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1.
李华宗 《数学学报》1937,2(2):225-233
<正> It is well-known that the camplex linear unimodular group G_2 ofa 2-dimensional affine space E_2 is a representation of the real orthogonalgToup G_4 of a 4-dimensional euclidean space R.In this paper it isshown that the same group G,is also a representation of the complexorthogonal group G_3 of a 3-dimensional euclidean space R_3,and that anisomorphism between G_4 and G_3 can be established.  相似文献   

2.
In this article, we give the area formula of the closed projection curve of a closed space curve in Lorentzian 3-space L3. For the 1-parameter closed Lorentzian space motion in L3, we obtain a Holditch Theorem taking into account the Lorentzian matrix multiplication for the closed space curves by using their othogonal projections onto the Euclidean plane in the fixed Lorentzian space. Moreover, we generalize this Holditch Theorem for noncollinear three fixed points of the moving Lorentzian space and any other fixed point on the plane which is determined by these three fixed points.  相似文献   

3.
苏步青 《数学学报》1937,2(2):277-289
<正> In a recent paper of the same title we studied the plane sectionsof the circumscribed developable of a curve in the projective n-dimen-sional space Sn(n(?)3) confining ourselves to the consideration of theplanes contained in the osculating space S_3(P) at an ordinary point Pof the curve.In particular, the plane section x_3 made by a planethrough the tangent of the curve at P has an inflexion at P and conse-quently admits an invariant point O_6,namely,the cusp of the cubic whichhas with x_3 a contact of order 6 at P.We have established among otherthings that when the plane π turns about the tangent the correspondingpoint O_6 describes a twisted cubic Г_3 in the osculating space S_3(P) ofthe curve at P.  相似文献   

4.
The purpose of this paper is to characterize the ellipsoids in the unimodularaffine space of dimension 3 by the affine principal curvatures and the spheres inthe space of constant curvature of dimension 3 by the principal curvatures. Let A~3 be the unimodular affine space of dimension 3,x:M→A~3 be a closed,locally strongly convex C~5 surface.Denote the equiaffine principal curvatures of Mby λ_1,λ_2 and let  相似文献   

5.
In this paper, a class of biholomorphic mappings named quasi-convex mapping of order a in the unit ball of a complex Banach space is introduced. When the Banach space is confined to Cn, we obtain the relation between this class of mappings and the convex mappings. Furthermore, the growth and covering theorems of this class of mappings are given on the unit ball of a complex Banach space X. Finally, we get the second order terms coefficient estimations of the homogeneous expansion of quasi-convex mapping of order a defined on the polydisc in Cn and on the unit ball in a complex Banach space, respectively.  相似文献   

6.
The present paper is devoted to determining the metric g for an n-dimension-al (n≥4) Riemannian manifold (M, g) of quasi-constant curvature [1]. By the way, we have identified the space of quasi-constant curvature with the κ-special conformally flat space of K.Yano & B.Y.Chen [8]. Based upon the results so obtained, we have completely determined the canonical metric for such a space to admit the relevant field X as geodesic field, and the geometric structure for (M, g) to be a recurrent space of quasi-constant curvature. Also we have examined the validity of our results just obtained for a 3-dimensional conformally flat space of quasi-constant cvrvature. Besides, we have deduced some global properties of a complete manifold of quasi-constant curvature, which may be useful in applications.  相似文献   

7.
The present paper is devoted to determining the metric g for an n-dimensional (n≥4) Riemannian manifold (M, g) of quasi-constant curvature [1]. By the way, we have identified the space of quasi-constant curvature with the k-special conformally flat space of K. Yano & B. Y. Chen [8]. Based upon the results so obtained, we have completely determined the canonical metric for such a space to admit the relevant field X as geodesic field, and the geometric structure for (M, g) to be a recurrent space of quasi-constant curvature. Also we have examined the validity of our results just obtained for a 3-dimensional conformally flat space of quasi-constant cvrvature. Besides, we have deduced some global properties for a complete manifold of quasi-constant curvature, which may be useful in applications.  相似文献   

8.
Let X be a non-elementary Riemann surface of type(g,n),where g is the number of genus and n is the number of punctures with 3g-3+n1.Let T(X)be the Teichmller space of X.By constructing a certain subset E of T(X),we show that the convex hull of E with respect to the Teichmller metric,the Carathodory metric and the Weil-Petersson metric is not in any thick part of the Teichmler space,respectively.This implies that convex hulls of thick part of Teichmller space with respect to these metrics are not always in thick part of Teichmller space,as well as the facts that thick part of Teichmller space is not always convex with respect to these metrics.  相似文献   

9.
A locally convex space is said to be a Gateaux differentiability space (GDS) provided every continuous convex function defined on a nonempty convex open subset D of the space is densely Gateaux differentiable in .D.This paper shows that the product of a GDS and a family of separable Prechet spaces is a GDS,and that the product of a GDS and an arbitrary locally convex space endowed with the weak topology is a GDS.  相似文献   

10.
The eventually distance minimizing ray(EDM ray) in moduli spaces of the Riemann surfaces of analytic finite type with 3 g + n-3 0 is studied, which was introduced by Farb and Masur [5]. The asymptotic distance of EDM rays in a moduli space and the distance of end points of EDM rays in the boundary of the moduli space in the augmented moduli space are discussed in this article. A relation between the asymptotic distance of EDM rays and the distance of their end points is established. It is proved also that the distance of end points of two EDM rays is equal to that of end points of two Strebel rays in the Teichmu¨ller space of a covering Riemann surface which are leftings of some representatives of the EDM rays. Meanwhile, simpler proofs for some known results are given.  相似文献   

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