minimum in the mean escape time, occurs when the time scale of the modulations is the same as the characteristic time scale of the system’s dynamics, essentially determined by dissipation-induced renormalization of the bare tunneling amplitude. The simple quantum system considered displays as well the general features that at slow modulations the mean escape time is dominated by the slowest configuration assumed by he system, while at fast modulations the escape dynamics is determined by the average configuration.
