Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userChiral Phase Transition beyond Mean Field Approximation
96
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Based on the analogy between the Nambu--Jona-Lasinio model of chiral symmetry breaking and the BCS theory of superconductivity, we investigate the effect of $bar q q$ pair fluctuations on the chiral phase transition. We include uncondensed $bar q q$ pairs at finite temperature and chemical potential in a self-consistent T-matrix formalism, the so-called $G_0 G$ scheme. The pair fluctuations reduce significantly the critical temperature and make quarks massive above the critical temperature.
rate research
Read More
We study the dressing of four-quark interaction by the ring diagram in an effective chiral quark model. Implementing such an in-medium coupling naturally reduces the chiral transition temperature in a class of chiral models, and is capable of generating the inverse magnetic catalysis at finite temperatures. We also demonstrate the important role of confining forces, via the Polyakov loop, in a positive feedback mechanism which reinforces the inverse magnetic catalysis.
We study the effects of gauge-field fluctuations on the free energy of a homogeneous color superconductor in the color-flavor-locked (CFL) phase. Gluonic fluctuations induce a strong first-order phase transition, in contrast to electronic superconductors where this transition is weakly first order. The critical temperature for this transition is larger than the one corresponding to the diquark pairing instability. The physical reason is that the gluonic Meissner masses suppress long-wavelength fluctuations as compared to the normal conducting phase where gluons are massless, which stabilizes the superconducting phase. In weak coupling, we analytically compute the temperatures associated with the limits of metastability of the normal and superconducting phases, as well as the latent heat associated with the first-order phase transition. We then extrapolate our results to intermediate densities and numerically evaluate the temperature of the fluctuation-induced first-order phase transition, as well as the discontinuity of the diquark condensate at the critical point. We find that the London limit of magnetic interactions is absent in color superconductivity.
The bubble wall velocity is essential for the phase transition dynamics in the early universe and its cosmological implications, such as the energy budget of phase transition gravitational wave and electroweak baryogenesis. One key factor to determine the wall velocity is the collision term that quantifies the interactions between the massive particles in the plasma and the bubble wall. We improve the calculations of the collision term beyond the leading-log approximation, and further obtain more precise bubble wall velocity for a representative effective model.
We investigate the fluctuation effect of the di-fermion field in the crossover from Bardeen-Cooper-Schrieffer (BCS) pairing to a Bose-Einstein condensate (BEC) in a relativistic superfluid. We work within the boson-fermion model obeying a global U(1) symmetry. To go beyond the mean field approximation we use Cornwall-Jackiw-Tomboulis (CJT) formalism to include higher order contributions. The quantum fluctuations of the pairing condensate is provided by bosons in non-zero modes, whose interaction with fermions gives the two-particle-irreducible (2PI) effective potential. It changes the crossover property in the BEC regime. With the fluctuations the superfluid phase transition becomes the first order in grand canonical ensemble. We calculate the condensate, the critical temperature $T_{c}$ and particle abundances as functions of crossover parameter the boson mass.
We study the effect of periodic boundary conditions on chiral symmetry breaking and its restoration in Quantum Chromodynamics. As an effective model of the effective potential for the quark condensate, we use the quark-meson model, while the theory is quantized in a cubic box of size $L$. After specifying a renormalization prescription for the vacuum quark loop, we study the condensate at finite temperature, $T$, and quark chemical potential, $mu$. We find that lowering $L$ leads to a catalysis of chiral symmetry breaking. The excitation of the zero mode leads to a jump in the condensate at low temperature and high density, that we suggest to interpret as a gas-liquid phase transition that takes place between the chiral symmetry broken phase (hadron gas) and chiral symmetry restored phase (quark matter). We characterize this intermediate phase in terms of the increase of the baryon density, and of the correlation length of the fluctuations of the order parameter: for small enough $L$ the correlation domains occupy a substantial portion of the volume of the system, and the fluctuations are comparable to those in the critical region. For these reasons, we dub this phase as the {it subcritical liquid}. The qualitative picture that we draw is in agreement with previous studies based on similar effective models. We also clarify the discrepancy on the behavior of the critical temperature versus $L$ found in different models.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
