CyberSec Research

With the advent of advanced quantum processors capable of probing lattice gauge theories (LGTs) in higher spatial dimensions, it is crucial to understand string dynamics in such models to guide upcoming experiments and to make connections to high-energy physics (HEP). Using tensor network methods, we study the far-from-equilibrium quench dynamics of electric flux strings between two static charges in the $2+1$D $\mathbb{Z}_2$ LGT with dynamical matter. We calculate the probabilities of finding the time-evolved wave function in string configurations of the same length as the initial string. At resonances determined by the the electric field strength and the mass, we identify various string breaking processes accompanied with matter creation. Away from resonance strings exhibit intriguing confined dynamics which, for strong electric fields, we fully characterize through effective perturbative models. Starting in maximal-length strings, we find that the wave function enters a dynamical regime where it splits into shorter strings and disconnected loops, with the latter bearing qualitative resemblance to glueballs in quantum chromodynamics (QCD). Our findings can be probed on state-of-the-art superconducting-qubit and trapped-ion quantum processors.

This work revisits the Euclidean Dynamical Triangulation (DT) approach to non-perturbative quantum gravity in three dimensions. Inspired by a recent combinatorial study by T. Budd and L. Lionni of a subclass of 3-sphere triangulations constructed from trees, called the \emph{triple-tree} class, we present a Monte Carlo investigation of DT decorated with a pair of spanning trees, one spanning the vertices and the other the tetrahedra of the triangulation. The complement of the pair of trees in the triangulation can be viewed as a bipartite graph, called the \emph{middle graph} of the triangulation. In the triple-tree class, the middle graph is restricted to be a tree, and numerical simulations have displayed a qualitatively different phase structure compared to standard DT. Relaxing this restriction, the middle graph comes with two natural invariants, namely the number of connected components and loops. Introducing corresponding coupling constants in the action, allows one to interpolate between the triple-tree class and unrestricted tree-decorated DT. Simulations of this extended model confirm the existence of a new phase, referred to as the \emph{triple-tree phase}, besides the familiar crumpled and branched polymer phases of DT. A statistical analysis of the phase transitions is presented, showing hints that the branched polymer to triple-tree phase transition is continuous.

We study the statistical properties of the physical action $S$ for random graphs, by treating the number of neighbors at each vertex of the graph (degree), as a scalar field. For each configuration (run) of the graph we calculate the Lagrangian of the degree field by using a lattice quantum field theory(LQFT) approach. Then the corresponding action is calculated by integrating the Lagrangian over all the vertices of the graph. We implement an evolution mechanism for the graph by removing one edge per a fundamental quantum of time, resulting in different evolution paths based on the run that is chosen at each evolution step. We calculate the action along each of these evolution paths, which allows us to calculate the probability distribution of $S$. We find that the distribution approaches the normal(Gaussian) form as the graph becomes denser, by adding more edges between its vertices. The maximum of the probability distribution of the action corresponds to graph configurations whose spacing between the values of $S$ becomes zero $\Delta S=0$, corresponding to the least-action (Hamilton) principle, which gives the path that the physical system follows classically. In addition, we calculate the fluctuations(variance) of the degree field showing that the graph configurations corresponding to the maximum probability of $S$, which follow the Hamilton's principle, have a balanced structure between regular and irregular graphs.

A recent work (Li, 2406.01204) considered quantum simulation of Quantum Electrodynamics (QED) on a lattice in the Coulomb gauge with gauge degrees of freedom represented in the occupation basis in momentum space. Here we consider representing the gauge degrees of freedom in field basis in position space and develop a quantum algorithm for real-time simulation. We show that the Coulomb gauge Hamiltonian is equivalent to the temporal gauge Hamiltonian when acting on physical states consisting of fermion and transverse gauge fields. The Coulomb gauge Hamiltonian guarantees that the unphysical longitudinal gauge fields do not propagate and thus there is no need to impose any constraint. The local gauge field basis and the canonically conjugate variable basis are swapped efficiently using the quantum Fourier transform. We prove that the qubit cost to represent physical states and the gate depth for real-time simulation scale polynomially with the lattice size, energy, time, accuracy and Hamiltonian parameters. We focus on the lattice theory without discussing the continuum limit or the UV completion of QED.

Motivated by the potential experimental relevance of magnetically affected heavy-quark diffusion, we consider here a five-dimensional nonlinear Einstein-Born-Infeld-dilaton model to not only holographically model the QCD thermodynamics in a magnetic background, but also to probe the charged inner structure of a heavy quarkonium. The dual model's gravitational equations of motion can be solved in analytical form via the potential reconstruction method. Using a variety of tools -- spectral functions, hydrodynamic expansions or hanging strings -- we study the anisotropic diffusion constants and heavy-quark number susceptibility, each time reporting closed form expressions.

I investigate a three-dimensional $U(N)$ Polyakov loop model derived that includes the exact static determinant with $N_f$ degenerate quark flavor and depends explicitly on the quark mass and chemical potential. In the large $N, N_f$ limit mean field gives the exact solution, and the core of the Polyakov loop model is reduced to a deformed unitary matrix model, which I solve exactly. I compute the free energy, the expectation value of the Polyakov loop, and the quark condensate. The phase diagram of the model and the type of phase transition is investigated and shows it depends on the ratio $\kappa =N_f/N$.

We analyze various two-point correlation functions of fermionic bilinears in a rotating finite-size cylinder at finite temperatures, with a focus on susceptibility functions. Due to the noninvariance of radial translation, the susceptibility functions are constructed using the Dirac propagator in the Fourier-Bessel basis instead of the plane-wave basis. As a specific model to demonstrate the susceptibility functions in an interacting theory, we employ the two-flavor Nambu-Jona-Lasinio model. We show that the incompatibility between the mean-field analysis and the Fourier-Bessel basis is evaded under the local density approximation, and derive the resummation formulas of susceptibilities with the help of a Ward-Takahashi identity. The resulting formulation reveals the rotational effects on meson, baryon number, and topological susceptibilities, as well as the moment of inertia. Our results may serve a useful benchmark for future lattice QCD simulations in rotating frames.

In arXiv:2504.17706 {Dutrieux:2025jed} we criticized the excessive model-dependence introduced by rigid few-parameter fits to extrapolate lattice data in the large momentum effective theory (LaMET) when the data are noisy and lose signal before an exponential asymptotic behavior of the space-like correlators is established. In reaction, arXiv:2505.14619 {Chen:2025cxr} claims that even when the data is of poor quality, rigid parametrizations are better than attempts at representing the uncertainty using what they call "inverse problem methods". We clarify the fundamental differences in our perspectives regarding how to meaningfully handle noisy lattice matrix elements, especially when they exhibit a strong sensitivity to the choice of regularization in the inverse problem. We additionally correct misunderstandings of {Chen:2025cxr} on our message and methods.

In a pure Gaussian tripartition, a range of entanglement between two parties ($AB$) can be purified through classical communication of Gaussian measurements performed within the third ($C$). To begin, this work introduces a direct method to calculate a hierarchic series of projective $C$ measurements for the removal of any $AB$ Gaussian noise, circumventing divergences in prior protocols. Next, a multimode conic framework is developed for pursuing the maximum (Gaussian entanglement of assistance, GEOA) or minimum (Gaussian entanglement of formation, GEOF) pure entanglement that may be revealed or required between $AB$. Within this framework, a geometric necessary and sufficient entanglement condition emerges as a doubly-enclosed conic volume, defining a novel distance metric for conic optimization. Extremizing this distance for spacelike vacuum entanglement in the massless and massive free scalar fields yields (1) the highest known lower bound to GEOA, the first that remains asymptotically constant with increasing vacuum separation and (2) the lowest known upper bound to GEOF, the first that decays exponentially mirroring the mixed $AB$ negativity. Furthermore, combination of the above with a generalization of previous partially-transposed noise filtering techniques allows calculation of a single $C$ measurement that maximizes the purified $AB$ entanglement. Beyond expectation that these behaviors of spacelike GEOA and GEOF persist in interacting theories, the present measurement and optimization techniques are applicable to physical many-body Gaussian states beyond quantum fields.

We give a pedagogical introduction to the origin of the mass of the nucleon. We first review the trace anomaly of the energy-momentum tensor, which generates most of the nucleon mass via the gluon fields and thus contributes even in the case of vanishing quark masses. We then discuss the contributions to the nucleon mass that do originate from the Higgs mechanism via the quark masses, reviewing the current status of nucleon $\sigma$-terms that encode the corresponding matrix elements.

The gradient flow exact renormalization group (GFERG) is a variant of the exact renormalization group (ERG) for gauge theory that is aimed to preserve gauge invariance as manifestly as possible. It achieves this goal by utilizing the Yang--Mills gradient flow or diffusion for the block-spin process. In this paper, we formulate GFERG by the Reuter equation in which the block spinning is done by Gaussian integration. This formulation provides a simple understanding of various points of GFERG, unresolved thus far. First, there exists a unique ordering of functional derivatives in the GFERG equation that remove ambiguity of contact terms. Second, perturbation theory of GFERG suffers from unconventional ultraviolet (UV) divergences if no gauge fixing is introduced. This explains the origin of some UV divergences we have encountered in perturbative solutions to GFERG. Third, the modified correlation functions calculated with the Wilson action in GFERG coincide with the correlation functions of diffused or flowed fields calculated with the bare action. This shows the existence of a Wilson action that reproduces precisely the physical quantities computed by the gradient flow formalism (up to contact terms). We obtain a definite ERG interpretation of the gradient flow. The formulation given in this paper provides a basis for further perturbative/non-perturbative computations in GFERG, preserving gauge invariance maximally.

It has been shown that defining gravitational entanglement entropies relative to quantum reference frames (QRFs) intrinsically regularizes them. Here, we demonstrate that such relational definitions also have an advantage in lattice gauge theories, where no ultraviolet divergences occur. To this end, we introduce QRFs for the gauge group via Wilson lines on a lattice with global boundary, realizing edge modes on the bulk entangling surface. Overcoming challenges of previous nonrelational approaches, we show that defining gauge-invariant subsystems associated with subregions relative to such QRFs naturally leads to a factorization across the surface, yielding distillable relational entanglement entropies. Distinguishing between extrinsic and intrinsic QRFs, according to whether they are built from the region or its complement, leads to extrinsic and intrinsic relational algebras ascribed to the region. The "electric center algebra" of previous approaches is recovered as the algebra that all extrinsic QRFs agree on, or by incoherently twirling any extrinsic algebra over the electric corner symmetry group. Similarly, a generalization of previous proposals for a "magnetic center algebra" is obtained as the algebra that all intrinsic QRFs agree on, or, in the Abelian case, by incoherently twirling any intrinsic algebra over a dual magnetic corner group. Altogether, this leads to a compelling regional algebra and relative entropy hierarchy. Invoking the corner twirls, we also find that the extrinsic/intrinsic relational entanglement entropies are upper bounded by the non-distillable electric/magnetic center entropies. Finally, using extrinsic QRFs, we discuss the influence of "asymptotic" symmetries on regional entropies. Our work thus unifies and extends previous approaches and reveals the interplay between entropies and regional symmetry structures.

We analyze the contribution of hypothetical quark electric dipoles to the electric dipole moment (EDM) of the neutron. Particular emphasis is devoted to the strange quark contribution. Considerations based on perturbative QCD, the large N expansion, a critic reassessment of the non-relativistic quark model as well as a next to leading order calculation in heavy baryon effective field theory, all consistently indicate that, barring accidental cancellations, the matrix element of the strange quark dipole should be of order a tenth of those of the valence quarks. This implies that the strange EDM provides the dominant contribution to the neutron EDM in many scenarios beyond the Standard Model.

In this work, a field theory model containing a real scalar singlet and an SU(2) symmetry preserving complex doublet is studied using the method of lattice simulations. The model considers all quartic vertices along with the Yukawa vertex between a real scalar singlet and an SU(2) symmetry preserving complex doublet field. Machine learning is used to extract representative functions of the field propagators, lattice regulator, and the Yukawa vertex. In the considered renormalization scheme the field propagators are found enhanced compared to their respective tree level structure. It is found that mixing of operators containing scalar singlet with SU(2) invariant field operators results in $0^{+}$ states with a peculiar scarcity in hundreds of $GeV$s. The Yukawa vertex shows weak dependence on the field momenta while the theory remain interactive as found by the renormalized field propagators. The impact of the real scalar quartic self interaction is found mitigated due to other interaction vertices. The field expectation values exhibit a certain classification despite no conclusive signal of phase transition.

We introduce a generalized definition of the isothermal compressibility ($\kappa_{T,\sigma_Q^2}$) calculable by keeping net conserved charge fluctuations rather than total number densities constant. We present lattice QCD results for this isothermal compressibility, expressed in terms of fluctuations of conserved charges that are related to baryon ($B$), electric charge ($Q$) and strangeness ($S$) quantum numbers. This generalized isothermal compressibility is compared with hadron resonance gas model calculations as well as with heavy-ion collision data obtained at RHIC and the LHC. We find $\kappa_{T,\sigma_Q^2}=13.8(1.3)$~fm$^3$/GeV at $T_{pc,0}=156.5(1.5)$~MeV and $\hat{\mu}_B=0$. This finding is consistent with the rescaled result of the ALICE Collaboration, where we replaced the number of charged hadrons ($N_{\rm ch}$) by the total number of hadrons ($N_{\rm tot}$) at freeze-out. Normalizing this result with the QCD pressure ($P$) we find that the isothermal compressibility on the pseudo-critical line stays close to that of an {\it ideal gas}, {\it i.e.} $P \kappa_{T,\sigma_Q^2}\simeq 1$.

While there has been a lot of progress in developing a formalism for the study of quarkonia in QGP, a nonperturbative study is still difficult. For bottomonia, where the system size is much less than the inverse temperature, the interaction of the system with the medium can be approximated by a dipole interaction with the color electric field. The decay of the quarkonia can be connected to a correlation function of the color electric field. We present preliminary results from a lattice study of the relevant color electric field correlator. The structure of the correlator, and its difference from the corresponding correlator studied for heavy quark diffusion, is discussed.

We calculate the threshold $T$ matrices of the meson and baryon processes that have no annihilation diagrams: $\pi^{+}\Sigma^{+}$, $\pi^{+}\Xi^0$, $K^+p$, $K^+n$, and $\bar{K}^0\Xi^0$ to the fourth order in heavy baryon chiral perturbation theory. By performing least squares and Bayesian fits to the non-physical lattice QCD data, we determine the low-energy constants through both perturbative and non-perturbative iterative methods. By using these low-energy constants, we obtain the physical scattering lengths in these fits. The values of the scattering lengths tend to be convergent at the fourth order in the perturbative method. The scattering lengths for the five channels, obtained by taking the median values from four different fitting approaches, are $a_{\pi^+\Sigma^+}=-0.16\pm 0.07\,\text{fm}$, $a_{\pi^+\Xi^0}=-0.04\pm0.04\,\text{fm}$, $a_{K^+p}=-0.41\pm 0.11\,\text{fm}$, $a_{K^+n}=-0.19\pm 0.10\,\text{fm}$, and $a_{\bar{K}^0\Xi^0}=-0.30\pm 0.07\,\text{fm}$, where the uncertainties are conservatively estimated by taking the maximum deviation between the median and extreme values of the statistical errors.

We investigate the mixing between flavor-singlet light meson and charmonium operators in the S-wave channels, i.e. pseudo-scalar and vector channel, at two different pion masses. We measure statistically significant non-zero correlations between operators with different quark content corresponding to off-diagonal entries of a flavor-singlet mixing correlation matrix. By solving a GEVP we extract the low-lying energy spectrum and compare it with the one obtained by the different types of operators separately. We also calculate the overlaps between the states created by different operators and the energy eigenstates of the theory and find that all types of operators contribute to resolve the states of interest.