Observing Cosmic Superstrings

Observing Cosmic Superstrings

Mark WymanCornell University

With Levon Pogosian, Ira Wasserman, Henry Tye, and Ben Shlaer

Pogosian, Tye, Wasserman, MW, Phys. Rev. D68 (2003) 023506 (hep-th/0304188)Pogosian, MW, Wasserman, JCAP 09 (2004) 008 (astro-ph/0403268)

MW, Pogosian, Wasserman, Phys. Rev. D72 (2005) 023513 (astro-ph/0503364)Tye, Wasserman, MW, Phys. Rev. D71 (2005) 103508 (astro-ph/0503506)

Shlaer and MW, hep-th/0509177

or, How Gravity Wave Observers

Could Prove String Theory

First, Some History …

I. InflationHorizon and Flatness Problems

• Spatial Scale L today: fraction H0 of “horizon”

• Expansion -> fraction HaL = (Ha/H0) H0L at an earlier time

• Standard Cosmology: Ha decreases with time. Extrapolate back to large scale, M: T ~ M, ~ M4

Horizon Problem:

I. InflationHorizon and Flatness Problems

• Spatial curvature

• 1 - = 0 unstable fixed point

Flatness Problem:

I. InflationThe Solution!

• Ha increased by at least 1029 M/MP during a “pre-Big Bang” epoch --> (Horizon scale today) < (Horizon scale before inflation)

• Expansion flattens the universe, so k -> 0 naturally

• At the end of Inflation, Universe reheats, standard Big-Bang cosmology begins.

• Needed: Very flat “Inflaton” Potential (Fine Tuning?)

II. Cosmic Strings

Kibble Mechanism for Symmetry Breaking:

Regions Larger than H-1 Are Out of Causal Contact!

Cosmic String Defect for U(1) Symmetry

(Fig. From Gangui)

Cosmic Strings

G = Newton’s constant ( = c = 1) = string tension

G ~ string tension in Planck units ~ gravitational coupling of string = size of

metric perturbation.

G Key Dimensionless Parameter

How do Strings Interact?

reconnection:probability P

nothing:probability P

Simulations suggest that approximately

P = 1 for non-string-theorycosmic strings

String Network Evolution: Scaling

But since this is hard to picture ….

Simplest One-Scale Model: Energy Lost in Loops (Kibble)

In theMatter-dominatedEra

Movie byPaulShellard

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Brane Inflation:New Source for Cosmic Strings?

• Annihilation of Inflating Branes Can Produce Strings (Actual 1-D Objects or “Wrapped” Higher-D Objects)

• Kibble Mechanism Applies --> But Not in Compact Dimensions (R < H-1) (or more complicated explanations!)

• Brane Dynamics Exclude Domain Walls and Monopoles; Allow Only Strings (Since 3 - 2 = 1)

• Predicts: few x • Not Ruled Out; Potentially Detectable

(Tye and Sarangi 2002, Jones, Stoica, and Tye 2002)

extra brane

extraanti-brane

Wilkinson Microwave Anisotropy Probe

Strings

Sloan Digital Sky SurveyStrings

Strings vs. Data: Review

Alone: Strings FAIL

Strings ARE allowedat a subdominant level:

Question: how much?

(Albrect, Battye, & Robinson, PRL 79 (1997) 4736)

(Bouchet, Peter, Riazuelo, Sakellariadou, PRD 65 (2002) 021301)

Cosmic String Observables:

• Cosmological Limits already in Place:– Precision CMB Observation Limits– Pulsar Timing

• Possible Direct Windows:– Gravity Waves:

Possible LIGO and LISA sources!

– Gravitational Lensing: One Observed Already?!

Our Modeling Parameters• Standard Cosmological Parameters: As, ns, h, Bh2, Mh2,

• Cosmic String Model “Weight”

• Incoherently add String and Adiabatic Power Spectra:

• Vary 7 Parameters using Markov Chain Monte Carlo(+ overall P(k) normalization and “string wiggliness”,

)

Method• Compute Adiabatic Cl’s with CMBWarp

• Compute String CL’s and string & adiabatic P(k)’s with a modified form of CMBFAST

• Nonlinear P(k) fitting with Halofit• Incoherently add String and Adiabatic

contributions • Use WMAP and SDSS Likelihood Functions

with MCMC to find PDFs

CMBWarp: Jimenez et al, PR D70 (2004) 023005 (astro-ph/0404237)Halofit: Smith et al MNRAS 341 (2003) 1311SDSS: Tegmark et al, PR D69 (2004) 103501 (astro-ph/0310723)WMAP: Verde et al, ApJ Supp. 148 (2003) 135 (astro-ph/0302217)Strings: Gangui et al PR D64 (2001) 43001; Pogosian et al, PR D60 (1999) 83504

Method• Compute Adiabatic Cl’s with CMBWarp

• Compute String CL’s and string & adiabatic P(k)’s with a modified form of CMBFAST

• Nonlinear P(k) fitting with Halofit• Incoherently add String and Adiabatic

contributions • Use WMAP and SDSS Likelihood Functions

with MCMC to find PDFs

CMBWarp: Jimenez et al, PR D70 (2004) 023005 (astro-ph/0404237)Halofit: Smith et al MNRAS 341 (2003) 1311SDSS: Tegmark et al, PR D69 (2004) 103501 (astro-ph/0310723)WMAP: Verde et al, ApJ Supp. 148 (2003) 135 (astro-ph/0302217)Strings: Gangui et al PR D64 (2001) 43001; Pogosian et al, PR D60 (1999) 83504

This is not simple!

WMAP and SDSS Bounds: Summary

WMAP and SDSS Bounds: Summary

WMAP and SDSS Bounds: Summary

WMAP and SDSS Bounds:Overall String Power

• Usual Parameters: basically unchanged

• CS fractional power f < 0.14 (95% c.l.)

• also: “test” of adiabatic model

WMAP and SDSS Bounds:Direct Limits on String Tension

• Fix parameters at WMAP values

• Define

• String Gravity:

• No Useful Limit

String Wiggliness

string wiggliness

B-Mode Polarization

• Odd parity: vector, tensor, and lensing E to B

• Adiabatic: Tensor mode fraction, r = 0.1 in graph

• Strings: f = 0.1 in graph; 2 different alpha values

String B-Mode in Context

Plot by Bruce Winstein

GW Background: Pulsar Timing

Lommen, Backer ‘KTR’ ‘01 Data;Vilenkin / Damour ‘04 Analysis:

String Loops Make Lots of Gravity Waves!

(But … Somewhat Model Dependent)

Gravity Wave Burstsfrom Cusps and Kinks

Gravity Waves from Cosmic Strings

~ 50G

LIGO I

Advanced LIGO

cusps kinks

h

Damour and Vilenkin 2001

LISA

cuspskin

ks

h

cosmological.bounds

Cosmic strings could be the very bright GW sources, over a wide range of G

Old Calculations:P = 1(100% interactionprobability)

Bursts from cusps

Analysis / Plot from Damour and Vilenkin, Phys. Rev. D71 (2005) 063510, hep-th/0410222

LIGO, LIGO 2, ….

But in String Theory, P < 1 …

most pessimistic

And for LISA:

most pessimistic

String Cusps

Typically, several times per oscillation a cusp will form somewhere on a cosmic string (Turok 1984).

For zero-width strings, the instantaneous velocity of the tip approaches c …

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String Cusps

But finite size / self-interaction effects MAY change this ….

Movie by Ken Olum

red: zero width approx.

Gravitational Lensing

by a String

Conical Spacetime (c = 1): (G = string mass per unit length ~1022

g/cm)

Deficit Angle

CSL-1: A Detection?

z = 0.46

Separation ~ 20 Kpc ~ 1.9 ”

(Sazhin et al, 2002)

--> G ~ few x 10-7

To be tested in February …

What we’d love to see

• Multi- networks: F, D, (p,q) bound states

• p F-strings + q D-strings = (p,q) string

•Scaling? Tension Distribution?? (MW, Wasserman, Tye, astro-ph/0503506)

Cosmic Superstrings: How Are They Different?

Distinctive Gravitational Lensing

Distinctive, but probably very rare

with B. Shlaer, hep-th/0509177

New Interaction Physics

Interaction Rules:• p and q must be coprime to be stable• (k,0) and (0,k) strings decay instantly

Become k (1,0) or (0,1) strings• All interactions lose energy

(Note: Hide Dynamics / Cosmology in conformal time,

Rules From Jackson, Jones, & Polchinski (2004)

• Multiple tensions:• L, v evolved as in Two Scale Model

• Densities evolve via …– Dilution (2H) and straightening – Self-interaction– Reactions and Breakup as in previous slide

N+1 Length Scales, One Velocity

n.b.: for F = 0

• Multiple tensions:• L, v evolved as in Two Scale Model

• Densities evolve via …– Dilution (2H) and straightening – Self-interaction– Reactions and Breakup as in previous slide

– P: self-interaction parameter; F: inter-string-interaction parameter (massive simplification of collision physics)

N+1 Length Scales, One Velocity

Possible Catastrophes

• Low P + reactions: leads to frustration (over-density, string domination)

• Low F: many tensions go to scaling …

A Multi-Tension UV Catastrophe:

Networks DO Scale

convergencetest

Cosmological scale factor, a

Conformal time

Few Tensions are Populated

N(

Tension

Few Tensions are Populated

N(

Tension

(0,1) (1,0) (1,1)

Conclusions

• Cosmic String power: ~10% or lessTension Limit: G < (few) x 10-7

• Cusps (and Kinks?) COULD be a major LIGO / LISA GW Source

• (p,q) Network interpretation:– Few String tensions: scaling: coherence?

• Gravitational Lensing? We’ll see in February …

Filling Out the Model …

When F = 0 … (no inter-string interactions)

Filling Out the Model …

When F = 0 … (no inter-string interactions)

String Theory:New Source for Cosmic Strings?

• Annihilation of Inflating Branes Can Produce Strings (Actual 1-D Objects or “Wrapped” Higher-D Objects)

• Kibble Mechanism Applies --> But Not in Compact Dimensions (R < H-1)

• Brane Dynamics Exclude Domain Walls and Monopoles; Allow Only Strings (Since 3 - 2 = 1)

• Predicts: few x • Not Ruled Out; Potentially Detectable

(Tye and Sarangi 2002, Jones, Stoica, and Tye 2002)

What Kind of

Strings can be a subdominant contribution to Structure FormationBouchet et al, PR D65 (2002) 21301; Pogosian et al, D68 (2003) 023506 (hep-th/0304188)

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II. Old-Style Cosmic Strings

WMAP dta

stringsAlbrecht, Battye, Robinson 1997

WMAP data

GUT Strings Alone Cannot Account forStructure Formation, CMB Power Spectra Shapes

II. Cosmic Strings

Data do allow strings as a subdominant contribution -- G

But where do we get lighter strings?Bouchet et al, PR D65 (2002) 21301; Pogosian et al, D68 (2003) 023506 (hep-th/0304188)

String Theory: Brane Inflation

• Early-universe D-Brane collisions can successfully model inflation

• Brane attraction can be weak = inflationary potential

• Brane collision may provide natural model for reheating

Cosmic Superstrings: How Are They Different?

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• Multi- networks: D,F, (p,q)

• Intercommutation Probability P < 1? (Sakellariadou 2004:

• Scaling Without Intercommutation? (MW, Wasserman, Tye, In preparation)

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String Theory to the Rescue ….

Are They Detectable?Vilenkin & Damour 2001, 2004

Maybe …