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The Fall and Rise of Cosmic Strings

Aurelien Fraisse Princeton University – Department of Astrophysical Sciences

Cosmology 2005: A Reality Check

The Fall and Rise of Cosmic Strings

Copenhagen, December 16th 2005

(Credit: DAMTP, Cambridge)

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Formation of Topological Defects

The Fall and Rise of Cosmic Strings

The Universe steadily cools down.

Expect phase transitions to happen

Spontaneous symmetry breaking

Two causally disconnected areas in the sky can be in two different states

of minimal energy.

Between them: potential barrier

Topological defects

(Credit: A. Gangui)

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The Fall and Rise of Cosmic Strings

1-D topological defects

Can be produced by a U(1) SSB

Radius ~ 3 trillion times smaller than the radius of

H1

Mass ~ 10 miles of string is about the mass of the Earth

Induce fluctuations in the CMB

Power spectrum has a single bump but is

otherwise featureless.

Cosmic Strings – Basic Properties

Pogosian & Vachaspati (astro-ph/9903361)

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The Fall and Rise of Cosmic Strings

Wyman et al. (astro-ph/0503364)

Where WMAP hurts…

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The Fall and Rise of Cosmic Strings

Would be dangerous for all GUTs…

G -> … -> SU(3)C x SU(2)L x U(1)Y

If G = SU(8), SU(9), SO(10), SO(14) or E6(NTL), formation of CS unavoidable

If G = E6(TL), formation of CD in 80% to 98% of acceptable schemes

G = SU(6) or SU(7) incompatible with proton lifetime measurements

(Sakellariadou, hep-th/0510227)

Is this the end?

Only show that strings alone cannot explain the CMB anisotropies

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The Fall and Rise of Cosmic Strings

Inflation and Formation of defects at the end of the inflationary phase

Clobs = (1-) Cl

CDM + Clstrings

Minimal description: , b, m, h, , ns, A (8)

Complete MCMC necessary

Hybrid Inflation

Best fit: = 4%

0% allowed at 2-

More than 22% rejected at 3-

(G)BF = 5.6 x 10-8

(G)max = 3.1 x 10-7

Compatible with HI predictions

(Fraisse, astro-ph/0503402)

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The Fall and Rise of Cosmic Strings

Minimum value of G constrained by theory: G < 10-11 difficult

Upcoming CMB data will be highly constraining

We’re safe, but for how long?

WMAP + PlanckACT

Damour & Vilenkin (’01 & ’04)

Network of CS loops among which 10% have cusps would produce bursts of GWs detectable by LISA and LIGO down to G ~ 10-12 !

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The Fall and Rise of Cosmic Strings

A CS distorts the surrounding space-time.

A Cosmic String lensing?

Candidate: CSL-1 (cf., e.g., astro-ph/0406516)

Pair of identical galaxies at z ~ 0.46.

Would imply G > 4 x 107, and v > 0.96 c (unlikely)

Theoretical loopholes to make it work (cf. ‘Heavy strings’, hep-ph/0508272)

HST time allotted to observe CSL-1.

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The Fall and Rise of Cosmic Strings

Conclusions

Cosmic strings properties begin to be highly constrained, close to the minimum level authorized by theory. They are however not ruled out.

Difficult to imagine how to construct SUSY GUTs without them.

Upper bounds on G could go down by several orders of magnitude in the coming years, in particular with ACT and other very small scales observations of the CMB. However, as of today, we do not have the

theoretical tools to set constraints using measurements at these scales.

CSL-1 is unlikely to be a CS lensing, but stay tuned…