https://doi.org/10.1140/epja/s10050-021-00494-9
Regular Article - Theoretical Physics
A finite box as a tool to distinguish free quarks from confinement at high temperatures
Institute of Physics, University of Graz, 8010, Graz, Austria
Received:
22
October
2020
Accepted:
13
May
2021
Published online:
5
June
2021
Above the pseudocritical temperature 
of chiral symmetry restoration a chiral spin symmetry (a symmetry of the color charge and of electric confinement) emerges in QCD. This implies that QCD is in a confining mode and there are no free quarks. At the same time correlators of operators constrained by a conserved current behave as if quarks were free. This explains observed fluctuations of conserved charges and the absence of the rho-like structures seen via dileptons. An independent evidence that one is in a confining mode is very welcome. Here we suggest a new tool how to distinguish free quarks from a confining mode. If we put the system into a finite box, then if the quarks are free one necessarily obtains a remarkable diffractive pattern in the propagator of a conserved current. This pattern is clearly seen in a lattice calculation in a finite box and it vanishes in the infinite volume limit as well as in the continuum. In contrast, the full QCD calculations in a finite box show the absence of the diffractive pattern implying that the quarks are confined.
© The Author(s) 2021
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