2.II.31E

Integrable Systems
Part II, 2007

Solve the following linear singular equation

(t+t1)ϕ(t)+(tt1)πifCϕ(τ)τtdτ(t+t1)2πiC(τ+2τ1)ϕ(τ)dτ=2t1\left(t+t^{-1}\right) \phi(t)+\frac{\left(t-t^{-1}\right)}{\pi i} f_{C} \frac{\phi(\tau)}{\tau-t} d \tau-\frac{\left(t+t^{-1}\right)}{2 \pi i} \oint_{C}\left(\tau+2 \tau^{-1}\right) \phi(\tau) d \tau=2 t^{-1}

where CC denotes the unit circle, tCt \in C and fCf_{C} denotes the principal value integral.