From a Geometric Langlands Duality for Surfaces, to the AGT Correspondence, to Integrable Systems
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M-Theoretic Derivations of 4d-2d Dualities: From a Geometric Langlands Duality for Surfaces, to the AGT Correspondence, to Integrable Systems Meng-Chwan Tan National University of Singapore January 1, 2016 Presentation Outline Introduction Dual 6d M-Theory Compactifications A Geometric Langlands Duality for Surfaces for the A{B Groups A Geometric Langlands Duality for Surfaces for the C{D{G Groups The Pure AGT Correspondence for the A{B Groups The Pure AGT Correspondence for the C{D{G Groups The AGT Correspondence with Matter The \Fully-Ramified” AGT Correspondence and Quantum Integrable Systems Generalizations & Future Work 4d-2d Dualities in Mathematics and Physics Circa 1994, Nakajima [1] | the middle-dimensional cohomology of the moduli space of U(N)-instantons on a resolved ALE space of Ak−1-type can be related to the integrable representations of an affine SU(k)-algebra of level N Circa 2007, Braverman-Finkelberg [2] | the intersection 4 cohomology of the moduli space of G-instantons on R =Zk is conjectured to be related to the integrable representations of the Langlands dual of an affine G-algebra. This conjecture was henceforth known as a geometric Langlands duality for surfaces, since it involves G-bundles over a complex surface (as opposed to a complex curve). 4d-2d Dualities in Mathematics and Physics Circa 2009, Alday-Gaiotto-Tachikawa [3] | the Nekrasov instanton partition function of a 4d N = 2 conformal SU(2) quiver theory is equivalent to a conformal block of a 2d CFT with W2-symmetry that is Liouville theory. This was henceforth known as the celebrated AGT correspondence. Circa 2009, Wyllard [4] | the AGT correspondence is partially checked to hold for a 4d N = 2 conformal SU(N) quiver theory whereby the corresponding 2d CFT is an AN−1 conformal Toda field theory which has WN -symmetry. Circa 2012, Schiffmann-Vasserot, Maulik-Okounkov [5, 6] | the equivariant cohomology of the moduli space of SU(N)-instantons is related to the integrable representations of an affine WN -algebra (as a mathematical proof of AGT for pure SU(N)). Main Objective The main objective of our talk is to present in a pedagogical manner, a fundamental M-theoretic derivation of all the above 4d-2d (conjectured) relations, their generalizations, and the connection to quantum integrable systems. Contents of talk based on my paper arXiv:1301.1977 (JHEP07(2013)171), of the same title. Approach In 2007, Dijkgraaf-Hollands-Sulkowski-Vafa gave a direct physical derivation [7] of Nakajima's result; the relevant generating functions were partition functions of BPS states in two different but dual frames in string/M-theory which could then be equated to each other. Witten, in a series of lectures delivered at the IAS in 2008 [8], argued that a geometric Langlands duality for surfaces can be understood as an invariance of the BPS spectrum of the mysterious 6d N = (2; 0) SCFT under different compactifications down to 5d. We will combine the insights from the above two works, and show that our results can be derived from the principle that the spacetime BPS spectra of string-dual six-dimensional M-theory compactifications with M5-branes, OM5-planes, fluxbranes and 4d worldvolume defects, ought to be equivalent. Dual Compactifications of M-Theory with M5-Branes By using, in a chain of dualities, (i) M-IIA theory duality, (ii) T-duality, (iii) the relation between N55-branes and Taub-NUT 4 R!1 space, (iv) the fact that R =Zk = TNk , (v) the relation between Taub-NUT space in M-theory and D6-branes in IIA theory, and (vi) IIB S-duality, we find that the following six-dimensional M-theory compactifications 4 1 5 M-theory : R =Zk × Sn × Rt ×R (1) | {z } N M5-branes and 5 1 R!0 M-theory : R × Rt × Sn × TNN ; (2) | {z } k M5-branes are physically dual. Dual Compactifications of M-Theory with M5-Branes and OM5-Plane By adding an OM5-plane and using a similar chain of dualities, one can conclude that the following six-dimensional M-theory compactifications 4 1 5 M-theory : R =Zk × Sn × Rt ×R (3) | {z } N M5-branes/OM5-plane and 5 1 R!0 M-theory : R × Rt × Sn × SNN ; (4) | {z } k M5-branes R are physically dual. Here, SNN is Sen's four-manifold which one 3 can roughly regard as TNN with a Z2-identification of its R base and S1-fiber (of asymptotic radius R). Dual Compactifications of M-Theory with M5-Branes and 4d Worldvolume Defect By adding a 4d worldvloume defect of the type studied in [9] that is characterized by a partition of N, and using a similar chain of dualities whilst noting the equivalent geometrical background of the defect [10], one can conclude that the following six-dimensional M-theory compactifications 5 1 4 M-theory : R × Rt × Sn × R =Zk (5) | {z } N M5-branes with a 4d defect and R!0 1 5 M-theory : TNN × Sn × Rt ×R ; (6) | {z } k M5-branes with a 4d defect 1 are physically dual. Here, the 4d worldvolume defect wraps Rt × Sn 4 1 and (i) the z-plane in R =Zk ' Cz =Zk × Cw =Zk , (ii) the S -fiber R!0 3 R!0 of TNN and a single direction along the R base of TNN . Dual Compactifications of M-Theory with M5-Branes, OM5-Plane and 4d Worldvolume Defect By further adding an OM5-plane, one can likewise conclude that the following six-dimensional M-theory compactifications 5 1 4 M-theory : R × Rt × Sn × R =Zk (7) | {z } N M5 + OM5 + 4d defect and R!0 1 5 M-theory : SNN × Sn × Rt ×R ; (8) | {z } k M5 + 4d defect 1 are physically dual. Here, the 4d worldvolume defect wraps Rt × Sn 4 1 and (i) the z-plane in R =Zk ' Cz =Zk × Cw =Zk , (ii) the S -fiber R!0 3 R!0 of SNN , and a single direction along the R base of SNN . An M-Theoretic Derivation of a Geometric Langlands Duality for Surfaces for the A{B Groups 4 R!0 Notice that because R =Zk and TNN are hyperk¨ahler four-manifolds which break half of the thirty-two supersymmetries in M-theory, the resulting six-dimensional spacetime theories along 5 Rt × R in (1) and (2), respectively, will both have 6d N = (1; 1) supersymmetry. As usual, there are spacetime BPS states which are annihilated by a subset of the sixteen supersymmetry generators of the 6d N = (1; 1) supersymmetry algebra; in particular, a generic (half) BPS state in six dimensions would be annihilated by eight supercharges. An M-Theoretic Derivation of a Geometric Langlands Duality for Surfaces for the A{B Groups Since the supersymmetries of the worldvolume theory of the stack of M5-branes are furnished by the ambient spacetime supersymmetries which are unbroken across the brane-spacetime barrier { in this instance, only half of the sixteen spacetime supersymmetries are unbroken across the brane-spacetime barrier because the M5-branes are half-BPS objects { a generic spacetime BPS state would correspond to a worldvolume ground state that is annihilated by all eight worldvolume supercharges. For example, in a six-dimensional compactification of M-theory with an M5-brane wrapping K3 × S1, where K3 is a hyperk¨aher four-manifold, the generic spacetime BPS states which span the massless representations of the 6d N = (1; 1) spacetime supersymmetry algebra correspond to the ground states of the worldvolume theory of the M5-brane [11]. An M-Theoretic Derivation of a Geometric Langlands Duality for Surfaces for the A{B Groups The principle that the spectra of such spacetime BPS states in the physically dual M-theory compactifications (1) and (2) ought to be equivalent, will lead us to a geometric Langlands duality for surfaces for the A{B groups. To understand this claim, we would first need to describe the quantum worldvolume theory of the stack of M5-branes whose ground states correspond to these spacetime BPS states. The quantum worldvolume theory of l coincident M5-branes is described by tensionless self-dual strings which live in the six-dimensional worldvolume itself [12]. In the low-energy point-particle limit, the theory of these strings reduces to a non-gravitational 6d N = (2; 0) Al−1 superconformal field theory of l − 1 massless tensor multiplets. An M-Theoretic Derivation of a Geometric Langlands Duality for Surfaces for the A{B Groups Alternatively, one can also describe (using DLCQ) the quantum worldvolume theory via a sigma-model on instanton moduli space [12, 13]; in particular, if the worldvolume is given by 1 M × Sn × Rt , where M is a generic hyperk¨ahlerfour-manifold, one can compute the spectrum of ground states of the quantum worldvolume theory (that are annihilated by all of its supercharges), as the spectrum of physical observables in the topological sector of 1 a two-dimensional N = (4; 4) sigma-model on Sn × Rt with target the hyperk¨ahlermoduli space MG (M) of G-instantons on M. In the M-theory compactification (1) where l = N, we have G = SU(N) if n = 1, and G = SO(N + 1) if n = 2 and N is even [14]. An M-Theoretic Derivation of a Geometric Langlands Duality for Surfaces for the A{B Groups Since the spectrum of physical observables in the topological sector 1 of the N = (4; 4) sigma-model on Sn × Rt are annihilated by all of its eight supercharges, it would mean that the ground states of the quantum worldvolume theory and hence the spacetime BPS states, would correspond to differential forms on the target space MG (M).