Approximate ground state in a model with spontaneous symmetry breakdown

The spontaneous symmetry breakdown is treated by means of a variational approach. Use is made of coherent states of Glauber and of pairing states of BCS-type as the translationally invariant vacuum states for the discussion of the real scalar field ⁴ withm ₀ ² 0. The first type of trial states reproduces the usual approach to spontaneous symmetry breakdown (-) in the tree approximation (which is possible only form ₀ ² <0), while the second type of trial states offers the possibility of spontaneous symmetry breakdown even form ₀ ² =0.     

A model of oxide film originating at thermal oxidation of GaAs

In this paper an approximative procedure to determine of the most probable model of oxide film originating at thermal oxidation of GaAs single-crystal samples within the temperature range 480–530 °C is proposed. It is shown that the system presented is more complicated if compare with that presumed previously.     

Longitudinal magnetoresistance of platinum: The influence of lattice vacancies

The longitudinal magnetoresistance of polycrystalline platinum wires has been measured in magnetic fields up to 45 kOe at liquid helium temperatures. The deviations from Kohler's rule found depend on the concentration of quenched-in vacancies, and are interpreted as due to the contribution of single vacancies in platinum to the small angle scattering of electrons. The small-angle scattering may also be responsible for the linear magnetoresistance of platinum in high magnetic fields.     

Non-uniqueness of the heat current operator and the hopping thermoelectric and Nernst-Ettingshausen effects in amorphous semiconductors

The Hardy correction in the heat current operator is generalized to the case of non-zero electron-phonon coupling constantg. It is then shown that not only the lowest (minus first) order but also the fist order contribution ing to the thermoelectric power of amorphous semiconductors in the hopping regime disappears. Consequently, since the lowest (zero) order contribution to the thermoelectric effects in the magnetic field yields no Nernst-Ettingshausen effect in these materials, the last effect is of the second order ing, at least.     

The decay of the 23min131Sb

The direct and the coincidence spectra of gamma-rays from the¹³¹Sb decay have been measured by means of different Ge(Li) detectors. The Sb sources have been prepared from mixture of²³⁵U thermal neutron fission products. The proposed level scheme of the¹³¹Te nuclei is based on the coincidence measurements, the analysis of the energy sums and the reaction data. The 49 of the total number of 64 gamma-rays observed have been placed in the present decay scheme. Properties of the some levels in¹³¹Te are compared with those observed in other oddmass Te isotopes. A probable structure of some of the excited states in¹³¹Te is discussed.     

Determination of the atomic-state population in A Kr-Br2 mixture

The atomic-state populations of the 5s[1$\text{1}\text{2}$]° metastable level of Kr and of the 5s²P_{$\text{3}\text{2}$} resonant level of Br in a Kr-Br₂ mixture have been determined as functions of current strength. Occurrence of energy transfer from the Kr-level to the Br-level has been verified.     

Die Röntgenolumineszenz Von NaCl-Kristallen Mit Beimengungen Von Elementen Der Eisengruppe

Zusammenfassung Es werden Versuchsergebnisse des Studiums der Röntgenolumineszenz (RL) von NaCl-Kristallen mit Beimengungen von Elementen der Eisengruppe (Fe, Co, Ni) angeführt. Die Kristalle wurden aus der Lösung und aus der Schmelze gezüchtet. Das Vorkommen und das Höhenverhältnis der einzelnen Emissionsbanden werden diskutiert.

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NaCl

NaCl Fe, Co, Ni. . .

     

Some applications of the discrete fourier transform to problems of crystal lattice deformation II

The method elaborated in [1] is applied to the solution of some problems for a plane lattice and the linear chain. The method can be used to investigate deformations around crystal lattice defects.

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, [1] . .

     

Theory of tamm surface states in approximation higher than tight-binding approximation

The influence of the non-zero value of exchange integrals between Wannier functions, localized in non-neighbouring elementary cells (higher approximation than tight-binding), on the conditions of existence of Tamm surface states and the position of the energy level corresponding to the surface state is shown.

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, ( ) , .

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This paper is part of M. Tomáek's candidate's thesis.     

Some applications of the discrete fourier transform to problems of crystal lattice deformation I

The theory of the discrete Fourier transform [1], [2] is applied in solving a system of difference equations describing the positions of atoms in a deformed crystal lattice. The crystal lattice is approximated by the Born-Kármán model modified to include the internal energy of the undeformed crystal.

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, , , [1] [2]. - , , .