abstract

By projecting the partition function on the “color”-singlet state, we investigate the Hosotani mechanism in the fermion-gauge boson plasma. The present toy-model analysis of the one-loop effective potential at finite temperature shows that the critical temperature of gauge symmetry breaking increases at higher temperature in the smaller volume.

abstract

A reduced form of the Dirac equation has been previously introduced and studied in the center-of-mass reference frame. In this work, we show that this equation can be written in a covariant form in a generic reference frame by using specific momentum variables. These variables are also consistent with the retardless form of the interaction of the model.

abstract

We apply our recently formulated Gluon Exchange Model (GEM) to baryon production in proton–nucleus reactions involving \(N\gt 1\) proton–nucleon collisions. We propose a description scheme for the process of soft color octet (gluon) exchange, based on the assumption that probabilities to form an effective diquark are equal for all allowed pairs of quarks. The latter effective diquark can form either from two valence, one valence and one sea, or from two sea quarks. Consequently, we calculate the probabilities for different color configurations involving diquarks of valence–valence, valence–sea, and sea–sea type. These probabilities appear to depend on the number of exchanged gluons, which results in increasing baryon stopping as a function of the number of proton–nucleon collisions in the nucleus. As such, the nuclear stopping power appears to be governed by the emergence of new color configurations as a function of \(N\) rather than by the energy loss of the original valence diquark. The advantage of our approach lies in its high predictive power which makes it verifiable by the new, precise data on proton and neutron production from the CERN SPS. The latter verification, and a set of predictions for the \(N\)-dependence of the baryon stopping process, are included in the letter.

abstract

In this paper, we analyze the role of central (\(t_0\)) and density-dependent (\(t_3\)) terms of the effective Skyrme interaction on the imaginary part of the optical potential, angular distributions, and analyzing powers of the low-energy neutron elastic scattering on a series of doubly closed shell nuclei in the framework of self-consistent mean-field approach and beyond. The central term is the leading term of the effective interaction, while the density-dependent term is well known to be an effective way to simulate the three-body interaction. To do it, the microscopic optical potential has been generated from the particle vibration coupling on top of the random-phase approximation collective states built from the particle–hole excitations on a mean-field calculation. It has been found that the contributions of (\(t_0,t_3\)) terms are dominant on the surface and in the interior of the absorption part. The effects of \(t_0\) term are the strongest among other terms. The obtained results show that, if the central and density-dependent terms are taken into account, the agreement on angular distributions is significantly improved, especially at the forward scattering angles. The two terms were also found to have strong yet unsystematic effects on analyzing power.

abstract

Quantum features of the baryon number fluctuations in subsystems of a hot and dense relativistic gas of fermions are analyzed. We find that the fluctuations in small systems are significantly different compared to their values known from the statistical physics, and diverge in the limit where the system size goes to zero. The numerical results obtained for a broad range of the thermodynamic parameters expected in heavy-ion collisions are presented. They can be helpful to interpret and shed new light on the experimental data.