A solution with unusual features appearing in some theories of gravitation is the wormhole configuration. Wormholes can be understood as tunnels connecting two universes or two distant points in the same universe. One of their most remarkable aspects is that they allow for the formation of closed timelike curves. Another important feature of this kind of space-time solutions is the requirement of matter violating the energy conditions as their source. Both characteristics may seem somewhat unrealistic, but the known laws of Physics do not forbid them. Consequently, it is interesting to study whether wormholes do exist in nature or not, through observational effects due to their existence. This idea was adopted in S.P.Bergliaffa and K.Hibberd Phys.Rev.D62:044045,2000, where the propagation of electromagnetic waves in a spherically symmetric wormhole is studied. Any ressonance in the transmission coefficient of waves crossing the wormhole throat would be seen as absorption lines, thus providing information about the size of the throat. Altough, in this simple case, no ressonances were found, it was indeed helpful for the future analysis of more important cases from the astrophysical viewpoint.

One such configuration that may become relevant for Astrophysics is that of a rotating wormhole. This case was already studied previously, but attention was given only to the geometrical aspects of the problem. In a recent communication (S.P.Bergliaffa and K.Hibberd, gr-qc/0006041) it is shown that, although rotating wormholes may be generated by a perfect fluid source, in most cases a more complicated fluid is indeed required (for instance, showing anisotropical stress or heat flow).

The (still unresolved) central problem is related to the description of the matter generating the wormhole. In spite of some constraints, its energy-momentum tensor is not uniquely determined, and so the wormholes are by no means unique solutions of Eisntein equations. Using results developed in Quantum Field Theory in curved spaces, the matter content shall be restricted as much as possible; in particular, constraints upon the negative energy density based on quantum inequalities will be applied in the case of a generic wormhole, in order to study more specific observational consequences of the existence of these objects.