## Fachbereich Physik

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#### Year of publication

- 1995 (9) (remove)

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#### Keywords

- mass difference (1)
- massive neutrinos (1)
- solar neutrinos (1)

- On the Mass Difference of Neutrinos (1995)
- We calculate a relative neutrino mass difference of Delta m / m = 6 10^-9 at the one loop level in a two flavor model. If we combine our result with recently published possible solutions to the solar neutrino problem we can estimate a neutrino mass range of m = (0,12-0,19) eV .

- Nonvacuum Preudoparticles, Quantum Tunneling and Metastability (1995)
- It is shown that nonvacuum pseudoparticles can account for quantum tunneling and metastability. In particular the saddle- point nature of the pseudoparticles is demonstrated, and the evaluation of path-integrals in their neighbourhood. Finally the relation between instantons and bounces is used to derive a result conjectured by Bogomolny and Fateyev.

- BRST-Invariant Approach to Quantum Mechanical Tunneling (1995)
- A new approach with BRST invariance is suggested to cure the degeneracy problem of ill defined path integrals in the path- integral calculation of quantum mechanical tunneling effects in which the problem arises due to the occurrence of zero modes. The Faddeev-Popov procedure is avoided and the integral over the zero mode is transformed in a systematic way into a well defined integral over instanton positions. No special procedure has to be adopted as in the Faddeev-Popov method in calculating the Jacobian of the transformation. The quantum mechanical tunneling for the Sine-Gordon potential is used as a test of the method and the width of the lowest energy band is obtained in exact agreement with that of WKB calculations.

- 2D quantum dilaton gravitational Hamiltonian, boundary terms and new definition for total energy (1995)
- The ADM and Bondi mass for the RST model have been first discussed from Hawking and Horowitz's argument. Since there is a nonlocal term in the RST model, the RST lagrangian has to be localized so that Hawking and Horowitz's proposal can be carried out. Expressing the localized RST action in terms of the ADM formulation, the RST Hamiltonian can be derived, meanwhile keeping track of all boundary terms. Then the total boundary terms can be taken as the total energy for the RST model. Our result shows that the previous expression for the ADM and Bondi mass actually needs to be modified at quantum level, but at classical level, our mass formula can be reduced to that given by Bilal and Kogan [5] and de Alwis [6]. It has been found that there is a new contribution to the ADM and Bondi mass from the RST boundary due to the existence of the hidden dynamical field. The ADM and Bondi mass with and without the RST boundary for the static and dynamical solutions have been discussed respectively in detail, and some new properties have been found. The thunderpop of the RST model has also been encountered in our new Bondi mass formula.

- Oscillatory surface in-plane lattice spacing during growth of Co and Cu on a Cu(001) single crystal (1995)

- Greensite-Halpern stabilization of Ak singularities in the N -> infty limit (1995)
- The Greensite-Halpern method of stabilizing bottomless Euclidean actions is applied to zerodimensional O(N) sigma models with unstable \(A_k\) singularities in the \( N = \infty\) limit.

- Double Scaling Limits, Airy Functions and Multicritical Behaviour in O(N) Vektor Sigma Models (1995)
- O(N) vector sigma models possessing catastrophes in their action are studied. Coupling the limit N - > infinity with an appropriate scaling behaviour of the coupling constants, the partition function develops a singular factor. This is a generalized Airy function in the case of spacetime dimension zero and the partition function of a scalar field theory for positive spacetime dimension.

- Nonvacuum pseudoparticles, quantum tuneling and metastability (1995)
- Abstract: It is shown that nonvacuum pseudoparticles can account forquantum tunneling and metastability. In particular the saddle-point nature of the pseudoparticles is demonstrated, and the evaluation of path-integrals in their neighbourhood. Finally the relation between instantons and bounces is used to derive a result conjectured by Bogomolny andFateyev.