190,183 research outputs found
Light Front Approach for Strong and Weak Decays of Pentaquarks
Strong and weak decays of pentaquarks are studied in the framework of the
light-front approach.Comment: 3 pages, talk given at the 2004 DPF Meeting, Riverside, CA. Aug
26-31, 200
Effective models for gapped phases of strongly correlated quantum lattice models
We present a robust scheme to derive effective models non-perturbatively for
quantum lattice models when at least one degree of freedom is gapped. A
combination of graph theory and the method of continuous unitary
transformations (gCUTs) is shown to efficiently capture all zero-temperature
fluctuations in a controlled spatial range. The gCUT can be used either for
effective quasi-particle descriptions or for effective low-energy descriptions
in case of infinitely degenerate subspaces. We illustrate the method for 1d and
2d lattice models yielding convincing results in the thermodynamic limit. We
find that the recently discovered spin liquid in the Hubbard model on the
honeycomb lattice lies outside the perturbative strong-coupling regime. Various
extensions and perspectives of the gCUT are discussed.Comment: 6 pages, 5 figures, extended discussion on J2/J1 for the honeycomb
Hubbard model and on the properties of different generators for the
continuous unitary transformatio
Characterisation of real GPRS traffic with analytical tools
With GPRS and UMTS networks lunched, wireless multimedia services are commercially becoming the most attractive applications next to voice. Because of the nature of bursty, packet-switched schemes and multiple data rates, the traditional Erlang approach and Poisson models for characterising voice-centric services traffic are not suitable for studying wireless multimedia services traffic. Therefore, research on the characterisation of wireless multimedia services traffic is very challenging. The typical reference for the study of wireless multimedia services traffic is wired Internet services traffic. However, because of the differences in network protocol, bandwidth, and QoS requirements between wired and wireless services, their traffic characterisations may not be similar. Wired network Internet traffic shows self-similarity, long-range dependence and its file sizes exhibit heavy-tailedness. This paper reports the use of existing tools to analyse real GPRS traffic data to establish whether wireless multimedia services traffic have similar properties as wired Internet services traffic
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