Chameleon dark energy - University of California, Los Angeles · Chameleon dark energy GammeV-CHASE...
Transcript of Chameleon dark energy - University of California, Los Angeles · Chameleon dark energy GammeV-CHASE...
Chameleon dark energyGammeV-CHASE
Chameleon and thin-shell effectsOscillation
Introduction
1 Cosmic acceleration is the greatest mystery in cosmology.
cosmological constant?scalar field, modified gravity ⇒ w(z) 6= −1, fifth forces, etc.
2 Chameleon dark energy
looks like cosmological constant on large scalesevades fifth force constraints by becoming massive inhigh-density environmentsphoton coupling ⇒ oscillation
3 GammeV-CHASE afterglow experiment
produce chameleon particles through oscillationtrap particles inside chamber“afterglow” as particles oscillate back into photonsconstraints on chameleon parameter space published
Amol Upadhye How dark is dark energy?
Chameleon dark energyGammeV-CHASE
Chameleon and thin-shell effectsOscillation
Chameleon scalar field
Action for a photon-coupled chameleon field:
S =
∫d4x
[− 1
2(∂φ)2 − V (φ) + Lmat(e
βmφMPl gµν) − 1
4 eβγφ
MPl FµνFµν]
nonlinear V ′
⇒ nonlinear e.o.m.
linear matter coupling
∼ βmρφ/MPl
photon coupling
∼ 12βγφ(B2 − E 2)/MPl
mass of field depends on matterdistribution
effective mass meff higher in denserenvironments
⇒ chameleon and thin-shell effects
chameleon-photonoscillation inbackgroundmagnetic field
Amol Upadhye How dark is dark energy?
Chameleon dark energyGammeV-CHASE
Chameleon and thin-shell effectsOscillation
Chameleon scalar field
Action for a photon-coupled chameleon field:
S =
∫d4x
[− 1
2(∂φ)2 − V (φ) + Lmat(e
βmφMPl gµν) − 1
4 eβγφ
MPl FµνFµν]
nonlinear V ′
⇒ nonlinear e.o.m.
linear matter coupling
∼ βmρφ/MPl
photon coupling
∼ 12βγφ(B2 − E 2)/MPl
mass of field depends on matterdistribution
effective mass meff higher in denserenvironments
⇒ chameleon and thin-shell effects
chameleon-photonoscillation inbackgroundmagnetic field
Amol Upadhye How dark is dark energy?
Chameleon dark energyGammeV-CHASE
Chameleon and thin-shell effectsOscillation
Chameleon scalar field
Action for a photon-coupled chameleon field:
S =
∫d4x
[− 1
2(∂φ)2 − V (φ) + Lmat(e
βmφMPl gµν) − 1
4 eβγφ
MPl FµνFµν]
nonlinear V ′
⇒ nonlinear e.o.m.
linear matter coupling
∼ βmρφ/MPl
photon coupling
∼ 12βγφ(B2 − E 2)/MPl
mass of field depends on matterdistribution
effective mass meff higher in denserenvironments
⇒ chameleon and thin-shell effects
chameleon-photonoscillation inbackgroundmagnetic field
Amol Upadhye How dark is dark energy?
Chameleon dark energyGammeV-CHASE
Chameleon and thin-shell effectsOscillation
Chameleon and thin-shell effects
(AU, Gubser, Khoury 2006)Amol Upadhye How dark is dark energy?
0
0.2
0.4
0.6
0.8
1
-20 -15 -10 -5 0 5 10 15 20
φ(x)
/φbu
lk
x [m-1eff]
0.3131030
thickness[m
eff-1 ]
force on test particle:F ∝ dφ/dx
vacuum
Chameleon dark energyGammeV-CHASE
Chameleon and thin-shell effectsOscillation
Chameleon-photon oscillation
γ ↔ φ conversion in background ~B field(from φF 2 interaction)
Oscillation probability
massless limit, parallel to ~B: Pγ↔φ =β2γB
2t2
4M2Pl
(AU, Steffen, Weltman 2010)
conversion rate for a chameleon particle
propagate through ~Bmeasure particle content after time ∆t
conversion rate Γ =Pγ↔φ(∆t)
∆taverage over particles to get total rate
Amol Upadhye How dark is dark energy?
Chameleon dark energyGammeV-CHASE
Chameleon and thin-shell effectsOscillation
Window as a quantum measurement device
0 5 10 15 20x [meff
-1]
density ρbackground φ0φ0 + δφphoton
Amol Upadhye How dark is dark energy?
Chameleon dark energyGammeV-CHASE
Experimental setupConstraints
A simple afterglow experiment
(a) Production phase: photons streamed through ~B0 region; someoscillate into chameleons
(b) Afterglow phase: chameleons slowly oscillate back intophotons, escaping chamber
Amol Upadhye How dark is dark energy?
Chameleon dark energyGammeV-CHASE
Experimental setupConstraints
GammeV-CHASE apparatus
1 Multiple magnetic field runs
2 Partitioning of magnetic field region
3 Modulation of detector
4 Vacuum maintained by ion pump
Amol Upadhye How dark is dark energy?
Chameleon dark energyGammeV-CHASE
Experimental setupConstraints
Conversion rate in GammeV-CHASE
(AU, et. al., 2012 (in prep.))Amol Upadhye How dark is dark energy?
1e-16
1e-14
1e-12
1e-10
1e-08
1e-06
0.0001
0.0001 0.001 0.01 0.1
rate
[Hz]
meff(chamber) [eV]
decay
afterglow
ξref
0 (V∝ φ 4)π/3 (V∝ 1/φ )π (V∝ exp φ)
Chameleon dark energyGammeV-CHASE
Experimental setupConstraints
Expected afterglow signal
Amol Upadhye How dark is dark energy?
0.01
1
100
10000
1e+06
1e+08
1e+10
1e+12
-1500 -1000 -500 0 500 1000 1500 2000 2500 3000
afte
rglo
w ra
te [s
ec-1
]
time [sec]
0.2 T
0.45 T
1.0 T
2.2 T
5.0 T
observation period βγ=3e11
Chameleon dark energyGammeV-CHASE
Experimental setupConstraints
Expected afterglow signal
Amol Upadhye How dark is dark energy?
0.01
1
100
10000
1e+06
1e+08
1e+10
1e+12
-1500 -1000 -500 0 500 1000 1500 2000 2500 3000
afte
rglo
w ra
te [s
ec-1
]
time [sec]
0.05 T0.09 T
0.2 T
0.45 T
1.0 T
2.2 T
5.0 T
observation period βγ=1e13
Chameleon dark energyGammeV-CHASE
Experimental setupConstraints
Expected afterglow signal
Amol Upadhye How dark is dark energy?
0.01
1
100
10000
1e+06
1e+08
1e+10
1e+12
-1500 -1000 -500 0 500 1000 1500 2000 2500 3000
afte
rglo
w ra
te [s
ec-1
]
time [sec]
0.05 T0.09 T
0.2 T0.45 T1.0 T2.2 T5.0 T
observation period βγ=3e14
Chameleon dark energyGammeV-CHASE
Experimental setupConstraints
Expected afterglow signal
Amol Upadhye How dark is dark energy?
0.01
1
100
10000
1e+06
1e+08
1e+10
1e+12
-1500 -1000 -500 0 500 1000 1500 2000 2500 3000
afte
rglo
w ra
te [s
ec-1
]
time [sec]
0.05 T0.09 T0.2 T0.45 T1.0 T2.2 T5.0 T
observation period βγ=1e16
Chameleon dark energyGammeV-CHASE
Experimental setupConstraints
GammeV-CHASE constraints
(Steffen, AU, et. al., 2010)Amol Upadhye How dark is dark energy?
effective mass meff [eV]
phot
on c
oupl
ing
β γ
scalarpseudoscalar
Collider constraints
GammeVconstraints
1e-05 0.0001 0.001 0.01 0.1 1e+10
1e+11
1e+12
1e+13
1e+14
1e+15
1e+16
1e+17
CHASE constraints
effective mass meff [eV]
phot
on c
oupl
ing
β γ
scalarpseudoscalar
Collider constraints
GammeVconstraints
1e-05 0.0001 0.001 0.01 0.1 1e+10
1e+11
1e+12
1e+13
1e+14
1e+15
1e+16
1e+17
CHASE constraints
Chameleon dark energyGammeV-CHASE
Experimental setupConstraints
Constraints on dark energy, V (φ) ≈ M4Λ + M4−N
Λ φN
(Steffen, AU, et. al., 2010)Amol Upadhye How dark is dark energy?
matter coupling βm
phot
on c
oupl
ing
β γ
Collider constraints
g γ =
βγ /
MP
l [G
eV-1
]
1e-8
1e-7
1e-6
1e-5
1e-4
1e-3
1e-2
10000 1e+08 1e+12 1e+16 1e+20 1e+24 1e+10
1e+11
1e+12
1e+13
1e+14
1e+15
1e+16
1e+17
N=-1N=-2N=-4N=4, λ=10-2
N=4, λ=10-4
matter coupling βm
phot
on c
oupl
ing
β γ
Collider constraints
g γ =
βγ /
MP
l [G
eV-1
]
1e-8
1e-7
1e-6
1e-5
1e-4
1e-3
1e-2
10000 1e+08 1e+12 1e+16 1e+20 1e+24 1e+10
1e+11
1e+12
1e+13
1e+14
1e+15
1e+16
1e+17
N=-1N=-2N=-4N=4, λ=10-2
N=4, λ=10-4
Chameleon dark energyGammeV-CHASE
Experimental setupConstraints
Conclusions
1 Laboratory searches for dark energy are complementary tocosmological probes.
2 GammeV and GammeV-CHASE attempted to produce, trap,and detect chameleon dark energy through its afterglow.
3 GammeV was a simple modification of an axion experiment,suggesting possibilities for future experiments.
4 GammeV-CHASE published constraints in Steffen, AU,Baumbaugh, Chou, Mazur, Tomlin, Weltman, Wester 2010.
excluded 4 orders of magnitude in βγ at meff = MΛ
bridged gap between GammeV and collider constraints
Amol Upadhye How dark is dark energy?
Chameleon dark energyGammeV-CHASE
Experimental setupConstraints
The End.
Amol Upadhye How dark is dark energy?