Person:
DELİCE, ÖZGÜR

Profile Picture

Email Address

Birth Date

Research Projects

Organizational Units

OrgUnit Logo
Organizational Unit

Job Title

Last Name

DELİCE

First Name

ÖZGÜR

Name

Filters

2011 - 20184
Reset filters

Settings

Subject: GENERAL-RELATIVITY ×

Search Results

Now showing 1 - 4 of 4
  • Thumbnail Image
    PublicationOpen Access
    Linearized modified gravity theories with a cosmological term: advance of perihelion and deflection of light
    (IOP PUBLISHING LTD, 2018-03-22) DELİCE, ÖZGÜR; Ozer, Hatice; Delice, Ozgur
    Two different ways of generalizing Einstein's general theory of relativity with a cosmological constant to Brans-Dicke type scalar-tensor theories are investigated in the linearized field approximation. In the first case a cosmological constant term is coupled to a scalar field linearly whereas in the second case an arbitrary potential plays the role of a variable cosmological term. We see that the former configuration leads to a massless scalar field whereas the latter leads to a massive scalar field. General solutions of these linearized field equations for both cases are obtained corresponding to a static point mass. Geodesics of these solutions are also presented and solar system effects such as the advance of the perihelion, deflection of light rays and gravitational redshift were discussed. In general relativity a cosmological constant has no role in these phenomena. We see that for the Brans-Dicke theory, the cosmological constant also has no effect on these phenomena. This is because solar system observations require very large values of the Brans-Dicke parameter and the correction terms to these phenomena becomes identical to GR for these large values of this parameter. This result is also observed for the theory with arbitrary potential if the mass of the scalar field is very light. For a very heavy scalar field, however, there is no such limit on the value of this parameter and there are ranges of this parameter where these contributions may become relevant in these scales. Galactic and intergalactic dynamics is also discussed for these theories at the latter part of the paper with similar conclusions.
  • Thumbnail Image
    PublicationOpen Access
    Higher dimensional cylindrical or Kasner type electrovacuum solutions
    (SPRINGER/PLENUM PUBLISHERS, 2013-11) DELİCE, ÖZGÜR; Delice, Ozgur; Kirezli, Pinar; Ciftci, Dilek K.
    We consider a dimensional Kasner type diagonal spacetime where metric functions depend only on a single coordinate and electromagnetic field shares the symmetries of spacetime. These solutions can describe static cylindrical or cosmological Einstein-Maxwell vacuum spacetimes. We mainly focus on electrovacuum solutions and four different types of solutions are obtained in which one of them has no four dimensional counterpart. We also consider the properties of the general solution corresponding to the exterior field of a charged line mass and discuss its several properties. Although it resembles the same form with four dimensional one, there is a difference on the range of the solutions for fixed signs of the parameters. General magnetic field vacuum solution are also briefly discussed, which reduces to Bonnor-Melvin magnetic universe for a special choice of the parameters. The Kasner forms of the general solution are also presented for the cylindrical or cosmological cases.
  • Thumbnail Image
    PublicationOpen Access
    Brans-Dicke-Maxwell solutions for higher dimensional static cylindrical symmetric spacetime
    (AMER INST PHYSICS, 2015-07) DELİCE, ÖZGÜR; Ciftci, Dilek K.; Delice, Ozgur
    In this paper, Brans-Dicke-Maxwell type vacuum solutions are considered for a static cylindrically symmetric spacetime in arbitrary dimensions. Exact solutions are obtained by directly solving the field equations for the case where an azimuthal magnetic field is present. Other configurations such as axial magnetic field case can be obtained by suitably relabeling the coordinates. We have also considered conformally related Einstein frame to relate the solutions we have obtained with the dilaton-Maxwell type solutions that exist in the literature. We see that for a special case the general solution we present reduces to dilaton-Melvin spacetime. The general relativistic limit of these solutions is also discussed and we found that this limit is different from the four dimensional case. (C) 2015 AIP Publishing LLC.
  • Thumbnail Image
    PublicationOpen Access
    A unified approach to variational derivatives of modified gravitational actions
    (IOP PUBLISHING LTD, 2011-01-07) DELİCE, ÖZGÜR; Baykal, Ahmet; Delice, OZgur
    Our main aim in this paper is to promote the coframe variational method as a unified approach to derive field equations for any given gravitational action containing the algebraic functions of the scalars constructed from the Riemann curvature tensor and its contractions. We are able to derive a master equation which expresses the variational derivatives of the generalized gravitational actions in terms of the variational derivatives of its constituent curvature scalars. Using the Lagrange multiplier method relative to an orthonormal coframe, we investigate the variational procedures for modified gravitational Lagrangian densities in spacetime dimensions n >= 3. We study the well-known gravitational actions such as those involving the Gauss-Bonnet and Ricci-squared, Kretchmann scalar, Weyl-squared terms and their algebraic generalizations similar to generic f(R) theories and the algebraic generalization of sixth order gravitational Lagrangians. We put forth a new model involving the gravitational Chern-Simons term and also give three-dimensional new massive gravity equations in a new form in terms of the Cotton 2-form.