1. Detecting Cosmic Superstrings Mark G. Jackson Fermilab MGJ, N. Jones and J. Polchinski, hep-th/0405229 MGJ and G. Shiu, hep-th/??? MGJ and S. Sethi, hep-th/??? COSMO ‘05, 8/30/05

2. String Theory Cosmic Strings? First studied by Witten 1985. First studied by Witten 1985. Original conclusion was entirely negative: they are not produced at the appropriate time in universe evolution, nor stable, nor observable, nor distinguishable! Original conclusion was entirely negative: they are not produced at the appropriate time in universe evolution, nor stable, nor observable, nor distinguishable! Revisited by Copeland, Myers and Polchinski 2003 with nonperturbative knowledge Revisited by Copeland, Myers and Polchinski 2003 with nonperturbative knowledge There are now ways of overcoming each of these obstacles, though each is very model- dependent There are now ways of overcoming each of these obstacles, though each is very model- dependent

3. Cosmic Superstring Spectrum D-strings,  D ~  F  /g s (non-perturbative) D-strings,  D ~  F  /g s (non-perturbative) F D F+D (p,q) strings, bound states of p F- and q D- (p,q) strings, bound states of p F- and q D- strings (non-perturbative) F-strings,  F ~ 1/  ’ (perturbative) F-strings,  F ~ 1/  ’ (perturbative)

4. Type I is unstable against decaying into short open strings, now interpreted as breaking onto a D9-brane Type I is unstable against decaying into short open strings, now interpreted as breaking onto a D9-brane Solution: don’t use type I strings. Type II/Heterotic strings are unstable because axion instantons generate “bump” in potential; the extra energy produces a domain wall, causing quick collapse Type II/Heterotic strings are unstable because axion instantons generate “bump” in potential; the extra energy produces a domain wall, causing quick collapse Solution: orientifold to remove axion zero-modes. Cosmic Superstring Stability

5. Orientifolding allows annihilation with image string, mimicking monopole pair production. Orientifolding allows annihilation with image string, mimicking monopole pair production. Solution: tunneling rate is highly suppressed for cases of interest. Strings unstable against breaking on D3-branes. Strings unstable against breaking on D3-branes. Solution: |p| ≤ M/2 stable, and again tunneling suppressed for cases of interest. Cosmic Superstring Stability mm (p,q) (p-M,q) D3-brane with M units of RR flux D3-brane with -M units of RR flux

6. Example: Cosmic Strings from Brane Inflation One model of inflation suggests there were extra brane-antibrane pairs in the early universe, which then annihilated and reheated the universe D-strings can be thought of as the topological defects in the tachyon field describing this annihilation, produced by Kibble mechanism. F-strings are produced via confinement of remaining gauge symmetry extra brane extra anti- brane our brane Dvali, Tye; Alexander; Burgess, Majumbdar, Nolte, Quevedo, Rajesh, Zhang; Dvali, Shafi, Solganik inflaton

7. Warping and Effective Tension Warped models suppress tension by e   large extra dimensions suppress tension by L p /R Warped models suppress tension by e   large extra dimensions suppress tension by L p /R

8. Combining Brane Inflation and Warping in K 2 LM 2 T Kachru, Kallosh, Linde and Trivedi; Kachru, Kallosh, Linde, Maldacena, McAllister & Trivedi (p,q) strings naturally produced in inflation throat 10 -12 < G  < 10 -6 (Tye et al)

9. Stability in K 2 LM 2 T The strings and branes feel a potential due to the gravitational redshift (warp factor) in the compact directions. The strings and branes feel a potential due to the gravitational redshift (warp factor) in the compact directions. To break the strings must tunnel to one of the other tunnels. This can be very slow, but is very model-dependent To break the strings must tunnel to one of the other tunnels. This can be very slow, but is very model-dependent e  O-plane brane strings inflationary throat (Copeland, Myers, Polchinski 2003)

10. Future Observation: Gravitational Waves Primary signal: cusps arising from oscillations Secondary signal: kinks arising from interactions

11. LIGO/LISA signals  ~ 50G  LIGO I Advanced LIGO cusps kinks h Damour and Vilenkin 2001 LISA cusps kinks h pulsar bound Cosmic strings could be the brightest GW sources, over a wide range of G . Current data: ~ 0.1 LIGO I design- year, perhaps full year in 2005.

12. Observing a Cosmic String via Gravitational Lensing Sazhin et al 2003, 2004 have found two adjacent z ~ 0.46 galaxies with identical size, intensity and spectra, known as CSL-1 Sazhin et al 2003, 2004 have found two adjacent z ~ 0.46 galaxies with identical size, intensity and spectra, known as CSL-1 Implies G  ~ 4 x 10 -7 Implies G  ~ 4 x 10 -7 They also found 11 more nearly identical pairs, consistent with extended nature of string (point lens only gives ~ 2 pairs) They also found 11 more nearly identical pairs, consistent with extended nature of string (point lens only gives ~ 2 pairs)

13. Distinguishing Super vs Vortex Cosmic Strings When two strings collide, two things can happen: reconnection: probability P nothing: probability 1-P Gauge theory strings always reconnect for v < v c Gauge theory strings always reconnect for v < v c (Matzner 1989). String theory reconnection is probabilistic (Polchinski 1988; MGJ, Jones, & Polchinski 2004) String theory reconnection is probabilistic (Polchinski 1988; MGJ, Jones, & Polchinski 2004)

14. Summary of P’s F-F: F-F: MGJ, Jones, Polchinski 2004 F-(p,q): F-(p,q): D-D: D-D: (Also see: Hanany & Hashimoto 2005)

15. Effect of Extra Dimensions on P Superstrings still have wavefunctions in compact dimensions Superstrings still have wavefunctions in compact dimensions Zero modes spread out over very small compact dimensions, producing P ~ V min / V comp Zero modes spread out over very small compact dimensions, producing P ~ V min / V comp Could also have wave function localized near potential minimum, producing P ~ L min / 1/2 Could also have wave function localized near potential minimum, producing P ~ L min / 1/2 MGJ, Jones, Polchinski 2004 Expand potential near minima: Each string mode feels a harmonic oscillator potential, and the effective width of each mode can be summed: The effective width can then be calculated given parameters:

16. K 2 LM 2 T model has compact dimensions of Klebanov-Strassler type, R 3 x S 3 : K 2 LM 2 T model has compact dimensions of Klebanov-Strassler type, R 3 x S 3 : with warp factor (potential) depending on R 3 radial parameter: n large extra dimensions: n large extra dimensions: Examples of Compactification Averaged over S 3 : Not averaged over S 3 : MGJ, Jones, Polchinski 2004

17. Strings are assumed to interact as much as allowed by causality, i.e. need ~ 1 interaction per Hubble time Strings are assumed to interact as much as allowed by causality, i.e. need ~ 1 interaction per Hubble time If P << 1, strings will need to interact ~ 1/P times to ensure one interaction per Hubble time, so we expect the number of strings per Hubble volume to be N ~ 1/P (Damour & Vilenkin 2004) If P << 1, strings will need to interact ~ 1/P times to ensure one interaction per Hubble time, so we expect the number of strings per Hubble volume to be N ~ 1/P (Damour & Vilenkin 2004) This should lead to dramatic enhancement of signal: This should lead to dramatic enhancement of signal: Effect on Gravity Wave Signal

18. This also implies the typical energy density per volume is  ~ P -1  t / t 3 ~  / (Pt 2 ). But this could also be computed using  ~  L/L 3. Equating these gives This also implies the typical energy density per volume is  ~ P -1  t / t 3 ~  / (Pt 2 ). But this could also be computed using  ~  L/L 3. Equating these gives This has been confirmed numerically (Sakellariadou 2004) This has been confirmed numerically (Sakellariadou 2004) Thus string parameters are measurable from observation! Thus string parameters are measurable from observation! Effect on the Scaling Solution

19. Conclusion We need cosmic superstrings to be We need cosmic superstrings to be Produced Produced Stable Stable Observable Observable Distinguishable Distinguishable Although not predicted by every model, if they exist they have a spectacular signature Although not predicted by every model, if they exist they have a spectacular signature