1 / 51

Fitting the luminosity data from type Ia supernovae by means of the cosmic defect theory

Fitting the luminosity data from type Ia supernovae by means of the cosmic defect theory. Angelo Tartaglia DIFIS – Politecnico and INFN Torino, Italy. Plan of the talk. Starting point and motivation Outline of the Cosmic Defect theory Fit of the observational data

jory
Download Presentation

Fitting the luminosity data from type Ia supernovae by means of the cosmic defect theory

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Fitting the luminosity data from type Ia supernovae by means of the cosmic defect theory Angelo Tartaglia DIFIS – Politecnico and INFN Torino, Italy Taipei - Hualien 29 May 2008

  2. Plan of the talk • Starting point and motivation • Outline of the Cosmic Defect theory • Fit of the observational data • Defects and Vector Theories: general Lagrangians • Open problems Taipei - Hualien 29 May 2008

  3. The accelerated expansion (luminosity data of SnIa’s) Taipei - Hualien 29 May 2008

  4. The power spectrum of CMB k=0 Taipei - Hualien 29 May 2008

  5. Presently agreed expansion Taipei - Hualien 29 May 2008

  6. Einstein equations Spacetime geometry “Matter” Why is Λ on the left? Taipei - Hualien 29 May 2008

  7. Give up GR and look for another theory Something missing • Inflation • Gravity in clusters and galaxies • Accelerated expansion There is something missing Introduce the missing entities Modify GR Taipei - Hualien 29 May 2008

  8. Add “matter” components Accept a four- (N-) dimentional spacetime manifold Perfect fluid Isotropy and homogeneity Taipei - Hualien 29 May 2008

  9. Λ Cold Dark Matter • Simplest and most effective model for the universe; however: • “matter” must be 7 times what we “see” (~30% of the source); • Λ corresponds to 70% of the souce but … what is Λ? Taipei - Hualien 29 May 2008

  10. Trying a new approach: The Cosmic Defect theory • Motivation, besides the simple fitting of the data: • describing the large scale behaviour of the universe in terms of intrinsic properties of a four-dimensional continuum; • interpreting space-time as Einstein’s GR ether Taipei - Hualien 29 May 2008

  11. Strain in a continuumN-dimensional “sheet” Strain induced by boundary conditions Taipei - Hualien 29 May 2008

  12. A defect Internal “spontaneous” strain state Taipei - Hualien 29 May 2008

  13. Four-dimensional point defect Taipei - Hualien 29 May 2008

  14. Geometry, elasticity and defects Taipei - Hualien 29 May 2008

  15. In a strained medium each point is in one to one correspondence with points in the unstrained state Displacement Intrinsic coordinates Extrinsic coord. The new situation is diffeomorphic to the old one ξ is a function of x Taipei - Hualien 29 May 2008

  16. Strain tensor Induced metric Taipei - Hualien 29 May 2008

  17. “Radial” displacement field (space isotropy and homogeneity) Taipei - Hualien 29 May 2008

  18. The line element Unperturbed Strained Taipei - Hualien 29 May 2008

  19. A Robertson-Walker universe Taipei - Hualien 29 May 2008

  20. How can we choose a Lagrangian expressing the presence of the defect? Start from the phase space of a Robertson-Walker universe and look around for similar phase spaces Taipei - Hualien 29 May 2008

  21. Inertial expansion Accelerated expansion Decelerated expansion Free motion Driving force Braking force Phase space analogy FRW universe Point particle Taipei - Hualien 29 May 2008

  22. A simple classical problem Motion of a point massive particle in a viscous medium Taipei - Hualien 29 May 2008

  23. Invariant formulation of the same problem Taipei - Hualien 29 May 2008

  24. Spacetime“Dissipative” action integral • Same structure as in the classical simple case • The “viscous” properties of space-time arecontainedin the vector field Taipei - Hualien 29 May 2008

  25. Robertson Walker symmetry Isotropy and homogeneity in 3 dimensions RW line element The symmetry is induced by the presence of a “defect” Taipei - Hualien 29 May 2008

  26. Impose the 4-isotropy around the origin and use cosmic time as the “radial” coordinate Taipei - Hualien 29 May 2008

  27. Symmetry and application of the minimal action principle do not commute Defect means Symmetry first Taipei - Hualien 29 May 2008

  28. Non-trivial if Lagrangian Taipei - Hualien 29 May 2008

  29. Divergence free vector Taipei - Hualien 29 May 2008

  30. The expansion rate(a and time in units of Q) Choose the + sign Taipei - Hualien 29 May 2008

  31. Accelerated expansion Asymptoticstop Expansion rate Taipei - Hualien 29 May 2008

  32. Acceleration Inflation Expansion versus cosmic time Taipei - Hualien 29 May 2008

  33. Fitting the data from SnIa Taipei - Hualien 29 May 2008

  34. The distance modulus Taipei - Hualien 29 May 2008

  35. The energy function for the CD theory Taipei - Hualien 29 May 2008

  36. Multicomponent cosmic fluid Equation of state Conservation law Expansion rate Taipei - Hualien 29 May 2008

  37. Fitting the data (192 SnIa) Taipei - Hualien 29 May 2008

  38. Reduced 2 of the fits 2 = 1.029 ΛCDM 2 = 1.092 CD Taipei - Hualien 29 May 2008

  39. The Hubble parameter H0 = (62.8 ± 1.7) km/sMpc Most models ~64 km/sMpc Observation ~75 km/sMpc Taipei - Hualien 29 May 2008

  40. Weaknesses and open problems • Fitting the SnIa luminosity data with a logarithmic function and two parameters is “too easy” • The inflation is too strong and long lasting (troubles with nucleosynthesis and formation of structures) • The exponential in the action integral is a poweful multiplier, but it should be weakened Taipei - Hualien 29 May 2008

  41. The null divergence condition should be a consequence of the singularity in correspondence of the defect, rather than a formal constraint imposed on the vector. • Once it has been induced, the γ vector has its own dynamics and energy content which must be taken into account Taipei - Hualien 29 May 2008

  42. General Lagrangian treatment (non-exponential coupling) Non-minimal coupling Taipei - Hualien 29 May 2008

  43. The equations for a and  Taipei - Hualien 29 May 2008

  44. Special or trivial solutions Matter dominated FRW Taipei - Hualien 29 May 2008

  45. Correspondences • Bimetric theories: “pre-shaped container” • Vector-tensor theories • Curvature fluid Taipei - Hualien 29 May 2008

  46. Final remarks The CD theory provides a consistent physical interpretation of space-time giving a heuristic tool to move across the Lagrangian “engineering” mostly driven by the formal search for the desired result. This conceptual framework looks promising Taipei - Hualien 29 May 2008

  47. A. Tartaglia, M. Capone, Int. Jour. Mod. Phys. D, 17, 275-299 (2008) A. Tartaglia, N. Radicella, Phys. Rev. D, 76, 083501 (2007) A. Tartaglia, M. Capone, V. Cardone, N. Radicella, arXiv:0801.1921, to appear on Int. Jour. Mod. Phys. D Taipei - Hualien 29 May 2008

  48. Thank you Taipei - Hualien 29 May 2008

  49. Why SnIa? Accreting white dwarf Supernova explosion Tycho Brahé 1572 (Chandra’s image) Taipei - Hualien 29 May 2008

  50. SnIa is a good candle Stable light curve Taipei - Hualien 29 May 2008

More Related