Recent content by EhsanZ

Thanks, but here appears another question. So why do we define a=R/R0 at all, when R0=1? It means a(t)=R(t), and it is just changing names, isn't it?!

Number?

What is the current value of the scale factor(R₀)? a= R(t)/R₀ Give me the number. Thanks

What is the current value of the scale factor(R₀)? a= R(t)/R₀ Give me the number.

In equation below 〖H₁〗^2/〖H₀〗^2 =Ω₀(cri) (R₀⁴)/(R₁⁴(1+z(eq))) Why is the term “(1+z(eq))” negligible in denominator according to the term “ R₁⁴ ” ? Weinburg did it in his book named "Cosmology".

Yes, you're right my friend. I should've written it more carefully. Thanks

I meant the notation that Hobson had used in his book named "General Relativity: An Introduction for Physicists ".

Doesn't matter! Everybody makes mistakes.:smile:

No my friend! U made a mistake.

With Hobson's notation: H=(da/dt)/a dH/dt = ((d2a/dt2)/a) - ((da/dt)/a)2 If ((d2a/dt2)/a) is negative, (dH/dt) is certainly negative. But if ((d2a/dt2)/a) is positive, (dH/dt) can be positive or negative. What is your interpretation?

What is the exact calculation of Particle horizon in Lemaître model? Does it exist? Is it finite or infinite? Can anyone calculate that integral? Thanks