We present a calculation of the recombination rate of the excited holon-doublon pairs based on the two-dimensional model relevant for undoped cuprates, which shows that fast processes, observed in pump-probe experiments on Mott-Hubbard insulators in the picosecond range, can be explained even quantitatively with the multimagnon emission. The precondition is the existence of the Mott-Hubbard bound exciton of the s-type. We find that its decay is exponentially dependent on the Mott-Hubbard gap and on the magnon energy, with a small prefactor, which can be traced back to strong correlations and consequently large exciton-magnon coupling.

COBISS.SI-ID: 2579044

Bad metals are materials with resistivity corresponding to the mean-free-path of charge carriers comparable to the nearest-neighbour distance in the crystal lattice. Such behaviour is found in some correlated materials, for instance in doped Mott insulators. Using the dynamical mean field theory we studied the doped Hubbard model and established the temperature dependence of the spectral properties. We discovered the existence of resilient quasiparticles that remain well defined above the Fermi temperature and dominate the transport in the intermediate regime up to the Mott-Ioffe-Regel regime.

COBISS.SI-ID: 26841383

For fundamental integrable quantum chains with deformed symmetries we outline a general procedure for defining a continuous family of quasilocal operators whose time derivative is supported near the two boundary sites only. The program is implemented for a spin 1=2 XXZ chain, resulting in improved rigorous estimates for the high temperature spin Drude weight. The key element of the approach which ensures quasilocality of the new conserved quantities is a derivative of the transfer matrix with respect to a complex representation parameter (e.g. complex spin parameter in the case of SU(2) symmetric chain) around the trivial point.

COBISS.SI-ID: 2572900

In this paper, we have done extensive analysis of empirical data collected from two types of communication systems---Blogs and Internet-Relayed-Chat channels in the presence of Web robots (Bots). In addition, as part of EU project, we have developed corresponding theoretical models of interacting emotional agents on networks, where the dynamic rules and control parameters were inferred from these empirical systems. Using fractal analysis of time series as well as topology analysis of corresponding networks that emerge in the same self-organized processes comprising emotional interactions of users, agents and Bots, we have demonstrated that two prevailing co-evolutionary mechanisms exist, which are strongly related with different use of emotions.

COBISS.SI-ID: 27275303

We show that in a nonintegrable spin ladder system with the XX type of coupling along the legs and the XXZ type along the rungs there are invariant subspaces that support ballistic magnetization transport. In the complementary subspace the transport is found to be diffusive. This shows that (i) quantum chaotic systems can possess ballistic subspaces, and (ii) diffusive and ballistic transport modes can coexist in a rather simple nonintegrable model.

COBISS.SI-ID: 2538340