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Wyszukujesz frazę "Lulek, T." wg kryterium: Autor


Tytuł:
Spin-Orbit Coupling for f-Electrons in a Crystalline Field
Autorzy:
Lulek, T.
Tematy:
71.70.Ch
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Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1929779.pdf  Link otwiera się w nowym oknie
Opis:
The notion of a spin-orbit interaction arises from consideration of dynamics of multielectron atoms, i.e. systems of N electrons in a spherical potential. This notion is essentially a single-particle one. We sketch its origin as a second-order correction when Dirac four-component wave equations for an electron in external electromagnetic fields are simplified to the two-component Pauli spinors. The constraints in spinorial degrees of freedom consist, roughly speaking, in neglecting the small component of the electron four-function. The spin-orbit interaction term serves to compensate effects of the small component. The crystalline field induces some deviations from spherical symmetry of an isolated atom, which yields some modifications of the spherical form of the spin-orbit interaction operator. These modifications can be described in terms of a number of tensor operators adapted to appropriate chains of subgroups of the spherical symmetry group. We present a classification of independent tensor operators and discuss the relevant parameters for f-ions.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Wigner-Racah Description of the Free-Electron Model
Autorzy:
Lulek, T.
Tematy:
02.20.+b
71.45.-d
75.10.Lp
75.20.-g
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Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1891909.pdf  Link otwiera się w nowym oknie
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.
Dostawca treści:
Biblioteka Nauki
Artykuł
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.
Tematy:
02.20.+b
02.40.+m
03.20.+i
61.50.Em
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Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1920925.pdf  Link otwiera się w nowym oknie
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.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Racah Recoupling Matrices for System of Two Free Electrons Confined To Single Star
Autorzy:
Lulek, T.
Kłos, J.
Tematy:
02.20.-a
31.10.+z
75.10.Lp
75.20.-g
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Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1945688.pdf  Link otwiera się w nowym oknie
Opis:
Racah-Wigner type of calculus is adapted to the system of two free electrons in a cubic box, confined to a single star p00 of quasimomentum. Various coupling schemes (LS-like, jj-like, and transitive) have been reviewed in analogy to the case of a free atom. Racah recoupling matrices are calculated explicitly, and their quantum-mechanical meaning is exposed in terms of octahedral multipoles.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Rarefied Band in Spectrum of Two-Magnon States of Heisenberg Ferromagnet of Clock Dial Plate
Autorzy:
Lulek, T.
Wal, A.
Tematy:
05.50.+q
75.30.Ds
02.20.-a
75.Jm
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Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1933552.pdf  Link otwiera się w nowym oknie
Opis:
The Heisenberg isotropic exchange Hamiltonian with the nearest neighbour interactions for the ring of N = 12 nodes (the clock dial plate) with the spin 1/2 has been diagonalized within the manifold of all 66 two-magnon excitations from the ferromagnetic ground state. The spectrum consists of 5 full bands, i.e. bands defined over the whole Brillouin zone, and a single band which is doubly rarefied, i.e. defined only for even values of quasimomentum. The rarefied band is found to be dispersionless outside the centre of the Brillouin zone. It separates two bands of "weakly bounded" spin waves from two other which are "weakly antibounded". The last remaining band is situated below this collection of scattered spin waves, and describes two tightly bounded spin deviations. The spectrum exhibits dispersion, but it is degenerate (singlet and quintet) at the boundary of the Brillouin zone.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Pentagonal Ring - Galois Extensions and Crystallography
Autorzy:
Labuz, M.
Lulek, T.
Tematy:
75.10.Jm
03.65.Fd
03.67.Lx
02.10.Ud
02.10.De
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Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1033704.pdf  Link otwiera się w nowym oknie
Opis:
The Galois symmetry of exact Bethe Ansatz eigenstates for magnetic pentagonal ring is shown to bear a close analogy to some crystallographic constructions. Automorphisms of number field extensions associated with these eigenstates prove to be related to choices of the Bravais cells in the finite crystal lattice ℤ₂×ℤ₂, responsible for extension of the cyclotomic field by the Bethe parameters.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Wreath Product in Factorization of Holosymmetric Group
Autorzy:
Florek, W.
Lulek, T.
Tematy:
61.50.Em
02.20.+b
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Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1887747.pdf  Link otwiera się w nowym oknie
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.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Coupled States of the System of Two Free Electrons on a Single Star
Autorzy:
Walcerz, S.
Lulek, T.
Tematy:
02.20.+b
71.45.-d
75.10.Lp
75.20.-g
Pokaż więcej
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1891910.pdf  Link otwiera się w nowym oknie
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.
Dostawca treści:
Biblioteka Nauki
Artykuł
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.
Tematy:
02.20.+b
02.40.+m
03.20.+i
11.30.Er
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Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1920926.pdf  Link otwiera się w nowym oknie
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.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Matrix Representation of Constants of Motion for One-Dimensional Heisenberg Magnet
Autorzy:
Jakubczyk, P.
Labuz, M.
Lulek, T.
Tematy:
03.65.Aa
75.10.Jm
Pokaż więcej
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1402564.pdf  Link otwiera się w nowym oknie
Opis:
We demonstrate an exact diagonalization of the one-dimensional Heisenberg magnet in terms of algebraic Bethe Ansatz. We point out, by a polynomial expansion of the transfer matrix with respect to spectral parameter, a complete set of observables for classification of all eigenstates. We introduce an application of our approach on the example of the Heisenberg magnet consisting of four qubits, including its constants of motion, density matrices and complete classification of eigenstates.
Dostawca treści:
Biblioteka Nauki
Artykuł

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