Vasiliki A. Mitsou. IFIC Valencia TAUP International Conference on Topics in Astroparticle and Underground Physics

Transcription

1 Vasiliki A. Mitsou IFIC Valencia TAUP 2009 International Conference on Topics in Astroparticle and Underground Physics Rome, Italy, 1-5 July 2009

2 Dark energy models CDM Super-horizon CDM (SHCDM) [Kolb, Matarrese, Notari, Riotto] Liouville (off-equilibrium) string Q-Cosmology [Diamandis, Ellis, Georgalas, Lahanas, Mavromatos, Nanopoulos] Astrophysical observations of universe acceleration type Ia supernovae differential galaxy ages baryon acoustic oscillations (BAO) Other probes of Supercritical String Cosmology (SSC) Quantum Gravity foam - high energy photons distant sources Implications for dark matter LHC signatures Ellis, Mavromatos, VAM, Nanopoulos, Astrop Phys 27 (2007) 185 [astro-ph/ ] Mavromatos, VAM,, Astrop Phys 29 (2008) 442 [astro-ph/ ]

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4 Dark energy is a cosmological constant, not changing through space and time All cosmological observations agree with CDM predictions so far 120 orders of magnitude less than QFT predictions for vacuum energy cosmological constant problem Why M now? coincidence problem Hubble expansion rate: ( ) = H 0 Ω Λ + Ω M ( 1+ z) 3 + Ω k ( 1+ z) 2 H z [ ] 1 2 k : curvature term k = M Λ M P 4

5 No dark energy assumed Observed effects (CMB, SNe, etc) induced by cosmological perturbations larger than the present Hubble radius 1/H 0 (super-horizon) (x,t): gravitational potential Depends on one parameter: l0 ds 2 = dt 2 + a 2 ( t)e 2Ψ( x,t ) δ ij dx i dx j specified by primordial inflation physics Ψ ( t) a( t)ψ 0, 1+ z = a 1 e a 1 ( )Ψ 0 H( t) = H 0 ( a 3 2 a 1 2 Ψ 0 ), 1 Ψ 0 Kolb et al, New J Phys 8 (2006) 322 astro-ph/ ] Kolb et al, hep-th/

6 SSC: theoretical framework largely phenomenological treating non-equilibrium string (cosmological) models of the Universe Departure from equilibrium cosmically catastrofic events (Big-Bang, brane collisions, ) quantum space-time foam Formal properties central charge surplus relaxation phenomena Liouville mode: world-sheet `time-like coordinate field extra time coordinate in target space Modifications in Einstein equations time-dependent dilaton field Ellis, Mavromatos, Nanopoulos, A Liouville String Aproach to Microscopic Time and Cosmology arxiv:hep-th/ , and references therein Mavromatos, Nanopoulos, The MAGIC of SSC and how it affects LHC, arxiv: [hep-ph, and references therein]

7 Relaxing-to-zero (dilaton) dark energy density, non-critical string contributions off-shell equations of motion for dilaton, graviton No cosmological constant asymptotic states/s-matrix may be well defined (strings) Parameterisation of Hubble expansion rate: ( ) = H 0 Ω 3 ( 1+ z) 3 + Ω δ ( 1+ z) δ + Ω 2 ( 1+ z) 2 H z [ ] 1 2, Ω 2 =1 Ω 3 Ω δ, δ 4 valid in certain models only for z O(10) (analytic in Ellis et al, Astrop Phys 27 (2007) 185 [astro-ph/ ]) could be more complicated (numerical analyses: Diamandis et al, PLB 642 (2006) 179 [hep-th/ ]) also valid in brane cosmology models Mixed-origin contributions to i from dark matter and dark energy Important: 3 could be negative! (1+z) 2 scaling distinct from curvature! Exotic scaling of dark matter different from (1+z) 3 non-trivial equation of state, w e 0

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9 Defines luminosity distance d L know L, measure F Standard candles Intensity µ 5logd L Type Ia supernovae (SN Ia): similar explosion with nearly the same peak intensity Standard Candles d L ( 1+ z) d z H z ( ) Comparison of SN Ia redshifts and magnitudes provides direct measurement of the changing rate of expansion of the universe z 0

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11 Davis dataset All three models fit equally well the SN data Rather tight constraints for model parameters Q-cosmology: 3 < 0 evidence of negative-energy dust Model Parameters 2 2 /dof CDM flat M = ± CDM curved ( M, ) = (0.33, 0.85) SHCDM 0 = ± Q-cosmology ( = 4) ( 3, 4 ) = (-2.8 ± 0.5, 0.86 ± 0.22)

12 Differential ages of distant galaxies (z 2) determine H(z) H(z) = 1 1+ z Simon et al, PRD 71 (2005) [astro-ph/ ] Due to large errors, data loosely constrain models Slightly worse 2 for Q-cosmology SHCDM: galaxies-favoured 0 more than 2 away from SN-favoured one: 0 = ± 0.07 Lookback time vs. redshift test can be applied for same data dz dt GDDS & archival data t L (z) z 0 d z (1+ z )H( z ) Model Parameters 2 2 /dof CDM flat M = 0.27 ± CDM curved ( M, ) = (0.2±0.3, 0.7±0.6) SHCDM 0 = ± Q-cosmology ( = 4) ( 3, 4 ) = (-1.0 ± 1.0, 0.2 ± 0.3)

13 Davis dataset In both cases, the goodness-of-fit depends weakly on Case = 3 is of no relevance to Q-cosmology, corresponding to a generic matter-dominated Universe with no cosmological constant Combination with other data may constrain Baryon Acoustic Oscillations

14 Coupling of photons and baryons in the early Universe imprints features in both CMB (WMAP) and matter power spectra (galaxy surveys) Common scale: sound horizon (~150 Mpc) standard ruler! Angular-diameter distance d A d A 1 1+ z Dilation scale D V D V (z) = D 2 M (z) z 0 d z H z ( ) cz H(z) σ detection A independent of H 0 A D V (z BAO ) A = ± Ω M H 0 2 cz BAO SDSS galaxy survey Eisenstein et al. ApJ 633 (2005) 560 [astro-ph/ ] 46,700 LRGs over 3816 deg 2 and 0.16 < z < 0.47 z BAO = 0.35

15 Observable B independent of M and H 0 B H 0 c D V (z BAO ) = E(z) H(z) /H 0 z BAO 0 dz E(z) 2 z BAO E(z BAO ) 1 3 CDM constraints for SN, galaxy ages and BAO compatible (as expected) SHCDM: prediction for B compatible with measured value marginally agrees with SNfavoured value model excluded by incompatibilty between SN and galaxy-ages data model prediction

16 SN & BAO almost overlap both d L and D V sensitive to: z d z 0 H( z ) Parameter restricted to Matter densities vary: highly correlated! Global fit (on updated data) necessary to get more precise results

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18 In SSC, D-particle defects in spacetime lead to Quantum Gravity `foam point-like stringy defects and the interactions of strings with them leads to non-critical strings contribution to Q-cosmology-like situations modified dispersion relations delays in the propagation of photons Fermi collab, Science 323: ,2009 Probes: high energy -rays from distant sources gamma-ray bursts, active galactic nuclei, pulsars, Fermi, MAGIC, HESS, e.g. GRB C current limit (from HESS): E QG > GeV 2 nd peak is moving toward later times as the energy increases clear signature of spectral evolution source effects to be understood

19 WMAP3 constraint on neutralino relic density SSC-allowed ordinary cosmologyallowed

20 CDM may not be the only model to fit the SN data Off-equilibrium (Liouville) string Q-Cosmology equally good fits with negative dust-like energy densities and exotic dark-matter scaling Encouraging results for SSC so far prompt further studies (theoretical & observational) new SN Ia datasets (Union, Constitution, ) comparison with CMB (WMAP) data prediction for H(z) at z~1000 needed lookback time of galaxy clusters, GRBs, Other classes of SSC models can be probed with highenergy photons Effect on LHC SUSY discovery channels