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

4. 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 Problems, Problems, Problems (pre-1995) microscopic details make strings unstable! Type I: open strings fragment Heterotic & Type II: closed strings domain walls,

5. 2 nd 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: Dualites: two mathematical descriptions describe identical physical phenomena D-branes: string theory contains other kinds of objects extended in 0, 1, 2,... dimensions D-particles D-stringsD-membranes Dp-branes Different perturbative constructions related by “Dualities” “String theory is more than a theory of strings” NS5-branes, M2-branes, M5-branes

7. After the 2 nd superstring revolution: 1.More kinds of strings: fundamental strings, D-strings, partially wrapped D-, M- or NS5-branes (Dualities may relate these objects)

8. After the 2 nd superstring revolution: 1.More kinds of strings: fundamental strings, D-strings, partially wrapped D-, M- or NS5-branes 2. More “exotic” kinds of compactifications: - large extra dimensions - warped compactifications (Dualities may relate these objects) We should reconsider cosmic superstrings

9. Pre-1995 thinking on cosmic superstrings: 1. Strings have Planck scale tension 2. Strings are diluted away by inflation 3.Strings are unstable

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

11. Pre-1995 thinking on cosmic superstrings: 1. Strings have Planck scale tension 2. Strings are diluted away by inflation 3.Strings are unstable String tension decoupled from Planck scale

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

13. Pre-1995 thinking on cosmic superstrings: 1. Strings have Planck scale tension 2. Strings are diluted away by inflation 3.Strings are unstable 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., a) Breaking on D-branes b) Collapsing with domain walls c) “Baryon decay” d) Tachyon decay One can find scenarios where: i) (p,q)-strings are stable ii) only D-strings are stable iii) no strings are stable But instabilities are model specific!!

15. Pre-1995 thinking on cosmic superstrings: 1. Strings have Planck scale tension 2. Strings are diluted away by inflation 3.Strings are unstable 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. Similarly for large extra dimensions models: Jones, Stoica & Tye; Sarangi & Tye Kachru, Kallosh, Linde, Maldacena, McAlister & Trivedi What are the numbers? Producing reasonable inflationary parameters constrains models with warped compactifications:

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

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

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

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

22. Conclusions: Cosmic Superstrings may present a remarkable astronomical window on the microphysics of superstring theory!!! 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)