  For Anderson localization models, there exists an exact real-space
renormalization procedure at fixed energy which preserves the Green functions
of the remaining sites [H. Aoki, J. Phys. C13, 3369 (1980)]. Using this
procedure for the Anderson tight-binding model in dimensions $d=2,3$, we study
numerically the statistical properties of the renormalized on-site energies
$\epsilon$ and of the renormalized hoppings $V$ as a function of the linear
size $L$. We find that the renormalized on-site energies $\epsilon$ remain
finite in the localized phase in $d=2,3$ and at criticality ($d=3$), with a
finite density at $\epsilon=0$ and a power-law decay $1/\epsilon^2$ at large $|
\epsilon |$. For the renormalized hoppings in the localized phase, we find:
${\rm ln} V_L \simeq -\frac{L}{\xi_{loc}}+L^{\omega}u$, where $\xi_{loc}$ is
the localization length and $u$ a random variable of order one. The exponent
$\omega$ is the droplet exponent characterizing the strong disorder phase of
the directed polymer in a random medium of dimension $1+(d-1)$, with
$\omega(d=2)=1/3$ and $\omega(d=3) \simeq 0.24$. At criticality $(d=3)$, the
statistics of renormalized hoppings $V$ is multifractal, in direct
correspondence with the multifractality of individual eigenstates and of
two-point transmissions. In particular, we measure $\rho_{typ}\simeq 1$ for the
exponent governing the typical decay $\overline{{\rm ln} V_L} \simeq
-\rho_{typ} {\rm ln}L$, in agreement with previous numerical measures of
$\alpha_{typ} =d+\rho_{typ} \simeq 4$ for the singularity spectrum $f(\alpha)$
of individual eigenfunctions. We also present numerical results concerning
critical surface properties.
