Epidemiology: A mortal foe

Mortal Multi-Armed Bandits

We formulate and study a new variant of the k-armed bandit problem, motivated by e-commerce applications. In our model, arms have (stochastic) lifetime after which they expire. In this setting an algorithm needs to continuously explore new arms, in contrast to the standard k-armed bandit model in which arms are available indefinitely and exploration is reduced once an optimal arm is identified ...

Evolving mortal networks.

We discuss a class of models for the evolution of tree networks in which new nodes are recruited into the network at random times, and nodes already in the network may die at random times. Stochastic mechanisms for growth and death of the network that are either sensitive or insensitive to the coordination number or degree of nodes are studied using simulations and mean-field approximations. Cr...

Bacteria and phagocytes: mortal enemies.

The research presented in this issue finds historical resonance in a classical scientific debate. Russian biologist Ilya Metchnikoff [1, 2] was awarded the Nobel Prize in 1908 for the development of the phagocyte theory, the central tenet of which was that the ‘swallowing and digestion’ of bacteria by circulating ‘white corpuscles’ (neutrophils and macrophages), enhanced by prior opsonization, ...

When is a Pair of Matrices Mortal?

A set of matrices over the integers is said to be length k mortal with k positive integer if the zero matrix can be expressed as a product of length k of matrices in the set The set is said to be mortal if it is length k mortal for some nite k We show that the problem of deciding whether a pair of integer matrices is mortal is undecidable and that the problem of deciding for a given k whether a...

Mortal outcomes when opportunity knocks.