Results 91 to 100 of about 290 (118)
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Homothety groups in space-time
General Relativity and Gravitation, 1990The authors investigate Lorentzian space-times which admit an r- dimensional Lie algebra of homothetic vector fields at least one of which is proper homothetic (i.e., it is not a Killing vector field). A complete description of the situation is obtained if \(r\geq 6\) and some results are given for \(r\leq 5\).
Hall, G. S., Steele, J. D.
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Generalized rule of homothety of ideal memristors and their siblings
2015 European Conference on Circuit Theory and Design (ECCTD), 2015The pinched hysteresis loop area increasing with the square of the frequency of driving harmonic signal on the assumption of constant charge delivered within the half-period belongs to the less known fingerprints of ideal memristor. The paper proves that this fingerprint holds not only for the harmonic excitation: the v-i characteristic of a memristor ...
Zdenek Biolek +5 more
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Formalism for spacetimes with a homothety
Classical and Quantum Gravity, 2002In this paper, the formalism developed by Fayos and Sopuerta for the study of spacetimes admitting a Killing vectors is generalized in three ways: the case of homothetic vector is covered, the tetrad is not assumed to be aligned with the (homothetic) bivector and the tetrad is not assumed to be normalized.
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, 2003 Simply-transitive homothety groups
General Relativity and Gravitation, 1991The author uses the spin-coefficient formalism of Penrose and Rindler to obtain spacetimes admitting a simply-transitive group of homotheties. Vacuum metrics with a five-dimensional homothety group are also considered.
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Singularities and homothety groups in spacetime
Classical and Quantum Gravity, 1988Some inaccuracies in the article of \textit{C. B. Collins} and \textit{J. M. Lang} in ibid. 3, 1143-1150 (1986; Zbl 0604.53045)] are corrected and commented here leading to a more general version of the main result given there.
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All vacuum Bianchi I metrics with a homothety
Classical and Quantum Gravity, 1991All vacuum metrics with a four-parameter homothety group containing a three-dimensional Abelian subgroup are found. These include the Kasner family of metrics, metrics related to the Kasner family by complex transformations (which include a family of vacuum metrics found by Lewis in 1932 and a metric found by Petrov in 1962 to be the only vacuum metric
C B G McIntosh, J D Steele
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Characterization of Bounded Sets in Terms of Asymptotic Cones and Homotheties
Mathematical Notes, 2020The author presents characterizations of bounded sets in a Banach space \(X\), based on the asymptotic cone defined for a subset \(A\subset X\) as \(A_{\infty}=\{x\in X:\exists t_{n}>0\), \(t_{n}\rightarrow 0\), \(\exists x_{n}\in A\), \(\lim_{n\rightarrow \infty }t_{n}x_{n}=x\}\).
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Lumen areas and homothety factor influence airway resistance in COPD
Respiratory Physiology & Neurobiology, 2010The remodelling process of COPD may affect both airway calibre and the homothety factor, which is a constant parameter describing the reduction of airway lumen (h(d): diameter of child/parent bronchus) that might be critical because its reduction would induce a frank increase in airway resistance.
Bokov, Plamen +8 more
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Homotheties and Spiral Similarities
Problem Books in Mathematics, 2022Ionut Onisor +2 more
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