2,355 research outputs found
Quantum-classical transition in the Caldeira-Leggett model
The quantum-classical transition in the Caldeira-Leggett model is
investigated in the framework of the functional renormalization group method.
It is shown that a divergent quadratic term arises in the action due to the
heat bath in the model. By removing the divergence with a frequency cutoff we
considered the critical behavior of the model. The critical exponents belonging
to the susceptibility and the correlation length are determined and their
independence of the frequency cutoff and the renormalization scheme is shown.Comment: 8 pages, 4 figure
Magnetic phase diagram of the Kondo lattice model with quantum localized spins
The magnetic phase diagram of the ferromagnetic Kondo lattice model is
determined at T=0 in 1D, 2D, and 3D for various magnitudes of the quantum
mechanical localized spins ranging from S=1/2 to classical spins. We consider
the ferromagnetic phase, the paramagnetic phase, and the
ferromagnetic/antiferromagnetic phase separated regime. There is no significant
influence of the spin quantum number on the phase boundaries except for the
case S=1/2, where the model exhibits an instability of the ferromagnetic phase
with respect to spin disorder. Our results give support, at least as far as the
low temperature magnetic properties are concerned, to the classical treatment
of the S=3/2-spins in the intensively investigated manganites, for which the
ferromagnetic Kondo-lattice model is generally employed to account for
magnetism.Comment: 8 pages, 6 figure
Computer-aided Melody Note Transcription Using the Tony Software: Accuracy and Efficiency
accepteddate-added: 2015-05-24 19:18:46 +0000 date-modified: 2017-12-28 10:36:36 +0000 keywords: Tony, melody, note, transcription, open source software bdsk-url-1: https://code.soundsoftware.ac.uk/attachments/download/1423/tony-paper_preprint.pdfdate-added: 2015-05-24 19:18:46 +0000 date-modified: 2017-12-28 10:36:36 +0000 keywords: Tony, melody, note, transcription, open source software bdsk-url-1: https://code.soundsoftware.ac.uk/attachments/download/1423/tony-paper_preprint.pdfWe present Tony, a software tool for the interactive an- notation of melodies from monophonic audio recordings, and evaluate its usability and the accuracy of its note extraction method. The scientific study of acoustic performances of melodies, whether sung or played, requires the accurate transcription of notes and pitches. To achieve the desired transcription accuracy for a particular application, researchers manually correct results obtained by automatic methods. Tony is an interactive tool directly aimed at making this correction task efficient. It provides (a) state-of-the art algorithms for pitch and note estimation, (b) visual and auditory feedback for easy error-spotting, (c) an intelligent graphical user interface through which the user can rapidly correct estimation errors, (d) extensive export functions enabling further processing in other applications. We show that Tonyâs built in automatic note transcription method compares favourably with existing tools. We report how long it takes to annotate recordings on a set of 96 solo vocal recordings and study the effect of piece, the number of edits made and the annotatorâs increasing mastery of the software. Tony is Open Source software, with source code and compiled binaries for Windows, Mac OS X and Linux available from https://code.soundsoftware.ac.uk/projects/tony/
Potential-energy (BCS) to kinetic-energy (BEC)-driven pairing in the attractive Hubbard model
The BCS-BEC crossover within the two-dimensional attractive Hubbard model is
studied by using the Cellular Dynamical Mean-Field Theory both in the normal
and superconducting ground states. Short-range spatial correlations
incorporated in this theory remove the normal-state quasiparticle peak and the
first-order transition found in the Dynamical Mean-Field Theory, rendering the
normal state crossover smooth. For smaller than the bandwidth, pairing is
driven by the potential energy, while in the opposite case it is driven by the
kinetic energy, resembling a recent optical conductivity experiment in
cuprates. Phase coherence leads to the appearance of a collective Bogoliubov
mode in the density-density correlation function and to the sharpening of the
spectral function.Comment: 5 pages, 4 figure
Morphologies of three-dimensional shear bands in granular media
We present numerical results on spontaneous symmetry breaking strain
localization in axisymmetric triaxial shear tests of granular materials. We
simulated shear band formation using three-dimensional Distinct Element Method
with spherical particles. We demonstrate that the local shear intensity, the
angular velocity of the grains, the coordination number, and the local void
ratio are correlated and any of them can be used to identify shear bands,
however the latter two are less sensitive. The calculated shear band
morphologies are in good agreement with those found experimentally. We show
that boundary conditions play an important role. We discuss the formation
mechanism of shear bands in the light of our observations and compare the
results with experiments. At large strains, with enforced symmetry, we found
strain hardening.Comment: 6 pages 5 figures, low resolution figures
New measure of electron correlation
We propose to quantify the "correlation" inherent in a many-electron (or
many-fermion) wavefunction by comparing it to the unique uncorrelated state
that has the same single-particle density operator as it does.Comment: Final version to appear in PR
Asymmetry between the electron- and hole-doped Mott transition in the periodic Anderson model
We study the doping driven Mott metal-insulator transition (MIT) in the
periodic Anderson model set in the Mott-Hubbard regime. A striking asymmetry
for electron or hole driven transitions is found. The electron doped MIT at
larger U is similar to the one found in the single band Hubbard model, with a
first order character due to coexistence of solutions. The hole doped MIT, in
contrast, is second order and can be described as the delocalization of
Zhang-Rice singlets.Comment: 18 pages, 19 figure
- âŠ