arXiv subjects

Guy D. Moore

Publications and source records attributed to Guy D. Moore.

At least 19 recordsLinked to original sources

arXiv2026

Tensor Decomposition for Energy-Momentum Correlation Functions

We establish the general functional form of the energy-momentum-tensor two-point function in Euclidean coordinate space at zero and finite temperature. The full correlation function is first decomposed into its fundamental tensorial structures based on the remaining rotational symmetry. We use energy-momentum conservation to derive differential relations between the resulting component functions. Using these constraints, the full set of component functions of the correlator can finally be represented in the form of a smaller set of spectral functions. Finally, we show how to use these techniques for more efficient future lattice investigations.

hep-ph↗

arXiv2026

Non-perturbative Renormalization of the EMT in Full QCD

The energy-momentum tensor (EMT) is the conserved current corresponding to space-time translation symmetry. Its applications are remarkably diverse, ranging from the thermodynamics to the calculation of transport coefficients. While the EMT is well-defined in the continuum up to a total derivative, with its coefficients fixed by Ward identities, its extension to lattice QCD is not straightforward. The primary challenge arises from the breaking of continuous space-time symmetries by the discrete lattice regulator. Although the EMT can be constructed on the lattice in a way that yields the correct continuum limit, the operators are not uniquely defined. In this proceeding, we construct the EMT for both pure-gauge theory and full QCD, discussing its renormalization in the specific context of determining the coefficients required for shear viscosity. In this context, we present a comparative analysis of the trace anomaly, number density, pressure, energy density and enthalpy density with imaginary chemical potential for multiple $\beta$ values at approximately the same temperature, aimed for the continuum limit.

hep-lat↗

arXiv2026

Exact center symmetry and first-order phase transition in QCD with three degenerate dynamical quarks

We study QCD with three degenerate flavors of dynamical quarks using first-principles lattice simulations. For a specific choice of imaginary isospin chemical potential, this theory possesses an exact center symmetry, just like pure gauge theory. This exact symmetry is expected to be intact at low temperatures and spontaneously broken in the high-temperature regime. By analyzing the finite-size scaling of the Polyakov loop distribution, obtained with a dedicated multi-histogram approach, we demonstrate that there is a first-order deconfinement phase transition in between. Our results are obtained employing stout-smeared rooted staggered quarks at one lattice spacing. Using simulations at different quark masses we sketch the behavior of QCD in the mass-isospin chemical potential plane, shedding new light on this corner of the fundamental phase diagram of the strong interactions and the relationship between chiral symmetry breaking and deconfinement.

hep-lat↗

arXiv2025

Finite T topological Susceptibility with heavy Quarks

Axion cosmology needs the QCD topological susceptibility between 400 and 1100 MeV. In this range the bottom quark is inconvenient to include in lattice simulations, but not heavy enough to ignore. We estimate its effect on the susceptibility by computing the ratio of the 4-quark susceptibility and the 4+1-quark susceptibility in the caloron gas approximation. We do so by computing small-mass and large-mass expansions of the finite mass and temperature fluctuation determinant and connecting them with a Padé approximant.

hep-ph↗

arXiv2025

Shear viscosity from quenched to full lattice QCD

The shear viscosity of the quark-gluon plasma (QGP) plays a crucial role in interpreting current measurements from heavy-ion collisions and is a key input to hydro-dynamical models. The interest in shear viscosity also lies in the fact that QGP is the most ideal fluid ever observed and has the shear viscosity to entropy ratio ($η/ s$) close to the theoretical bound $η/ s \geq 1/ 4 π$ in the strong coupling region within AdS/CFT formalism. The lattice determination of $η/ s$ has been explored for the pure gauge case, but its determination in full QCD remains unexplored, despite its significant importance. In this proceeding, we present updates on extending our quenched findings to full QCD. Specifically, we focus on the renormalization of the energy-momentum tensor with the gradient flow method and provide a progress update on determining the relevant renormalization coefficients for shear viscosity. For this purpose, we have used an imaginary isospin chemical potential.

hep-lat↗

arXiv2025

Temperature Dependence of Heavy Quark Diffusion from (2+1)-flavor Lattice QCD

We present a lattice determination of the heavy-quark diffusion coefficient in (2+1)-flavor QCD with almost physical quark masses. The momentum and spatial diffusion coefficients are extracted for a wide temperature range, from $T=163$ MeV to $10$ GeV. The results are in agreement with previous works from the HotQCD collaboration, and show fast thermalization of the heavy quark inside the QGP. Near the chiral crossover temperature $T_c\simeq150$ MeV, our results are close to the AdS/CFT estimation computed at strong coupling.

hep-lat↗

arXiv2025

First-order phase transition in dynamical 3-flavor QCD at imaginary isospin

We revisit QCD with three mass-degenerate quark flavors at an imaginary isospin chemical potential set to 4 pi T/3. This choice corresponds to a special point in the parameter space, where the theory possesses an exact Z(3) center symmetry. Through a finite-size scaling analysis, we demonstrate that in this case the finite temperature QCD transition is of first order and entails singular behavior both in the Polyakov loop and in the quark condensate. Our results are based on simulations with stout-smeared staggered quarks and a dedicated multi-histogram analysis.

hep-lat↗

arXiv2024

QCD field-strength correlators on a Polyakov loop with gradient flow at next-to-leading order

Momentum exchange between a heavy quark and a hot quark-gluon medium can be characterized nonperturbatively in terms of field-strength field-strength (E-E and B-B) correlators along a Polyakov loop. These can be studied on the lattice and analytically continued. However the lattice typically determines the correlators after the application of gradient flow. We investigate how gradient flow renormalizes these correlation functions by carrying out a next-to-leading order perturbative analysis of the correlators including gradient flow. This establishes a next-to-leading order renormalization matching between the correlators as measured on the lattice and the correlators relevant for momentum diffusion.

hep-ph↗

arXiv2024

Hot and Dense QCD Shear Viscosity at (almost) NLO

The next-to-leading order weak-coupling shear viscosity of QCD was computed 6 years ago. However, these results have never been applied at finite baryon chemical potential $μ$, even though intermediate-energy heavy ion collisions and merging neutron stars may explore the Quark-Gluon Plasma in a regime where baryon chemical potentials are large. Here, we extend the next-to-leading order shear viscosity calculations to finite $μ$, and we show that, while the convergence of the weak-coupling expansion is questionable for achievable plasmas, it is somewhat better at $μ> T$ than at $μ=0$.

hep-ph↗

arXiv2024

Lattice $B$-field correlators for heavy quarks

We analyze the color-magnetic (or "$B$") field two-point function that encodes the finite-mass correction to the heavy quark momentum diffusion coefficient. The simulations are done on fine isotropic lattices in the quenched approximation at $1.5\,T_c$, using a range of gradient flow times for noise suppression and operator renormalization. The continuum extrapolation is performed at fixed flow time followed by a second extrapolation to zero flow time. Perturbative calculations to next-to-leading order of this correlation function, matching gradient-flowed correlators to MS-bar, are used to resolve nontrivial renormalization issues. We perform a spectral reconstruction based on perturbative model fits to estimate the coefficient $κ_B$ of the finite-mass correction to the heavy quark momentum diffusion coefficient. The approach we present here yields high-precision data for the correlator with all renormalization issues incorporated at next-to-leading order, and is also applicable for actions with dynamical fermions.

hep-lat↗

arXiv2024

Hydrodynamics as sound-speed approaches light-speed

I present the simplest 3+1 dimensional quantum field theory for which the speed of sound can be arbitrarily close to the speed of light. Examining the hydrodynamics, I find cases where the shear viscosity is finite, but the "shear relaxation coefficient" appears always to be divergently large.

hep-ph↗

arXiv2024

Quark Mass Dependence of Heavy Quark Diffusion Coefficient from Lattice QCD

We present the first study of the quark mass dependence of the heavy quark momentum and spatial diffusion coefficients using lattice QCD with light dynamical quarks corresponding to a pion mass of 320 MeV. We find that, for the temperature range 195 MeV $<T<$ 293 MeV, the spatial diffusion coefficients of the charm and bottom quarks are smaller than those obtained in phenomenological models that describe the $p_T$ spectra and elliptic flow of open heavy flavor hadrons.

hep-lat↗

arXiv2023

Bounding the QCD Equation of State with the Lattice

The equation of state of QCD matter at high densities is relevant for neutron star structure and for neutron star mergers and has been a focus of recent work. We show how lattice QCD simulations, free of sign problems, can provide an upper bound on the pressure as a function of quark chemical potentials. We show that at large chemical potentials this bound should become quite sharp; the difference between the upper bound on the pressure P-phase-quenched and the true pressure P is of order alpha^3 P. The corrections arise from a single Feynman diagram; its calculation would render remaining corrections of order alpha^4 P.

nucl-th↗

arXiv2023

Step scaling with gradient flow and finite temperature

We combine gradient flow, step-scaling, and finite-temperature boundary conditions to scale-set 2+1+1 flavor QCD lattices with physical HISQ quarks at multiple spacings down to a=0.01378 fm, such that they represent the same temperature at the percent level and the same quark mass to a few percent. This preparatory work will allow the evaluation and continuum extrapolation of the topological susceptibility at up to 1 GeV temperatures with good control over quark-mass effects.

hep-lat↗

arXiv2023

Miniclusters from axion string simulations

The properties of axion miniclusters and of the voids between them can have very strong implications for the discovery of axions and the dark matter of the Universe. These properties can be strongly affected by axion dynamics in the early Universe, such as the axion string network and the non-linear dynamics around the QCD phase transition. Recently, improvements in numerical simulation techniques have allowed us to calculate the dark matter axion field from axion strings and QCD effects using different methods: directly with low-tension strings but high resolution, directly with effective high-tension strings, or indirectly by extrapolating an attractor solution. In this work, we study the properties of miniclusters in the different approaches used in the literature. We find that, while there are substantial differences in the mass distribution and internal density profiles, globally there is a similar energy distribution between minicluster halos and voids.

hep-ph↗

arXiv2023

Hard parton dispersion in the quark-gluon plasma, non-perturbatively

The in-medium dispersion of hard partons, encoded in their so-called asymptotic mass, receives large non-perturbative contributions from classical gluons, i.e. soft gluons with large occupation numbers. Here, we discuss how the analytical properties of thermal amplitudes allow for a non-perturbative determination of the infrared classical contribution through lattice determinations in the dimensionally-reduced effective theory of hot QCD, EQCD. We show how these lattice determinations need to be complemented by perturbative two-loop matching calculations between EQCD and QCD, so that the unphysical (classical) ultraviolet behavior of EQCD is replaced by its proper quantum QCD counterpart. We show how lattice and perturbative EQCD are in good agreement in the UV and present an outlook on the two-loop quantum QCD contribution.

hep-ph↗

arXiv2023

The force-force-correlator in hot QCD perturbatively and from the lattice

High-energy particles traversing a medium experience modified dispersion. In the Quark-Gluon Plasma, such dispersion affects jet propagation and transport properties and should be determined better. Above $\sim 2T_c$ we expect strongly coupled infrared behavior and perturbative ultraviolet behavior, allowing a perturbative matching to an effective theory called EQCD, which can be studied non-perturbatively. We study the relevant non-local operator in EQCD at next-to-leading order which allows for a complete EQCD-to-lattice match and prepares the groundwork for a matching between EQCD and full QCD. Our results in EQCD show remarkable agreement between perturbation theory and the lattice in the expected regime.

hep-ph↗

arXiv2023

Viscosity of pure-glue QCD from the lattice

We calculate shear viscosity and bulk viscosity in SU(3) gauge theory on the lattice at $1.5 \,T_c$. The viscosities are extracted via a Kubo formula from the reconstructed spectral function which we determine from the Euclidean-time dependence of the corresponding channel of the energy-momentum tensor correlators. We obtain unprecedented precision for the correlators by applying gradient flow and blocking methods. The correlators are extrapolated to the continuum and then to zero flow time. To extract the viscosities we fit theoretically inspired models to the lattice data and crosscheck the fit results using the Backus Gilbert method. The final estimates for shear and bulk viscosity are $η/s = 0.15-0.48$ and $ζ/s = 0.017-0.059$.

hep-lat↗