A system of bosons studied within the mean field framework has two fascinating phenomena: a liquid-gas first order phase transition and Bose-Einstein condensation. Interplay between these two phenomena is being investigated. Depending on the mean-field potential parameters one can observe two types of critical points (CP), called ”Boltzmann” and ”Bose”, that belong to different universality...
The Ising model is an archetype describing collective ordering processes. As such, it is widely known in physics and far beyond. Less known is the fact that the thesis defended by Ernst Ising 100 years ago under supervision of Wilhelm Lenz [1] contained not only the solution of what we call now the ‘classical 1D Ising model’ but also other problems. Some of these problems are the subject of...
We analyze multi-qubit states that can be represented using directed graphs G(V,E). We focus on the geometric properties of these states, namely on curvature and torsion [1]. It has been found that the curvature of quantum states is determined by the sum of the weighted degrees of nodes in graphs where the weights in G(V,E) are raised to the second and fourth powers [2]. Additionally,...
In this talk some less known facts of the discovery of the Wave of Translation will be discussed. A brief review of the advancement of the theory of Davydov's solitons will be given. New results on the study of the dynamics of the Davydov’s soliton [1] in an external oscillating in time magnetic field [2,3] will be reported.
It is shown that in the magnetic field, perpendicular to the...
The nonlinear Klein–Gordon (nKG) model,
$
\partial_{tt}\phi-c^{2}\partial_{xx}\phi+f(\phi)=0,
$
is a universal model for describing the propagation of nonlinear waves in various physical media. For example, its stationary version describes the macroscopic wave function of the condensed phase (i.e., the order parameter) in the Landau theory of phase transitions. Noteworthy is also an...
The entanglement of diamond spin systems in thermodynamic equilibrium has
been studied in various papers (for, example, [1, 2, 3, 4]). We focus on the evolution of entanglement in a diamond spin-1/2 cluster. This cluster consists of two central spins described by the anisotropic Heisenberg model, which interact with two side spins via an Ising interaction. The influence of the interaction...
