4,721 research outputs found
Investigation of metal-insulator like transition through the ab initio density matrix renormalization group approach
We have studied the Metal-Insulator like Transition (MIT) in lithium and
beryllium ring-shaped clusters through ab initio Density Matrix Renormalization
Group (DMRG) method. Performing accurate calculations for different interatomic
distances and using Quantum Information Theory (QIT) we investigated the
changes occurring in the wavefunction between a metallic-like state and an
insulating state built from free atoms. We also discuss entanglement and
relevant excitations among the molecular orbitals in the Li and Be rings and
show that the transition bond length can be detected using orbital entropy
functions. Also, the effect of different orbital basis on the effectiveness of
the DMRG procedure is analyzed comparing the convergence behavior.Comment: 12 pages, 14 figure
Inelastic diffractive scattering in nonperturbative QCD
We examine diffractive proton-proton scattering p p -> p X and photo- and
electroproduction of \rho^0 mesons \gamma^(*) p -> \rho^0 X, where X denotes a
proton or a final state, into which the proton can go by diffractive
dissociation. Using a functional integral approach we derive the scattering
amplitudes, which are governed by the expectation values of light-like
Wegner-Wilson loops, which are then evaluated using the model of the stochastic
vacuum. For the proton, we assume a quark-diquark structure. From the
scattering amplitudes we calculate total and differential cross sections for
high centre of mass energy and small momentum transfer and compare with
experiments. Furthermore we calculate isovector form factors for the proton and
the pion within the same model.Comment: 32 pages, 11 figures, v3: revised chapter 5, added appendix B, to be
published in Eur.Phys.J.
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