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30 YEARS OF COSMIC STRINGS

30 YEARS OF COSMIC STRINGS. Alex Vilenkin. Tufts Institute of Cosmology. 30 YEARS OF COSMIC STRINGS. String evolution. FOCUS ON:. Detection (bounds). 30 YEARS OF COSMIC STRINGS. LEAVE OUT:. Superconducting strings Vortons Semilocal strings String formation Strings in GUTs

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30 YEARS OF COSMIC STRINGS

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  1. 30 YEARS OF COSMIC STRINGS Alex Vilenkin Tufts Institute of Cosmology

  2. 30 YEARS OF COSMIC STRINGS String evolution FOCUS ON: Detection (bounds)

  3. 30 YEARS OF COSMIC STRINGS LEAVE OUT: Superconducting strings Vortons Semilocal strings String formation Strings in GUTs Strings in condensed matter …

  4. Cosmic super- strings! Strings are seeds of galaxies! Strings are dead! A BRIEF HISTORY Publications per year Kibble 1976

  5. OLD STRING EVOLUTION SCENARIO Kibble (1976), A.V. (1981) • Distance between strings: • Loop sizes: • Loops decay by gravitational radiation: Mass per unit length of string

  6. THE FIRST COSMIC STRING REVOLUTION

  7. High-resolution simulations: the loops are tiny (below the resolution) rad. matter Small-scale wiggles Bennett & Bouchet (1990) Allen & Shellard (1990) Loop sizes are set by the scale of wiggles.

  8. SCENARIOS: is determined by gravitational back-reaction: Bennett & Bouchet (1990) (“standard model”) Siemens & Olum (2001) Siemens, Olum & A.V. (2002) No scaling: Vincent, Hindmarsh & Sakellariadou (1997) Observational predictions are sensitive to !

  9. THE SECOND COSMIC STRING REVOLUTION (still in progress!)

  10. Small-scale wiggles and loops are resolved! Ringeval, Sakellariadou & Bouchet (2005): Most of the energy goes Into loops with . Requires a cutoff. Shellard & Martins (2005): Loop formation on scales . Radiation era Olum & Vanchurin (2006): Scaling peak in loop production develops at after a long transient regime.

  11. Flat-space exact simulation Vanchurin, Olum & A.V. (2005) after a long transient regime.

  12. The picture that seems to emerge is close to the old string scenario: (?) Broad distribution of loops and small-scale wiggles.

  13. Analytic models: Kibble (1985) Bennett (1986) Copeland, Kibble & Austin (1992) Martins & Shellard (1996) Copeland, Kibble & Steer (1998) Polchinski & Rocha (2006) To reach full understanding, we will need to combine numerical and analytic techniques.

  14. COSMIC SUPERSTRINGS Witten (1985) Sarangi & Tye (2002) Majumdar & A. Davis (2002) F, D and FD strings; FD networks. Copeland, Myers & Polchinski (2004) Dvali & A.V. (2004) Metastable, but the lifetime can be >> 1010 yrs. In models of brane inflation: . Jones, Stoica & Tye (2003) [Similar range in hybrid inflation GUT models] Jeannerot & Postma (2005) Reconnection probability may be small: . Jackson, Jones & Polchinski (2004)

  15. How does affect string evolution? Simple argument suggests Numerical evidence is inconclusive. Sakellariadou & A.V. (1990) Sakellariadou (2005) Avgoustidis & Shellard (2006) But in any case, for p << 1 there is a large number of strings per Hubble volume. Direct observational test of string theory.

  16. EVOLUTION OF FD-NETWORKS Scaling: Vachaspati & A.V. (1987) McGraw (1998) Tye, Wasserman & Wyman (2005) Simple models depends on energy dissipation. Goldstone radiation Spergel & Pen (1997) Copeland & Saffin (2005) Hindmarsh & Saffin (2006) Global string network simulations If the dominant energy loss is gravitational radiation: String domination

  17. Gauge strings Urrestilla U(1)xU(1) Loop production? Scaling:

  18. OBSERVATIONAL BOUNDS

  19. STRING SIGHTINGS: Cowie & Hu (1987) Sazhin et. al. (2003) Schild et. al. (2004)

  20. GRAVITATIONAL RADIATION Stochastic GW background & GW bursts from cusps. Comparable power in bursts and in low harmonics. Vachaspati & A.V. (1984) Hogan & Rees (1984) Caldwell & Allen (1992) Battye, Caldwell & Shellard (1996) … Bursts may be detectable for . Damour & A.V. (2000,2005) Better for p << 1. Siemens et. al. (2006) Hogan (2006) LIGO search is underway!

  21. BOUNDS FROM PULSAR OBSERVATIONS 8 yrs: Kaspi, Taylor & Ryba (1994) 17 yrs: Lommen (2002) Hogan (2006) (disputed) PTA: Jenet et. al. (2006) (Pulsar Timing Array) Full PTA (20 pulsars for 5 yrs)

  22. Implications of large loops Nucleosynthesis bound: Vanchurin, Olum & A.V. (2005) Reionization: loops seed early galaxy formation. Olum & A.V. (2006)

  23. CMB BOUNDS CMB anisotropies Pogosian, Wasserman & Wyman (2006) CMB polarization B-type polarization due to vector perturbations induced by strings. may be detectable. Seljak & Slosar (2006)

  24. Bad news: GUT-scale strings are ruled out. We are not likely to detect strings through gravitational lensing or CMB anisotropies. Constraint is much weaker for global strings: Good news: strings can be detected well below the GUT scale. Gravitational waves, CMB polarization

  25. CONCLUSIONS A new generation of string simulations is underway. Strong indications of loop scaling; (?) important observational implications. The strongest present bound on strings: (PTA) The most promising detection methods: pulsar timing, GW bursts, CMB polarization. May get to in ~ 5 yrs. The field is as vibrant as ever!

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