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Cosmic Superstrings

Cosmic Superstrings. Strings (or linear defects) appear in many physical systems:. vortex lines in liquid helium. magnetic flux tubes in Type II superconductors. disclination lines in liquid crystals. Could the fundamental strings of superstring theory appear as cosmic strings?. X.

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Cosmic Superstrings

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  1. Cosmic Superstrings

  2. Strings (or linear defects) appear in many physical systems: • vortex lines in liquid helium • magnetic flux tubes in Type II superconductors • disclination lines in liquid crystals

  3. Could the fundamental strings of superstring theory appear as cosmic strings? X superstrings cosmic strings E. Witten (1985): NO!!

  4. Problems, Problems, Problems (pre-1995) • microscopic details make strings unstable! Type I: open strings fragment Heterotic & Type II: closed strings domain walls, • fundamental strings have tension close • to Planck scale, but isotropy of CMB constrains • inflation would dilute away any such relic strings • from Planck scale era

  5. 2nd Superstring Revolution(circa 1995): • M-theory Conjecture: all known string theories are • different solutions of single fundamental theory

  6. Essential ingredients for M-theory conjecture: Different perturbative constructions related by “Dualities” • Dualites: two mathematical descriptions describe • identical physical phenomena “String theory is more than a theory of strings” • D-branes: string theory contains other kinds of • objects extended in 0, 1, 2, . . . dimensions D-particles Dp-branes D-strings D-membranes • NS5-branes, M2-branes, M5-branes

  7. After the 2nd superstring revolution: • More kinds of strings: • fundamental strings, D-strings, • partially wrapped D-, M- or NS5-branes (Dualities may relate these objects)

  8. After the 2nd superstring revolution: • More kinds of strings: • fundamental strings, D-strings, • partially wrapped D-, M- or NS5-branes (Dualities may relate these objects) 2. More “exotic” kinds of compactifications: - large extra dimensions - warped compactifications We should reconsider cosmic superstrings

  9. Strings have Planck scale tension • Strings are diluted away by inflation • Strings are unstable Pre-1995 thinking on cosmic superstrings:

  10. 1. string tension reduced in “exotic” compactifications: in “warped” compactifications, tension is redshifted by internal metric factors Bulk: Throat:

  11. Strings have Planck scale tension • Strings are diluted away by inflation • Strings are unstable Pre-1995 thinking on cosmic superstrings: String tension decoupled from Planck scale

  12. Burgess et al; Jones, Stoica & Tye; Sarangi & Tye 2. Cosmic strings from brane inflation: D1-strings form in D3-D3 annihilation as defects in tachyon field by standard Kibble mechanism Radiation (p,q)-strings D3 D3 Theory contains Dirichlet strings, fundamental strings, and also bound state strings (p,q)-strings

  13. Strings have Planck scale tension • Strings are diluted away by inflation • Strings are unstable Pre-1995 thinking on cosmic superstrings: String tension decoupled from Planck scale Rich network of strings may be generated at end of brane inflation

  14. 3. Many potential sources of instability, e.g., • Breaking on D-branes • Collapsing with domain walls • “Baryon decay” • Tachyon decay But instabilities are model specific!! One can find scenarios where: i) (p,q)-strings are stable ii) only D-strings are stable iii) no strings are stable

  15. Strings have Planck scale tension • Strings are diluted away by inflation • Strings are unstable Pre-1995 thinking on cosmic superstrings: String tension decoupled from Planck scale Rich network of strings may be generated at end of brane inflation Many potential instabilities , but model specific!!

  16. What are the numbers? Producing reasonable inflationary parameters constrains models with warped compactifications: Kachru, Kallosh, Linde, Maldacena, McAlister & Trivedi Similarly for large extra dimensions models: Jones, Stoica & Tye; Sarangi & Tye

  17. Seeing Cosmic Superstrings? There are a number of experimental opportunities to observe cosmic superstrings: a) Gravitational Lensing b) Pulsar Timing c) Cosmic Microwave Background d) Gravitational Radiation

  18. c) Cosmic Microwave Background: cosmic strings give no acoustic peaks! Landriau & Shellard; Pogosian et al Non-gaussianities: Jeong & Smoot Future polarization measurements!

  19. d) Gravitational Radiation: Oscillating loops of string can be very wiggly! Cusps: for an instant in an oscillation – rare Kinks: sharp bends appear every intercommutation – common Both produce beams of gravity waves, but cuspsare much more powerful!!

  20. d) Gravitational Radiation: Gravitational radiation bursts from cusps (and kinks) may be observed by gravity wave observatories: Hanford, WA (Livingston, LA) LIGO LISA

  21. Damour & Vilenkin d) Gravitational Radiation: Gravitational radiation bursts from cusps (and kinks): • LIGO I: • LIGO II: • LISA: LIGO I cusps LIGO II kinks

  22. Conclusions: Modern superstring theory admits scenarios where macroscopic superstrings satisfy: a) small tension (compared to Planck scale) b) copiously produced (after inflation) c) stable (on cosmological timescales) Cosmic Superstrings may present a remarkable astronomical window on the microphysics of superstring theory!!!

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