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The vibrating string is a source of gravitational waves which requires novelcomputational techniques, based on the explicit construction of a conserved andrenormalized (in a classical sense) energy-momentum tensor. The renormalizationis necessary to take into account the effect of external constraints, whichaffect the emission considerably. Vibrating media offer in general a testingground for reconciling conflicts between General Relativity and other branchesof physics; however, constraints are absent in sources like the Weber bar, forwhich the standard covariant formalism for elastic bodies can also be applied.Our solution method is based on the linearized Einstein equations, but relaxesother usual assumptions like far-field approximation, spherical or plane wavesymmetry, TT gauge and source without internal interference. The stringsolution is then adapted to give the radiation field of a transversal Alfvenwave in a rarefied plasma, where the tension is produced by an external staticmagnetic field. Like for the string, the field strength turns out to beindependent from the frequency. We give a preliminary example of a numericalsolution based on parameters referred to Alfven waves in the solar corona.Further astrophysical applications require an extension of the solutionprocedure to second order in the amplitude, and consideration of bordereffects. Future work will also address numerical and analytical near-fieldsolutions.

Gravitational radiation of a vibrating physical string as a model for the gravitational emission of an astrophysical plasma