Harmonic measures of slit sides perpendicular to the domain boundary
  The article is devoted to the geometry of solutions to the chordal Loewner equation which is based on comparison of singular solutions and harmonic measures for the sides of a slit in domains generated by a driving term. It is proved that harmonic measures of two sides of a slit in the upper half-plane which is perpendicular to the real axis are asymptotically equal to each other. 
Dmitri Prokhorov and Andrey Zakharov
math.CV