We extend previous analyses of soliton solutions in (4 + 1) gravity to new ranges of their defining parameters. The geometry, as studied using invariants, has the topology of worm-holes found in (3 + 1) gravity. In the induced-matter picture, the fluid does not satisfy the strong energy conditions, but its gravitational mass is positive. We infer the possible existance of (4 + 1) wormholes which, compared to their (3 + 1) counterparts, are less exotic.

We consider a modification of the standard Einstein theory in four dimensions, alternative to R. Jackiw and S.-Y. Pi, Phys. Rev. D 68, 104012 (2003), since it is based on the first-order (Einstein-Cartan) approach to General Relativity, whose gauge structure is manifest. This is done by introducing an additional topological term in the action which becomes a Lorentz-violating term by virtue of the dependence of the coupling on the space-time point. We obtain a condition on the solutions of the Einstein equations, such that they persist in the deformed theory, and show that the solutions remarkably correspond to the classical solutions of a collection of independent 2 + 1-d (topological) Chern-Simons gravities. Finally, we study the relation with the standard second-order approach and argue that they both coincide to leading order in the modulus of the Lorentz-violating vector field.

A generic massive Thirring Model in three space-time dimensions exhibits a correspondence with a topologically massive bosonized gauge action associated to a self-duality constraint, and we write down a general expression for this relationship.We also generalize this structure to d dimensions, by adopting the so-called doublet approach, recently introduced. In particular, a non-conventional formulation of the bosonization technique in higher dimensions (in the spirit of d = 3), is proposed and, as an application, we show how fermionic (Thirring-like) representations for bosonic topologically massive models in four dimensions may be built up. *