wrote:
It is possible to consider that as a possible explanation provided
that the hypothesis of exotic dark matter can ever be shown to exist
physically, which it can't.

Sorry, that is incorrect. It has been shown there is more
matter associated with galaxies than we can see. The part
we can see is thought to be about 5% of the universe. Dark
matter possesses conventional gravity and apparently makes
up about 30% of the universe.

For that hypothesis to be true, of course we must
verify that alleged exotic matter, which cannot be observed, has a
negative gravitational force relative to physical mass, ...

Sorry, that is incorrect. The thing thought to be responsible
for the expansion of the universe is Dark Energy causing an
expansion pressure. Dark Energy is thought to account for
65% of the universe.
--
73, Cecil http://www.w5dxp.com
"According to the general theory of relativity,
space without ether is unthinkable." Albert Einstein