arXiv subjects

Yizhuang Liu

Publications and source records attributed to Yizhuang Liu.

At least 19 recordsLinked to original sources

arXiv2026

Computability of GPDs near $x=\pmξ$ in Lattice QCD

In lattice QCD computations of generalized parton distributions (GPDs), the large momentum expansion generally requires all hard scales, $2|x\pmξ|P^z$ and $2|1\pm x|P^z$, to be much larger than $Λ_{\rm QCD}$. We show that this condition can be relaxed for $2|x\pmξ|P^z$ at large $ξ$, making the important $x\sim\pmξ$ regions accessible to lattice calculations and considerably expanding the region of computability. Revisiting previous lattice results with complete one-loop matching, we obtain the expected partonic threshold behavior---GPDs continuous at $x=\pmξ$ but with discontinuous derivatives---which has not previously been observed on the lattice. We thus obtain, for the first time, important prediction for GPDs in the distribution-amplitude-like region, which smoothly connects the quark and antiquark PDF-like behaviors.

hep-lat↗

arXiv2026

Exact spin form factors and correlations at a massive Kramers-Wannier interface

We determine exact finite-volume spin form factors and two-point correlations for a massive Kramer--Wannier interface in the scaling Ising model, separating ordered and disordered phases. The interface admits two complementary lattice realizations: a self-dual inhomogeneous Ising chain whose continuum limit has a sign-changing Majorana mass profile, and, after exchanging Euclidean space and time, a mixed thermal average amenable to Toeplitz/Fredholm methods. Combining these descriptions, we obtain the exact Neveu-Schwarz-Ramond spin matrix elements and a factorized Fredholm determinant for the interface correlator. Defect TCSA and independent fermionic spin-chain calculations confirm the predicted spectrum and matrix elements.

hep-th↗

arXiv2026

Analytic asymptotics of the integrable XXX critical spin chains in the small external-field limit from TBA

In this note, inspired partly by the works on the analytic trans-series of free-energies in 2D integrable QFTs in the UV limit, we study the corresponding asymptotic expansions in the IR limit of the integrable XXX spin chains, at the anti-ferromagnetic critical point. Starting from the linear TBA integral equation, we generate the perturbative series in the minimal-scheme coupling constants, up to the first order where the $ζ_3$ appears. To all perturbative orders, at spin one-half, the perturbative series relates to that of the $β^2=8π^-$ massive sine-Gordon by a sign flip of the coupling constant, and this relation generalizes for an arbitrary spin, to certain massive deformation of $su(2)_k$ WZW. This relation partially supports the conjectured field-theoretical interpretations of such critical points, at the leading-power $\&\&$ all-logarithmic accuracy. We also compute the perturbative coefficients attached to the first exponentially-small corrections up to the order where $ζ_3$ appears, in case $s>1$. An interesting feature is that the largest exponentially-small corrections at the locations $h^{2+\frac{2k}{s}}$ are non-vanishing, but the corresponding Borel singularities in the perturbative series are canceled for generic $s>1$, not necessarily integers or half-integers. This becomes most dramatic in the a 't Hooft type large $s$ limit, in which the perturbative series has a finite convergence radius, while these exponentially small corrections still survive.

hep-th↗

arXiv2026

A note on the 2D NLSM free energy

This note contains the perturbative computation of the 2D non-linear sigma model (NLSM) energy-density in a chemical potential $h$, at the fourth order in the coupling constant expansion. The result is in fully agreement with the $h\rightarrow \infty$ asymptotics extracted from the thermodynamical Bethe ansatz (TBA).

hep-th↗

arXiv2026

Trans-series from condensates in the non-linear sigma model

In this work we provide a massless perturbative framework for the two dimensional non-linear sigma model (NLSM), that allows the computation of the perturbative series attached to the operator condensates in the operator product expansion (OPE). It is based on a limit of the quartic linear sigma model (LSM) and is manifestly $O(N)$ symmetric. We show, at next-to-leading order in the $1/N$ expansion, how this framework reproduces the perturbative contribution to the two-point function, as well as its first exponentially small correction due to the condensate of the Lagrangian operator, in full agreement with the exact non-perturbative large $N$ solution. We also show that, in the full LSM, the physics at the natural UV cutoff indeed decouples from the NLSM in the IR, in the weak-coupling limit. In particular, we show that the perturbative framework for the LSM at the cutoff scale is connected to the one in the NLSM. The structure of power divergences in the LSM regularization also reveals that the first renormalon on the positive Borel axis of the NLSM perturbative self-energy is an UV renormalon, which cancels against the ambiguity in the condensate.

hep-th↗

arXiv2026

Analyticity, asymptotics and natural boundary for a one-point function of the finite-volume critical Ising chain

This note reports the following observation: the finite-volume expectation value of the spin operator (the one-point function) between the $\mathbb{Z}_2$-even and odd ground states in the critical periodic Ising chain, when continued as a complex-analytic function of the system length $N$ through the Borel resummation of its large-$N$ expansion, has a natural boundary of analyticity along the negative real axis. The singular behavior near the negative real axis, after an exponential map, is the same as that of a Lambert-type series for the odd-divisor-squared sum near the unit circle $|z|=1$. The same divisor sum also governs the strengths of the Borel discontinuities of the one-point function's factorially-divergent large-$N$ asymptotics. We also report the all-order large-$N$ asymptotics of the leg function for the finite-volume spin-operator form factor, and the similarities to certain known quantities in the literature.

math-ph↗

arXiv2026

Spin-operator form factors of the critical Ising chain and their finite volume scaling limits

In this work, we provide a self-contained derivation of the spin-operator matrix elements in the fermionic basis, for the critical periodic Ising chain at a generic system length $N\in 2Z_{\ge 2}$. The approach relies on the near-Cauchy property of certain matrices formed by the Toeplitz symbols in the critical model, and leads to a few square-root products for the leg functions. The square root products allow simple integral representations, that further reduce to the Binet's second integral and its generalization by Hermite, in the finite volume scaling limit. This leads to product formulas for the spin operator matrix elements in the scaling limit, providing explicit expressions for the spin-operator form factors of the Ising CFT in the fermionic basis, that were computed iteratively in Yurov:1991my. They are all rational numbers up to $\sqrt{2}$. We also determine the normalization factor of the spin-operator and show explicitly how the coefficient $G(\frac{1}{2})G(\frac{3}{2})$ appear through a ground state overlap. Moreover, by expanding the spin-spin two point correlator in the fermionic basis, we observed a Fredholm determinant identity that allows to show the convergence of the rescaled two-point correlator to the CFT version on a cylinder.

hep-th↗

arXiv2026

Asymptotic Long-Distance Expansion of Euclidean Correlators in Lattice Parton Applications

Bilinear Euclidean quark and gluon correlators with Wilson links have been used widely for applications of large-momentum effective field theories to computing non-perturbative collinear and soft parton physics. Due to color confinement, these correlators decay exponentially at large spatial distances, a behavior crucial for computing momentum-space Fourier transformations with controlled errors from lattice QCD data. Using heavy-quark effective theory reduction, dispersive analysis, Lorentz symmetry, and heavy-flavor spectra, we determine the leading and next-to-leading asymptotic behaviors and relate the expansion parameters to binding energies of heavy-flavor hadrons. We demonstrate the results through two-loop calculations in $ϕ^3$ theory and from the perspective of locality and analyticity. We also study the impact of the asymptotic analysis on realistic lattice QCD data and demonstrate reliable error estimates.

hep-lat↗

arXiv2026

Asymptotics of spin-spin correlators weighted by fermion number measurements with low rapidity threshold in the 2D Ising free-fermion QFT

In the work, we study the averaged number of massive fermions above a low rapidity threshold $Y$, underlying the form-factor expansions of the spin-spin two-point correlators at an Euclidean distance $r$, in the 2D Ising QFT at the free massive fermion point. Despite the on-shell freeness, the spin operators are still far away from being Gaussian, and create particles in the asymptotic states with complicated correlations. We show how the number observables can still be incorporated into the integrable Sinh-Gordon/Painleve-III framework and controlled by linear differential equations with two variables $(r,Y)$. We show how the differential equations and the information of two crucial scaling functions arising in the $r\rightarrow 0$, $e^{Y}r={\cal O}(1)$ scaling limit, can be combined to fully determine the small-$r$ asymptotics of the observables, in the $λ$-extended form. The scaling functions, on the other hand, are analyzed by summing the exponential form-factor expansions directly, generalizing the traditional Ising connecting computations. We show carefully, how the singularities cancel in the physical value limit $λπ\rightarrow 1$ and how the power-corrections that collapse at this value can be resummed. In particular, we show for the physical $λ$-value, the scaling functions are related to an integrated four-point function in the Ising CFT and continue to control the asymptotics of the number-observables in the scaling limit up to ${\cal O}(r^3)$.

hep-th↗

arXiv2025

Renormalon-like factorial enhancements to power expansion/OPE in a super-renormalizable 2D $O(N)$ quartic model

In this work, we investigate the effects of logarithms on the asymptotic behavior of power expansion/OPE in supper-renormalizable QFTs. We performed a careful investigation of the large $p^2$ expansion of a scalar-scalar two-point function at the next-to-leading order in the large-$N$ expansion, in a large-$N$ $O(N)$ quartic model that is populated by logarithms. We show that because the large-$p^2$ logarithms of the individual bubbles can be amplified by bubble-chains, there are factorial enhancements to the power expansion. We show how the factorial enhancements appear separately in the coefficient functions and operator condensates, and demonstrate how they are cancelled off-diagonally across different powers. Restricted to any given power, the factorial enhancements are no-longer canceled. The large-$p^2$ power expansion is divergent.

hep-th↗

arXiv2025

Effects of threshold resummation for large-$x$ PDF in large momentum effective theory

Parton distribution functions (PDFs) at large $x$ are challenging to extract from experimental data, yet they are essential for understanding hadron structure and searching for new physics beyond the Standard Model. Within the framework of the large momentum $P^z$ expansion of lattice quasi-PDFs, we investigate large $x$ PDFs, where the matching coefficient is factorized into the hard kernel, related to the active quark momentum $x P^z$, and the threshold soft function, associated with the spectator momentum $(1-x) P^z$. The renormalization group equation of the soft function enables the resummation of the threshold double logarithms $α^{k} \ln^{2k}(1-x)$, which is crucial for a reliable and controllable calculation of large $x$ PDFs. Our analysis with pion valence PDFs indicates that perturbative matching breaks down when the spectator momentum $(1-x)P^z$ approaches $Λ_{\rm QCD}$, but remains valid when both $x P^z$ and $(1-x)P^z$ are much larger than $Λ_{\rm QCD}$. Additionally, we incorporate leading renormalon resummation within the threshold framework, demonstrating good perturbative convergence in the region where both spectator and active quark momenta are perturbative scales.

hep-ph↗

arXiv2024

Revisiting the time-ordering issue of TMD soft factors: causality, coordinate space analyticity and new equalities

We show that as a result of causality-constrained coordinate space analyticity, the Drell-Yan-shape transverse-momentum dependent soft factor in the exponential regulator allows Euclidean-type parametric representations without cuts, to all orders in perturbation theory. Moreover, it is identical to another soft factor defined with a single time-ordering that has a natural interpretation as a space-like form factor. Furthermore, this relation continues to hold for a larger class of TMD soft factors that interpolate between three different rapidity regulators: the off-light-cone regulator, the finite light-front length regulator, and the exponential regulator.

hep-ph↗

arXiv2024

Spin-spin correlators on the $β$/$β^{\star}$ boundaries in 2D Ising-like models: exact analysis through theory of block Toeplitz determinants

In this work, we investigate quantitative properties of correlation functions on the boundaries between two 2D Ising-like models with dual parameters $β$ and $β^{\star}$. Spin-spin correlators in such constructions without reflection symmetry with respect to transnational-invariant directions are usually represented as $2\times 2$ block Toeplitz determinants which are usually significantly harder than the scalar ($1\times 1$ block) versions. Nevertheless, we show that for the specific $β/β^{\star}$ boundaries considered in this work, the symbol matrices allow explicit commutative Wiener-Hopf factorizations. As a result, the constants $E(a)$ and $E(\tilde a)$ for the large $n$ asymptotics still allow explicit representations that generalize the strong Szegö's theorem for scalar symbols. However, the Wiener-Hopf factors at different $z$ do not commute. We will show that due to this non-commutativity, ``logarithmic divergences'' in the Wiener-Hopf factors generate certain ``anomalous terms'' in the exponential form factor expansions of the re-scaled correlators. Since our boundaries in the naive scaling limits can be formulated as certain integrable boundaries/defects in 2D massive QFTs, the results of this work facilitate detailed comparisons with bootstrap approaches.

cond-mat.stat-mech↗

arXiv2024

Bjorken and threshold asymptotics of a space-like structure function in the 2D $U(N)$ Gross-Neveu model

In this work, we investigate a coordinate space structure function ${\cal E}(z^2m^2,λ)$ in the 2D $U(N)$ Gross-Neveu model to the next-to-leading order in the large-$N$ expansion. We analytically perform the twist expansion in the Bjorken limit through double Mellin representations. Hard and non-perturbative scaling functions are naturally generated in their Borel representations with detailed enumerations and explicit expressions provided to all powers. The renormalon cancellation at $t=n$ between the hard functions at powers $p$ and the non-perturbative functions at powers $p+n$ are explicitly verified, and the issue of ``scale-dependency'' of the perturbative and non-perturbative functions is explained naturally. Simple expressions for the leading power non-perturbative functions are also provided both in the coordinate space and the momentum-fraction space ($0<α<1$) with ``zero-mode-type'' subtractions at $α=0$ discussed in detail. In addition to the Bjorken limit, we also perform the threshold expansion of the structure function up to the next-to-next-to-leading threshold power exactly and investigate the resurgence relation between threshold and ``Regge'' asymptotics. We also prove that the twist expansion is absolutely convergent for any $0<z^2<\infty$ and any $ λ\in iR_{\ge 0}$.

hep-th↗

arXiv2024

Renormalon cancellation and linear power correction to threshold-like asymptotics of space-like parton correlators

In this paper, we show that the common hard kernel of double-log-type or threshold-type factorization for certain space-like parton correlators that arise in the context of lattice parton distributions, the heavy-light Sudakov hard kernel, has linear infrared (IR) renormalon. We explicitly demonstrate how this IR renormalon correlates with ultraviolet (UV) renormalons of next-to-leading power operators in two explicit examples: threshold asymptotics of space-like quark-bilinear coefficient functions and transverse momentum dependent (TMD) factorization of quasi wave function amplitude. Theoretically, the pattern of renormalon cancellation complies with general expectations to marginal asymptotics in the UV limit. Practically, this linear renormalon explains the slow convergence of imaginary parts observed in lattice extraction of the Collins-Soper kernel and signals the relevance of next-to-leading power contributions. Fully factorized, fully controlled threshold asymptotic expansion for space-like quark-bilinear coefficient functions in coordinate and moment space has also been proposed.

hep-ph↗

arXiv2023

The Nambu-Goto string in QCD: Dipole interactions, scattering and entanglement

We revisit some aspects of the stringy approach to dipole-dipole interactions, scattering and entanglement in QCD, using the Nambu-Goto (NG) string, without recourse to holography. We first show that the potential between two static dipoles exchanging closed NG strings is attractive at all separations. Underlining the exchange there is an emergent entropy, that is dominated by the tachyon at large separation, and vanishes at short separation, a measure of the confinement-deconfinement transition. The same tachyon is dominant in the scattering amplitude, as a correlator of two Wilson loops for two fixed dipole-like hadrons separated at large rapidity gap, where the contribution of the worldsheet fermions is included. While the tachyon causes the mean string bit density to grow exponentially with the rapidity, the total scattering cross section still satisfies the Froissart bound by quantum shadowing. The stringy scattering exchange also carries an entanglement entropy, that saturates when the bound is reached. For hadrons with varying dipole sizes, the tachyon exchange takes place in hyperbolic space in the conformal limit. The result for the full S-matrix is reminiscent of the one from Mueller$^\prime$s evolved dipole wavefunction, for the total dipole-dipole cross section in perturbative QCD.

hep-ph↗

arXiv2023

Energy-momentum tensor of a hydrogen atom: stability, D-term, and the Lamb shift

We clarify two issues related to the so-called $D$-term in matrix elements of the energy-momentum tensor. First, we show that in a stable system, the $D$-term can have either sign, contrary to claims that it must be negative. Second, we demonstrate a logarithmic enhancement of the $\mathcalα$ correction to the $D$-term in any state of the hydrogen atom. We contrast this enhancement with the Lamb shift where it is present only in S-states.

hep-ph↗

arXiv2023

Updated analysis of near-threshold heavy quarkonium production for probe of proton's gluonic gravitational form factors

There has been growing interest in the near-threshold production of heavy quarkonium which can access the gluonic structure in the nucleon. Previously we studied this process with quantum chromodynamics (QCD) and showed that it can be factorized with the gluon generalized parton distributions (GPDs) in the heavy quark limit. We further argued that the hadronic matrix element is dominated by its leading moments corresponding to the gluonic gravitational form factors (GFFs) in this limit. Since then, there have been many new developments on this subject. More experimental measurements have been made and published, and the lattice simulation of gluonic GFFs has been improved as well. In this work, we make an important revision to a previous result and perform an updated analysis with the new inputs. We also study the importance of the large momentum transfer to extract these gluonic structures reliably in this framework.

hep-ph↗