Temat: 02.20.+b - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: Wreath Product in Factorization of Holosymmetric Group
Autorzy:: Florek, W.
Lulek, T.
Powiązania:: https://bibliotekanauki.pl/articles/1887747.pdf
Data publikacji:: 1991-06
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:: 61.50.Em
02.20.+b
Opis:: The holosymmetric group Q of an n-dimensional crystal lattice determined by a given lattice basis B is considered. This group is contained in the n-dimensional orthogonal group O(n) so its elements preserve the orthogonality of basis vectors and their lengths. These conditions yield the decomposition of lattice basis into orthogonal sublattices and next the factorization of the holosymmetric group, which can be written as a direct product of complete monomial groups of k-dimensional (k ≤ n) holosymmetric groups. Simple, decomposable and primitive holosymmetric groups are discussed. The results for n ≤ 4 are presented.
Źródło:: Acta Physica Polonica A; 1991, 79, 6; 843-852
0587-4246
1898-794X
Pojawia się w:: Acta Physica Polonica A
Dostawca treści:: Biblioteka Nauki

Artykuł

Skocz do pozycji: 2.

Tytuł:: Mac Lane Method for Determination of Extensions of Finite Groups. I. A Review in the Context of Structure of Condensed Matter
Autorzy:: Lulek, T.
Powiązania:: https://bibliotekanauki.pl/articles/1920925.pdf
Data publikacji:: 1992-09
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:: 02.20.+b
02.40.+m
03.20.+i
61.50.Em
Opis:: The problem of classification of all extensions of a finite group Q by an Abelian group T has been reviewed using cohomology of groups and fibre bundle picture. The relevance of this problem in condensed matter physics has been pointed out in the context of crystallography and gauge fields. The Mac Lane method of an effective construction of the corresponding second cohomology group as the quotient group of all operator homomorphisms vs. crossed homomorphisms from some free groups to T has been described in detail.
Źródło:: Acta Physica Polonica A; 1992, 82, 3; 377-393
0587-4246
1898-794X
Pojawia się w:: Acta Physica Polonica A
Dostawca treści:: Biblioteka Nauki

Artykuł

Skocz do pozycji: 3.

Tytuł:: Mac Lane Method for Determination of Extensions of Finite Groups. II. An Example for the Dihedral Group D$\text{}_{2}$
Autorzy:: Lulek, T.
Chatterjee, R.
Powiązania:: https://bibliotekanauki.pl/articles/1920926.pdf
Data publikacji:: 1992-09
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:: 02.20.+b
02.40.+m
03.20.+i
11.30.Er
Opis:: The Mac Lane method of classification and construction of all extensions of a group Q by an Abelian group T is demonstrated on the case Q = D$\text{}_{2}$, T = C$\text{}_{2}$. Constructions involving free groups and operator homomorphisms are performed in detail, and the complete list of resulting extensions is given. It is shown that there are 8 classes of gauge equivalency, and they fall into 4 classes of isomorphism. The role of gauge transformations is pointed out. Physical contexts of various constructions are reviewed. A comparison with the direct cohomology definitions is performed.
Źródło:: Acta Physica Polonica A; 1992, 82, 3; 395-406
0587-4246
1898-794X
Pojawia się w:: Acta Physica Polonica A
Dostawca treści:: Biblioteka Nauki

Artykuł

Skocz do pozycji: 4.

Tytuł:: Wigner-Racah Description of the Free-Electron Model
Autorzy:: Lulek, T.
Powiązania:: https://bibliotekanauki.pl/articles/1891909.pdf
Data publikacji:: 1991-12
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:: 02.20.+b
71.45.-d
75.10.Lp
75.20.-g
Opis:: A version of Wigner-Racah type of approach is proposed for the model of a free-electron gas in a cubic box. The approach bases on the structure of fibre bundle in description of states of a single electron. Contrary to the tight binding model, the base of the bundle is the reciprocal space rather than the positional one. An elementary quantity of the approach is the star of quasi-momentum. Such a treatment reveals the degeneracy of energy levels of the system of N electrons, in particular of the ground Fermi level, for an uncomplete filling of stars. The associated classification of energy levels and corresponding states can be performed within an atomic-like Wigner-Racah scheme.
Źródło:: Acta Physica Polonica A; 1991, 80, 6; 769-779
0587-4246
1898-794X
Pojawia się w:: Acta Physica Polonica A
Dostawca treści:: Biblioteka Nauki

Artykuł

Skocz do pozycji: 5.

Tytuł:: Coupled States of the System of Two Free Electrons on a Single Star
Autorzy:: Walcerz, S.
Lulek, T.
Powiązania:: https://bibliotekanauki.pl/articles/1891910.pdf
Data publikacji:: 1991-12
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:: 02.20.+b
71.45.-d
75.10.Lp
75.20.-g
Opis:: A classification scheme of quantum states for the system of two free electrons in a cubic box, confined to a single star of quasi-momentum is proposed within a Racah-Wigner type of approach. Coupling of angular momenta of the atomic case is here substituted by Mackey theorem for transitive representations, which provides a crystalline analogue of orbital angular momentum - the resultant orbit of the geometric symmetry group. The action of the Pauli group is combined with that of the octahedral group which yields the connection between spin (i.e. the singlet or triplet pairing of electrons) and statistic of the positional factor. Resultant singlets and doublets - irreducible representations of the octahedral group, exhibit an ordinary Landau diamagnetic behaviour, whereas triplets are paramagnetic. A relation between the Mackey star and the star of resultant momentum is discussed.
Źródło:: Acta Physica Polonica A; 1991, 80, 6; 781-792
0587-4246
1898-794X
Pojawia się w:: Acta Physica Polonica A
Dostawca treści:: Biblioteka Nauki

Artykuł

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