### Observational signature of sign of cosmological perturbation

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**April 20 2015**Hello,

As far as I know, all observational evidence for cosmological perturbations comes from the CMB power spectrum, which goes like [tex]\delta^2[/tex]. Are there any observational signatures that would indicate the sign of [tex]\delta[/tex]?

Thanks for any help,

Kevin

As far as I know, all observational evidence for cosmological perturbations comes from the CMB power spectrum, which goes like [tex]\delta^2[/tex]. Are there any observational signatures that would indicate the sign of [tex]\delta[/tex]?

Thanks for any help,

Kevin