function feq0=boltfeq0(T)
%-----------------------------------------------------------------------
% Specify the function to be solved
% We want to solve for T such that boltmean(T) = v_target,
% which, in the standard form "f(x)=0" is
%     0 = boltmean(T) - v_target
%-----------------------------------------------------------------------
      global v_target
      feq0 = boltmean(T) - v_target;