Vibrational structure of quasiline fluorescence and absorption spectra of bisanthene molecules

The quasiline spectra of the fluorescence and absorption of bisanthene in n-hexane are obtained at 77 and 4.2 K, and their vibration analysis is carried out. Substantial violation of the mirror symmetry of the fluorescence and S₁ ← S₀-absorption bands with respect to both the frequencies and intensities is found. This allowed the conclusion that the S₂-level is localized in the region of vibronic sublevels of the S₁-state with . Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 4, pp. 488–491, July–August, 2000.     

Photoelasticity in quasicrystals

The maximum number of non-vanishing and independent second order photoelastic coefficients required by the seven pentagonal and the two icosahedral point groups 5(C₅), (S₁₀), (C_5h ), m2(D_5h ), 52(D₅), 5m(C_5v ), 2m(D_5d ); 235(I), 2/m (I _h )—that describe the quasicrystals symmetry groups in two and three dimensions—is obtained. The schemes of non-vanishing and independent coefficients have been calculated and listed. Finally the results of this group-theoretical study are briefly discussed.     

World spinors—Construction and some applications

The existence of a topological double-covering for the GL(n, R) and diffeomorphism groups is reviewed. These groups do not have finite-dimensional faithful representations. An explicit construction and the classification of all (n, R), n=3,4 unitary irreducible representations is presented. Infinite-component spinorial and tensorial fields, “manifields”, are introduced. Particle content of the ladder manifields, as given by the (3, R) “little” group, is determined. The manifields are lifted to the corresponding world spinorial and tensorial manifields by making use of generalized infinite-component frame fields. World manifields transform w.r.t. corresponding representations, which are constructed explicitly. Supported in part by the Science Foundation (Belgrade).     

Antihydrogen synthesis: A progress report

The main suggested routes for atomic antihydrogen ( ) formation will be reviewed in a pedestrian fashion. These are the following reactions: , and (iii) . The present status of the projects related to these reactions, as well as the projects' experimental scope, will also be discussed or referred to. Some speculations will be made regarding the physics that can be yielded by an antihydrogen probe.     

Laser goniophotometric stokes polarimeter

An automated Stokes polarimeter of the dynamic type is created to measure the polarization characteristics of radiation emitted, reflected, and scattered by objects at different angles to a surface. An analysis of the versions of processing of measurement resuls has shown that the dependence of a random error in determination of the parameters on the number of positions N of a quarter-wave plate, at which the radiation intensity is measured, is of a similar nature as the dependence on the number of independent measurements of the same quantity . B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68 Skorina Ave., Minsk., 220072, Belarus, e-mail: tsaruk@dragon.bas-net.by. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 6, pp. 869–874, November–December, 1999.     

Modules over\mathfrak{U}_q (\mathfrak{s}\mathfrak{l}_2 )

The restricted quantum universal enveloping algebra decomposes in a canonical way into a direct sum of indecomposable left (or right) ideals. They are useful for determining the direct summands which occur in the tensor product of two simple . The indecomposable finite-dimensional are classified and located in the Auslander-Reiten quiver.     

Bethe subalgebras in twisted Yangians

We study analogues of the Yangian of the Lie algebra for the other classical Lie algebras and . We call them twisted Yangians. They are coideal subalgebras in the Yangian of and admit homomorphisms onto the universal enveloping algebras U( ) and U( ) respectively. In every twisted Yangian we construct a family of maximal commutative subalgebras parametrized by the regular semisimple elements of the corresponding classical Lie algebra. The images in U( ) and U( ) of these subalgebras are also maximal commutative.     

High resolution measurement of bragg cut-off in beryllium

Bragg cut-off for plane of polycrystalline beryllium of various lengths of 300 and 116 K has been measured with an energy resolution of 5 μeV. The natural width of the cut-off is 12.5±1.5 μeV, independent of temperature and length of beryllium and also of physical characteristics and certain metallurgical treatments of the powder. Such blocks of beryllium would be suitable for designing a ΔT-window spectrometer with resolution ⩾20 μeV. Bragg cut-offs corresponding to (0002) and planes of beryllium have been separated for the first time. These can also be used for producing additional energy windows in a ΔT-window spectrometer, thus increasing its efficiency. Paper entitled ‘ΔT-window spectrometer’ will appear in the November issue of Pramana.     

Dependence of the Electronic Spectra of the Chlorin Molecule on the Degree of Alternation of the Macrocycle Bond Lengths

The geometric structure of the chlorin molecule (H₂Ch) has been calculated by the restricted and unrestricted Hartree-Fock (RHF and UHF) methods with an AM1 Hamiltonian. Transformations of this molecule into excited electronic states have been calculated by the CNDO/S method. The RHF method without symmetry restrictions gives a plane structure for the chlorin macrocycle with an alternation of the lengths of the bonds along the 18-member azacyclopolyene and a C_1h symmetry for the molecule as a whole. The level of the first excited state Q₁ of this structure is substantially shifted (δ ≅ +4000 cm⁻¹) relative to the Q_x level of porphin (H₂P) toward shorter waves, which is in contradiction with the experimental data, according to which this shift is long-wave and is equal to δ = −400 to −550 cm⁻¹. The optimization of the geometry of H₂Ch by the UHF method has shown that it has a structure with an 18-member azacyclopolyene with bonds of equal lengths and a D_2h symmetry. For this geometry of H₂Ch the calculated shift of the Q_x level, equal to δ = −70 cm⁻¹, is bathochromic and the position of the Q_y level is practically exactly coincident with the experimental one. For the geometry calculated by the RHF method with restrictions on the D_2h symmetry of the 18-member azacyclopolyene δ = +180 cm⁻¹, and for the geometry calculated with restrictions on the highest C_2v symmetry of the H₂Ch molecule δ = +620 cm⁻¹. The latter result shows that the “natural” requirement for the C_2v symmetry of the H₂Ch macrocycle, which is frequently used in various calculations, is inadequate to achieve a quantitative agreement between the calculation and experimental data and, in this case, the lengths of the bonds along the 18-member azacyclopolyene are not equal. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 339–347, May–June, 2005.     

A mathematical condition for a sublattice of a propositional system to represent a physical subsystem,with a physical interpretation

We display three equivalent conditions for a sublattice, isomorphic to aP , of the propositional systemP() of a quantum system to be the representation of a physical subsystem (see [1]). These conditions are valid for dim 3. We prove that one of them is still necessary and sufficient if dim <3. A physical interpretation of this condition is given.Wetenschappelijke medewerkers bij het Interuniversitair Instituut voor Kernwetenschappen (in het kader van navorsingsprogramma 21 EN).     

Space tensors in general relativity I: Spatial tensor algebra and analysis

A pair (M, Γ) is defined as a Riemannian manifold M of normal hyperbolic type carrying a distinguished time-like congruence Γ. The spatial tensor algebraD associated with the pair (M, Γ) is discussed. A general definition of the concept of spatial tensor analysis over (M, Γ) is then proposed. Basically, this includes a spatial covariant differentiation and a time-derivative , both acting onD and commuting with the process of raising and lowering the tensor indices. The torsion tensor fields of the pair are discussed, as well as the corresponding structural equations. The existence of a distinguished spatial tensor analysis over (M, Γ) is finally established, and the resulting mathematical structure is examined in detail. This work was assisted by funds from the C.N.R. under the aegis of the activity of the National Group for Mathematical Physics.     

Superconformal current algebras and their unitary representations

A natural supersymmetric extension is defined of the current (= affine Kac-Moody Lie) algebra ; it corresponds to a superconformal and chiral invariant 2-dimensional quantum field theory (QFT), and hence appears as an ingredient in superstring models. All unitary irreducible positive energy representations of are constructed. They extend to unitary representations of the semidirect sumS (G) of with the superconformal algebra of Neveu-Schwarz, for , or of Ramond, for =0.On leave of absence from the Institute for Nuclear Research and Nuclear Energy of the Bulgarian Academy of Sciences, BG-1184 Sofia, Bulgaria     

New connection between spinors and geometry

We study those nonlinear infinitesimal realizations ofSL(2,C) that leave invariant the quadratic function of the four-velocity components of a particle. These transformations are defined as maps of a larger manifold, which includes the four-velocity space, into itself in such a way that transformations of the depend upon other functions in the manifold. The requirement that remain invariant limits the types of other functions that can contribute in the transformation of the . However, among those allowed are the spinors and a three-dimensional space that transforms nonlinearly and recently associated with electric charge. We point out and explore two interesting aspects of these nonlinear realizations. First, they generally necessitate interactions since is not a covariant equation. Second, with superposition of solutions, exact measurement of the four-velocity or space-time position, is impossible. This and related features of nondeterministic measurement inherent to these realizations are discussed.     

Magnetic field effect on free and bound excitons in chalcopyrite CuInS<Subscript>2</Subscript>

The effect of a strong magnetic field (induction up to 10 T) on free and bound excitons in CuInS₂ single crystals is studied. A diamagnetic shift to higher energies is observed in the luminescence and reflectance spectra for free-exciton lines A_LPB ≈ 1.5348 eV, A_UPB ≈ 1.5361 eV, and BC ≈ 1.557 eV. The diamagnetic shifts of free-exciton lines A_LPB, A_UPB, and BC provide a basis for estimating the exciton reduced masses = 0.131m₀, = 0.13 4m₀, and μ_BC = 0.111m₀, respectively. Bound-exciton lines in luminescence spectra are split under the influence of the magnetic field. The magnitude of the Zeeman effect (g-factor of the magnetic splitting) is estimated. __________ Translated from Zhurnal Prikladnoi Spektroskopii Vol. 74, No. 3, pp. 373–377, May–June, 2007.     

Elastic wave surfaces for the (111) plane of cubic crystals

The nature of inverse velocity surfaces as well as energy surfaces for elastic wave propagation in the (111) plane have been studied for a number of cubic crystals. The sections of inverse velocity surfaces by the (111) plane exhibit six-fold symmetry in all cases. Cuspidal edges are exhibited with a six-fold symmetry by both the slow transverse and fast transverse shear modes in the (111) plane, unlike the case of the (100) and (110) planes for which only the slow transverse shear mode exhibits cuspidal edges. The slow transverse mode energy surface exhibits cuspidal edges along direction or an equivalent symmetry direction. The inverse velocity surfaces of the A-15 compounds exhibit unusually large inflexions for the slow transverse mode, whereas their energy surfaces have large cuspidal edges which intersect each other resulting in common regions of cusps.     

Scanning electron microscopic studies on different habits of gel grown doped manganese carbonate crystals

The effect of impurities on the growth of manganese carbonate crystals has been studied. Stereophotogrammetric analysis showed that all crystal faces have the same Miller indices and the peanut-shaped forms are twins with twin axis 0001.     

The expected magnitude of simultaneous parity and time violation in nuclear systems

Time (T) and simultaneous parity-time (PT) symmetry violations in the nuclear system generally cause the gamma ray multipole mixing ratios to acquire imaginary components. These complex phases may then be measured experimentally by virtue of the resulting gamma ray distributions. However, the true significance of such experiments may only be assessed once the imaginary mixing ratios have been related theoretically to the coupling constant of some fundamental, symmetry violating, interaction. We discuss, in a quantitative way, the various aspects of this relationship. To illustrate this further we examine the case of the 1189 keV transition in¹⁸²W. For this transition we predict the experimentally observable mixing ratio to have a parity (P) violating real part of ≅5×10⁻⁵ and a PT violating imaginary part of , where is the strength of the isovector PT violating pion-nucleon coupling. An upper limit to this coupling of ≲3×10⁻¹⁰ may be obtained from the electric dipole moment of the neutron.     

Magnetic studies of the dislocation structure of iron single crystals deformed at 195K and 77K

Measurements of the coercive field, the initial susceptibility and the reversible susceptibility in the approach to ferromagnetic saturation show that during low-temperature deformation of iron single crystals mainly screw dislocations are created. Long-range internal stresses are found to be significantly smaller than in crystals deformed at room temperature. Macroscopic slip occurs on several slip systems. In the parabolic region of the work-hardening curves at 195 K the relation is valid, where τ isthe shear stress andN is the dislocation density. In the region of saturation of the shear stress the dislocation density further increases. After room-temperature prestrain the relation appears to hold for 77K-deformation also. Exhaustion hardening of edge dislocation is found at the beginning of the low-temperature deformation.     

Regularized,continuum Yang-Mills process and Feynman-Kac functional integral

Giving an ultraviolet regularization and volume cut off we construct a nuclear Riemannian structure on the Hilbert manifold of gauge orbits. This permits us to define a regularized Laplace-Beltrami operator on and an associated global diffusion in governed by . This enables us to define, via a Feynman-Kac integral, a Euclidean, continuum regularized Yang-Mills process corresponding to a suitable regularization (of the kinetic term) of the classical Yang-Mills Lagrangian onT .On leave of absence from Zaragoza University (Spain)Laboratoire associé au CNRS     

Renormalizable theories from nonrenormalizable interactions

By using Kikkawa’s method the equivalence of the nonrenormalizable pair interaction to a renormalizable theory is proved. Equivalence relationships between a few other nonrenormalizable and renormalizable interactions are also indicated.