W. Kinney - Scale-Invariant Perturbations: is Inflation the only Way?
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W. Kinney - Scale-Invariant Perturbations: is Inflation the only Way?

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The SEENET-MTP Workshop BW2011

The SEENET-MTP Workshop BW2011
Particle Physics from TeV to Plank Scale
28 August – 1 September 2011, Donji Milanovac, Serbia

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    W. Kinney - Scale-Invariant Perturbations: is Inflation the only Way? W. Kinney - Scale-Invariant Perturbations: is Inflation the only Way? Presentation Transcript

    • Inflation … Or What? Will Kinney Seenet­MTP Workshop Balkan Summer Institute, Donji Milanovac  31 August 2011  
    • CMB: Basic Properties Adiabatic density perturbations Superhorizon correlations Gaussian statistics Near scale­invariance over a factor of 1000 in wavelength Q: What does this really tell us?   
    • Generation of Perturbations Horizon Mode freezing   
    • Generation of Perturbations Comoving horizon: Decelerating Expansion: Accelerating Expansion: Key ingredient for generation of perturbations:  shrinking horizon   
    • The Comoving Horizon in Inflation Decelerating Accelerating   
    • The Comoving Horizon in Inflation   
    • Mode Exit and Re­entry re­entry classical exit quantum   
    • Larger Scales Exit Earlier   
    • Superhorizon Perturbations   
    • The Horizon Is Not The Horizon The Hubble length is not the causal horizon in inflation. Mode freezing has absolutely nothing to do with causality.   
    • The Horizon Is Not The Horizon In general, the Hubble length is not even the freezeout horizon: Scale invariance and freezeout:   
    • Is Inflation the Only Way? Comoving Horizon  (constant equation of state): Decelerating Expansion: Accelerating Expansion: Duality:    (Boyle, et al., hep­th/0403026)
    • The Comoving Hubble Horizon in Inflation Decelerating Accelerating   
    • The Comoving Hubble Horizon in Bouncing Cosmology Expansion Bounce Contraction   
    • The Cyclic Dual to Slow Roll Slow Roll   
    • The Cyclic Dual to Slow Roll Slow Roll   
    • The Cyclic Dual to Slow Roll Slow Roll Dual­Slow Roll Quasi­static contraction   
    • Perturbations Slow Roll Dual­Slow Roll  (WHK, Moradinezhad Dizgah, arXiv:1007.0753)  
    • Ekpyrosis: Problems Shrinking proper Hubble length:  blue spectra Instabilities: growing mode Negative potential Singular bounce Name sounds like a skin disease Buchbinder, Khoury & Ovru, PRD 76, 123503 (2007) Khoury & Steinhardt, arXiv:0910.2230 Linde, Mukhanov & Vikman, arXiv:0912.0944   
    • Generating Superhorizon Perturbations New result: In an expanding universe, to generate  perturbations consistent with observation, you must have one of: (1) Accelerated Expansion (2) Superluminal Sound Speed (3) Super­Planckian Energy Density    (Geshnizjani, WHK, Moradinezhad Dizgah, arXiv:1107.1241)
    • Non­Canonical Lagrangians as Bimetric Theories Lagrangian with arbitrary kinetic term: Acoustic metric Light cone:  Two horizons! Acoustic cone:    
    • Light Cones in DBI Inflation  Acoustic Cone: Light cone: x y   
    • Mode Freezing and Horizons Tensor modes freeze out at the Hubble Horizon Scalar modes freeze out at the Acoustic Horizon Curvature perturbations generated by shrinking acoustic horizon!    (Garriga & Mukhanov, arXiv:hep­th/9904176)
    • Horizons in DBI Inflation Hubble Horizon  Acoustic Horizon   
    • Beyond Inflation For               we still need inflation to generate superhorizon perturbations. Tachyacoustic Cosmology : generate superhorizon perturbations in a   radiation­ or matter­dominated universe Armendariz­Picon, arXiv:astro­ph/0606168 Piao, arXiv:gr­qc/0609071 Magueijo, arXiv:08030859 Bessada, WHK, Stojkovic, Wang, arXiv:0908.3898 Causally self­consistent cosmology: no timelike loops. Babichev, Mukhanov & Vikman, arXiv:0708.0561   
    • Light Cones in Tachyacoustic Cosmology  Acoustic Cone: Light cone: x y   
    • The Tachyacoustic Solution Decelerating Expansion: Decaying Sound Speed:   
    • Horizons in Tachyacoustic Cosmology Hubble Horizon: Acoustic Horizon: Hubble Horizon grows  (no tensor modes!) Acoustic Horizon shrinks   
    • Horizons in Tachyacoustic Cosmology Hubble Horizon  Acoustic Horizon   
    • Perturbations in Tachyacoustic Cosmology Hubble Horizon: Acoustic Horizon: (Magueijo, arXiv:0803.0859)    (Bessada, WHK, Stojkovic, Wang, arXiv:0908.3898)
    • Tachyacoustic Cosmology: Problems String embedding problematic Does not solve flatness problem Initial singularity Is it a dynamical attractor?  (Preliminary: yes)   
    • Summary The Hubble length is not the horizon. Expanding universe: only three ways to get scale invariance for a sufficient range of super­Hubble  perturbations: Accelerated expansion Superluminal sound speed Transplanckian energy density Nothing works nearly as well as inflation.