Seminar: P. Girard/V. Pavlov/M.Wilson 2014-05-20

Speaker: Patrick Girard, Valery Pavlov and Mark Wilson
Affiliation: The University of Auckland
Title: Experimental study of influence in social networks
Date: Tuesday, 20 May 2014
Time: 5:00 pm
Location: OGGB level 0. DECIDE, The UoA Business Decision-Making Lab (formerly Lab 04

We present an overview of work in progress using the DECIDE lab (http://hfbeltran.wix.com/decide), part of a larger project on threshold models of influence. Our pilot study has yielded several interesting hypotheses for future investigation. We welcome audience suggestions for follow-up work.

Slides

Revamp of CMSS

Our centre has been formally reviewed in December 2013, and we have decided to try to grow.

(coming soon)

There will be a new Advisory Board, which is smaller and not solely composed of academic researchers. Expect to see minor changes to this website soon.

Seminar: K. Manson 2014-04-08

Speaker:     Kerry Manson
Affiliation: The University of Auckland
Title:       Power Indices and their Real-World Application
Date:        Tuesday, 8 Apr 2014
Time:        5:00 pm
Location:    Room 412, Science Centre (303)

It has been recognised that standard, a priori power indices do not describe political power
well in many real-world situations. This lowers our ability to usefully incorporate the effects of
power distribution into political analyses. Methods of a posteriori power measurement which
take into account restrictions on the set of allowable coalitions are examined and developed. A
Hasse diagram representation of games is used to give a new method for adapting any a priori
Banzhaf index to a restricted coalition structure. A modified Banzhaf index is further analysed, and the
conditions for manipulation of this index by players are given.

The talk is based on Kerry’s Honours dissertation written in 2013.

Seminar: S. Ozernikov 2014-03-25

Speaker:     Sergey Ozernikov
Affiliation: The University of Auckland
Title:       Public-Key Infrastructure: trust metrics in the Web of Trust
Date:        Tuesday, 25 Mar 2014
Time:        5:00 pm
Location:    Room 412, Science Centre (303)

Public Key Insrastructure (PKI) is an arrangement that provides its users with means for confident and effective utilisation of public-key cryptography. An overview of non-hierarchical example of PKI – Pretty Good Privacy (PGP) – will be given, which uses the concept of a Web of Trust – a structure where any user can act as a certificate authority and assert validity of other users’ certificates.

A user A of PGP before sending a message to another user X must calculate the validity of the other user’s certificate using the public information about the network and their private information about the trustworthiness of the users on the certification paths from A to X. This is normally done on the basis of the so-called trust metric. Trust metrics and decision rules based on them are a field of active research – it is unlikely that anyone will invent a single perfect decision rule since there are many conflicting desiderata. In particular, it is desirable that such a decision rule
– be immune to various attacks;
– be easily computable;
– satisfy nice normative properties (axioms).

This is an introductory talk on this subject. No specific knowledge of cryptography will be assumed. Social networks people are especially invited.

Seminar: A. Clearwater 2014-03-11

Speaker:     Adam Clearwater
Affiliation: The University of Auckland
Title:       The single-crossing property on a tree
Date:        Tuesday, 11 Mar 2014
Time:        5:00 pm
Location:    Room 412, Science Centre (303)

We generalize the classical single-crossing property to single-crossing property on trees and obtain new ways to construct the so-called Condorcet domains which are sets of linear orders which possess the property that every profile composed from those orders have transitive majority relation. We prove that for any tree there exist profiles that are single-crossing on that tree; moreover, that tree is minimal in this respect for at least one such profile. Finally, we provide a polynomial-time algorithm to recognize whether or not a given profile is single-crossing with respect to some tree. We also show that finding winners for Chamberlin-Courant rule is polynomial  for profiles that are single-crossing on trees.

This paper is a product of Adam’s Summer Scholarship project. The research was conducted jointly with Clemens Puppe (KIT, Germany) and Arkadii Slinko.