cosmic superstrings. strings (or linear defects) appear in many physical systems: vortex lines in...
Post on 18-Dec-2015
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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)