Josef Klusoň

Non-Linear Massive Gravity with Additional Primary Constraint and Absence of Ghosts

We complete the Hamiltonian analysis of a specific model of nonlinear massive gravity that was started in 2012 [J. Kluson, J. High Energy Phys. 06 (2012) 170]. We identify the primary constraint and corresponding secondary constraint. We show that they are the second class constraints and hence they lead to the elimination of the additional scalar mode. We also find that the remaining constraints are the first class constraints with the structure that corresponds to the manifestly diffeomorphism-invariant theory. Finally, we determine the number of physical degrees of freedom and we show that it corresponds to the number of physical modes of massive gravity.

Hořava-Lifshitz f(R) gravity

This paper is devoted to the construction of new type of f(R) theories of gravity that are based on the principle of detailed balance. We discuss two versions of these theories with and without the projectability condition.

Giant Magnon in NS5-brane Background.

We study the giant magnon solutions in the near horizon geometry of the Neveu-Schwarz (NS) 5-brane background. In conformal gauge, we find magnon dispersion relation in the large angular momentum (J) limit. We further show that the giant magnon poses uniform distribution of the angular momentum along the string world-sheet as in case of AdS_5\times S^5 spacetime.

Mimetic dark matter, ghost instability and a mimetic tensor-vector-scalar gravity

A bstractRecently modified gravitational theories which mimic the behaviour of dark matter, the so-called “Mimetic Dark Matter”, have been proposed. We study the consistency of such theories with respect to the absence of ghost instability and propose a new tensor-vector-scalar theory of gravity, which is a generalization of the previous models of mimetic dark matter with additional desirable features. The original model proposed by Chamseddine and Mukhanov [JHEP 11 (2013) 135] is concluded to describe a regular pressureless dust, presuming that we consider only those configurations where the energy density of the mimetic dust remains positive under time evolution. For certain type of configurations the theory can become unstable. Both alternative modified theories of gravity, which are based on a vector field (tensor-vector theory) or a vector field and a scalar field (tensor-vector-scalar theory), are free of ghost instabilities.

Giant Magnon on Deformed AdS(3)xS(3)

Studujeme řeseni klasicke bozonove struny v deformovanem AdS3xS3 prostoru, ktere odpovida gigantickemu magnonu. Řesime tyto pohybove rovnice při zakalibrovani teorie v konformni kalibraci. Pote urcime dispersni relaci a ukažeme, že v limitě, kdy deformacni parametr jde k nule, se redukuje na slavnou Hofman-Maldacena dispersni relaci.

Comments about Hamiltonian formulation of non-linear massive gravity with Stückelberg fields

A bstractWe perform the Hamiltonian analysis of some form of the non-linear massive gravity action that is formulated in the Stückelberg formalism. Following seminal analysis performed in arXiv:1203.5283 [hep-th] we find that this theory possesses one primary constraint which could eliminate one additional mode in this theory. We performed the explicit Hamiltonian analysis of two dimensional non-linear massive gravity and we found that this is theory free from the ghosts.

New proposal for non-linear ghost-free massive F(R) gravity: Cosmic acceleration and Hamiltonian analysis

Abstract We propose new version of massive F ( R ) gravity which is natural generalization of convenient massive ghost-free gravity. Its Hamiltonian formulation in scalar-tensor frame is developed. We show that such F ( R ) theory is ghost-free. The cosmological evolution of such theory is investigated. Despite the strong Bianchi identity constraint the possibility of cosmic acceleration (especially, in the presence of cold dark matter) is established. Ghost-free massive F ( R , T ) gravity is also proposed.

Hamiltonian analysis of curvature-squared gravity with or without conformal invariance

Analyzujeme gravitacni teorie se cleny vyssich řadů v křivosti, kde specialnim připadem je Weylovska gravitace. Urcime lokalni podminky, ktere urcuji pocet fyzikalnich stupňů volnosti.

U(1) Invariant F(\tilde{R}) Hořava–Lifshitz gravity

This paper is devoted to the study of various aspects of projectable F(R) Hořava–Lifshitz (HL) gravity. We show that some versions of F(R) HL gravity may have stable de Sitter solution and unstable flat-space solution. In this case, the problem of scalar graviton does not appear because flat space is not vacuum state. Generalizing the U(1) HL theory proposed in arXiv:1007.2410, we formulate U(1) extension of scalar theory and of F(R) Hořava–Lifshitz gravity. The Hamiltonian approach for such the theory is developed in full detail. It is demonstrated that its Hamiltonian structure is the same as for the non-relativistic covariant HL gravity. The spectrum analysis performed around the flat background indicates the consistency of the theory because it contains a graviton with only transverse polarization. Finally, we analyze the spatially flat FRW equations for U(1) invariant F(R) Hořava–Lifshitz gravity.

Hamiltonian analysis of the Higgs mechanism for gravity

In this paper, we perform the canonical description of the Higgs mechanism for gravity and provide the Hamiltonian definition of massive gravities.