  Euclidean point-to-point propagators or wall-to-wall correlators related to
exchange by an unstable particle(sigma,rho,omega-mesons) are modified by
presence of particle width. In particular, the usual method of deriving
particle masses from logarithmic derivatives need to be modified. Similarly
Yukawa-like potentials of nuclear physics due to exchange of those mesons are
significantly modified since the coupling to the decay products is strong. For
example, the large distance asymptotic changes, exp(-M_{min} r), where M_{min}
is the sum of the decay product masses
  (2 m_{\pi}, 2 m_{e}, 2 m_{\nu}). In the area M_{min}r<1the potential has a
long-range tail 1/r^3. Similar effects appear due to the virtual decays in the
elecroweak sector of the Standard model. The $Z-\gamma$ mixing via electron
loop gives the parity violation potential with the range $1/2 m_{e}$, i.e. the
range of the weak interaction increases $10^{5}$ times.
