Numerical strategies are constantly developed by our group to benefit from the progress in HPC systems, with an emphasis on efficient exploitation of multi/many-cores architectures. Our group is currently involved in the development of a new multi-level computational strategy based on the multi-boson domain-decomposed Hybrid Monte Carlo. Our future plans include the further development of this numerical strategy to integrate it with the master-field paradigm and to perform a precise study of the string breaking in QCD.

The team of Computational Physics of the Bicocca Theory Group has a wide experience in the study of computing architectures for calculation-intensive problems such as the numerical simulations of strong interactions. In the early 1980s some members of the team have been among the pioneers in the development of numerical simulations of Quantum Chromodynamics (QCD) in the non perturbative regime and have also been involved in the design and manufacturing of four generations of computers with an architecture specifically suited for the calculation structures typical of the numerical simulation of QCD on a lattice (LQCD). Starting from the first machine, APE (1985) with a maximum power of 1 GFlops, a power of 800 GFlops has been reached with apeNEXT (2002) with two other projects of intermediate power.

These computers have given the Italian LQCD community a tool to obtain physics results that, as far as statistical and systematic reliability is concerned, were among the best available at the time and impossible to attain with ordinary computing facilities.

The APE project has been constantly funded by INFN and has soon become an international collaboration with installations in many European research centers.

A description of the project and useful references for a further insight can be found in:

• Computing for LQCD: apeNEXT
• apeNEXT: A MULTI-TFLOPS LQCD COMPUTING PROJECT
• Inspirehep APE collaboration

Our group is directly involved in the development of highly-parallel codes, optimized for the latest generation architectures and with excellent scalability. Moreover we have actively contributed to several other publicly available packages, such as openQCD, DDHMC, Grid and gpt. Finally we authored and currently maintain the open-source analysis package pyobs.

Research and development: cluster KNUTH

• 12 nodes with Intel Xeon Silver, 20 nodes with AMD Epyc 7302
• 1 node with 2x AMD Epyc 7302 and 4x Nvidia A100 SXM4
• 4.5 TB total RAM
• Infiniband EDR 100 Gbit/s
• Master node with 2x Intel Xeon 4208 and 192 GB RAM
• Storage 16 TB SSD

Teaching: cluster WILSON

• 20 nodes with 2x Intel Xeon E5-2630
• 1.3 TB total RAM
• Infiniband 40 Gbit/s
• Master node 2x Intel Xeon E5-2603, 32GB RAM
• Storage 6 TB
• 30 Raspberry Pi 3B+ workstations remotely connected to the cluster (Laboratorio Fisica Computazionale “Marco Comi”)

The non-perturbative study of relativistic quantum field theories is required for the theoretical understanding of many phenomena in Physics where the interactions among the fundamental constituents are strong. We actively involved in the following areas of research:

The current discrepancy between the theoretical prediction and the experimental measurement of the anomalous magnetic of the muon, is a promising direction to look for physics beyond the Standard Model. The theoretical determination of the hadronic contributions, which dominates the error of the theory prediction, is based on dispersive relations and rely on several additional experimental inputs. Lattice QCD is the only method to obtain a first-principles prediction and our group is pioneering a calculation of the hadronic vacuum polarization contribution to the (g-2) of the muon based on a new multi-level Monte Carlo method, with the aim of delivering the desired target accuracy of a few per-mille.

CP violation in the SM is not sufficient to explain the observed matter/antimatter asymmetry. Hence CP violating hadronic decays and other flavor-physics related processes are an excellent laboratory to test the validity of the SM, to possibly identify discrepancies and signs of unknown fundamental phenomena. The prediction of the relevant hadronic amplitudes can be reliably obtained only from Lattice QCD simulations. In our group we are working both on their direct calculation using the so-called finite volume formalism, and on the formulation of new formal strategies to extract them from Euclidean correlators.

QCD plays a crucial and dominant role in phenomena involving the collective behaviour of strongly interacting particles that span from astrophysics and cosmology to the collisions of heavy ions. However, the behaviour of the theory is unknown for temperatures above 1-2 GeV due to numerical challenges. Our group has proposed and developed an innovative theoretical framework that overcomes the difficulties of state-of-the-art approaches to investigate QCD at high temperatures. The setup is based on formulating the quantum theory in a moving reference frame in the path integral formalism, thus providing new and more efficient equations to compute non-perturbatively the thermodynamical properties of the theory by Monte Carlo simulations on the lattice. The method has been already successfully applied to compute the Equation of State of the SU(3) Yang-Mills theory to very high temperatures and we are currently extending the study to QCD; the technique has been also instrumental to measure, for the first time, the QCD mesonic screening masses at temperatures up to the Electro-Weak scale and beyond. In both cases, despite perturbation theory being expected to be valid at asymptotically large temperatures, it turns out that it does not provide a satisfactory description of thermal QCD up to the electroweak scale.

M. Bruno, C. Destri, L. Giusti, M. Pepe, F. Rapuano, Doctoral students and postdoc.

• [2021-2023] QCDLAT, INFN national project
• [2021] MLHVP - Multi-Level measurement of the Hadron Vacuum Polarization in Lattice QCD, PRACE
• [2019-2020] EoSQCD – Equation of State of QCD, PRACE
• [2019-2020] The Equation of State of QCD, ISCRA
• [2019-2020] The anomalous magnetic moment of the muon with a multi-level algorithm, ISCRA
• [2019] Gradient Flow coupling in a massive scheme, HLRN
• [2018-2020] New frontiers in lattice field theory for the SM and beyond, INFN national project
• [2016-2018] High performance data network, INFN special project

• CERN Theory department
• CLS
• DESY Zeuthen
• BNL
• Higgs Centre for Theoretical Physics
• Università degli Studi di Parma
• Università degli Studi di Roma Tor Vergata
• Sapienza Università di Roma

• GGI
• latticejobs
• latticenews
• MIT Virtual lattice seminar series
• MIT Centre for Theoretical Physics
• MITP
• INT

• The Standard Model and a new algorithmic invention to measure the specific properties of one of its fundamental particles - the muon
• Magnetismo anomalo del muone: una sfida per la prossima generazione di supercalcolatori
• Destra o sinistra, che direzione scelgono i quark? Ce lo dice il super computer
• Destra o sinistra: è un supercommputer a dirci la direzione che prendono i quark
• New Calculation Refines Comparison of Matter with Antimatter