The factorization method for the inverse acoustic scattering problems with limited aperture data

We study the factorization method for the inverse acoustic scattering problems in the case of limited aperture data. In this case, the factorization of the far field operator is not symmetric. So, we can not apply the original factorization method which requires the symmetricity of the factorization. In this paper, we provide a new functional analytic theorem corresponding to the case of limited aperture data, and by applying it, we give the characterizations of the unknown domain.