# Can pre-inflationary gravitational attraction affect objects after inflation?

According to inflation theory, the inflation itself took place at some short yet finite time after Big Bang, so there should be some gravitational interactions present before inflation, some objects started accelerating towards other objects etc. However after inflation many of those objects were scattered outside of their neighbours' light cones and as gravity propagates with the speed of light the interaction between such objects should be interrupted. Yet what about the initial acceleration that these objects gained before the inflation occurred? Shouldn't these objects still be moving in their original pre-inflationary direction? And how would such forces shape the present Universe?

• Would you mind clarifying what you mean by "objects", bearing in mind the conditions immediately after the big bang. Thanks – user81619 Jun 23 '15 at 0:56
• By objects I mean any form of matter which could exist at that time, so probably nothing more than the most elementary particles. – Ardath Jun 23 '15 at 20:22

$$D = 2\frac{\dot{a}}{a}\mathbf{u}$$
where $\mathbf{u}$ is the comoving velocity and $a$ is the scale factor. This isn't a real force, it's the result of the universe expanding away from the moving object, but the end result is that in an expanding universe freely moving objects appear to slow down.
The key parameter is that factor of $\dot{a}/a$. The numerator, $\dot{a}$ is the rate of change of the scale factor, and during inflation this was absolutely enormous and produced a huge Hubble drag. The end result is that any peculiar velocities that particles had before inflation were reduced to essentially zero by the time inflation ended.