discretized minimal surface and gluon scattering ... · introduction ads/cft correspondence and...
TRANSCRIPT
. . . . . .
IntroductionAdS/CFT correspondence and Gluon amplitudes
Numerial Solutions of minimal surface in AdSConclusions and Outlook
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.
. ..
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Discretized Minimal Surface and Gluon ScatteringAmplitudes in N=4 SYM at Strong Coupling
Katsushi Ito
Tokyo Institute of Technology
June 29– July 2, 2009@Integrability in Gauge and String TheoryS. Dobashi, K.I. and K. Iwasaki, arXiv:0805.3594, JHEP 07 (2008)088
S. Dobashi and K.I., arXiv:0901.3046, Nucl. Phys. B819 (2009) 18
Katsushi Ito gluon amplitudes
. . . . . .
IntroductionAdS/CFT correspondence and Gluon amplitudes
Numerial Solutions of minimal surface in AdSConclusions and Outlook
.
.Gluon Scattering Amplitudes in N = 4 SYM
Planar L-loop, n-point amplitude
A(L)n (k1, · · · , kn) = A(0)
n (k1, · · · , kn)M(L)n (ε)
the BDS conjecture Bern-Dixon-Smirnov, Anastasiou-Bern-Dixon-Kosower
lnMn(ε) =A2
ε2+
A1
ε
− 1
16f(λ)
nX
i=1
“
ln
„
µ2
−si,i+1
«
”2
− g(λ)
4
nX
i=1
ln
„
µ2
−si,i+1
«
+f(λ)
4F (BDS)
n (0) + C
For n = 4
F BDS4 =
1
2log2
“s
t
”
+2π2
3
For n ≥ 5, F BDSn (0) = 1
2
Pni=1 gn,i ( Mandelstam variables:
t[r]i ≡ (ki + ... + ki+r−1)
2)
gn,i = −[n/2]−1X
r=2
ln
−t[r]i
−t[r+1]i
!
ln
−t[r]i+1
−t[r+1]i
!
+ Dn,i + Ln,i +3
2ζ2
Katsushi Ito gluon amplitudes
. . . . . .
IntroductionAdS/CFT correspondence and Gluon amplitudes
Numerial Solutions of minimal surface in AdSConclusions and Outlook
.
.Test of the BDS conjecture (Weak Coupling)
explicit loop calculation
4-point up to 3-loops [BDS]5-point up to 2-loops [Cachazo et. al. , Bern et. al.]n(≥ 6)-point 1-loop [Bern et. al.]
Discrepancy in 6-point 2-loop amplitude[Bern et. al. 0803.1465]Gluon amplitudes=Wilson loop [Drummond et. al. 0803.1466]
ln MMHV6 = ln W (C6) + const., F WL
6 = F BDS6 + R6(u), R6 6= 0
Non-trivial dependence comes from the function of the cross-ratio
uij,kl =x2
ijx2kl
x2ikx2
jl
, (x2ij = t
[j−i]i )
For n = 6, u13,46, u24,15, u35,26 are independent cross ratios.
Katsushi Ito gluon amplitudes
. . . . . .
IntroductionAdS/CFT correspondence and Gluon amplitudes
Numerial Solutions of minimal surface in AdSConclusions and Outlook
Gluon amplitudes = Wilson loop with light-like boundaries
ends at r = R2
zIR→ 0 (zIR → ∞)
yµ: surrounded by the light-likesegments
Mn ∼ exp(−SNG)
k1
k2
r=0
y
SNG: the value of the Nambu-Goto action for the surface surrounded light-likesegments = Area of the minimal surfacestatic gauge: surface y0(y1, y2), r(y1, y2) parametrized by (y1, y2)
SNG =R2
2π
Z
dy1dy2
p
1 + (∂ir)2 − (∂iy0)2 − (∂1r∂2y0 − ∂2r∂1y0)2
r2
Euler-Lagrange equations
∂i
„
∂L
∂(∂iy0)
«
= 0, ∂i
„
∂L
∂(∂ir)
«
− ∂L
∂r= 0,
non-linear differential equations, difficult to solve
Test of the BDS conjecture at Strong Coupling
Katsushi Ito gluon amplitudes
. . . . . .
IntroductionAdS/CFT correspondence and Gluon amplitudes
Numerial Solutions of minimal surface in AdSConclusions and Outlook
.
.Alday-Maldacena’s Solution
4-point amplitude (s = t): s = −(k1 + k2)2, t = −(k1 + k4)
2
boundary condition:r(±1, y2) = r(y1,±1) = 0,y0(±1, y2) = ±y2,y0(y1,±1) = ±y1
solution: y0 = y1y2,
r =p
(1 − y21)(1 − y2
2)
-1-0.5
00.5
1y1
-1
-0.500.5
1y2
-1
-0.5
0
0.5
1
y0
-1-0.5
00.5
1y1
-1
-0.500.5
1y2
-1-0.5
00.5
1y1
-1
-0.5
0
0.5
1
y20
0.250.5
0.751
r
-1-0.5
00.5
1y1
general (s, t)-solution (SO(2, 4) transformation)conformal boost (b)+scale transformation (a)
r′ =ar
1 + by0, y′
0 =a√
1 + b2y0
1 + by0, y′
1 =ay1
1 + by0, y′
2 =ay2
1 + by0
−s(2π)2 = 8a2
(1−b)2, −t(2π)2 = 8a2
(1+b)2
The area agrees with the BDS formula. Higher-point amplitudes?
Katsushi Ito gluon amplitudes
. . . . . .
IntroductionAdS/CFT correspondence and Gluon amplitudes
Numerial Solutions of minimal surface in AdSConclusions and Outlook
.
.Numerical Solutions of Minimal Surfaces in AdS
discretization
square lattice with spacing h = 2M
(i, j) (i, j = 0, · · · , M)y0[i, j] = y0(−1 + hi,−1 + hj)r[i, j] = r(−1 + hi,−1 + hj).
h
h
(i,j)
-1 +1-1
1
y_1
y_2
E-L Equations→ 2(M − 1)2 nonlinear simultaneous equations for y0[i, j] and r[i, j]
Use the same momentum configurations as in Astefanesei-Dobashi-Ito-NastaseSolve these equations numerically. (Newton’s method)Evaluate the action S =
P
L[i, j]h2 using the radial cut-off regularization
S[rc] =R
r(y1,y2)≥rcdy1dy2L
Sdis[rc] =P
r[i,j]≥rcL[i, j]h2
r
y
y
1
2
r=rc
quantitative check of the gluon amplitude/Wilson loop duality and theBDS conjecture at strong coupling
some hints to obtain exact solutions
Katsushi Ito gluon amplitudes
. . . . . .
IntroductionAdS/CFT correspondence and Gluon amplitudes
Numerial Solutions of minimal surface in AdSConclusions and Outlook
.
.Minimal surface:4-point amplitude
-1 -0.5 0 0.5 1 -1-0.5
0 0.5
1-1
-0.5 0
0.5 1
y0M=50
exact sol.
y1y2
y0
-1 -0.5 0 0.5 1 -1-0.5
0 0.5
1 0
0.2 0.4 0.6 0.8
1r M=50
exact sol
y1y2
r
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
-1 -0.5 0 0.5 1
y 0
rho
M=300y0=rho2/2
y1 = y2 section (M = 300)
S4[rc, b] =
Z
S
dy1dy2L, L =1
(1 − y21)(1 − y2
2)
S: region surrounded by the cut-off curve C
r2c = (1 − y2
1)(1 − y22)
1
(1 + by1y2)2
S4[rc, b] =1
4log
2
r2c
−8π2s
!
+1
4log
2
r2c
−8π2t
!
−1
4log
2(
s
t)−3.289... + O(r
2c log r
2c).
FBDS4 = −
1
4log
2(
s
t) −
π2
3= −
1
4log
2(
s
t) − 3.28987...
Katsushi Ito gluon amplitudes
. . . . . .
IntroductionAdS/CFT correspondence and Gluon amplitudes
Numerial Solutions of minimal surface in AdSConclusions and Outlook
.
.Numerical check of the BDS formula: 4-pt amplitude
M = 520
5
10
15
20
25
30
35
0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
S 4[r c
,b]
rc
b=0.0b=0.0(S4)
b=0.4b=0.4(S4
b=0.8b=0.8(S4)
S[rc, b] vs Sdis[rc, b]
-0.07
-0.06
-0.05
-0.04
-0.03
-0.02
-0.01
0
0.01
0.02
0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
(Sdi
s 4-SBD
S 4)/S
dis 4
rc
b=0.0b=0.0(exact)
b=0.4b=0.4(exact)
b=0.8b=0.8(exact)
(Sdis4 − SBDS
4 )/Sdis4
Finite rc correction ≤ 6%
numerical error becomes large rc ≤ 0.2 (and large b)
Katsushi Ito gluon amplitudes
. . . . . .
IntroductionAdS/CFT correspondence and Gluon amplitudes
Numerial Solutions of minimal surface in AdSConclusions and Outlook
.
.n-point amplitude (conjecture)
S̃n[rc] =18
n∑i=1
(log
r2c
−8π2si,i+1
)2
+Fn(p1, · · · , pn)+O(r2c log2 rc),
Fn = −12FBDS
n + Rn(uij,kl)
remainder function: Rn
It is difficult to distinguish finite rc correction and remainderfunction, numerically.
Gdisn [rc, b] = Sdis
n [rc, b] − Sdisn [rc, 0] : smaller rc correction
Katsushi Ito gluon amplitudes
. . . . . .
IntroductionAdS/CFT correspondence and Gluon amplitudes
Numerial Solutions of minimal surface in AdSConclusions and Outlook
.
.Difference of areas with different boost parameters
4-point amplitude:
0
1
2
3
4
5
6
7
8
0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
G4[r
c, b]
rc
b=0.2b=0.2 (BDS)
b=0.4b=0.4 (BDS)
b=0.6b=0.6 (BDS)
b=0.8b=0.8 (BDS)
Gdis[rc, b] vs GBDS [rc, b]
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.2 0.25 0.3 0.35 0.4 0.45 0.5
(Gdi
s 4-G
BDS 4)
/Gdi
s 4
rc
b=0.4b=0.4(exact)
b=0.6b=0.6(exact)
b=0.8b=0.8(exact)
(Gdis − GBDS)/Gdis
small rc: large fluctuation, large rc: large rc correction(∼10%)
difference 5% at rc = 0.3If we find deviation larger than finite rc correction, thissuggests the existence of the remainder function Rn.
Katsushi Ito gluon amplitudes
. . . . . .
IntroductionAdS/CFT correspondence and Gluon amplitudes
Numerial Solutions of minimal surface in AdSConclusions and Outlook
.
.Highre-point amplitudes
6-point solution1
-1 -0.5 0 0.5 1 -1-0.5
0 0.5
1-1
-0.5 0
0.5 1
y0M=50
eq. (2.7)
y1y2
y0
-1 -0.5 0 0.5 1 -1-0.5
0 0.5
1 0
0.2 0.4 0.6 0.8
1 1.2
r M=50eq. (2.7)
y1y2
r
6-point solution2
-1 -0.5 0 0.5 1 -1-0.5
0 0.5
1-1
-0.5 0
0.5 1
y0M=50y1 |y2|
y1y2
y0
-1 -0.5 0 0.5 1 -1-0.5
0 0.5
1 0
0.2 0.4 0.6 0.8
1r M=50
eq. (2.9)
y1y2
r
8-point
-1 -0.5 0 0.5 1 -1-0.5
0 0.5
1 0
0.2 0.4 0.6 0.8
1y0
M=50|y1 y2|
y1y2
y0
-1 -0.5 0 0.5 1 -1-0.5
0 0.5
1 0
0.2 0.4 0.6 0.8
1 1.2
r M=50eq. (2.11)
y1y2
r
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
y 2
y1
b=0.0b=0.4b=0.8
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
y 2
y1
b=0.0b=0.4b=0.8
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
y 2
y1
b=0.0b=0.4b=0.8
Katsushi Ito gluon amplitudes
. . . . . .
IntroductionAdS/CFT correspondence and Gluon amplitudes
Numerial Solutions of minimal surface in AdSConclusions and Outlook
.
.6-point amplitude solution 1
Sdis[rc, b] vs SBDS
5
10
15
20
25
30
35
0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
S 6(1
) [r c,b
]
rc
b=0.0b=0.0(BDS)
b=0.4b=0.4(BDS)
b=0.8b=0.8(BDS)
Gdis[rc, b] vs GBDS [rc, b]
-2.4
-2.2
-2
-1.8
-1.6
-1.4
-1.2
-1
-0.8
-0.6
-0.4
0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
G6(1
) [r c, b
]
rc
b=0.2b=0.2 (BDS)
b=0.4b=0.4 (BDS)
cross ratios are independent of b: u1 = u2 = u3 = 1
SBDS(1)6 [rc, b] =
1
8
n
2 log2(
r2c(1 − b)
8) + 2 log
2(
r2c(1 + b)2
8) + log
2 r2c
4+ log
2(
r2c(1 + b)2
16)o
−1
2
n
log 2 log(1 − b) − 2 log 2 log(1 + b) − 2 log(1 − b) log(1 + b)
+1
2log
2(1 − b) + 3 log
2(1 + b)
o
−3π2
16
=⇒ Rdis6 does not depend on b and is non-zero constant.
Katsushi Ito gluon amplitudes
. . . . . .
IntroductionAdS/CFT correspondence and Gluon amplitudes
Numerial Solutions of minimal surface in AdSConclusions and Outlook
.
.6-point amplitude solution 2
Sdis[rc, b] vs SBDS [rc, b]
5
10
15
20
25
30
35
40
45
0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
S 6(2
) [r c,b
]
rc
b=0.0b=0.0(BDS)
b=0.4b=0.4(BDS)
b=0.8b=0.8(BDS)
Gdis[rc, b] vs GBDS [rc, b]
0
1
2
3
4
5
6
7
8
9
0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
G6(2
) [r c, b
]
rc
b=0.2b=0.2 (BDS)
b=0.4b=0.4 (BDS)
b=0.6b=0.6 (BDS)
b=0.8b=0.8 (BDS)
cross ratios are independent of b: u1 = u2 = u3 = 1
SBDS(2)6 [rc, b] =
1
8
n
log2(
r2c(1 − b)2
8) + log
2(
r2c(1 + b)2
8) + 2 log
2(
r2c(1 + b)
8) + 2 log
2(
r2c(1 − b)
8)o
−1
2
n 3
2log
2(1 − b) +
3
2log
2(1 + b) − 2 log(1 − b) log(1 + b)
o
−3π2
16
Katsushi Ito gluon amplitudes
. . . . . .
IntroductionAdS/CFT correspondence and Gluon amplitudes
Numerial Solutions of minimal surface in AdSConclusions and Outlook
.
.8-point amplitude
Sdis[rc, b] SBDS [rc, b]
0
5
10
15
20
25
30
35
40
45
0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
S 6(2
) [r c,b
]
rc
b=0.0b=0.0(BDS)
b=0.4b=0.4(BDS)
b=0.8b=0.8(BDS)
Gdis[rc, b] vs GBDS [rc, b]
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
F 8[r c
, b]
rc
b=0.2b=0.2 (BDS)
b=0.4b=0.4 (BDS)
b=0.6b=0.6 (BDS)
b=0.8b=0.8 (BDS)
cross ratios are independent of b: uijkl = 1
SBDS8 [rc, b] =
1
8
n
4 log2(
r2c(1 + b)2
8) + 4 log
2(
r2c
4)o
−1
2
n
4 log2(1 + b) − 4 log 2 log(1 + b) −
π2
6
o
−π2
2
Katsushi Ito gluon amplitudes
. . . . . .
IntroductionAdS/CFT correspondence and Gluon amplitudes
Numerial Solutions of minimal surface in AdSConclusions and Outlook
.
.Conclusions and Outlook
For the 4-point amplitude, M = 520 data is numerically consistent withthe BDS formula.
For the 6 and 8-point amplitudes, the present numerical solutions suggestnon-zero constant remainder functions Rn.
Non-trivial momentum configurations =⇒Rn(u).Compare the deviation with the results from weak coupling analysisAnastasiou et al., 0902.2245
Improve numerical solutions (larger M)
AdS3 constraints: r2 − y20 + y2
1 + y22 = 1
Jevicki-Jin-Kalousios 0712.1193, Alday-Maldacena 0903.4701; 0904.0663
Newton method→contragradient method
Hints to obtain exact solution ( without AdS3 constraints)Numerical check of underlying integrable structure at strong coupling(dual conformal symmetry, fermionic T-duality, Yangian)
non-AdS geometry (finite temperature) Ito-Nastase-Iwasaki
Katsushi Ito gluon amplitudes