EMERGENT GRAVITY AND COSMOLOGY: THERMODYNAMIC PERSPECTIVE

Transcription

1 EMERGENT GRAVITY AND COSMOLOGY: THERMODYNAMIC PERSPECTIVE Master Colloquium Pranjal Dhole University of Bonn Supervisors: Prof. Dr. Claus Kiefer Prof. Dr. Pavel Kroupa May 22, 2015 Work done at: Institute of Theoretical Physics University of Cologne

2 Motivation: Gravity and Quantum Theory Points of contact and conflict Black hole singularity Big Bang singularity Cosmological constant problem 2

3 OUTLINE: Notion of emergence in Gravity: AdS/CFT and Verlinde's Entropic gravity 3

4 OUTLINE: Notion of emergence in Gravity: AdS/CFT and Verlinde's Entropic gravity (Refer thesis) 1. Gravity as emergent phenomenon: Sakharov Paradigm 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 7. Emergent Cosmology 8. Further Investigations and my work 4

5 1. Gravity as an emergent phenomenon Sakharov Paradigm Solids Spacetime Mechanics, Elasticity Einstein's Theory 5

6 1. Gravity as an emergent phenomenon Sakharov Paradigm Solids Spacetime Mechanics, Elasticity Einstein's Theory Statistical mechanics of atoms/molecules (well-known) Emergence : Different dynamical variables different descriptions. 6

7 1. Gravity as an emergent phenomenon Sakharov Paradigm Solids Spacetime Mechanics, Elasticity Einstein's Theory Statistical mechanics of atoms/molecules (well-known) Statistical mechanics of ``atoms of spacetime'' (?) Emergence : Different dynamical variables different descriptions. 7

8 2. Temperature and Law of Equipartition: Boltzmann's postulate: Anything that can be heated has `atomic' structure! Equipartition Law: Equipartition of energy connects thermodynamics to microscopic d.o.f. Temperature of matter told us that it has `atomic' structure demands granularity with finite n; degrees of freedom scale as volume. 8

9 Spacetimes can be Static observer in Schwarzschild spacetime Hawking temperature [1975] 9

10 Spacetimes can be Rindler observer in flat spacetime Davies-Unruh temperature [1976] 10

11 Indistinguishability of thermal and quantum fluctuations Curved spacetime, Flat spacetime, Hawking effect Unruh effect 11

12 Indistinguishability of thermal and quantum fluctuations Curved spacetime, Flat spacetime, Hawking effect Unruh effect Generalisation to arbitrary spacetime: Kolekar, T.P. [gr-qc/ v2]

13 Equipartition of `Area Bits' at null surface TP(2004) [gr-qc/ ] Null surface (Hawking Temperature) (Number of degrees of freedom) Equipartition Law: 13

14 3. Black hole thermodynamics Horizon thermodynamics BH Thermodynamics: 14

15 3. Black hole thermodynamics Horizon thermodynamics Any static, spherically symmetric spacetime with horizon: Horizon: Temperature of horizon Einstein's equation evaluated at horizon 15

16 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 : 16

17 3. Black hole thermodynamics Horizon thermodynamics BH Thermodynamics: Horizon Thermodynamics: 17

18 4. Action Functional: Hint of alternative description Important! entropy of horizon field equations: TP(2009)[gr-qc/ ]

19 4. Action Functional: Hint of alternative description Why this happens?? Important! HOLOGRAPHIC REDUNDANCY!! TP(2005)[gr-qc/ ] entropy of horizon field equations: TP(2009)[gr-qc/ ]

20 5. Holographically conjugated variables thermodynamic conjugacy Canonical General Relativity via conjugated variables: Majhi,Parattu,TP,(2013) Thermodynamic Conjugacy: 20

21 6. Holographic Equipartition Surface DoF: 21

22 6. Holographic Equipartition Surface DoF: Bulk DoF: 22

23 6. Holographic Equipartition Surface DoF: Bulk DoF: Evolution of geometry Static geometry: no evolution 23

24 6. Holographic Equipartition Surface DoF: Bulk DoF: Evolution of geometry Static geometry: no evolution Holographic equipartition! 24

25 7. Emergent Cosmology Bjorken(2006),TP(2013) 25

26 7. Emergent Cosmology TP(2014) Holographic equipartition Holographic equipartition 26

27 7. Emergent Cosmology TP(2014) Holographic equipartition Standard Universe Holographic equipartition 27

28 7. Emergent Cosmology Chicken is egg's way of making another egg! TP(2014) Holographic equipartition Standard Universe Holographic equipartition 28

29 7. Emergent Cosmology TP(2014) Emergence of cosmic space & Arrow of time! Thermodynamic equillibrium Standard Universe Thermodynamic equillibrium 29

30 8. Further Investigations and my work ds 30

31 8. Further Investigations and my work ds 31

32 8. Further Investigations and my work ds Standard Universe 32

33 8. Further Investigations and my work ds Standard Universe 33

34 8. Further Investigations and my work ds Standard Universe ds 34

35 8. Further Investigations and my work ds Standard Universe ds Holographic discrepancy Classical Universe Holographic equipartition 35

36 8. Further Investigations and my work ds Standard Universe ds Holographic discrepancy Classical Universe Holographic equipartition Conformal symmetry Breaking of Conformal symmetry No Conformal symmetry restoring Conformal symmetry Conformal symmetry 36

37 8. Further Investigations and my work ds Standard Universe ds Holographic discrepancy Classical Universe Holographic equipartition (?) Conformal symmetry Breaking of Conformal symmetry No Conformal symmetry restoring Conformal symmetry Conformal symmetry Conformal symmetry Mechanism for symmetry breaking? (?) Holographic equipartition 37 Needs more exploration!

38 8. Further Investigations and my work 1. Define conformal variables 2. Evaluate surface Hamiltonian in terms of conformal variables. 3. Check and for thermodynamic conjugacy relation. Interesting: Conformal contributions Non-conformal contributions Formulate holographic equipartition and discrepancy in terms of conformal variables. Observation CMB spectrum: nearly scale invariant Look for breaking of conformal symmetry at high energy Within this framework 38

39 8. Further Investigations and my work 1. Conformal Variables 39

40 8. Further Investigations and my work 1. Conformal Variables Work in progress! 40

41 8. Further Investigations and my work 1. Conformal Variables Work in progress! 41 Thank you for your attention!

42 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! 42

43 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! 43

44 7. Quantum Cosmology Chicken is egg's way of making another egg! TP(2014) Holographic equipartition Standard Cosmology Holographic equipartition 44

45 Attractive features Beginning and the end of the universe: non-zero, finite volume Postulate Arrow of cosmic time Thermodynamic arrow Reduction of Cosmological constant problem to CosMIn Recovery: Friedmann equations for will be determined by high energy physics 45

46 Principle of Equivalence Observer dependence Of Physics Lightcone structure is affected by gravity Gravity = Geometry Existence of observers with horizons All horizons have entropy Spacetime has Entropy density Equipartition of energy Entropy is maximal for all horizons Field equations Microstructure of spacetime 46