Ward Identities for Invariant Group Integrals (2006)
Uhlmann, S., Meinel, R., Wipf, A.
We derive two types of Ward identities for the generating functions for invariant integrals of monomials of the fundamental characters for arbitrary simple compact Lie groups. The results are applied...
Spectral asymmetry on the ball and asymptotics of the asymmetry kernel (2006)
Kirchberg, A., Kirsten, K., Santangelo, E. M., Wipf, A.
Let $\ui\di$ be the Dirac operator on a $D=2d$ dimensional ball $\mcB$ with radius $R$. We calculate the spectral asymmetry $\eta(0,\ui\di)$ for D=2 and D=4, when local chiral bag boundary conditions...
On the Observation of Vacuum Birefringence (2006)
Heinzl, T., Liesfeld, B., Amthor, K. -U., Schwoerer, H., Sauerbrey, R., Wipf, A.
We suggest an experiment to observe vacuum birefringence induced by intense laser fields. A high-intensity laser pulse is focused to ultra-relativistic intensity and polarizes the vacuum which then...
Algebraic Solution of the Supersymmetric Hydrogen Atom (2005)
Wipf, A., Kirchberg, A., Länge, J. D.
The N=2 supersymmetric extension of the Schr\"odinger-Hamiltonian with 1/r-potential in d dimension is constructed. The system admits a supersymmetrized Laplace-Runge-Lenz vector which extends the...
From the Dirac Operator to Wess-Zumino Models on Spatial Lattices (2004)
Kirchberg, A., Laenge, J. D., Wipf, A.
We investigate two-dimensional Wess-Zumino models in the continuum and on spatial lattices in detail. We show that a non-antisymmetric lattice derivative not only excludes chiral fermions but in...
Extended Supersymmetries and the Dirac Operator (2004)
Kirchberg, A., Laenge, J. D., Wipf, A.
We consider supersymmetric quantum mechanical systems in arbitrary dimensions on curved spaces with nontrivial gauge fields. The square of the Dirac operator serves as Hamiltonian. We derive a...
Algebraic Solution of the Supersymmetric Hydrogen Atom in d Dimensions (2002)
Kirchberg, A., Laenge, J. D., Pisani, P. A. G., Wipf, A.
In this paper the N=2 supersymmetric extension of the Schroedinger Hamiltonian with 1/r-potential in arbitrary space-dimensions is constructed. The supersymmetric hydrogen atom admits a conserved...
Spectral asymmetry for bag boundary conditions (2002)
Beneventano, C. G., Santangelo, E. M., Wipf, A.
We give an expression, in terms of boundary spectral functions, for the spectral asymmetry of the Euclidean Dirac operator in two dimensions, when its domain is determined by local boundary...
Pole structure of the Hamiltonian $\zeta$-function for a singular potential (2001)
Falomir, H., Pisani, P. A. G., Wipf, A.
We study the pole structure of the $\zeta$-function associated to the Hamiltonian $H$ of a quantum mechanical particle living in the half-line $\mathbf{R}^+$, subject to the singular potential $g...
Effective Theories of Confinement (2001)
Dittmann, L., Heinzl, T., Wipf, A.
We review some approaches to describe confinement in terms of effective (model) field theories. After a brief discussion of the dual Abelian Higgs model, we concentrate on a lattice analysis of the...
A lattice study of the Faddeev-Niemi effective action (2001)
Dittmann, L., Heinzl, T., Wipf, A.
We perform a lattice analysis of the Faddeev-Niemi effective action conjectured to describe the low energy sector of SU(2) Yang-Mills theory. We generalize the effective action such that it contains...
Nahm Transform and Moduli Spaces of CPn Models on the Torus (2001)
Aguado, M., Asorey, M., Wipf, A.
There is a Nahm transform for two-dimensional gauge fields which establishes a one-to-one correspondence between the orbit space of U(N) gauge fields with topological charge k defined on a torus and...
Magnetic monopoles vs. Hopf defects in the Laplacian (Abelian) gauge (2000)
Bruckmann, F., Heinzl, T., Vekua, T., Wipf, A.
We investigate the Laplacian Abelian gauge on the sphere S^4 in the background of a single `t Hooft instanton. To this end we solve the eigenvalue problem of the covariant Laplace operator in the...
ADHM Construction of Instantons on the Torus (2000)
Ford, C., Pawlowski, J. M., Tok, T., Wipf, A.
We apply the ADHM instanton construction to SU(2) gauge theory on T^n x R^(4-n)for n=1,2,3,4. To do this we regard instantons on T^n x R^(4-n) as periodic (modulo gauge transformations) instantons on...
Witten-Veneziano Relation for the Schwinger Model (2000)
Azakov, S., Joos, H., Wipf, A.
The Witten-Veneziano relation between the topological susceptibility of pure gauge theories without fermions and the main contribution of the complete theory and the corresponding formula of Seiler...
Instantons and Gribov Copies in the Maximally Abelian Gauge (2000)
Bruckmann, F., Heinzl, T., Tok, T., Wipf, A.
We calculate the Faddeev-Popov operator corresponding to the maximally Abelian gauge for gauge group SU(N). Specializing to SU(2) we look for explicit zero modes of this operator. Within an...
SU(N)-Gauge Theories in Polyakov Gauge on the Torus (1998)
We investigate the Abelian projection with respect to the Polyakov loop operator for SU(N) gauge theories on the four torus. The gauge fixed $A_0$ is time-independent and diagonal. We construct...
Abelian Projection on the Torus for general Gauge Groups (1998)
We consider Yang-Mills theories with general gauge groups $G$ and twists on the four torus. We find consistent boundary conditions for gauge fields in all instanton sectors. An extended Abelian...
Monopoles, Polyakov-Loops and Gauge Fixing on the Torus (1998)
Ford, C., Mitreuter, U. G., Pawlowski, J., Tok, T., Wipf, A.
We consider pure Yang Mills theory on the four torus. A set of non-Abelian transition functions is presented which encompass all instanton sectors. It is argued that these transition functions are a...
Polyakov-Loops and Fermionic Zero Modes in QCD2 on the Torus (1996)
Mitreuter, U. G., Pawlowski, J. M., Wipf, A.
A simple derivation of the free energy and expectation values of Polyakov-loops in $QCD_2$ via path integral methods is given. In the chosen gauge (which can be generalized to 4 dimensions) without...
Generalized Thirring Models (1995)
The Thirring model and various generalizations of it are analyzed in detail. The four-Fermi interaction modifies the equation of state. Chemical potentials and twisted boundary conditions both result...
Running surface couplings (1995)
We discuss the renormalization group improved effective action and running surface couplings in curved spacetime with boundary. Using scalar self-interacting theory as an example, we study the...
Gauge Theories in a Bag (1994)
We investigate multi-flavour gauge theories confined in $d\es 2n$-dimensional Euclidean bags. The boundary conditions for the 'quarks' break the axial flavour symmetry and depend on a parameter...
On 4D-Hawing Radiation from Effective Action (1994)
Mukhanov, V., Wipf, A., Zelnikov, A.
We determine the $s$-waves contribution of a scalar field to the four dimensional effective action for arbitrary spherically symmetric external gravitational fields. The result is applied to...
On the Symmetries of Hamiltonian Systems (1994)
In this paper we show how the well-know local symmetries of Lagrangeans systems, and in particular the diffeomorphism invariance, emerge in the Hamiltonian formulation. We show that only the...
Temperature- and Curvature Dependence of the Chiral Symmetry Breaking in 2D Gauge Theories (1993)
The partition function and the order parameter for the chiral symmetry breaking are computed for a family of 2-dimensional interacting theories containing the gauged Thirring model. In particular we...
Conformal- and Thermodynamic Properties of a Family of Thirring-like Models (1993)
Sachs, I., Wipf, A., Dettki, A.
We investigate Thirring-like models containing fermionic and scalar fields propagating in 2-dimensional space time. The corresponding conformal algebra is studied and we disprove a conjecture...
Generalized Gauged Thirring Model on Curved Space-Times (1993)
Dettki, A., Sachs, I., Wipf, A.
We analyse the interacting theory of charged fermions, scalars, pseuso-scalars and photons propagating in 2-dimensional curved spacetime in detail. For certain values of the coupling constants the...
On the General Structure of Hamiltonian Reductions of the Wznw Theory (1991)
Feher, L., O'raifeartaigh, L., Ruelle, P., Tsutsui, I., Wipf, A.
The structure of Hamiltonian reductions of the Wess-Zumino-Novikov-Witten (WZNW) theory by first class Kac-Moody constraints is analyzed in detail. Lie algebraic conditions are given for ensuring the...