TY - JOUR

T1 - New approach to lattice QCD at finite density

T2 - 38th International Symposium on Lattice Field Theory, LATTICE 2021

AU - Pásztor, Attila

AU - Borsányi, Szabolcs

AU - Fodor, Zoltán

AU - Giordano, Matteo

AU - Kapás, Kornél

AU - Katz, Sándor D.

AU - Nógrádi, Dániel

AU - Wong, Chik Him

N1 - Funding Information:
The project was supported by the BMBF Grant No. 05P18PXFCA. This work was also supported by the Hungarian National Research, Development and Innovation Office, NKFIH grant KKP126769. A.P. is supported by the J. Bolyai Research Scholarship of the Hungarian Academy of Sciences and by the ÚNKP-21-5 New National Excellence Program of the Ministry for Innovation and Technology from the source of the National Research, Development and Innovation Fund. The authors gratefully acknowledge the Gauss Centre for Supercomputing e.V. (www.gauss-centre.eu) for funding this project by providing computing time on the GCS Supercomputers JUWELS/Booster and JURECA/Booster at FZ-Juelich.
Publisher Copyright:
© Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0)

PY - 2022/7/8

Y1 - 2022/7/8

N2 - Approaches to finite baryon density lattice QCD usually suffer from uncontrolled systematic uncertainties in addition to the well-known sign problem. We test a method - sign reweighting - that works directly at finite chemical potential and is yet free from any such uncontrolled systematics: with this approach the only problem is the sign problem itself. In practice the approach involves the generation of configurations with the positive fermionic weights given by the absolute value of the real part of the quark determinant, and a reweighting by a sign. There are only two sectors, +1 and -1 and as long as the average h±i ≠ 0 (with respect to the positive weight) this discrete reweighting has no overlap problem - unlike reweighting from μ = 0 - and the results are reliable. We also present results based on this algorithm on the phase diagram of lattice QCD with two different actions: as a first test, we apply the method to calculate the position of the critical endpoint with unimproved staggered fermions at Nτ = 4; as a second application, we study the phase diagram with 2stout improved staggered fermions at Nτ = 6. This second one is already a reasonably fine lattice - relevant for phenomenology. We demonstrate that the method penetrates the region of the phase diagram where the Taylor and imaginary chemical potential methods lose predictive power.

AB - Approaches to finite baryon density lattice QCD usually suffer from uncontrolled systematic uncertainties in addition to the well-known sign problem. We test a method - sign reweighting - that works directly at finite chemical potential and is yet free from any such uncontrolled systematics: with this approach the only problem is the sign problem itself. In practice the approach involves the generation of configurations with the positive fermionic weights given by the absolute value of the real part of the quark determinant, and a reweighting by a sign. There are only two sectors, +1 and -1 and as long as the average h±i ≠ 0 (with respect to the positive weight) this discrete reweighting has no overlap problem - unlike reweighting from μ = 0 - and the results are reliable. We also present results based on this algorithm on the phase diagram of lattice QCD with two different actions: as a first test, we apply the method to calculate the position of the critical endpoint with unimproved staggered fermions at Nτ = 4; as a second application, we study the phase diagram with 2stout improved staggered fermions at Nτ = 6. This second one is already a reasonably fine lattice - relevant for phenomenology. We demonstrate that the method penetrates the region of the phase diagram where the Taylor and imaginary chemical potential methods lose predictive power.

UR - http://www.scopus.com/inward/record.url?scp=85134428005&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85134428005&partnerID=8YFLogxK

M3 - Conference article

AN - SCOPUS:85134428005

SN - 1824-8039

VL - 396

JO - Proceedings of Science

JF - Proceedings of Science

M1 - 128

Y2 - 26 July 2021 through 30 July 2021

ER -