Upcoming MAMS Colloquium Series
Fall 2025
10/31/2025, Friday 3:15-4:15 pm in Nord 356
Speaker: Hyunjoong Kim (University of Cincinnati)
Title: When Adventurous Individuals Emerge
Abstract: Exploration in uncertain and changing environments poses a fundamental dilemma:
while it benefits the group by generating valuable information, it imposesdirect costs on individual explorers. What conditions allow such adventurousindividuals to exist and persist in decentralized collectives? We address thisquestion using a normative model of collective foraging in which agents decidewhether to commit or remain idle, with rewards and information shared acrossthe group. Using dynamic programming and asymptotic analysis, we show thatoptimal performance arises from structured heterogeneity: a small,heterogeneous subset of risk-tolerant explorers ventures even when expectedreturns are negative, while the majority of risk-averse individuals commit collectivelyonce conditions become favorable. This decentralized composition matches theefficiency of a centrally coordinated group through simple threshold-basedrules.
The degree of heterogeneity peaks at intermediate commitmentcost and moderate environmental switch amplitude but diminished in rapidlychanging environments. These results reveal when and why adventurousindividuals emerge, showing how collectives self-organize to balanceexploration and exploitation under uncertainty.
9/26/2025, Friday 3:15-4:15 pm in DeGrace Hall 312
Speaker: Grzegorz (“Greg”) Rempala (The Ohio State University)
Title: Estimation of the Effective Reproduction Number Using Dynamical Survival Analysis
Abstract: The effective reproduction number (Rt) is a key epidemiological quantity that reflects the temporal dynamics of an infectious disease outbreak and serves as a critical measure of intervention effectiveness. Accurate and timely estimation of Rt is particularly important in the early stages of an epidemic, when public health responses are most sensitive to uncertainty. Conventional approaches often rely on assumptions about the generation or serial interval and are further complicated by incomplete or delayed reporting of cases, leading to biased estimates.
In this talk, I will present a new estimation framework based on Dynamical Survival Analysis, which avoids the need to specify the generation or serial interval. The method leverages likelihood-based inference applied to individual-level infection time data within an SEIR modeling context and demonstrates improved robustness when classical assumptions are violated.
This work is joint with Micaela Richter and Eben Kenah.
9/12/2025, Friday 3:15-4:15 pm in Nord 356
Speaker: Shiri Artstein-Avidan (Tel Aviv University)
Title: Ball-bodies, old and new
Abstract: We will discuss the class of bodies with sectional curvatures bounded below by 1 (it goes by many names: ball bodies, hyperconvex bodies, 1-convex sets, ball summands) which has been studied by various authors in several different contexts, and relates to many open problems in geometry and elsewhere. We will give emphasis on the natural (and unique, in many senses) duality operation defined on the class, and show new results regarding a variant of affine surface area defined for this class by Schuett, Werner and Yalikun.