Detecting Cosmic Detecting Cosmic SuperstringsSuperstrings

Mark G. JacksonMark G. JacksonFermilabFermilab

MGJ, N. Jones and J. Polchinski, hep-th/0405229MGJ, N. Jones and J. Polchinski, hep-th/0405229

MGJ and G. Shiu, hep-th/???MGJ and G. Shiu, hep-th/???

MGJ and S. Sethi, hep-th/???MGJ and S. Sethi, hep-th/???

COSMO ‘05, 8/30/05

String Theory Cosmic String Theory Cosmic Strings?Strings?

First studied by First studied by Witten 1985Witten 1985.. Original conclusion was entirely negative: they are Original conclusion was entirely negative: they are

not not producedproduced at the appropriate time in universe at the appropriate time in universe evolution, nor evolution, nor stablestable, nor , nor observableobservable, nor , nor distinguishabledistinguishable!!

Revisited by Revisited by Copeland, Myers and Polchinski 2003 Copeland, Myers and Polchinski 2003 with nonperturbative knowledgewith nonperturbative knowledge

There are now ways of overcoming each of these There are now ways of overcoming each of these obstacles, though each is very model-dependentobstacles, though each is very model-dependent

Cosmic Superstring Cosmic Superstring SpectrumSpectrum

D-strings, D-strings, DD ~ ~ FF//ggss (non-perturbative) (non-perturbative)

F

DF+D

((p,qp,q) strings, bound states of ) strings, bound states of pp F- and F- and qq D- D-

strings (non-perturbative)strings (non-perturbative)

F-strings, F-strings, FF ~ 1/ ~ 1/’ (perturbative)’ (perturbative)

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

SolutionSolution: don’t use type I strings.: don’t use type I strings.

Type II/Heterotic strings are unstable because axion Type II/Heterotic strings are unstable because axion instantons generate “bump” in potential; the extra instantons generate “bump” in potential; the extra energy produces a domain wall, causing quick collapseenergy produces a domain wall, causing quick collapse

SolutionSolution: orientifold to remove axion zero-modes.: orientifold to remove axion zero-modes.

Cosmic Superstring Cosmic Superstring StabilityStability

Orientifolding allows annihilation with image Orientifolding allows annihilation with image string, mimicking monopole pair production.string, mimicking monopole pair production.

SolutionSolution: tunneling rate is highly suppressed for : tunneling rate is highly suppressed for cases of interest.cases of interest.

Strings unstable against breaking on D3-branes.Strings unstable against breaking on D3-branes.

SolutionSolution: |: |pp| ≤ | ≤ M/M/2 stable, and again tunneling 2 stable, and again tunneling suppressed for cases of interest.suppressed for cases of interest.

Cosmic Superstring Cosmic Superstring StabilityStability

m m

(p,q)(p,q) (p-M,q)

D3-brane with M units of RR flux

D3-brane with -M units of RR flux

Example: Cosmic StringsExample: Cosmic Stringsfrom Brane Inflationfrom Brane Inflation

One model of One model of inflation inflation

suggests there suggests there were extra were extra

brane-antibrane brane-antibrane pairs in the early pairs in the early

universe, which universe, which then annihilated then annihilated

and reheated the and reheated the universeuniverse

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

extra brane

extraanti-brane

our brane

Dvali, Tye; Alexander; Dvali, Tye; Alexander; Burgess, Majumbdar, Burgess, Majumbdar, Nolte, Quevedo, Rajesh, Nolte, Quevedo, Rajesh, Zhang; Dvali, Shafi, Zhang; Dvali, Shafi, SolganikSolganik

inflaton

Warping and Effective Warping and Effective TensionTension

Warped models suppress tension by Warped models suppress tension by eelarge extra dimensions suppress large extra dimensions suppress tension by tension by LLpp/R/R

€

ds2 = e2A (y )(η μν dxμdxν ) + ds2perp (y)

€

Teff = e2A (IR )Tfun <<Tfun

Combining Brane Combining Brane Inflation and Warping in Inflation and Warping in

KK22LMLM22TT

Kachru, Kallosh, Linde and Trivedi; Kachru, Kallosh, Linde, Maldacena, McAllister & Trivedi

(p,q) strings naturally produced in inflation throat

1010-12-12 < G < G < 10 < 10-6-6 (Tye et al)(Tye et al)

Stability in KStability in K22LMLM22TT The strings and branes feel a potential due The strings and branes feel a potential due

to the gravitational redshift (warp factor) in to the gravitational redshift (warp factor) in the compact directions. the compact directions.

To break the strings must tunnel to one of To break the strings must tunnel to one of the other tunnels. This can be very slow, the other tunnels. This can be very slow, but is very model-dependentbut is very model-dependent

e

O-plane

brane

strings

inflationarythroat

(Copeland, Myers, Polchinski 2003)(Copeland, Myers, Polchinski 2003)

Future Observation: Future Observation: Gravitational WavesGravitational Waves

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are needed to see this picture.

Primary signal:cusps arising fromoscillations

Secondary signal:kinks arising frominteractions

LIGO/LISA signalsLIGO/LISA signals

~ 50G

LIGO I

Advanced LIGO

cusps kinks

h

Damour and Vilenkin 2001

LISA

cuspskin

ks

h

pulsar bound

Cosmic strings could be the brightest GW sources, over a wide range of G.

Current data: ~ 0.1 LIGO I design-year, perhaps full year in 2005.

Observing a Cosmic Observing a Cosmic StringString

via Gravitational Lensingvia Gravitational Lensing Sazhin et al 2003, 2004Sazhin et al 2003, 2004 have found two adjacent have found two adjacent zz ~ 0.46 galaxies with ~ 0.46 galaxies with identical size, intensity identical size, intensity and spectra, known as and spectra, known as CSL-1CSL-1

Implies GImplies G ~ 4 x 10 ~ 4 x 10-7-7

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

DistinguishingDistinguishingSuper vs Vortex Cosmic Super vs Vortex Cosmic

StringsStringsWhen two strings collide, two things can happen:

reconnection:probability P

nothing:probability 1-P

Gauge theory strings always reconnect for Gauge theory strings always reconnect for v < vv < vcc ((Matzner 1989Matzner 1989).). String theory reconnection is probabilistic (String theory reconnection is probabilistic (Polchinski Polchinski 1988; MGJ, Jones, & Polchinski 20041988; MGJ, Jones, & Polchinski 2004))

Summary of Summary of PP’s’s

F-F: F-F:

MGJ, Jones, Polchinski 2004MGJ, Jones, Polchinski 2004

F-(F-(p,qp,q):):

D-D:D-D:

(Also see: (Also see: Hanany & Hashimoto 2005Hanany & Hashimoto 2005))

Effect of Extra Dimensions Effect of Extra Dimensions on on PP

Superstrings still have wavefunctions in compact Superstrings still have wavefunctions in compact dimensionsdimensions

Zero modes spread out over very small compact Zero modes spread out over very small compact dimensions, producing dimensions, producing PP ~ ~ VVmin min / / VVcompcomp

Could also have wave function localized near potential Could also have wave function localized near potential minimum, producing minimum, producing PP ~ ~ LLmin min / <(/ <(X)X)22>>1/21/2

MGJ, Jones, Polchinski 2004MGJ, Jones, Polchinski 2004

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:

KK22LMLM22T model has compact dimensions of T model has compact dimensions of Klebanov-Strassler type, RKlebanov-Strassler type, R33 x S x S33::

with warp factor (potential) depending on with warp factor (potential) depending on RR33 radial parameter: radial parameter:

nn large extra dimensions: large extra dimensions:

Examples of Examples of CompactificationCompactification

Averaged over S3:

Not averaged over S3:

MGJ, Jones, Polchinski 2004MGJ, Jones, Polchinski 2004

Strings are assumed to interact as much as Strings are assumed to interact as much as allowed by causality, i.e. need ~ 1 interaction per allowed by causality, i.e. need ~ 1 interaction per Hubble timeHubble time

If If P << 1P << 1, strings will need to interact , strings will need to interact ~ 1/P~ 1/P times to ensure one interaction per Hubble time, times to ensure one interaction per Hubble time, so we expect the number of strings per Hubble so we expect the number of strings per Hubble volume to be volume to be N ~ 1/P N ~ 1/P (Damour & Vilenkin 2004) (Damour & Vilenkin 2004)

This should lead to dramatic enhancement of This should lead to dramatic enhancement of signal:signal:

Effect on Gravity Wave Effect on Gravity Wave SignalSignal

This also implies the typical energy density per This also implies the typical energy density per volume is volume is ~ ~ PP-1-1t / tt / t33 ~ ~ / (Pt/ (Pt22). ). But this could also But this could also be computed using be computed using ~ ~ L/LL/L33. Equating these gives. Equating these gives

This has been confirmed numerically (This has been confirmed numerically (Sakellariadou Sakellariadou

20042004) )

Thus string parameters are measurable from Thus string parameters are measurable from observation!observation!

Effect on the Scaling Effect on the Scaling SolutionSolution

€

L ~ Pt

ConclusionConclusion We need cosmic superstrings to beWe need cosmic superstrings to be

ProducedProduced StableStable ObservableObservable DistinguishableDistinguishable

Although not predicted by every Although not predicted by every model, if they exist they have a model, if they exist they have a spectacularspectacular signaturesignature