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en.wikipedia.org/wiki/Friedmann_equations

The Friedmann equations are a set of equations in physical cosmology that govern the expansion of space in homogeneous and isotropic models of the universe within the context of general relativity.They were first derived by Alexander Friedmann in 1922 from Einstein's field equations of gravitation for the Friedmann–Lemaître–Robertson–Walker metric and a perfect fluid with a given mass ...

diposit.ub.edu/dspace/bitstream/2445/59759/1/TFG-Arnau-Romeu-Joan.pdf

Derivation of Friedman equations Author: Joan Arnau Romeu Facultat de F sica, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain. Abstract: In this report we make a detailed derivation of Friedman Equations, which are the dy-namical equations of a homogeneous and isotropic universe. First, we derive them in the framework

astronomy.nmsu.edu/aklypin/COSMOLOGY/SimpleDerivation.pdf

Friedmann Equation: Newtonian derivation Consider a sphere, which expands in a homogeneous Universe. For non-relativistic particles the mass inside the sphere is constant. We need to find how the radius of the sphere changes with time. Later we will add corrections due to effects of GR.

www.astronomy.ohio-state.edu/~dhw/A5682/notes4.pdf

A5682: Introduction to Cosmology Course Notes The Friedmann Equationin GR A proper derivation of the Friedmann equation begins by inserting the Friedmann-Robertson-Walker metric into the Einstein Field Equation. Since GR yields the Newtonian limit, we should expect the small scale behavior to resemble that

hyperphysics.phy-astr.gsu.edu/hbase/Astro/fried.html

The Friedmann Equation Alexander Friedmann of Russia is credited with developing a dynamic equation for the expanding universe in the 1920s. This was a time when Einstein, Willem de Sitter of the Netherlands, and Georges Lemaitre of Belgium were also working on equations to model the universe.

uncw.edu/phy/documents/thefriedmannequations.pdf

Alexander A. Friedmann (1888-1925) The Man Who Made the Universe Expand Soviet mathematician and meteorologist Most famous for contributions to cosmology First person to mathematically predict an expanding universe (1922) Derived from Einstein's general relativity Einstein initially dismissed Friedmann’s equations

astrobites.org/2011/10/09/general-relativity-friedmann-equations-and...

We point this out simply as historical context for what follows. We turn now to a derivation of the equations Friedmann would have used to produce this model, and that more generally constrain the evolution of any model universe given certain initial inputs. Derivation of the Friedmann equations from general relativity

en.wikipedia.org/wiki/Talk:Friedmann_equations

Then a can be updated with the first Friedmann equation; and ρ with the continuity equation. Pressure p must be provided by the added equation. Exact solutions are possible in some special cases (see Friedmann equations#Useful solutions). If we assume k=0 and = for some constant w ≠ −1, then

www1.maths.leeds.ac.uk/~serguei/teaching/cosmology.pdf

13 Robertson-Walker metric and Friedmann equations 48 ... we will outline its key ideas and describe how the basic equations of theoretical Cosmology arise from the relativistic theory of gravity. Finding solutions to these equations and their analysis ... Analytic derivation: This type of approach works for any coordinate transformation.

universeinproblems.com/index.php/Friedman_equations

Show that among the three equations (two Friedman equations and the conservation equation) only two are independent, i.e. any of the three can be obtained from the two others. solution The derivation of the conservation equation from the two Friedman equations was discussed above .