- #1
meteor
- 940
- 0
I see often that rhocrit(the critical density of matter), is expressed this way:
rhocrit=(3*(H^2))/(8*pi*G)
This is not correct because a cosmological constant is missed.
This is the Friedmann Equation:
H^2=((8*pi*G*rhocrit)/3)+(lambda/3)-(k/(a^2))
Since it is known that the curvature(k)of the universe is zero, the Friedmann equation can be reduced to this:
H^2=((8*pi*G*rhocrit)/3)+(lambda/3)
and rhocrit is:
rhocrit=(3*((H^2)-(lambda/3)))/(8*pi*G)
Now, i would like to solve this equation. I have a value for rhocrit of 10^(-26)kg/m^3, but i need the value of the cosmological constant to complete the equation. You know the value? (in SI units, please)
also given that H=((da/dt)/da), being a the scale factor and H=Hubble constant, it would be nice to know the current value of the scale factor
rhocrit=(3*(H^2))/(8*pi*G)
This is not correct because a cosmological constant is missed.
This is the Friedmann Equation:
H^2=((8*pi*G*rhocrit)/3)+(lambda/3)-(k/(a^2))
Since it is known that the curvature(k)of the universe is zero, the Friedmann equation can be reduced to this:
H^2=((8*pi*G*rhocrit)/3)+(lambda/3)
and rhocrit is:
rhocrit=(3*((H^2)-(lambda/3)))/(8*pi*G)
Now, i would like to solve this equation. I have a value for rhocrit of 10^(-26)kg/m^3, but i need the value of the cosmological constant to complete the equation. You know the value? (in SI units, please)
also given that H=((da/dt)/da), being a the scale factor and H=Hubble constant, it would be nice to know the current value of the scale factor
Last edited: