Physics

Renormalization

Resummation

QCD matter

Particle physics

Quantum chromodynamics

Engineering

Coupling (piping)

Effective field theory

Nuclear matter

Nucleon

Neutron star

Quantum electrodynamics

Quantum mechanics

Strange matter

Equation of state

Quark

Mechanical engineering

Physical Review Letters

Accurate knowledge of the thermodynamic properties of zero-temperature, high-density quark matter plays an integral role in attempts to constrain the behavior of the dense QCD matter found inside neutron-star cores, irrespective of the phase realized inside the stars. In this Letter, we consider the weak-coupling expansion of the dense QCD equation of state and compute the next-to-next-to-next-to-leading-order contribution arising from the non-Abelian interactions among long-wavelength, dynamically screened gluonic fields. Accounting for these interactions requires an all-loop resummation, which can be performed using hard-thermal-loop (HTL) kinematic approximations. Concretely, we perform a full two-loop computation using the HTL effective theory, valid for the long-wavelength, or soft, modes. We find that the soft sector is well behaved within cold quark matter, contrary to the case encountered at high temperatures, and find that the new contribution decreases the renormalization-scale dependence of the equation of state at high density.

Soft Interactions in Cold Quark Matter