The unified transform method (UTM) for analyzing initial-boundary value (IBV) problems provides an important generalization of the inverse scattering transform (IST) method for analyzing initial value problems. In comparison with the IST, a major difficulty of the implementation of the UTM in general is the involvement of unknown boundary values. In this paper we analyze the IBV problem for the massive Thirring model posed in the quarter plane. We show for this integrable model, the UTM is as effective as the IST method: the Riemann-Hilbert (RH) problems we formulated for such a problem have explicit (x, t)dependence and depend only on the given initial and boundary values; they do not involve additional unknown boundary values.Keywords: massive Thirring system, initial-boundary value problem, unified transform method, inverse scattering transform.
Transformations of the Lax pairFollowing [17], we transform the Lax pair (1.2) with the spectral parameter λ to two equivalent forms: one, with the new spectral parameter k, is suitable to study the behaviour for λ near origin, and the other one, with the new spectral parameter z, is suitable to study the behaviour for λ near infinity. More precisely, we introduce the following two transformationsand we introduce the new spectral parameterswhere the jump matrix J (x, t, z) and the oriented contour L = L 1 ∪ L 2 ∪ L 3 ∪ L 4 are defined as follows
47)Using the global relation (3.52) we can verify directly that {Ω (j) (t, k)} 4 1 satisfy J 1 (0, t, k)Ω (2) (t, k) = Ω (1) (t, k)J (t) (t, k), k ∈ L 1 , J 2 (0, t, k)Ω (2) (t, k) = Ω (3) (t, k)J (t) (t, k), k ∈ L 2 , J 3 (0, t, k)Ω (4) (t, k) = Ω (3) (t, k)J (t) (t, k), k ∈ L 3 , J 4 (0, t, k)Ω (4) (t, k) = Ω (1) (t, k)J (t) (t, k), k ∈ L 4 .(4.27)