arXiv subjects

Georges Ripka

Publications and source records attributed to Georges Ripka.

7 recordsLinked to original sources

arXiv2009

Density functionals derived from Feynman diagrams

We construct a stationary density functional for the partition function from a chosen set of one (boson) line irreducible Feynman diagrams. The construction does not proceed by the inversion of a Legendre transform. It is formulated for fermions with Coulomb interactions, in which case a stationary functional of the particle density is contructed, as well as for nucleons interacting with mesons, which involves a stationary functional of several densities. The use of Kohn-Sham orbits is shown to be an unnecessary complication.

nucl-th↗

arXiv2008

The classical pion field in a nucleus

A self-consistent symmetry arises when the nucleon angular momentum j and the isospin t are coupled to a grand spin G. Closed G shells become sources of a classical pion field with a hedgehog shape. Although the amplitude of the pion field, as measured by the chiral angle, is small, it is found to perturb significantly the energies of the nucleon orbits.

nucl-th↗

arXiv2001

Solitons in nonlocal chiral quark models

Properties of hedgehog solitons in a chiral quark model with nonlocal regulators are described. We discuss the formation of the hedgehog soliton, the quantization of the baryon number, the energetic stability, the gauging and construction of Noether currents with help of path-ordered P-exponents, and the evaluation of observables. The issue of nonlocality is thoroughly discussed, with a focus on contributions to observables related to the Noether currents. It is shown that with typical model parameters the solitons are not far from the weak nonlocality limit. The methods developed are applicable to solitons in models with separable nonlocal four-fermion interactions.

hep-ph↗

arXiv1999

Non-local regularization of chiral quark models in the soliton sector

A chiral quark model is described which is regularized in terms of Lorentz invariant non-local interactions. The model is regularized to all loop orders and it ensures the proper quantization of the baryon number. It sustains bound hedgehog solitons which, after suitable centre of mass corrections, can adequately describe the nucleon.

hep-ph↗

arXiv1998

Solitons in a chiral quark model with non-local interactions

Hedgehog solitons are found in a chiral quark model with non-local interactions. The solitons are stable without the chiral-circle constraint for the meson fields, as was assumed in previous Nambu-Jona--Lasinio model with local interactions.

hep-ph↗

arXiv1996

The impossible regularization of the Nambu Jona-Lasinio model with vector interactions

We show that the procedure of regularizing the real part of the euclidean action, while leaving the imaginary part unregularized, leads to a non-analytic and highly singular functional of the fields. It is customary to work with an imaginary time component of the vector field, in order to avoid regularization of the anomalous processes. We show that this procedure is flawed by the fact that a stationary point of the action occurs for a real, not imaginary, time component of the vector field. Furthermore the action in the vicinity of the stationary point is singular. The regularized action is thus not suitable for an evaluation of the partition function using a saddle point method. We discuss proposed solutions to this problem, as well as other regularizations. They all lead to practical problems.

hep-ph↗

arXiv1994

Macroscopic Chromodynamics of a Confining Medium

A nonminimal interaction of the gluon field with a massive antisymmetric tensor order parameter is shown to yield a vanishing dielectric function at tree level. The London-type description of this perfect diaelectric suggests a tractable non-Abelian chromodynamics of the Ginzburg-Landau type which is suitable for describing the confinement-deconfinement phase transition.

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