Browsing by Author "Yilmaz, Nejat Tevfik"

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Cosmological solution moduli of bigravity
(IOP PUBLISHING LTD, 2015) Nejat Tevfik Yilmaz; Yilmaz, Nejat Tevfik
We construct the complete set of metric-configuration solutions of the ghost-free massive bigravity for the scenario in which the g-metric is the Friedmann-Lemaitre-Robertson-Walker (FLRW) one and the interaction Lagrangian between the two metrics contributes an effective ideal fluid energy-momentum tensor to the g-metric equations. This set corresponds to the exact background cosmological solution space of the theory.
Decoupling solution moduli of bigravity
(Elsevier B.V., 2016) Nejat Tevfik Yilmaz; Yilmaz, Nejat Tevfik
A complete classification of exact solutions of ghost-free massive bigravity is derived which enables the dynamical decoupling of the background and the foreground metrics. The general decoupling solution space of the two metrics is constructed. Within this branch of the solution space the foreground metric theory becomes general relativity (GR) with an additional effective cosmological constant and the background metric dynamics is governed by plain GR. © 2016 Elsevier B.V. All rights reserved.
Citation - WoS: 1
Effective fluid FLRW cosmologies of minimal massive gravity
(World Scientific, 2015) Nejat Tevfik Yilmaz; Yilmaz, Nejat Tevfik
By using a solution ansatz we partially decouple the metric and the Stückelberg sectors of the minimal massive gravity (MMGR). In this scheme for a diagonal physical metric we find the general solutions for the scalars of the theory and the particular fiducial (background) metric which leads to these solutions. Then we adopt this general formalism to construct the derivation of new Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmologies of the theory in the presence of a so-called effective ideal fluid which arises from our solution ansatz as a modifying non-physical source for the Einstein and the corresponding Friedmann equations. © 2021 Elsevier B.V. All rights reserved.
Citation - WoS: 6
Effective matter cosmologies of massive gravity I: non-physical fluids
(IOP PUBLISHING LTD, 2014) Nejat Tevfik Yilmaz; Yilmaz, Nejat Tevfik
For the massive gravity after decoupling from the metric equation we find a broad class of solutions of the Stuckelberg sector by solving the background metric in the presence of a diagonal physical metric. We then construct the dynamics of the corresponding FLRW cosmologies which inherit effective matter contribution through the decoupling solution mechanism of the scalar sector.
Citation - WoS: 2
Citation - Scopus: 2
Effective matter cosmologies of massive gravity: Physical fluids
(American Physical Society revtex@aps.org, 2014) Nejat Tevfik Yilmaz; Yilmaz, Nejat Tevfik
We derive new cosmological solutions of the ghost-free massive gravity with a general background metric in which the contribution of the mass sector to the metric one is modeled by an effective cosmological constant and an ideal fluid which obeys the first law of thermodynamics, thus it satisfies the ordinary energy-momentum conservation or continuity equation. © 2020 Elsevier B.V. All rights reserved.