Massless mode and positivity violation in hot QCD

Area of Science:

• Quantum Chromodynamics (QCD)
• High-Temperature Physics
• Particle Physics

Background:

• Understanding quark behavior at high temperatures is crucial for studying the early universe and neutron stars.
• Previous models primarily focused on chromoelectric scales, potentially overlooking magnetic scale contributions.

Purpose of the Study:

• To calculate the quark self-energy at one-loop level at high temperatures.
• To investigate the impact of both chromoelectric and chromomagnetic scales on quark excitations.
• To analyze the resulting spectral functions and their implications for confinement.

Main Methods:

• One-loop level calculation of quark self-energy.
• Inclusion of contributions from both chromoelectric (gT) and chromomagnetic (g^2T) scales.
• Analysis of quark spectral functions.

Main Results:

• Standard massive excitations were reproduced, consistent with the chromoelectric scale.
• A novel massless excitation, attributed to the chromomagnetic scale, was discovered.
• The residue of this massless excitation was found to be nonpositive, leading to positivity violation in quark spectral functions.

Conclusions:

• Confinement effects significantly influence thermal quark collective excitations.
• The novel massless excitation and positivity violation demonstrate long-range correlations in the system.
• This work provides new insights into the complex dynamics of quarks in extreme thermal environments.