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Fri, 28 Sep 2001 00:00:00 +0200Fri, 28 Sep 2001 00:00:00 +0200Physikalisches Praktikum für Anfänger Teil C
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1319
Anleitung zu zwölf physikalischen Versuchen im Rahmen des Anfängerpraktikums.Kurt Jungcoursematerialhttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1319Fri, 28 Sep 2001 00:00:00 +0200Physikalisches Praktikum für Anfänger Teil B
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1318
Anleitung zu zwölf physikalischen Versuchen im Rahmen des Anfängerpraktikums.Kurt Jungcoursematerialhttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1318Fri, 28 Sep 2001 00:00:00 +0200Physikalisches Praktikum für Chemiker und Biologen
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1320
Anleitung zu zehn physikalischen Versuchen im Rahmen des Praktikums für Chemiker und Biologen.Kurt Jungcoursematerialhttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1320Fri, 28 Sep 2001 00:00:00 +0200Physikalisches Praktikum für Elektrotechnik, Informationstechnik und Technoinformatik
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1321
Anleitung zu zehn physikalischen Versuchen im Rahmen des Praktikums für Studenten der Elektrotechnik, Informationstechnik und Technoinformatik.Kurt Jungcoursematerialhttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1321Fri, 28 Sep 2001 00:00:00 +0200Physikalisches Praktikum für Maschinenbau- und Verfahrenstechnik
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1322
Anleitung zu zehn physikalischen Versuchen im Rahmen des Praktikums für Studenten der Maschinenbau- und Verfahrenstechnik.Kurt Jungcoursematerialhttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1322Fri, 28 Sep 2001 00:00:00 +0200Physikalisches Praktikum für Anfänger Teil A
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1317
Anleitung zu zwölf physikalischen Versuchen im Rahmen des Anfängerpraktikums.Kurt Jungcoursematerialhttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1317Thu, 27 Sep 2001 00:00:00 +0200Random Matrix Theory, Chiral Perturbation Theory, and Lattice Data
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1310
Abstract: Recently, the chiral logarithms predicted by quenched chiral perturbation theory have been extracted from lattice calculations of hadron masses. We argue that the deviations of lattice results from random matrix theory starting around the so-called Thouless energy can be understood in terms of chiral perturbation theory as well. Comparison of lattice data with chiral perturbation theory formulae allows us to compute the pion decay constant. We present results from a calculation for quenched SU(2) with Kogut-Susskind fermions at ß = 2.0 and 2.2.M. E. Berbenni-Bitsch; M. Göckeler; H. Hehl; S. Meyer; P.E.L. Rakow; A. Schäfer; T. Wettigpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1310Tue, 03 Jul 2001 00:00:00 +0200Random Matrix Theory and Chiral Logarithms
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1311
Abstract: Recently, the contributions of chiral logarithms predicted by quenched chiral perturbation theory have been extracted from lattice calculations of hadron masses. We argue that a detailed comparison of random matrix theory and lattice calculations allows for a precise determination of such corrections. We estimate the relative size of the m log(m), m, and m^2 corrections to the chiral condensate for quenched SU(2).M. E. Berbenni-Bitsch; M. Göckeler; H. Hehl; S. Meyer; P.E.L. Rakow; A. Schäfer; T. Wettigpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1311Tue, 03 Jul 2001 00:00:00 +0200Equivalent of a Thouless energy in lattice QCD Dirac spectra
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1308
Abstract: Random matrix theory (RMT) is a powerful statistical tool to model spectral fluctuations. In addition, RMT provides efficient means to separate different scales in spectra. Recently RMT has found application in quantum chromodynamics (QCD). In mesoscopic physics, the Thouless energy sets the universal scale for which RMT applies. We try to identify the equivalent of a Thouless energy in complete spectra of the QCD Dirac operator with staggered fermions and SU_(2) lattice gauge fields. Comparing lattice data with RMT predictions we find deviations which allow us to give an estimate for this scale.M.E. Berbenni; T. Guhr; J.-Z. Ma; S. Meyer; T. Wilkepreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1308Tue, 03 Jul 2001 00:00:00 +0200Beyond the Thouless energy
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1309
Abstract: The distribution and the correlations of the small eigenvalues of the Dirac operator are described by random matrix theory (RMT) up to the Thouless energy E_= 1 / sqrt (V), where V is the physical volume. For somewhat larger energies, the same quantities can be described by chiral perturbation theory (chPT). For most quantities there is an intermediate energy regime, roughly 1/V < E < 1/sqrt (V), where the results of RMT and chPT agree with each other. We test these predictions by constructing the connected and disconnected scalar susceptibilities from Dirac spectra obtained in quenched SU(2) and SU(3) simulations with staggered fermions for a variety of lattice sizes and coupling constants. In deriving the predictions of chPT, it is important totake into account only those symmetries which are exactly realized on the lattice.M. E. Berbenni-Bitsch; M. Göckeler; H. Hehl; S. Meyer; P.E.L. Rakow; A. Schäfer; T. Wettigpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1309Tue, 03 Jul 2001 00:00:00 +0200Enhancement of Magneto-Optic Effects via Large Atomic Coherence
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1297
Abstract: We utilize the generation of large atomic coherence to enhance the resonant nonlinear magneto-optic effect by several orders of magnitude, thereby eliminating power broadening and improving the fundamental signal-to-noise ratio. A proof-of-principle experiment is carried out in a dense vapor of Rb atoms. Detailed numerical calculations are in good agreement with the experimental results. Applications such as optical magnetometry or the search for violations of parity and time reversal symmetry are feasible.V. A. Sautenkov; M. D. Lukin; C. J. Bednar; G. R. Welch; M. Fleischhauer; V. L. Velichansky; M. O. Scullypreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1297Mon, 02 Jul 2001 00:00:00 +0200Entanglement of Atomic Ensembles by Trapping Correlated Photon States
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1293
Abstract: We describe a general technique that allows for an ideal transfer of quantum correlations between light fields and metastable states of matter. The technique is based on trapping quantum states of photons in coherently driven atomic media, in which the group velocity is adiabatically reduced to zero. We discuss possible applications such as quantum state memories, generation of squeezed atomic states, preparation of entangled atomic ensembles and quantum information processing.M. D. Lukin; S. F. Yelin; M. Fleischhauerpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1293Mon, 02 Jul 2001 00:00:00 +0200How to Trap Photons? Storing Single-Photon Quantum States in Collective Atomic Excitations
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1294
Abstract: We show that it is possible to "store" quantum states of single-photon fields by mapping them onto collective meta-stable states of an optically dense, coherently driven medium inside an optical resonator. An adiabatic technique is suggested which allows to transfer non-classical correlations from traveling-wave single-photon wave-packets into atomic states and vise versa with nearly 100% efficiency. In contrast to previous approaches involving single atoms, the present technique does not require the strong coupling regime corresponding to high-Q micro-cavities. Instead, intracavity Electromagnetically Induced Transparency is used to achieve a strong coupling between the cavity mode and the atoms.M. Fleischhauer; S.F. Yelin; M. D. Lukinpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1294Mon, 02 Jul 2001 00:00:00 +0200Mirrorless oscillation based on resonantly enhanced 4-wave mixing: All-order analytic solutions
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1295
Abstract: The phase transition to mirrorless oscillation in resonantly enhanced four-wave mixing in double-A systems are studied analytically for the ideal case of infinite lifetimes of ground-state coherences. The stationary susceptibilities are obtained in all orders of the generated fields and analytic solutions of the coupled nonlinear differential equations for the field amplitudes are derived and discussed.M. Fleischhauerpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1295Mon, 02 Jul 2001 00:00:00 +0200Spontaneous emission and level shifts in absorbing disordered dielectrics and dense atomic gases: A Green's function approach
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1298
Abstract: Spontaneous emission and Lamb shift of atoms in absorbing dielectrics are discussed. A Green's-function approach is used based on the multipolar interaction Hamiltonian of a collection of atomic dipoles with the quantised radiation field. The rate of decay and level shifts are determined by the retarded Green's-function of the interacting electric displacement field, which is calculated from a Dyson equation describing multiple scattering. The positions of the atomic dipoles forming the dielectrics are assumed to be uncorrelated and a continuum approximation is used. The associated unphysical interactions between different atoms at the same location is eliminated by removing the point-interaction term from the free-space Green's-function (local field correction). For the case of an atom in a purely dispersive medium the spontaneous emission rate is altered by the well-known Lorentz local-field factor. In the presence of absorption a result different from previously suggested expressions is found and nearest-neighbour interactions are shown to be important.Michael Fleischhauerpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1298Mon, 02 Jul 2001 00:00:00 +0200Diagram expansions in classical stochastic field theory. I. Regularisations, stochastic calculus and causal Wick's theorem
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1216
Abstract: We aim to establish a link between path-integral formulations of quantum and classical field theories via diagram expansions. This link should result in an independent constructive characterisation of the measure in Feynman path integrals in terms of a stochastic differential equation (SDE) and also in the possibility of applying methods of quantum field theory to classical stochastic problems. As a first step we derive in the present paper a formal solution to an arbitrary c-number SDE in a form which coincides with that of Wick's theorem for interacting bosonic quantum fields. We show that the choice of stochastic calculus in the SDE may be regarded as a result of regularisation, which in turn removes ultraviolet divergences from the corresponding diagram series.L.I. Plimak; M. Fleischhauer; M.J. Collettpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1216Tue, 15 May 2001 00:00:00 +0200Diagram expansions in classical stochastic field theory / Diagram series and stochastic differential equations
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1217
We show that the solution to an arbitrary c-number stochastic differential equation (SDE) can be represented as a diagram series. Both the diagram rules and the properties of the graphical elements reflect causality properties of the SDE and this series is therefore called a causal diagram series. We also discuss the converse problem, i.e. how to construct an SDE of which a formal solution is a given causal diagram series. This then allows for a nonperturbative summation of the diagram series by solving this SDE, numerically or analytically.L.I. Plimak; M. Fleischhauer; M. J. Collettpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1217Tue, 15 May 2001 00:00:00 +0200Measuring a coherent superposition
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1212
Abstract: We propose a simple method for measuring the populations and the relative phase in a coherent superposition of two atomic states. The method is based on coupling the two states to a third common (excited) state by means of two laser pulses, and measuring the total fluorescence from the third state for several choices of the excitation pulses.K. Bergmann; N.V. Vitanov; B.W. Shore; R.G. Unanyanpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1212Wed, 09 May 2001 00:00:00 +0200Photoionization Suppression by Continuum Coherence: Experiment and Theory
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1213
Abstract: We present experimental and theoretical results of a detailed study of laser-induced continuum structures (LICS) in the photoionization continuum of helium out of the metastable state 2s^1 S_0. The continuum dressing with a 1064 nm laser, couples the same region of the continuum to the 4s^1 S_0 state. The experimental data, presented for a range of intensities, show pronounced ionization suppression (by asmuch as 70% with respect to the far-from-resonance value) as well as enhancement, in a Beutler-Fano resonance profile. This ionization suppression is a clear indication of population trapping mediated by coupling to a contiuum. We present experimental results demonstrating the effect of pulse delay upon the LICS, and for the behavior of LICS for both weak and strong probe pulses. Simulations based upon numerical solution of the Schrödinger equation model the experimental results. The atomic parameters (Rabi frequencies and Stark shifts) are calculated using a simple model-potential method for the computation of the needed wavefunctions. The simulations of the LICS profiles are in excellent agreement with experiment. We also present an analytic formulation of pulsed LICS. We show that in the case of a probe pulse shorter than the dressing one the LICS profile is the convolution of the power spectra of the probe pulse with the usual Fano profile of stationary LICS. We discuss some consequences of deviation from steady-state theory.L.P. Yatsenko; T. Halfmann; B.W. Shore; K. Bergmannpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1213Wed, 09 May 2001 00:00:00 +0200Coherent properties of a tripod system coupled via a continuum
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1194
We present results from a study of the coherence properties of a system involving three discrete states coupled to each other by two-photon processes via a common continuum. This tripod linkage is an extension of the standard laser-induced continuum structure (LICS) which involves two discrete states and two lasers. We show that in the tripod scheme, there exist two population trapping conditions; in some cases these conditions are easier to satisfy than the single trapping condition in two-state LICS. Depending on the pulse timing, various effects can be observed. We derive some basic properties of the tripod scheme, such as the solution for coincident pulses, the behaviour of the system in the adiabatic limit for delayed pulses, the conditions for no ionization and for maximal ionization, and the optimal conditions for population transfer between the discrete states via the continuum. In the case when one of the discrete states is strongly coupled to the continuum, the population dynamics reduces to a standard two-state LICS problem (involving the other two states) with modified parameters; this provides the opportunity to customize the parameters of a given two-state LICS system.K. Bergmann; R. G. Unanyan; N.V. Vitanov; B. W. Shorepreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1194Fri, 27 Apr 2001 00:00:00 +0200Renormalization Proof for Spontaneously broken Yang-Mills Theory with Flow Equations
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1195
Abstract: In this paper we present a renormalizability proof for spontaneously broken SU (2) gauge theory. It is based on Flow Equations, i.e. on the Wilson renormalization group adapted to perturbation theory. The power counting part of the proof, which is conceptually and technically simple, follows the same lines as that for any other renormalizable theory. The main difficulty stems from the fact that the regularization violates gauge invariance. We prove that there exists a class of renormalization conditions such that the renormalized Green functions satisfy the Slavnov-Taylor identities of SU (2) Yang-Mills theory on which the gauge invariance of the renormalized theory is based.Volkhard F. Müller; Christoph Kopperpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1195Thu, 19 Apr 2001 00:00:00 +0200Correlation between structure and magnetic anisotropies of Co on Cu(110)
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/884
Magnetic anisotropies of MBE-grown fcc Co(110)-films on Cu(110) single crystal substrates have been determined by using Brillouin light scattering(BLS) and have been correlated with the structural properties determined by low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). Three regimes of film growth and associated anisotropy behavior are identified: coherent growth in the Co film thickness regime of up to 13 Å, in-plane anisotropic strain relaxation between 13 Å and about 50 Å and inplane isotropic strain relaxation above 50 Å. The structural origin of the transition between anisotropic and isotropic strain relaxation was studied using STM. In the regime of anisotropic strain relaxation long Co stripes with a preferential [ 110 ]-orientation are observed, which in the isotropic strain relaxation regime are interrupted in the perpendicular in-plane direction to form isotropic islands. In the Co film thickness regime below 50 Å an unexpected suppression of the magnetocrystalline anisotropy contribution is observed. A model calculation based on a crystal field formalism and discussed within the context of band theory, which explicitly takes tetragonal misfit strains into account, reproduces the experimentally observed anomalies despite the fact that the thick Co films are quite rough.Jürgen Fassbender; Christoph Mathieu; Burkard Hillebrands; G. Güntherodt; R. Jungblut; J. Kohlhepp; M.T. Johnson; D.J. Roberts; G.A. Gehringpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/884Fri, 02 Mar 2001 00:00:00 +0100Mode beating of spin wave beams in ferrimagnetic Lu2.04Bi0.96Fe5O12 films
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/878
Absract: We report on measurements of the two-dimensional intensity distribtion of linear and non-linear spin wave excitations in a LuBiFeO film. The spin wave intensity was detected with a high-resolution Brillouinlight scatteringspectroscopy setup. The observed snake-like structure of the spin wave intensity distribution is understood as a mode beating between modes with different lateral spin wave intensity distributions. The theoretical treatment of the linear regime is performed analytically, whereas the propagation of non-linear spin waves is simulated by a numerical solution of a non-linear Schrödinger equation with suitable boundary conditions.Oliver Büttner; Martin Bauer; Christoph Mathieu; Serguei Demokritov; Burkard Hillebrands; P.A. Kolodin; M.P. Kostylev; S. Sure; H. Dötsch; V. Grimalsky; Yu. Rapoport; A.N. Slavinpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/878Fri, 02 Mar 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 +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 +0100