We consider the solution space of the noncommutative KP hierarchy with the noncommutative extension of the Sato theory. The noncommutative deformation of the Toda hierarchy is introduced. We derive the bilinear identities for the BakerAkhiezer functions and calculate the N -soliton solutions of the noncommutative Toda hierarchy.
Noncommutative KP and Toda hierarchyRecently, the classical and quantum field theory over the noncommutative (NC) space times is extensively studied. The NC gauge theory has a great success in the string theory. In particular, the NC deformation of the ADHM construction of the (anti)SDYM equation [9] and the Nahm construction [1] were shown. It seems to imply the significance of the NC deformation of the integrable systems. Some authors have discussed the NC integrable systems on lower dimension [2,3,6,13,17] (See also [5,15,16]), especially the NC KP hierarchy. In this letter, we study the moduli space of the NC KP hierarchy throughout the Birkhoff decomposition of a certain formal group over a NC algebra. We also introduce the NC Toda hierarchy and derive the bilinear identities and the N -soliton solutions.Let (t 1 ,t 2 , · · · ) be coordinates of NC plane R 2∞ which satisfy [t i ,t j ] = iθ ij , and A θ a set of functions on it. The deformation parameters θ ij ∈ R are non-zero constants and we assume that a matrix (θ ij ) is invertible. By an orthogonal change of coordinates as [t 2n−1 ,t 2n ] = iθ n (n ≥ 1), the algebra is realized as operators over the Fock spaceThe NC KP hierarchy of the operator form is defined as follows [2,3,17]. We consider an operator valued monic pseudo differential operator (PDO)