Well, they are purely gravitational.
I should have said matter instead of mass, actually.
There is a subtle difference...
Actually,
with Kaluza-Klein theory you can completely describe a universe with gravity
and electricity and magnetism (light) using
only the theory of general relativity (gravity).
The question was:
What are phisical parameters of ' non-trivial universes without mass ' ?
The answer was:
Well, they ( parameters ) are purely gravitational.
I should have said matter instead of mass, actually.
There is a subtle difference...
Actually,
with Kaluza-Klein theory you can completely describe a universe
with gravity and electricity and magnetism (light) using only
the theory of general relativity (gravity).
===..
My conclusion from Niflmir answer:
Hmm.
I asked the parameters of ' non-trivial universes without mass '
and Niflmir answered :
. . they ( parameters ) are purely gravitational (
Matter / Mass )
. . .
with Kaluza-Klein theory you can completely describe a universe
with gravity (
Matter / Mass ) and electricity and magnetism (light)
using only the theory of general relativity (gravity).
=.
But which theory I need to know in order to understand
the parameters of ' non-trivial universes
without mass ' ?
!!!
===...