Topologically Stable Z - Strings in the Supersymmetric Standard Model
  We show that the minimal supergravity extension of the standard model automatically contains topologically stable electroweak strings if the hidden sector is invariant under the exact R-symmetry. These defects appear in the form of the semiglobal R-strings, which necessarily carry $Z$-flux inside their core. This result is independent from the particular structure of the hidden sector. Discussed strings differ fundamentally from the embedded $Z$-strings. If R-symmetry is explicitly broken (e.g. due to an anomaly), the decay of the semiglobal strings may have important implications for the baryogenesis. 
G. Dvali and Goran Senjanovi{\'c}