The complexity of controlling candidate-sequential elections

  title={The complexity of controlling candidate-sequential elections},
  author={Edith Hemaspaandra and Lane A. Hemaspaandra and J{\"o}rg Rothe},
  journal={Theor. Comput. Sci.},

Complexity of control by partitioning veto elections and of control by adding candidates to plurality elections

It is observed that a reduction from the literature showing the parameterized complexity of control by adding candidates to plurality elections, parameterized by the number of voters, is technically flawed, and it is shown how this reduction can be adapted to make it correct.

Closing the Gap of Control Complexity in Borda Elections: Solving ten open cases

This work considers the problem of control in elections where an election chair seeks to either make a designated candidate win, or prevent her from winning, via actions such as adding, deleting, or partitioning either candidates or voters, and settles the complexity for ten missing cases in the unique-winner model.

Closing the Gap of Control Complexity in Borda Elections : Solving Twelve Open Cases 1

We consider the problem of control in elections where an election chair seeks to either make a designated candidate win, or prevent her from winning, via actions such as adding, deleting, or

The Complexity of Online Bribery in Sequential Elections

It is shown that even for election systems whose winner-determination problem is polynomial-time computable, an online, sequential setting may vastly increase the complexity of bribery, in fact jumping the problem up to completeness for high levels of thePolynomial hierarchy or even PSPACE.

Election-Attack Complexity for More Natural Models

A model of electoral control in the setting where some of the voters act strategically (i.e., are manipulators) is introduced, and both the case where the agent controlling the election and the manipulators share a goal, and the cases where they have competing goals are considered.

Solving Seven Open Problems of Offline and Online Control in Borda Elections

This work reduces the number of missing cases by pinpointing the complexity of three control scenarios for Borda elections, including some that arguably are among the practically most relevant ones.

Optimal defense against election control by deleting voter groups

Borda Count in Collective Decision Making: A Summary of Recent Results

It is described how Borda can be used to maximize social welfare when indivisible goods are to be allocated to agents with ordinal preferences and the use of Borda in forming coalitions of players in a certain type of hedonic game is illustrated.

Dynamic Proportional Rankings

This work proposes generalizations of well-known aggregation rules to this setting and studies their monotonicity and proportionality properties, and evaluates the performance of these rules experimentally, using realistic probabilistic assumptions on the selection procedure.

Perpetual Voting: Fairness in Long-Term Decision Making

This paper explores the proposed voting rules via an axiomatic analysis as well as a quantitative evaluation by computer simulations and identifies two perpetual voting rules as particularly recommendable in long-term collective decision making.



Controlling Candidate-Sequential Elections

This work provides a natural model for sequential candidate evaluation, a framework for evaluating the computational complexity of controlling the outcome within that framework, and some initial results on the range such complexity can take on.

The complexity of online voter control in sequential elections

A framework that models online voter control in sequential elections and obtains completeness for coNP in the deleting/adding cases with a bounded deletion/addition limit and for NP in the partition cases with an additional restriction is introduced.

The Complexity of Online Manipulation of Sequential Elections

Online Voter Control in Sequential Elections

This work introduces a framework that models online voter control in sequential elections and shows that for plurality, online control by deleting or adding voters is in P, and for partitioning voters is coNP-hard.

How Hard Is It to Control an Election by Breaking Ties?

It can be NP-hard to control an election by breaking ties even with a two-stage voting rule, and it is shown that the form of the tie-breaking function can increase the opportunities for control.

More Natural Models of Electoral Control by Partition

It is the hope that having these new partition types will allow studies of control attacks to include such models that more realistically capture many settings, and for some important cases analyze the complexity of these models.

When are elections with few candidates hard to manipulate?

This article characterize the exact number of candidates for which manipulation becomes hard for the plurality, Borda, STV, Copeland, maximin, veto, plurality with runoff, regular cup, and randomized cup protocols and shows that for simpler manipulation problems, manipulation cannot be hard with few candidates.

Challenges to complexity shields that are supposed to protect elections against manipulation and control: a survey

This work surveys and discusses some recent results on challenges to complexity results for manipulation and control, including typical-case analyses and experiments, fixed-parameter tractability, domain restrictions, and approximability.

Control and Bribery in Voting

This chapter surveys results on the complexity of control and bribery in elections, providing an overview of the specific problems studied, sketching sample proofs, and reviewing some approaches to dealing with the computational hardness of these control and bribes problems.