Semi-classical quantisation of magnetic solitons in the anisotropic Heisenberg quantum chain

Using the algebro-geometric approach, we study the structure of semi-classical eigenstates in a weakly-anisotropic quantum Heisenberg spin chain. We outline how classical nonlinear spin waves governed by the anisotropic Landau-Lifshitz equation arise as coherent macroscopic low-energy fluctuations of the ferromagnetic ground state. Special emphasis is devoted to the simplest types of solutions, describing precessional motion and elliptic magnetisation waves. The internal magnon structure of classical spin waves is resolved by performing the semi-classical quantisation using the Riemann-Hilbert problem approach. We present an expression for the overlap of two semi-classical eigenstates and discuss how correlation functions at the semi-classical level arise from classical phase-space averaging.Comment: 61 pages, 14 figure

Rehabilitation Works Of The Existing Asphalt Pavement And Connecting The Existing Asphalt Pavement With The Newly Constructed Pavement, Motorway E-75, Section Tabanovce - Kumanovo From Km 0+764.70 To Km 8+388.43, Part Of The Corridor X

The Corridor X is part of the pan-European network of corridors. The starting point of the corridor is in Salzburg, Austria and the end point is in Thessaloniki, Greece. The corridor passes through Austria, Slovenia, Croatia, Serbia, Macedonia and Greece. The Construction of the Corridor is supported by the international financing institutions like the European Bank for Reconstruction and Development (EBRD) and the International Bank for Reconstruction and Development (IBRD). The paper refers to one of the sections in R. Macedonia that is under the construction, section between Tabanovce and Kumanovo in length of 7.62 km.Part of the pavement works consisted of rehabilitation of the existing pavement with applying polymer grids, specially designed for such purpose. In the paper the entire procedure of the pavement design will be presented, with particular attention on the quality requirements of the materials that should be for the road construction. Numerical analysis of the pavement was accomplished using the software package PLAXIS. The results of these analyses are presented in the paper, namely: stress fields and zones where the plasticity limit of the materials was reached. The cross section was treated with and without polymer grids. The number of the polymer grids in the cross section was also varied, as well as its location. The presented procedure of the pavement design coul

Spin diffusion in perturbed isotropic Heisenberg spin chain

The isotropic Heisenberg chain represents a particular case of an integrable many-body system exhibiting superdiffusive spin transport at finite temperatures. Here, we show that this model has distinct properties also at finite magnetization $m\ne0$, even upon introducing the SU(2) invariant perturbations. Specifically, we observe nonmonotonic dependence of the diffusion constant ${\cal D}_0(\Delta)$ on the spin anisotropy $\Delta$, with a pronounced maximum at $\Delta =1$. The latter dependence remains true also in the zero magnetization sector, with superdiffusion at $\Delta=1$ that is remarkably stable against isotropic perturbation (at least in finite-size systems), consistent with recent experiments with cold atoms.Comment: 5+5 pages, 4+5 figure

Thermodyamic bounds on Drude weights in terms of almost-conserved quantities

We consider one-dimensional translationally invariant quantum spin (or fermionic) lattices and prove a Mazur-type inequality bounding the time-averaged thermodynamic limit of a finite-temperature expectation of a spatio-temporal autocorrelation function of a local observable in terms of quasi-local conservation laws with open boundary conditions. Namely, the commutator between the Hamiltonian and the conservation law of a finite chain may result in boundary terms only. No reference to techniques used in Suzuki's proof of Mazur bound is made (which strictly applies only to finite-size systems with exact conservation laws), but Lieb-Robinson bounds and exponential clustering theorems of quasi-local C^* quantum spin algebras are invoked instead. Our result has an important application in the transport theory of quantum spin chains, in particular it provides rigorous non-trivial examples of positive finite-temperature spin Drude weight in the anisotropic Heisenberg XXZ spin 1/2 chain [Phys. Rev. Lett. 106, 217206 (2011)].Comment: version as accepted by Communications in Mathematical Physics (22 pages with 2 pdf-figures