# Seminars and Colloquia

## Other

Apr 3

#### Computer Science Lecture Series: Pooyan Jamshidi, USC, Adversarial Machine Learning

02:45 pm

Exley Science Center Tower ESC 121

Ensembles of Many Diverse Weak Defenses can be Strong: Defending Deep Neural Networks Against Adversarial Attacks Abstract: Despite achieving state-of-the-art performance across many domains, machine learning systems are highly vulnerable to subtle adversarial perturbations. Although defense approaches have been proposed in recent years, many have been bypassed by even weak adversarial attacks. Previous studies showed that ensembles created by combining multiple weak defenses (i.e., input data transformations) are still weak. In this talk, I will show that it is indeed possible to construct effective ensembles using weak defenses to block adversarial attacks. However, to do so requires a diverse set of such weak defenses. Based on this motivation, I will present Athena, an extensible framework for building effective defenses to adversarial attacks against machine learning systems. I will talk about the effectiveness of ensemble strategies with a diverse set of many weak defenses that comprise transforming the inputs (e.g., rotation, shifting, noising, denoising, and many more) before feeding them to target deep neural network classifiers. I will also discuss the effectiveness of the ensembles with adversarial examples generated by various adversaries in different threat models. In the second half of the talk, I will explain why building defenses based on the idea of many diverse weak defenses works, when it is most effective, and what its inherent limitations and overhead are. Bio: Pooyan Jamshidi is an Assistant Professor at the University of South Carolina. He directs the AISys Lab, where he investigates the development of novel algorithmic and theoretically principled methods for machine learning systems. Before his current position, he was a research associate at Carnegie Mellon University and Imperial College London, where he primarily worked on transfer learning for performance understanding of highly-configurable systems including robotics and big data systems. Pooyans general research interests are at the intersection of systems/software and machine learning. He received his Ph.D. in Computer Science at Dublin City University in 2014, and MS and BS degrees in Computer Science and Math from the Amirkabir University of Technology in 2003 and 2006 respectively. More info: http://pooyanjamshidi.github. io/

Oct 9

#### Undergrad Computer Science Club

04:30 pm

Exley Science Center Tower ESC 638

Daichi Onda 17' will tell us about his experience working at Amazon and his "Wesleyan Alumni in Tech network" project that he started to help CS students look for tech jobs.

Oct 4

#### Math Club Presentations

12:00 pm

Exley Science Center (Not Tower) ESC 184 (Woodhead Lounge)

INTRINSIC PROPERTIES OF GRAPHS EMBEDDED IN 3 ERICA FLAPAN, Editor in Chief of the Notices of the American Mathematical Society Knot theory is the study of embeddings of simple closed curves in 3 . A natural extension of knot theory is the study of embeddings of graphs in 3 . However, in contrast with knots, the structure of a graph can be complex, and this can affect all of its embeddings. If every embedding of a graph has a particular property, then we say that property is intrinsic to the graph. For example, a graph is said to be intrinsically knotted if every embedding of the graph in 3 contains a knot. In this talk I will introduce intrinsic knotting and other intrinsic properties of graphs, and present some open problems in the area.

Apr 12

#### Mathematics Colloquium

04:20 pm

Exley Science Center Tower ESC 121

Aaron Brown, University of Chicago Recent progress in the Zimmer program Abstract: The Zimmer program refers to a number of questions and conjectures about actions of certain discrete groups, namely, lattices in higher-rank simple Lie groups. The primary example example of a such a group is SL(n,R). In the past few years, there has been significant progress in the Zimmer program. In my talk, I will discuss a recent proof of Zimmer's conjecture which shows that (cocompact and certain non-uniform) higher-rank lattices do not act on manifolds with low dimension. I will also discuss recent results and work in progress that classify all possible non-trivial actions under certain dynamical or dimension assumptions.