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TO WA R D S W E A K CO U P L I N G I N H O LO G R A P H Y WO R K - - PowerPoint PPT Presentation

S A O G R OZ DA N OV I N ST I T U U T- LO R E N TZ F O R T H E O R E T I CA L P H Y S I C S L E I D E N U N I V E R S I TY TO WA R D S W E A K CO U P L I N G I N H O LO G R A P H Y WO R K I N CO L L A B O R AT I O N W I T H J . CA S


slide-1
SLIDE 1

TO WA R D S W E A K CO U P L I N G I N H O LO G R A P H Y

I N ST I T U U T- LO R E N TZ F O R T H E O R E T I CA L P H Y S I C S L E I D E N U N I V E R S I TY

OX F O R D, 6 . 3 . 2 0 1 7

S A Š O G R OZ DA N OV

WO R K I N CO L L A B O R AT I O N W I T H J . CA S A L D E R R E Y-S O L A N A , N . KA P L I S , N .

P O OV U T T I K U L , A . STA R I N E T S A N D W. VA N D E R S C H E E

slide-2
SLIDE 2

O U T L I N E

  • from holography to experiment
  • coupling constant dependence and universality in

hydrodynamics

  • thermalisation and higher-energy spectrum
  • heavy ion collisions
  • conclusion and future directions

2

slide-3
SLIDE 3

F R O M H O LO G R A P H Y TO E X P E R I M E N T

  • some strongly coupled field theories have a

dual gravitational description (AdS/CFT correspondence)

  • riginally a duality in type IIB string theory
  • so far: universality at strong coupling
  • challenges
  • field content (no supersymmetry)
  • away from infinite N
  • away from infinite coupling

Z[field theory] = Z[string theory]

3

α0 ∝ 1/λ1/2 λ ≡ g2

Y MN

slide-4
SLIDE 4

T WO C L A S S E S O F T H E O R I E S

  • top-down dual of N=4 theory with ’t Hooft coupling corrections from

type IIB string theory

SIIB = 1 2κ2

10

Z d10x√−g ✓ R − 1 2 (∂φ)2 − 1 4 · 5!F 2

5 + γe− 3

2 φW + . . .

◆ γ = α03ζ(3)/8 α0/L2 = λ1/2

W = CαβγδCµβγνC ρσµ

α

ρσδ + 1

2CαδβγCµνβγC ρσµ

α

ρσδ

4

  • bottom-up curvature-squared theory with a special, non-perturbative

case of Gauss-Bonnet gravity

SR2 = 1 2κ2

5

Z d5x√−g ⇥ R − 2Λ + L2 α1R2 + α2RµνRµν + α3RµνρσRµνρσ⇤

SGB = 1 2κ2

5

Z d5x√−g  R − 2Λ + λGB 2 L2 R2 − 4RµνRµν + RµνρσRµνρσ

slide-5
SLIDE 5

H Y D R O DY N A M I C S

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SLIDE 6

H Y D R O DY N A M I C S

  • QCD and quark-gluon plasma
  • low-energy limit of QFTs (effective field theory)
  • tensor structures (phenomenological gradient expansions)

with transport coefficients (microscopic)

rµT µν = 0 T µν uλ, T, µ

  • = (ε + P) uµuν + Pgµν ησµν ζr · u∆µν + . . .

6

slide-7
SLIDE 7

H Y D R O DY N A M I C S

  • conformal (Weyl-covariant) hydrodynamics
  • infinite-order asymptotic expansion
  • classification of tensors beyond Navier-Stokes

first order: 2 (1 in CFT) - shear and bulk viscosities second order: 15 (5 in CFT) - relaxation time, … [Israel-Stewart and extensions] third order: 68 (20 in CFT) - [S. G., Kaplis, PRD 93 (2016) 6, 066012, arXiv:1507.02461] 


T µ

µ = 0

gµν → e−2ω(x)gµν T µν → e6ω(x) T µν

ω =

OH

X

n=0

αnkn+1

T µν =

X

n=0

T µν

(n)

7

slide-8
SLIDE 8

H Y D R O DY N A M I C S

  • diffusion and sound dispersion relations in CFT
  • loop corrections break analyticity of the gradient expansion (long-time tails), but are 1/N

suppressed [Kovtun, Yaffe (2003)]

  • entropy current, constraints on transport and new transport coefficients (anomalies,

broken parity)

  • non-relativistic hydrodynamics
  • hydrodynamics from effective Schwinger-Keldysh field theory with dissipation

[Nicolis, et. al.; S. G., Polonyi; Haehl, Loganayagam, Rangamani; de Boer, Heller, Pinzani-Fokeeva; Crossley, Glorioso, Liu]

shear: ω = i η ε + P k2 i " η2τΠ (ε + P)2 1 2 θ1 ε + P # k4 + O

  • k5

sound: ω = ±csk iΓck2 ⌥ Γc 2cs

  • Γc 2c2

sτΠ

  • k3 i

" 8 9 η2τΠ (ε + P)2 1 3 θ1 + θ2 ε + P # k4 + O

  • k5

8

slide-9
SLIDE 9

H Y D R O DY N A M I C S F R O M H O LO G R A P H Y

  • holography can compute microscopic transport coefficients [Policastro,

Son, Starinets (2001)]

  • low-energy limit of QFTs / low-energy gravitational perturbations in

backgrounds with black holes

  • Green’s functions and Kubo formulae
  • quasi-normal modes [Kovtun, Starinets (2005)]
  • fluid-gravity [Bhattacharyya, Hubeny, Minwalla, Rangamani (2007)]


⌦ T ab

R (0)

↵ =Gab

R (0) − 1

2 Z d4xGab,cd

RA (0, x)hcd(x) + 1

8 Z d4xd4yGab,cd,ef

RAA

(0, x, y)hcd(x)hef(y) + . . .

ω =

X

n=0

αnkn+1

9

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SLIDE 10

N = 4 AT I N F I N I T E CO U P L I N G

  • type IIB theory on S5 dual to N=4 supersymmetric Yang-Mills at

infinite ’t Hooft coupling and infinite Nc

  • black brane
  • use to find field theory stress-energy tensor to third order


S = 1 2κ2

5

Z d5x√−g ✓ R + 12 L2 ◆

κ5 = 2π/Nc

ds2 = r2 u

  • −f(u)dt2 + dx2 + dy2 + dz2

+ du2 4u2f(u)

f(u) = 1 − u2

T ab = εuaub + P∆ab ησab + ητΠ 

hDσabi + 1

3σab (r · u)

  • + κ

h Rhabi 2ucRchabidud i + λ1σha

cσbic + λ2σha cΩbic + λ3Ωha cΩbic + 20

X

n=1

λ(3)

n On 10

slide-11
SLIDE 11

N = 4 AT I N F I N I T E CO U P L I N G

  • transport coefficients [S. G., Kaplis, PRD 93 (2016) 6, 066012, arXiv:1507.02461]


η s = 1 4π

λ(3)

1

+ λ(3)

2

+ λ(3)

4

≡ −θ1 = −N 2

c T

32π λ(3)

3

+ λ(3)

5

+ λ(3)

6

≡ −θ2 = N 2

c T

384π ✓π2 12 + 18 ln 2 − ln2 2 − 22 ◆ λ(3)

1

− λ(3)

16 = N 2 c T

16π ✓π2 12 + 4 ln 2 − ln2 2 ◆ λ(3)

17 = N 2 c T

16π ✓π2 12 + 2 ln 2 − ln2 2 ◆

λ(3)

1

6 + 4λ(3)

2

3 + 4λ(3)

3

3 + 5λ(3)

4

6 + 5λ(3)

5

6 + 4λ(3)

6

3 − λ(3)

7

2 + 3λ(3)

8

2 + λ(3)

9

2 − 2λ(3)

10

3 − 11λ(3)

11

6 − λ(3)

12

3 + λ(3)

13

6 − λ(3)

15 = N 2 c T

648π

  • 15 − 2π2 − 45 ln 2 + 24 ln2 2
  • η = π

8 N 2

c T 3

τΠ = (2 − ln 2) 2πT κ = N 2

c T 2

8 λ1 = N 2

c T 2

16 λ2 = −N 2

c T 2

8 ln 2 λ3 = 0

11

slide-12
SLIDE 12

TO P- D O W N CO N ST R U C T I O N

  • type IIB action with ’t Hooft coupling corrections
  • dimensional reduction
  • black brane


SIIB = 1 2κ2

10

Z d10x√−g ✓ R − 1 2 (∂φ)2 − 1 4 · 5!F 2

5 + γe− 3

2 φW + . . .

◆ γ = α03ζ(3)/8 α0/L2 = λ1/2

W = CαβγδCµβγνC ρσµ

α

ρσδ + 1

2CαδβγCµνβγC ρσµ

α

ρσδ

S = 1 2κ2

5

Z d5x√−g ✓ R + 12 L2 + γW ◆

ds2 = r2 u

  • −f(u)Ztdt2 + dx2 + dy2 + dz2

+ Zu du2 4u2f

f(u) = 1 − u2

Zt = 1 − 15γ

  • 5u2 + 5u4 − 3u6

Zu = 1 + 15γ

  • 5u2 + 5u4 − 19u6

12

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SLIDE 13

TO P- D O W N CO N ST R U C T I O N

  • N=4 transport coefficients to second order [S. G., Starinets, JHEP 1503 (2015)

007 arXiv:1412.5685]

η = π 8 N 2

c T 3 (1 + 135γ + . . . )

τΠ = (2 − ln 2) 2πT + 375γ 4πT + . . . κ = N 2

c T 2

8 (1 − 10γ + . . . ) λ1 = N 2

c T 2

16 (1 + 350γ + . . . ) λ2 = −N 2

c T 2

16 (2 ln 2 + 5 (97 + 54 ln 2) γ + . . . ) λ3 = 25N 2

c T 2

2 γ + . . .

η s = 1 4π ⇣ 1 + 15ζ(3)λ−3/2 + . . . ⌘

¯ h 4πkB η s g2Nc

[Kovtun, Son, Starinets (2005)]

13

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SLIDE 14

B OT TO M - U P CO N ST R U C T I O N

  • curvature-squared theory [S. G., Starinets, JHEP 1503 (2015) 007 arXiv:1412.5685]

SR2 = 1 2κ2

5

Z d5x√−g ⇥ R − 2Λ + L2 α1R2 + α2RµνRµν + α3RµνρσRµνρσ⇤

η = r3

+

2κ2

5

(1 − 8 (5α1 + α2)) + O(α2

i )

ητΠ = r2

+ (2 − ln 2)

4κ2

5

✓ 1 − 26 3 (5α1 + α2) ◆ − r2

+ (23 + 5 ln 2)

12κ2

5

α3 + O(α2

i )

κ = r2

+

2κ2

5

✓ 1 − 26 3 (5α1 + α2) ◆ − 25r2

+

6κ2

5

α3 + O(α2

i )

λ1 = r2

+

4κ2

5

✓ 1 − 26 3 (5α1 + α2) ◆ − r2

+

12κ2

5

α3 + O(α2

i )

λ2 = −r2

+ ln 2

2κ2

5

✓ 1 − 26 3 (5α1 + α2) ◆ − r2

+ (21 + 5 ln 2)

6κ2

5

α3 + O(α2

i )

λ3 = −28r2

+

κ2

5

α3 + O(α2

i )

14

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SLIDE 15

B OT TO M - U P CO N ST R U C T I O N

  • Gauss-Bonnet theory [S. G., Starinets, Theor. Math. Phys. 182 (2015) 1, 61-73]

SGB = 1 2κ2

5

Z d5x√−g  R − 2Λ + λGB 2 L2 R2 − 4RµνRµν + RµνρσRµνρσ

η = sγ2/4π τΠ = 1 2πT ✓1 4 (1 + γ) ✓ 5 + γ − 2 γ ◆ − 1 2 log 2 (1 + γ) γ ◆ λ1 = η 2πT (1 + γ)

  • 3 − 4γ + 2γ3

2γ2 ! λ2 = − η πT ✓ −1 4 (1 + γ) ✓ 1 + γ − 2 γ ◆ + 1 2 log 2 (1 + γ) γ ◆ λ3 = − η πT (1 + γ)

  • 3 + γ − 4γ2

γ2 ! κ = η πT (1 + γ)

  • 2γ2 − 1
  • 2γ2

! θ1 = η 8π2T 2 γ

  • 2γ2 + γ − 1
  • γ =

p 1 − 4λGB

η s = 1 4π (1 − 4λGB)

15

slide-16
SLIDE 16

L I M I T S O F T H E G AU S S - B O N N E T T H E O R Y

  • exact spectrum in the extreme (anomalous) limit of

16

λGB = 1/4

Scalar: w = −i ⇣ 4 + 2n1 − p 4 − 3q2 ⌘ , w = −i ⇣ 4 + 2n2 + p 4 − 3q2 ⌘ Shear: w = −2i (1 + n1) , w = −2i (3 + n2) Sound: w = −i ⇣ 4 + 2n1 − p 4 + q2 ⌘ , w = −i ⇣ 4 + 2n2 + p 4 + q2 ⌘

  • in the extreme ``weak” limit there is a curvature

singularity, which needs a stringy resolution

lim

λGB→−∞ SGB = λGBL2

4κ2

5

Z d5x√−g  R2 − 4RµνRµν + RµνρσRµνρσ − 4Λ λGBL2

  • ds2 =

p −λGB 2 4− ˜ r2 L2 r 1 − ˜ r4

+

˜ r4 dt2 + L2 ˜ r2 q 1 −

˜ r4

+

˜ r4

d˜ r2 + ˜ r2 L2

  • dx2 + dy2 + dz2

3 5

λGB → −∞

  • how can we interpret the extreme limits of the Gauss-Bonnet coupling?
slide-17
SLIDE 17

C H A R G E D I F F U S I O N

  • construct the most general four-derivative action [S. G., Starinets (2016)

arXiv:1611.07053]

17

  • make it such that the equations of motion are only second order

S = 1 2κ2

5

Z d5x√−g [R − 2Λ + LGB] + Z d5x√−gLA

LA = 1 4FµνF µν + α4RFµνF µν + α5RµνFµρF ρ

ν + α6RµνρσFµνFρσ + α7 (FµνF µν)2

+ α8rµFρσrµF ρσ + α9rµFρσrρF µσ + α10rµF µνrρFρν + α11F µνFνρF ρσFσµ

LA = − 1 4FµνF µν + β1L2 (RFµνF µν − 4RµνFµρF ρ

ν + RµνρσFµνFρσ)

+ β2L2 (FµνF µν)2 + β3L2F µνFνρF ρσFσµ

D = (1 + γGB)(1 + 2β) ⇣ β + p β2 − γ2

GB

⌘ 6(β − 1) h β ⇣ β + p β2 − γ2

GB

⌘ − γ2

GB

i ( p (1 − γ2

GB) (β2 − γ2 GB) ln

" γGB 1 + p 1 − γ2

GB

# −

  • β − γ2

GB

  • ln

" γGB β + p β2 − γ2

GB

#)

  • diffusion

γGB = p 1 − 4λGB β = 1 + 48β1

D 6= D = 0 D 6= D = 0

slide-18
SLIDE 18

U N I V E R S A L I TY

  • membrane paradigm (conserved current)
  • first-order hydrodynamics [Kovtun, Policastro, Son, Starinets]
  • second-order hydrodynamics [Haack, Yarom (2009); S. G., Starinets, JHEP 1503

(2015) 007 arXiv:1412.5685]

η s = 1 4π

∂rJ = 0

2ητΠ − 4λ1 − λ2 = O

  • γ2

2ητΠ − 4λ1 − λ2 = O

  • α2

i

  • 2ητΠ − 4λ1 − λ2 = − η

πT (1 − γGB)

  • 1 − γ2

GB

  • (3 + 2γGB)

γ2

GB

= −40λ2

GBη

πT + O

  • λ3

GB

  • 18
slide-19
SLIDE 19

( M O R E ) U N I V E R S A L I TY

  • non-renormalisation of anomalous conductivities

[Gursoy, Tarrio (2015); S. G., Poovuttikul, JHEP 1609 (2016) 046 arXiv: 1603.08770]

  • universal values
  • bulk with arbitrarily high derivatives (gauge, diffeomorphism)
  • proof to all orders in the coupling constant expansion

✓ hδJµi hδJµ

5 i

◆ = ✓ σJB σJω σJ5B σJ5ω ◆ ✓ Bµ ωµ ◆

σJ5B = −2γµ σJB = −2γµ5, σJ5ω = κµ2

5 + γµ2 + 2λ(2πT)2

σJω = 2γµ5µ

S = Z d5x√−g {L [Aa, Va, gab, φi] + LCS [Aa, Va, gab]}

LCS [Aa, Va, gab] = ✏abcdeAa ⇣ 3 FA,bcFA,de + FV,bcFV,de + Rp

qbcRq pde

19

slide-20
SLIDE 20

B E YO N D H Y D R O DY N A M I C S

slide-21
SLIDE 21

W E A K CO U P L I N G ( K I N E T I C T H E O R Y )

  • coupling constant dependence of non-hydrodynamic transport

[S. G., Kaplis, Starinets, JHEP 1607 (2016) 151 arXiv:1605.02173]

  • instead of hydrodynamics, start with (weakly coupled) kinetic theory
  • essential concept: quasi-particles
  • Boltzmann equation
  • close to equilibrium
  • resulting equation
  • solution

21

∂F ∂t + pi m ∂F ∂ri − ∂U(r) ∂ri ∂F ∂pi = C[F]

F(t, r, p) = F0(r, p) [1 + ϕ(t, r, p)]

∂ϕ ∂t = −pi m ∂ϕ ∂ri + ∂U(r) ∂ri ∂ϕ ∂pi + L0[ϕ] ϕ(t, r, p) = etL ϕ0(r, p) = 1 2πi

γ+i∞

Z

γ−i∞

est Rsds ϕ0(r, p)

Rs = (sI − L)−1

slide-22
SLIDE 22

W E A K CO U P L I N G ( K I N E T I C T H E O R Y )

  • ansatz for homogeneous eq. distribution
  • eigenvalue equation for lin. coll. operator
  • hierarchy of relaxation times

22

ϕ(t, p) = e−νth(p)

−νh = L0[h]

ϕ(t, p) = X

n

Cne−νnthn(p)

dominant:

τR = 1/νmin

slide-23
SLIDE 23

T H E R M A L I S AT I O N ( R E L A X AT I O N )

  • KGB equation
  • kinetic theory predicts
  • relaxation time bound [Sachdev]
  • Ising model (BTZ)

η = τR s T

τR ≥ C ~ kBT

GR(ω, q) = C∆ π Γ2(∆ − 1) sin π∆

  • Γ

✓∆ 2 + i(ω − q) 4πT ◆ Γ ✓∆ 2 + i(ω + q) 4πT ◆

  • 2

× " cosh q 2T − cos π∆ cosh ω 2T + i sin π∆ sinh ω 2T #

ω = ±q − i4πT ✓ n + ∆ 2 ◆

τR = 1 2π∆ ~ kBT

23

∂F ∂t + pi m ∂F ∂ri − ∂U(r) ∂ri ∂F ∂pi = −F − F0 τR

cute:

∆ = 2 ⇒ “η/s” = 1/4π

slide-24
SLIDE 24

F U L L Q UA S I N O R M A L S P E C T R U M

  • weak/strong coupling (perturbative/holographic quasi-normal

mode calculations) [Hartnoll, Kumar (2005)]

q q

  • q
  • q
  • i4πT
  • i4πT
  • i8πT
  • i8πT
  • i12πT
  • i12πT
  • i16πT
  • i16πT

Re ω Im ω Re ω Im ω

λ → 0 λ → ∞

24

slide-25
SLIDE 25

R E S U LT S : Q N M ST R U C T U R E

  • different trends depending on
  • poles become denser (branch cut)
  • new poles on imaginary axis

x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x ◆ ◆ ◆ Re ω Im ω x x x x x x x x x x x x x x x x x x x x x x x x ◆ ◆ ◆ Re ω Im ω

η/s

η/s > ~/4πkB η/s < ~/4πkB

``weak limit”

γ → ∞ λGB → −∞

``anomalous limit” λGB → 1/4

25

slide-26
SLIDE 26

Q N M ST R U C T U R E

  • shear channel QNMs in N=4

x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x ◆ ◆ ◆ Re ω Im ω x x x x x x x x x x x x x x x x x x x x x x x x ◆ ◆ ◆ Re ω Im ω ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ □ □ □ □ □ □ □ □ □ □ □ □ ○ □ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ □ □ □ □ □ □ □ □ □ □ ○ □ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ □ □ □ □ □ □ □ □ □ □ □ □ ○ □ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ ○ □

26

slide-27
SLIDE 27

Q N M ST R U C T U R E

  • shear channel QNMs in Gauss-Bonnet

x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x ◆ ◆ ◆ Re ω Im ω x x x x x x x x x x x x x x x x x x x x x x x x ◆ ◆ ◆ Re ω Im ω ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ ○ □ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ ○ □ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ ○ □ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ ○ □

27

slide-28
SLIDE 28

K I N E T I C T H E O R Y R E S U LT

  • kinetic theory behaviour quickly approached

x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x ◆ ◆ ◆ Re ω Im ω x x x x x x x x x x x x x x x x x x x x x x x x ◆ ◆ ◆ Re ω Im ω

η/s ∼ const τRT

○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○○ ○ ○ ○○○○○○○○○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □□□□□□□□ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ ○ □

28

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SLIDE 29

H Y D R O DY N A M I C S

  • breakdown of hydrodynamics (diffusion)

qc ∼ λ3/4

29

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SLIDE 30

H Y D R O DY N A M I C S

  • breakdown of hydrodynamics (diffusion)
〉 〉

qc ∼ λ3/4

30

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SLIDE 31

H Y D R O DY N A M I C S

  • breakdown of hydrodynamics (sound)
〉 〉

qc ∼ λ3/4

31

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SLIDE 32

H Y D R O DY N A M I C S

  • breakdown of hydrodynamics due to new poles
  • shear and sound correlators in Gauss-Bonnet [S. G., Starinets (2016) arXiv:

1611.07053]

32

Gtt,tt(ω, q) = 3 √ 2π4T 4 (1 + γGB)3/2κ2

5

  • 5q2 − 3ω2

(1 − ω/ωg) − iγ2

GBωq2/πT

(3ω2 − q2) (1 − ω/ωg) + iγ2

GBωq2/πT

!

Gxz,xz(ω, q) = √ 2π3T 3γ2

GB

(1 + γGB)3/2κ2

5

✓ ω2 iω − iω2/ωg − γ2

GBq2/4πT

  • dispersion relations

ω1 = −i γ2

GB

4πT q2 ω2 = ωg + i γ2

GB

4πT q2

ω1,2 = ± 1 √ 3 q − i γ2

GB

6πT q2 ω3 = ωg + i γ2

GB

3πT q2 ωg = − 8πTi γGB (γGB + 2) − 3 + 2 ln ⇣

2 γGB+1

⌘ ≈ −8πTi γ2

GB

  • gap
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SLIDE 33

Q UA S I - PA RT I C L E S ( T R A N S P O RT P E A K )

  • quasi-particles appear in the spectrum [Casalderrey-Solana, S. G., Starinets (2017)]
  • weak coupling (Boltzmann equation)

33

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SLIDE 34
  • holographic results in N=4 theory (scalar channel)

34

Q UA S I - PA RT I C L E S ( T R A N S P O RT P E A K )

slide-35
SLIDE 35
  • holographic results in a dual of the Gauss-Bonnet theory (scalar

channel)

35

Q UA S I - PA RT I C L E S ( T R A N S P O RT P E A K )

slide-36
SLIDE 36

Q UA S I - PA RT I C L E S I N N = 4

36

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SLIDE 37

Q UA S I - PA RT I C L E S I N G AU S S - B O N N E T

37

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SLIDE 38
  • quasi-particles appear also in other channels (shear)

38

  • how do these peaks manifest themselves (if at all) in a weakly

coupled field theory like QCD?

Q UA S I - PA RT I C L E S I N G AU S S - B O N N E T

slide-39
SLIDE 39

H E AV Y I O N CO L L I S I O N S

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SLIDE 40

H E AV Y I O N CO L L I S I O N S

  • R2 coupling constant corrections to shockwave collisions

[S. G., van der Schee (2016) arXiv:1610.08976]

  • energy density along the longitudinal direction after collision: less

stopping of narrow shocks (88% higher energy density on lightcone) and decreased energy density of wide shocks

40

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SLIDE 41

H E AV Y I O N CO L L I S I O N S

  • delayed hydrodynamisation

41

thydThyd = {0.41 − 0.52λGB, 0.43 − 6.3λGB}

at λGB = −0.2 :

{25%, 290%}

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SLIDE 42

H E AV Y I O N CO L L I S I O N S

  • rapidity profile: start wider and smaller but later become comparable

42

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SLIDE 43

H E AV Y I O N CO L L I S I O N S

  • change in entropy density: enhanced on lightcone, negative in plasma

43

  • total entropy: reduced at intermediate coupling
slide-44
SLIDE 44

CO N C LU S I O N A N D F U T U R E D I R E C T I O N S

  • various weakly coupled properties are recovered remarkably quickly
  • the topic of this workshop: how precisely do they match onto those

computed from weakly coupled, perturbative physics?

  • use interpolations between weakly coupled physics and coupling-

dependent holography to understand intermediate coupling

  • can we see a signature of higher-QNMs (quasi-particles) in

experiments?

  • a harder task for the future: understand 1/N corrections

44

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SLIDE 45

T H A N K YO U !