The nature of low-lying scalar and axial-vector charmed mesons has long been debated, specifically whether they are best explained as hadronic molecules or compact tetraquark systems. These two scenarios exhibit quite different features for the accessible SU(3) multiplets in the scalar and axial-vector sectors. To resolve this debate, we performed N_f=3+1 lattice simulations and calculated the energy levels of the SU(3) [6] and [15] multiplets for both the scalar and axial-vector mesons in an SU(3) flavor-symmetric setting. In both sectors we find attractive states for the [6] and repulsive interactions for the [15]. This is consistent with the hadronic molecule picture, but not the compact tetraquark picture which predicts a low-lying [15] states in the axial-vector sector but not in the scalar sector.

The nature of low-lying scalar and axial-vector charmed mesons has been debated for decades, with hadronic molecular and compact tetraquark models being prominent candidates. These two models predict quite different features for the accessible SU(3) multiplets in the scalar and axial-vector sectors, which can be tested through lattice calculations at SU(3) symmetric points. In this work, we perform lattice calculations for both scalar and axial-vector charmed mesons with an SU(3) symmetric pion mass about 613 MeV for the SU(3) [6] and [15] multiplets. We find that the [6] multiplet exhibits attractive interactions in both scalar and axial-vector sectors, while the [15] multiplet shows repulsive interactions in both sectors. The energy shifts in the scalar and axial-vector sectors are compatible with each other within uncertainties. These results are fully consistent with the hadronic molecular picture, while challenging the compact tetraquark model, which predicts the existence of low-lying [15] states in the axial-vector sector but not in the scalar sector.

In this proceedings we consider several states, namely the $D^*_{s0}(2317)$, $D_{s1}(2460)$, $D^*_{0}(2300)$ and $D_{1}(2430)$, which appear to defy description as simple quark-antiquark pairs. Theoretical input from unitarized chiral perturbation theory suggests they can be understood as emerging from Goldstone-Boson--$D$-meson scattering. We present results from an $SU(3)$ flavor-symmetric lattice QCD simulation at large pion masses suggesting that there exists a $\pi D$ bound state in the flavor-sextet representation that cannot emerge for quark-antiquark states, but that appears naturally from the multiquark states. Moreover, we find repulsion in the [15] representation, which establishes the pattern predicted for the interactions of Goldstone bosons with $D$ mesons. This suggests these states may have the structure of hadronic molecules.

In recent years many candidates for states beyond the most simple realization of the quark model were found in various experiments around the world. However, so far no consensus exists on their structure, although there is strong evidence that at least some of those are dynamically generated from meson-meson interactions. In this Letter we provide an important missing piece from the theoretical side to prove that the lightest open charm strange and non-strange scalars D_s0^*(2317) and D_0^* as well as their axial-vector partner states can all be understood as emerging from the interactions between Goldstone bosons stemming from the spontaneous breaking of chiral symmetry and the ground state charmed mesons. For that purpose we exploit the flavor multiplet structure of the lightest open-charm positive-parity scalar states in an SU(3) symmetric lattice QCD simulation at large pion masses to establish that there exists a bound state in the flavor-sextet representation, which cannot emerge for quark-antiquark states but appears naturally for four-quark configurations. Moreover, we find repulsion in the [15] representation and thus no single-particle state in this representation exists, falsifying the expectation for tetraquark models. The findings establish the pattern predicted for the interactions of Goldstone bosons with D mesons from chiral symmetry and the paradigm of the lowest-lying positive-parity charmed mesons as dynamically generated states.

In this proceedings we consider several states, namely the $D^*_{s0}(2317)$, $D_{s1}(2460)$, $D^*_{0}(2300)$ and $D_{1}(2430)$, which appear to defy description as simple quark-antiquark pairs. Theoretical input from unitarized chiral perturbation theory suggests they can be understood as emerging from Goldstone-Boson--$D$-meson scattering. We present results from an $SU(3)$ flavor-symmetric lattice QCD simulation at large pion masses suggesting that there exists a $\pi D$ bound state in the flavor-sextet representation that cannot emerge for quark-antiquark states, but that appears naturally from the multiquark states. Moreover, we find repulsion in the [15] representation, which establishes the pattern predicted for the interactions of Goldstone bosons with $D$ mesons. This suggests these states may have the structure of hadronic molecules.

Modular supercomputers contain heterogeneous computing resources on which the user can allocate a hardware mix meeting the demands of the calculation. I discuss motivations for generalizing QCD simulations for use on modular supercomputers, and identify possible models of LQCD simulations suitable for such an environment. I introduce QMOD, a system of libraries in development to enable task-parallelization of existing lattice QCD simulation codes for modular systems. The Jureca cluster at the J\"ulich Supercomputing Centre serves as a test bed for modular supercomputing strategies.

We describe a lattice approach to calculating the leading-order hadronic contribution to the anomalous magnetic moment of the muon. We employ lattice momentum derivatives, in both the spatial and temporal directions, to determine the hadronic vacuum polarization scalar at low momenta and construct a smooth, intregrable function in this momentum region. The method is tested on one hex-smeared Wilson-quark lattice ensemble with physical pion masses.

MILC asqtad QCD SU(3) gauge ensemble; series=a; a=0.11fm; Ls=2.2fm; Nf=2+1; u0.m0=(0.020,0.050)

MILC asqtad QCD SU(3) gauge ensemble; series=a; a=0.083fm; Ls=5.3fm; Nf=2+1; u0.m0=(0.00155,0.031)

MILC asqtad QCD SU(3) gauge ensemble; series=a; a=0.083fm; Ls=2.3fm; Nf=2+1; u0.m0=(0.0124,0.031)

MILC asqtad QCD SU(3) gauge ensemble; series=a; a=0.058fm; Ls=2.8fm; Nf=2+1; u0.m0=(0.0036,0.018)

MILC asqtad QCD SU(3) gauge ensemble; series=a; a=0.11fm; Ls=2.2fm; Nf=2+1; u0.m0=(0.040,0.050)

MILC asqtad QCD SU(3) gauge ensemble; series=a; a=0.058fm; Ls=2.8fm; Nf=2+1; u0.m0=(0.0072,0.018)

MILC asqtad QCD SU(3) gauge ensemble; series=a; a=0.11fm; Ls=2.2fm; Nf=2+1; u0.m0=(0.030,0.050)

MILC asqtad QCD SU(3) gauge ensemble; series=a; a=0.083fm; Ls=2.7fm; Nf=2+1; u0.m0=(0.00465,0.031)

MILC asqtad QCD SU(3) gauge ensemble; series=a; a=0.083fm; Ls=2.3fm; Nf=2+1; u0.m0=(0.0062,0.031)

MILC asqtad QCD SU(3) gauge ensemble; series=a; a=0.14fm; Ls=2.2fm; Nf=2+1; u0.m0=(0.0484,0.0484)

MILC asqtad QCD SU(3) gauge ensemble; series=b; a=0.11fm minus 0.0022fm; Ls=2.16fm; Nf=2+1; u0.m0=(0.010,0.050)