Viable higher derivative theories

Özönder, Şener
In this thesis, higher derivative theories are investigated. Ostrogradskian instability of higher derivative theories is examined both at the classical and quantum levels. It is shown that avoiding the instability in nondegenerate higher derivative theories is impossible. Moreover, the degenerate model of relativistic particle with a curvature term is studied as a viable higher derivative theory. Most of the work we present here is not original. We give a review of the literature and compile various detached works that already exist.


Quantum decoherence and quantum state diffusion formalism
Dumlu, Cesim Kadri; Turgut, Sadi; Department of Physics (2007)
Foundational problems of quantum theory, regarding the appearance of classicality and the measurement problem are stated and their link to studies of open quantum systems is discussed. This study's main aim is to analyze the main approaches that are employed in the context of open quantum systems. The general form of Markovian master equations are derived by a constructive approach. The Quantum State Diffusion (QSD) formalism is stressed upon as an alternative method to the master equations. Using the Calde...
Massive higher derivative gravity theories
Güllü, İbrahim; Tekin, Bayram; Department of Physics (2011)
In this thesis massive higher derivative gravity theories are analyzed in some detail. One-particle scattering amplitude between two covariantly conserved sources mediated by a graviton exchange is found at tree-level in D dimensional (Anti)-de Sitter and flat spacetimes for the most general quadratic curvature theory augmented with the Pauli-Fierz mass term. From the amplitude expression, the Newtonian potential energies are calculated for various cases. Also, from this amplitude and the propagator structu...
Spontaneous Lorentz violation: the case of infrared QED
Balachandran, A. P.; Kürkcüoğlu, Seçkin; de Queiroz, A. R.; VAİDYA, SACHİN (2015-02-24)
It is by now clear that the infrared sector of quantum electrodynamics (QED) has an intriguingly complex structure. Based on earlier pioneering work on this subject, two of us recently proposed a simple modification of QED by constructing a generalization of the U(1) charge group of QED to the "Sky" group incorporating the well-known spontaneous Lorentz violation due to infrared photons, but still compatible in particular with locality (Balachandran and Vaidya, Eur Phys J Plus 128:118, 2013). It was shown t...
Effective gauge theories from fuzzy extra dimensions
Ünal, Gönül; Kürkcüoğlu, Seçkin; Department of Physics (2016)
In this thesis, we investigate the formulation and various aspects of gauge theories with fuzzy extra dimensions. In SU (N ) gauge theories coupled to a suitable number of adjoint scalar fields, we determine a family of fuzzy vacuum configurations dynamically emerging after the spontaneously symmetry breaking of the gauge symmetry. The emergent models are conjectured to be effective U (n) (n < N ) gauge theories with fuzzy extra dimensions. Making use of the equivariant parametrization technique and focusin...
Basics of massive spin-2 theories
Kürekçi, Şahin; Tekin, Bayram; Department of Physics (2015)
In this thesis, basics of massive spin-2 theories are studied. The theory of general relativity cannot explain some problems in very small and in very large scales and it needs a modification. The way of modifying general relativity by giving mass to the propagating particle graviton is called massive gravity. The first correct massive gravity theory is the linear theory written by Fierz and Pauli. However, later on it has been found that this theory does not match up with the physical predictions of genera...
Citation Formats
Ş. Özönder, “Viable higher derivative theories,” M.S. - Master of Science, Middle East Technical University, 2007.