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Fri, 04 May 2001 00:00:00 +0200Fri, 04 May 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 +0200Holographic Trace Anomaly and Cocycle of Weyl Group
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1190
Abstract: The behavior of the divergent part of the bulk AdS/CFT effective action is considered with respect to the special finite diffeomorphism transformations acting on the boundary as a Weyl transformation of the boundary metric. The resulting 1-cocycle of the Weyl group is in full agreement with the 1-cocycle of the Weyl group obtained from the cohomological consideration of the effective action of the corresponding CFT.R. Manvelyan; R. Mkrtchyan; H. J. W. Müller-Kirstenpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1190Thu, 05 Apr 2001 00:00:00 +0200Periodic 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 +0100Periodic Instanton Method and Macroscopic Quantum Tunneling between two weakly-linked Bose-Einstein Condensates
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1161
A new method is used to investigate the tunneling between two weakly-linked Bose-Einstein con- densates confined in double-well potential traps. The nonlinear interaction between the atoms in each well contributes to a finite chemical potential, which, with consideration of periodic instantons, leads to a remarkably high tunneling frequency. This result can be used to interpret the newly found Macroscopic Quantum Self Trapping (MQST) effect. Also a new kind of first-order crossover between different regions is predicted.Yunbo Zhang; H.J.W. Müller-Kirstenpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1161Fri, 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 +0100Gross-Ooguri Phase Transition at Zero and Finite Temperature: Two Circular Wilson Loop Case
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1183
Abstract: In the context of AdS/CFT correspondence the two Wilson loop correlator is examined at both zero and finite temperatures. On the basis of an entirely analytical approach we have found for Nambu-Goto strings the functional relation dSc(Reg) /dL = 2*pi*k between Euclidean action Sc and loop separation L with integration constant k, which corresponds to the analogous formula for point-particles. The physical implications of this relation are explored in particular for the Gross-Ooguri phase transition at finite temperature.Hungsoo Kim; D. K. Park; S. Tamaryan; H.J.W. Müller-Kirstenpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1183Fri, 16 Feb 2001 00:00:00 +0100Quantum Phase Interference for Quantum Tunneling in Spin Systems
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1179
Abstract: The point-particle-like Hamiltonian of a biaxial spin particle with external magnetic field along the hard axis is obtained in terms of the potential field description of spin systems with exact spin-coordinate correspondence. The Zeeman energy term turns out to be an effective gauge potential which leads to a nonintegrable phase of the Euclidean Feynman propagator. The phase interference between clockwise and anticlockwise under barrier propagations is recognized explicitly as the Aharonov-Bohm effect. An additional phase which is significant for quantum phase interference is discovered with the quantum theory of spin systems besides the known phase obtained with the semiclassical treatment of spin. We also show the energy dependence of the effect and obtain the tunneling splitting at excited states with the help of periodic instantons.J.-Q. Liang; H. J. W. Müller-Kirsten; D. K. Park; F.-C. Pupreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1179Fri, 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 +0100Macroscopic Quantum Coherence in Small Antiferromagnetic Particle and the Quantum Interference Effects
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1158
Starting from the Hamiltonian operator of the noncompensated two-sublattice model of a small antiferromagnetic particle, we derive the e effective Lagrangian of a biaxial antiferromagnetic particle in an external magnetic field with the help of spin-coherent-state path integrals. Two unequal level-shifts induced by tunneling through two types of barriers are obtained using the instanton method. The energy spectrum is found from Bloch theory regarding the periodic potential as a superlattice. The external magnetic field indeed removes Kramers' degeneracy, however a new quenching of the energy splitting depending on the applied magnetic field is observed for both integer and half-integer spins due to the quantum interference between transitions through two types of barriers.Yi-Hang Nie; Y.-B. Zhang; J.-Q. Liang; H.J.W. Müller-Kirsten; F.-C. Pupreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1158Fri, 09 Feb 2001 00:00:00 +0100Self-Duality beyond Chiral p-Form Actions
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1154
Abstract: The self-duality of chiral p-forms was originally investigated by Pasti, Sorokin and Tonin in a manifestly Lorentz covariant action with non-polynomial auxiliary fields. The investigation was then extended to other chiral p-form actions. In this paper we point out that the self-duality appears in a wider context of theoretical models that relate to chiral p-forms. We demonstrate this by considering the interacting model of Floreanini- Jackiw chiral bosons and gauge fields, the generalized chiral Schwinger model (GCSM) and the latter's gauge invariant formulation, and discover that the self-duality of the GCSM corresponds to the vector and axial vector current duality.Yan-Gang Miao; R. Manvelyan; H.J.W. Müller-Kirstenpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1154Fri, 09 Feb 2001 00:00:00 +0100Absorption Cross Section of Scalar Field in Supergravity Background
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1155
Abstract: It has recently been shown that the equation of motion of a massless scalar field in the background of some specific p branes can be reduced to a modified Mathieu equation. In the following the absorption rate of the scalar by a D3 brane in ten dimensions is calculated in terms of modified Mathieu functions of the first kind, using standard Mathieu coefficients. The relation of the latter to Dougall coefficients (used by others) is investigated. The S-matrix obtained in terms of modified Mathieu functions of the first kind is easily evaluated if known rapidly convergent low energy expansions of these in terms of products of Bessel functions are used. Leading order terms, including the interesting logarithmic contributions, can be obtained analytically.R. Manvelyan; H. J. W. Müller-Kirsten; J.-Q. Liang; Yunbo Zhangpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1155Fri, 09 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 +0100Self-Duality of Various Chiral Boson Actions
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1156
Abstract: The duality symmetries of various chiral boson actions are investigated using D = 2 and D = 6 space-time dimensions as examples. These actions involve the Siegel, Floreanini-Jackiw, Srivastava and Pasti-Sorokin-Tonin formulations. We discover that the Siegel, Floreanini-Jackiw and Pasti-Sorokin-Tonin actions have self-duality with respect to a common anti-dualization of chiral boson fields in D = 2 and D = 6 dimensions, respectively, while the Srivastava action is self-dual with respect to a generalized dualization of chiral boson fields. Moreover, the action of the Floreanini-Jackiw chiral bosons interacting with gauge fields in D = 2 dimensions also has self-duality but with respect to a generalized anti-dualization of chiral boson fields.Yan-Gang Miao; H.J.W. Müller-Kirstenpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1156Fri, 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 +0100Correspondence, Poincar'e Vacuum Stateand Greybody Factors in BTZ Black Holes
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/899
The greybody factors in BTZ black holes are evaluated from 2D CFT in the spirit of AdS3/CFT correspondence. The initial state of black holes in the usual calculation of greybody factors by effective CFT is described as Poincar'e vacuum state in 2D CFT. The normalization factor which cannot be fixed in the effective CFT without appealing to string theory is shown to be determined by the normalized bulk-to-boundary Green function. The relation among the greybody factors in different dimensional black holes is exhibited. Two kinds of (h; _h) = (1; 1) operators which couple with the boundary value of massless scalar field are discussed.Nobuyoshi Ohta; H.J.W. Müller-Kirsten; Jian-Ge Zhoupreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/899Mon, 03 Apr 2000 00:00:00 +0200BRST-Invariant Approach to Quantum Mechanical Tunneling
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/883
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.Jui-Qing Liang; H. J. W. Müller-Kirsten; F. Zimmerschied; Jiang-Ge Zhoupreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/883Mon, 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 +0200