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731.
We define energy (E) and compute its values for gravitational systems involving terms quadratic in curvature. There are significant differences, both conceptually and concretely, from Einstein theory. For D=4, all purely quadratic models admit constant curvature vacua with arbitrary Lambda, and E is the "cosmological" Abbott-Deser (AD) expression; instead, E always vanishes in flat, Lambda=0, background. For combined Einstein-quadratic curvature systems without explicit Lambda-term vacuum must be flat space, and E has the usual Arnowitt-Deser-Misner form. A Lambda-term forces unique de Sitter vacuum, with E the sum of contributions from Einstein and quadratic parts to the AD form. We also discuss the effects on energy definition of higher curvature terms and of higher dimension. 相似文献
732.
We define formally smooth coalgebras and we study their relation with hereditary coalgebras. The main result of the paper
establishes that a coalgebra with separable coradical is hereditary if and only if it is formally smooth if and only if it
is the cotensor coalgebra
, where C0 is the coradical of C and N is a certain (C0,C0)–bicomodule.
Presented by A. Verschoren
Mathematics Subject Classifications (2000) primary: 16W30; secondary: 18G20.
D. Ştefan: This author thanks the members of the Algebra Department of the University of Granada for their warm hospitality.
He is especially grateful to Pascual Jara for the kind invitation to visit University of Granada. This research was partially
supported by CERES, Contract 4-147. 相似文献
733.
M. Avrigeanu M. IvaŞcu V. Avrigeanu 《Zeitschrift für Physik A Hadrons and Nuclei》1990,335(3):299-313
Consistent pre-equilibrium emission and statistical model calculations of fast neutron induced reaction cross sections are used to validate nuclear level densities for excitation energies up to 40 MeV in the mass regionA ?50. A “composed” level density approach has been employed by using the back-shifted Fermi gas model for excitation energies lower than 12 MeV and a realistic analytical formula for higher excitations. In the transition region from the BSFG model range to that of full applicability of the realistic formula, an interpolation between the predictions of the two models is adopted. The interpolation rule, suggested by microscopic level density calculations, has been validated through the comparison of the calculated and experimental cross sections. 相似文献
734.
The energy positions and the wavefunctions of 2S autoionizing states of the neutral lithium atom have been calculated using the derivative method with a Hylleraas-type basis set. Computed energies are in good agreement with experiment and with other theoretical results. 相似文献
735.
(–)—Crinine, C16H17NO3, is an alkaloid extracted from the bulbs of Pancratium maritimum L. (Amaryllidaceae). The compound crystallizes in the space group P212121 with cell dimensions a = 6.040(1), b = 12.382(1), c = 17.861(2) Å, with Z = 4. The molecule has five rings and an OH group. The N-containing, five-membered ring and the D ring have envelope conformations. The A and B rings have distorted chair and half-chair conformations, respectively. 相似文献
736.
Mihai Şabac 《Journal of Functional Analysis》1983,52(3):303-314
Some results concerning the operatorially irreducible, topologically irreducible, operatorially and topologically irreducible representations of a class of infinite-dimensional Lie algebras by bounded operators in a complex Banach space are obtained. 相似文献
737.
738.
739.
Ultrasound is known to enhance solid/liquid reactions. This paper deals with the investigation of the dissolution of phosphate rock in nitric acid, in the absence and presence of ultrasound. The reaction is first-order with respect to H+ and activation energy equal to 16 kJ/mol in both cases. The effect of ultrasound is on the pre-exponential factor A. An empirical relation is given, which relates rate constant to ultrasound power. 相似文献
740.
In this study, the concept of a statistically D-bounded sequence in a probabilistic normed (PN) space endowed with the strong topology is introduced and its basic properties are investigated. It is shown that a strongly statistically convergent sequence and a strong statistically Cauchy sequence are statistically D-bounded under certain conditions. A sequence which goes far away from the limit point infinitely many times and presents random deviations in a PN space may be handled with the tools of strong statistical convergence and statistical D-boundedness. 相似文献