Lattice quantum chromodynamics at large isospin density

Journal Article · 18 December 2023 · Physical Review. D.

DOI: https://doi.org/10.1103/physrevd.108.114506 · OSTI ID:1996937

Abbott, Ryan  ^[1]; Detmold, William ^[1]; Romero-López, Fernando ^[1]; Davoudi, Zohreh  ^[2]; Illa, Marc  ^[3]; Parreño, Assumpta ^[4]; Perry, Robert J. ^[4]; Shanahan, Phiala E. ^[1]; Wagman, Michael L. ^[5]

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1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); NSF AI Institute for Artificial Intelligence and Fundamental Interactions (IAIFI), Boston, MA (United States)
2. Univ. of Maryland, College Park, MD (United States); Joint Center for Quantum Information and Computer Science, College Park, MD (United States)
3. Univ. of Washington, Seattle, WA (United States). InQubator for Quantum Simulation (IQuS)
4. University of Barcelona (Spain)
5. Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)

We present an algorithm to compute correlation functions for systems with the quantum numbers of many identical mesons from lattice quantum chromodynamics (QCD). The algorithm is numerically stable and allows for the computation of n-pion correlation functions for n ϵ {1, … , N} using a single N × N matrix decomposition, improving on previous algorithms. We apply the algorithm to calculations of correlation functions with up to 6144 charged pions using two ensembles of gauge field configurations generated with quark masses corresponding to a pion mass m_π = 170 MeV and spacetime volumes of (4.4³ × 8.8) fm⁴ and (5.8³ × 11.6) fm⁴. We also discuss statistical techniques for the analysis of such systems, in which the correlation functions vary over many orders of magnitude. In particular, we observe that the many-pion correlation functions are well-approximated by log-normal distributions, allowing the extraction of the energies of these systems. Using these energies, the large-isospin-density, zero-baryon-density region of the QCD phase diagram is explored. A peak is observed in the energy density at an isospin chemical potential μ_I ~ 1.5m_π, signaling the transition into a Bose-Einstein condensed phase. The isentropic speed of sound, c_s, in the medium is seen to exceed the ideal-gas (conformal) limit ($$c^{2}_{s} ≤ 1/3)$$ over a wide range of chemical potential before falling towards the asymptotic expectation at μ_I ~ 15m_π. These, and other thermodynamic observables, indicate that the isospin chemical potential must be large for the system to be well described by an ideal gas or perturbative QCD.

• Research Organization: Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP); National Science Foundation (NSF); USDOE Office of Science (SC), Nuclear Physics (NP); USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR). Scientific Discovery through Advanced Computing (SciDAC)
• Contributing Organization: NPLQCD Collaboration
• Grant/Contract Number: AC02-07CH11359; AC05-00OR22725; AC02-05CH11231; SC0011090; PHY-2019786; SC0023116
• OSTI ID: 1996937
• Report Number(s): MIT-CTP/5560; UMD-PP-023-03; FERMILAB-PUB-23-382-T; arXiv:2307.15014; oai:inspirehep.net:2682305; TRN: US2405171
• Journal Information: Physical Review. D., Vol. 108, Issue 11; ISSN 2470-0010
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English