  We assume that the galactical dark matter halo, considered composed of an
axionlike particles Bose-Einstein condensate \cite{pir12}, can present
topological defects, namely domain walls, arising as the dark soliton solution
for the Gross-Pitaevskii equation in a self-graviting potential. We investigate
the influence that such substructures would have in the gravitational
interactions within a galaxy. We find that, for the simple domain wall model
proposed, the effects are too small to be identified, either by means of a
local measurement of the gradient of the gravitational field or by analysing
galaxy rotation curves. In the first case, the gradient of the gravitational
field in the vicinity of the domain wall would be $10^{-31}\; (m/s^2)/m$. In
the second case, the ratio of the tangential velocity correction of a star due
to the presence of the domain wall to the velocity in the spherical symmetric
case would be $10^{-8}$.
