Detecting Cosmic Superstrings

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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
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String Theory Cosmic Strings?

• 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!
• 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

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Cosmic Superstring Spectrum
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Cosmic Superstring Stability

• Type I is unstable against decaying into short
  open strings, now interpreted as breaking onto a
  D9-brane
• Solution dont 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.

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Cosmic Superstring Stability

• 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.
• Solution p M/2 stable, and again tunneling
  suppressed for cases of interest.

(p-M,q)
(p,q)
(p,q)
D3-brane with M units of RR flux
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Example Cosmic Stringsfrom Brane Inflation

• One model of inflation suggests there were extra
  brane-antibrane pairs in the early universe,
  which then annihilated and reheated the universe

inflaton
extra anti- brane
extra brane
our brane
Dvali, Tye Alexander Burgess, Majumbdar, Nolte,
Quevedo, Rajesh, Zhang Dvali, Shafi, Solganik
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Warping and Effective Tension

• Warped models suppress tension by e2A, large
  extra dimensions suppress tension by Lp/R

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Combining Brane Inflation and Warping in K2LM2T

• (p,q) strings naturally produced in inflation
  throat
• 10-12 lt Gm lt 10-6 (Tye et al)

• Kachru, Kallosh, Linde and Trivedi Kachru,
  Kallosh, Linde, Maldacena, McAllister Trivedi

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Stability in K2LM2T

• 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

(Copeland, Myers, Polchinski 2003)
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Future Observation Gravitational Waves
Primary signal cusps arising from oscillations
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LIGO/LISA signals
Cosmic strings could be the brightest GW sources,
over a wide range of Gm. Current data 0.1
LIGO I design-year, perhaps full year in 2005.
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Observing a Cosmic Stringvia Gravitational
Lensing

• Implies Gm 4 x 10-7

• They also found 11 more nearly identical pairs,
  consistent with extended nature of string (point
  lens only gives 2 pairs)

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DistinguishingSuper vs Vortex Cosmic Strings
When two strings collide, two things can happen

• Gauge theory strings always reconnect for v lt vc
  
• (Matzner 1989).
• String theory reconnection is probabilistic
  (Polchinski 1988 MGJ, Jones, Polchinski 2004)

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Summary of Ps

• F-F

MGJ, Jones, Polchinski 2004
(Also see Hanany Hashimoto 2005)
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Effect of Extra Dimensions on P

• Superstrings still have wavefunctions in compact
  dimensions
• Zero modes spread out over very small compact
  dimensions, producing P Vmin / Vcomp
• Could also have wave function localized near
  potential minimum, producing P Lmin / lt(DX)2gt1/2

MGJ, Jones, Polchinski 2004
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Examples of Compactification

• K2LM2T model has compact dimensions of
  Klebanov-Strassler type, R3 x S3
• with warp factor (potential) depending on R3
  radial parameter
• n large extra dimensions

Averaged over S3
Not averaged over S3
MGJ, Jones, Polchinski 2004
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Effect on Gravity Wave Signal

• Strings are assumed to interact as much as
  allowed by causality, i.e. need 1 interaction
  per Hubble time
• If P ltlt 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

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Effect on the Scaling Solution

• This also implies the typical energy density per
  volume is r P-1mt / t3 m / (Pt2). But this
  could also be computed using r mL/L3. Equating
  these gives
• This has been confirmed numerically
  (Sakellariadou 2004)
• Thus string parameters are measurable from
  observation!

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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