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Forecasting the Axiverse

This paper explores the concept of the Axiverse, a theoretical framework that suggests the presence of many ultra-light axions in the universe. It discusses the implications of the Axiverse for cosmology, dark matter, and dark energy, and provides forecasts for future observations. The paper also discusses the standard model, gauge forces, and the strong CP problem.

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Forecasting the Axiverse

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  1. Forecasting the Axiverse David J. E. Marsh, Edward Macaulay, Maxime Trebitsch and Pedro G. Ferreira, arXiv:astro-ph/1110.0502. David J. E. Marsh, Berkeley, 1/12/11 Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 1/35

  2. Outline • Introduction: standard models • The “String Axiverse” • Axions and Cosmology • Forecasts (“Euclid-like”) • Conclusions and outlook Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 2/35

  3. Radiation: The Concordance Model Photons Relativistic species, e.g. massless neutrinos • Ordinary matter: Baryons • Dark sector: Dark matter Dark energy • Initial conditions: … Inflation Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 3/35

  4. Gauge forces: EM, strong and weak forces. • nucleosynthesis, recombination… • Matter: quarks and leptons • baryons, massless neutrinos • Neutrino masses? • Strong CP problem and axions? The Standard Model Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 4/35

  5. Standard model has no candidates. • Cosmology: CDM and a c.c. can fit all data. • Extra relativistic species? • DE equation of state or EDE? • Particle Physics: CDM = WIMP (e.g. LSP). • In addition, need massive neutrinos (observationally) and possibly axions (theoretically). The Dark Sector Komatsu et al (WMAP 7, 2011) Dunkley et al (ACT, 2010) Giunti, arXiv:1106.4479 (2011) Peccei and Quinn, PRL 38,1440 (1977) Dark Matter is multi-component! Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 5/35

  6. “String theory suggests the simultaneous presence of many ultra-light axions, possibly populating each decade of mass down to the Hubble scale, 10-33 eV” Arvanitaki et al PRD 81, 123530 (2010) The Axiverse: what? Figure: Arvanitaki et al Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 6/35

  7. Svrcek and Witten, arXiv:hep-th/0605206 • String theory has extra dimensions: compactify. • Axions are KK zero-modes of antisymmetric tensor fields compactified on closed cycles. The Axiverse: how? • Potentials from non-perturbative physics (D-branes, instantons etc.). Many pseudo Goldstone bosons Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 7/35

  8. Require the QCD axion to solve strong CP: The Axiverse and QCD • SSB at scale fa, then instantons tilt the hat. • The QCD axion must remain light to achieve this. http://www.hep.ph.ic.ac.uk/cms/physics/higgs.html Many axions will remain light Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 8/35

  9. A source of ultra-light scalar dark matter • Scales depend on the action of the instantons: • Canonically normalised axions are weakly coupled The Axiverse in this work (and why) • Instanton action scales with the area of a cycle. • Masses distribute on a log scale: Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 9/35

  10. Sikivie, Physics Today, Dec. ‘96 Interlude • You observe a flat table in a room with a slanted floor. How? • You propose a mechanism to straighten it accurately: gravity. • The required accuracy requires a long arm and heavy weight. • How can you test this? Look for relic oscillations from production. Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 10/35

  11. Well defined measure for abundance. • Fine tuning? • Isocurvature and gravity waves give constraints. • Motivated as dark matter in many different contexts. • Couplings give further constraints. • Axions and inflation. • Monodromy quintessence, BH superradiance, … Comments on Axions Tegmark et al, PRD (2006) Mack and Steinhardt, JCAP (2011) Fox et al, hep-th/0409059 Sikivie, arXiv:1003.2426 Mortsell and Goobar, JCAP (2003) Linde, PLB (1991) Panda et al, arXiv:1011.5877 Arvanitaki and Dubovsky, PRD (2011) Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 11/35

  12. DJEM, PRD (2011) • Coupling to a modulus: Axiverse Extended • Stabilisation in an attractor. • Potential to solve initial conditions problem for axion? • EDE and dark energy dynamics. • Collapsing universe is asymptotic future. Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 12/35

  13. Equations of motion: Ma and Bertschinger, APJ (1995) Hu, APJ (1998) Cosmology of the Axiverse I • Stress energy tensor: Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 13/35

  14. Background Evolution • Different background scaling implies different effects on matter-radiation equality, and hence on the CMB. • Relic density is non-thermal. Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 14/35

  15. WKB approx. gives a scale dependent sound speed: Cosmology of the Axiverse II Hu et al, PRL (2000) Amendola and Barbieri, PLB (2006) • Process analogous to neutrino free-streaming: Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 15/35

  16. DJEM and Ferreira, PRD (2010) • This leads to steps in the matter power spectrum: Axion “Free-Streaming” DJEM and Ferreira, PRD (2010) Eisenstein and Hu, APJ (1997) • Many degeneracies as for massive neutrinos. Hu, Eisenstein, Tegmark, PRL (1998) Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 16/35

  17. Important Scales DJEM et al, arXiv:1110.0502 Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 17/35

  18. Module for CAMB solves field equations and oscillations. • Mass range restricted by this choice. Implementation Amendola and Barbieri, PLB (2006) Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 18/35

  19. DJEM et al, arXiv:1110.0502 Observables: P(k) and BAO • Model for smooth part changes: bias? • Small change in sound horizon from background. Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 19/35

  20. DJEM et al, arXiv:1110.0502 Observables: Growth Rate • Scale dependent growth, degenerate with more CDM. • Unique signal needs large scale measurement. Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 20/35

  21. DJEM et al, arXiv:1110.0502 Observables: Weak Lensing • Convergence power spectrum measures dark matter density directly from galaxy shear. • Window function sets redshift bin: tomography. Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 21/35

  22. Observables: Weak Lensing • Indistinguishable from LCDM in single bin. • Growth amplitude from tomography gives very strong constraints. Hu, PRD (2002) Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 22/35

  23. Observables: CMB • Most effects can be removed due to total degeneracy with horizon size and equality redshift. • Breaks degeneracy with neutrino mass and number. • Constraining power in ISW due to oscillations near recombination: used in checks. • Larger effects in lensing not used because of correlations. Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 23/35

  24. Fisher Matrix forecast for Planck + Euclid. • CMB uses FIsherCodes by Sudeep Das. • GRS and WLT are our own, by Edward and Maxime. Forecasts: Implementation http://www.astro.princeton.edu/~sudeep/fisherCodesDoc Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 24/35

  25. http://sci.esa.int/euclid arXiv:1110.3193 Forecasts: Euclid “The Euclid survey can be thought of as the low-redshift, 3-dimensional analogue and complement to the map of the high redshift Universe provided by ESA’s Planck mission”. Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 25/35

  26. Planck: TT, TE, EE in 100, 143 and 217 GHz. Forecasts: Survey Parameters • Euclid GRS: 15 redshift bins of varying volume. Spectroscopic 43.68 million galaxies at a constant density of: • Euclid WLT: 5 redshift bins, with constant # of sources. Photometric Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 26/35

  27. Forecasts: Fiducial Models • Fixed Hubble: • Test 4 axion masses: Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 27/35

  28. Fiducial cosmology: Forecasts: Fiducial Models • Marginalise over: Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 28/35

  29. DJEM et al, arXiv:1110.0502 • Compare with massive neutrinos: Forecasts: Results Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 29/35

  30. DJEM et al, arXiv:1110.0502 • Strong CMB degeneracies: Forecasts: Results Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 30/35

  31. DJEM et al, arXiv:1110.0502 • Value of combining redshift information: Forecasts: Results GRS alone can constrain 1% at 1 Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 31/35

  32. DJEM et al, arXiv:1110.0502 • Combined results: Forecasts: Results Mass independent constraints Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 32/35

  33. Outlook • Still much work to do for param. estimation. • Fits comparing to specific neutrino models. • Multiple, heavier species: Ly-alpha? • Anharmonic potentials. • Dynamics of extended model. • Isocurvature? DJEM et al, in prep. Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 33/35

  34. Summary Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 34/35

  35. Thank You! Questions? Forecasting the Axiverse, David J. E. Marsh, Berkeley, 1/12/11 35/35

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