## Seminars and Colloquia by Series

Wednesday, September 6, 2017 - 12:10 , Location: Skiles 006 , Virginia Ahalt , DoD , Organizer: Timothy Duff
SPORT is a 12-week *PAID* summer internship offered by the National Security Agency (NSA) that provides 8 U.S. Citizen graduate students the opportunity to apply their technical skills to current, real-world operations research problems at the NSA.  SPORT looks for strong students in operations research, applied math, computer science, data science, industrial and systems engineering, and other related fields. Program Highlights: -- Paid internship (12 weeks, late May to mid-August 2018) -- Applications accepted September 1 - October 31, 2017 -- Opportunity to apply operations research, mathematics, statistics, computer science, and/or engineering skills -- Real NSA mission problems -- Paid annual and sick leave, housing available, most travel costs covered -- Flexible work schedule -- Opportunity to network with other Intelligence Agencies
Wednesday, September 6, 2017 - 01:55 , Location: Skiles 005 , Shahaf Nitzan , Georgia Tech , Organizer: Shahaf Nitzan
The classical Balian-Low theorem states that if both a function and it's Fourier transform decay too fast then the Gabor system generated by this function (i.e. the system obtained from this function by taking integer translations and integer modulations) cannot be an orthonormal basis or a Riesz basis.Though it provides for an excellent `thumbs--rule' in time-frequency analysis, the Balian--Low theorem is not adaptable to many applications. This is due to the fact that in realistic situations information about a signal is given by a finite dimensional vector rather then by a function over the real line. In this work we obtain an analog of the Balian--Low theorem in the finite dimensional setting, as well as analogs to some of its extensions. Moreover, we will note that the classical Balian--Low theorem can be derived from these finite dimensional analogs.
Monday, September 4, 2017 - 14:15 , Location: Skiles 006 , None , None , Organizer: Dan Margalit
Friday, September 1, 2017 - 14:00 , Location: Skiles 005 , Moumanti Podder , Georgia Tech , , Organizer: Lutz Warnke
This talk will focus on tree automata, which are tools to analyze existential monadic second order properties of rooted trees. A tree automaton A consists of a finite set \Sigma of colours, and a map \Gamma: \mathbb{N}^\Sigma \rightarrow \Sigma. Given a rooted tree T and a colouring \omega: V(T) \rightarrow \Sigma, we call \omega compatible with automaton A if for every v \in V(T), we have \omega(v) = \Gamma(\vec{n}), where \vec{n} = (n_\sigma: \sigma \in \Sigma) and n_\sigma is the number of children of v with colour \sigma. Under the Galton-Watson branching process set-up, if p_\sigma denotes the probability that a node is coloured \sigma, then \vec{p} = (p_\sigma: \sigma \in \Sigma) is obtained as a fixed point of a system of equations. But this system need not have a unique fixed point.  Our question attempts to answer whether a fixed point of such a system simply arises out of analytic reasons, or if it admits of a probabilistic interpretation. I shall formally defined interpretation, and provide a nearly complete description of necessary and sufficient conditions for a fixed point to not admit an interpretation, in which case it is called rogue.Joint work with Tobias Johnson and Fiona Skerman.
Friday, September 1, 2017 - 13:55 , Location: Skiles 006 , None , None , Organizer: John Etnyre
Thursday, August 31, 2017 - 15:05 , Location: Skiles 006 , , University of Wisconsin-Madison , Organizer: Mayya Zhilova
We discuss two recent results concerning disease modeling on networks. The infection is assumed to spread via contagion (e.g., transmission over the edges of an underlying network). In the first scenario, we observe the infection status of individuals at a particular time instance and the goal is to identify a confidence set of nodes that contain the source of the infection with high probability. We show that when the underlying graph is a tree with certain regularity properties and the structure of the graph is known, confidence sets may be constructed with cardinality independent of the size of the infection set. In the scenario, the goal is to infer the network structure of the underlying graph based on knowledge of the infected individuals. We develop a hypothesis test based on permutation testing, and describe a sufficient condition for the validity of the hypothesis test based on automorphism groups of the graphs involved in the hypothesis test. This is joint work with Justin Khim (UPenn).
Wednesday, August 30, 2017 - 13:55 , Location: Skiles 006 , None , None , Organizer: John Etnyre
Series: Other Talks
Tuesday, August 29, 2017 - 11:00 , Location: Skiles Atrium , Rachel Kuske , Georgia Tech , Organizer: Sharon McDowell
Introduction of the new Faculty, Postdocs, Academic Professionals and Staff.
Friday, August 25, 2017 - 13:55 , Location: Skiles 005 , Prof. Song Li , Zhejiang University , Organizer: Haomin Zhou
In this talk, i shall provide some optimal PIR bounds, which confirmed a conjecture on optimal RIP bound. Furtheremore, i shall also investigate some results on signals recovery with redundant dictionaries, which are also related to statistics and sparse representation.
Friday, August 25, 2017 - 13:55 , Location: Skiles 006 , None , None , Organizer: John Etnyre