SciPost Phys. Core 6, 066 (2023) ·
published 16 October 2023

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We outline a holographic framework that attempts to unify Landau and beyondLandau paradigms of quantum phases and phase transitions. Leveraging a modern understanding of symmetries as topological defects/operators, the framework uses a topological order to organize the space of quantum systems with a global symmetry in one lower dimension. The global symmetry naturally serves as an input for the topological order. In particular, we holographically construct a String Operator Algebra (SOA) which is the building block of symmetric quantum systems with a given symmetry G in one lower dimension. This exposes a vast web of dualities which act on the space of Gsymmetric quantum systems. The SOA facilitates the classification of gapped phases as well as their corresponding order parameters and fundamental excitations, while dualities help to navigate and predict various corners of phase diagrams and analytically compute universality classes of phase transitions. A novelty of the approach is that it treats conventional Landau and unconventional topological phase transitions on an equal footing, thereby providing a holographic unification of these seeminglydisparate domains of understanding. We uncover a new feature of gapped phases and their multicritical points, which we dub fusion structure, that encodes information about which phases and transitions can be dual to each other. Furthermore, we discover that selfdual systems typically posses emergent noninvertible, i.e., beyond grouplike symmetries. We apply these ideas to $1+1d$ quantum spin chains with finite Abelian group symmetry, using topologicallyordered systems in $2+1d$. We predict the phase diagrams of various concrete spin models, and analytically compute the full conformal spectra of nontrivial quantum phase transitions, which we then verify numerically.
SciPost Phys. 13, 083 (2022) ·
published 5 October 2022

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We present a correspondence between twodimensional N=(2,2) supersymmetric gauge theories and rational integrable gl(mn) spin chains with spin variables taking values in Verma modules. To explain this correspondence, we realize the gauge theories as configurations of branes in string theory and map them by dualities to brane configurations that realize line defects in fourdimensional ChernSimons theory with gauge group GL(mn). The latter configurations embed the superspin chains into superstring theory. We also provide a string theory derivation of a similar correspondence, proposed by Nekrasov, for rational gl(mn) spin chains with spins valued in finitedimensional representations.
SciPost Phys. 9, 017 (2020) ·
published 5 August 2020

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We propose a toy model for holographic duality. The model is constructed by embedding a stack of $N$ D2branes and $K$ D4branes (with one dimensional intersection) in a 6D topological string theory. The worldvolume theory on the D2branes (resp. D4branes) is 2D BF theory (resp. 4D ChernSimons theory) with $\mathrm{GL}_N$ (resp. $\mathrm{GL}_K$) gauge group. We propose that in the large $N$ limit the BF theory on $\mathbb{R}^2$ is dual to the closed string theory on $\mathbb R^2 \times \mathbb R_+ \times S^3$ with the ChernSimons defect on $\mathbb R \times \mathbb R_+ \times S^2$. As a check for the duality we compute the operator algebra in the BF theory, along the D2D4 intersection  the algebra is the Yangian of $\mathfrak{gl}_K$. We then compute the same algebra, in the guise of a scattering algebra, using Witten diagrams in the ChernSimons theory. Our computations of the algebras are exact (valid at all loops). Finally, we propose a physical string theory construction of this duality using a D3D5 brane configuration in type IIB  using supersymmetric twist and $\Omega$deformation.