Detecting Cosmic Superstrings

Transcription

1 Detecting Cosmic Superstrings Mark G. Jackson Fermilab MGJ, N. Jones and J. Polchinski, hep-th th/ MGJ and G. Shiu, hep-th th/0506nnn Rutgers University, 5/17/05

2 Breaking U(1) in Cosmology A field breaking a U(1) symmetry will roll to different minima at different points in the universe

3 Breaking U(1) in Cosmology A field breaking a U(1) symmetry will roll to different minima at different points in the universe Neighboring field values will try to correlate

4 Breaking U(1) in Cosmology A field breaking a U(1) symmetry will roll to different minima at different points in the universe Neighboring field values will try to correlate Will often have trapped winding with unbroken U(1), producing a core of energy

5 Expansion/Reconnection Creates Cosmic String Network At formation After expansion/reconnection Allen and Shellard (1990)

6 The Parameter Gµ G Strings created in a phase transition at T c will have tension µ ~ T 2 c. Gravitational interactions are then characterized by dimensionless parameter Gµ ~ (T( c /M pl ) 2. For GUT strings, T c ~ GeV, M pl pl ~ GeV,, so Gµ G ~ 10-6.

7 Current Bounds on Gµ G Gµ ~ produce observed δt/t and δρ/ρ (Zeldovich 1980, Vilenkin 1981) But produce wrong CMB power spectrum - String contribution < 10% implies Gµ G < 10-6 (Pogosian,, Wyman, Wasserman 2004) Albrecht, Battye, Robinson 1997 WMAP strings data Also ruled out by pulsar bounds: Gµ G < 10-7 (Allen 95; Battye,, Caldwell, Shellard 97; Kaspi,, Taylor, Ryba 94; Lommen,, Backer 01)

8 String Theory Cosmic Strings? First studied by Witten 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 There are now ways of overcoming each of these obstacles, though each is very model- dependent

9 Cosmic Superstring Spectrum F-strings, µ F ~ 1/α (perturbative( perturbative) D-strings, µ D ~ µ F /g s (non-perturbative perturbative) (p,q)) strings, bound states of p F- and q D- strings (non-perturbative perturbative) F D F+D

10 Cosmic Superstring Stability 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 Solution: orientifold to remove axion zero-modes.

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

12 Example: Cosmic Strings from Brane Inflation our brane extra brane 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 inflaton extra antibrane One model of inflation suggests there were extra brane-antibrane antibrane pairs in the early universe, which then annihilated and reheated the universe Dvali, Tye; ; Alexander; Burgess, Majumbdar,, Nolte, Quevedo,, Rajesh, Zhang; Dvali, Shafi, Solganik

13 Warping and Effective Tension Warped models suppress tension by e 2Α, large extra dimensions suppress tension by L p /R ds 2 = e 2A(y ) (η µν dx µ dx ν ) + ds 2 perp(y) T eff = e 2A(IR ) T fun << T fun

14 Warping and Effective Tension Simplest models sets tension at < Gµ G < 10-6 (Tye et al) K 2 LM 2 T (Kachru, Kallosh, Linde, Maldacena, McAllister, Trivedi 2003) have developed a specific model of inflation in string theory which puts tension in the middle of this range

15 Combining Brane Inflation and Warping in K 2 LM 2 T (p,q) strings naturally produced in inflation throat Kachru, Kallosh, Linde and Trivedi; Kachru, Kallosh, Linde, Maldacena, McAllister & Trivedi

16 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. e 2 O-plane brane strings inflationary throat To break the strings must tunnel to one of the other tunnels. This can be very slow, but is very model-dependent dependent (Copeland, Myers, Polchinski 2003)

17 Future Observation: Gravitational Waves QuickTime and a Animation decompressor are needed to see this picture. Primary signal: cusps arising from oscillations Secondary signal: kinks arising from interactions

18 Gravitational Wave Detectors LIGO: online now, Advanced LIGO ~ 2009 Frequency range: 5 Hz f 2 x 10 4 Hz VIRGO: online now Frequency range: 10 Hz f 10 4 Hz LISA: Planned launch date of 2013 Frequency range: 10-5 Hz f 1 Hz

19 LIGO/LISA signals h h cusps α ~ 50Gµ cusps kinks LIGO I Advanced LIGO Damour and Vilenkin 2001 kinks pulsar bound Cosmic strings could be the brightest GW sources, over a wide range of Gµ. Current data: ~ 0.1 LIGO I designyear, perhaps full year in LISA

20 Deficit Angles due to Cosmic Strings Vilenkin 1981 noted that cosmic strings have conical deficit D = 8πGµ 8 and so could be used as a gravitational lens. identify cosmic string earth

21 Observing a Cosmic String via Gravitational Lensing: : 1 Sazhin et al 2003, 2004 have found two adjacent z ~ 0.46 galaxies with identical size, intensity and spectra, known as CSL-1 Point lens gives odd # of images, string lens gives even # Implies Gµ 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)

22 Observing a Cosmic String via Gravitational Lensing: : 2 Q is a well-known system of a quasar being lensed by a galaxy. The two quasar images have a relative delay of 417 days due to path length difference. Schild et al 2004 have reported anomalous periodic brightness fluctuations of 4% in the quasar images The fluctuations have zero time delay, in contrast to the 417-day delay expected if the fluctuations were intrinsic to the quasar. This implies the object responsible for the anomalous lensing is very close to us A star lensing model is clearly ruled out; a rotating cosmic string model of Gµ G ~ 10-6 works very well

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

24 F-F F Reconnection Probability Relate P to forward amplitude via unitarity: P=Σ Construct vertex operators: f f 2 = Im Compute forward scattering amplitude: Take imaginary part: MGJ, Jones, Polchinski 2004

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

26 Effect of Extra Dimensions on P Superstrings still have wavefunctions in compact dimensions 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 / <( X) 2 > 1/2 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: MGJ, Jones, Polchinski 2004

27 Examples of Compactification 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: Averaged over S 3 : Not averaged over S 3 : n large extra dimensions: MGJ, Jones, Polchinski 2004

28 Effect on the Scaling Solution The scaling solution is an attractor solution which assumes the amount of string per Hubble volume is the maximal 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) This should lead to dramatic enhancement of signal:

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

30 Novel Cosmic String Networks (p,q)) networks D3-brane nodes F D F+D Winding beads Matsuda 2004

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