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Two-Dimensional tomography with unknown view angles
We consider uniqueness of two-dimensional parallel beam tomography
with unknown view angles. We show that infinitely many projections
at unknown view angles of a sufficiently asymmetric object determine
the object uniquely. An explicit expression for the required
asymmetry is given in terms of the object's geometric moments. We
also show that under certain assumptions finitely many projections
guarantee uniqueness for the unknown view angles. Compared to
previous results about uniqueness of view angles, our result reduces
the minimum number of required projections to approximately half and
is applicable to a larger set of objects. Our analysis is based on
algebraic geometric properties of a certain system of homogeneous
polynomials determined by the Helgason-Ludwig consistency
conditions.