The problem of the analysis of low temperature magnetization is exposed in detail. The application of exact Bose representation of spin operators to the bulk ferromagnets is justified. By means of this representation the magnetization of ultrathin films was analysed. It turned out that thin films magnetization contains exponentially small terms characterized by Dyson's functions even in harmonical approximation. The main conclusions of this work

The low-temperature magnetization of a film was analyzed by the use of exact Bose representation of spin operators that does not suffer from the presence of unphysical states. The magnetization of thin films has exponentially small temperature correctness, so that Dyson’s proof about exponentially small correction coming from two bosons at ideal lattice point cannot be used in film analyses. The main conclusions of this work are that magnetic lattice

We have examined the excitation on coherent states of the pseudoharmonic oscillator which are obtained by repeated action of the raising operator on the usual coherent states. By using the density matrix approach, we have examined some interesting properties (including the nonclassicality) of these states, both in pure and also in mixed (thermal) cases.

In the paper, we have constructed and examined some properties of pair-coherent states of Barut–Girardello kind for two noninteracting subsystems of pseudoharmonic oscillators. The pseudoharmonic oscillator obeys SU(1,1) group symmetry, which was extensively used to study many problems in quantum optics and quantum information theory.

The BCS approach to superconductivity of bulk structures was tested for a thin metallic film. The main difference between the bulk and the film lies in the fact that two electron zones and consequently two types of Couper's pairs appear in film. The pairing of electrons of one zone gives several times higher critical temperature with respect to the critical temperature of the bulk, while the pairing of electrons of the second zone gives superconductivity

In the paper we examine some properties of the generalized coherent states of the Barut-Girardello kind. These states are defined as eigenstates of a generalized lowering operator and they are strongly dependent on the structure constants. Besides the pure coherent states we focused our attention on the mixed states one, which are characterized by different probability distributions. As some examples we consider the thermal canonical distribution

In the paper we have constructed and examined the properties of the Gazeau-Klauder coherent states (GK-CSs) for the pseudoharmonic oscillator (PHO), one of three possible kinds in order to define the coherent states for this oscillator potential. In the second part, we have examined some nonclassical properties of these states. Our attention has been concentrated on the mixed states (thermal states). The diagonal P-representation of the corresponding

In this paper we have showed that the qubit can be expressed through the coherent states. Consequently, a message, i.e. a sequence of qubits, is expressed as a tensor product of coherent states. In the quantum information theory and practice, only the code and key message are expressed as a sequence of qubits, i.e. through a quantum channel, the properly information will be transmitted by using a classical channel. Even if the most used coherent

The advanced methodology of Green's function method and application of this new methodology have resulted in a set of interesting conclusions concerning thin film properties. It has been concluded that thin films possess high superconductive, thermoisolation and acoustical isolation properties. It is also concluded that physical characteristics of thin films are spatially dependent and that this spatial dependence can be the basis for widening of