Vikman, Alexander (2007): Kessence: cosmology: causality and emergent geometry. Dissertation, LMU München: Faculty of Physics 

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Abstract
In this work we consider different aspects of kessence theories, which are scalar field theories described by the generally covariant and Lorentz invariant action with noncanonical kinetic terms. It is shown that, because of the intrinsic nonlinearity, these theories can have rather unexpected and unusual physical properties. As in the usual relativistic field theories, any nontrivial dynamical solution of the kessence equation of motion spontaneously breaks the Lorentz invariance. Thus the perturbations around such solutions propagate in a "new aether". In contrast to the usual relativistic field theories, these perturbations propagate in an "effective" metric which is different from the usual gravitational metric. This effective metric can be interpreted as the socalled "emergent spacetime". In this thesis we show that the dynamics of the perturbations can be described by the action which is generally covariant with respect to the reparameterization of this "emergent spacetime". The most interesting manifestation of this "emergent spacetime" is that perturbations can propagate faster than light. We show that despite the superluminal propagation the causal paradoxes do not arise in these theories, and in this respect these theories are not less safe than General Relativity. This superluminal propagation of perturbations has interesting consequences for cosmology and black hole physics. In particular, it is possible to construct models of inflation with an enhanced production of gravitational waves. This in turn can be verified in the nearest future by the observations of the Bmode polarization of the Cosmic Microwave Background Radiation (CMBR). Moreover, we have shown that there exist kessence models which in principle allow to obtain information from the region beyond the black hole horizon. This information is encoded in the perturbations around the solution describing the stationary accretion of the kessence onto the black hole. In addition, we discuss the possible dynamical violation of the Null Energy Condition (NEC) in the kessence models. The violation of NEC by the dynamical Dark Energy (DE) is not excluded and even slightly preferred by observations Moreover, the violation of NEC plays a crucial role in the preBigBang scenarios. We have shown that in the framework of general kessence the dynamical violation of NEC is physically implausible.
Item Type:  Thesis (Dissertation, LMU Munich) 

Keywords:  kessence, cosmology, superluminal propagation, black holes, inflation, gravitational waves 
Subjects:  600 Natural sciences and mathematics > 530 Physics 600 Natural sciences and mathematics 
Faculties:  Faculty of Physics 
Language:  English 
Date Accepted:  30. November 2007 
1. Referee:  Mukhanov, Viatcheslav 
Persistent Identifier (URN):  urn:nbn:de:bvb:1977612 
MD5 Checksum of the PDFfile:  e20632c0fd86b33f891771b45f3c8e21 
Signature of the printed copy:  0001/UMC 16616 
ID Code:  7761 
Deposited On:  05. Dec 2007 07:17 
Last Modified:  19. Jul 2016 16:23 