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Oktay Cebecioğlu

Publications and source records attributed to Oktay Cebecioğlu.

8 recordsLinked to original sources

Torsion-Induced Modification to Friedmann Equations in $AdSL_{4}$ Gauged Gravity

We study the solution of the gravitational field equations in $AdSL_{4}$-gauged gravity, a gauge-theoretic extension of general relativity based on the $AdSL_{4}$ algebra. In this formulation, the antisymmetric gauge field $B^{ab}$, associated with additional $AdSL_{4}$ tensorial generators, induces space-time torsion via the relation $K^{ab}=μB^{ab}$, where $K^{ab}$ denotes the contorsion 1-form. The presence of torsion modifies both the spin connection and curvature, leading to an extended set of Einstein-Cartan field equations. Focusing on spatially homogeneous and isotropic cosmological backgrounds, we derive the modified Friedmann equations which explicitly incorporate the torsional contribution. The resulting acceleration equation admits de Sitter-like solutions in which cosmic acceleration originates purely from the gauge-theoretic structure of enlarged four-dimensional space-time symmetries. Within this formulation, the dynamical components of the gauge field $B^{ab}$ emerge naturally as a source of the effective cosmological constants, without the introduction of exotic matter sources. Furthermore, our analysis shows that the torsion-driven cosmological phase in $AdSL_{4}$-gauged gravity can reproduce an effective equation-of-state parameter $ω_{B}=-1/3$, establishing a connection between space-time torsion and cosmic-string-like dynamics.

hep-th↗

Gauging the Maxwell extended $\mathcal{GL}\left(n,\mathbb{R}\right)$ and $\mathcal{SL}\left(n+1,\mathbb{R}\right)$ algebras

We consider the extension of the general-linear and special-linear algebras by employing the Maxwell symmetry in $D$ space-time dimensions. We show how various Maxwell extensions of the ordinary space-time algebras can be obtained by a suitable contraction of generalized algebras. The extended Lie algebras could be useful in the construction of generalized gravity theories and the objects that couple to them. We also consider the gravitational dynamics of these algebras in the framework of the gauge theories of gravity. By adopting the symmetry-breaking mechanism of the Stelle-West model, we present some modified gravity models that contain the generalized cosmological constant term in four dimensions.

hep-th↗

Maxwell extension of $f(R)$ gravity

Inspired by the Maxwell symmetry generalization of general relativity (Maxwell gravity), we have constructed the Maxwell extension of $f(R)$ gravity. We found that the semi-simple extension of the Poincare symmetry allows us to introduce geometrically a cosmological constant term in four-dimensional $f(R)$ gravity. This symmetry also allows the introduction of a non-vanishing torsion to the Maxwell $f(R)$ theory. It is found that the antisymmetric gauge field $B^{ab}$ associated with Maxwell extension is considered as a source of the torsion. It is also found that the gravitational equation of motion acquires a new term in the form of an energy-momentum tensor for the background field. The importance of these new equations is briefly discussed.

hep-th↗

Maxwell-Modified Metric Affine Gravity

We present a gauge formulation of the special affine algebra extended to include an antisymmetric tensorial generator belonging to the tensor representation of the special linear group. We then obtain a Maxwell modified metric affine gravity action with a cosmological constant term. We find the field equations of the theory and show that the theory reduces to an Einstein-like equation for metric affine gravity with the source added to the gravity equations with cosmological constant μcontains linear contributions from the new gauge fields. The reduction of the Maxwell metric affine gravity to Riemann-Cartan one is discussed and the shear curvature tensor corresponding to the symmetric part of the special linear connection is identified with the dark energy. Furthermore, the new gauge fields interpreted as geometrical inflaton vector fields which drive accelerated expansion.

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Gauge theory of the Maxwell and semi-simple extended (anti) de Sitter algebra

In this paper, a semi-simple and Maxwell extension of the (anti) de Sitter algebra is constructed. Then, a gauge-invariant model has been presented by gauging the Maxwell semi-simple extension of the (anti) de Sitter algebra. We firstly construct a Stelle-West like model action for five-dimensional space-time in which the effects of spontaneous symmetry breaking have been taken into account. In doing so, we get an extended version of Einstein's field equations. Next, we decompose the five-dimensional extended Lie algebra and establish a MacDowell-Mansouri like action that contains the Einstein-Hilbert term, the cosmological term as well as new terms coming from Maxwell extension in four-dimensional space-time where the torsion-free condition is assumed. Finally, we have shown that both models are equivalent for an appropriately chosen gauge condition.

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Generalized cosmological constant from gauging Maxwell-conformal algebra

The Maxwell extension of the conformal algebra is presented. With the help of gauging the Maxwell-conformal group, a conformally invariant theory of gravity is constructed. In contrast to the conventional conformally invariant actions, our gravitational action contains the Einstein-Hilbert term without introducing any additional (compensator) scalar field to satisfy the local scale invariance. This is achieved by using the curvatures of the algebra. In a special condition, we show that the resulting action is reduced to the Brans-Dicke like theory of gravity. We subsequently find the generalized Einstein field equation together with a coordinate dependent cosmological term and additional contributions.

hep-th↗

$D=4$ supergravity from the Maxwell-Weyl superalgebra

Abstract We present the construction of the first-order $D=4$, $\mathcal{N}=1$ supergravity action by gauging the Maxwell-Weyl superalgebra. The four-form lagrangian is constructed by using the curvatures of the algebra and the local scale invariance of the action is achieved through the introduction of a compensating scalar field. Finally, we find the generalized Einstein equation with a coordinate dependent cosmological term.

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$D=4$ topological gravity from gauging the Maxwell-special-affine group

In this paper, the Maxwell extension of the special-affine algebra is obtained and corresponding non-linear realization is constructed. We give also the differential realization of the generators of the extended symmetry. Moreover, we present the gauge theory of the Maxwell special-affine algebra and the topological gravity action in four dimensions. As a conclusion, we show that the Bianchi identities can be found by using the solution of the equations of motion.

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