Ученый Совет ИТФ им. Л.Д.Ландау, пятница 20 сентября 2019 г., ИТФ, 11:30|
Борис Лукьянчук (МГУ & Nanyang Technological University, Singapore)
High order Fano-resonances and extreme effects in field localization
The weakly dissipating dielectric spheres (glass, quartz, etc.) permit to realize high order Fano resonances for internal Mie modes. These resonances for specific values of the size parameter yield field-intensity enhancement factors on the order of 104–107, which can be directly obtained from analytical calculations. These “super-resonances” provides magnetic nanojets with giant magnetic fields, which is attractive for many applications.
Московский физико-технический институт
Лабораторный корпус МФТИ, к.122
контактный адрес: email@example.com (заведующий лабораторией М.В.Фейгельман, зам. зав. И.В.Загороднев)Направления исследований
colloquium, пятница 6 сентября 2019 г., , 11:30|
Sergej Flach (Institute for Basic Science, Republic of Korea)
Dynamical Glass - en route from KAM and FPUT to MBL
Classical many body interacting systems are typically chaotic (nonzero Lyapunov exponents) and their microcanonical dynamics ensures that time averages and phase space averages are identical (ergodic hypothesis). In proximity to an integrable limit the long- or short-range properties of the network of nonintegrable action space perturbations define the finite time relaxation properties of the system towards Gibbs equilibrium. I will touch upon few analytical results including the KAM theorem, and review a number of computational studies which originate from the pioneering work of Enrico Fermi, John Pasta, Stanislaw Ulam and Mary Tsingou. I will then focus on short range networks which lead to a dynamical glass (DG), using a classical Josephson junction chain in the limit of large energy densities or small Josephson energies. Close to these limits the Josephson coupling between the superconducting grains induces a short-range nonintegrable network in the corresponding action space. I will introduce a set of quantitative measures which lead to the Lyapunov time TΛ, the ergodization time TE, and to a diffusion constant D. In the DG the system fragments into large patches of nonresonant ’integrable’ grains of size l separated by triplets of resonant chaotic patches, all surviving over large times. TE sets the time scale for chaotic dynamics in the triplets. Contrary, TE ≈ l2/D is the much larger time scale of slow diffusion of chaotic triplets. The DG is a generic feature of weakly non-integrable systems with a short range coupling network in action space, and expected to be related to nonergodic quantum metallic states of quantum many-body systems in proximity to a many-body localization phase.