  The equilibrium dynamics of the spin-1/2 XX chain is re-examined within a
recently developed formalism based on the quantum transfer matrix and a thermal
form factor expansion.
  The transversal correlation function is evaluated in real time and space. The
high-accuracy calculation reproduces several exact results in limiting cases as
well as the well-known asymptotic formulas obtained by the matrix
Riemann-Hilbert approach.
  Furthermore, comparisons to numerical data based on a direct evaluation of
the Pfaffian as well as to asymptotic formulas obtained within non-linear
Luttinger liquid theory are presented.
