Transcript The Accelerating Universe

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L. Perivolaropoulos
http://leandros.physics.uoi.gr
Department of Physics
University of Ioannina
Geometrical
(Standard Candles, Standard Rulers)
Cosmological Tests of
the Cosmological Constant Λ
Dynamical
(Growth of Fluctuations by Gravity)
The Cosmological Constant (w=-1) remains
consistent with all current data as a driving force of the acceleration.
Q: What could be the origin of Λ?
Α: Vacuum Fluctuations with Cutoff (ωc=10-3eV, lc=0.1mm)
Q: What Experiment could probe the cutoff structure of the vacuum in the lab?
A: Casimir Effect (detected attraction of metal plates)
Cutoff Prediction:
Extra Dimension:
Change of sign of Casimir Force ( d  lr  lc )
Change of sign at higher separations
lr  lc 
Predicted Hubble Expansion History (flat universe):
H ( z)
2
CDM

a2
3
 2  H02 0m 1  z   
a

   0 m  1
Luminosity Distance (standard candles - SnIa):
Obs
SnIa
L
l
4 d L2
dz 
d L ( z )th  c 1  z  
0 H  z ;  m 
z
dL  z 
SnIa : z  (0,1.7]
Angular Diameter Distance (standard rulers – CMB sound horizon):
dA  z 


rs
dA  z 
rs

c z
dz 
d A ( z )th 

1

z
  0 H  z ; m 
BAO : z  0.35
CMB Spectrum : z  1089
CDM   w0 , w1    1,0
Generalize H(z):
w  z   w0  w1
z
1 z
5log10  d L, A ( zi )obs   5log  d L, A ( zi ; w0 , w1 )th 
  min
 2  m , w0 , w1    
2
2
Minimize:
N
i 1
ESSENCE+SNLS+HST data
i
WMAP3+SDSS(2007) data
Standard Candles
(SnIa)
0 m  0.24
2σ tension between
standard candles and
standard rulers
Lazkoz, Nesseris, LP
arxiv: 0712.1232
Standard Rulers
(CMB+BAO)
Measure growth function of cosmological perturbations:
Predicted Evolution of δ :
(General Relativity)
Parametrization:
f  m  a 

Wang, Steinhardt, Astrophys.J.508:483-490,1998
CDM : de    const
6
 
11
f  m  a 

Parametrization:
CDM : de    const
 
6
11
Parametrization:
CDM : de    const
 
6
11
Fit to LSS data:
0 m  0.3
ΛCDM
ΛCDM provides an excellent fit
to the linear perturbations
growth data
best fit
S. Nesseris, LP, arxiv: 0710.1092,
Phys.Rev.D77:023504,2008
Equivalence Principle
EM field zero point vacuum energy:
V
Gravity couples to the
zero point energy of the
vacuum
pmax  
?
V  const 
 

Q: Can we probe the zero point energy of the vacuum in the lab?
A: No! Non-gravitational experiments are only sensitive to changes
of the zero point energy.
But: This is not so in the presence of a physical finite cutoff !
Majajan, Sarkar, Padmanbhan,
Phys.Lett.B641:6-10,2006
Casimir Force Experiments can pick up the presence of a physical cutoff !!
Vacuum Energy gets modified in the presence
of the plates (boundary conditions)
d
2
FCas
ECas
  2
hc

240d 4
  2
hc

720d 3
Attractive Force
d
Agreement between
theory and experiment
at 1%
Harris, Chen, Mohideen,
2000
d (nm)
EM vacuum energy with cutoff
UV regulator
L  d
d2
L
d
Modification of vacuum energy
due to the plates:
β=1
repulsive
L
attractive
d
β=0 (R=0)
LP, arxiv: 0802.1531, accepted in
Phys.Rev.D (to appear)
β=0 (R=0)
β=1
Thus, the cutoff predicts a Casimir
force which becomes repulsive for
d<0.6mm (not consistent with
experiments)
L
Casimir Force decreases
in the presence of an extra dimension
d
Poppenhaeger et. al.
hep-th/0309066 Phys.Lett.B582:1-5,2004
A change of sign of the Casimir force at low surface separations could
be an indication of a fundamental cutoff in the vacuum energy modes.
Such a cutoff could be an indication of both new physics and the origin of
the Cosmological Constant.
β=0 (R=0)
β=1
Standard Rulers are systematically less in favor of ΛCDM
than Standard Candles.
L
d
Geometrical
(Standard Candles, Standard Rulers)
Cosmological Tests of
the Cosmological Constant Λ
Dynamical
(Growth of Fluctuations by Gravity)
The Cosmological Constant (w=-1) remains
consistent with all current data as a driving force of the acceleration.
Q: What could be the origin of Λ?
Α: Vacuum Fluctuations with Cutoff (ωc=10-3eV, lc=0.1mm)
Q: What Experiment could probe the cutoff structure of the vacuum in the lab?
A: Casimir Effect (detected attraction of metal plates)
Cutoff Prediction:
Extra Dimension:
d  l  l ) : Not Detected
Change of sign of Casimir Force (d<l
c
r
Change of sign at higher separations
c
lr  lc 
Unless New Physics is imposed, current Casimir force experiments are not consistent
with the presence of the cutoff required to produce the observed value of Λ.