arXiv subjects

Jan B. Thomassen

Publications and source records attributed to Jan B. Thomassen.

7 recordsLinked to original sources

arXiv2001

Radiative corrections to the Casimir energy and effective field theory

We discuss radiative corrections to the Casimir effect from an effective field theory point of view. It is an improvement and more complete version of a previous discussion by Kong and Ravndal. By writing down the most general effective Lagrangian respecting the symmetries and the boundary conditions, we are able to reproduce earlier results of Bordag, Robaschik and Wieczorek calculated in full QED. They obtained the correction E_0^(1) = π^2α/2560mL^4 to the Casimir energy. We find that this leading correction is due to surface terms in the effective theory, which we attribute to having dominant fluctuations localized on the plates.

hep-th↗

arXiv2000

Bosonization in four dimensions: The smooth way

I investigate bosonization in four dimensions, using the smooth bosonization scheme. I argue that generalized chiral ``phases'' of the fermion field corresponding to chiral phase rotations and ``chiral Poincare transformations'' are the appropriate degrees of freedom for bosonization. Smooth bosonization is then applied to an Abelian fermion coupled to an external vector. The result is an exact rewriting of the theory, including the fermion, the bosonic fields, and ghosts. Exact bosonization is therefore not achieved since the fermion and the ghosts are not completely eliminated. The action for the bosons is given by the Jacobian of a change of variables in the path integral, and I calculate parts of this. The action describes a nonlinear field theory, and thus static, topologically stable solitons may exist in the bosonic sector of the theory, which become the fermions of the original theory after quantization.

hep-th↗

arXiv2000

Chiral anomalies and Poincare invariance

I study variations of the fermionic determinant for a nonabelian Dirac fermion with external vector and axial vector sources. I consider different regularizations, leading to different chiral anomalies when the variations are chiral transformations. For these different regularizations, I then consider variations associated with Poincare transformations. I find that both Lorentz and translational invariance are anomalously violated in general, but that they are respected when the variations of the determinant are regularized to give a Wess-Zumino consistent anomaly (the Bardeen anomaly). If the variations are regularized to give a covariant anomaly, then Poincare invariance is not respected. Following Manohar in an investigation of Poincare anomalies in a chiral gauge theory, this gives an alternative way to understand the need for a consistent regularization of the variations of the fermionic determinant.

hep-th↗

arXiv1999

Path Integral Bosonization of the Massive Thirring Model

There is a conceptual error in the main argument of this paper (essentially a regularization scheme is changed in the middle of a calculation), and therefore it is withdrawn. Interested readers are instead referred to hep-th/9811137.

hep-th↗

arXiv1999

Chiral Poincare transformations and their anomalies

I consider global transformations of a Dirac fermion field, that are generated by the generators of Poincar'e transformations, but with a γ_5 appended. Such chiral translations and chiral Lorentz transformations are usually not symmetries of the Lagrangian, but naively they are symmetries of the fermionic measure. However, by using proper time regularization in Minkowski space, I find that they in general give rise to a nontrivial Jacobian. In this sense they have "anomalies". I calculate these anomalies in a theory of a massive fermion coupled to an external Abelian vector field. My motivation for considering chiral Poincar'e transformations is the possibility that they are relevant to bosonization in four dimensions.

hep-th↗

arXiv1999

Jacobians of chiral transformations and two-dimensional bosonization

We formulate a complete path integral bosonization procedure for any fermionic theory in two dimensions. The method works equally well for massive and massless fermions, and is a generalization of an approach suggested earlier by Andrianov. The classical action of the bosons in the bosonized theory is identified with -i times the logarithm of the Jacobian of a local chiral transformation, with the boson fields as transformation parameters. Three examples, the Schwinger model, the massive Thirring model and massive non-Abelian bosonization, are worked out.

hep-th↗

arXiv1998

Two-Dimensional Bosonization from Variable Shifts in the Path Integral

A method to perform bosonization of a fermionic theory in (1+1) dimensions in a path integral framework is developed. The method relies exclusively on the path integral property of allowing variable shifts, and does not depend on the explicit form of Greens functions. Two examples, the Schwinger model and the massless Thirring model, are worked out.

hep-th↗