  We investigate the transverse fluctuations of the confining string connecting
two static quarks in (2+1)-d SU(2) Yang-Mills theory using Monte Carlo
calculations. The exponentially suppressed signal is extracted from the large
noise by a very efficient multi-level algorithm. The resulting width of the
string increases logarithmically with the distance between the static quark
charges. Corrections at intermediate distances due to universal higher order
terms in the effective string action are calculated analytically. They
accurately fit the numerical data.
