My primary research interest is in microeconomic theory, with an emphasis on game theory and decision theory. I have worked on existence of equilibrium in games with payoffs that lack the usual continuity properties, as well as games with incomplete information with neither an *a priori* order structure nor convexity assumptions on strategy spaces or payoff functions. That work has resulted in several working papers, including a contribution to the fixed point theory of decomposable sets in non-linear analysis. More recently, I have been studying learning and belief formation in an environment in which little information is available to the economic agent and surprises are frequent. I have also been continuously involved in the organization of conferences, workshops, seminars, and minicourses for the Australian National University, many of them multidisciplinary.

### Working papers

**On the existence of equilibrium in Bayesian games without complementarities [pdf]**

(with Rabee Tourky)

This paper presents new results on the existence of Bayesian equilibria in pure strategies of a specified functional form. These results broaden the scope of methods developed by Reny (2011) well beyond monotone pure strategies. Applications include natural models of first-price and all-pay auctions not covered by previous existence results. To illustrate the scope of our results, we present two applications to auctions: (i) a first-price auction in which bidders’ payoffs have a very general interdependence structure; and (ii) an all-pay auction with non-monotone equilibrium.

**Keywords: **Bayesian games, monotone strategies, pure-strategy equilibrium, auctions

**Paying to overbid **

(with Larry Samuelson)

Overbidding appears to be common in a variety of auctions, both in the laboratory and in the field. This paper suggests an explanation for overbidding based on agency costs. Principals must hire agents to bid in an auction, giving rise to a competing-mechanisms problem with informational interdependence among the agents. The agents can exert unobserved and costly effort to collect information about the value of the object. The optimal remuneration scheme must induce the agents to exert effort and then appropriately condition their bids on their information. We identify conditions under which this remuneration scheme induces overbidding.

**Keywords:** auctions, moral hazard, competing mechanisms

**Bargaining with multiple partners **

(with Anna Sanktjohanser)

We analyze a model of bargaining with two sides, say buyers and sellers. Each agent wants to make exactly one deal. Each player can choose from multiple possible bargaining partners, and some may be a better match than others. We analyze how the presence of alternative bargaining partners affects the outcome of a bilateral bargaining agreement.

**Keywords:** bargaining

**A fixed point theorem for closed-graphed decomposable-valued correspondences [pdf]**

(with Rabee Tourky)

Extending the fixed-point theorem of Cellina–Fryszkowski [1, 7], which is for functions on decomposable sets, to decomposable-set-valued correspondences has been an unresolved challenge since the early attempt of Cellina, Colombo, and Fonda [2]. Motivated by the fixed point problem of Reny [12] arising in Bayesian games, this paper proves such a theorem.

**Keywords:** fixed point, decomposable set

### Publications

- Grant, S., Meneghel, I., and Tourky, R. (2022). “Learning under unawareness.”
*Economic Theory*, 74(2), pp. 447–475. - Grant, S., Kline, J., Meneghel, I., Quiggin, J., and Tourky, R. (2016). “A theory of robust experiments for choice under uncertainty.”
*Journal of Economic Theory*, 165, pp. 124–151. - Grant, S., Meneghel, I., and Tourky, R. (2016). “Savage games.”
*Theoretical Economics*, 1 (2), pp. 641–682. - Barelli, P. and Meneghel, I. (2013). “A note on the equilibrium existence problem in discontinuous games.”
*Econometrica*, 81 (2), pp. 813–824.