1,372 research outputs found

    Multipole (E1, M1, E2, M2) transition wavelengths and rates between states with n<= 6 in heliumlike carbon, nitrogen, oxygen, neon, silicon, and argon

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    Transition wavelengths and rates are given for E1, E2, M1, and M2 transitions between singlet and triplet S, P, D, and F states in heliumlike ions of astrophysical interest: carbon, nitrogen, oxygen, neon, silicon, and argon. All possible transitions between states with n <= 6 are considered. Wave functions and energies are calculated using the relativistic configuration-interaction (CI) method including both Coulomb and Breit interactions. For transitions to the ground state, the present theoretical wavelengths agree to five digits with precise measurements.Comment: 8 pages of text 97 pages of tables submitted to Atomic & Data Nuclear Datable

    Non-Perturbative String Equations for Type 0A

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    Well-defined non-perturbative formulations of the physics of string theories, sometimes with D-branes present, were identified over a decade ago, from a careful study of double scaled matrix models. Following recent work which recasts some of those old results in the context of type 0 string theory, a study is made of a much larger family of models, which are proposed as type 0A models of the entire superconformal minimal series coupled to gravity. This gives many further examples of important physical phenomena, including non-perturbative descriptions of transitions between D-branes and fluxes, tachyon condensation, and holography. In particular, features of a large family of non-perturbatively stable string equations are studied, and results are extracted which pertain to type 0A string theory, with D-branes and fluxes, in this large class of backgrounds. For the entire construction to work, large parts of the spectrum of the supergravitationally dressed superconformal minimal models and that of the gravitationally dressed bosonic conformal minimal models must coincide, and it is shown how this happens. The example of the super-dressed tricritical Ising model is studied in some detail.Comment: 29 pages LaTe

    Tachyon Condensation, Open-Closed Duality, Resolvents, and Minimal Bosonic and Type 0 Strings

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    Type 0A string theory in the (2,4k) superconformal minimal model backgrounds and the bosonic string in the (2,2k-1) conformal minimal models, while perturbatively identical in some regimes, may be distinguished non-perturbatively using double scaled matrix models. The resolvent of an associated Schrodinger operator plays three very important interconnected roles, which we explore perturbatively and non-perturbatively. On one hand, it acts as a source for placing D-branes and fluxes into the background, while on the other, it acts as a probe of the background, its first integral yielding the effective force on a scaled eigenvalue. We study this probe at disc, torus and annulus order in perturbation theory, in order to characterize the effects of D-branes and fluxes on the matrix eigenvalues. On a third hand, the integrated resolvent forms a representation of a twisted boson in an associated conformal field theory. The entire content of the closed string theory can be expressed in terms of Virasoro constraints on the partition function, which is realized as wavefunction in a coherent state of the boson. Remarkably, the D-brane or flux background is simply prepared by acting with a vertex operator of the twisted boson. This generates a number of sharp examples of open-closed duality, both old and new. We discuss whether the twisted boson conformal field theory can usefully be thought of as another holographic dual of the non-critical string theory.Comment: 37 pages, some figures, LaTe

    Education and training of library technicians in Czechoslovakia.

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    Czechoslovakia, since 1969, has been a federal state of two nations. The Czech Socialist Republic (CSR) covers the western areas of the country, traditionally known as Bohemia and Moravia. The eastern portion, Slovakia, forms the Slovak Socialist Republic (SSR). The educational system is controlled separately by the Ministers of Education in each Republic, but the Federal government takes a close interest in the state and development of educational work. Since World War II, substantial progress has been made in the development of education in Czechoslovakia, particularly in Slovakia where education had been comparatively neglected by the Austro-Hungarian government prior to the establishment of the Czechoslovakian Republic at the end of World War I. Emphasis has been placed on the development of higher education and, under the influence of the Russian system, with programmes of study adapted to the economic and cultural needs of the country as perceived by government planners. The aim of schools is to educate the youth and the working people to function as socially useful citizens of the republic. Nine years of compulsory basic schooling, beginning at the age of six, is followed by a four-year secondary programme. This programme can be completed in the gymnasia (general secondary schools), in vocational secondary schools, or in apprentice training schools. Students can take the school leaving certificate at any of these types of secondary schools. The first courses for librarians were offered in Czechoslovakia in 1918, and the first library school was established in 1920 under the control of the Ministry of Education and Culture. A school of librarianship was established in Charles University, Prague, in 1927, but it was re-established in the early 1950s following the amalgamation and re-organisation of three schools of librarianship in Prague. During the same period, in the early 1950s, the first of the specialist secondary schools was opened, the vocational secondary school for librarians in Brno. Today, there are two university schools of librarianship, in Prague and Bratislava, and three secondary schools for librarians, in Prague, Bratislava and Brno

    On the diameter of reconfiguration graphs for vertex colourings

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    The reconfiguration graph of the k-colourings of a graph G contains as its vertex set the proper vertex k-colourings of G, and two colourings are joined by an edge in the reconfiguration graph if they differ in colour on just one vertex of G. We prove that for a graph G on n vertices that is chordal or chordal bipartite, if G is k-colourable, then the reconfiguration graph of its ℓ-colourings, for â„“â©Ÿk+1, is connected and has diameter O(n2). We show that this bound is asymptotically tight up to a constant factor

    Energy levels and lifetimes of Nd IV, Pm IV, Sm IV, and Eu IV

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    To address the shortage of experimental data for electron spectra of triply-ionized rare earth elements we have calculated energy levels and lifetimes of 4f{n+1} and 4f{n}5d configurations of Nd IV (n=2), Pm IV (n=3), Sm IV (n=4), and Eu IV (n=5) using Hartree-Fock and configuration interaction methods. To control the accuracy of our calculations we also performed similar calculations for Pr III, Nd III and Sm III, for which experimental data are available. The results are important, in particular, for physics of magnetic garnets.Comment: 4 pages 1 tabl

    Third-order relativistic many-body calculations of energies and lifetimes of levels along the silver isoelectronic sequence

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    Energies of 5l_j (l= s, p, d, f, g) and 4f_j states in neutral Ag and Ag-like ions with nuclear charges Z = 48 - 100 are calculated using relativistic many-body perturbation theory. Reduced matrix elements, oscillator strengths, transition rates and lifetimes are calculated for the 17 possible 5l_j-5l'_{j'} and 4f_j-5l_{j'} electric-dipole transitions. Third-order corrections to energies and dipole matrix elements are included for neutral Ag and for ions with Z60. Comparisons are made with available experimental data for transition energies and lifetimes. Correlation energies and transition rates are shown graphically as functions of nuclear charge Z for selected cases. These calculations provide a theoretical benchmark for comparison with experiment and theory.Comment: 8 page

    Combined effect of coherent Z exchange and the hyperfine interaction in atomic PNC

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    The nuclear spin-dependent parity nonconserving (PNC) interaction arising from a combination of the hyperfine interaction and the coherent, spin-independent, PNC interaction from Z exchange is evaluated using many-body perturbation theory. For the 6s-7s transition in 133Cs, we obtain a result that is about 40% smaller than that found previously by Bouchiat and Piketty [Phys. Lett. B 269, 195 (1991)]. Applying this result to 133Cs, leads to an increase in the experimental value of nuclear anapole moment and exacerbates differences between constraints on PNC meson coupling constants obtained from the Cs anapole moment and those obtained from other nuclear parity violating experiments. Nuclear spin-dependent PNC dipole matrix elements, including contributions from the combined weak-hyperfine interaction, are also given for the 7s-8s transition in 211Fr and for transitions between ground-state hyperfine levels in K, Rb, Cs, Ba+, Au, Tl, Fr, and Ra+.Comment: Revtex4 preprint 19 pages 4 table

    Age regression from soft aligned face images using low computational resources

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    The initial step in most facial age estimation systems consists of accurately aligning a model to the output of a face detector (e.g. an Active Appearance Model). This fitting process is very expensive in terms of computational resources and prone to get stuck in local minima. This makes it impractical for analysing faces in resource limited computing devices. In this paper we build a face age regressor that is able to work directly on faces cropped using a state-of-the-art face detector. Our procedure uses K nearest neighbours (K-NN) regression with a metric based on a properly tuned Fisher Linear Discriminant Analysis (LDA) projection matrix. On FG-NET we achieve a state-of-the-art Mean Absolute Error (MAE) of 5.72 years with manually aligned faces. Using face images cropped by a face detector we get a MAE of 6.87 years in the same database. Moreover, most of the algorithms presented in the literature have been evaluated on single database experiments and therefore, they report optimistically biased results. In our cross-database experiments we get a MAE of roughly 12 years, which would be the expected performance in a real world application
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