The anisotropic universe: A reality or fluke?



During the last decade, a strikingly successful cosmological concordance model has been established. With only six free parameters, nearly all observables, comprising millions of data points, may be fitted with outstanding precision. However, in this beautiful picture a few "blemishes" have turned up, apparently not consistent with the standard model: While the model predicts that the universe is isotropic (i.e., looks the same in all directions) and homogeneous (i.e., the statistical properties are the same everywhere), subtle hints of the contrary are now seen. For instance, peculiar preferred directions and correlations are observed in the cosmic microwave background; some studies considering nearby galaxies suggest the existence of anomalous large-scale cosmic flows; a study of distant quasars hints towards unexpected large-scale correlations. All of these reports are individually highly intriguing, and together they hint toward a more complicated and interesting universe than previously imagined -- but none of the reports can be considered decisive. One major obstacle in many cases has been the relatively poor data quality.


This is currently about to change, as the next generation of new and far more powerful experiments are coming online. Of special interest to us are Planck, an ESA-funded CMB satellite currently taking data; QUIET, a ground-based CMB polarization experiment located in Chile; and various large-scale structure (LSS) data sets, such as the SDSS and 2dF surveys, and in the future Euclid, a galaxy survey satellite also funded by ESA. By combining the world’s best data from both CMB and LSS measurements, we will in this ERC funded project attempt to settle this question: Is our universe really anisotropic? Or are these recent claims only the results of systematic errors or statistical flukes? If the claims turn out to hold against this tide of new and high-quality data, then cosmology as a whole may need to be re-written.


  1. "A search for concentric circles in the 7-year WMAP temperature sky maps" , I. K. Wehus and H. K. Eriksen, 2011, ApJ, 733, L29

  2. "Bayesian noise estimation for non-ideal CMB experiments", I. K. Wehus, S. K. Næss and H. K. Eriksen, 2011, ApJS, submitted,  2011


This project is funded by an ERC Starting Grant (StG2010-257080) for a total of €1.5M over five years.


Tags: Cosmology, statistical properties, computational methods
Published Feb. 28, 2011 10:44 AM - Last modified Aug. 4, 2020 3:13 PM


Hans Kristian Eriksen


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