horizons in Cosmology

[micomaco86572]

What is the difference of cosmological horizon and particle horizon in cosmology?

[micomaco86572]

Nobody knows the answer?

[chronon]

Take a look at http://www.chronon.org/articles/cosmichorzns.html and http://www.chronon.org/articles/Cosmological_Event_Horizon.html on my website

[micomaco86572]

Take a look at http://www.chronon.org/articles/cosmichorzns.html and http://www.chronon.org/articles/Cosmological_Event_Horizon.html on my website

Thx Chronon! I benefited a lot from your website, which is really cool! lol!

I have two more question: the cosmological horizon people often talk about actually means the the cosmological event horizon, doesn't it?
You said:"for particle horizons to occur the rate of expansion of the universe (the derivative of the scale factor with time) must be infinite at time zero.", why?

[chronon]

the cosmological horizon people often talk about actually means the the cosmological event horizon, doesn't it?I think that 'people' are sometimes confused about the issue, but that would be the most reasonable interpretation of cosmological horizon.

You said:"for particle horizons to occur the rate of expansion of the universe (the derivative of the scale factor with time) must be infinite at time zero.", why? Well a freely coasting a universe without large scale gravity or cosmological constant - the (0,0) universe, also known as the Milne universe - doesn't have particle horizons. If you transform to conformal coordinates (See http://www.astro.ucla.edu/~wright/cosmo_03.htm#MSTD) then the conformal time goes back to minus inifinity.

[micomaco86572]

But in the Milne universe we still have the boundary of the observable universe, do we? Can we refer to it as a particle horizon? thx