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Nejat Tevfik Yilmaz

Publications and source records attributed to Nejat Tevfik Yilmaz.

At least 19 recordsLinked to original sources
arXiv2016

Decoupling Solution Moduli of Bigravity

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.

hep-th↗
arXiv2015

Cosmological Solution Moduli of Bigravity

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.

hep-th↗
arXiv2015

Effective Fluid FLRW Cosmologies of Minimal Massive Gravity

By using a solution ansatz we partially decouple the metric and the Stuckelberg 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.

hep-th↗
arXiv2014

Effective Matter Cosmologies of Massive Gravity: Physical Fluids

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.

hep-th↗
arXiv2014

Effective Matter Cosmologies of Massive Gravity I: Non-Physical Fluids

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.

hep-th↗
arXiv2014

Constant Curvature Solutions of Minimal Massive Gravity

We study the constant curvature solutions of the minimal massive gravity (MMGR). After introducing a condition on the physical and the fiducial metrics as well as the Stuckelberg scalars which truncates the action to the Einstein-Hilbert one in the presence of an effective cosmological constant we focus on the solutions of the constraint equations written for the constant curvature physical metrics. We discuss two distinct formal solution methods for these constraint equations then present an explicit class of solutions for the Stuckelberg scalars and the fiducial metrics giving rise to constant curvature solutions of MMGR.

gr-qc↗
arXiv2014

Supergravity Induced Interactions on Thick Branes

The gravity coupling of the symmetric space sigma model is studied in the solvable Lie algebra parametrization. The corresponding Einstein's equations are derived and the energy-momentum tensor is calculated. The results are used to derive the dynamical equations of the warped 5D geometry for localized bulk scalar interactions in the framework of thick brane world models. The Einstein and scalar field equations are derived for flat brane geometry in the context of minimal and non-minimal gravity-bulk scalar couplings.

gr-qc↗
arXiv2010

Integrated Lax Formalism for PCM

By solving the first-order algebraic field equations which arise in the dual formulation of the D=2 principal chiral model (PCM) we construct an integrated Lax formalism built explicitly on the dual fields of the model rather than the currents. The Lagrangian of the dual scalar field theory is also constructed. Furthermore we present the first-order PDE system for an exponential parametrization of the solutions and discuss the Frobenious integrability of this system.

math-ph↗
arXiv2010

Braneworld Gravity in Symmetric Space Bulk

By considering the p-brane motion in G/K symmetric space bulk we identify the G-invariant bulk metric in the solvable lie algebra gauge of the brane action. After calculating the Levi-Civita connection of this bulk metric we use it in the Gauss equation to compute the braneworld curvature in terms of the bulk coordinates. Finally, by making use of the Gauss equation in the braneworld Einstein equation we present a geometrical method of implementing the first fundamental form in the gravitating brane dynamics for the specially chosen symmetric space bulk case leading to an Einstein equation solely expressed in terms of the bulk coordinates of the braneworld.

gr-qc↗
arXiv2009

Algebraic Integration of Sigma Model Field Equations

We prove that the dualization algebra of the symmetric space coset sigma model is a Lie algebra and we show that it generates an appropriate adjoint representation which enables the local integration of the field equations yielding the first-order ones.

math-ph↗
arXiv2008

Decoupling structure of the principal sigma model-Maxwell interactions

The principal sigma model and Abelian gauge fields coupling is studied. By expressing the first-order formulation of the gauge field equations an implicit on-shell scalar-gauge field decoupling structure is revealed. It is also shown that due to this decoupling structure the scalars of the theory belong to the pure sigma model and the gauge fields sector consists of a number of coupled Maxwell theories with currents partially induced by the scalars.

hep-th↗
arXiv2008

Dualisation of the principal sigma model

The first-order formulation of the principal sigma model with a Lie group target space is performed. By using the dualisation of the algebra and the field content of the theory the field equations which are solely written in terms of the field strengths are realized through an extended symmetry algebra parametrization. The structure of this symmetry algebra is derived so that it generates the realization of the field equations in a Bianchi identity of the current derived from the extended parametrization.

math-ph↗
arXiv2007

On the Symmetric Space Sigma-Model Kinematics

The solvable Lie algebra parametrization of the symmetric spaces is discussed. Based on the solvable Lie algebra gauge two equivalent formulations of the symmetric space sigma model are studied. Their correspondence is established by inspecting the normalization conditions and deriving the field transformation laws.

hep-th↗
arXiv2007

An Implicit Decoupling for the Dilatons and the Axions of the Heterotic String

A set of consistency conditions is derived for the massless sector of the D-dimensional E(8)xE(8) heterotic string. Under the solvable Lie algebra gauge these conditions are further formulated explicitly in terms of the dilatons and the axions. It is then shown that these consistency conditions which are satisfied by the solution space give way to an implicit decoupling between the coset scalar sector namely the dilatons and the axions and the gauge fields of the theory.

hep-th↗
arXiv2007

Heterotic String Dynamics in the Solvable Lie Algebra Gauge

A revision of the torodial Kaluza-Klein compactification of the massless sector of the E(8)xE(8) heterotic string is given. Under the solvable Lie algebra gauge the dynamics of the O(p,q)/(O(p)xO(q)) symmetric space sigma model which is coupled to a dilaton, N abelian gauge fields and the Chern-Simons type field strength is studied in a general formalism. The results are used to derive the bosonic matter field equations of the massless sector of the D-dimensional compactified E(8)xE(8) heterotic string.

hep-th↗
arXiv2007

Non-linear Realisation of the N=2, D=6 Supergravity

We have applied the method of dualisation to construct the coset realisation of the bosonic sector of the N=2, D=6 supergravity which is coupled to a tensor multiplet. The bosonic field equations are regained through the Cartan-Maurer equation which the Cartan form satisfies. The first-order formulation of the theory is also obtained as a twisted self-duality condition within the non-linear coset construction.

hep-th↗