宇宙論 · 学部

Cosmological Constant

The constant energy density term associated with accelerated expansion.

公開 2026年4月26日 · 1 分

PDF View

The PDF file is linked, but it has not been added yet.

/sources/cosmological-constant.pdf

In Einstein’s Equation

The cosmological constant appears as

G_{\mu\nu}+\Lambda g_{\mu\nu}=\frac{8\pi G}{c^4}T_{\mu\nu}.

It can be moved to the matter side and interpreted as a constant vacuum energy density.

Vacuum energy has

p_\Lambda = -\rho_\Lambda c^2.

The negative pressure makes it contribute positively to $\ddot a$ in the Friedmann acceleration equation.

A standard introductory path through expansion, Friedmann dynamics, distance scales, and the thermal history of the universe.

The density that makes the spatial curvature term vanish for a given Hubble rate.

The equations governing the expansion of a homogeneous and isotropic universe.