Nonequilibrium superoperator GW equations

Hedin's equations [Phys. Rev. 139, 796 (1965)] for the one-particle equilibrium Green's function of a many-electron system are generalized to nonequilibrium open systems using two fields that separately control the evolution of the bra and the ket of the density matrix. A closed hierarchy is derived for the Green's function, the self-energy, the screened potential, the polarization, and the vertex function, all expressed as Keldysh matrices in Liouville space.     

Simulation of single molecule inelastic electron tunneling signals in paraphenylene-vinylene oligomers and distyrylbenzene[2.2]paracyclophanes

Inelastic resonances in the electron tunneling spectra of several conjugated molecules are simulated using the nonequilibrium Greens function formalism. The vibrational modes that strongly couple to the electronic current are different from the infrared and Raman active modes. Spatially resolved inelastic electron tunneling (IET) intensities are predicted. The simulated IET intensities for a large distyrylbenzene paracyclophane molecule are in qualitative agreement with recent experimental results.     

Simulation of x-ray absorption near edge spectra of electronically excited ruthenium tris-2,2'-bipyridine

The L(3) edge x-ray absorption near edge spectrum (XANES) of the ground electronic state and the metal to ligand charge transfer state of ruthenium tris-2,2(')-bipyridine is calculated. The final valence states and energies in the presence of the photoelectron and core hole, and the corresponding transition intensities are computed using time dependent density functional theory with the Becke three-parameter density functional with the Lee-Yang-Parr correlation functional. Calculations show a valence shift of the primary XANES peak and the appearance of the new XANES transition to the hole created by the optical excitation, in agreement with experiment [M. Saes, C. Bressler, R. Abela, D. Grolimund, S. L. Johnson, P. A. Heimann, and M. Chergui, Phys. Rev. Lett. 90, 047403 (2003)].     

Exciton annihilation on dendrimeric trees

Exciton-exciton annihilation on Cayley tree like dendrimer molecules are investigated via Monte Carlo simulations. Annihilation reaction of the type A+A→0 is considered to calculate the exciton density decay for multiexciton diffusion on dendrimers. Exciton density decays as a power law with a continuously varying exponent in a linear potential. For the case of realistic nonlinear potential of phenylacetylene dendrimers (Phys. Rev. Lett. 77 (1998) 4656) the excitons accumulate around the free energy minimum and annihilate each other quickly.     

Probing anomalous relaxation by coherent multidimensional optical spectroscopy

We propose to study the origin of algebraic decay of two-point correlation functions observed in glasses, proteins, and quantum dots by their nonlinear response to sequences of ultrafast laser pulses. Power-law spectral singularities and temporal relaxation in two-dimensional correlation spectroscopy signals are predicted for a continuous time random walk model of stochastic spectral jumps in a two-level system with a power-law distribution of waiting times psi(t) approximately t;{-alpha-1}. Spectroscopic signatures of stationary ensembles for 1相似文献   

Modelling one-dimensional driven diffusive systems by the Zero-Range Process

In order to characterize networks in the scale-free network class we study the frequency of cycles of length h that indicate the ordering of network structure and the multiplicity of paths connecting two nodes. In particular we focus on the scaling of the number of cycles with the system size in off-equilibrium scale-free networks. We observe that each off-equilibrium network model is characterized by a particular scaling in general not equal to the scaling found in equilibrium scale-free networks. We claim that this anomalous scaling can occur in real systems and we report the case of the Internet at the Autonomous System Level.Received: 15 January 2004, Published online: 14 May 2004PACS: 89.75.-k Complex systems - 89.75.Hc Networks and genealogical trees     

Anomalous lineshapes and aging effects in two-dimensional correlation spectroscopy

Multitime correlation functions provide useful probes for the ensembles of trajectories underlying the stochastic dynamics of complex systems. These can be obtained by measuring their optical response to sequences of ultrashort optical pulse. Using the continuous time random walk model for spectral diffusion, we analyze the signatures of anomalous relaxation in two-dimensional four wave mixing signals. Different models which share the same two point joint probability distribution show markedly different lineshapes and may be distinguished. Aging random walks corresponding to waiting time distributions with diverging first moment show dependence of 2D lineshapes on initial observation time, which persist for long times.     

Dynamics of simple computer networks

We consider a simple two-dimensional layered automaton. Each processor in the automaton performs the same nonlinear, thresholdlike operation (so that the row-to-row evolution of the array can also be seen as the time development of a one-dimensional automaton). One row of the machine is reserved for input, another is singled out as output. We study the output space in detail, as restricted by the very wiring of the array, enumerating the output configurations, and characterizing them statistically. We demonstrate that input configurations flow to a set of zero measure in output space. The variations in output that are to be expected when input is subjected to perturbations are also examined.