Abstract
If the equation of state of dark energy is anisotropic there will be additional quadrupole anisotropy in the cosmic microwave background induced by the time-dependent anisotropic stress quantified in terms of . Assuming that the entire amplitude of the observed quadrupole is due to this anisotropy, we conservatively impose a limit of for any value of assuming that . This is considerably tighter than that which comes from supernovae. Stronger limits, up to a factor of 10, are possible for specific values of and . Since we assume this component is uncorrelated with the stochastic component from inflation, we find that both the expectation value and the sample variance are increased. There is no improvement in the likelihood of an anomalously low quadrupole as suggested by previous work on an elliptical universe.
- Received 11 December 2009
DOI:https://doi.org/10.1103/PhysRevD.81.081301
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