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Yunfeng Jiang

Publications and source records attributed to Yunfeng Jiang.

At least 37 records · Page 2Linked to original sources
arXiv2025

Holographic Wilson Loop One-point Functions in ABJM Theory

We compute the correlation function between a circular half-BPS Wilson loop (or straight Wilson line) and a local operator in ABJM theory utilizing its M-theory description. The local operator can be a $1/3$-BPS single-trace chiral primary operator or the stress-energy tensor. Using the AdS/CFT correspondence, these correlators are dual to fluctuations of a probe M2-brane in $AdS_4 \times S^7/\mathbb{Z}_k$. We derive analytic results for both cases and compare them with existing results based on supersymmetric localization in the literature. In the large-$N$ limit with $k$ finite, our holograkphic results exhibit perfect agreement with localization.

hep-th↗
arXiv2025

Mesons in a quantum Ising ladder

When two transverse-field Ising chains (TFICs) with magnetic order are coupled, the original free excitations become confined, giving rise to meson-like bound states. In this work, we study such bound states systematically. The mesons are characterized by their fermion number parity and chain-exchanging properties, which lead to distinct sets of mesonic states. The meson masses are determined by solving the Bethe-Salpter equation. An interesting observation is the additional degeneracy in the chain-exchanging odd sectors. Beyond the two particle approximation, we exploit the truncated free fermionic space approach to calculate the spectrum numerically. Corrections to the meson masses are obtained, and the degeneracy is further confirmed. The characterization and degeneracy can be connected to the situation when each chain is tuned to be quantum critical, where the system is described by the Ising$_h^2$ integrable model, a sine-Gordon theory with $\mathbb{Z}_2$ orbifold. Here we establish a clear correspondence between the particles in the bosonized form and their fermionic counterparts. Near this point, the stability of these particles is analyzed using the form factor perturbation scheme, where four particles are always present. Additionally, we calculate the evolution of the dominant dynamical structure factor for local spin operators, providing further insight into the low-energy excitations and their role in the system's behavior. The two-particle confinement framework as well as the parity classifications may inspire the study for other coupled bi-partite systems.

hep-th↗
arXiv2025

Spin dynamics and dark particle in a weak-coupled quantum Ising ladder with $\mathcal{D}_8^{(1)}$ spectrum

Emergent Ising$_h^2$ integrability is anticipated in a quantum Ising ladder composed of two weakly-coupled critical transverse field Ising chains. The system is remarkable for including eight types of massive relativistic particles, with their scattering matrix and mass spectrum characterized by the $\mathcal{D}_8^{(1)}$ Lie algebra. In this article, by computing the spin dynamical structure factors following analytical form factor approach, we clearly identify dispersive single-particle excitations of (anti-) soliton and breathers as well as their multi-particle continua in the spectra, which is further confirmed by the numerical simulations. We show that the selection rule inherent in the parity and topological charge of the theory, causes a significant result that charge-parity-odd particles, termed as dark particles, cannot be directly excited from the ground state through any local or quasi-local operations. This in turn suggests the long lifetime of the lightest dark particle.

cond-mat.str-el↗
arXiv2025

Exact Spin Correlators of Integrable Quantum Circuits from Algebraic Geometry

We calculate the correlation functions of strings of spin operators for integrable quantum circuits exactly. These observables can be used for calibration of quantum simulation platforms. We use algebraic Bethe Ansatz, in combination with computational algebraic geometry to obtain analytic results for medium-size (around 10-20 qubits) quantum circuits. The results are rational functions of the quantum circuit parameters. We obtain analytic results for such correlation functions both in the real space and Fourier space. In the real space, we analyze the short time and long time limit of the correlation functions. In Fourier space, we obtain analytic results in different parameter regimes, which exhibit qualitatively different behaviors. Using these analytic results, one can easily generate numerical data to arbitrary precision.

quant-ph↗
arXiv2025

Resurgent properties of $T\overline{T}$-deformed conformal field theories

We elaborate on the resurgence analysis on the $T\overline{T}$-deformed 2d conformal field theory (CFT). Writing the deformed partition function as an infinite series in the deformation parameter $λ$, we develop efficient analytical methods to compute high-order terms of the $λ$-series. Based on the asymptotic behavior of the large-order perturbative series, we show that the $λ$-series is asymptotic and extract non-perturabtive contributions by resurgence. This paper extends a previous Letter of the same authors to interacting rational CFTs, with Lee-Yang CFT as a concrete example. We also discuss possible implications of the resurgence results on holography.

hep-th↗
arXiv2025

Equivariant smoothing of cusp singularities

We generalize Looijenga's conjecture for smoothing surface cusp singularities to the equivariant setting. Moreover, we prove that for any cusp singularity which admits a one-parameter smoothing, the smoothing can always be induced by smoothing of locally complete intersection cusps. The result provides evidence for the existence of the moduli stack of $\lci$ covers over semi-log-canonical surfaces.

math.AG↗
arXiv2025

Smoothing of surface singularities via equivariant smoothing of lci covers

We provide some results of the smoothing of surface singularities by Looijenga-Wahl and study smoothing of isolated surface singularities induced by equivariant smoothing of locally complete intersection ($\lci$) singularities. We classify the situation where the smoothing of a simple elliptic singularity, a cusp singularity or its cyclic quotient is induced by the equivariant smoothing of the $\lci$ covers.

math.AG↗
arXiv2024

Exact g-function without strings

We propose a new approach to compute exact $g$-function for integrable quantum field theories with non-diagonal scattering S-matrices. The approach is based on an integrable lattice regularization of the quantum field theory. The exact $g$-function is encoded in the overlap of the integrable boundary state and the ground state on the lattice, which can be computed exactly by Bethe ansatz. In the continuum limit, after subtracting the contribution proportional to the volume of the closed channel, we obtain the exact $g$-function, given in terms of the counting function which is the solution of a nonlinear integral equation. The resulting $g$-function contains two parts, the scalar part, which depends on the boundary parameters and the ratio of Fredholm determinants, which is universal. This approach bypasses the difficulties of dealing with magnetic excitations for non-diagonal scattering theories in the framework of thermodynamic Bethe ansatz. We obtain numerical and analytical results of the exact $g$-function for the prototypical sine-Gordon theory with various integrable boundary conditions.

hep-th↗
arXiv2024

Resurgence of $T\bar{T}$-deformed Partition Function

We study non-perturbative effects of torus partition function of the $T\bar{T}$-deformed 2d CFTs by resurgence. The deformed partition function can be written as an infinite series of the deformation parameter $λ$. We develop highly efficient methods to compute perturbative coefficients in the $λ$ expansion. To exemplify, the first 600 coefficients for the $T\bar{T}$-deformed free boson and free fermion are computed. Equipped with the large order perturbative data, we provide convincing numerical evidence that the $λ$ expansion series is asymptotic and not Borel resummable. We extract the non-perturbative contribution by resurgence and propose that they originate from new complex saddle points after analytically continuing the modular parameters in the integral representation of the partition function. The proposal is checked by comparing the predicted asymptotic behavior of the coefficients and large order perturbative data, which match nicely. The implications of these non-perturbative contributions for the Stokes phenomenon, which relates the positive and negative signs of $λ$, is also discussed.

hep-th↗
arXiv2024

Spectrum-preserving deformations of integrable spin chains with open boundaries

We discover a family of local deformations that leave part of the spectrum intact for strongly interacting and exactly solvable quantum many-body systems. Since the deformation preserves the Bethe Ansatz equations (BAE), it is dubbed the iso-BAE flow. Although all theories on the flow share the same BAE, the spectra are different. Part of the spectrum remains intact along the whole flow. Such states are protected by an emergent symmetry. The remaining parts of the spectrum change continuously along the flow and are doubly degenerate for even length spin chains. For odd length chains, the deformed spectrum also comprises doubly degenerate pairs apart from the sector with magnon number $(L+1)/2$, where $L$ is the length of the spin chain. We discuss the iso-BAE flow for the ${\rm XXX}_{1/2}$ model in detail and show that the iso-BAE flows exist for more general models including $q$-deformed XXZ as well as higher spin ${\rm XXX}_{s}$ spin chains.

cond-mat.stat-mech↗
arXiv2024

Spin-$s$ Rational $Q$-system

Bethe ansatz equations for spin-$s$ Heisenberg spin chain with $s\ge1$ are significantly more difficult to analyze than the spin-$\tfrac{1}{2}$ case, due to the presence of repeated roots. As a result, it is challenging to derive extra conditions for the Bethe roots to be physical and study the related completeness problem. In this paper, we propose the rational $Q$-system for the XXX$_s$ spin chain. Solutions of the proposed $Q$-system give all and only physical solutions of the Bethe ansatz equations required by completeness. This is checked numerically and proved rigorously. The rational $Q$-system is equivalent to the requirement that the solution and the corresponding dual solution of the $TQ$-relation are both polynomials, which we prove rigorously. Based on this analysis, we propose the extra conditions for solutions of the XXX$_s$ Bethe ansatz equations to be physical.

hep-th↗
arXiv2024

Emergent $D_8^{(1)}$ spectrum and topological soliton excitation in CoNb$_2$O$_6$

Quantum integrability emerging near a quantum critical point (QCP) is manifested by exotic excitation spectrum that is organized by the associated algebraic structure. A well known example is the emergent $E_8$ integrability near the QCP of a transverse field Ising chain (TFIC), which was long predicted theoretically and initially proposed to be realized in the quasi-one-dimensional (q1D) quantum magnet CoNb$_2$O$_6$. However, later measurements on the spin excitation spectrum of this material revealed a series of satellite peaks that cannot be described by the $E_8$ Lie algebra. Motivated by these experimental progresses, we hereby revisit the spin excitations of CoNb$_2$O$_6$ by combining numerical calculation and analytical analysis. We show that, as effects of strong interchain fluctuations, the spectrum of the system near the 1D QCP is characterized by the $D_{8}^{(1)}$ Lie algebra with robust topological soliton excitation. We further show that the $D_{8}^{(1)}$ spectrum can be realized in a broad class of interacting quantum systems. Our results advance the exploration of integrability and manipulation of topological excitations in quantum critical systems.

cond-mat.str-el↗
arXiv2024

$T\bar{T}$-deformed Entanglement Entropy for Integrable Quantum Field Theory

We calculate the $T\bar{T}$-deformed entanglement entropy for integrable quantum field theories (IQFTs) using the form factor bootstrap approach. We solve the form factor bootstrap axioms for the branch-point twist fields and obtain the deformed form factors. Using these form factors, we compute the deformed von Neuman entropy up to two particle contributions. The solution of the form factor axioms is not unique. We find that for the simplest solution of the bootstrap axioms, the UV limit of the entanglement entropy takes the same form as the undeformed one, but the effective central charge is deformed. For solutions with additional CDD-like factors, we can have different behaviors. The IR corrections, which only depends on the particle spectrum is untouched.

hep-th↗
arXiv2023

$T\bar{T}$-deformation: a lattice approach

Integrable quantum field theories can be regularized on the lattice while preserving integrability. The resulting theory on the lattice are integrable lattice models. A prototype of such a regularization is the correspondence between sine-Gordon model and 6-vertex model on a light-cone lattice. We propose an integrable deformation of the light-cone lattice model such that in the continuum limit we obtain the $T\bar{T}$-deformed sine-Gordon model. Under this deformation, the cut-off momentum becomes energy dependent while the underlying Yang-Baxter integrability is preserved. Therefore this deformation is integrable but non-local, similar to the $T\bar{T}$-deformation of quantum field theory.

hep-th↗
arXiv2023

Giant Correlators at Quantum Level

We compute four-point functions with two maximal giant gravitons and two chiral primary operators at three-loop order in planar $\mathcal{N}=4$ Super-Yang-Mills theory. The Lagrangian insertion method, together with symmetries of the theory fix the integrand up to a few constants, which can be determined by lower loop data. The final result can be written in terms of the known three-loop conformal integrals. From the four-point function, we extract the OPE coefficients of two giant gravitons and one non-BPS twist-2 operator with arbitrary spin at three-loops, given in terms of harmonic sums. We observe an intriguingly simple relation between the giant graviton OPE coefficients and the OPE coefficients of three single-trace operators.

hep-th↗
arXiv2023

Wilson-loop One-point Functions in ABJM Theory

In this paper we initiate the study of correlation functions of a single trace operator and a circular supersymmetric Wilson loop in ABJM theory. The single trace operator is in the scalar sector and is an eigenstate of the planar two-loop dilatation operator. The Wilson loop is in the fundamental representation of the gauge group or a suitable (super-)group. Such correlation functions at tree level can be written as an overlap of the Bethe state corresponding to the single trace operator and a boundary state which corresponds to the Wilson loop. There are various type of supersymmetric Wilson loops in ABJM theory. We show that some of them correspond to tree-level integrable boundary states while some are not. For the tree-level integrable ones, we prove their integrability and obtain analytic formula for the overlaps. For the non-integrable ones, we give examples of non-vanishing overlaps for Bethe states which violate selection rules.

hep-th↗