864 research outputs found
Equivalent and Alternative Forms for BF Gravity with Immirzi Parameter
A detailed analysis of the BF formulation for general relativity given by
Capovilla, Montesinos, Prieto, and Rojas is performed. The action principle of
this formulation is written in an equivalent form by doing a transformation of
the fields of which the action depends functionally on. The transformed action
principle involves two BF terms and the two Lorentz invariants that appear in
the original action principle generically. As an application of this formalism,
the action principle used by Engle, Pereira, and Rovelli in their spin foam
model for gravity is recovered and the coupling of the cosmological constant in
such a formulation is obtained
Gauge invariance of complex general relativity
In this paper it is implemented how to make compatible the boundary
conditions and the gauge fixing conditions for complex general relativity
written in terms of Ashtekar variables using the Henneaux-Teitelboim-Vergara
approach. Moreover, it is found that at first order in the gauge parameters,
the Hamiltonian action is (on shell) fully gauge-invariant under the gauge
symmetry generated by the first class constraints in the case when spacetime
has the topology and has no
boundary. Thus, the statement that the constraints linear in the momenta do not
contribute to the boundary terms is right, but only in the case when
has no boundary.Comment: 9 pages, Latex file, no figures. To be published in Gen. Rel. Gra
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