1,089 research outputs found
Two algorithms for the student-project allocation problem
We study the Student-Project Allocation problem (SPA), a generalisation of the classical Hospitals / Residents problem (HR). An instance of SPA involves a set of students, projects and lecturers. Each project is offered by a unique lecturer, and both projects and lecturers have capacity constraints. Students have preferences over projects, whilst lecturers have preferences over students. We present two optimal linear-time algorithms for allocating students to projects, subject to the preference and capacity constraints. In particular, each algorithm finds a stable matching of students to projects. Here, the concept of stability generalises the stability definition in the HR context. The stable matching produced by the first algorithm is simultaneously best-possible for all students, whilst the one produced by the second algorithm is simultaneously best-possible for all lecturers. We also prove some structural results concerning the set of stable matchings in a given instance of SPA. The SPA problem model that we consider is very general and has applications to a range of different contexts besides student-project allocation
Review of Recent Developments in the Random-Field Ising Model
A lot of progress has been made recently in our understanding of the
random-field Ising model thanks to large-scale numerical simulations. In
particular, it has been shown that, contrary to previous statements: the
critical exponents for different probability distributions of the random fields
and for diluted antiferromagnets in a field are the same. Therefore, critical
universality, which is a perturbative renormalization-group prediction, holds
beyond the validity regime of perturbation theory. Most notably, dimensional
reduction is restored at five dimensions, i.e., the exponents of the
random-field Ising model at five dimensions and those of the pure Ising
ferromagnet at three dimensions are the same.Comment: 11 pages, 4 figures, updated and extended version, to be published in
J. Stat. Phy
Ultra-high Energy Cosmic Rays: a probe into New Physics
The most energetic particles ever detected exceed eV in energy.
Their existence represents at the same time a great challenge for particle
physics and astrophysics, and a great promise of providing us for a probe of
the validity of the laws of Nature in extreme conditions. We review here the
most recent data and the future perspectives for detection of cosmic rays at
ultra-high energies, and discuss possible ways of using these data to test the
possibility that new Physics and/or new Astrophsyics may be awaiting around the
corner.Comment: Invited Review Talk at SpacePart 2002, La Biodola, Isola d'Elba,
Italy - May 14-19, 200
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