The Center of Mathematic Sciences and Applications will host a conference on From Algebraic Geometry to Vision and AI: A Symposium Celebrating the Mathematical Work of David Mumford. The event will be held in the Harvard Science Center, Hall D.
For a list of lodging options convenient to the Center, please visit our recommended lodgings page.
Confirmed speakers and panelists:
*This event is jointly supported by the CMSA, National Science Foundation, and the International Science Foundation of Cambridge.
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The Big Data Conference features many speakers from the Harvard community as well as scholars from across the globe, with talks focusing on computer science, statistics, math and physics, and economics. This is the third conference on Big Data the Center will host as part of our annual events, and is coorganized by Richard Freeman, Scott Kominers, Jun Liu, HorngTzer Yau and ShingTung Yau.
To register for this event, please click here. For a list of lodging options convenient to the Center, please visit our recommended lodgings page.
Please note that lunch will not be provided during the conference, but a map of Harvard Square with a list of local restaurants can be found by clicking Map & Restaurants.
Confirmed Speakers:
Following the conference, there will be a twoday workshop from August 2021. The workshop is organized by Scott Kominers, and will feature:
Conference Schedule
The schedule below is tentative and subject to change. A PDF version of the schedule can also be downloaded here.
Time  Speaker  Topic 
8:30 am – 9:00 am  Breakfast  
9:00 am – 9:40 am  Mohammad Akbarpour  Title: Information aggregation in overlapping generations and the emergence of experts
Abstract: We study a model of social learning with “overlapping generations”, where agents meet others and share data about an underlying state over time. We examine under what conditions the society will produce individuals with precise knowledge about the state of the world. There are two information sharing regimes in our model: Under the full information sharing technology, individuals exchange the information about their point estimates of an underlying state, as well as their sources (or the precision of their signals) and update their beliefs by taking a weighted average. Under the limited information sharing technology, agents only observe the information about the point estimates of those they meet, and update their beliefs by taking a weighted average, where weights can depend on the sequence of meetings, as well as the labels. Our main result shows that, unlike most social learning settings, using such linear learning rules do not guide the society (or even a fraction of its members) to learn the truth, and having access to, and exploiting knowledge of the precision of a source signal are essential for efficient social learning (joint with Amin Saberi & Ali Shameli). 
9:40 am – 10:20 am  Lucas Janson  Title: ModelFree Knockoffs For HighDimensional Controlled Variable Selection
Abstract: Many contemporary largescale applications involve building interpretable models linking a large set of potential covariates to a response in a nonlinear fashion, such as when the response is binary. Although this modeling problem has been extensively studied, it remains unclear how to effectively control the fraction of false discoveries even in highdimensional logistic regression, not to mention general highdimensional nonlinear models. To address such a practical problem, we propose a new framework of modelfree knockoffs, which reads from a different perspective the knockoff procedure (Barber and Candès, 2015) originally designed for controlling the false discovery rate in linear models. The key innovation of our method is to construct knockoff variables probabilistically instead of geometrically. This enables modelfree knockoffs to deal with arbitrary (and unknown) conditional models and any dimensions, including when the dimensionality p exceeds the sample size n, while the original knockoffs procedure is constrained to homoscedastic linear models with n greater than or equal to p. Our approach requires the design matrix be random (independent and identically distributed rows) with a covariate distribution that is known, although we show our procedure to be robust to unknown/estimated distributions. As we require no knowledge/assumptions about the conditional distribution of the response, we effectively shift the burden of knowledge from the response to the covariates, in contrast to the canonical modelbased approach which assumes a parametric model for the response but very little about the covariates. To our knowledge, no other procedure solves the controlled variable selection problem in such generality, but in the restricted settings where competitors exist, we demonstrate the superior power of knockoffs through simulations. Finally, we apply our procedure to data from a casecontrol study of Crohn’s disease in the United Kingdom, making twice as many discoveries as the original analysis of the same data. 
10:20 am – 10:50 am  Break  
10:50 pm – 11:30 pm  Noureddine El Karoui  Title: Random matrices and highdimensional statistics: beyond covariance matrices
Abstract: Random matrices have played a central role in understanding very important statistical methods linked to covariance matrices (such as Principal Components Analysis, Canonical Correlation Analysis etc…) for several decades. In this talk, I’ll show that one can adopt a randommatrixinspired point of view to understand the performance of other widely used tools in statistics, such as Mestimators, and very common methods such as the bootstrap. I will focus on the highdimensional case, which captures well the situation of “moderately” difficult statistical problems, arguably one of the most relevant in practice. In this setting, I will show that random matrix ideas help upend conventional theoretical thinking (for instance about maximum likelihood methods) and highlight very serious practical problems with resampling methods. 
11:30 am – 12:10 pm  Nikhil Naik  Title: Understanding Urban Change with Computer Vision and Streetlevel Imagery
Abstract: Which neighborhoods experience physical improvements? In this work, we introduce a computer vision method to measure changes in the physical appearances of neighborhoods from timeseries streetlevel imagery. We connect changes in the physical appearance of five US cities with economic and demographic data and find three factors that predict neighborhood improvement. First, neighborhoods that are densely populated by collegeeducated adults are more likely to experience physical improvements. Second, neighborhoods with better initial appearances experience, on average, larger positive improvements. Third, neighborhood improvement correlates positively with physical proximity to the central business district and to other physically attractive neighborhoods. Together, our results illustrate the value of using computer vision methods and streetlevel imagery to understand the physical dynamics of cities. (Joint work with Edward L. Glaeser, Cesar A. Hidalgo, Scott Duke Kominers, and Ramesh Raskar.) 
12:10 pm – 12:25 pm  Data Science Lightning Talks  
12:25 pm – 1:30 pm  Lunch  
1:30 pm – 2:10 pm  Tracy Ke  Title: A new SVD approach to optimal topic estimation
Abstract: In the probabilistic topic models, the quantity of interest—a lowrank matrix consisting of topic vectors—is hidden in the text corpus matrix, masked by noise, and Singular Value Decomposition (SVD) is a potentially useful tool for learning such a lowrank matrix. However, the connection between this lowrank matrix and the singular vectors of the text corpus matrix are usually complicated and hard to spell out, so how to use SVD for learning topic models faces challenges. We overcome the challenge by revealing a surprising insight: there is a lowdimensional simplex structure which can be viewed as a bridge between the lowrank matrix of interest and the SVD of the text corpus matrix, and which allows us to conveniently reconstruct the former using the latter. Such an insight motivates a new SVDbased approach to learning topic models. For asymptotic analysis, we show that under a popular topic model (Hofmann, 1999), the convergence rate of the l1error of our method matches that of the minimax lower bound, up to a multilogarithmic term. In showing these results, we have derived new elementwise bounds on the singular vectors and several large deviation bounds for weakly dependent multinomial data. Our results on the convergence rate and asymptotical minimaxity are new. We have applied our method to two data sets, Associated Process (AP) and Statistics Literature Abstract (SLA), with encouraging results. In particular, there is a clear simplex structure associated with the SVD of the data matrices, which largely validates our discovery. 
2:10 pm – 2:50 pm  AlbertLászló Barabási  Title: Taming Complexity: From Network Science to Controlling Networks
Abstract: The ultimate proof of our understanding of biological or technological systems is reflected in our ability to control them. While control theory offers mathematical tools to steer engineered and natural systems towards a desired state, we lack a framework to control complex selforganized systems. Here we explore the controllability of an arbitrary complex network, identifying the set of driver nodes whose timedependent control can guide the system’s entire dynamics. We apply these tools to several real networks, unveiling how the network topology determines its controllability. Virtually all technological and biological networks must be able to control their internal processes. Given that, issues related to control deeply shape the topology and the vulnerability of real systems. Consequently unveiling the control principles of real networks, the goal of our research, forces us to address series of fundamental questions pertaining to our understanding of complex systems.

2:50 pm – 3:20 pm  Break  
3:20 pm – 4:00 pm  Marena Lin  Title: Optimizing climate variables for human impact studies
Abstract: Estimates of the relationship between climate variability and socioeconomic outcomes are often limited by the spatial resolution of the data. As studies aim to generalize the connection between climate and socioeconomic outcomes across countries, the best available socioeconomic data is at the national level (e.g. food production quantities, the incidence of warfare, averages of crime incidence, gender birth ratios). While these statistics may be trusted from government censuses, the appropriate metric for the corresponding climate or weather for a given year in a country is less obvious. For example, how do we estimate the temperatures in a country relevant to national food production and therefore food security? We demonstrate that highresolution spatiotemporal satellite data for vegetation can be used to estimate the weather variables that may be most relevant to food security and related socioeconomic outcomes. In particular, satellite proxies for vegetation over the African continent reflect the seasonal movement of the Intertropical Convergence Zone, a band of intense convection and rainfall. We also show that agricultural sensitivity to climate variability differs significantly between countries. This work is an example of the ways in which insitu and satellitebased observations are invaluable to both estimates of future climate variability and to continued monitoring of the earthhuman system. We discuss the current state of these records and potential challenges to their continuity. 
4:00 pm – 4:40 pm  Alex Peysakhovich  
4:40 pm – 5:20 pm  Tze Leung Lai  Title: Gradient boosting: Its role in big data analytics, underlying mathematical theory, and recent refinements
Abstract: We begin with a review of the history of gradient boosting, dating back to the LMS algorithm of Widrow and Hoff in 1960 and culminating in Freund and Schapire’s AdaBoost and Friedman’s gradient boosting and stochastic gradient boosting algorithms in the period 19992002 that heralded the big data era. The role played by gradient boosting in big data analytics, particularly with respect to deep learning, is then discussed. We also present some recent work on the mathematical theory of gradient boosting, which has led to some refinements that greatly improves the convergence properties and prediction performance of the methodology. 
Time  Speaker  Topic 
8:30 am – 9:00 am  Breakfast  
9:00 am – 9:40 am  Natesh Pillai  Title: Accelerating MCMC algorithms for Computationally Intensive Models via Local Approximations
Abstract: We construct a new framework for accelerating Markov chain Monte Carlo in posterior sampling problems where standard methods are limited by the computational cost of the likelihood, or of numerical models embedded therein. Our approach introduces local approximations of these models into the Metropolis–Hastings kernel, borrowing ideas from deterministic approximation theory, optimization, and experimental design. Previous efforts at integrating approximate models into inference typically sacrifice either the sampler’s exactness or efficiency; our work seeks to address these limitations by exploiting useful convergence characteristics of local approximations. We prove the ergodicity of our approximate Markov chain, showing that it samples asymptotically from the exact posterior distribution of interest. We describe variations of the algorithm that employ either local polynomial approximations or local Gaussian process regressors. Our theoretical results reinforce the key observation underlying this article: when the likelihood has some local regularity, the number of model evaluations per Markov chain Monte Carlo (MCMC) step can be greatly reduced without biasing the Monte Carlo average. Numerical experiments demonstrate multiple orderofmagnitude reductions in the number of forward model evaluations used in representative ordinary differential equation (ODE) and partial differential equation (PDE) inference problems, with both synthetic and real data. 
9:40 am – 10:20 am  Ravi Jagadeesan  Title: Designs for estimating the treatment effect in networks with interference
Abstract: In this paper we introduce new, easily implementable designs for drawing causal inference from randomized experiments on networks with interference. Inspired by the idea of matching in observational studies, we introduce the notion of considering a treatment assignment as a quasicoloring” on a graph. Our idea of a perfect quasicoloring strives to match every treated unit on a given network with a distinct control unit that has identical number of treated and control neighbors. For a wide range of interference functions encountered in applications, we show both by theory and simulations that the classical Neymanian estimator for the direct effect has desirable properties for our designs. This further extends to settings where homophily is present in addition to interference. 
10:20 am – 10:50 am  Break  
10:50 am – 11:30 am  Annie Liang  Title: The Theory is Predictive, but is it Complete? An Application to Human Generation of Randomness
Abstract: When we test a theory using data, it is common to focus on correctness: do the predictions of the theory match what we see in the data? But we also care about completeness: how much of the predictable variation in the data is captured by the theory? This question is difficult to answer, because in general we do not know how much “predictable variation” there is in the problem. In this paper, we consider approaches motivated by machine learning algorithms as a means of constructing a benchmark for the best attainable level of prediction. We illustrate our methods on the task of predicting humangenerated random sequences. Relative to a theoretical machine learning algorithm benchmark, we find that existing behavioral models explain roughly 15 percent of the predictable variation in this problem. This fraction is robust across several variations on the problem. We also consider a version of this approach for analyzing field data from domains in which human perception and generation of randomness has been used as a conceptual framework; these include sequential decisionmaking and repeated zerosum games. In these domains, our framework for testing the completeness of theories provides a way of assessing their effectiveness over different contexts; we find that despite some differences, the existing theories are fairly stable across our field domains in their performance relative to the benchmark. Overall, our results indicate that (i) there is a significant amount of structure in this problem that existing models have yet to capture and (ii) there are rich domains in which machine learning may provide a viable approach to testing completeness (joint with Jon Kleinberg and Sendhil Mullainathan). 
11:30 am – 12:10 pm  Zak Stone  Title: TensorFlow: Machine Learning for Everyone
Abstract: We’ve witnessed extraordinary breakthroughs in machine learning over the past several years. What kinds of things are possible now that weren’t possible before? How are opensource platforms like TensorFlow and hardware platforms like GPUs and Cloud TPUs accelerating machine learning progress? If these tools are new to you, how should you get started? In this session, you’ll hear about all of this and more from Zak Stone, the Product Manager for TensorFlow on the Google Brain team. 
12:10 pm – 1:30 pm  Lunch  
1:30 pm – 2:10 pm  Jann Spiess  Title: (Machine) Learning to Control in Experiments
Abstract: Machine learning focuses on highquality prediction rather than on (unbiased) parameter estimation, limiting its direct use in typical program evaluation applications. Still, many estimation tasks have implicit prediction components. In this talk, I discuss accounting for controls in treatment effect estimation as a prediction problem. In a canonical linear regression framework with highdimensional controls, I argue that OLS is dominated by a natural shrinkage estimator even for unbiased estimation when treatment is random; suggest a generalization that relaxes some parametric assumptions; and contrast my results with that for another implicit prediction problem, namely the first stage of an instrumental variables regression. 
2:10 pm – 2:50 pm  Bradly Stadie  Title: Learning to Learn Quickly: OneShot Imitation and Meta Learning
Abstract: Many reinforcement learning algorithms are bottlenecked by data collection costs and the brittleness of their solutions when faced with novel scenarios. 
2:50 pm – 3:20 pm  Break  
3:20 pm – 4:00 pm  HauTieng Wu  Title: When Medical Challenges Meet Modern Data Science
Abstract: Adaptive acquisition of correct features from massive datasets is at the core of modern data analysis. One particular interest in medicine is the extraction of hidden dynamics from a single observed time series composed of multiple oscillatory signals, which could be viewed as a singlechannel blind source separation problem. The mathematical and statistical problems are made challenging by the structure of the signal which consists of nonsinusoidal oscillations with time varying amplitude/frequency, and by the heteroscedastic nature of the noise. In this talk, I will discuss recent progress in solving this kind of problem by combining the cepstrumbased nonlinear timefrequency analysis and manifold learning technique. A particular solution will be given along with its theoretical properties. I will also discuss the application of this method to two medical problems – (1) the extraction of a fetal ECG signal from a single lead maternal abdominal ECG signal; (2) the simultaneous extraction of the instantaneous heart/respiratory rate from a PPG signal during exercise; (3) (optional depending on time) an application to atrial fibrillation signals. If time permits, the clinical trial results will be discussed. 
4:00 pm – 4:40 pm  Sifan Zhou  Title: Citing People Like Me: Homophily, Knowledge Spillovers, and Continuing a Career in Science
Abstract: Forward citation is widely used to measure the scientific merits of articles. This research studies millions of journal article citation records in life sciences from MEDLINE and finds that authors of the same gender, the same ethnicity, sharing common collaborators, working in the same institution, or being geographically close are more likely (and quickly) to cite each other than predicted by their proportion among authors working on the same research topics. This phenomenon reveals how social and geographic distances influence the quantity and speed of knowledge spillovers. Given the importance of forward citations in academic evaluation system, citation homophily potentially put authors from minority group at a disadvantage. I then show how it influences scientists’ chances to survive in the academia and continue publishing. Based on joint work with Richard Freeman. 
This workshop will focus on new developments in coding and information theory that sit at the intersection of combinatorics and complexity, and will bring together researchers from several communities — coding theory, information theory, combinatorics, and complexity theory — to exchange ideas and form collaborations to attack these problems.
Squarely in this intersection of combinatorics and complexity, locally testable/correctable codes and listdecodable codes both have deep connections to (and in some cases, direct motivation from) complexity theory and pseudorandomness, and recent progress in these areas has directly exploited and explored connections to combinatorics and graph theory. One goal of this workshop is to push ahead on these and other topics that are in the purview of the yearlong program. Another goal is to highlight (a subset of) topics in coding and information theory which are especially ripe for collaboration between these communities. Examples of such topics include polar codes; new results on ReedMuller codes and their thresholds; coding for distributed storage and for DNA memories; coding for deletions and synchronization errors; storage capacity of graphs; zeroerror information theory; bounds on codes using semidefinite programming; tensorization in distributed source and channel coding; and applications of informationtheoretic methods in probability and combinatorics. All these topics have attracted a great deal of recent interest in the coding and information theory communities, and have rich connections to combinatorics and complexity which could benefit from further exploration and collaboration.
Participation: The workshop is open to participation by all interested researchers, subject to capacity. Click here to register.
Confirmed participants include:
Coorganizers of this workshop include Venkat Guruswami, Alexander Barg, Mary Wootters. More details about this event, including participants, will be updated soon. A list of lodging options convenient to the Center can also be found on our recommended lodgings page.
]]>Additive combinatorics is a mathematical area bordering on number theory, discrete mathematics, harmonic analysis and ergodic theory. It has achieved a number of successes in pure mathematics in the last two decades in quite diverse directions, such as:
Ideas and techniques from additive combinatorics have also had an impact in theoretical computer science, for example
The main focus of this workshop will be to bring together researchers involved in additive combinatorics, with a particular inclination towards the links with theoretical computer science. Thus it is expected that a major focus will be additive combinatorics on the boolean cube (Z/2Z)^n , which is the object where the exchange of ideas between pure additive combinatorics and theoretical computer science is most fruitful. Another major focus will be the study of pseudorandom phenomena in additive combinatorics, which has been an important contributor to modern methods of generating provably good randomness through deterministic methods. Other likely topics of discussion include the status of major open problems (the polynomial FreimanRuzsa conjecture, inverse theorems for the Gowers norms with bounds, explicit correlation bounds against low degree polynomials) as well as the impact of new methods such as the introduction of algebraic techniques by Croot–Pach–Lev and Ellenberg–Gijswijt.
Participation: The workshop is open to participation by all interested researchers, subject to capacity. Click here to register. A list of lodging options convenient to the Center can also be found on our recommended lodgings page.
Confirmed participants include:
Coorganizers of this workshop include Ben Green, Swastik Kopparty, Ryan O’Donnell, Tamar Ziegler.
]]>Extremal and Probabilistic Combinatorics are two of the most central branches of modern combinatorial theory. Extremal Combinatorics deals with problems of determining or estimating the maximum or minimum possible cardinality of a collection of finite objects satisfying certain requirements. Such problems are often related to other areas including Computer Science, Information Theory, Number Theory and Geometry. This branch of Combinatorics has developed spectacularly over the last few decades. Probabilistic Combinatorics can be described informally as a (very successful) hybrid between Combinatorics and Probability, whose main object of study is probability distributions on discrete structures.
There are many points of interaction between these fields. There are deep similarities in methodology. Both subjects are mostly asymptotic in nature. Quite a few important results from Extremal Combinatorics have been proven applying probabilistic methods, and vice versa. Such emerging subjects as Extremal Problems in Random Graphs or the theory of graph limits stand explicitly at the intersection of the two fields and indicate their natural symbiosis.
The symposia will focus on the interactions between the above areas. These topics include Extremal Problems for Graphs and Set Systems, Ramsey Theory, Combinatorial Number Theory, Combinatorial Geometry, Random Graphs, Probabilistic Methods and Graph Limits.
Participation: The workshop is open to participation by all interested researchers, subject to capacity. Click here to register.
Confirmed participants include:
Coorganizers of this workshop include Benny Sudakov and David Conlon. More details about this event, including participants, will be updated soon. A list of lodging options convenient to the Center can also be found on our recommended lodgings page.
]]>The main focus of the workshop is the application of algebraic method to study problems in combinatorics. In recent years there has been a large number of results in which the use of algebraic technique has resulted in significant improvements to long standing open problems. Such problems include the finite field Kakeya problem, the distinct distance problem of Erdos and, more recently, the capset problem. The workshop will include talks on all of the above mentioned problem as well as on recent development in related areas combining combinatorics and algebra.
Participation: The workshop is open to participation by all interested researchers, subject to capacity. Click here to register. A list of lodging options convenient to the Center can also be found on our recommended lodgings page.
Confirmed participants include:
Coorganizers of this workshop include Zeev Dvir, Larry Guth, and Shubhangi Saraf. More details about this event’s schedule will be updated soon.
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