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Observing Cosmic Superstrings

Observing Cosmic Superstrings. or, How Gravity Wave Observers Could Prove String Theory. Mark Wyman Cornell University. With Levon Pogosian, Ira Wasserman, Henry Tye, and Ben Shlaer Pogosian, Tye, Wasserman, MW, Phys. Rev. D68 (2003) 023506 (hep-th/0304188)

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Observing Cosmic Superstrings

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  1. Observing Cosmic Superstrings or, How Gravity Wave Observers Could Prove String Theory Mark Wyman Cornell 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

  2. First, Some History …

  3. I. Inflation Horizon 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, r ~ M4 Horizon Problem:

  4. I. Inflation Horizon and Flatness Problems • Spatial curvature • 1 - W = 0 unstable fixed point Flatness Problem:

  5. I. Inflation The 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?)

  6. 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)

  7. Cosmic Strings Gm:Key Dimensionless Parameter G = Newton’s constant ( = c = 1) m= string tension Gm ~ string tension in Planck units ~ gravitational coupling of string = size of metric perturbation.

  8. How do Strings Interact? nothing: probability 1-P reconnection: probability P P = 1 for non-string-theory cosmic strings Simulations suggest that approximately

  9. String Network Evolution: Scaling Simplest One-Scale Model: Energy Lost in Loops (Kibble) But since this is hard to picture ….

  10. In the Matter- dominated Era Movie by Paul Shellard

  11. Brane Inflation:New Source for Cosmic Strings? (Tye and Sarangi 2002, Jones, Stoica, and Tye 2002) • 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 extra anti- brane extra brane

  12. Wilkinson Microwave Anisotropy Probe Sloan Digital Sky Survey Strings Strings Strings vs. Data: Review Alone: Strings FAIL (Albrect, Battye, & Robinson, PRL 79 (1997) 4736) Strings ARE allowed at a subdominant level: Question: how much? (Bouchet, Peter, Riazuelo, Sakellariadou, PRD 65 (2002) 021301)

  13. 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?!

  14. Our Modeling Parameters • Standard Cosmological Parameters: As, ns, h, WBh2, WMh2, t • 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”, a)

  15. 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) 1311 SDSS: 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

  16. This is not simple! 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) 1311 SDSS: 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

  17. WMAP and SDSS Bounds: Summary

  18. WMAP and SDSS Bounds: Summary WMAP and SDSS Bounds: Summary

  19. 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

  20. WMAP and SDSS Bounds:Direct Limits on String Tension • Fix parameters at WMAP values • Define

  21. String Wiggliness • String Gravity: • No Useful Limit string wiggliness

  22. 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

  23. String B-Mode in Context Plot by Bruce Winstein

  24. GW Background: Pulsar Timing String Loops Make Lots of Gravity Waves! Lommen, Backer ‘KTR’ ‘01 Data; Vilenkin / Damour ‘04 Analysis: (But … Somewhat Model Dependent)

  25. Gravity Wave Burstsfrom Cusps and Kinks

  26. LIGO I h Advanced LIGO cusps kinks Damour and Vilenkin 2001 a ~ 50Gm h cusps kinks LISA Gravity Waves from Cosmic Strings Cosmic strings could be the very bright GW sources, over a wide range of Gm cosmological. bounds Old Calculations: P = 1 (100% interaction probability)

  27. But in String Theory, P < 1 … most pessimistic Bursts from cusps LIGO, LIGO 2, …. Analysis / Plot from Damour and Vilenkin, Phys. Rev. D71 (2005) 063510, hep-th/0410222

  28. And for LISA: most pessimistic

  29. 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 …

  30. String Cusps But finite size / self-interaction effects MAY change this …. red: zero width approx. Movie by Ken Olum

  31. Gravitational Lensingby a String

  32. Conical Spacetime (c = 1): (Gm = string mass per unit length ~1022 g/cm) Deficit Angle

  33. CSL-1: A Detection? (Sazhin et al, 2002) z = 0.46 Separation ~ 20 Kpc ~ 1.9 ” --> Gm ~ few x 10-7

  34. To be tested in February … What we’d love to see

  35. Cosmic Superstrings: How Are They Different? • Multi-m 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)

  36. Distinctive Gravitational Lensing Distinctive, but probably very rare with B. Shlaer, hep-th/0509177

  37. New Interaction Physics (Note: Hide Dynamics / Cosmology in conformal time,  • 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 Rules From Jackson, Jones, & Polchinski (2004)

  38. N+1 Length Scales, One Velocity • 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.b.: for F = 0

  39. N+1 Length Scales, One Velocity • 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)

  40. Possible Catastrophes • Low P + reactions: leads to frustration (over-density, string domination) • Low F: many tensions go to scaling … A Multi-Tension UV Catastrophe:

  41. Networks DO Scale convergence test Conformal time Cosmological scale factor, a

  42. Few Tensions are Populated N( Tension

  43. Few Tensions are Populated (0,1) (1,0) (1,1) N( Tension

  44. Conclusions • Cosmic String power: ~10% or less Tension 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 …

  45. Filling Out the Model … When F = 0 … (no inter-string interactions)

  46. Filling Out the Model … When F = 0 … (no inter-string interactions)

  47. String Theory:New Source for Cosmic Strings? (Tye and Sarangi 2002, Jones, Stoica, and Tye 2002) • 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

  48. What Kind of Strings can be a subdominant contribution to Structure Formation Bouchet et al, PR D65 (2002) 21301; Pogosian et al, D68 (2003) 023506 (hep-th/0304188)

  49. WMAP dta strings Albrecht, Battye, Robinson 1997 WMAP data II. Old-Style Cosmic Strings GUT Strings Alone Cannot Account for Structure Formation, CMB Power Spectra Shapes

  50. II. Cosmic Strings Data do allow strings as a subdominant contribution -- Gm < 10-6 But where do we get lighter strings? Bouchet et al, PR D65 (2002) 21301; Pogosian et al, D68 (2003) 023506 (hep-th/0304188)

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