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Primordial Gravitational WavesPowerPoint Presentation

Primordial Gravitational Waves

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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
- Shape of potential
- Small-scale physics …

- Does inflation predict directly detectable gravitational waves?

- Is it worth all that ?

Primordial Gravitational Waves

Inflation predicts a *small*

stochastic background of GW,

but how small?

- Energy spectrum

The search for tensor modes

WMAP3 + SDSS :

r < 0.2 (95%)

at k = 0.002 Mpc-1[Peiris, Easther]

Planck, BICEP, CLOVER, QUIET etc.

What does inflation predict?

But V(Φ) is unknown!

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]

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]

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

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…]

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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