emergent gravity and cosmology: thermodynamic …
TRANSCRIPT
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Master Colloquium
Supervisors:Prof. Dr. Claus KieferProf. Dr. Pavel Kroupa Work done at:
Institute of Theoretical PhysicsUniversity of Cologne
University of Bonn
May 22, 2015
Pranjal Dhole
EMERGENT GRAVITY AND COSMOLOGY:THERMODYNAMIC PERSPECTIVE
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Motivation:
Black hole singularity
Big Bang singularity
Cosmological constant problem
Gravity and Quantum Theory
Points of contact and conflict
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OUTLINE:
Notion of emergence in Gravity: AdS/CFT and Verlinde's Entropic gravity
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OUTLINE:
Notion of emergence in Gravity: AdS/CFT and Verlinde's Entropic gravity
1. Gravity as emergent phenomenon: Sakharov Paradigm
7. Emergent Cosmology
(Refer thesis)
2. Temperature and Law of Equipartition in Gravity
3. BH thermodynamics Horizon thermodynamics
4. Action Functional : Hint of alternative description
5. Holographically conjugated variables thermodynamic conjugacy
6. Holographic equipartition
8. Further Investigations and my work
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1. Gravity as an emergent phenomenon
Sakharov Paradigm
Solids Spacetime
Mechanics, Elasticity Einstein's Theory
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1. Gravity as an emergent phenomenon
Sakharov Paradigm
Solids Spacetime
Mechanics, Elasticity Einstein's Theory
Statistical mechanicsof atoms/molecules
(well-known)
Emergence : Different dynamical variables → different descriptions.
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1. Gravity as an emergent phenomenon
Sakharov Paradigm
Solids Spacetime
Mechanics, Elasticity Einstein's Theory
Statistical mechanicsof atoms/molecules
(well-known)
Statistical mechanics of ``atoms of spacetime'' (?)
Emergence : Different dynamical variables → different descriptions.
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Boltzmann's postulate: Anything that can be heated has `atomic' structure!
Equipartition of energy connects thermodynamics to microscopic d.o.f.
Temperature of mattertold us that it has`atomic' structure
Equipartition Law:
demands granularity with finite n; degrees of freedom scale as volume.
2. Temperature and Law of Equipartition:
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Hawking temperature
Spacetimes can be
Static observer in Schwarzschild spacetime
[1975]
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Rindler observer in flat spacetime
Davies-Unruh temperature
Spacetimes can be
[1976]
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Indistinguishability of thermal and quantum fluctuations
Curved spacetime, Flat spacetime,
Hawking effect Unruh effect
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Kolekar, T.P. [gr-qc/1308.6289v2]
Curved spacetime, Flat spacetime,
Hawking effect Unruh effect
Generalisation toarbitrary spacetime:
Indistinguishability of thermal and quantum fluctuations
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Equipartition of `Area Bits' at null surface TP(2004) [gr-qc/0308070]
Null surface
(Hawking Temperature)
(Number of degrees of freedom)
Equipartition Law:
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BH Thermodynamics:
3. Black hole thermodynamics Horizon thermodynamics
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3. Black hole thermodynamics Horizon thermodynamics
Any static, spherically symmetric spacetime with horizon:
Horizon:
Temperature of horizon Einstein's equation evaluated at horizon
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3. Black hole thermodynamics Horizon thermodynamics
Any static, spherically symmetric spacetime with horizon:
Horizon:
Temperature of horizon Einstein's equation evaluated at horizon
Horizons at and :
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BH Thermodynamics:
Horizon Thermodynamics:
3. Black hole thermodynamics Horizon thermodynamics
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→ entropy of horizon → field equations:
Important!
TP(2009)[gr-qc/0912.3165]
4. Action Functional: Hint of alternative description
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HOLOGRAPHICREDUNDANCY!!
Why this happens??
Important!
TP(2005)[gr-qc/0412068]
4. Action Functional: Hint of alternative description
→ entropy of horizon → field equations:
TP(2009)[gr-qc/0912.3165]
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Canonical General Relativity via conjugated variables:
Thermodynamic Conjugacy:
5. Holographically conjugated variables thermodynamic conjugacy
Majhi,Parattu,TP,(2013)
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Surface DoF:
6. Holographic Equipartition
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Surface DoF:
Bulk DoF:
6. Holographic Equipartition
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Surface DoF:
Bulk DoF:
Static geometry: no evolution
Evolution of geometry
6. Holographic Equipartition
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Surface DoF:
Bulk DoF:
Static geometry: no evolution Holographic equipartition!
Evolution of geometry
6. Holographic Equipartition
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Bjorken(2006),TP(2013)7. Emergent Cosmology
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TP(2014)
Holographicequipartition
Holographicequipartition
7. Emergent Cosmology
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TP(2014)
Holographicequipartition
Holographicequipartition
7. Emergent Cosmology
StandardUniverse
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TP(2014)“Chicken is egg's wayof making another egg!”
Holographicequipartition
Holographicequipartition
7. Emergent Cosmology
StandardUniverse
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TP(2014)7. Emergent Cosmology
Thermodynamicequillibrium
Thermodynamicequillibrium
Emergence of cosmic space&
Arrow of time!
StandardUniverse
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dS
8. Further Investigations and my work
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dS
8. Further Investigations and my work
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dS
8. Further Investigations and my work
StandardUniverse
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dS
8. Further Investigations and my work
StandardUniverse
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dS dSStandardUniverse
8. Further Investigations and my work
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dS dS
Holographicdiscrepancy
HolographicequipartitionClassical Universe
8. Further Investigations and my work
StandardUniverse
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dS dS
Conformalsymmetry
Conformalsymmetry
NoConformalsymmetry
Holographicdiscrepancy
HolographicequipartitionClassical Universe
Breaking ofConformal symmetry
restoringConformal symmetry
8. Further Investigations and my work
StandardUniverse
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dS dS
Conformalsymmetry
Conformalsymmetry
NoConformalsymmetry
Conformal symmetry Holographic equipartition
Classical UniverseHolographicdiscrepancy
Holographicequipartition
Breaking ofConformal symmetry
restoringConformal symmetry
Needs more exploration!
(?)
Mechanism for symmetry breaking?
8. Further Investigations and my work
(?)
StandardUniverse
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2. Evaluate surface Hamiltonian in terms of conformal variables.
3. Check and for thermodynamic conjugacy relation.
Interesting:Conformal contributions
Non-conformal contributions
CMB spectrum: nearly scale invariantLook for breaking of conformal
symmetry at high energyWithin this framework
Observation
1. Define conformal variables
Formulate holographic equipartition and discrepancyin terms of conformal variables.
8. Further Investigations and my work
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1. Conformal Variables
8. Further Investigations and my work
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1. Conformal Variables
8. Further Investigations and my work
Work in progress!2. ...
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1. Conformal Variables
8. Further Investigations and my work
Work in progress!2. ...
Thank you for your attention!
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Holographic equipartition for de Sitter space
The dS maintain time translation invariance; natural choice for equillibrium.
For dS with Hubble radius
For pure de Sitter universe, we get
Pure dS universe maintain holographic equipartition with constant V!
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Comic expansion: Quest for holographic equipartition
Postulate:
using
We get standard FRW dynamics
In Planck units, this has discrete version:
Alternate way of studying Quantum Cosmology!
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TP(2014)7. Quantum Cosmology
“Chicken is egg's wayof making another egg!”
Holographicequipartition
Holographicequipartition
StandardCosmology
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Attractive features
Beginning and the end of the universe: non-zero, finite volume
Arrow of cosmic time → Thermodynamic arrow
Reduction of Cosmological constant problem to CosMIn
Recovery: Friedmann equations for
Postulate
will be determined byhigh energy physics
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Principle of Equivalence
Observer dependenceOf Physics
Lightcone structure isaffected by gravity Gravity = Geometry
Existence of observerswith horizons
All horizonshave entropy
Spacetime hasEntropy density
Equipartitionof energy Entropy is maximal
for all horizons
Field equations
Microstructure ofspacetime