A free scalar field with Lagrangian density(adsbygoogle = window.adsbygoogle || []).push({});

$${\cal L}=\frac{1}{2}g^{\mu\nu}\partial_{\mu}\phi\partial_{\nu}\phi$$

has the energy momentum tensor with the equation of state ##p=\rho##, i.e. ##w=1##. The Lagrangian density above is a very natural Lagrangian, yet the equation of state ##w=1## seems not to be considered in cosmology. Why is it not considered?

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# A Equation of state w=1

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