Title
HOW TO DETECT A SALAMI SLICER: A STOCHASTIC CONTROLLER-AND-STOPPER GAME WITH UNKNOWN COMPETITION
Abstract
We consider a stochastic game of control and stopping specified in terms of a process X-t = -theta Lambda(t)+W-t, representing the holdings of Player 1, where W is a Brownian motion, theta is a Bernoulli random variable indicating whether Player 2 is active or not, and Lambda is a nondecreasing continuous process representing the accumulated "theft" or "fraud" performed by Player 2 (if active) against Player 1. Player 1 cannot observe theta or Lambda directly but can merely observe the path of the process X and may choose a stopping rule tau to deactivate Player 2 at a cost M. Player 1 thus does not know if she is the victim of fraud or not and operates in this sense under unknown competition. Player 2 can observe both theta and W and seeks to choose a fraud strategy Lambda that maximizes the expected discounted amount E [integral(tau)(0) e(-rs)d Lambda(s)vertical bar theta = 1], whereas Player 1 seeks to choose the stopping strategy tau so as to minimize the expected discounted cost E[theta integral(tau)(0) e(-rs)d Lambda(s) + e(-rr)MI({tau, infinity})]. This non-zero-sum game belongs to a class of stochastic dynamic games with unknown competition and continuous controls and is motivated by applications in fraud detection; it combines filtering (detection), stochastic control, optimal stopping, strategic features (games), and asymmetric information. We derive Nash equilibria for this game; for some parameter values we find an equilibrium in pure strategies, and for other parameter values we find an equilibrium by allowing for randomized stopping strategies.
Year
DOI
Venue
2022
10.1137/21M139044X
SIAM JOURNAL ON CONTROL AND OPTIMIZATION
Keywords
DocType
Volume
stochastic game theory, stochastic optimal control, fraud detection, optimal stopping
Journal
60
Issue
ISSN
Citations 
1
0363-0129
0
PageRank 
References 
Authors
0.34
0
3
Name
Order
Citations
PageRank
Erik Ekström100.34
Kristoffer Lindensjö201.01
Marcus Olofsson300.34