Yazar "Erdogan, Feyza Esra" seçeneğine göre listele

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    Bi-f-Harmonic Curves and Hypersurfaces
    (Univ Nis, Fac Sci Math, 2019) Perktas, Selcen Yuksel; Blaga, Adara M.; Erdogan, Feyza Esra; Acet, Bilal Eftal
    In the present paper, we study bi-f-harmonic maps which generalize not only f-harmonic maps, but also biharmonic maps. We derive bi-f -harmonic equations for curves in the Euclidean space, unit sphere, hyperbolic space, and for hypersurfaces of Riemannian manifolds.
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    f-Biharmonic and Bi-f-Harmonic Magnetic Curves in Three-Dimensional Normal Almost Paracontact Metric Manifolds
    (Int Electronic Journal Geometry, 2021) Bozdag, Serife Nur; Erdogan, Feyza Esra
    In this paper, we study f-harmonic, f-biharmonic, bi-f-harmonic and f-biminimal non-null magnetic curves in three-dimensional normal almost paracontact metric manifolds. We determine necessary and sufficient conditions for these properties of a non-null magnetic curve. Besides, we obtain absence theorems.
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    Golden Riemannian Manifolds Having Constant Sectional Curvatures and Their Submanifolds
    (Springer Basel Ag, 2022) Sahin, Fulya; Sahin, Bayram; Erdogan, Feyza Esra
    We study Golden Riemannian manifolds having constant sectional curvatures. First of all, we observed that if the Golden manifold has a constant (real) sectional curvature, then under certain conditions it is flat. Then, we examined holomorphic-like and holomorphic bisectional-like sectional curvatures. We have found that these both curvatures are zero on Golden Riemannian manifolds. Therefore, we have modified these notions by introducing the notion of Golden sectional curvature and we provide an example for this new notion. We then obtain the expression of curvature tensor field when the Golden sectional curvature is constant. Moreover, we applied this notion to submanifolds of Golden Riemannian manifolds and obtain existence theorems for semi-invariant submanifolds.
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    Half-Lightlike Submanifolds of Metallic semi-Riemannian Manifolds
    (Int Electronic Journal Geometry, 2022) Acet, Bilal Eftal; Erdogan, Feyza Esra; Perktas, Selcen Yuksel
    The aim of the present paper is to study half-lightlike submanifolds of a semi-Riemannian manifold endowed with a metallic structure. We introduce a special half-lightlike submanifold called screen semi-invariant half lightlike submanifold in metallic semi-Riemannian manifolds and give an example. We present necessary and sufficient conditions for the distributions included in the definition of such half lightlike submanifolds to be integrable. Moreover, we analyze geometry of a screen semi-invariant half lightlike submanifold in a locally metallic semi -Riemannian manifold when it is totally geodesic and screen conformal.
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    Isotropic Riemannian submersions
    (Scientific Technical Research Council Turkey-Tubitak, 2020) Erdogan, Feyza Esra; Sahin, Bayram
    In this paper, we present the notion of isotropic submersions between Riemannian manifolds. We first give examples to illustrate this new notion. Then we express a characterization in terms of O'Neill's tensor field T and examine certain relations between sectional curvatures of the total manifold and the base manifold. We also study lambda-isotropic submersions with pointwise planar horizontal sections.
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    Lightlike Hypersurfaces of Meta-Golden Semi-Riemannian Manifolds
    (Mdpi, 2023) Erdogan, Feyza Esra; Perktas, Selcen Yueksel; Bozdağ, Şerife Nur; Acet, Bilal Eftal
    In this research, we embark on the examination of lightlike hypersurfaces within an almost meta-Golden semi-Riemannian manifold. We investigate the properties of the induced structure on a lightlike hypersurface by meta-Golden semi-Riemannian structure. Then, we introduce invariant lightlike hypersurfaces, anti-invariant lightlike hypersurfaces and screen semi-invariant lightlike hypersurfaces of almost meta-Golden semi-Riemannian manifolds and give examples.
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    LIGHTLIKE HYPERSURFACES WITH PLANAR NORMAL SECTIONS IN R-1(4)
    (Ankara Univ, Fac Sci, 2020) Erdogan, Feyza Esra; Perktas, Selcen Yuksel
    In the present paper our aim is to investigate lightlike hypersurfaces of R-1(4) having degenerate or non-degenerate planar normal sections. Firstly, we prove that lightlike hypersurfaces in R-1(4) always have degenerate planar normal sections. Then we examine the conditions for lightlike hypersurfaces in R-1(4) to have non-degenerate planar normal sections and obtain some characterizations for such lightlike hypersurfaces.
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    Lightlike Submanifolds of Metallic Semi-Riemannian Manifolds
    (Univ Nis, Fac Sci Math, 2020) Perktas, Selcen Yuksel; Erdogan, Feyza Esra; Acet, Bilal Eftal
    Our aim in this paper is to investigate some special types of lightlike submanifolds in metallic semi-Riemannian manifolds. We study invariant lightlike submanifolds and screen semi-invariant lightlike hypersurfaces of metallic semi-Riemannian manifolds and give examples. We obtain some conditions for the induced connection to be a metric connection and present integrability conditions for the distributions involved in the definitions of such types.
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    On some curves in three-dimensional beta-Kenmotsu manifolds
    (Springer Heidelberg, 2022) Bozdag, Serife Nur; Perktas, Selcen Yuksel; Erdogan, Feyza Esra
    This paper is devoted to examine necessary and sufficient conditions for a Frenet curve to be f-harmonic, f-biharmonic, bi- f -harmonic and f-biminimal in three-dimensional beta-Kenmotsu manifolds. In addition, such conditions are investigated for slant curves.
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    On Some Types of Lightlike Submanifolds of Golden Semi-Riemannian Manifolds
    (Univ Nis, Fac Sci Math, 2019) Erdogan, Feyza Esra
    The main purpose of the present paper is to study the geometry of screen transversal lightlike submanifolds and radical screen transversal lightlike submanifolds and screen transversal anti-invariant lightlike submanifolds of Golden semi-Riemannian manifolds. We investigate the geometry of distributions and obtain necessary and sufficient conditions for the induced connection on these manifolds to be metric connection. We also obtain characterizations of screen transversal anti-invariant lightlike submanifolds of Golden semi-Riemannian manifolds. Finally, we give two examples.
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    Screen transversal lightlike submanifolds of metallic semi-Riemannian manifolds
    (Elsevier Science Bv, 2019) Erdogan, Feyza Esra; Perktas, Selcen Yuksel; Acet, Bilal Eftal; Blaga, Adara Monica
    In the present paper, we introduce screen transversal lightlike submanifolds of metallic semi-Riemannian manifolds with its subclasses, namely screen transversal anti-invariant, radical screen transversal and isotropic screen transversal lightlike submanifolds, and give an example. We show that there do not exist co-isotropic and totally screen transversal type of screen transversal anti-invariant lightlike submanifolds of a metallic semi-Riemannian manifold. We investigate the geometry of distributions involved in the definition of such submanifolds and the conditions for the induced connection to be a metric connection. Furthermore, we give a necessary and sufficient condition for an isotropic screen transversal lightlike submanifold to be totally geodesic. (C) 2019 Elsevier B.V. All rights reserved.
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    Some types of f-biharmonic and bi-f-harmonic curves
    (Hacettepe Univ, Fac Sci, 2022) Erdogan, Feyza Esra; Bozdag, Serife Nur
    In this paper, we determine necessary and sufficient conditions for a non-Frenet Legendre curve to be f-harmonic, f-biharmonic, bi-f-harmonic, biminimal and f-biminimal in three-dimensional normal almost paracontact metric manifold. Besides, we obtain some nonexistence theorems.
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    Transversal lightlike submanifolds of metallic semi-Riemannian manifolds
    (Scientific Technical Research Council Turkey-Tubitak, 2018) Erdogan, Feyza Esra
    The main purpose of the present paper is to study the geometry of transversal lightlike submanifolds and radical transversal lightlike submanifolds of metallic semi-Riemannian manifolds. We investigate the geometry of distributions and obtain necessary and sufficient conditions for the induced connection on these manifolds to be a metric connection. We also obtain characterization of transversal lightlike submanifolds of metallic semi-Riemannian manifolds. Finally, we give two examples.