Yazar "Yildiz, Ahmet" seçeneğine göre listele

Listeleniyor 1 - 18 / 18
  • Küçük Resim Yok
    Öğe
    A Case of Hydatid Cyst Mimicking Kidney Tumor
    (Aves, 2019) Camtosun, Ahmet; Celik, Huseyin; Yildiz, Ahmet; Altintas, Ramazan; Tasdemir, Cemal
    A 45-year-old male patient presented with left flank pain that started a month ago. There was no history of fever or pyuria. Vital signs were normal. The rest of the systemic examination was unremarkable. There were no pathological findings on urinalysis or urine cytology. Ultrasonography revealed an 8x6.2x6 cm heterogeneous exophytic trending lesion at the lower pole of the left kidney. The lesion's walls were seen to be calcified in places, and the margin between the kidney and lesion was indistinct. It could not be differentiated by ultrasonography if the lesion is a complicated cyst or a mass. Magnetic resonance imaging scan of the upper abdomen also revealed a 9x7.5x7 cm cortical-parapelvic localized lesion at the lower pole of the left kidney, extending exophytically to the inferior. Given the possibility that the lesion is malignant, nephrectomy was planned. A laparoscopic approach was performed. Histopathological diagnosis was hydatid cyst. Enzyme-linked immunosorbent assay test for hydatid disease was negative. Albendazole 10 mg/kg twice a day was administered postoperatively for 3 weeks.
  • Küçük Resim Yok
    Öğe
    Certain curvature conditions on generalized sasakian space-forms
    (Natl Inquiry Services Centre Pty Ltd, 2015) De, Uday Chand; Yildiz, Ahmet
    The object of the present paper is to study certain curvature conditions on generalized Sasakian space-forms. We classify generalized Sasakian space-forms which satisfy P P=0, P Z=0, Z P=0, Z Z=0, where P is the projective curvature tensor and Z is the concircular curvature tensor.
  • Küçük Resim Yok
    Öğe
    Certain results on a type of contact metric manifold
    (Springer Heidelberg, 2015) De, Uday Chand; Yildiz, Ahmet; Cetinkaya, Azime
    Let M be a 3-dimensional almost contact metric manifold satisfying (*) condition. We denote such a manifold by M*. At first we study symmetric and skew-synunetric parallel tensor of type (0, 2) in M*. Next we prove that a non-cosymplectic manifold M* is Ricci semisymmetric if and only if it is Einstein. Also we study locally phi-symmetry and eta-parallel Ricci tensor of M*. Finally, we prove that if a non-cosymplectic M* is Einstein, then the manifold is Sasakian.
  • Küçük Resim Yok
    Öğe
    Chaki type pseudo-symmetric lightlike hypersurfaces
    (World Scientific Publ Co Pte Ltd, 2015) Sahin, Bayram; Yildiz, Ahmet
    In this paper, we investigate lightlike hypersurfaces which are Chaki type pseudosymmetric, Chaki type pseudo-Ricci symmetric and Chaki type pseudo-projective symmetric in a semi-Euclidean space. We also give some physical interpretations of Chaki type pseudo-symmetry condition.
  • Küçük Resim Yok
    Öğe
    Characterizations of mixed quasi-Einstein manifolds
    (World Scientific Publ Co Pte Ltd, 2017) Mallick, Sahanous; Yildiz, Ahmet; De, Uday Chand
    The object of the present paper is to study mixed quasi-Einstein manifolds. Some geometric properties of mixed quasi-Einstein manifolds have been studied. We also discuss M(QE)(4) spacetime with space-matter tensor and some properties related to it. Finally, we construct an example of a mixed quasi-Einstein spacetime.
  • Küçük Resim Yok
    Öğe
    f-KENMOTSU MANIFOLDS WITH THE SCHOUTEN-VAN KAMPEN CONNECTION
    (Publications L Institut Mathematique Matematicki, 2017) Yildiz, Ahmet
    We study 3-dimensional f-Kenmotsu manifolds with the Schoutenvan Kampen connection. With the help of such a connection, we study projectively flat, conharmonically flat, Ricci semisymmetric and semisymmetric 3-dimensional f-Kenmotsu manifolds. Finally, we give an example of 3dimensional f-Kenmotsu manifolds with the Schouten-van Kampen connection.
  • Küçük Resim Yok
    Öğe
    Generalized Quasi-Einstein Metrics and Contact Geometry
    (Kyungpook Natl Univ, Dept Mathematics, 2022) Biswas, Gour Gopal; De, Uday Chand; Yildiz, Ahmet
    The aim of this paper is to characterize K-contact and Sasakian manifolds whose metrics are generalized quasi-Einstein metric. It is proven that if the metric of a K-contact manifold is generalized quasi-Einstein metric, then the manifold is of constant scalar curvature and in the case of a Sasakian manifold the metric becomes Einstein under certain restriction on the potential function. Several corollaries have been provided. Finally, we consider Sasakian 3-manifold whose metric is generalized quasi-Einstein metric.
  • Küçük Resim Yok
    Öğe
    A note on almost quasi Yamabe solitons and gradient almost quasi Yamabe solitons
    (Hacettepe Univ, Fac Sci, 2021) Ghosh, Sujit; De, Uday Chand; Yildiz, Ahmet
    In this article, we characterize almost quasi-Yamabe solitons and gradient almost quasiYamabe solitons in context of three dimensional Kenmotsu manifolds. It is proven that if the metric of a three dimensional Kenmotsu manifold admits an almost quasi-Yamabe soliton with soliton vector field W then the manifold is of constant sectional curvature -1, but the converse is not true has been shown by a concrete example, under the restriction phi W not equal 0. Next we consider gradient almost quasi-Yamabe solitons in a three dimensional Kenmotsu manifold.
  • Küçük Resim Yok
    Öğe
    ON A CLASS OF N(k)-CONTACT METRIC MANIFOLDS
    (Editura Acad Romane, 2014) De, Uday Chand; Yildiz, Ahmet; Ghosh, Sujit
    The object of the present paper is to study xi-concircularly flat and phi-concircularly flat N(k)-contact metric manifolds. Beside these, we also study N(k)-contact metric manifolds satisfying Z(xi, X).S = 0. Finally, we construct an example to verify some results.
  • Küçük Resim Yok
    Öğe
    ON A TYPE OF LORENTZIAN PARA-SASAKIAN MANIFOLDS
    (Editura Acad Romane, 2014) Yildiz, Ahmet; De, Uday Chand; Ata, Erhan
    The object of the present paper is to introduce a new concept called generalized eta-Einstein manifold in a Lorentzian Para-Sasakian manifold. Some geometric properties have been studied. Finally an example has been constructed to prove the existance of a generalized eta-Einstein Lorentzian Para-Sasakian manifold.
  • Küçük Resim Yok
    Öğe
    On Quasi-Sasakian 3-Manifolds with Respect to the Schouten-van Kampen Connection
    (Int Electronic Journal Geometry, 2020) Perktas, Selcen Yuksel; Yildiz, Ahmet
    In this paper we study some soliton types on a quasi-Sasakian 3-manifold with respect to the Schouten-van Kampen connection.
  • Küçük Resim Yok
    Öğe
    On some classes of 3-dimensional generalized (?, ?)-contact metric manifolds
    (Tubitak Scientific & Technological Research Council Turkey, 2015) Yildiz, Ahmet; De, Uday Chand; Cetinkaya, Azime
    The object of the present paper is to obtain a necessary and sufficient condition for a 3-dimensional generalized (kappa, mu)-contact metric manifold to be locally phi-symmetric in the sense of Takahashi and the condition is verified by an example. Next we characterize a 3-dimensional generalized (kappa, mu)-contact metric manifold satisfying certain curvature conditions on the concircular curvature tensor. Finally, we construct an example of a generalized (kappa, mu)-contact metric manifold to verify Theorem 1 of our paper.
  • Küçük Resim Yok
    Öğe
    ON TRANS-SASAKIAN 3-MANIFOLDS WITH symbolscript DEFORMATION WITH REGARD TO THE SCHOUTEN-VAN KAMPEN CONNECTION
    (Publications L Institut Mathematique Matematicki, 2022) Zeren, Semra; Yildiz, Ahmet; Perktas, Selcen Yuksel
    We study some soliton types on trans-Sasakian 3-manifolds with Da-homotetic deformation with regard to the Schouten-van Kampen connec-tion.
  • Küçük Resim Yok
    Öğe
    Riemannian manifolds admitting a new type of semisymmetric nonmetric connection
    (Tubitak Scientific & Technological Research Council Turkey, 2019) Chaubey, Sudhakar K.; Yildiz, Ahmet
    We define a new type of semisymmetric nonmetric connection on a Riemannian manifold and establish its existence. It is proved that such connection on a Riemannian manifold is projectively invariant under certain conditions. We also find many basic results of the Riemannian manifolds and study the properties of group manifolds and submanifolds of the Riemannian manifolds with respect to the semisymmetric nonmetric connection. To validate our findings, we construct a nontrivial example of a 3-dimensional Riemannian manifold equipped with a semisymmetric nonmetric connection.
  • Küçük Resim Yok
    Öğe
    Sequential warped product manifolds with a semi-symmetric metric connection
    (Univ Nis, Fac Sci Math, 2023) Zeren, Semra; Perkta, Selcen Yuksel; Yildiz, Ahmet
    In the present paper, we study a new generalization of warped product manifolds, called sequential warped product manifolds, with respect to a semi-symmetric metric connection. We obtain relations for covariant derivatives, Riemannian curvature, Ricci curvature and scalar curvature of the sequential warped product manifolds with respect to the semi-symmetric connection, respectively, and demonstrate the relationship between them and curvatures with respect to the Levi-Civita connection. Also, we consider sequential warped product space-time models, namely sequential generalized Robertson -Walker space-times and sequential standard static space-times, with semi-symmetric metric connections and obtain conditions for such space-times to be Einstein.
  • Küçük Resim Yok
    Öğe
    SOME CURVATURE PROPERTIES ON PARACONTACT METRIC (k, ?)-MANIFOLDS WITH RESPECT TO THE SCHOUTEN-VAN KAMPEN CONNECTION
    (Univ Nis, 2021) Yildiz, Ahmet; Perktas, Selcen Yuksel
    The object of the present paper is to characterize paracontact metric (k, mu)-manifolds satisfying certain semisymmetry curvature conditions with respect to the Schouten-van Kampen connection.
  • Küçük Resim Yok
    Öğe
    Some results on paracontact metric (k, ?)-manifolds with respect to the Schouten-van Kampen connection
    (Hacettepe Univ, Fac Sci, 2022) Perktas, Selcen Yuksel; De, Uday Chand; Yildiz, Ahmet
    In the present paper we study certain symmetry conditions and some types of solitons on paracontact metric (k, mu)-manifolds with respect to the Schouten-van Kampen connection. We prove that a Ricci semisymmetric paracontact metric (k, mu)-manifold with respect to the Schouten-van Kampen connection is an g-Einstein manifold. We investigate paracontact metric (k, mu)-manifolds satisfying (sic) . (sic)(cur) = 0 with respect to the Schouten-van Kampen connection. Also, we show that there does not exist an almost Ricci soliton in a (2n + 1)-dimensional paracontact metric (k, mu)-manifold with respect to the Schouten-van Kampen connection such that k > -1 or k < -1. In case of the metric is being an almost gradient Ricci soliton with respect to the Schouten-van Kampen connection, then we state that the manifold is either N(k)-paracontact metric manifold or an Einstein manifold. Finally, we present some results related to almost Yamabe solitons in a paracontact metric (k, mu)-manifold equipped with the Schouten-van Kampen connection and construct an example which verifies some of our results.
  • Küçük Resim Yok
    Öğe
    SOME SEMISYMMETRY CONDITIONS ON RIEMANNIAN MANIFOLDS
    (Univ Nis, 2014) Yildiz, Ahmet; Cetinkaya, Azime
    We study a Riemannian manifold M admitting a semisymmetric metric connection (del) over tilde such that the vector field U is a parallel unit vector field with respect to the Levi-Civita connection del. Firstly, we show that ifMis projectively flat with respect to the semisymmetric metric connection (del) over tilde then M is a quasi-Einstein manifold. Also we prove that if R.(P) over tilde = 0 if and only ifMis projectively semisymmetric; if (P) over tilde .R = 0 or R.(P) over tilde-(P) over tilde .R = 0 then Mis conformally flat and quasi-Einstein manifold. Here R, P and (P) over tilde denote Riemannian curvature tensor, the projective curvature tensor of del and the projective curvature tensor of (del) over tilde, respectively.