  Stable non-topological solitons, Q-balls, are studied using analytical and
numerical methods. Three different physically interesting potentials that
support Q-ball solutions are considered: two typical polynomial potentials and
a logarithmic potential inspired by supersymmetry. It is shown that Q-balls in
these potentials exhibit different properties in the thick-wall limit where the
charge of a Q-ball is typically considerably smaller than in the thin-wall
limit. Analytical criteria are derived to check whether stable Q-balls exists
in the thick-wall limit for typical potentials. Q-ball charge, energy and
profiles are presented for each potential studied. Evaporation rates are
calculated in the perfect thin-wall limit and for realistic Q-ball profiles. It
is shown that in each case the evaporation rate increases with decreasing
charge.
