Positive semidefinite germs on the cone

@inproceedings{Fernando2002PositiveSG,
  title={Positive semidefinite germs on the cone},
  author={Jos{\'e} F. Fernando and Jes{\'u}s M. Ruiz},
  year={2002}
}
We show that any positive semidefinite analytic function germ on the cone z 2 = x 2 + y 2 is a sum of two squares of analytic function germs.