critical density (redirected from Friedmann equations)

critical density [′krid·ə·kəl ′den·səd·ē]

(astronomy)

The mass density above which, it is believed, the expansion of the universe will slow down and reverse.

(chemistry)

The density of a substance exhibited at its critical temperature and critical pressure.

(civil engineering)

For a highway, the density of traffic when the volume equals the capacity.

(geology)

That degree of density of a saturated, granular material below which, as it is rapidly deformed, it will decrease in strength and above which it will increase in strength.

(thermodynamics)

The density of a substance at the liquid-vapor critical point.

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critical density

That unit weight of a saturated granular material above which it will gain strength and below which it will lose strength when subjected to rapid deformation.