arXiv subjects
Publications and source records attributed to K. Sailer.
The RG flow for the sine-Gordon model is determined by means of the method of Wegner and Houghton in next-to-leading order of the derivative expansion. For small values of the fugacity this agrees with the well-known RG flow of the two-dimensional Coulomb-gas found in the dilute gas approximation and a systematic way of obtaining higher-order corrections to this approximation is given.
The renormalization of the periodic potential is investigated in the framework of the Euclidean one-component scalar field theory by means of the differential RG approach. Some known results about the sine-Gordon model are recovered in an extremely simple manner. There are two phases, an ordered one with asymptotical freedom and a disordered one where the model is non-renormalizable and trivial. The order parameter of the periodicity, the winding number, indicates spontaneous symmetry breaking in the ordered phase where the fundamental group symmetry is broken and the solitons acquire dynamical stability. It is argued that the periodicity and the convexity are so strong constraints on the effective potential that it always becomes flat. This flattening is reproduced by integrating out the RG equation.
It is shown that the vacuum of QED$_2$ in Minkowski spacetime does not favour a periodic electric mean field. The projected effective action exhibiting a genuine dependence on the non-vanishing background field has been introduced. The functional dependence of the energy density of the vacuum on the assumed periodic vacuum expectation value of the vector potential is determined from the component $T^{00}$ of the energy-momentum tensor at one-loop order. Treating the background field non-perturbatively, the energy of the vacuum in the presence of a periodic mean field is found not be equal to the negative of the effective action.
In this paper the Dynamical String Model is applied to the numerical simulation of the ultrarelativistic heavy-ion collision S(200 GeV/n)+S. The results are in qualitative agreement with experimental data.
The Rarita-Schwinger equations are generalised for the delta baryon having spin 3/2 and isospin 3/2. The coupling of the nucleon and the delta fields is studied. A possible generalisation of the Walecka model is proposed.
The phase structure of the scalar field theory with arbitrary powers of the gradient operator and a local non-analytic potential is investigated by the help of the RG in Euclidean space. The RG equation for the generating function of the derivative part of the action is derived. Infinitely many non-trivial fixed points of the RG transformations are found. The corresponding effective actions are unbounded from below and do probably not exhibit any particle content. Therefore they do not provide physically sensible theories.
The time dependent pion emission rate and the mean life time of the pion source in the center of mass frame of the two-jet events have been determined for $e^+-e^- \to hadrons$ at $\sqrt{s} = 20 - 50$ GeV by the Dynamical String Model. It was established that the time needed for the creation of the pion source is $5$ fm/c, whereas its life time is $τ_0 \approx 7 - 13$ fm/c for energies $\sqrt{s} = 20 - 50$ GeV, respectively.
It is shown that the renormalized finite temperature effective potential for continuum $SU(2)$ Yang-Mills theory develops a non-perturbative minimum for sufficiently strong coupling, i.e. below a critical temperature. The corresponding phase can be the candidate for the confining phase of the continuum theory and becomes energetically favoured basicly due to the decay of the $A^0$ condensate into three gluons.
Including the Haar measure we show that the effective potential of the regularized SU(2) Yang-Mills theory has a minimum at vanishing Wilson-line $W=0$ for strong coupling, whereas it develops two degenerate minima close to $W=\pm 1$ for weak coupling. This suggests that the non-abelian character of $SU(2)$ as contained in the Haar measure might be responsible for confinement.
Retaining only the `timelike' component $A_0$ of the vector potential a skelet model with explicit global center symmetry is constructed for $SU(2)$ Yang-Mills theory. It is shown that the $A_0$ gluon vacuum is equivalent with the 4-dimensional Coulomb-gas. In 1--loop approximation, the effective theory of the skelet model exhibits non-local self-interaction. A coupling constant $λ$ is found that governs the loop expansion. For $λ< 1$ the effective theory does not confine (the string tension vanishes), whereas for $λ= 1$ confinement (with non-vanishing string tension) takes place. In the deconfined phase the $A_0$ gluons exhibit non-zero rest mass and global center symmetry is broken by the vacuum state. Confinement sets on for $λ=1$ when the rest mass of $A_0$ gluons vanishes and the global center symmetry of the vacuum is restored.