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Fri, 16 Feb 2001 00:00:00 +0100Fri, 16 Feb 2001 00:00:00 +0100Periodic Bounce for Nucleation Rate at Finite Temperature in Minisuperspace Models
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1182
Abstract: The periodic bounce configurations responsible for quantum tunneling are obtained explicitly and are extended to the finite energy case for minisuperspace models of the Universe. As a common feature of the tunneling models at finite energy considered here we observe that the period of the bounce increases with energy monotonically. The periodic bounces do not have bifurcations and make no contribution to the nucleation rate except the one with zero energy. The sharp first order phase transition from quantum tunneling to thermal activation is verified with the general criterions.J.-Q. Liang; H. J. W. Müller-Kirsten; Y.-B. Zhang; A.V. Shurgaia; S.-P Kou; D.K. Parkpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1182Fri, 16 Feb 2001 00:00:00 +0100Functional Relation of interquark potential with interquark distance
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1160
Abstract: The functional relation between interquark potential and interquark distance is explicitly derived by considering the Nambu-Goto action in the AdS5 X S 5 background. It is also shown that a similar relation holds in a general background. The implications of this relation for confinement are briefly discussed.D.K. Park; H.J. W. Müller-Kirsten; A. V. Shurgaiapreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1160Fri, 16 Feb 2001 00:00:00 +0100Instanton-Sphaleron transition in the d = 2 Abelian-Higgs model on a Circle
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1176
Abstract: The transition from the instanton-dominated quantum regime to the sphaleron-dominated classical regime is studied in the d = 2 abelian-Higgs model when the spatial coordinate is compactified to S1. Contrary to the noncompactified case, this model allows both sharp first-order and smooth second-order transitions depending on the size of the circle. This finding may make the model a useful toy model for the analysis of baryon number violating processes.D.K. Park; H. J. W. Müller-Kirsten; J.-Q. Liang; A. V. Shurgaiapreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1176Fri, 16 Feb 2001 00:00:00 +0100Particle with torsion on 3d null-curves
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1157
We consider a (2 + 1)-dimensional mechanical system with the Lagrangian linear in the torsion of a light-like curve. We give Hamiltonian formulation of this system and show that its mass and spin spectra are defined by one-dimensional nonrelativistic mechanics with a cubic potential. Consequently, this system possesses the properties typical of resonance-like particles.A. Nersessian; R. Manvelyan; H.J.W. Müller-Kirstenpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1157Fri, 09 Feb 2001 00:00:00 +0100Finite Temperature Tunneling and Phase Transitions in SU(2)-Gauge Theory
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1151
A pure Yang-Mills theory extended by addition of a quartic term is considered in order to study the transition from the quantum tunneling regime to that of classical, i.e. thermal, behaviour. The periodic field confiurations are found, which interpolate between the vacuum and sphaleron field configurations. It is shown by explicit calculation that only smooth second order transitions occur for all permissible values of the parameter A introduced with the quartic term. The theory is one of the rare cases which canbe handled analytically.A.V. Shurgaia; H. J. W. Müller-Kirsten; J.-Q. Liang; D.K. Parkpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1151Mon, 22 Jan 2001 00:00:00 +0100Nucleation at Finite Temperature Beyond the Superminispace Model
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1152
Abstract: The transition from the quantum to the classical regime of the nucleation of the closed Robertson-Walker Universe with spacially homogeneous matter fields is investigated with a perturbation expansion around the sphaleron configuration. A criterion is derived for the occurrence of a first-order type transition, and the related phase diagram for scalar and vector fields is obtained. For scalar fields both the first and second order transitions can occur depending on the shape of the potential barrier. For a vector field, here that of an O (3) nonlinear o-model, the transition is seen to be only of the first order. PACS numbers: 11.15.Kc, 03.65Sq, 05.70.Fh, 98.80.CqJ.-Q. Liang; H. J. W. Müller-Kirsten; D.K. Park; A. V. Shurgaiapreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1152Mon, 22 Jan 2001 00:00:00 +0100Light-Cone Formulation of Super D2-Brane
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/900
The light-cone Hamiltonian approach is applied to the super D2- brane, and the equivalent area-preserving and U(1) gauge-invariant effective Lagrangian, which is quadratic in the U(1) gauge field, is derived. The latter is recognised to be that of the three- dimensional U(1) gauge theory, interacting with matter supermultiplets, in a special external induced supergravity metric and the gravitino field, depending on matter fields. The duality between this theory and 11d supermembrane theory is demonstrated in the light-cone gauge.Ruben Manvelyan; H. J. W. Müller-Kirsten; A. Melikyan; R. Mkrtchyanpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/900Mon, 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 +0200Anisotropic magnetic coupling of permalloy micron dots forming a square lattice
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/926
Static magnetic and spin wave properties of square lattices of permalloy micron dots with thicknesses of 500 Å and 1000 Å and with varying dot separations have been investigated. A magnetic fourfold anisotropy was found for the lattice with dot diameters of 1 micrometer and a dot separation of 0.1 micrometer. The anisotropy is attributed to an anisotropic dipole-dipole interaction between magnetically unsaturated parts of the dots. The anisotropy strength (order of 100000 erg/cm^3 ) decreases with increasing in-plane applied magnetic field.Christoph Mathieu; Martin Bauer; Oliver Büttner; Steffen Riedling; Björn Roos; Serguei Demokritov; Burkard Hillebrands; C. Hartmann; B. Bartenlian; C. Chappert; D. Decanini; F. Rousseaux; E. Cambril; A. Müller; B. Hoffmann; U. Hartmannarticlehttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/926Wed, 01 Jan 1997 00:00:00 +0100Static and dynamic properties of patterned magnetic permalloy films
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/930
Static magnetic and spin wave properties of square lattices of permalloy micron dots with thicknesses of 500 Å and 1000 Å and with varying dot separations have been investigated. The spin wave frequencies can be well described taking into account the demagnetization factor of each single dot. A magnetic four-fold anisotropy was found for the lattice with dot diameters of 1 micrometer and a dot separation of 0.1 micrometer. The anisotropy is attributed to an anisotropic dipole-dipole interaction between magnetically unsaturated parts of the dots. The anisotropy strength (order of 100000 erg/cm^3 ) decreases with increasing in-plane applied magnetic field.Burkard Hillebrands; Christoph Mathieu; C. Hartmann; Martin Bauer; Oliver Büttner; Steffen Riedling; Björn Roos; Serguei Demokritov; B. Bartenlian; C. Chappert; D. Decanini; F. Rousseaux; E. Cambril; A. Müller; B. Hoffmann; U. Hartmannarticlehttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/930Wed, 01 Jan 1997 00:00:00 +0100