Why do we need the inflaton to expland space-time?

[fairy._.queen]

Hi all!
Fields associated with a particle affect other particles and their fields and that's ok.
But why would a particle affect the space-time (which is not a particle) making it expand?
Thank you in advance!

 

[Mordred]

Energy/particle fields have energy mass density. Density is equivalent to pressure.

 

[fairy._.queen]

You mean through an equation of state?

Also, although I know the Friedmann equations, it is not clear to me why the fluid pressure, should it be negative, would cause the space-time to expand faster.

 

[Mordred]

Essentially the ratio of actual density to critical density.
https://www.physicsforums.com/showthread.php?t=694499

this thread shows the math some of the math involved. Though it doesn't cover the equations of state as its a curvature article.

Related articles can be found in the links in my signature

gravity being assigned as positive pressure would need the cosmological constant to be negative pressure to have expansion.

 

[fairy._.queen]

Thank you!