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Thu, 05 Apr 2001 00:00:00 +0200Thu, 05 Apr 2001 00:00:00 +0200Nonvacuum pseudoparticles, quantum tuneling and metastability
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1189
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.Jiu-Qing Liang; H.J.W. Müller-Kirstenpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1189Thu, 05 Apr 2001 00:00:00 +0200Instanton Induced Tunneling Amplitude At Excited States With The LSZ Method
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/889
Quantum tunneling between degenerate ground states through the central barrier of a potential is extended to excited states with the instanton method. This extension is achieved with the help of an LSZ reduction technique as in field theory and may be of importance in the study of macroscopic quantum phenomena in magnetic systems.H. J. W. Müller-Kirsten; Jiu-Qing Liang; J.-G. Zhou; J. Burzlaffpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/889Mon, 03 Apr 2000 00:00:00 +0200Application of Instatons: Quenching Of Macroscopic Quantum Coherence And Macroscopic Fermi-Particle Configurations
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/890
Starting from the coherent state representation of the evolution operator with the help of the path-integral, we derive a formula for the low-lying levels E = ffl0 Gamma 24ffl cos(s + ,)ss of a quantum spin system. The quenching of macroscopic quantum coherence is understood as the vanishing of cos(s + ,)ss in disagreement with the suppression of tunneling (i.e. 4ffl = 0) as claimed in the literature. A new configuration called the macroscopic Fermi-particle is suggested by the character of its wave function. The tunne- ling rate ( 24fflss ) does not vanish, not for integer spin s nor for a half-integer value of s, and is calculated explicitly (for the position dependent mass) up to the one-loop approximation.H. J. W. Müller-Kirsten; Jiu-Qing Liang; Jian-Ge Zhoupreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/890Mon, 03 Apr 2000 00:00:00 +0200Simple Calculation of Quantum Spin Tunneling Effects
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/891
The level splitting formulae much discussed in the study of spin tunneling in macroscopic ferromagnetic particles and previously derived only by complicated pseudoparticle methods for the ground state, are derived from those of eigenvalues of periodic equations and extended to excited states.Jiu-Qing Liang; H. J. W. Müller-Kirsten; J. M. Singh Ranapreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/891Mon, 03 Apr 2000 00:00:00 +0200Enhancement of Quantum Tunneling for Excited States in Ferromagnetic Particles
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/894
A formula suitable for a quantitative evaluation of the tunneling effect in a ferromagnetic particle is derived with the help of the instanton method. The tunneling between n-th degenerate states of neighboring wells is dominated by a periodic pseudoparticle configuration. The low-lying level-splitting previously obtained with the LSZ method in field theory in which the tunneling is viewed as the transition of n bosons induced by the usual(vacuum) instanton is recovered.The observation made with our new result is that the tunneling effect increases at excited states. The results should be useful in analyzing results of experimental tests of macroscopic quantum coherence in ferromagnetic particles.Jiu-Qing Liang; H. J. W. Müller-Kirsten; F. Zimmerschied; Y.-B. Zhang; Jian-Ge Zhou; F.-C. Pupreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/894Mon, 03 Apr 2000 00:00:00 +0200Calculation of Spin Tunneling Effects in the Presence of an Applied Magnetic Field
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/895
The tunneling splitting of the energy levels of a ferromagnetic particle in the presence of an applied magnetic field - previously derived only for the ground state with the path integral method - is obtained in a simple way from Schr"odinger theory. The origin of the factors entering the result is clearly understood, in particular the effect of the asymmetry of the barriers of the potential. The method should appeal particularly to experimentalists searching for evidence of macroscopic spin tunneling.Jiu-Qing Liang; H. J. W. Müller-Kirsten; F. Zimmerschied; A.V. Shurgaiapreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/895Mon, 03 Apr 2000 00:00:00 +0200Periodic Instantons and Quantum-Classical Transitions in Spin Systems
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/896
The tunneling splitting of the energy levels of a ferromagnetic particle in the presence of an applied magnetic field - previously derived only for the ground state with the path integral method - is obtained in a simple way from Schr"odinger theory. The origin of the factors entering the result is clearly understood, in particular the effect of the asymmetry of the barriers of the potential. The method should appeal particularly to experimentalists searching for evidence of macroscopic spin tunneling.Jiu-Qing Liang; H. J. W. Müller-Kirsten; F. Zimmerschied; D.K. Parkpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/896Mon, 03 Apr 2000 00:00:00 +02002D quantum dilaton gravitational Hamiltonian, boundary terms and new definition for total energy
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/902
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.H. J. W. Müller-Kirsten; Jian-Ge Zhou; Yan-Gang Miao; Jiu-Qing Liangpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/902Mon, 03 Apr 2000 00:00:00 +0200