Faculty of Mathematics, University of Waterloo

WebNotice Postings: 26-Sep-2016 through 02-Oct-2016

Postings for all Departments

Monday, 26 September 2016, 10:15AM -- DC 1302
Database Research Group Seminar -- Computer Science
Speaker: Per-Åke (Paul) Larson, Microsoft Research
Title: "Database Systems Meet Non-Volatile Memory (NVRAM"
Abstract: Byte addressable, non-volatile memory (NVRAM) with close to DRAM speed is becoming a reality. Low capacity DIMMs (10s of MBs) are already available and high capacity DIMMs (100s of GB) are expected in 2017. This talk is about how database systems, in particular, main-memory databases can benefit from NVRAM. It will begin with an outline of the characteristics of different types of NVRAM and how the operating system manages and provides applications access to NVRAM. Ensuring that data structures such as indexes in NVRAM can be recovered to a consistent state without data or memory loss after a crash is challenging. The talk will discuss what causes the difficulties and how they can be overcome. It will then show how NVRAM can be used to greatly reduce the latency of commit processing and replication. By storing a main-memory database, including indexes, it is possible to achieve near-instant recovery after a crash. The final part of the talk will discuss how this can be achieved.

Biography: Paul has conducted research in the database field for over 35 years. He served as a Professor in the Department of Computer Science at the University of Waterloo for 15 years and as a Principal Researcher at Microsoft Research for close to 20 years. Paul is a Fellow of the ACM. He has worked in a variety of areas: file structures, materialized views, query processing, query optimization, column stores, and main-memory databases among others. Paul collaborated closely with the SQL Server team to drastically improve SQL Server performance by adding column store indexes, a novel main-memory engine (Hekaton), and support for real-time analytics.

Tuesday, 27 September 2016, 2:00PM -- MC 6460
Miscellaneous -- Applied Mathematics
Speaker: Matthew Harris, Department of Applied Mathematics
Title: "PhD Comp Seminar | Instabilities of fronts"
Abstract: Fronts, locations of large density gradients, are of major importance in both the atmosphere and the oceans. In particular, oceanic fronts play a major role in the ecosystem of the oceans and atmospheric fronts dramatically affect weather patterns. The study of fronts is naturally split into two sections, the development of a front, known as frontogenesis, and the subsequent collapse. The focus of this talk is on the collapse of a front. In particular, we work within the 2 layer shallow water framework and apply linear stability theory to a geostrophically balanced background state in order to find the most unstable modes for a range of Rossby and Richardson numbers. The spatial structure of these modes is then examined.

Tuesday, 27 September 2016, 3:00PM -- MC 6486
Graduate Student Seminar Seminar -- Combinatorics and Optimization
Speaker: Alfred Menezes, University of Waterloo
Title: "Post-PhD"
Abstract: I will discuss the various career options that may be available after completion of your Ph.D. (or M.Math. degree). I will also offer some advice on how to best make use of your graduate school experience in order to achieve your career goals.

Tuesday, 27 September 2016, 3:30PM -- MC 5417
Computability Learning Seminar -- Pure Mathematics
Speaker: Mohammad Mahmoud, Department of Pure Mathematics University of Waterloo
Title: "“R.i.c.e. relations”"
Abstract: This week we start chapter 2 and introduce some Relatively intrinsic notions. Basically we discuss R.i.c.e. (relatively intrinsic computably enumerable) relations and give some examples. Our goal is to prove a characterization theorem for R.i.c.e. relations.

Thursday, 29 September 2016, 1:30AM - ** Time Change ** - now at 1:30PM
** See updated entry for additional event information **
Speaker: Anton Mosunov, Department of Pure Mathematics University of Waterloo
Title: "“What do we know about aliquot sequences? (in honor of Richard Guy’s 100th birthday) ”"

Thursday, 29 September 2016, 12:00PM -- DC2306C
Artificial Intelligence Lab PhD Seminar -- Computer Science
Speaker: Hassan Ashtiani, David R. Cheriton School of Computer Science
Title: "Clustering with Same-Cluster Queries (Joint work with Shrinu Kushagra and Shai Ben-David)"
Abstract: We propose a framework for Semi-Supervised Active Clustering framework (SSAC), where the learner is allowed to interact with a domain expert, asking whether two given instances belong to the same cluster or not. We study the query and computational complexity of clustering in this framework and consider a setting where the expert conforms to a center-based clustering with a notion of margin. We show that there is a trade off between computational complexity and query complexity; We prove that for the case of k-means clustering (i.e., when the expert conforms to a solution of k-means), having access to relatively few such queries allows efficient solutions to otherwise NP hard problems. We also prove a lower bound on the number of queries needed to have a computationally efficient clustering algorithm in this setting. This is a joint work with Shrinu Kushagra and Shai Ben-David.

Thursday, 29 September 2016, 1:30PM -- MC 5479 true
Number Theory Seminar Seminar -- Pure Mathematics
Speaker: Anton Mosunov, Department of Pure Mathematics University of Waterloo
Title: "“What do we know about aliquot sequences? (in honor of Richard Guy’s 100th birthday) ”"
Abstract: Let s(n) denote the sum of the proper divisors of n and sk(n) denote the k-th iterate of s. An aliquot sequence starting at n is a sequence of the form n,s(n),s2(n),s3(n), and so on. There has been a lot of discussion about the convergence of these sequences. On the one hand, the Catalan- Dickson conjecture (1913) states that all aliquot sequences converge. On the other hand, there exists a heuristic counter-argument due to Guy and Selfridge (1975), according to which the divergence occurs for almost all aliquot sequences starting with an even number. In this talk, we intend to summarize all theoretical observations about aliquot sequences and present a series of computational results on the heuristics of Guy and Selfridge. This is joint work with Kevin Chum, Richard K. Guy and Michael J. Jacobson, Jr. (University of Calgary).

Thursday, 29 September 2016, 2:30PM -- MC 5413
Logic Seminar Seminar -- Pure Mathematics
Speaker: Christopher Hawthorne, Department of Pure Mathematics University of Waterloo
Title: "“Model theory and formal languages”"
Abstract: A language is a set of strings over a fixed, finite alphabet. In the study of formal languages, one considers natural classes of languages (typically defined by some model of computation) and studies properties of these classes. In this talk, I will outline my attempts to analyze formal languages using model theory; to do this, we will view languages as subsets of finitely generated free monoids, and consider the model theory of the latter. We will first see some basic model-theoretic properties of free monoids and their complete theories. We will then consider the computational power of definable and quantifier-free definable sets in one variable: we will see that the quantifier-free definable sets fit nicely into the complexity hierarchy of formal languages, and we will conjecture that the definable sets do not. Finally, we will consider regular languages, a class of great theoretical and practical interest; we will characterize regularity of a language by properties of the type space of an associated structure. No knowledge of formal languages will be assumed.

Thursday, 29 September 2016, 3:30PM -- DC 1302 true
Computer Science Lecture -- Computer Science
Speaker: Gail Murphy, Computer Science Professor and Associate VP Research & International pro tem, University of British Columbia
Title: "Human-Centric Software Development Tools"
Abstract: Abstract: Software systems are sometimes referred to as the most complex artifacts ever engineered. To help create these systems, software engineers use many tools, such as compilers and debuggers. The vast majority of these tools have been designed from an artifact-centric perspective; for instance, a compiler takes one representation of a program and changes it into another representation. In this talk, I will argue that a human-centric approach to designing software development tools is essential to accelerate our ability to build complex software systems with desired qualities. A human-centric approach involves a focus on how humans work with computational structures and with each other. I will describe how we take this approach in my research group from studies of how software engineers work through to the development of tools and the subsequent study of those tools in the wild world of software development. I will use as an example, the science behind the Eclipse Mylyn tool developed in my research group; Mylyn is downloaded millions of times per month and has formed the basis for a start-up enterprise software development company called Tasktop Technologies.

Biography: Gail C. Murphy is a Professor of Computer Science and Associate Vice President Research and International pro tem at UBC. She is also a co-founder and Chief Scientist at Tasktop Technologies Inc. Her research interests are in improving the productivity of software developers and knowledge workers by giving them tools to identify, manage and coordinate the information that really matters for their work. She is a Fellow of the Royal Society of Canada, an ACM Distinguished Scientist and a recipient of such awards as a University of Washington Computer Science & Engineering Alumni Achievement Award, an NSERC E.W.R. Stacie Memorial Fellowship and the AITO Dahl-Nygaard Junior Prize.

Thursday, 29 September 2016, 3:30PM -- Math & Computer, Room 5479
Seminar -- Combinatorics and Optimization
Speaker: Edward Lee, Dept. of Combinatorics & Optimization, University of Waterloo
Title: "Circle Graph Obstructions"
Abstract: A circle graph is the intersection graph of a set of chords drawn on a circle. We present a graphic proof of Bouchet's characterization of the class of circle graphs.

Thursday, 29 September 2016, 4:00PM -- M3 3127
Seminar -- Statistics & Actuarial Science
Speaker: Rui Sun, University of Toronto
Title: "A W-test for epistasis testing with application in Bipolar Disorder GWAS Data"
Remarks: Refreshments will be provided.
Abstract: Epistasis plays an essential role in the development of complex diseases. Interaction methods face common challenge of seeking a balance between persistent power, model complexity, computation efficiency, and validity of identified bio-markers. We introduce a novel W-test to identify pairwise epistasis effect, which measures the distributional difference between cases and controls through a combined log odds ratio. The test is model-free, fast, and inherits a Chi-squared distribution with data adaptive degrees of freedom. No permutation is needed to obtain the P-values. Simulation studies demonstrated that the W-test is more powerful in low frequency variants environment than alternative methods, which are the Chi-squared test, logistic regression and multifactor-dimensionality reduction (MDR). In two independent real bipolar disorder genome-wide associations (GWAS) datasets, the W-test identified significant interactions pairs that can be replicated, including SLIT3-CENPN, SLIT3-TMEM132D, CNTNAP2-NDST4 and CNTCAP2-RTN4R. The genes in the pairs play central roles in neurotransmission and synapse formation. A majority of the identified loci are undiscoverable by main effect and are low frequency variants. The proposed method offers a powerful alternative tool for mapping the genetic puzzle underlying complex disorders.

Friday, 30 September 2016, 2:30PM -- MC 5413
Geometry & Topology Seminar Seminar -- Pure Mathematics
Speaker: Ruxandra Moraru, Department of Pure Mathematics University of Waterloo
Title: "“Moduli spaces of generalized holomorphic bundles”"
Abstract: Generalized holomorphic bundles are the analogues of holomorphic vector bundles in the generalized geometry setting. For some generalized complex structures, these bundles corre- spond to co-Higgs bundles, flat bundles or Poisson modules. In this talk, I will discuss the deformation theory of generalized holomorphic bundles on generalized Kaehler manifolds. I will also give explicit examples of moduli spaces of generalized holomorphic bundles on Hopf surfaces and on Inoue surfaces. This is joint work with Shengda Hu and Mohamed El Alami.

Friday, 30 September 2016, 3:30PM -- MC 5417
Analysis Seminar Seminar -- Pure Mathematics
Speaker: Xiao Xiong, Seoul National University
Title: "“Characterizations of operator-valued Hardy spaces.”"
Abstract: I will introduce the operator-valued Hardy spaces studied by Tao Mei, and show that the Poisson kernel in Mei’s definition of these spaces can be replaced by any reasonable test function. An important example of such test function is given by positive-order Riesz potential of the Poisson kernel.

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