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On the initial value problem for second order scalar fluctuations in Einstein static

B. Losic·W. G. Unruh
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Abstract

We consider fluctuations in a perfect irrotational fluid coupled to gravity in an Einstein static universe background. We show that the homogeneous linear perturbations of the scalar and metric fluctuations in the Einstein static universe must be present if the second order constraint equations are to be integrable. I.e., the 'linearization stability' constraint forces the presence of these homogeneous modes. Since these linear homogeneous scalar modes are well known to be exponentially unstable, the tactic of neglecting these modes to create a long-lived, almost Einstein universe does not work, even if all higher order (L $>$ 1) modes are dynamically stable.

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B. Losic, W. G. Unruh. 2004-11-22. On the initial value problem for second order scalar fluctuations in Einstein static. https://doi.org/10.1103/physrevd.71.044011

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