scholarly journals On new characterization of inextensible flows of space-like curves in de Sitter space

2016 ◽  
Vol 14 (1) ◽  
pp. 946-954 ◽  
Author(s):  
Mustafa Yeneroğlu
Keyword(s):  
De Sitter Space ◽  
De Sitter ◽  
Practical Applications ◽  
Inextensible Flows

AbstractElastica and inextensible flows of curves play an important role in practical applications. In this paper, we construct a new characterization of inextensible flows by using elastica in space. The inextensible flow is completely determined for any space-like curve in de Sitter space $\mathbb{S}_{1}^{3}$. Finally, we give some characterizations for curvatures of a space-like curve in de Sitter space $\mathbb{S}_{1}^{3}$.

scholarly journals Weingarten spacelike hypersurfaces in a de Sitter space

2012 ◽  
Vol 20 (1) ◽  
pp. 387-406
Author(s):  
Junfeng Chen ◽  
Shichang Shu
Keyword(s):  
De Sitter Space ◽  
De Sitter ◽  
Principal Curvatures ◽  
Riemannian Product ◽  
Spacelike Hypersurfaces ◽  
Hyperbolic Cylinder

Abstract We study some Weingarten spacelike hypersurfaces in a de Sitter space S1n+1 (1). If the Weingarten spacelike hypersurfaces have two distinct principal curvatures, we obtain two classification theorems which give some characterization of the Riemannian product Hk(1−coth2 ϱ)× Sn−k(1 − tanh2 ϱ), 1 < k < n − 1 in S1n+1(1), the hyperbolic cylinder H1(1 − coth2 ϱ) × Sn-1(1 − tanh2 ϱ) or spherical cylinder Hn−1(1 − coth2 ϱ) × S1(1 − tanh2 ϱ) in S1n+1 (1)

scholarly journals Compact Spacelike Hypersurfaces with Constant Mean Curvature in the Antide Sitter Space

2009 ◽  
Vol 2009 ◽  
pp. 1-12
Author(s):  
Henrique F. de Lima ◽  
Joseilson R. de Lima
Keyword(s):  
Hyperbolic Space ◽  
Mean Curvature ◽  
Constant Mean Curvature ◽  
Spacelike Hypersurface ◽  
De Sitter Space ◽  
De Sitter ◽  
Height Estimate ◽  
Spacelike Hypersurfaces ◽  
Hyperbolic Domains

We obtain a height estimate concerning to a compact spacelike hypersurfaceΣnimmersed with constant mean curvatureHin the anti-de Sitter spaceℍ1n+1, when its boundary∂Σis contained into an umbilical spacelike hypersurface of this spacetime which is isometric to the hyperbolic spaceℍn. Our estimate depends only on the value ofHand on the geometry of∂Σ.As applications of our estimate, we obtain a characterization of hyperbolic domains ofℍ1n+1and nonexistence results in connection with such types of hypersurfaces.

scholarly journals The motion of a relativistic charged particle in a homogenous electromagnetic field in De-Sitter space

2018 ◽  
Vol 64 (2) ◽  
pp. 176 ◽  
Author(s):  
Ridvan Cem Demirkol ◽  
Talat Körpinar
Keyword(s):  
Electromagnetic Field ◽  
Charged Particle ◽  
De Sitter Space ◽  
Geometric Characterization ◽  
Antisymmetric Tensor ◽  
De Sitter ◽  
Relativistic Approach ◽  
Relativistic Charged Particle

We discuss the geometric characterization of the trajectoryof a moving charged particle, for the case of a homogeneous electromagnetic…eld, in De-Sitter space when the motion is governed by the Lorentz equa-tion. We employ totally relativistic approach during the discussion and itis based on a systematic use of the four-dimensional Frenet-Serret formulae,which is adapted to the De-Sitter space to determine the worldline geometryof the electromagnetic …eld acting on the particle in De-Sitter space, and ofthe Faraday antisymmetric tensor properties.

Characterization of intergranular cuprous oxide in polycrystalline YBa2Cu3O7-x

1988 ◽  
Vol 46 ◽  
pp. 880-881
Author(s):  
Bradley L. Thiel ◽  
Chan Han R. P. ◽  
Kurosky L. C. Hutter ◽  
I. A. Aksay ◽  
Mehmet Sarikaya
Keyword(s):  
Grain Boundary ◽  
Cuprous Oxide ◽  
Room Temperature ◽  
Boundary Phase ◽  
Spectroscopic Techniques ◽  
Transition Width ◽  
Practical Applications ◽  
Thin Foils ◽  
Superconducting Oxides

The identification of extraneous phases is important in understanding of high Tc superconducting oxides. The spectroscopic techniques commonly used in determining the origin of superconductivity (such as RAMAN, XPS, AES, and EXAFS) are surface-sensitive. Hence a grain boundary phase several nanometers thick could produce irrelevant spectroscopic results and cause erroneous conclusions. The intergranular phases present a major technological consideration for practical applications. In this communication we report the identification of a Cu2O grain boundary phase which forms during the sintering of YBa2Cu3O7-x (1:2:3 compound).Samples are prepared using a mixture of Y2O3. CuO, and BaO2 powders dispersed in ethanol for complete mixing. The pellets pressed at 20,000 psi are heated to 950°C at a rate of 5°C per min, held for 1 hr, and cooled at 1°C per min to room temperature. The samples show a Tc of 91K with a transition width of 2K. In order to prevent damage, a low temperature stage is used in milling to prepare thin foils which are then observed, using a liquid nitrogen holder, in a Philips 430T at 300 kV.

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