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Primordial Gravitational Waves

Primordial Gravitational Waves. and Black Holes:. Is it worth the search?. Sirichai Chongchitnan (with George Efstathiou) Institute of Astronomy University of Cambridge 25th September 2006. Questions. What will we learn about inflation? e.g. Energy scale

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Primordial Gravitational Waves

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  1. Primordial Gravitational Waves and Black Holes: Is it worth the search? • Sirichai Chongchitnan • (with George Efstathiou) • Institute of Astronomy • University of Cambridge • 25th September 2006

  2. Questions • What will we learn about inflation? • e.g. Energy scale • Shape of potential • Small-scale physics … • Does inflation predict directly detectable gravitational waves? • Is it worth all that ?

  3. Primordial Gravitational Waves Inflation predicts a *small* stochastic background of GW, but how small? • Energy spectrum

  4. The search for tensor modes WMAP3 + SDSS : r < 0.2 (95%) at k = 0.002 Mpc-1[Peiris, Easther] Planck, BICEP, CLOVER, QUIET etc.

  5. Direct detections Joseph Weber 1969 Nautilus (Rome)

  6. What does inflation predict? But V(Φ) is unknown!

  7. Hamilton-Jacobi Formalism Evolve “flow equations” till inflation ends ≡a potential V(Φ) Specify initial Taylor coefficients of H(Φ) [Hoffman&Turner’01] [Kinney’02] ✱H(Φ) determines ωgw directly ✱Dynamics well-understood [Chongchitnan and Efstathiou PRD’05]

  8. Generic constraint onωgw At f ≃ 0.1 - 1 Hz, for all models of single field inflation [Chongchitnan and Efstathiou PRD’06] 0.92 ≲ns≲1.06 -1.04≲≲ 0.03 [Viel et al’04] ,[Seljak’05]

  9. High ωgwmodels (r= few x 10-3) Directly detectable GW ⇔ “pathological” potential

  10. Energy scale of inflation Future GW experiments will probe a tiny range of energy scales [Efstathiou and Chongchitnan Prog.Theor.Phys.’06] e.g. , r ≃ 10-10 , V1/4 ≃ 1014 GeV

  11. Primordial Black Holes • Formed by great overdensities during inflation • Slow-roll underestimate PBH abundance. • Precise calculations needed • “Absence” of PBH rules out very pathological models. • [Chongchitnan and Efstathiou, astroph/0610…]

  12. Conclusions • Large scales, Planck/CLOVER can rule out large-field (chaotic) inflation models • Small scales, BBO/DECIGO will improve limit of energy scale of inflation by only a few. Will test only pathological models. • Worth looking at other signatures of inflation : Non-gaussianity from multi-field inflation or distinctive signatures of cosmic strings from brane inflation.

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