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Journal Article

#### Isotropic Solutions of the Einstein-Liouville Equations

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##### Fulltext (public)

336788.pdf

(Publisher version), 419KB

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##### Citation

Ehlers, J., Geren, P., & Sachs, R. K. (1968). Isotropic Solutions of the Einstein-Liouville
Equations.* Journal of Mathematical Physics,* *9*(9), 1344-1349.
doi:10.1063/1.1664720.

Cite as: http://hdl.handle.net/11858/00-001M-0000-0013-5EFE-8

##### Abstract

The gravitational field generated by a gas whose one-particle distribution function obeys the Liouville equation is examined under the following assumptions: First, the distribution is locally isotropic in momentum space with respect to some world-velocity field; second, if the particles have rest-mass zero, the gas is irrotational. It is shown that the model is then either stationary or a Robertson-Walker model. The time dependence of the radius in the Robertson-Walker models is given in terms of integrals containing the distribution function.