Post on 14-Oct-2020
ACCCOSMICELERATIONDark energy and beyond
M. SAMICentre for Theoretical Physics
Jamia Millia University New Delhi
3/25/2013 IPMU 2013
Kobayashi-Maskawa Institute for the
Origin of Particles and the Universe,
Nagoya University, Nagoya .
3/25/2013
REFERENCES
MS, “ A primer on problems and prospects of dark
energy “ Curr Sci, V 97, 848 (2009) [arXiv:0904.3445].
M. Turner, D. Huterer, “Cosmic Acceleration, Dark
Energy and Fundamental Physics
“J.Phys.Soc.Jap.76:111015,2007.
E. Copeland, MS, S. Tsujikawa, “ Dynamic of Dark
Energy”, hep-th/0603057.
Zeldovic and Novikov, Structure and evolution of universe, V 2
IPMU 2013
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BRIEF OVER VIEW
• Cosmological constant a la Hook’s law---Static universe
Neumann (1895) and Seeliger (1896)
• Late time inconsistency of hot big bang: Resolution of
age crisis.
•Theoretical issues related cosmological constant (Sakharov)
Coincidence ; Fine tuning.
• Quintessence : quintessential inflation; problems.
• Modified theories of gravity:
• Local physics---Screening mechanisms.
Chameleon, Symmetron , Vainshtein mechanism.
Scope of chameleon/symmetron : Self acceleration.
Phenomenological extensions of massive gravity.
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Homogeneous and isotropic universe
Hubble Law
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NEWTONIAN COSMOLOGY
No static universe:
Co-moving system:
MS, arXiv:
0904.3445
(1895- Neumann, 1896-Seeliger)
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Static universe
Neumann (1895) and Seeliger(1896)
Einstein 1917
MS, arXiv: 0904.3445
Cosmological constant or Hook’s law
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NEWTONIAN COSMOLOGYCosmological constant a la Hook’s law
Static universe(K>0)
MS, Curr Sci, V 97, 848 (2009)
[arXiv:0904.3445].If no quasi-static universe then away
with cosmological constant!
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Inconsistencies of standard model
EARLY TIMES:
LATE TIMES: Age crisis
Flatness problem
Primordial inhomogeneities INFLATION
Horizon problem
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AGE CRISIS IN HOT BIG BANG
Matter dominated universe:
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Let us ignore gravity for a moment :
AGE CRISIS IN HOT BIG BANG
Present epoch:
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AGE CRISIS AND ITS RESOLUTION WITH
Open universe (K<0)
Repulsive effect
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AGE CRISIS AND ITS RESOLUTION WITH
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ENERGY OF VACUUM
SAKHAROV 1968
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The effective Cosmological constant
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COSMOLOGICAL CONSTANT
Old cosmological
constant problem
New cosmological constant problem
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The correct level of fine tuning
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CINCIDENCE PROBLEM ?
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z
WHERE IS THE COINSIDENCE ?
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SCALAR FIELD AS DARK ENERGYQuintessence
for steep pot.
Predictive power of scalar fieldsFor a priori given cosmic history, it is always possible to construct a field potentialsuch that it gives rise to the desired result. Thus the scalar field models should be judgedby their generic features.
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Scalar Field Dynamics in presence of background
matter : Tracker or Freezing Models
Scaling Solution:
MS, Curr Sci, V 97, 848 (2009) [arXiv:0904.3445]
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Absence of trackers: Thawing
Models
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Scalar Field Dynamics in presence of background
matter : Tracker or Freezing Models
Scaling Solution:
MS, Curr Sci, V 97, 848 (2009) [arXiv:0904.3445]
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Quintessential inflation-Model
Of reincarnation
P.J.E. Peebles, A.Vilenkin, PRD59,06350(1999)
MS, V. Sahni, Phys. Rev. D 70, 083513 (2004);
Phys. Rev. D 65, 023518 (2002); MS, N. Dadhich,
T.Shiromizu, PLB568, 118(2003).
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TRACKER POTENTIAL
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Quintessential Inflation (gravitational particle production)
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Quintessential Inflation (instant preheating)
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OBSERVATIONAL CONSTRAINTS
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Unstable under radiative corrections when coupled to
other fields unless severely fine tuned.
Quintessence problem
C. Kolda and D Lyth,
hep-th/9811375
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MODIFIED THEORIES OF GRAVITY
• Chameleon theories.
• Galileon modified theories
• Massive gravity Scalar degree(s) of freedom
LARGE SCALE MODIFICATION
Requirements
• Local physics be intact
• Cosmic acceleration
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SCALARON: Requirements
DE:
Solar Physics:
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Chameleon Field
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MASS SCREENING OR FIFTH FORCE SUPPRESSION
(Basic Idea)
Chameleon or Symmetron
Localized source:
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Kinetic suppression
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Galileon
Chameleon versus Galileon(Vainshtein )
Chameleon
Small distances:
Large distances:
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R, M
Chameleon at work
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Vainstein Effect- dynamical suppression of fifth force
Short distances:
Large distances:
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R, M
Vainshtein at work
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Symmetron: Dark energy
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Symmetry should break:
Local gravity constraints
Symmetron: Dark energy
arXiv: 1211.2289: K. Bamba, R.
Gannouji, MS
Kurt Hinterbichler, Justin Khoury: arxiV:1001.4525
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Scalar tensor theories
-Einstein frame
-Jordon frame
Local gravity constraints: Screening Mechanism
Chameleon Field
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VIABLE f(R) MODELS
Stability conditions:
Stable de Sitter:
Local gravity constraints:
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Problems of f(R): scalaron mass
Thongkool, MS, R. Gannouji, S.Jhingan,
Phys.Rev.D80:043523,2009 ;
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CURING THE SINGULARITY ?
Countering Term:Thongkool, MS, S. Rai Choudhury,
arXiv:0908.1663
Thongkool, MS, R. Gannouji, S. Jhingan,
Phys.Rev.D80:043523,2009 ;
S A. Appleby,R. A. Battye, A. Starobinsky,
arXiv:0909.1737
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Self acceleration:
Screening:
SELF ACCELERATION:SCOPE OF CHAMELEON THEORIES
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No scope for self acceleration
Chameleon/Symmetron theories-
arXiv:1284612: J. Wang, L. Hui and J. Khoury
arXiv: 1211.2289: K. Bamba, R.
Gannouji, MS
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(helicity 2 object) + (helicity 1 object)+ (helicity zero object)
Universally couples to all fields
a b
Ghost:
Stuckelberging
Massive gravity: possible extensions
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Massive gravity: possible extensions
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Massive gravity: possible extensions
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Massive gravity: possible extensions
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Massive gravity: possible extensions
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Massive gravity: possible extensions
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BEST MODEL OF
INFLATION AND DARK
ENERGY?
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Best model for quintessential inflation
BEST MODEL OF INFLATION AND DARK ENERGY?
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NATURE OF DARK ENERGY
IT COULD BE ANYTHING
OR
IT COULD BE NOTHING