4 research outputs found
Matter Lagrangians Coupled with Connections
We shall here consider extended theories of gravitation in the metric-affine
formalism with matter coupled directly to the connection. A sufficiently
general procedure will be exhibited to solve the resulting field equation
associated to the connection. As special cases one has the no-coupling case
(which is standard in f(R) literature) as well as the cases already analyzed in
ref.[1].Comment: Refs adde
Covariant Lagrangian Formulation of Chern-Simons and BF Theories
We investigate the covariant formulation of Chern-Simons theories in a
general odd dimension which can be obtained by introducing a vacuum connection
field as a reference. Field equations, Noether currents and superpotentials are
computed so that results are easily compared with the well-known results in
dimension 3. Finally we use this covariant formulation of Chern-Simons theories
to investigate their relation with topological BF theories.Comment: 23 pages, refs. adde
New Cases of Universality Theorem for Gravitational Theories
The "Universality Theorem" for gravity shows that f(R) theories (in their
metric-affine formulation) in vacuum are dynamically equivalent to vacuum
Einstein equations with suitable cosmological constants. This holds true for a
generic (i.e. except sporadic degenerate cases) analytic function f(R) and
standard gravity without cosmological constant is reproduced if f is the
identity function (i.e. f(R)=R). The theorem is here extended introducing in
dimension 4 a 1-parameter family of invariants R' inspired by the
Barbero-Immirzi formulation of GR (which in the Euclidean sector includes also
selfdual formulation). It will be proven that f(R') theories so defined are
dynamically equivalent to the corresponding metric-affine f(R) theory. In
particular for the function f(R)=R the standard equivalence between GR and
Holst Lagrangian is obtained.Comment: 10 pages, few typos correcte