5 research outputs found
ATTac-2000: An Adaptive Autonomous Bidding Agent
The First Trading Agent Competition (TAC) was held from June 22nd to July
8th, 2000. TAC was designed to create a benchmark problem in the complex domain
of e-marketplaces and to motivate researchers to apply unique approaches to a
common task. This article describes ATTac-2000, the first-place finisher in
TAC. ATTac-2000 uses a principled bidding strategy that includes several
elements of adaptivity. In addition to the success at the competition, isolated
empirical results are presented indicating the robustness and effectiveness of
ATTac-2000's adaptive strategy
Next nearest neighbour Ising models on random graphs
This paper develops results for the next nearest neighbour Ising model on
random graphs. Besides being an essential ingredient in classic models for
frustrated systems, second neighbour interactions interactions arise naturally
in several applications such as the colour diversity problem and graphical
games. We demonstrate ensembles of random graphs, including regular
connectivity graphs, that have a periodic variation of free energy, with either
the ratio of nearest to next nearest couplings, or the mean number of nearest
neighbours. When the coupling ratio is integer paramagnetic phases can be found
at zero temperature. This is shown to be related to the locked or unlocked
nature of the interactions. For anti-ferromagnetic couplings, spin glass phases
are demonstrated at low temperature. The interaction structure is formulated as
a factor graph, the solution on a tree is developed. The replica symmetric and
energetic one-step replica symmetry breaking solution is developed using the
cavity method. We calculate within these frameworks the phase diagram and
demonstrate the existence of dynamical transitions at zero temperature for
cases of anti-ferromagnetic coupling on regular and inhomogeneous random
graphs.Comment: 55 pages, 15 figures, version 2 with minor revisions, to be published
J. Stat. Mec