  We consider the exclusion process in the one-dimensional discrete torus with
$N$ points, where all the bonds have conductance one, except a finite number of
slow bonds, with conductance $N^{-\beta}$, with $\beta\in[0,\infty)$. We prove
that the time evolution of the empirical density of particles, in the diffusive
scaling, has a distinct behavior according to the range of the parameter
$\beta$. If $\beta\in [0,1)$, the hydrodynamic limit is given by the usual heat
equation. If $\beta=1$, it is given by a parabolic equation involving an
operator $\frac{d}{dx}\frac{d}{dW}$, where $W$ is the Lebesgue measure on the
torus plus the sum of the Dirac measure supported on each macroscopic point
related to the slow bond. If $\beta\in(1,\infty)$, it is given by the heat
equation with Neumann's boundary conditions, meaning no passage through the
slow bonds in the continuum.
