Are signatures of anti-de-Sitter black hole at the Galactic Center?
  Using Schwarzschild -- de-Sitter (Kottler) metric we derive a simple
analytical relation between a shadow size and $\Lambda$-term. Current
observations of the smallest spot to evaluate shadow size at the Galactic
Center do not reach an accuracy comparable with cosmological $\Lambda$-term
$\sim 10^{-52}{\rm m}^{-2}$, however, if in reality we have dark energy instead
of a constant $\Lambda$-term then dark energy may be a function depending on
time and space and it could be approximated with a local constant
$\Lambda$-term near the Galactic Center and it is important to introduce a
procedure to evaluate the $\Lambda$-term. We suggest such a procedure based on
a black hole shadow evaluation. Surprisingly, current observational estimates
of shadows are in agreement with anti-de-Sitter spacetimes corresponding to a
negative $\Lambda$-term which is about $-0.4\times 10^{-20}{\rm m}^{-2}$. A
negative $\Lambda$-term has been predicted in the framework of a some class of
multidimensional string models.
