The Fall and Rise of Cosmic Strings

1. The Fall and Rise of Cosmic Strings The Fall and Rise of Cosmic Strings Cosmology 2005: A Reality Check Copenhagen, December 16th 2005 (Credit: DAMTP, Cambridge) Aurelien Fraisse Princeton University – Department of Astrophysical Sciences

2. The Fall and Rise of Cosmic Strings Formation of Topological Defects The Universe steadily cools down. Expect phase transitions to happen u v (Credit: A. Gangui) 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

3. The Fall and Rise of Cosmic Strings Cosmic Strings – Basic Properties 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. Pogosian & Vachaspati (astro-ph/9903361)

4. The Fall and Rise of Cosmic Strings Where WMAP hurts… Wyman et al. (astro-ph/0503364)

5. The Fall and Rise of Cosmic Strings Is this the end? 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) Only show that strings alone cannot explain the CMB anisotropies

6. The Fall and Rise of Cosmic Strings Hybrid Inflation Inflation and Formation of defects at the end of the inflationary phase Clobs = (1-a) ClLCDM + a Clstrings Minimal description: a, wb, wm, h, t, ns, A (s8) Complete MCMC necessary Best fit: a = 4% 0% allowed at 2-s More than 22% rejected at 3-s (Gm)BF = 5.6 x 10-8 (Gm)max = 3.1 x 10-7 Compatible with HI predictions (Fraisse, astro-ph/0503402)

7. The Fall and Rise of Cosmic Strings We’re safe, but for how long? Minimum value of Gm constrained by theory: Gm < 10-11 difficult Upcoming CMB data will be highly constraining WMAP + Planck ACT 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 Gm ~ 10-12 !

8. The Fall and Rise of Cosmic Strings A Cosmic String lensing? A CS distorts the surrounding space-time. Candidate: CSL-1 (cf., e.g., astro-ph/0406516) Pair of identical galaxies at z ~ 0.46. Would imply Gm > 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.

9. 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 Gm 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…