Cosmic Superstrings

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Cosmic Superstrings
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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

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

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2nd Superstring Revolution (circa 1995)

• M-theory Conjecture all known string theories
  are
• different solutions of single fundamental theory

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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

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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)
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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
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• Strings have Planck scale tension
• Strings are diluted away by inflation
• Strings are unstable

Pre-1995 thinking on cosmic superstrings
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1. string tension reduced in exotic
compactifications in warped
compactifications, tension is redshifted by
internal metric factors
Bulk
Throat
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• 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
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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
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• 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
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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
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• 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!!
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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
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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
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c) Cosmic Microwave Background
cosmic strings give no acoustic peaks!
Landriau Shellard Pogosian et al
Non-gaussianities
Jeong Smoot
Future polarization measurements!
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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 cusps
are much more powerful!!
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d) Gravitational Radiation
Gravitational radiation bursts from cusps (and
kinks) may be observed by gravity wave
observatories
Hanford, WA
(Livingston, LA)
LIGO
LISA
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Damour Vilenkin
d) Gravitational Radiation
Gravitational radiation bursts from cusps (and
kinks)

• LIGO I
• LIGO II
• LISA

LIGO I
cusps
LIGO II
kinks
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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!!!