The Complexity of Manipulating $k$-Approval Elections

An important problem in computational social choice theory is the computability and complexity of undesirable behavior among agents, such as control, manipulation, and bribery in election systems. These kind of voting strategies are often tempting at the individual level but disasterous for the agents as a whole. Creating election systems where the determination of such strategies is difficult is thus an important goal. Previous work in this area has demonstrated the complexity of misuse in cases involving a fixed number of candidates, and of specific election systems on unbounded number of candidates such as Borda. In contrast, we take the first step in generalizing the results of computational complexity of election misuse to cases of infinitely many systems on an unbounded number of candidates. Interesting families of systems include $k$-approval and $k$-veto elections, in which voters distinguish $k$ candidates from the candidate set. We also demonstrate a surprising connection between manipulation in election systems with some graph theory problems.