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Integrability and Bethe Ansatz in the AdS/CFT correspondence. Thanks to: Niklas Beisert (Princeton) Johan Engquist (Utrecht) Gabriele Ferretti (Chalmers) Rainer Heise (AEI, Potsdam) Vladimir Kazakov (ENS) Andrey Marshakov (ITEP, Moscow) Joe Minahan (Uppsala & Harvard) Kazuhiro Sakai (ENS)
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Integrability and Bethe Ansatz in the AdS/CFT correspondence Thanks to: Niklas Beisert (Princeton) Johan Engquist (Utrecht) Gabriele Ferretti (Chalmers) Rainer Heise (AEI, Potsdam) Vladimir Kazakov (ENS) Andrey Marshakov (ITEP, Moscow) Joe Minahan (Uppsala & Harvard) Kazuhiro Sakai (ENS) Sakura Schäfer-Nameki (Hamburg) Matthias Staudacher (AEI, Potsdam) Arkady Tseytlin (Imperial College & Ohio State) Marija Zamaklar (AEI, Potsdam) Konstantin Zarembo (Uppsala U.) Nordic Network Meeting Helsinki, 28.10.05
AdS/CFT correspondence Maldacena’97 Gubser,Klebanov,Polyakov’98 Witten’98
Local operators and spin chains related by SU(2) R-symmetry subgroup j i j i
Operator mixing Renormalized operators: Mixing matrix (dilatation operator):
Multiplicatively renormalizable operators with definite scaling dimension: anomalous dimension
Mixing matrix Heisenberg Hamiltonian
Heisenberg model in Heisenberg representation Heisenberg operators: Hiesenberg equations:
Continuum + classical limit Landau-Lifshitz equation
(+ S5 + fermions) z 5D bulk strings 0 gauge fields 4D boundary
String theory in AdS5S5 Metsaev,Tseytlin’98 • Conformal 2d field theory (¯-function=0) • Sigma-model coupling constant: • Classically integrable Classical limit is Bena,Polchinski,Roiban’03
Need to know the spectrum of string states: • - eigenstates of Hamiltonian in light-cone gauge • or • - (1,1) vertex operators in conformal gauge • Nothing of that is known • But as long as λ>>1 semiclassical approximation is OK Time-periodic classical solutions Bohr-Sommerfeld Quantum states
Consistent truncation String on S3 x R1:
Conformal/temporal gauge: ~energy 2d principal chiral field – well-known intergable model Pohlmeyer’76 Zakharov,Mikhailov’78 Faddeev,Reshetikhin’86
Equations of motion Currents: Virasoro constraints:
Light-cone currents and spins Classical spins: Virasoro constraints: Equations of motion:
High-energy approximation : Approximate solution at The same (Landau-Lifshitz) equation describes the spin chain in the classical limit! Kruczenski’03
Integrability: Time-periodic solutions of classical equations of motion Spectral data (hyperelliptic curve + meromorphic differential) AdS/CFT correspondence: Noether charges in sigma-model Quantum numbers of SYM operators (L, M, Δ)
Global symmetries of the sigma-model Left shifts: Right shifts: Time translations: World-sheet reparameterization invariance
Noether charges Length of the chain: Total spin: Energy (scaling dimension): Virasoro constraints:
“Dimensional analysis” Q – any charge:energy Δ; spins L, M; … Dimensionless variables: • BMN coupling: • filling fraction: Berenstein,Maldacena,Nastase’02
BMN scaling For any classical solution: Frolov-Tseytlin limit: If 1<<λ<<L2: Which can be compared to perturbation theory even though λ is large. Frolov,Tseytlin’03
String energy (strong-coupling calculation): Anomalous dimension (weak-coupling calculation): • three-loop discrepancy • structural difference of finite-size/quantum corrections Callan et al’03; Beisert,Kristjansen,Staudacher’03; Beisert,Dippel,Staudacher’04 Beisert,Tseytlin’05; Schäfer-Nameki,Zamaklar’05
Integrability Equations of motion: Zero-curvature representation: equivalent
time Conserved charges Generating function (quasimomentum): on equations of motion
Non-local charges: Local charges:
Dirac equation in 1d (j0, j1 are 2x2 matrices) with spectral parameter x Quasi-periodic boundary conditions: quasimomentum
Analytic structure of quasimomentum p(x) is meromorphic on complex plane with cuts along forbidden zones of auxiliary linear problem and has poles at x=+1,-1 Resolvent: is analytic and therefore admits spectral representation: and asymptotics at ∞ completely determine ρ(x).
Classical string Bethe equation Kazakov,Marshakov,Minahan,Z.’04 Normalization: Momentum condition: Anomalous dimension:
Take Normalization: Momentum condition: Anomalous dimension: This is the classical limit of Bethe equations for spin chain!
x defined on cuts Ck in the complex plane 0
Exact quantum Bethe equations: In the scaling limit, Taking the logarithm and expanding in 1/L:
Bethe equations for quantum strings? Arutyunov,Frolov,Staudacher’04 Staudacher’04; Beisert,Staudacher’05 Mann,Polchinski’05 Ambjørn,Janik,Kristjansen’05
Quantizing strings in AdS5xS5 Solving N=4, D=4 SYM at large N!
IS N=4 SYM SOLVABLE? STRINGS SPIN CHAINS PLANAR DIAGRAMS Universal relationship for large-N gauge theories?