Cosmic Superstrings

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

E. Witten (1985): NO!!

Could the fundamental strings of superstringtheory appear as cosmic strings?

X

cosmic stringssuperstrings

• 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

21 1 SFT

3fun 10TGN

5miccos 10TGN

Problems, Problems, Problems (pre-1995)

• microscopic details make strings unstable!Type I: open strings fragment

Heterotic & Type II: closed strings domain walls,

2nd Superstring Revolution (circa 1995):

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

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-strings D-membranes

Dp-branes

Different perturbative constructions related by “Dualities”

“String theory is more than a theory of strings”

• NS5-branes, M2-branes, M5-branes

After the 2nd superstring revolution:

1.More kinds of strings: fundamental strings, D-strings,

partially wrapped D-, M- or NS5-branes(Dualities may relate these objects)

After the 2nd 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

Pre-1995 thinking on cosmic superstrings:

1. Strings have Planck scale tension

2. Strings are diluted away by inflation

3.Strings are unstable

1. string tension reduced in “exotic” compactifications:

in “warped” compactifications, tension is redshifted by internal metric factors

funT

effT

funfunA

eff TTeT 02

)(2)(22 ydsdxdxeds yA

12 Ae

102 Ae

Bulk:

Throat:

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

2. Cosmic strings from brane inflation:

D3 D3

D1-strings form in D3-D3 annihilation as defectsin tachyon field by standard Kibble mechanism

Burgess et al; Jones, Stoica & Tye; Sarangi & Tye

(p,q)-strings

Radiation

2221),( SFqp gqpTT

Theory contains Dirichlet strings, fundamental strings,and also bound state strings (p,q)-strings

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 generatedat end of brane inflation

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!!

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 generatedat end of brane inflation

Many potential instabilities, but model specific!!

Similarly for large extra dimensions models:

612 1010 TGN

Jones, Stoica & Tye; Sarangi & Tye

Kachru, Kallosh, Linde, Maldacena, McAlister & Trivedi

910 1010 TGN

What are the numbers?

Producing reasonable inflationary parameters constrainsmodels with warped compactifications:

Seeing Cosmic Superstrings?

There are a number of experimental opportunitiesto observe cosmic superstrings:

a) Gravitational Lensing

b) Pulsar Timing

c) Cosmic Microwave Background

d) Gravitational Radiation

7107 TGNLandriau & Shellard;Pogosian et al

cosmicstringsgive noacousticpeaks!

Non-gaussianities: 7103 TGN Jeong & Smoot

c) Cosmic Microwave Background:

Future polarization measurements!

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

1x

Oscillating loops of string can be very wiggly!

d) Gravitational Radiation:

Gravitational radiation bursts from cusps (and kinks)may be observed by gravity wave observatories:

(Livingston, LA)Hanford, WA

LIGO

d) Gravitational Radiation:

LISA

Gravitational radiation bursts from cusps (and kinks):

Damour & Vilenkin

• LIGO I:

• LIGO II:

• LISA:

1110TGN

1010TGN

1310TGN

TGN50log

LIGO I

LIGO II

kinks

cusps

d) Gravitational Radiation:

Conclusions:

Cosmic Superstrings may present a remarkable astronomical window on the

microphysics of superstring theory!!!

Modern superstring theory admits scenarioswhere macroscopic superstrings satisfy:

a) small tension (compared to Planck scale)b) copiously produced (after inflation)c) stable (on cosmological timescales)