The Knapsack Problem with Neighbour Constraints

We study a constrained version of the knapsack problem in which dependencies between items are given by the adjacencies of a graph. In the 1-neighbour knapsack problem, an item can be selected only if at least one of its neighbours is also selected. In the all-neighbours knapsack problem, an item can be selected only if all its neighbours are also selected. We give approximation algorithms and hardness results when the nodes have both uniform and arbitrary weight and profit functions, and when the dependency graph is directed and undirected.Comment: Full version of IWOCA 2011 pape

Housing, housing finance, and monetary policy: an introduction to the Bank's 2007 Economic Symposium

Housing ; Housing - Prices ; Business cycles ; Monetary policy ; Consumer behavior

Unresolved Legacies: Aboriginal Food Production Landscapes, Ecosystem Recovery Strategies & Land Use Planning for Conservation of the Garry Oak Ecosystems in South-Western British Columbia

In Canada, aboriginal legacies in landscapes and their implications for land use planning for biodiversity conservation remain poorly acknowledged. Similarly, inter-cultural conversations on values about and priorities for biological resources and habitat protection remain under-developed. This essay begins with a rhetorical question. Will it be possible to forge successful ecosystem recovery strategies, to maintain all elements of local biological diversity through land use planning, without far deeper cognizance of the aboriginal legacies in Canadian landscapes? I do not think so. This discussion, from the drier enclaves on the south coast of British Columbia, centres on a federally funded ecosystem recovery team in the first four years of its operation from 1999 to 2003 and the near total lack of outreach to, and engagement with, aboriginal people and First Nations. These were the same years as the final phase of development of Canada’s relatively weak Species At Risk Act (SARA).2

Lost Landscapes and the Spatial Contextualization of Queerness

Lesbian, gay, and bisexual1 habitation of outdoor and indoor environments has become a major topic in queer2 theory and spatial issues3 have come to represent new frontiers in the politics of our various communities. Homophobia, violence, and isolation in outdoor spaces arc coming to be framed as environmental problems. A host of possibilities for new alliances around queer space is emerging. But it is first necessary to ask a number of questions before specific interventions in the condition of outdoor areas can better define and strengthen our communities and improve our lives

Categorisation and Detection of Dark Matter Candidates from String/M-theory Hidden Sectors

We study well-motivated dark matter candidates arising from weakly-coupled hidden sectors in compactified string/$M$-theory. Imposing generic top-down constraints greatly restricts allowed candidates. By considering the possible mechanisms for achieving the correct dark matter relic density, we compile categories of viable dark matter candidates and annihilation mediators. We consider the case where supersymmetry breaking occurs via moduli stabilisation and is gravitationally mediated to the visible and other hidden sectors, without assuming sequestering of the sector in which supersymmetry is broken. We find that in this case, weakly-coupled hidden sectors only allow for fermionic dark matter. Additionally, most of the mechanisms for obtaining the full relic density only allow for a gauge boson mediator, such as a dark $Z'$. Given these considerations, we study the potential for discovering or constraining the allowed parameter space given current and future direct detection experiments, and direct production at the LHC. We also present a model of a hidden sector which would contain a satisfactory dark matter candidate.Comment: 29 pages, 10 figure