The effective systems corresponding to the infrared sector of the original continuum gauge theory are studied. The emphasis is on the phase-transition behavior. The effective potential is shown to display the features known in the Ginzburg-Landau theory. The phase transition depends on the value of the (renormalized) coupling constant. The numerical value of the critical coupling or the critical temperature is in agreement with lattice calculations.

A survey devoted to A,-condensate in gauge theories at high temperature is presented. Both theoretical foundations of the spontaneously generated condensate and known methods of its calculation are discussed. As the most important consequence, the S U ( N ) global symmetry breakdown is investigated in detail. The influence of A , on matter fields is studied in different aspects. Some new results concerning this subject are reported as well. 0. A. BORISENKO et al., A, Condensate in QCD know, there is no (mathematically) strict proof at the present time that the A,-condensate must disappear at high temperature. Nevertheless, we believe that calculation of the ( A , ) by different methods and, on the other hand, the derivation of the most significant consequences of such a condensate on multi-particle systems make our attempt quite justified. Besides, the appearance of the A,-condensate and the breakdown of global gauge symmetry can undoubtedly lead to significant improvement of our conception both of the high temperature behaviour of the strongly interacting matter and of the physics of gauge theories on the whole and surely have a connection to other problems currently under investigation (as, for instance, the infrared problem, the behaviour of quarks at non-zero baryonic number, etc.). All these questions will be considered in the paper.Let us begin with a comprehensive consideration of some known facts obtained from the studies of QCD. The Hamiltonian can be formally written as a sum of chromoelectric and chromomagnetic terms and has the following form in lattice version of the theory At finite temperature the behaviour of chromoelectric fields has been well studied both in the perturbative (in gz) region and especially in the non-perturbative one. As is generally known, in the strong coupling approximation the main contribution to the partition function results from the chromoelectric part in Eq. (l), because the chromomagnetic term, being proportional to g -2 , can be treated perturbatively in T . At high temperature, because of periodic boundary conditions, the gauge field configurations known as Polyakov loops develop a non-vanishing expectation value, which breaks global 2, symmetry ( Z ( N ) g l ) of the initial QCD-action and leads to deconfinement. As the Polyakov loops transform non-trivially under Z (Ql rotations, their non-zero expectation value could mean screening of Z(N)-charges (or static quarks) at T > zD (where KD is the critical temperature of the deconfinement phase transition). If this is the case, one may claim that there exists a physical quantity which characterizes the phenomenon of screening. This quantity is called the Debye mass and is defined in the continuum as the zero momentum limit of the time component of the vacuum polarization tensor, 1 g rni(T)= -II,,(L* 0, k,=0).(2)This definition gives a gauge invariant value for SU(N,) gauge theory with Nf massless fermions only in the lowest non-trivial order of the weak-coupling expansionThe calculation of no,, Eq.(2), in the two-loop ap...

Articles you may be interested in Förster resonance energy transfer, absorption and emission spectra in multichromophoric systems. II. Hybrid cumulant expansion J. Chem. Phys. 142, 094107 (2015); 10.1063/1.4908600 Förster resonance energy transfer, absorption and emission spectra in multichromophoric systems. I. Full cumulant expansions and system-bath entanglement A numerically exact path integral treatment of the absorption and emission spectra of open quantum systems is presented that requires only the straightforward solution of a stochastic differential equation. The approach converges rapidly enabling the calculation of spectra of large excitonic systems across the complete range of system parameters and for arbitrary bath spectral densities. With the numerically exact absorption and emission operators, one can also immediately compute energy transfer rates using the multi-chromophoric Förster resonant energy transfer formalism. Benchmark calculations on the emission spectra of two level systems are presented demonstrating the efficacy of the stochastic approach. This is followed by calculations of the energy transfer rates between two weakly coupled dimer systems as a function of temperature and system-bath coupling strength. It is shown that the recently developed hybrid cumulant expansion (see Paper II) is the only perturbative method capable of generating uniformly reliable energy transfer rates and emission spectra across a broad range of system parameters. C 2015 AIP Publishing LLC. [http://dx.