Gluon

Tracing the historical development of quantum physics, the author describes the baffling and seemingly lawless world of leptons, hadrons, gluons and quarks and provides a lucid and exciting guide for the layman to the world of infinitesimal particles. 

Xn an entiraly different wetter. X have been reading and thinking about the proton and quarks. The 9en r l wey how Nobel Prises have been given seems to be far from proper, but 1 obviously hava no influence. The second point is that the whole discussion of quarks and gluons is a little unconvincing. I hava even triad soma improvement on the way to look at the problem. I hava nothing really to report, but t continue to worry. 

Despite the successes, even with its generalizations, difficulties in thermal field theory remain to be overcome in order to deal with experimental and theoretical demands. In fact, numerous studies, in particular using quantum chromodynamics (A. Smilga, 2001), have been carried out in an attempt to understand, for instance, the quark-gluon plasma at finite temperature and in this common effort, some underlying aspects have been identified. For example, the coupling constants for 7r,a,w and p mesons decrease to zero at a certain critical temperature, which are, respectively, given by = 360 MeV, Tj = 95... 

It is interesting to note that we have calculated the casimir pressure at finite temperature for parallel plates, a square wave-guide and a cubic box. For a fermion field in a cubic box with an edge of 1.0 fm, which is of the order of the nuclear dimensions, the critical temperature is 100 MeV. Such a result will have implications for confinement of quarks in nucleons. However such an analysis will require a realistic calculation, a spherical geometry, with full account of color and flavor degrees of freedom of quarks and gluons. 

Figure 8. Histograms of the nearest-neighbor spacing distribution for the nucleon (left plots) and the delta (right plots). The data is for Goldstone-boson exchange and for one-gluon exchange compared to a pure linear confinement potential of the same strength. Curves represent the Poisson and the GOE-Wigner distributions.

It was found that normal zero-point oscillations lie on top of large gluon fluctuations - instantons and anti-instantons with random positions and sizes. The left column - action density and the right column - topological charge density. Here instantons are peaks and anti-instantons are holes. 

Matsui, T. and H. Satz. J/T suppression by quark-gluon plasma formation. Physics Letters B, 178 416, 1986. 

Thus we have treated the chaotic dynamics of the quarkonium in a time periodic field. Using the Chirikov s resonance overlap criterion we obtain estimates for the critical value of the external field strength at which chaotization of the quarkonium motion will occur. The experimental realization of the quarkonium motion under time periodic perturbation could be performed in several cases in laser driven mesons and in quarkonia in the hadronic or quark-gluon matter. 

In the simplest approximation we consider an ideal quantum gas of elementary particles such as protons, neutrons, electrons and possibly neutrinos (the quark-gluon substructure will not be considered at densities and temperatures considered). The EOS is found in textbooks and will not be discussed any further here. 

We first review briefly the description of the bulk properties of uniform quark matter, deconfined from the /3-stable hadronic matter mentioned in the previous section, by using the MIT bag model [31]. The thermodynamic potential of f = u,d,s quarks can be expressed as a sum of the kinetic term and the one-gluon-exchange term [32, 33] proportional to the QCD fine structure... 

Phenomenological quasiparticle model. Taking into account only the dominant contributions in (7), namely the quasiparticle contributions of the transverse gluons as well as the quark particle-excitations for Nj / 0, we arrive at the quasiparticle model [8], The dispersion relations can be even further simplified by their form at hard momenta, u2 h2 -rnf, where m.t gT are the asymptotic masses. With this approximation of the self-energies, the pressure reads in analogy to the scalar case... 

The phenomenological quasiparticle model can be generalized to non-zero chemical potential, where the quasiparticle masses of the gluons and quarks read... 

The spectrum in the 2SC state is made of 5 massive Gluons with a mass of the order of the gap, 3 massless Gluons confined (at zero temperature) into light glueballs and gapless up and down quarks in the direction (say) 3 of color. 

The double trace term is due to the absence of the condition for the vanishing of the trace for the broken generator X5. It emerges naturally in the non linear realization framework at the same order in derivative expansion with respect to the single trace term. In the unitary gauge these two terms correspond to the five gluon masses [431. 

Figure 4 Tree-level matching Four-Fermi interaction due to hard gluons...

For instance, a one-light particle irreducible amplitude in QCD of two gluons and two quarks is matched as... 

While, in the BCS theory, such attractive force for electron Cooper pair is provided by phonons, for dense quark matter, where phonons are absent, the gluon exchange interaction provides the attraction, as one-gluon exchange interaction is attractive in the color anti-triplet channel1 One therefore expects that color anti-triplet Cooper pairs will form and quark matter is color superconducting, which is indeed shown more than 20 years ago [13, 14],... 

At intermediate density, quarks and gluons are strongly interacting and gluons are therefore presumably screened. Then, QCD at intermediate density may be modeled by four-Fermi interactions and higher-order terms by massive gluons. 

Integrating out the fast modes, modes far from the Fermi surface and hard gluons, the QCD partition function (1) becomes... 

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