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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 +0100Tunneling of Born-Infeld Strings to D2-Branes
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1159
Abstract: A Born-Infeld theory describing a D2-brane coupled to a 4-form RR field strength is considered, and the general solutions of the static and Euclidean time equations are derived and discussed. The period of the bounce solutions is shown to allow a consideration of tunneling and quantum-classical transitions in the sphaleron region. The order of such transitions, depending on the strength of the RR field strength, is determined. A criterion is then derived to confirm these findings.D.K. Park; S. Tamaryan; Y.-G. Miao; H.J.W. Müller-Kirstenpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1159Fri, 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 +0100The Stability of D2-Branes in the Presence of an RR field
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1174
A Born-Infeld theory describing a D2-brane coupled to a 3-form RR potential is reconsidered in order to investigate the stability of its nonsingular solutions with finite energy. The condition of stability of the solutions is established and the stable solutions and their shape are determined.D.K. Park; S. Tamaryan; H.J.W. Müller-Kirstenpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1174Fri, 16 Feb 2001 00:00:00 +0100Universality or Non-Universality of Absorption Cross Sections for Extended Objects
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1175
Abstract: The calculation of absorption cross sections for minimal scalars in supergravity backgrounds is an important aspect of the investigation of AdS/CFT correspondence and requires a matching of appropriate wave functions. The low energy case has attracted particular attention. In the following the dependence of the cross section on the matching point is investigated. It is shown that the low energy limit is independent of the matching point and hence exhibits universality. In the high energy limit the independence is not maintained, but the result is believed to possess the correct energy dependence.D.K. Park; H. J. W. Müller-Kirstenpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1175Fri, 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 +0100D-Branes and their Absorptivity in Born-Infeld Theory
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1177
Abstract: Standard methods of nonlinear dynamics are used to investigate the stability of particles, branes and D-branes of abelian Born-Infeld theory. In particular the equation of small fluctuations about the D-brane is derived and converted into a modified Mathieu equation and - complementing earlier low-energy investigations in the case of the dilaton-axion system - studied in the high-energy domain. Explicit expressions are derived for the S-matrix and absorption and reflection amplitudes of the scalar fluctuation in the presence of the D-brane. The results confirm physical expectations and numerical studies of others. With the derivation and use of the (hitherto practically unknown) high energy expansion of the Floquet exponent our considerations also close a gap in earlier treatments of the Mathieu equation.D.K. Park; S.N. Tamaryan; H.J.W. Müller-Kirsten; Jian-zu Zhangpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1177Fri, 16 Feb 2001 00:00:00 +0100Winding Number Transitions in the Mottola-Wipf Model on a Circle
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1181
Abstract: Winding number transitions from quantum to classical behavior are studied in the case of the 1+1 dimensional Mottola-Wipf model with the space coordinate on a circle for exploring the possibility of obtaining transitions of second order. The model is also studied as a prototype theory which demonstrates the procedure of such investigations. In the model at hand we find that even on a circle the transitions remain those of first order.D.K. Park; H.J.W. Müller-Kirsten; J.-Q. Liangpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1181Fri, 16 Feb 2001 00:00:00 +0100Macroscopic Quantum Phase Interference in Antiferromagnetic Particles
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1178
Abstact. The tunnel splitting in biaxial antiferromagnetic particles is studied with a magnetic field applied along the hard anisotropy axis. We observe the oscillation of tunnel splitting as a function of the magnetic field due to the quantum phase interference of two tunneling paths of opposite windings. The oscillation is similar to the recent experimental result with Fe8 molecular clusters.Yi-Hang Nie; Yan-Hong Jin; J.-Q. Liang; H.J.W. Müller-Kirsten; D.K. Park; F.-C. Pupreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1178Fri, 16 Feb 2001 00:00:00 +0100Winding number transitions at finite temperature in the d = 2 Abelian-Higgs model
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1180
Abstract: Following our earlier investigations we examine the quantum-classical winding number transition in the Abelian-Higgs system. It is demonstrated that the winding number transition in this system is of the smooth second order type in the full range of parameter space. Comparison of the action of classical vortices with that of the sphaleron supports our finding.D.K. Park; H.J.W. Müller-Kirsten; J.-Q. Liangpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1180Fri, 16 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 +0100Periodic 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 +0200Quantum Tunneling and Phase Transitions in Spin Systems with an Applied Magnetic Field
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/897
Transitions from classical to quantum behaviour in a spin system with two degenerate ground states separated by twin energy barriers which are asymmetric due to an applied magnetic field are investigated. It is shown that these transitions can be interpreted as first- or second-order phase transitions depending on the anisotropy and magnetic parameters defining the system in an effective Lagrangian description.S.-Y. Lee; H. J. W. Müller-Kirsten; F. Zimmerschied; D.K. Parkpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/897Mon, 03 Apr 2000 00:00:00 +0200A condition for first order phase transitions in quantum mechanical tunneling models
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1070
H. J. W. Müller-Kirsten; D.K. Park; J.M.S. Ranapreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1070Fri, 10 Mar 2000 00:00:00 +0100