Hypermagnetic knots and gravitational radiation at intermediate
  frequencies
  The maximally gyrotropic configurations of the hypermagnetic field at the
electroweak epoch can induce a stochastic background of relic gravitational
waves with comoving frequencies ranging from the $\mu$Hz to the kHz. Using two
complementary approaches we construct a physical template family for the
emission of the gravitational radiation produced by the hypermagnetic knots.
The current constraints and the presumed sensitivities of the advanced
wide-band interferometers (both terrestrial and space-borne) are combined to
infer that the lack of observations at intermediate frequencies may invalidate
the premise of baryogenesis models based (directly or indirectly) on the
presence of gyrotropic configurations of the hypermagnetic field at the
electroweak epoch. Over the intermediate frequency range the spectral energy
density of the gravitational waves emitted by the hypermagnetic knots at the
electroweak scale can exceed the inflationary signal even by nine orders of
magnitude without affecting the standard bounds applicable on the stochastic
backgrounds of gravitational radiation. The signal of hypermagnetic knots can
be disambiguated, at least in principle, since the the produced gravitational
waves are polarized.
