[Landau ITP Seminars] Correction: семинары 6 сентября

[Serge Krashakov]

В разосланном несколько минут назад письме была допущена ошибка:

В пятницу 6 октября будет заслушано 2 доклада одного и того же докладчика:

11:30 Коллоквиум
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

16:00 Семинар
Sergej Flach
*The wonderful world of flatbands*

Certain lattice wave systems in translationally invariant settings have 
one or more spectral bands that are strictly flat or independent of 
momentum in the tight binding approximation, arising from either 
internal symmetries or fine-tuned coupling. These flat bands display 
remarkable strongly interacting phases of matter. Originally considered 
as a theoretical convenience useful for obtaining exact analytical 
solutions of ferromagnetism, flat bands have now been observed in a 
variety of settings, ranging from electronic systems to ultracold atomic 
gases and photonic devices. I will review the design and implementation 
of flat bands and chart future directions of this exciting field. In 
particular I will focus on the field of photonic lattices. Flatband 
photonic lattices consist of arrays of coupled waveguides or resonators 
where the peculiar lattice geometry results in at least one completely 
flat or dispersionless band in its photonic band structure. Although 
bearing a strong resemblance to structural slow light, this independent 
research direction is instead inspired by analogies with “frustrated” 
condensed matter systems. In this talk, I will critically analyze the 
research carried out to date, discuss how this exotic physics may lead 
to novel photonic device applications, and chart promising future 
directions in theory and experiment.


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.itp.ac.ru/pipermail/seminars/attachments/20190905/8505b908/attachment.html>