115,105 research outputs found
Synchronization of Chaotic Maps by Symmetric Common Noise
Synchronization of identical chaotic systems subjected to common noise has
been the subject of recent research. Studies on several chaotic systems have
shown that, the synchronization is actually induced by the non-zero mean of the
noise, and symmetric noise with zero-mean cannot lead to synchronization. Here
it is presented that synchronization can be achieved by {\sl zero-mean} noise
in some chaotic maps with large convergence regions.Comment: 5 pages, 4 figure
Dynamics of a hole in the large--U Hubbard model: a Feynman diagram approach
We study the dynamics of a single hole in an otherwise half--filled
two--dimensional Hubbard model by introducing a nonlocal Bogolyubov
transformation in the antiferromagnetic state. This allows us to rewrite the
Hamiltonian in a form that makes a separation between high--energy processes
(involving double--occupancy) and low--energy physics possible. A diagrammatic
scheme is developped that allows for a systematic study of the different
processes delocalizing a carrier in the antiferromagnetic state. In particular,
the so--called Trugman process, important if transverse spin fluctuations are
neglected, is studied and is shown to be dominated by the leading vertex
corrections. We analyze the dynamics of a single hole both in the Ising limit
and with spin fluctuations. The results are compared with previous theories as
well as with recent exact small--cluster calculations, and we find good
agreement. The formalism establishes a link between weak and strong coupling
methodologies.Comment: Latex 34pages, Orsay Preprint, submitted to Phys. Rev.
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