September 18, 2015
Goergen 109
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Physics of Ranking Processes

Gourab Ghoshal

Department of Physics, Computer Science, and Mathematics

The world is addicted to ranking: everything, from the reputation of scientists, journals, and universities to purchasing decisions and company performance is driven by measured or perceived differences between them. While significant attention is paid to the “winners”, items at the top of the list, little scientific attention is devoted to the ranking process itself. There is a good reason for this: the sheer heterogeneity of the ranked systems, spanning such a diverse set of subjects, each with their own specific peculiarities, makes it seem a hopeless exercise to seek order in such a volatile subject. Yet, in some way, ranking serves as a coarse-grained indicator of many socio-economic factors, making it imperative to understand the mechanisms driving it. In this talk I will attempt to do just that, introducing the concept of ranking stability as it relates to eigenvalue based algorithms such as Google’s page rank and then moving on to the empirical examination of a plethora of temporal datasets that enables us to develop a “phenomenological” theory capturing the dynamics of ranking. Implications and future directions will also be explored.

Ongoing Research Talk

Genomic Consequences of Recent Loss of Sexual Reproduction

Yogeshwar Kelkar

Department of Biostatistics and Computational Biology

Sex is an inefficient way to reproduce because of the associated costs. One of these costs is intralocus sexual antagonism (SA), which takes place when the optimum phenotype differs between males and females. Over the long term, this can be resolved by mechanisms such as sex-biased splicing, and sex- biased expression of gene duplicates. What happens when the pressure of SA is released, as in the case of species that have recently become asexual? How do the ancestrally sex-biased genes respond? Here we examine genome evolution in Muscidifurax uniraptor, a parthenogenetically reproducing parasatoid wasp, in the context of two closely related sexually reproducing lineages (Muscidifurax raptorellus and Muscidifurax raptor). We find that female and well as male-biased genes experience high rates of divergence in asexual lineages.

Friday, September 18, 2015

11:30 am - 1:00 pm

Goergen 109 (River Campus)