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Hugo Reinhardt

Publications and source records attributed to Hugo Reinhardt.

82 records · Page 5Linked to original sources
arXiv2002

On the Landau Ginzburg theory of MAG projected SU(2) lattice gauge theory

Maximal Abelian gauge fixing and subsequent Abelian projection of SU(2) lattice gauge theory defines closed trajectories of magnetic monopoles. These trajectories can be interpreted in terms of an effective scalar field theory of the MAG monopoles using the worldline representation of the functional determinants. Employing the monopole worldlines detected in the numerical simulation, we show that a scalar bound state exists. The screening mass $m$ of this state properly scales towards the continuum limit. We find m ~ 1.3 $GeV when the string tension sigma = 440 MeV is used as reference scale.

hep-lat↗
arXiv2002

Kamlah Expansion and Gauge Theories

In Yang-Mills theories, variational calculations of the Rayleigh-Ritz type face the problem that on the one hand, calculability puts severe constraints on the space of test wave functionals; on the other hand, the test wave functionals have to be gauge invariant. The conflict between the two requirements can be resolved by introducing a projector. In this paper we present an approach to approximating the projector in a way known and successfully employed in nuclear physics: the Kamlah expansion. We discuss it both for electrodynamics and for Yang-Mills theories to leading order in a perturbative expansion, and demonstrate that the results are compatible with what one would expect from perturbation theory.

hep-ph↗
arXiv2000

The Stefan-Boltzmann law: SU(2) versus SO(3) lattice gauge theory

We investigate the high temperature limit of SU(2) and SO(3) lattice gauge theory, respectively. In particular, we study the Stefan-Boltzmann constant in both cases. As is well known, the Stefan-Boltzmann constant extracted from SU(2) lattice gauge theory by incorporating finite size effects is smaller than the continuum value which assumes three gluon degrees of freedom. On the other hand, the extrapolation of our SO(3) lattice data comes much closer to the continuum value. This rises the question whether SU(2) and SO(3) lattice gauge theories represent different quantum theories in the continuum limit.

hep-lat↗
arXiv1997

Confinement and scaling of the vortex vacuum of SU(2) lattice gauge theory

The magnetic vortices which arise in SU(2) lattice gauge theory in center projection are visualized for a given time slice. We establish that the number of vortices piercing a given 2-dimensional sheet is a renormalization group invariant and therefore physical quantity. We find that roughly 2 vortices pierce an area of 1 fm^2.

hep-lat↗
arXiv1997

Effective potential for the order parameter of the SU(2) Yang-Mills deconfinement transition

The Polyakov loop variable serves as an order parameter to characterize the confined and deconfined phases of Yang-Mills theory. By integrating out the vector fields in the SU(2) Yang-Mills partition function in one-loop approximation, an effective action is obtained for the Polyakov loop to second order in a derivative expansion. The resulting effective potential for the Polyakov loop is capable of describing a second-order deconfinement transition as a function of temperature.

hep-th↗
arXiv1997

A New State Of Hadronic Matter At High Density

We propose in this article that if the chemical potential exceeds a critical value in dense hadronic medium, a first-order phase transition to a new state of matter with Lorentz symmetry spontaneously broken (in addition to the explicit breaking) takes place. As a consequence, light vector mesons get excited as ``almost'' Goldstone bosons. Since the light vector mesons dominantly couple to photons, the presence of these new vector mesons could lead to an enhancement in the dilepton production from dense medium at an invariant mass lower than the free-space vector-meson mass. We provide a low-energy quark model which demonstrates that the above scenario is a generic case for quark theories with a strong interaction in the vector channel. We discuss possible relevance of this phase to the phenomenon of the enhanced dilepton production at low invariant masses in relativistic heavy-ion collisions.

hep-ph↗
arXiv1997

Improving the signal-to-noise-ratio in lattice gauge theories

Renormalization of composite fields is employed to suppress the statistical noise in lattice gauge calculations. We propose a new action which differs from the standard Wilson action by ''irrelevant'' operators, but suppresses the fluctuations of the plaquette. We numerically study the Creutz ratios and find a scaling window. The SU(2) mass gap is estimated. We prove that the contributions of the ''irrelevant'' operators to the screening mass decrease towards the continuum limit. The results obtained from the action with noise suppression are compared with those of the standard Wilson action.

hep-lat↗
arXiv1996

A renormalizable extension of the NJL-model

The Nambu-Jona-Lasinio model is supplemented by the quark interaction generated by the one-gluon exchange. The employed gluon propagator exhibits the correct large momentum behavior of QCD, whereas the Landau-pole at low energies is screened. The emerging constituent quark model is one-loop renormalizable and interpolates between the phenomenologically successful Nambu-Jona-Lasinio model at low energies and perturbative QCD at high momenta. Consequently, the momentum dependence of the quark self-energy at high energy coincides with the prediction from perturbative QCD. The chiral phase transition is studied in dependence on the low energy four quark interaction strength in the Dyson-Schwinger equation approach. The critical exponents of the quark self-energy and the quark condensate are obtained. The latter exponent deviates from the NJL-result. Pion properties are addressed by means of the Bethe-Salpeter equation. The validity of the Gell-Mann-Oakes-Renner relation is verified. Finally, we study the conditions which are necessary to allow for an accurate estimate of observables by the NJL-model as well as the shortcoming of the NJL-model due to its inherent non-renormalizability.

hep-ph↗
arXiv1996

Restoration of chiral symmetry in quark models with effective one gluon exchange

The restoration of chiral symmetry at finite density and/or temperature is investigated in a wide class of one-gluon exchange models in the instantaneous approximation. If the effective quark interaction is less divergent than $1/k^2$ for small momentum transfer $k$, we obtain Gaussian critical exponents for the chiral phase transitions at finite temperature and density, respectively. In the opposite case, for an interaction diverging faster than $1/k^2$ in the infrared region, a qualitative different behavior of the quark self-energy near the critical Fermi momentum $k_c$ and the critical temperature $T_c$, respectively, is observed. In the first scenario, we find $k_c \approx 2 \ln 2 \; T_c$, which compares well with recent data from QCD lattice simulations.

hep-ph↗