Why Cosmology Isn't Boring

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Talk given to the Dark Energy Survey Collaboration Meeting, University of Sussex, October 22nd 2014

Transcript of Why Cosmology Isn't Boring

  • 1. Dark Energy SurveyCollaboration MeetingOctober 22nd 2014Why Cosmology isntBoringPeter Coles (MPS)(@telescoper)

2. Dark Energy SurveyCollaboration MeetingOctober 22nd 2014Why the StandardCosmology isntBoringPeter Coles (MPS)(@telescoper) 3. 23 October 2014 4. Precision Cosmologyas we know, there are known knowns;there are things we know we know. We alsoknow there are known unknowns; that is tosay we know there are some things we do notknow. But there are also unknown unknowns-- the ones we don't know we don't know. 5. SAY PRECISIONCOSMOLOGYONE MORE TIME 6. Ingredients of the StandardCosmologyGeneral RelativityCold Dark MatterCosmological ConstantCosmological PrinciplePrimordial Gaussian fluctuationsInflationBaryonsNeutrinosRadiation 7. Questionable Aspects of theStandard CosmologyGeneral RelativityCold Dark MatterCosmological ConstantCosmological PrinciplePrimordial Gaussian fluctuationsInflationBaryonsNeutrinosRadiation 8. CONCORDANCE 9. The Meaning of Inflation (OED)1.The action of inflating or distending with air or gas2.The condition of being inflated with air or gas, orbeing distended or swollen as if with air3.The condition of being puffed up with vanity, prideor baseless notions4.The quality of language or style when it is swollenwith big or pompous words; turgidity, bombast 10. TheoriesBayesian FrequentistObservations 11. Cosmology is a massiveexercise in datacompression...Cosmology is an exercise in data compression.but it is worth looking atthe information that hasbeen thrown away to checkthat it makes sense! 12. The Elephant in the Room 13. Beyond the PowerSpectrum So far what we have discovered islargely based on second-orderstatistics This is fine as long as we dont throwaway important clues ..ie if the fluctuations are statisticallyhomogeneous and istropic, andGaussian.. 14. If tortured sufficiently, datawill confess to almostanythingFred Menger 15. Beware the ProsecutorsFallacy!P(A|M)P(M|A) 16. CMB AnomaliesType I obvious problems with data(e.g. foregrounds)Type II anisotropies and alignments(North-South, Axis of Evil..)Type III localized features, e.g. TheCold SpotType IV Something else (even/oddmultipoles, magnetic fields, ?) 17. Low Quadrupole? 18. Parity Violation? 19. (from Copi et al. 2005) 20. (from Hansen et al. 2004) 21. A. Theres no problem at allwith LCDMB. There are interestingindicationsC. Theres definitelyevidence of new physics 22. The Maximally BoringUniverse? There are many unanswered theoreticalquestions! So far the questions weve asked havebeen the easy ones Now that this boring stuff is out of theway, cosmology will start to getinteresting! Because we now have a better idea whatto ask! 23. BICEP2 24. 23 October 2014 25. 23 October 2014