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Strongly coupled plasma - hydrodynamics, thermalization and - - PowerPoint PPT Presentation

Strongly coupled plasma - hydrodynamics, thermalization and nonequilibrium behavior Romuald A. Janik Jagiellonian University Krakw work with M. Heller, P. Witaszczyk see RJ 1311.3966 [hep-ph] for a recent review 1 / 22 Outline Why use


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SLIDE 1

Strongly coupled plasma - hydrodynamics, thermalization and nonequilibrium behavior

Romuald A. Janik

Jagiellonian University Kraków

work with M. Heller, P. Witaszczyk see RJ 1311.3966 [hep-ph] for a recent review

1 / 22

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SLIDE 2

Outline Why use AdS/CFT? N = 4 plasma versus QCD plasma The AdS/CFT description of a plasma system Boost-invariant flow The transition to hydrodynamics and its characteristics Nonequillibrium degrees of freedom Conclusions

2 / 22

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SLIDE 3

The AdS/CFT correspondence N = 4 Super Yang-Mills theory ≡ Superstrings on AdS5 × S5 strong coupling (semi-)classical strings nonperturbative physics

  • r supergravity

very difficult ‘easy’ weak coupling highly quantum regime ‘easy’ very difficult

◮ New ways of looking at nonperturbative gauge theory physics... ◮ Intricate links with General Relativity... ◮ Has been extended to many other cases

3 / 22

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SLIDE 4

The AdS/CFT correspondence N = 4 Super Yang-Mills theory ≡ Superstrings on AdS5 × S5 strong coupling (semi-)classical strings nonperturbative physics

  • r supergravity

very difficult ‘easy’ weak coupling highly quantum regime ‘easy’ very difficult

◮ New ways of looking at nonperturbative gauge theory physics... ◮ Intricate links with General Relativity... ◮ Has been extended to many other cases

3 / 22

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SLIDE 5

The AdS/CFT correspondence N = 4 Super Yang-Mills theory ≡ Superstrings on AdS5 × S5 strong coupling (semi-)classical strings nonperturbative physics

  • r supergravity

very difficult ‘easy’ weak coupling highly quantum regime ‘easy’ very difficult

◮ New ways of looking at nonperturbative gauge theory physics... ◮ Intricate links with General Relativity... ◮ Has been extended to many other cases

3 / 22

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SLIDE 6

The AdS/CFT correspondence N = 4 Super Yang-Mills theory ≡ Superstrings on AdS5 × S5 strong coupling (semi-)classical strings nonperturbative physics

  • r supergravity

very difficult ‘easy’ weak coupling highly quantum regime ‘easy’ very difficult

◮ New ways of looking at nonperturbative gauge theory physics... ◮ Intricate links with General Relativity... ◮ Has been extended to many other cases

3 / 22

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SLIDE 7

Why use AdS/CFT for quark-gluon plasma physics? Problem:

◮ QCD plasma produced at RHIC/LHC is most probably a strongly

coupled system

◮ Nonperturbative methods applicable to real time dynamics are very

scarce

◮ Conventional lattice QCD is inherently Euclidean

AdS/CFT works equally well for Minkowski and Euclidean signature – study similar problems in N =4 SYM – generalize later to other theories

4 / 22

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SLIDE 8

Why use AdS/CFT for quark-gluon plasma physics? Problem:

◮ QCD plasma produced at RHIC/LHC is most probably a strongly

coupled system

◮ Nonperturbative methods applicable to real time dynamics are very

scarce

◮ Conventional lattice QCD is inherently Euclidean

AdS/CFT works equally well for Minkowski and Euclidean signature – study similar problems in N =4 SYM – generalize later to other theories

4 / 22

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SLIDE 9

Why use AdS/CFT for quark-gluon plasma physics? Problem:

◮ QCD plasma produced at RHIC/LHC is most probably a strongly

coupled system

◮ Nonperturbative methods applicable to real time dynamics are very

scarce

◮ Conventional lattice QCD is inherently Euclidean

AdS/CFT works equally well for Minkowski and Euclidean signature – study similar problems in N =4 SYM – generalize later to other theories

4 / 22

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SLIDE 10

Why use AdS/CFT for quark-gluon plasma physics? Problem:

◮ QCD plasma produced at RHIC/LHC is most probably a strongly

coupled system

◮ Nonperturbative methods applicable to real time dynamics are very

scarce

◮ Conventional lattice QCD is inherently Euclidean

AdS/CFT works equally well for Minkowski and Euclidean signature – study similar problems in N =4 SYM – generalize later to other theories

4 / 22

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SLIDE 11

Why use AdS/CFT for quark-gluon plasma physics? Problem:

◮ QCD plasma produced at RHIC/LHC is most probably a strongly

coupled system

◮ Nonperturbative methods applicable to real time dynamics are very

scarce

◮ Conventional lattice QCD is inherently Euclidean

AdS/CFT works equally well for Minkowski and Euclidean signature – study similar problems in N =4 SYM – generalize later to other theories

4 / 22

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SLIDE 12

Why use AdS/CFT for quark-gluon plasma physics? Problem:

◮ QCD plasma produced at RHIC/LHC is most probably a strongly

coupled system

◮ Nonperturbative methods applicable to real time dynamics are very

scarce

◮ Conventional lattice QCD is inherently Euclidean

AdS/CFT works equally well for Minkowski and Euclidean signature – study similar problems in N =4 SYM – generalize later to other theories

4 / 22

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SLIDE 13

Why use AdS/CFT for quark-gluon plasma physics? Problem:

◮ QCD plasma produced at RHIC/LHC is most probably a strongly

coupled system

◮ Nonperturbative methods applicable to real time dynamics are very

scarce

◮ Conventional lattice QCD is inherently Euclidean

AdS/CFT works equally well for Minkowski and Euclidean signature – study similar problems in N =4 SYM – generalize later to other theories

4 / 22

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SLIDE 14

Why use AdS/CFT for quark-gluon plasma physics? Problem:

◮ QCD plasma produced at RHIC/LHC is most probably a strongly

coupled system

◮ Nonperturbative methods applicable to real time dynamics are very

scarce

◮ Conventional lattice QCD is inherently Euclidean

AdS/CFT works equally well for Minkowski and Euclidean signature – study similar problems in N =4 SYM – generalize later to other theories

4 / 22

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SLIDE 15

Point of reference: heavy-ion collision at RHIC/LHC:

5 / 22

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SLIDE 16

Point of reference: heavy-ion collision at RHIC/LHC:

5 / 22

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SLIDE 17

Point of reference: heavy-ion collision at RHIC/LHC:

5 / 22

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SLIDE 18

Point of reference: heavy-ion collision at RHIC/LHC:

5 / 22

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SLIDE 19

Point of reference: heavy-ion collision at RHIC/LHC:

5 / 22

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Point of reference: heavy-ion collision at RHIC/LHC:

5 / 22

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SLIDE 21

Point of reference: heavy-ion collision at RHIC/LHC:

5 / 22

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SLIDE 22

N = 4 plasma versus QCD plasma Similarities:

◮ Deconfined phase ◮ Strongly coupled ◮ No supersymmetry!

Differences:

◮ No running coupling −

→ Even at very high energy densities the coupling remains strong

◮ (Exactly) conformal equation of state −

→ Perhaps not so bad around T ∼ 1.5 − 2.5Tc

◮ No confinement/deconfinement phase transition −

→ The N = 4 plasma expands and cools indefinitely One can pass to more complicated AdS/CFT setups and lift the above differences

6 / 22

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SLIDE 23

N = 4 plasma versus QCD plasma Similarities:

◮ Deconfined phase ◮ Strongly coupled ◮ No supersymmetry!

Differences:

◮ No running coupling −

→ Even at very high energy densities the coupling remains strong

◮ (Exactly) conformal equation of state −

→ Perhaps not so bad around T ∼ 1.5 − 2.5Tc

◮ No confinement/deconfinement phase transition −

→ The N = 4 plasma expands and cools indefinitely One can pass to more complicated AdS/CFT setups and lift the above differences

6 / 22

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SLIDE 24

N = 4 plasma versus QCD plasma Similarities:

◮ Deconfined phase ◮ Strongly coupled ◮ No supersymmetry!

Differences:

◮ No running coupling −

→ Even at very high energy densities the coupling remains strong

◮ (Exactly) conformal equation of state −

→ Perhaps not so bad around T ∼ 1.5 − 2.5Tc

◮ No confinement/deconfinement phase transition −

→ The N = 4 plasma expands and cools indefinitely One can pass to more complicated AdS/CFT setups and lift the above differences

6 / 22

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SLIDE 25

N = 4 plasma versus QCD plasma Similarities:

◮ Deconfined phase ◮ Strongly coupled ◮ No supersymmetry!

Differences:

◮ No running coupling −

→ Even at very high energy densities the coupling remains strong

◮ (Exactly) conformal equation of state −

→ Perhaps not so bad around T ∼ 1.5 − 2.5Tc

◮ No confinement/deconfinement phase transition −

→ The N = 4 plasma expands and cools indefinitely One can pass to more complicated AdS/CFT setups and lift the above differences

6 / 22

slide-26
SLIDE 26

N = 4 plasma versus QCD plasma Similarities:

◮ Deconfined phase ◮ Strongly coupled ◮ No supersymmetry!

Differences:

◮ No running coupling −

→ Even at very high energy densities the coupling remains strong

◮ (Exactly) conformal equation of state −

→ Perhaps not so bad around T ∼ 1.5 − 2.5Tc

◮ No confinement/deconfinement phase transition −

→ The N = 4 plasma expands and cools indefinitely One can pass to more complicated AdS/CFT setups and lift the above differences

6 / 22

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SLIDE 27

N = 4 plasma versus QCD plasma Similarities:

◮ Deconfined phase ◮ Strongly coupled ◮ No supersymmetry!

Differences:

◮ No running coupling −

→ Even at very high energy densities the coupling remains strong

◮ (Exactly) conformal equation of state −

→ Perhaps not so bad around T ∼ 1.5 − 2.5Tc

◮ No confinement/deconfinement phase transition −

→ The N = 4 plasma expands and cools indefinitely One can pass to more complicated AdS/CFT setups and lift the above differences

6 / 22

slide-28
SLIDE 28

N = 4 plasma versus QCD plasma Similarities:

◮ Deconfined phase ◮ Strongly coupled ◮ No supersymmetry!

Differences:

◮ No running coupling −

→ Even at very high energy densities the coupling remains strong

◮ (Exactly) conformal equation of state −

→ Perhaps not so bad around T ∼ 1.5 − 2.5Tc

◮ No confinement/deconfinement phase transition −

→ The N = 4 plasma expands and cools indefinitely One can pass to more complicated AdS/CFT setups and lift the above differences

6 / 22

slide-29
SLIDE 29

N = 4 plasma versus QCD plasma Similarities:

◮ Deconfined phase ◮ Strongly coupled ◮ No supersymmetry!

Differences:

◮ No running coupling −

→ Even at very high energy densities the coupling remains strong

◮ (Exactly) conformal equation of state −

→ Perhaps not so bad around T ∼ 1.5 − 2.5Tc

◮ No confinement/deconfinement phase transition −

→ The N = 4 plasma expands and cools indefinitely One can pass to more complicated AdS/CFT setups and lift the above differences

6 / 22

slide-30
SLIDE 30

N = 4 plasma versus QCD plasma Similarities:

◮ Deconfined phase ◮ Strongly coupled ◮ No supersymmetry!

Differences:

◮ No running coupling −

→ Even at very high energy densities the coupling remains strong

◮ (Exactly) conformal equation of state −

→ Perhaps not so bad around T ∼ 1.5 − 2.5Tc

◮ No confinement/deconfinement phase transition −

→ The N = 4 plasma expands and cools indefinitely One can pass to more complicated AdS/CFT setups and lift the above differences

6 / 22

slide-31
SLIDE 31

N = 4 plasma versus QCD plasma Similarities:

◮ Deconfined phase ◮ Strongly coupled ◮ No supersymmetry!

Differences:

◮ No running coupling −

→ Even at very high energy densities the coupling remains strong

◮ (Exactly) conformal equation of state −

→ Perhaps not so bad around T ∼ 1.5 − 2.5Tc

◮ No confinement/deconfinement phase transition −

→ The N = 4 plasma expands and cools indefinitely One can pass to more complicated AdS/CFT setups and lift the above differences

6 / 22

slide-32
SLIDE 32

N = 4 plasma versus QCD plasma Similarities:

◮ Deconfined phase ◮ Strongly coupled ◮ No supersymmetry!

Differences:

◮ No running coupling −

→ Even at very high energy densities the coupling remains strong

◮ (Exactly) conformal equation of state −

→ Perhaps not so bad around T ∼ 1.5 − 2.5Tc

◮ No confinement/deconfinement phase transition −

→ The N = 4 plasma expands and cools indefinitely One can pass to more complicated AdS/CFT setups and lift the above differences

6 / 22

slide-33
SLIDE 33

N = 4 plasma versus QCD plasma Similarities:

◮ Deconfined phase ◮ Strongly coupled ◮ No supersymmetry!

Differences:

◮ No running coupling −

→ Even at very high energy densities the coupling remains strong

◮ (Exactly) conformal equation of state −

→ Perhaps not so bad around T ∼ 1.5 − 2.5Tc

◮ No confinement/deconfinement phase transition −

→ The N = 4 plasma expands and cools indefinitely One can pass to more complicated AdS/CFT setups and lift the above differences

6 / 22

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SLIDE 34

Why study N = 4 plasma?

◮ The applicability of using N = 4 plasma to model real world

phenomenae dependes on the questions asked..

◮ Use it as a theoretical laboratory where we may compute from ‘first

principles’ nonequilibrium nonperturbative dynamics

◮ Gain qualitative insight into the physics which is very difficult to

access using other methods

◮ Discover some universal properties? (like η/s) ◮ For N = 4 plasma the AdS/CFT correspondence is technically

simplest

◮ Use the results on strong coupling properties of N = 4 plasma as a

point of reference for analyzing/describing QCD plasma

◮ Eventually one may consider more realistic theories with AdS/CFT

duals...

7 / 22

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SLIDE 35

Why study N = 4 plasma?

◮ The applicability of using N = 4 plasma to model real world

phenomenae dependes on the questions asked..

◮ Use it as a theoretical laboratory where we may compute from ‘first

principles’ nonequilibrium nonperturbative dynamics

◮ Gain qualitative insight into the physics which is very difficult to

access using other methods

◮ Discover some universal properties? (like η/s) ◮ For N = 4 plasma the AdS/CFT correspondence is technically

simplest

◮ Use the results on strong coupling properties of N = 4 plasma as a

point of reference for analyzing/describing QCD plasma

◮ Eventually one may consider more realistic theories with AdS/CFT

duals...

7 / 22

slide-36
SLIDE 36

Why study N = 4 plasma?

◮ The applicability of using N = 4 plasma to model real world

phenomenae dependes on the questions asked..

◮ Use it as a theoretical laboratory where we may compute from ‘first

principles’ nonequilibrium nonperturbative dynamics

◮ Gain qualitative insight into the physics which is very difficult to

access using other methods

◮ Discover some universal properties? (like η/s) ◮ For N = 4 plasma the AdS/CFT correspondence is technically

simplest

◮ Use the results on strong coupling properties of N = 4 plasma as a

point of reference for analyzing/describing QCD plasma

◮ Eventually one may consider more realistic theories with AdS/CFT

duals...

7 / 22

slide-37
SLIDE 37

Why study N = 4 plasma?

◮ The applicability of using N = 4 plasma to model real world

phenomenae dependes on the questions asked..

◮ Use it as a theoretical laboratory where we may compute from ‘first

principles’ nonequilibrium nonperturbative dynamics

◮ Gain qualitative insight into the physics which is very difficult to

access using other methods

◮ Discover some universal properties? (like η/s) ◮ For N = 4 plasma the AdS/CFT correspondence is technically

simplest

◮ Use the results on strong coupling properties of N = 4 plasma as a

point of reference for analyzing/describing QCD plasma

◮ Eventually one may consider more realistic theories with AdS/CFT

duals...

7 / 22

slide-38
SLIDE 38

Why study N = 4 plasma?

◮ The applicability of using N = 4 plasma to model real world

phenomenae dependes on the questions asked..

◮ Use it as a theoretical laboratory where we may compute from ‘first

principles’ nonequilibrium nonperturbative dynamics

◮ Gain qualitative insight into the physics which is very difficult to

access using other methods

◮ Discover some universal properties? (like η/s) ◮ For N = 4 plasma the AdS/CFT correspondence is technically

simplest

◮ Use the results on strong coupling properties of N = 4 plasma as a

point of reference for analyzing/describing QCD plasma

◮ Eventually one may consider more realistic theories with AdS/CFT

duals...

7 / 22

slide-39
SLIDE 39

Why study N = 4 plasma?

◮ The applicability of using N = 4 plasma to model real world

phenomenae dependes on the questions asked..

◮ Use it as a theoretical laboratory where we may compute from ‘first

principles’ nonequilibrium nonperturbative dynamics

◮ Gain qualitative insight into the physics which is very difficult to

access using other methods

◮ Discover some universal properties? (like η/s) ◮ For N = 4 plasma the AdS/CFT correspondence is technically

simplest

◮ Use the results on strong coupling properties of N = 4 plasma as a

point of reference for analyzing/describing QCD plasma

◮ Eventually one may consider more realistic theories with AdS/CFT

duals...

7 / 22

slide-40
SLIDE 40

Why study N = 4 plasma?

◮ The applicability of using N = 4 plasma to model real world

phenomenae dependes on the questions asked..

◮ Use it as a theoretical laboratory where we may compute from ‘first

principles’ nonequilibrium nonperturbative dynamics

◮ Gain qualitative insight into the physics which is very difficult to

access using other methods

◮ Discover some universal properties? (like η/s) ◮ For N = 4 plasma the AdS/CFT correspondence is technically

simplest

◮ Use the results on strong coupling properties of N = 4 plasma as a

point of reference for analyzing/describing QCD plasma

◮ Eventually one may consider more realistic theories with AdS/CFT

duals...

7 / 22

slide-41
SLIDE 41

The AdS/CFT description Aim: Describe the time dependent evolving strongly coupled plasma system ↓ Describe it in terms of lightest degrees of freedom on the AdS side which are relevant at strong coupling ↓ ds2 = gµν(xρ, z)dxµdxν + dz2 z2 ≡ g 5D

αβdxαdxβ

↓ Compute the time-evolution by solving (numerically) 5D Einstein’s equations Rαβ − 1 2g 5D

αβR − 6 g 5D αβ = 0

↓ Extract physical observables (like T µν(xρ)) from the numerical geometry

8 / 22

slide-42
SLIDE 42

The AdS/CFT description Aim: Describe the time dependent evolving strongly coupled plasma system ↓ Describe it in terms of lightest degrees of freedom on the AdS side which are relevant at strong coupling ↓ ds2 = gµν(xρ, z)dxµdxν + dz2 z2 ≡ g 5D

αβdxαdxβ

↓ Compute the time-evolution by solving (numerically) 5D Einstein’s equations Rαβ − 1 2g 5D

αβR − 6 g 5D αβ = 0

↓ Extract physical observables (like T µν(xρ)) from the numerical geometry

8 / 22

slide-43
SLIDE 43

The AdS/CFT description Aim: Describe the time dependent evolving strongly coupled plasma system ↓ Describe it in terms of lightest degrees of freedom on the AdS side which are relevant at strong coupling ↓ ds2 = gµν(xρ, z)dxµdxν + dz2 z2 ≡ g 5D

αβdxαdxβ

↓ Compute the time-evolution by solving (numerically) 5D Einstein’s equations Rαβ − 1 2g 5D

αβR − 6 g 5D αβ = 0

↓ Extract physical observables (like T µν(xρ)) from the numerical geometry

8 / 22

slide-44
SLIDE 44

The AdS/CFT description Aim: Describe the time dependent evolving strongly coupled plasma system ↓ Describe it in terms of lightest degrees of freedom on the AdS side which are relevant at strong coupling ↓ ds2 = gµν(xρ, z)dxµdxν + dz2 z2 ≡ g 5D

αβdxαdxβ

↓ Compute the time-evolution by solving (numerically) 5D Einstein’s equations Rαβ − 1 2g 5D

αβR − 6 g 5D αβ = 0

↓ Extract physical observables (like T µν(xρ)) from the numerical geometry

8 / 22

slide-45
SLIDE 45

The AdS/CFT description Aim: Describe the time dependent evolving strongly coupled plasma system ↓ Describe it in terms of lightest degrees of freedom on the AdS side which are relevant at strong coupling ↓ ds2 = gµν(xρ, z)dxµdxν + dz2 z2 ≡ g 5D

αβdxαdxβ

↓ Compute the time-evolution by solving (numerically) 5D Einstein’s equations Rαβ − 1 2g 5D

αβR − 6 g 5D αβ = 0

↓ Extract physical observables (like T µν(xρ)) from the numerical geometry

8 / 22

slide-46
SLIDE 46

What physics can we extract?

◮ Asymptotics of gµν(xρ, z) at z ∼ 0 gives the

energy-momentum tensor Tµν(xρ) of the plasma system

◮ We can test whether Tµν(xρ) is of a

hydrodynamic form...

◮ We can check for local thermal equilibrium ◮ The area of the apparent horizon defines for

us the entropy density

◮ We observe some initial entropy

9 / 22

slide-47
SLIDE 47

What physics can we extract?

◮ Asymptotics of gµν(xρ, z) at z ∼ 0 gives the

energy-momentum tensor Tµν(xρ) of the plasma system

◮ We can test whether Tµν(xρ) is of a

hydrodynamic form...

◮ We can check for local thermal equilibrium ◮ The area of the apparent horizon defines for

us the entropy density

◮ We observe some initial entropy

9 / 22

slide-48
SLIDE 48

What physics can we extract?

◮ Asymptotics of gµν(xρ, z) at z ∼ 0 gives the

energy-momentum tensor Tµν(xρ) of the plasma system

◮ We can test whether Tµν(xρ) is of a

hydrodynamic form...

◮ We can check for local thermal equilibrium ◮ The area of the apparent horizon defines for

us the entropy density

◮ We observe some initial entropy

9 / 22

slide-49
SLIDE 49

What physics can we extract?

◮ Asymptotics of gµν(xρ, z) at z ∼ 0 gives the

energy-momentum tensor Tµν(xρ) of the plasma system

◮ We can test whether Tµν(xρ) is of a

hydrodynamic form...

◮ We can check for local thermal equilibrium ◮ The area of the apparent horizon defines for

us the entropy density

◮ We observe some initial entropy

9 / 22

slide-50
SLIDE 50

What physics can we extract?

◮ Asymptotics of gµν(xρ, z) at z ∼ 0 gives the

energy-momentum tensor Tµν(xρ) of the plasma system

◮ We can test whether Tµν(xρ) is of a

hydrodynamic form...

◮ We can check for local thermal equilibrium ◮ The area of the apparent horizon defines for

us the entropy density

◮ We observe some initial entropy

9 / 22

slide-51
SLIDE 51

What physics can we extract?

◮ Asymptotics of gµν(xρ, z) at z ∼ 0 gives the

energy-momentum tensor Tµν(xρ) of the plasma system

◮ We can test whether Tµν(xρ) is of a

hydrodynamic form...

◮ We can check for local thermal equilibrium ◮ The area of the apparent horizon defines for

us the entropy density

◮ We observe some initial entropy

9 / 22

slide-52
SLIDE 52

What physics can we extract?

◮ Asymptotics of gµν(xρ, z) at z ∼ 0 gives the

energy-momentum tensor Tµν(xρ) of the plasma system

◮ We can test whether Tµν(xρ) is of a

hydrodynamic form...

◮ We can check for local thermal equilibrium ◮ The area of the apparent horizon defines for

us the entropy density

◮ We observe some initial entropy

9 / 22

slide-53
SLIDE 53

What physics can we extract?

◮ Asymptotics of gµν(xρ, z) at z ∼ 0 gives the

energy-momentum tensor Tµν(xρ) of the plasma system

◮ We can test whether Tµν(xρ) is of a

hydrodynamic form...

◮ We can check for local thermal equilibrium ◮ The area of the apparent horizon defines for

us the entropy density

◮ We observe some initial entropy

9 / 22

slide-54
SLIDE 54

What physics can we extract?

◮ Asymptotics of gµν(xρ, z) at z ∼ 0 gives the

energy-momentum tensor Tµν(xρ) of the plasma system

◮ We can test whether Tµν(xρ) is of a

hydrodynamic form...

◮ We can check for local thermal equilibrium ◮ The area of the apparent horizon defines for

us the entropy density

◮ We observe some initial entropy

9 / 22

slide-55
SLIDE 55

Key question: Understand the features of the far- from equilibrium stage of the dynam- ics of the strongly coupled plasma system

10 / 22

slide-56
SLIDE 56

Key question: Understand the features of the far- from equilibrium stage of the dynam- ics of the strongly coupled plasma system

10 / 22

slide-57
SLIDE 57

Boost-invariant flow Bjorken ’83 Assume a flow that is invariant under longitudinal boosts and does not depend on the transverse coordinates.

◮ In a conformal theory, T µ µ = 0 and ∂µT µν = 0 determine, under the

above assumptions, the energy-momentum tensor completely in terms of a single function ε(τ), the energy density at mid-rapidity.

◮ The longitudinal and transverse pressures are then given by

pL = −ε − τ d dτ ε and pT = ε + 1 2τ d dτ ε .

◮ The assumptions of symmetry fix uniquely the flow velocity

11 / 22

slide-58
SLIDE 58

Boost-invariant flow Bjorken ’83 Assume a flow that is invariant under longitudinal boosts and does not depend on the transverse coordinates.

◮ In a conformal theory, T µ µ = 0 and ∂µT µν = 0 determine, under the

above assumptions, the energy-momentum tensor completely in terms of a single function ε(τ), the energy density at mid-rapidity.

◮ The longitudinal and transverse pressures are then given by

pL = −ε − τ d dτ ε and pT = ε + 1 2τ d dτ ε .

◮ The assumptions of symmetry fix uniquely the flow velocity

11 / 22

slide-59
SLIDE 59

Boost-invariant flow Bjorken ’83 Assume a flow that is invariant under longitudinal boosts and does not depend on the transverse coordinates.

◮ In a conformal theory, T µ µ = 0 and ∂µT µν = 0 determine, under the

above assumptions, the energy-momentum tensor completely in terms of a single function ε(τ), the energy density at mid-rapidity.

◮ The longitudinal and transverse pressures are then given by

pL = −ε − τ d dτ ε and pT = ε + 1 2τ d dτ ε .

◮ The assumptions of symmetry fix uniquely the flow velocity

11 / 22

slide-60
SLIDE 60

Boost-invariant flow Bjorken ’83 Assume a flow that is invariant under longitudinal boosts and does not depend on the transverse coordinates.

◮ In a conformal theory, T µ µ = 0 and ∂µT µν = 0 determine, under the

above assumptions, the energy-momentum tensor completely in terms of a single function ε(τ), the energy density at mid-rapidity.

◮ The longitudinal and transverse pressures are then given by

pL = −ε − τ d dτ ε and pT = ε + 1 2τ d dτ ε .

◮ The assumptions of symmetry fix uniquely the flow velocity

11 / 22

slide-61
SLIDE 61

Large τ behaviour of ε(τ)

◮ Structure of the analytical result for large τ:

ε(τ) = 1 τ

4 3 −

2 2

1 2 3 3 4

1 τ 2 +1 + 2 log 2 12 √ 3 1 τ

8 3 +−3 + 2π2 + 24 log 2 − 24 log2 2

324 · 2

1 2 3 1 4

1 τ

10 3 +. . .

RJ, Peschanski; Nakamura, S-J Sin; RJ; RJ, Heller; Heller

◮ Leading term — perfect fluid behaviour

second term — 1st order viscous hydrodynamics third term — 2nd order viscous hydrodynamics fourth term — 3rd order viscous hydrodynamics...

◮ In general:

ε(τ) =

  • n=2

εn τ

2n 3

◮ Currently we know 240 terms in this expansion

Heller, RJ, Witaszczyk

◮ The hydrodynamic series is only asymptotic and has zero radius of

convergence...

Heller, RJ, Witaszczyk 1302.0697 [PRL 110 (2013) 211602]

12 / 22

slide-62
SLIDE 62

Large τ behaviour of ε(τ)

◮ Structure of the analytical result for large τ:

ε(τ) = 1 τ

4 3 −

2 2

1 2 3 3 4

1 τ 2 +1 + 2 log 2 12 √ 3 1 τ

8 3 +−3 + 2π2 + 24 log 2 − 24 log2 2

324 · 2

1 2 3 1 4

1 τ

10 3 +. . .

RJ, Peschanski; Nakamura, S-J Sin; RJ; RJ, Heller; Heller

◮ Leading term — perfect fluid behaviour

second term — 1st order viscous hydrodynamics third term — 2nd order viscous hydrodynamics fourth term — 3rd order viscous hydrodynamics...

◮ In general:

ε(τ) =

  • n=2

εn τ

2n 3

◮ Currently we know 240 terms in this expansion

Heller, RJ, Witaszczyk

◮ The hydrodynamic series is only asymptotic and has zero radius of

convergence...

Heller, RJ, Witaszczyk 1302.0697 [PRL 110 (2013) 211602]

12 / 22

slide-63
SLIDE 63

Large τ behaviour of ε(τ)

◮ Structure of the analytical result for large τ:

ε(τ) = 1 τ

4 3 −

2 2

1 2 3 3 4

1 τ 2 +1 + 2 log 2 12 √ 3 1 τ

8 3 +−3 + 2π2 + 24 log 2 − 24 log2 2

324 · 2

1 2 3 1 4

1 τ

10 3 +. . .

RJ, Peschanski; Nakamura, S-J Sin; RJ; RJ, Heller; Heller

◮ Leading term — perfect fluid behaviour

second term — 1st order viscous hydrodynamics third term — 2nd order viscous hydrodynamics fourth term — 3rd order viscous hydrodynamics...

◮ In general:

ε(τ) =

  • n=2

εn τ

2n 3

◮ Currently we know 240 terms in this expansion

Heller, RJ, Witaszczyk

◮ The hydrodynamic series is only asymptotic and has zero radius of

convergence...

Heller, RJ, Witaszczyk 1302.0697 [PRL 110 (2013) 211602]

12 / 22

slide-64
SLIDE 64

Large τ behaviour of ε(τ)

◮ Structure of the analytical result for large τ:

ε(τ) = 1 τ

4 3 −

2 2

1 2 3 3 4

1 τ 2 +1 + 2 log 2 12 √ 3 1 τ

8 3 +−3 + 2π2 + 24 log 2 − 24 log2 2

324 · 2

1 2 3 1 4

1 τ

10 3 +. . .

RJ, Peschanski; Nakamura, S-J Sin; RJ; RJ, Heller; Heller

◮ Leading term — perfect fluid behaviour

second term — 1st order viscous hydrodynamics third term — 2nd order viscous hydrodynamics fourth term — 3rd order viscous hydrodynamics...

◮ In general:

ε(τ) =

  • n=2

εn τ

2n 3

◮ Currently we know 240 terms in this expansion

Heller, RJ, Witaszczyk

◮ The hydrodynamic series is only asymptotic and has zero radius of

convergence...

Heller, RJ, Witaszczyk 1302.0697 [PRL 110 (2013) 211602]

12 / 22

slide-65
SLIDE 65

Large τ behaviour of ε(τ)

◮ Structure of the analytical result for large τ:

ε(τ) = 1 τ

4 3 −

2 2

1 2 3 3 4

1 τ 2 +1 + 2 log 2 12 √ 3 1 τ

8 3 +−3 + 2π2 + 24 log 2 − 24 log2 2

324 · 2

1 2 3 1 4

1 τ

10 3 +. . .

RJ, Peschanski; Nakamura, S-J Sin; RJ; RJ, Heller; Heller

◮ Leading term — perfect fluid behaviour

second term — 1st order viscous hydrodynamics third term — 2nd order viscous hydrodynamics fourth term — 3rd order viscous hydrodynamics...

◮ In general:

ε(τ) =

  • n=2

εn τ

2n 3

◮ Currently we know 240 terms in this expansion

Heller, RJ, Witaszczyk

◮ The hydrodynamic series is only asymptotic and has zero radius of

convergence...

Heller, RJ, Witaszczyk 1302.0697 [PRL 110 (2013) 211602]

12 / 22

slide-66
SLIDE 66

Large τ behaviour of ε(τ)

◮ Structure of the analytical result for large τ:

ε(τ) = 1 τ

4 3 −

2 2

1 2 3 3 4

1 τ 2 +1 + 2 log 2 12 √ 3 1 τ

8 3 +−3 + 2π2 + 24 log 2 − 24 log2 2

324 · 2

1 2 3 1 4

1 τ

10 3 +. . .

RJ, Peschanski; Nakamura, S-J Sin; RJ; RJ, Heller; Heller

◮ Leading term — perfect fluid behaviour

second term — 1st order viscous hydrodynamics third term — 2nd order viscous hydrodynamics fourth term — 3rd order viscous hydrodynamics...

◮ In general:

ε(τ) =

  • n=2

εn τ

2n 3

◮ Currently we know 240 terms in this expansion

Heller, RJ, Witaszczyk

◮ The hydrodynamic series is only asymptotic and has zero radius of

convergence...

Heller, RJ, Witaszczyk 1302.0697 [PRL 110 (2013) 211602]

12 / 22

slide-67
SLIDE 67

Large τ behaviour of ε(τ)

◮ Structure of the analytical result for large τ:

ε(τ) = 1 τ

4 3 −

2 2

1 2 3 3 4

1 τ 2 +1 + 2 log 2 12 √ 3 1 τ

8 3 +−3 + 2π2 + 24 log 2 − 24 log2 2

324 · 2

1 2 3 1 4

1 τ

10 3 +. . .

RJ, Peschanski; Nakamura, S-J Sin; RJ; RJ, Heller; Heller

◮ Leading term — perfect fluid behaviour

second term — 1st order viscous hydrodynamics third term — 2nd order viscous hydrodynamics fourth term — 3rd order viscous hydrodynamics...

◮ In general:

ε(τ) =

  • n=2

εn τ

2n 3

◮ Currently we know 240 terms in this expansion

Heller, RJ, Witaszczyk

◮ The hydrodynamic series is only asymptotic and has zero radius of

convergence...

Heller, RJ, Witaszczyk 1302.0697 [PRL 110 (2013) 211602]

12 / 22

slide-68
SLIDE 68

Large τ behaviour of ε(τ)

◮ Structure of the analytical result for large τ:

ε(τ) = 1 τ

4 3 −

2 2

1 2 3 3 4

1 τ 2 +1 + 2 log 2 12 √ 3 1 τ

8 3 +−3 + 2π2 + 24 log 2 − 24 log2 2

324 · 2

1 2 3 1 4

1 τ

10 3 +. . .

RJ, Peschanski; Nakamura, S-J Sin; RJ; RJ, Heller; Heller

◮ Leading term — perfect fluid behaviour

second term — 1st order viscous hydrodynamics third term — 2nd order viscous hydrodynamics fourth term — 3rd order viscous hydrodynamics...

◮ In general:

ε(τ) =

  • n=2

εn τ

2n 3

◮ Currently we know 240 terms in this expansion

Heller, RJ, Witaszczyk

◮ The hydrodynamic series is only asymptotic and has zero radius of

convergence...

Heller, RJ, Witaszczyk 1302.0697 [PRL 110 (2013) 211602]

12 / 22

slide-69
SLIDE 69

Remarks:

◮ In order to study far-from equilibrium behaviour for small τ we have

to use numerical relativity methods

◮ We get rid of the dependence on the number of degrees of freedom

by parametrizing the energy density through an effective temperature given by ε(τ) = 3 8N2

c π2T 4 eff (τ) ◮ Previously, we normalized our initial data by setting

Teff (τ = 0) = 1 but this is generically unknown in realistic heavy-ion collisions...

◮ It is much better to fix the normalization through the hydrodynamic

tail... πTeff (τ) ∼ 1 τ

1 3 in the τ → ∞ limit

The coefficient ‘1’ fixes the units of τ.

13 / 22

slide-70
SLIDE 70

Remarks:

◮ In order to study far-from equilibrium behaviour for small τ we have

to use numerical relativity methods

◮ We get rid of the dependence on the number of degrees of freedom

by parametrizing the energy density through an effective temperature given by ε(τ) = 3 8N2

c π2T 4 eff (τ) ◮ Previously, we normalized our initial data by setting

Teff (τ = 0) = 1 but this is generically unknown in realistic heavy-ion collisions...

◮ It is much better to fix the normalization through the hydrodynamic

tail... πTeff (τ) ∼ 1 τ

1 3 in the τ → ∞ limit

The coefficient ‘1’ fixes the units of τ.

13 / 22

slide-71
SLIDE 71

Remarks:

◮ In order to study far-from equilibrium behaviour for small τ we have

to use numerical relativity methods

◮ We get rid of the dependence on the number of degrees of freedom

by parametrizing the energy density through an effective temperature given by ε(τ) = 3 8N2

c π2T 4 eff (τ) ◮ Previously, we normalized our initial data by setting

Teff (τ = 0) = 1 but this is generically unknown in realistic heavy-ion collisions...

◮ It is much better to fix the normalization through the hydrodynamic

tail... πTeff (τ) ∼ 1 τ

1 3 in the τ → ∞ limit

The coefficient ‘1’ fixes the units of τ.

13 / 22

slide-72
SLIDE 72

Remarks:

◮ In order to study far-from equilibrium behaviour for small τ we have

to use numerical relativity methods

◮ We get rid of the dependence on the number of degrees of freedom

by parametrizing the energy density through an effective temperature given by ε(τ) = 3 8N2

c π2T 4 eff (τ) ◮ Previously, we normalized our initial data by setting

Teff (τ = 0) = 1 but this is generically unknown in realistic heavy-ion collisions...

◮ It is much better to fix the normalization through the hydrodynamic

tail... πTeff (τ) ∼ 1 τ

1 3 in the τ → ∞ limit

The coefficient ‘1’ fixes the units of τ.

13 / 22

slide-73
SLIDE 73

Remarks:

◮ In order to study far-from equilibrium behaviour for small τ we have

to use numerical relativity methods

◮ We get rid of the dependence on the number of degrees of freedom

by parametrizing the energy density through an effective temperature given by ε(τ) = 3 8N2

c π2T 4 eff (τ) ◮ Previously, we normalized our initial data by setting

Teff (τ = 0) = 1 but this is generically unknown in realistic heavy-ion collisions...

◮ It is much better to fix the normalization through the hydrodynamic

tail... πTeff (τ) ∼ 1 τ

1 3 in the τ → ∞ limit

The coefficient ‘1’ fixes the units of τ.

13 / 22

slide-74
SLIDE 74

Remarks:

◮ In order to study far-from equilibrium behaviour for small τ we have

to use numerical relativity methods

◮ We get rid of the dependence on the number of degrees of freedom

by parametrizing the energy density through an effective temperature given by ε(τ) = 3 8N2

c π2T 4 eff (τ) ◮ Previously, we normalized our initial data by setting

Teff (τ = 0) = 1 but this is generically unknown in realistic heavy-ion collisions...

◮ It is much better to fix the normalization through the hydrodynamic

tail... πTeff (τ) ∼ 1 τ

1 3 in the τ → ∞ limit

The coefficient ‘1’ fixes the units of τ.

13 / 22

slide-75
SLIDE 75

Effective temperature Teff as a function of τ green line: 3rd order hydro red line: Borel resummed hydro

◮ Very clear transition to a hydrodynamic behaviour ◮ Very little information on the initial energy density at τ = 0 (unless

we have some specific information on the initial state)

14 / 22

slide-76
SLIDE 76

Effective temperature Teff as a function of τ green line: 3rd order hydro red line: Borel resummed hydro

◮ Very clear transition to a hydrodynamic behaviour ◮ Very little information on the initial energy density at τ = 0 (unless

we have some specific information on the initial state)

14 / 22

slide-77
SLIDE 77

Effective temperature Teff as a function of τ green line: 3rd order hydro red line: Borel resummed hydro

◮ Very clear transition to a hydrodynamic behaviour ◮ Very little information on the initial energy density at τ = 0 (unless

we have some specific information on the initial state)

14 / 22

slide-78
SLIDE 78

Effective temperature Teff as a function of τ green line: 3rd order hydro red line: Borel resummed hydro

◮ Very clear transition to a hydrodynamic behaviour ◮ Very little information on the initial energy density at τ = 0 (unless

we have some specific information on the initial state)

14 / 22

slide-79
SLIDE 79

Effective temperature Teff as a function of τ green line: 3rd order hydro red line: Borel resummed hydro

◮ Very clear transition to a hydrodynamic behaviour ◮ Very little information on the initial energy density at τ = 0 (unless

we have some specific information on the initial state)

14 / 22

slide-80
SLIDE 80

Effective temperature Teff as a function of τ green line: 3rd order hydro red line: Borel resummed hydro

◮ Very clear transition to a hydrodynamic behaviour ◮ Very little information on the initial energy density at τ = 0 (unless

we have some specific information on the initial state)

14 / 22

slide-81
SLIDE 81

Transition to hydrodynamics – hydrodynamization

  • 1. Form the dimensionless product w ≡ Teff · τ
  • 2. For all initial conditions considered, viscous hydrodynamics works

very well for w ≡ Teff · τ > 0.7 (natural values for RHIC: (τ0 = 0.25 fm, T0 = 500 MeV ) assumed in [Broniowski, Chojnacki, Florkowski, Kisiel] correspond to w = 0.63)

  • 3. The plasma system is described by viscous hydrodynamics even

though it is not in true thermal equilibrium — there is still a sizable pressure anisotropy ∆pL ≡ 1 − pL ε/3 ∼ 0.7

15 / 22

slide-82
SLIDE 82

Transition to hydrodynamics – hydrodynamization

  • 1. Form the dimensionless product w ≡ Teff · τ
  • 2. For all initial conditions considered, viscous hydrodynamics works

very well for w ≡ Teff · τ > 0.7 (natural values for RHIC: (τ0 = 0.25 fm, T0 = 500 MeV ) assumed in [Broniowski, Chojnacki, Florkowski, Kisiel] correspond to w = 0.63)

  • 3. The plasma system is described by viscous hydrodynamics even

though it is not in true thermal equilibrium — there is still a sizable pressure anisotropy ∆pL ≡ 1 − pL ε/3 ∼ 0.7

15 / 22

slide-83
SLIDE 83

Transition to hydrodynamics – hydrodynamization

  • 1. Form the dimensionless product w ≡ Teff · τ
  • 2. For all initial conditions considered, viscous hydrodynamics works

very well for w ≡ Teff · τ > 0.7 (natural values for RHIC: (τ0 = 0.25 fm, T0 = 500 MeV ) assumed in [Broniowski, Chojnacki, Florkowski, Kisiel] correspond to w = 0.63)

  • 3. The plasma system is described by viscous hydrodynamics even

though it is not in true thermal equilibrium — there is still a sizable pressure anisotropy ∆pL ≡ 1 − pL ε/3 ∼ 0.7

15 / 22

slide-84
SLIDE 84

Transition to hydrodynamics – hydrodynamization

  • 1. Form the dimensionless product w ≡ Teff · τ
  • 2. For all initial conditions considered, viscous hydrodynamics works

very well for w ≡ Teff · τ > 0.7 (natural values for RHIC: (τ0 = 0.25 fm, T0 = 500 MeV ) assumed in [Broniowski, Chojnacki, Florkowski, Kisiel] correspond to w = 0.63)

  • 3. The plasma system is described by viscous hydrodynamics even

though it is not in true thermal equilibrium — there is still a sizable pressure anisotropy ∆pL ≡ 1 − pL ε/3 ∼ 0.7

15 / 22

slide-85
SLIDE 85

Transition to hydrodynamics – hydrodynamization

  • 1. Form the dimensionless product w ≡ Teff · τ
  • 2. For all initial conditions considered, viscous hydrodynamics works

very well for w ≡ Teff · τ > 0.7 (natural values for RHIC: (τ0 = 0.25 fm, T0 = 500 MeV ) assumed in [Broniowski, Chojnacki, Florkowski, Kisiel] correspond to w = 0.63)

  • 3. The plasma system is described by viscous hydrodynamics even

though it is not in true thermal equilibrium — there is still a sizable pressure anisotropy ∆pL ≡ 1 − pL ε/3 ∼ 0.7

15 / 22

slide-86
SLIDE 86

Transition to hydrodynamics – hydrodynamization

  • 1. Form the dimensionless product w ≡ Teff · τ
  • 2. For all initial conditions considered, viscous hydrodynamics works

very well for w ≡ Teff · τ > 0.7 (natural values for RHIC: (τ0 = 0.25 fm, T0 = 500 MeV ) assumed in [Broniowski, Chojnacki, Florkowski, Kisiel] correspond to w = 0.63)

  • 3. The plasma system is described by viscous hydrodynamics even

though it is not in true thermal equilibrium — there is still a sizable pressure anisotropy ∆pL ≡ 1 − pL ε/3 ∼ 0.7

15 / 22

slide-87
SLIDE 87

Key observation: Hydrodynamization = Thermalization

16 / 22

slide-88
SLIDE 88

Key observation: Hydrodynamization = Thermalization

16 / 22

slide-89
SLIDE 89

Role of initial entropy Initial entropy turns out to be a key characterization of the initial state There is a clear correlation of produced entropy with the initial entropy... Similar conclusion holds for e.g. (effective) thermalization time (understood here as the transition to a viscous hydrodynamic description)

17 / 22

slide-90
SLIDE 90

Role of initial entropy Initial entropy turns out to be a key characterization of the initial state There is a clear correlation of produced entropy with the initial entropy... Similar conclusion holds for e.g. (effective) thermalization time (understood here as the transition to a viscous hydrodynamic description)

17 / 22

slide-91
SLIDE 91

Role of initial entropy Initial entropy turns out to be a key characterization of the initial state There is a clear correlation of produced entropy with the initial entropy... Similar conclusion holds for e.g. (effective) thermalization time (understood here as the transition to a viscous hydrodynamic description)

17 / 22

slide-92
SLIDE 92

Role of initial entropy Initial entropy turns out to be a key characterization of the initial state There is a clear correlation of produced entropy with the initial entropy... Similar conclusion holds for e.g. (effective) thermalization time (understood here as the transition to a viscous hydrodynamic description)

17 / 22

slide-93
SLIDE 93

Recall Teff (τ) How to model deviations from (all-order) hydrodynamics?

18 / 22

slide-94
SLIDE 94

Recall Teff (τ) How to model deviations from (all-order) hydrodynamics?

18 / 22

slide-95
SLIDE 95

Recall Teff (τ) How to model deviations from (all-order) hydrodynamics?

18 / 22

slide-96
SLIDE 96

How to model additional non-hydrodynamic degrees of freedom?

◮ Is there a simple phenomenological model simpler than 5D Einstein’s

equations?? Tµν(T, uρ) ∼ hydrodynamics Tµν(T, uρ, ???) ∼ hydrodynamics + additional DOF c.f. anisotropic hydrodynamics of Florkowski, Strickland and collaborators

◮ Can we get information on the possible (number of) degrees of

freedom from our knowledge of a) resummed hydrodynamics b) a large set of diverse numerical profiles

19 / 22

slide-97
SLIDE 97

How to model additional non-hydrodynamic degrees of freedom?

◮ Is there a simple phenomenological model simpler than 5D Einstein’s

equations?? Tµν(T, uρ) ∼ hydrodynamics Tµν(T, uρ, ???) ∼ hydrodynamics + additional DOF c.f. anisotropic hydrodynamics of Florkowski, Strickland and collaborators

◮ Can we get information on the possible (number of) degrees of

freedom from our knowledge of a) resummed hydrodynamics b) a large set of diverse numerical profiles

19 / 22

slide-98
SLIDE 98

How to model additional non-hydrodynamic degrees of freedom?

◮ Is there a simple phenomenological model simpler than 5D Einstein’s

equations?? Tµν(T, uρ) ∼ hydrodynamics Tµν(T, uρ, ???) ∼ hydrodynamics + additional DOF c.f. anisotropic hydrodynamics of Florkowski, Strickland and collaborators

◮ Can we get information on the possible (number of) degrees of

freedom from our knowledge of a) resummed hydrodynamics b) a large set of diverse numerical profiles

19 / 22

slide-99
SLIDE 99

How to model additional non-hydrodynamic degrees of freedom?

◮ Is there a simple phenomenological model simpler than 5D Einstein’s

equations?? Tµν(T, uρ) ∼ hydrodynamics Tµν(T, uρ, ???) ∼ hydrodynamics + additional DOF c.f. anisotropic hydrodynamics of Florkowski, Strickland and collaborators

◮ Can we get information on the possible (number of) degrees of

freedom from our knowledge of a) resummed hydrodynamics b) a large set of diverse numerical profiles

19 / 22

slide-100
SLIDE 100

How to model additional non-hydrodynamic degrees of freedom?

◮ Is there a simple phenomenological model simpler than 5D Einstein’s

equations?? Tµν(T, uρ) ∼ hydrodynamics Tµν(T, uρ, ???) ∼ hydrodynamics + additional DOF c.f. anisotropic hydrodynamics of Florkowski, Strickland and collaborators

◮ Can we get information on the possible (number of) degrees of

freedom from our knowledge of a) resummed hydrodynamics b) a large set of diverse numerical profiles

19 / 22

slide-101
SLIDE 101

Quasinormal modes

◮ On the gravity side, deviations from hydrodynamics may be

represented by metric perturbations (quasinormal modes)

◮ Each quasinormal mode represents an independent degree of

freedom from the 4D perspective...

◮ The generic structure of QNM modes for a boost-invariant flow

(including first viscous corrections) δε(τ) ∼ τ −2e−iωQNM

  • πT(τ)dτ

where ωQNM = ωR − iωI

◮ One can estimate that s =

τ

0 πT(τ)dτ at the transition to

hydrodynamics would set the scale for how many QNM would be relevant there...

◮ It turns out that s = 1.6...3 and Im ωQNM = 2.75, 4.76, 6.77, ... ◮ A few additional DOF might suffice?

20 / 22

slide-102
SLIDE 102

Quasinormal modes

◮ On the gravity side, deviations from hydrodynamics may be

represented by metric perturbations (quasinormal modes)

◮ Each quasinormal mode represents an independent degree of

freedom from the 4D perspective...

◮ The generic structure of QNM modes for a boost-invariant flow

(including first viscous corrections) δε(τ) ∼ τ −2e−iωQNM

  • πT(τ)dτ

where ωQNM = ωR − iωI

◮ One can estimate that s =

τ

0 πT(τ)dτ at the transition to

hydrodynamics would set the scale for how many QNM would be relevant there...

◮ It turns out that s = 1.6...3 and Im ωQNM = 2.75, 4.76, 6.77, ... ◮ A few additional DOF might suffice?

20 / 22

slide-103
SLIDE 103

Quasinormal modes

◮ On the gravity side, deviations from hydrodynamics may be

represented by metric perturbations (quasinormal modes)

◮ Each quasinormal mode represents an independent degree of

freedom from the 4D perspective...

◮ The generic structure of QNM modes for a boost-invariant flow

(including first viscous corrections) δε(τ) ∼ τ −2e−iωQNM

  • πT(τ)dτ

where ωQNM = ωR − iωI

◮ One can estimate that s =

τ

0 πT(τ)dτ at the transition to

hydrodynamics would set the scale for how many QNM would be relevant there...

◮ It turns out that s = 1.6...3 and Im ωQNM = 2.75, 4.76, 6.77, ... ◮ A few additional DOF might suffice?

20 / 22

slide-104
SLIDE 104

Quasinormal modes

◮ On the gravity side, deviations from hydrodynamics may be

represented by metric perturbations (quasinormal modes)

◮ Each quasinormal mode represents an independent degree of

freedom from the 4D perspective...

◮ The generic structure of QNM modes for a boost-invariant flow

(including first viscous corrections) δε(τ) ∼ τ −2e−iωQNM

  • πT(τ)dτ

where ωQNM = ωR − iωI

◮ One can estimate that s =

τ

0 πT(τ)dτ at the transition to

hydrodynamics would set the scale for how many QNM would be relevant there...

◮ It turns out that s = 1.6...3 and Im ωQNM = 2.75, 4.76, 6.77, ... ◮ A few additional DOF might suffice?

20 / 22

slide-105
SLIDE 105

Quasinormal modes

◮ On the gravity side, deviations from hydrodynamics may be

represented by metric perturbations (quasinormal modes)

◮ Each quasinormal mode represents an independent degree of

freedom from the 4D perspective...

◮ The generic structure of QNM modes for a boost-invariant flow

(including first viscous corrections) δε(τ) ∼ τ −2e−iωQNM

  • πT(τ)dτ

where ωQNM = ωR − iωI

◮ One can estimate that s =

τ

0 πT(τ)dτ at the transition to

hydrodynamics would set the scale for how many QNM would be relevant there...

◮ It turns out that s = 1.6...3 and Im ωQNM = 2.75, 4.76, 6.77, ... ◮ A few additional DOF might suffice?

20 / 22

slide-106
SLIDE 106

Quasinormal modes

◮ On the gravity side, deviations from hydrodynamics may be

represented by metric perturbations (quasinormal modes)

◮ Each quasinormal mode represents an independent degree of

freedom from the 4D perspective...

◮ The generic structure of QNM modes for a boost-invariant flow

(including first viscous corrections) δε(τ) ∼ τ −2e−iωQNM

  • πT(τ)dτ

where ωQNM = ωR − iωI

◮ One can estimate that s =

τ

0 πT(τ)dτ at the transition to

hydrodynamics would set the scale for how many QNM would be relevant there...

◮ It turns out that s = 1.6...3 and Im ωQNM = 2.75, 4.76, 6.77, ... ◮ A few additional DOF might suffice?

20 / 22

slide-107
SLIDE 107

Quasinormal modes

◮ On the gravity side, deviations from hydrodynamics may be

represented by metric perturbations (quasinormal modes)

◮ Each quasinormal mode represents an independent degree of

freedom from the 4D perspective...

◮ The generic structure of QNM modes for a boost-invariant flow

(including first viscous corrections) δε(τ) ∼ τ −2e−iωQNM

  • πT(τ)dτ

where ωQNM = ωR − iωI

◮ One can estimate that s =

τ

0 πT(τ)dτ at the transition to

hydrodynamics would set the scale for how many QNM would be relevant there...

◮ It turns out that s = 1.6...3 and Im ωQNM = 2.75, 4.76, 6.77, ... ◮ A few additional DOF might suffice?

20 / 22

slide-108
SLIDE 108

How to write an equation of motion for a scalar nonhydrodynamic degree of freedom (e.g. tr F 2) in a generic hydrodynamic background?

◮ The scalar dof corresponds to a scalar QNM with frequencies

ωQNM = ωR − iωI

◮ Key feature: the frequencies have only very mild dependence on

the spatial momentum — the dynamics seems ‘ultralocal’

◮ We may write the equation of motion in a generic hydrodynamic flow

D2φ + 2ωIDφ +

  • ω2

I + ω2 R

  • φ = 0

where D ≡ 1 T uµ∂µ Extension to nonhydrodynamic modes of Tµν in progress...

21 / 22

slide-109
SLIDE 109

How to write an equation of motion for a scalar nonhydrodynamic degree of freedom (e.g. tr F 2) in a generic hydrodynamic background?

◮ The scalar dof corresponds to a scalar QNM with frequencies

ωQNM = ωR − iωI

◮ Key feature: the frequencies have only very mild dependence on

the spatial momentum — the dynamics seems ‘ultralocal’

◮ We may write the equation of motion in a generic hydrodynamic flow

D2φ + 2ωIDφ +

  • ω2

I + ω2 R

  • φ = 0

where D ≡ 1 T uµ∂µ Extension to nonhydrodynamic modes of Tµν in progress...

21 / 22

slide-110
SLIDE 110

How to write an equation of motion for a scalar nonhydrodynamic degree of freedom (e.g. tr F 2) in a generic hydrodynamic background?

◮ The scalar dof corresponds to a scalar QNM with frequencies

ωQNM = ωR − iωI

◮ Key feature: the frequencies have only very mild dependence on

the spatial momentum — the dynamics seems ‘ultralocal’

◮ We may write the equation of motion in a generic hydrodynamic flow

D2φ + 2ωIDφ +

  • ω2

I + ω2 R

  • φ = 0

where D ≡ 1 T uµ∂µ Extension to nonhydrodynamic modes of Tµν in progress...

21 / 22

slide-111
SLIDE 111

How to write an equation of motion for a scalar nonhydrodynamic degree of freedom (e.g. tr F 2) in a generic hydrodynamic background?

◮ The scalar dof corresponds to a scalar QNM with frequencies

ωQNM = ωR − iωI

◮ Key feature: the frequencies have only very mild dependence on

the spatial momentum — the dynamics seems ‘ultralocal’

◮ We may write the equation of motion in a generic hydrodynamic flow

D2φ + 2ωIDφ +

  • ω2

I + ω2 R

  • φ = 0

where D ≡ 1 T uµ∂µ Extension to nonhydrodynamic modes of Tµν in progress...

21 / 22

slide-112
SLIDE 112

How to write an equation of motion for a scalar nonhydrodynamic degree of freedom (e.g. tr F 2) in a generic hydrodynamic background?

◮ The scalar dof corresponds to a scalar QNM with frequencies

ωQNM = ωR − iωI

◮ Key feature: the frequencies have only very mild dependence on

the spatial momentum — the dynamics seems ‘ultralocal’

◮ We may write the equation of motion in a generic hydrodynamic flow

D2φ + 2ωIDφ +

  • ω2

I + ω2 R

  • φ = 0

where D ≡ 1 T uµ∂µ Extension to nonhydrodynamic modes of Tµν in progress...

21 / 22

slide-113
SLIDE 113

How to write an equation of motion for a scalar nonhydrodynamic degree of freedom (e.g. tr F 2) in a generic hydrodynamic background?

◮ The scalar dof corresponds to a scalar QNM with frequencies

ωQNM = ωR − iωI

◮ Key feature: the frequencies have only very mild dependence on

the spatial momentum — the dynamics seems ‘ultralocal’

◮ We may write the equation of motion in a generic hydrodynamic flow

D2φ + 2ωIDφ +

  • ω2

I + ω2 R

  • φ = 0

where D ≡ 1 T uµ∂µ Extension to nonhydrodynamic modes of Tµν in progress...

21 / 22

slide-114
SLIDE 114

How to write an equation of motion for a scalar nonhydrodynamic degree of freedom (e.g. tr F 2) in a generic hydrodynamic background?

◮ The scalar dof corresponds to a scalar QNM with frequencies

ωQNM = ωR − iωI

◮ Key feature: the frequencies have only very mild dependence on

the spatial momentum — the dynamics seems ‘ultralocal’

◮ We may write the equation of motion in a generic hydrodynamic flow

D2φ + 2ωIDφ +

  • ω2

I + ω2 R

  • φ = 0

where D ≡ 1 T uµ∂µ Extension to nonhydrodynamic modes of Tµν in progress...

21 / 22

slide-115
SLIDE 115

Conclusions

◮ AdS/CFT provides a very general framework for studying

time-dependent dynamical processes

◮ The AdS/CFT methods do not presuppose hydrodynamics so are

applicable even to very out-of-equilibrium configurations

◮ AdS/CFT may fill in gaps in our knowledge of the early

nonequilibrium stage of plasma evolution

◮ Thermalization = hydrodynamization ◮ Simple dimensionless criterion for applicability of hydrodynamics ◮ Important role of ‘initial entropy’ as a characterization of the initial

state

◮ One can perhaps understand better the dynamics of lowest

nonhydrodynamic degrees of freedom from the 4D perspective

◮ Key role of quasinormal frequencies...

22 / 22

slide-116
SLIDE 116

Conclusions

◮ AdS/CFT provides a very general framework for studying

time-dependent dynamical processes

◮ The AdS/CFT methods do not presuppose hydrodynamics so are

applicable even to very out-of-equilibrium configurations

◮ AdS/CFT may fill in gaps in our knowledge of the early

nonequilibrium stage of plasma evolution

◮ Thermalization = hydrodynamization ◮ Simple dimensionless criterion for applicability of hydrodynamics ◮ Important role of ‘initial entropy’ as a characterization of the initial

state

◮ One can perhaps understand better the dynamics of lowest

nonhydrodynamic degrees of freedom from the 4D perspective

◮ Key role of quasinormal frequencies...

22 / 22

slide-117
SLIDE 117

Conclusions

◮ AdS/CFT provides a very general framework for studying

time-dependent dynamical processes

◮ The AdS/CFT methods do not presuppose hydrodynamics so are

applicable even to very out-of-equilibrium configurations

◮ AdS/CFT may fill in gaps in our knowledge of the early

nonequilibrium stage of plasma evolution

◮ Thermalization = hydrodynamization ◮ Simple dimensionless criterion for applicability of hydrodynamics ◮ Important role of ‘initial entropy’ as a characterization of the initial

state

◮ One can perhaps understand better the dynamics of lowest

nonhydrodynamic degrees of freedom from the 4D perspective

◮ Key role of quasinormal frequencies...

22 / 22

slide-118
SLIDE 118

Conclusions

◮ AdS/CFT provides a very general framework for studying

time-dependent dynamical processes

◮ The AdS/CFT methods do not presuppose hydrodynamics so are

applicable even to very out-of-equilibrium configurations

◮ AdS/CFT may fill in gaps in our knowledge of the early

nonequilibrium stage of plasma evolution

◮ Thermalization = hydrodynamization ◮ Simple dimensionless criterion for applicability of hydrodynamics ◮ Important role of ‘initial entropy’ as a characterization of the initial

state

◮ One can perhaps understand better the dynamics of lowest

nonhydrodynamic degrees of freedom from the 4D perspective

◮ Key role of quasinormal frequencies...

22 / 22

slide-119
SLIDE 119

Conclusions

◮ AdS/CFT provides a very general framework for studying

time-dependent dynamical processes

◮ The AdS/CFT methods do not presuppose hydrodynamics so are

applicable even to very out-of-equilibrium configurations

◮ AdS/CFT may fill in gaps in our knowledge of the early

nonequilibrium stage of plasma evolution

◮ Thermalization = hydrodynamization ◮ Simple dimensionless criterion for applicability of hydrodynamics ◮ Important role of ‘initial entropy’ as a characterization of the initial

state

◮ One can perhaps understand better the dynamics of lowest

nonhydrodynamic degrees of freedom from the 4D perspective

◮ Key role of quasinormal frequencies...

22 / 22

slide-120
SLIDE 120

Conclusions

◮ AdS/CFT provides a very general framework for studying

time-dependent dynamical processes

◮ The AdS/CFT methods do not presuppose hydrodynamics so are

applicable even to very out-of-equilibrium configurations

◮ AdS/CFT may fill in gaps in our knowledge of the early

nonequilibrium stage of plasma evolution

◮ Thermalization = hydrodynamization ◮ Simple dimensionless criterion for applicability of hydrodynamics ◮ Important role of ‘initial entropy’ as a characterization of the initial

state

◮ One can perhaps understand better the dynamics of lowest

nonhydrodynamic degrees of freedom from the 4D perspective

◮ Key role of quasinormal frequencies...

22 / 22

slide-121
SLIDE 121

Conclusions

◮ AdS/CFT provides a very general framework for studying

time-dependent dynamical processes

◮ The AdS/CFT methods do not presuppose hydrodynamics so are

applicable even to very out-of-equilibrium configurations

◮ AdS/CFT may fill in gaps in our knowledge of the early

nonequilibrium stage of plasma evolution

◮ Thermalization = hydrodynamization ◮ Simple dimensionless criterion for applicability of hydrodynamics ◮ Important role of ‘initial entropy’ as a characterization of the initial

state

◮ One can perhaps understand better the dynamics of lowest

nonhydrodynamic degrees of freedom from the 4D perspective

◮ Key role of quasinormal frequencies...

22 / 22

slide-122
SLIDE 122

Conclusions

◮ AdS/CFT provides a very general framework for studying

time-dependent dynamical processes

◮ The AdS/CFT methods do not presuppose hydrodynamics so are

applicable even to very out-of-equilibrium configurations

◮ AdS/CFT may fill in gaps in our knowledge of the early

nonequilibrium stage of plasma evolution

◮ Thermalization = hydrodynamization ◮ Simple dimensionless criterion for applicability of hydrodynamics ◮ Important role of ‘initial entropy’ as a characterization of the initial

state

◮ One can perhaps understand better the dynamics of lowest

nonhydrodynamic degrees of freedom from the 4D perspective

◮ Key role of quasinormal frequencies...

22 / 22

slide-123
SLIDE 123

Conclusions

◮ AdS/CFT provides a very general framework for studying

time-dependent dynamical processes

◮ The AdS/CFT methods do not presuppose hydrodynamics so are

applicable even to very out-of-equilibrium configurations

◮ AdS/CFT may fill in gaps in our knowledge of the early

nonequilibrium stage of plasma evolution

◮ Thermalization = hydrodynamization ◮ Simple dimensionless criterion for applicability of hydrodynamics ◮ Important role of ‘initial entropy’ as a characterization of the initial

state

◮ One can perhaps understand better the dynamics of lowest

nonhydrodynamic degrees of freedom from the 4D perspective

◮ Key role of quasinormal frequencies...

22 / 22