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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 +0200Tunneling 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 +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 +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 +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 +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 +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 +0200Nonvacuum Preudoparticles, Quantum Tunneling and Metastability
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/882
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.Jui-Qing Liang; H.J.W. Müller-Kirstenpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/882Mon, 03 Apr 2000 00:00:00 +0200On Different Formulations of Chiral Bosons
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/898
It is shown, that recently constructed PST Lagrangians for chiral supergravities follow directly from earlier Kavalov-Mkrtchyan Lagrangians by an Ansatz for the ' tensor by expressing this in terms of the PST scalar. The susy algebra which included earlier ff-symmetry in the commutator of supersymmetry transformations, is now shown to include both PST symmetries, which arise from the single ff-symmetry term. The Lagrangian for the 5-brane is not described by this correspondence, and probably can be obtained from more general Lagrangians, posessing ff-symmetry.Ruben Manvelyan; H.J.W. Müller-Kirstenpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/898Mon, 03 Apr 2000 00:00:00 +0200Periodic instanton and phase transition in quantum tunneling of spin systems
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1068
Y. Zhang; Y. Nie; S. Kou; J.-Q. Liang; H.J.W. Müller-Kirsten; F.-C. Pupreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1068Fri, 10 Mar 2000 00:00:00 +0100Quantum-classical phase transition of escape rate in biaxial spin particles
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1069
Y.-B. Zhang; J.-Q. Liang; H.J.W. Müller-Kirsten; F.-C. Pupreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1069Fri, 10 Mar 2000 00:00:00 +0100