status of the disformally coupled galileon model after...
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March 19, 2018 Rencontres de Moriond 2018 - Cosmology session
Status of the disformally coupled galileon model after GW170817
Clément Leloup – CEA/Irfu/DPhP Cosmology group
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Outline
I. Presentation of the galileon model
II. Methodology and datasets
III. Results
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Outline
I. Presentation of the galileon model
II. Methodology and datasets
III. Results
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The galileon model
➢ Simple principles for a successful modified gravity model : Additional scalar field : Galilean symmetry in Minkowskii space-time :
2nd order e.o.m in derivatives : avoid Ostrogradski ghosts
Direct couplings to matter : conformal and/or disformal
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The galileon model
➢ Simple principles for a successful modified gravity model : Additional scalar field : Galilean symmetry in Minkowskii space-time :
2nd order e.o.m in derivatives : avoid Ostrogradski ghosts
Direct couplings to matter : conformal and/or disformal
Disfavoured by Neveu et al. 2016
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The galileon model
➢ Most general action :
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The galileon model
Five galileon parameters
➢ Most general action :
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The galileon model
Five galileon parameters
➢ Most general action :
Disformal coupling
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The galileon model
Tadpole (behaves like so c1=0)
➢ Most general action :
Five galileon parameters
Disformal coupling
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The galileon model
Kinetic term
➢ Most general action :
Five galileon parameters
Disformal coupling
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Tadpole (behaves like so c1=0)
The galileon model
➢ Most general action :
Kinetic term
Five galileon parameters
Disformal coupling
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Tadpole (behaves like so c1=0)
Non-linear lagrangians
The galileon model
➢ Most general action :
➢ Non-linear lagrangians necessary to screen the galileon at small scales (Vainshtein effect)
Kinetic term
Five galileon parameters
Disformal coupling
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Tadpole (behaves like so c1=0)
Non-linear lagrangians
I. Presentation of the galileon model
II.Methodology and datasets
III.Results
Outline
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Methodology and datasets
➢ Cosmological background evolution :
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Methodology and datasets
➢ Cosmological background evolution :
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Methodology and datasets
➢ Cosmological background evolution :
functions of H and x
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Methodology and datasets
➢ Cosmological background evolution :
➢ Initial condition at z=0 : (H0, x0)
functions of H and x
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Methodology and datasets
➢ Cosmological background evolution :
➢ Initial condition at z=0 : (H0, x0)
functions of H and x
?
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Methodology and datasets
➢ Cosmological background evolution :
➢ Initial condition at z=0 : (H0, x0)
➢ Scaling invariance :
functions of H and x
?
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Methodology and datasets
➢ Cosmological background evolution :
➢ Initial condition at z=0 : (H0, x0)
➢ Scaling invariance :
functions of H and x
If B=x0 :
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Methodology and datasets
➢ Set of galileon parameters :
Full galileon :
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Methodology and datasets
➢ Set of galileon parameters :
Full galileon :
Fixed by flatness condition at z=0 :
Fixed by re-scaling
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Methodology and datasets
➢ Set of galileon parameters :
Full galileon :
Fixed by flatness condition at z=0 :
Fixed by re-scaling
Free parameters
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Methodology and datasets
➢ Set of galileon parameters :
Full galileon :
➢ In most studies, tracker solutions only :
attractor solutions
additional relation on
analytic solutions for the background evolution
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Methodology and datasets
➢ Set of galileon parameters :
Full galileon :
➢ In most studies, tracker solutions only :
attractor solutions
additional relation on
analytic solutions for the background evolution
➢ In this study, no restriction on the parameter space
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Methodology and datasets
➢ Set of galileon parameters :
Full galileon :
➢ In most studies, tracker solutions only :
attractor solutions
additional relation on
analytic solutions for the background evolution
➢ In this study, no restriction on the parameter space
➢ Galileon predictions obtained using our own modified version of Boltzmann code CAMB
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Methodology and datasets
➢ MCMC exploration of the parameter spaceagainst cosmological observations
→ Our own modified version of CosmoMC
→ Don't consider sets of parameters that fail stability conditions
CMB : Planck 2015 TTTEEE+lowP+lensing
BAO : 6dFGS, SDSS, BOSS, WiggleZ
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Methodology and datasets
➢ MCMC exploration of the parameter spaceagainst cosmological observations
→ Our own modified version of CosmoMC
→ Don't consider sets of parameters that fail stability conditions
CMB : Planck 2015 TTTEEE+lowP+lensing
BAO : 6dFGS, SDSS, BOSS, WiggleZ
➢ A posteriori comparison to GW speed constraint from GW170817
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Outline
I. Presentation of the galileon model
II.Methodology and datasets
III.Results
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➢ Fit to CMB TTTEEE+lensing+lowP :
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Results
➢ Fit to CMB TTTEEE+lensing+lowP :
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Results
➢ According to Barreira et al. 2014 :poor fit to CMB TT unless tracker reached before the start of dark energy era
➢ A posteriori check on the best fit
➢ Tracker defined by :
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Results
➢ According to Barreira et al. 2014 :poor fit to CMB TT unless tracker reached before the start of dark energy era
➢ A posteriori check on the best fit
➢ Tracker defined by :
OK !
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Results
➢ In most recent studies : Scans restricted to tracker solutions
No good fit to CMB temperature and lensing unless
➢ In this study : Exploration of the full parameter space
Good fit to CMB temperature and lensing keeping
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Results
Results
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➢ Fit to CMB :
Results
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➢ Fit to CMB :
Compatible with 0
Results
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➢ Fit to CMB :
➢ Low value for (due to lensing)
Results
➢ Low value for (due to lensing)
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➢ Fit to CMB :
Results
(arXiv:astro-ph/0108097)
➢ Low value for (due to lensing)
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➢ Fit to CMB :
Results
(arXiv:astro-ph/0108097)
➢ Low value for (due to lensing)
➢ Tension with lower bounds on zrei from observations of high redshift quasars and galaxies 14
➢ Fit to CMB :
Results➢ Fit to CMB+BAO :
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Results➢ Fit to CMB+BAO :
➢ Disagreement with reionization data
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Results➢ Fit to CMB+BAO :
➢ Disagreement with reionization data➢ Poor fit to BAO data + degradation of CMB fit
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Results
➢ Tension between CMB and CMB+BAO
Cosmological parameters Galileon parameters16
Results
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➢ Time delay between GW and light from GW170817
arXiv:1710.05834
Results
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➢ Time delay between GW and light from GW170817
arXiv:1710.05834
Results
Speed of GW
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➢ Time delay between GW and light from GW170817
arXiv:1710.05834
Results
Speed of GW
Redshift of host galaxy NGC4993 :
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➢ Time delay between GW and light from GW170817
arXiv:1710.05834
Results
Speed of GW
Redshift of host galaxy NGC4993 :
Time delay between GW emission and light emission.Conservative assumption (arXiv:1710.05834) :
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➢ Time delay between GW and light from GW170817
arXiv:1710.05834
Results
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Summary
➢ Study of a robust modified gravity model
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Summary
➢ Study of a robust modified gravity model➢ Full parameter space exploration provides good fit to
CMB data ...
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Summary
➢ Study of a robust modified gravity model➢ Full parameter space exploration provides good fit to
CMB data … in tension with reionization
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Summary
➢ Study of a robust modified gravity model➢ Full parameter space exploration provides good fit to
CMB data … in tension with reionization➢ Tensions increase with BAO
→ extend the model allowing for higher ?
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Summary
➢ Study of a robust modified gravity model➢ Full parameter space exploration provides good fit to
CMB data … in tension with reionization➢ Tensions increase with BAO
→ extend the model allowing for higher ?
➢ Most critical issue : GW170818
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Summary
➢ Study of a robust modified gravity model➢ Full parameter space exploration provides good fit to
CMB data … in tension with reionization➢ Tensions increase with BAO
→ extend the model allowing for higher ?
➢ Most critical issue : GW170818➢ Is there a last hope ?
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Summary
➢ Study of a robust modified gravity model➢ Full parameter space exploration provides good fit to
CMB data … in tension with reionization➢ Tensions increase with BAO
→ extend the model allowing for higher ?
➢ Most critical issue : GW170818➢ Is there a last hope ?➢ Yes if cubic galileon can be revived
Cubicgalileon
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Thank you !
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➢ Non-linear lagrangians Vainshtein screening
Galileon fifth force
Newtonian force
GR
Galileon dynamics
