Kütle-çekiminin metrik kuramları: perturbasyonlar ve korunum yasaları

By focusing on the mostly used variational methods, this monograph aspires to give a unified description and comparison of various ways of constructing conserved quantities for perturbations and to study symmetries in general relativity and modified theories of gravity. The main emphasis lies on the field-theoretical covariant formulation of perturbations, the canonical Noether approach and the Belinfante procedure of symmetrisation. The general formalism is applied to build the gauge-invariant cosmological perturbation theory, conserved currents and superpotentials to describe physically important solutions of gravity theories. Meticulous attention is given to the construction of conserved quantities in asymptotically-flat spacetimes as well as in asymptotically constant curvature spacetimes such as the Anti-de Sitter space. Significant part of the book can be used in graduate courses on conservation laws in general relativity.


Problems of Massive Gravity
Boybeyi, Töre Deniz; Tekin, Bayram; Department of Physics (2021-8-5)
In this thesis, the general properties of massive gravitation theories are outlined. Particular attention is given to the van Dam-Veltman-Zakharov discontinuity which arises in the massless limit of massive theories. Also, the observational, holographic, and thermodynamic properties of these theories are mentioned.
A Three dimensional mixed formulation nonlinear frame finite element based on hu-washizu functional
Soydaş, Ozan; Sarıtaş, Afşin; Department of Civil Engineering (2013)
A three dimensional nonlinear frame finite element is presented in this analytical study by utilizing Hu-Washizu principle with three fields of displacement, strain and stress in the variational form. Timoshenko beam theory is extended to three dimensions in order to derive strains from the displacement field. The finite element approximation for the beam uses shape functions for section forces that satisfy equilibrium and discontinous section deformations along the beam. Nonlinear analyses are performed by...
Linearization in stability in gravity theories
Altaş Kiracı, Emel; Tekin, Bayram; Department of Physics (2018)
In a nonlinear theory, such as gravity, physically relevant solutions are usually hard to find. Therefore, starting from a background exact solution with symmetries, one uses the perturbation theory, which albeit approximately, provides a lot of information regarding a physical solution. But even this approximate information comes with a price: the basic premise of a perturbative solution is that it should be improvable. Namely, by going to higher order perturbation theory, one should be able to improve and ...
Conformal symmetry in field theory
Huyal, Ulaş; Tekin, Bayram; Department of Physics (2011)
In this thesis, conformal transformations in d and two dimensions and the results of conformal symmetry in classical and quantum field theories are reviewed. After investigating the conformal group and its algebra, various aspects of conformal invariance in field theories, like conserved charges, correlation functions and the Ward identities are discussed. The central charge and the Virasoro algebra are briefly touched upon.
The electronic band structure of III (in, al, ga)-v (n, as, sb) compounds and ternary alloys
Mohammad, Rezek Mahmoud Salim; Katırcıoğlu, Şenay; Department of Physics (2005)
In this work, the electronic band structure of III (In, Al, Ga) - V (N, As, Sb) compounds and their ternary alloys have been investigated by density functional theory (DFT) within generalized gradient approximation (GGA) and empirical tight binding (ETB) calculations, respectively. The present DFT-GGA calculations have shown direct band gap structures in zinc-blende phase for InN, InAs, InSb, GaN, and GaAs. However, indirect band gap structures have been obtained for cubic AlN, AlSb and AlAs com- pounds; he...
Citation Formats
B. Tekin, Kütle-çekiminin metrik kuramları: perturbasyonlar ve korunum yasaları. 2017.