The effective and efficient numerical solution of Riemann–Hilbert problems has been demonstrated in recent work. With the aid of ideas from the method of nonlinear steepest descent for Riemann– Hilbert problems, the resulting numerical methods have been shown numerically to retain accuracy as values of certain parameters become arbitrarily large. The primary aim of this paper is to prove that t...

The theory of Hilbert spaces of entire functions [1] was developed by Louis de Branges in the late 1950s and early 1960s with the help of his students including James Rovnyak and David Trutt. It is a generalization of the part of Fourier analysis involving Fourier transform and Plancherel formula. The de Branges-Rovnyak theory of square summable power series, which played an important role in l...

The goal of this note is to show that the Riemann-Hilbert problem to find multivalued analytic functions with SL(2,C)-valued monodromy on Riemann surfaces of genus zero with n punctures can be solved by taking suitable linear combinations of the conformal blocks of Liouville theory at c = 1. This implies a similar representation for the isomonodromic tau-function. In the case n = 4 we thereby g...

The pure braid group Γ of a quadruply-punctured Riemann sphere acts on the SL(2, C)-moduli M of the representation variety of such sphere. The points in M are classified into Γ-orbits. We show that, in this case, the monodromy groups of many explicit solutions to the Riemann-Hilbert problem are subgroups of SU(2). Most of these solutions are examples of representations that have dense images in...

Consideration in this present paper is the long-time asymptotics of solutions to derivative nonlinear Schrödinger (DNLS) equation with step-like initial value q(x,0)=q0(x)=A1eiϕe2iBx,x<0,A2e−2iBx,x>0,by Deift-Zhou method. The problem described by a matrix Riemann-Hilbert problem. A crucial ingredient used introduce g-function mechanism for solving entries jump growing exponentially as t→∞. It s...