903 research outputs found
Dual Methods for Lattice Field Theories at Finite Density
We present a dual representation of the partition function of the charged
scalar field in which the complex action problem at non-zero chemical potential
is absent. In this dual representation Monte Carlo simulations are possible and
we show some physical results obtained with this approach. Furthermore we
present a technique to study 2-point functions at finite density. Results for
the lattice correlators at various chemical potentials are shown and discussed.Comment: 7 pages, 2 figures, presented at the 31st International Symposium on
Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, German
Solving the sign problems of the massless lattice Schwinger model with a dual formulation
We derive an exact representation of the massless Schwinger model on the
lattice in terms of dual variables which are configurations of loops, dimers
and plaquette occupation numbers. When expressed with the dual variables the
partition sum has only real and positive terms also when a chemical potential
or a topological term are added -- situations where the conventional
representation has a complex action problem. The dual representation allows for
Monte Carlo simulations without restrictions on the values of the chemical
potential or the vacuum angle.Comment: Several comments added. Final version to appear in Nuclear Physics
Update Delay: A new Information-Centric Metric for a Combined Communication and Application Level Reliability Evaluation of CAM based Safety Applications
Standard network metrics, such as throughput, latency and reception probability, are the most popular performance indicators used in the literature to describe and compare communication protocol variations. However, these âtraditionalâ network-centric PI are not adapted to the distributed, information-centric nature of the beaconing communication pattern, nor do they cover application level reliability or freshness of information.
In this paper, we introduce a more suitable metric called Update Delay, represented as a Complementary Cumulative Distribution Function (CCDF). We will show how this single Update Delay performance indicator can be an optimal representation of the freshness and reliability of the information about a certain transmitter, i.e. awareness about vehicles and their current state in the vicinity. This paper extends on the methodological aspects of the approach, as well as introduces several concrete examples
Performance of CAM based Safety Applications using ITS-G5A MAC in High Dense Scenarios
ETSI ITS-G5 is the current vehicle-to-vehicle communication technology in Europe, which will be standardized by ETSI TC ITS. It is based on IEEE 802.11p and therefore uses a CSMA/CA scheme for Media Access Control (MAC). In this paper we analyze the performance of CAM based safety applications using the ETSI ITS-G5 MAC technology in a challenging scenario with respect to MAC issues: A suitable freeway segment with 6 lanes in each direction. The freeway scenario is thoroughly modeled and implemented in the well known ns-3 simulation environment.
Based on this model, the paper shows the performance of CAM based safety applications under MAC challenging conditions. Therefore we provide a set of simulation results resting upon a particular performance metric which incorporates the key requirements of safety applications. Finally we analyze two concrete example scenarios to make a point how reliable CAM based safety applications are in high dense traffic scenarios
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