Sunday | Monday | Tuesday | Wednesday | Thursday | Friday | Saturday |
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31 | 1 | 2 | 3 | 4 | 5 | 6 |

- 11:15am
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7 | 8 | 9 | 10 | 11 | 12 | 13 |

- 12:20pm
- 4pm
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14 | 15 | 16 | 17 | 18 | 19 | 20 |

- 11am
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28 | 29 | 30 | 1 | 2 | 3 | 4 |

### Geometric and Harmonic Analysis Workshop

Sunday, March 31st, 201912:00 AM - 11:59 PM

Storrs Campus

Schenker, McHugh, and Monteith Halls

https://gaha2019.math.uconn.edu/

Contact Information: Matthew Badger (matthew.badger@uconn.edu)
More

### Geometric and Harmonic Analysis Workshop

Sunday, March 31st, 201912:00 AM - 11:59 PM

Storrs Campus

Monteith

https://gaha2019.math.uconn.edu/

Contact Information: Matthew Badger
More

###
PDE and Differential Geometry Seminar

Title TBA

Speaker TBA.

Monday, April 1st, 201902:30 PM - 03:30 PM

Storrs Campus

MONT 214

TBA

Contact Information: Wang, lihan.wang@uconn.edu
More

###
Connecticut Logic Seminar

Coding overhead and the pitfalls of formalization

Benedict Eastaugh (Munich Center for Mathematical Philosophy)

Monday, April 1st, 201904:45 PM - 06:00 PM

Storrs Campus

MONT 214

Reverse mathematics purports to demonstrate what axioms are necessary in order to prove theorems of ordinary mathematics: real, complex, and functional analysis, countable algebra, infinitary combinatorics. This involves formalizing the basic notions of these fields in the language of second order arithmetic, thus limiting what can be formalized to mathematical objects which admit of countable representations or codes. That a formalized counterpart of an ordinary mathematical theorem such as the Heine-Borel covering theorem implies the set existence axiom WKL (weak Konig’s lemma) is usually glossed as “WKL is necessary to prove the Heine-Borel covering theorem”. But to justify the use of this gloss, and indeed the central claim of reverse mathematics to be determining the axioms necessary to prove ordinary mathematical theorems, the coding involved in the formalization of these theorems in second order arithmetic must satisfy certain conditions that ensure their faithfulness. In particular, the coding should not affect what axioms are necessary to prove a given theorem. In this paper we study the coding overhead of additional principles that are necessary to prove the extensional correctness of a coding, and argue that several codings used in reverse mathematical practice fail to be faithful when evaluated in the context of specific theorems from analysis and topology.

Contact Information: Reed Solomon, david.solomon@uconn.edu
More

###
Algebra Seminar

Measures of irrationality for algebraic varieties

Brooke Ullery (Harvard University)

Wednesday, April 3rd, 201911:15 AM - 12:05 PM

Storrs Campus

Monteith, 313

A smooth algebraic curve is said to be rational if it is isomorphic to P^1, the projective line. More generally, the gonality of a smooth projective curve is the smallest degree of a map from the curve to the projective line. The intuition is that the higher the gonality, the further the curve is from being rational. A classical theorem of Noether says that if C is a smooth plane curve of degree d, then the gonality of C is d-1, and it is obtained by projecting away from a point on the curve. A natural question is: does Noether's theorem generalize in some way to curves in larger projective spaces? What about to higher dimensional varieties? We will explore these questions, focusing on the examples of hypersurfaces and, more generally, complete intersections in projective space.

Contact Information: Mihai Fulger, mihai.fulger@uconn.edu
More

###
Mathematical Finance and Applied Probability Seminar

Mean Field Systems for solving Free-Boundary problems: from Finance to Neuroscience and Physics

Sergey Nadtochiy (IIT)

Wednesday, April 3rd, 201904:00 PM - 05:00 PM

Storrs Campus

MONT 313

This talk is concerned with the recent advances in the study of particle systems with threshold-type interaction. Such systems appear naturally in the mathematical models for neuron cells, supercooled liquids, computer and credit networks, etc. In particular, our recent work shows how to use these particle systems in order to solve the supercooled Stefan PDE. The latter is a free-boundary problem which describes the process of freezing of a supercooled liquid, and whose well-posedness has been an open question for the last 50 years. We prove the well-posedness and provide a complete description of such solutions in one space dimension, by relating the temperature distribution in the liquid to the regularity of the interface between the solid and liquid states. These results provide a methodology for establishing the well-posedness and describing the structure of other mean-filed systems with threshold-type interaction (and of the associated free-boundary problems). This is a joint work with F. Delarue and M. Shkolnikov.

Contact Information: Oleksii Mostovyi
More

###
Math Club

Numerical differentiation: some lessons from blast calculations

Jeffrey Connors (UConn)

Wednesday, April 3rd, 201905:45 PM - 06:35 PM

Storrs Campus

Monteith 321

Computer simulations of natural phenomena often require the calculation of derivatives for functions when the function values are only known approximately at some specific points and the standard differentiation rules from calculus are not applicable. The derivative can only be approximated using the available data. Such a technique is called ``numerical differentiation'', and there are infinitely many ways to do it.

In the early days of computing, scientists learned right away that different algorithms for numerical differentiation can yield very different results for simulations. In fact, it is not uncommon for methods that seem intuitive to fail completely. There is a classic test problem that comes from computing the shock wave for an explosion. We will study numerical differentiation for this problem and another related problem to learn some things about what works, what doesn't and why.

In the early days of computing, scientists learned right away that different algorithms for numerical differentiation can yield very different results for simulations. In fact, it is not uncommon for methods that seem intuitive to fail completely. There is a classic test problem that comes from computing the shock wave for an explosion. We will study numerical differentiation for this problem and another related problem to learn some things about what works, what doesn't and why.

Contact Information: Keith Conrad (kconrad@math.uconn.edu)
More

###
S.I.G.M.A. Seminar

A Brief History and Introduction of Finite Element Methods

Kyle Allaire

Friday, April 5th, 201912:20 PM - 01:10 PM

Storrs Campus

MONT 214

The Finite Element Method (FEM) was popularized by the engineering community in early 1900's Russia. Since then, it has become the standard numerical method for solving problems in heat transfer, fluid flow, and structural mechanics. In this talk, we will the introduce the method on Poisson's Equation in order to construct an approximate solution.

Contact Information: Lisa Naples
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### Logic Colloquium: Marianna Antonutti Marfori (MCMP)

Friday, April 5th, 201902:30 PM - 04:00 PM

Storrs Campus

Humanities Institute seminar room, Babbidge Library, 4th Floor

Join us for a talk by Marianna Antonutti Marfori (Munich, MCMP) in the Logic Colloquium!

https://logic.uconn.edu/

https://logic.uconn.edu/

Contact Information: https://logic.uconn.edu/about/
More

###
Analysis Learning Seminar

Title: The Gaussian limit of Spherical integrals and Polynomials on High Dimensional Spheres

Amy Peterson

Friday, April 5th, 201903:30 PM - 04:30 PM

Storrs Campus

MONT 313

Abstract: We show in detail that the limit of spherical surface integrals taken over slices of a high dimensional sphere is a Gaussian integral on an affine plane of finite codimension in infinite dimensional space. We then utilize these ideas to show that a natural class of orthogonal polynomials on high dimensional spheres limit to Hermite polynomials

Contact Information: Murat Akman and Vyron Vellis
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### Logic Group workshop: Conditionals

Saturday, April 6th, 201912:00 AM - 11:59 PM

Storrs Campus

Oak 112

UConn Logic Group Workshop, April 6-7, 2019

https://meaning.linguistics.uconn.edu/special-events/

“If" by any other name

It is a relatively recent development that research on conditionals is taking a deep and sustained interest in the full range of linguistic markers, their interactions with each other and with other linguistic categories, and the ways in which they drive and constrain the interpretation of the sentences they occur in. Tense and aspect is an area where such attention has already borne fruit; to a lesser extent, we may mention conditional connectives and pro-forms (especially thanks to works like Iatridou 2000 and Iatridou & Embick 1993). More recently, there seems to be a growing interest in two things: on the one hand, more varied aspects of formal marking of conditionals and the ways in which different grammatical categories may be recruited to encode conditional meaning (including aspect, different types of connectives, conjunctions, etc.); on the other hand, the appearance of these markers in other linguistic contexts (like optatives, complement clauses, temporal clauses, interrogatives, etc.).

Speakers at the workshop include: Kai von Fintel, Sabine Iatridou, Teruyuki Mizuno, Hiromune Oda, Paolo Santorio, Will Starr, Una Stojnić, and Muyi Yang

See the full program here:

https://meaning.linguistics.uconn.edu/special-events/

https://meaning.linguistics.uconn.edu/special-events/

“If" by any other name

It is a relatively recent development that research on conditionals is taking a deep and sustained interest in the full range of linguistic markers, their interactions with each other and with other linguistic categories, and the ways in which they drive and constrain the interpretation of the sentences they occur in. Tense and aspect is an area where such attention has already borne fruit; to a lesser extent, we may mention conditional connectives and pro-forms (especially thanks to works like Iatridou 2000 and Iatridou & Embick 1993). More recently, there seems to be a growing interest in two things: on the one hand, more varied aspects of formal marking of conditionals and the ways in which different grammatical categories may be recruited to encode conditional meaning (including aspect, different types of connectives, conjunctions, etc.); on the other hand, the appearance of these markers in other linguistic contexts (like optatives, complement clauses, temporal clauses, interrogatives, etc.).

Speakers at the workshop include: Kai von Fintel, Sabine Iatridou, Teruyuki Mizuno, Hiromune Oda, Paolo Santorio, Will Starr, Una Stojnić, and Muyi Yang

See the full program here:

https://meaning.linguistics.uconn.edu/special-events/

Contact Information: magdalena.kaufmann@uconn.edu
More

### Logic Group workshop: Conditionals

Sunday, April 7th, 201912:00 AM - 11:59 PM

Storrs Campus

Oak 112

https://meaning.linguistics.uconn.edu/special-events/

“If" by any other name

It is a relatively recent development that research on conditionals is taking a deep and sustained interest in the full range of linguistic markers, their interactions with each other and with other linguistic categories, and the ways in which they drive and constrain the interpretation of the sentences they occur in. Tense and aspect is an area where such attention has already borne fruit; to a lesser extent, we may mention conditional connectives and pro-forms (especially thanks to works like Iatridou 2000 and Iatridou & Embick 1993). More recently, there seems to be a growing interest in two things: on the one hand, more varied aspects of formal marking of conditionals and the ways in which different grammatical categories may be recruited to encode conditional meaning (including aspect, different types of connectives, conjunctions, etc.); on the other hand, the appearance of these markers in other linguistic contexts (like optatives, complement clauses, temporal clauses, interrogatives, etc.).

Speakers at the workshop include: Kai von Fintel, Sabine Iatridou, Teruyuki Mizuno, Hiromune Oda, Paolo Santorio, Will Starr, Una Stojnić, and Muyi Yang

See the full program here:

https://meaning.linguistics.uconn.edu/special-events/

Contact Information: magdalena.kaufmann@uconn.edu
More

###
PDE and Differential Geometry Seminar

On Gaussian curvature equation with prescribed nonpositive curvature

Zhou, Feng

Eastern China Normal University

Monday, April 8th, 201902:30 PM - 03:30 PM

Storrs Campus

MONT 214

We present some results concerning the solutions of

$$

\Delta u +K(x) e^{2u}=0 \quad{\rm in}\;\; \mathbb{R}^2

$$

with $$K\leq 0$$.

$$

\Delta u +K(x) e^{2u}=0 \quad{\rm in}\;\; \mathbb{R}^2

$$

with $$K\leq 0$$.

Contact Information: Wang, lihan.wang@uconn.edu
More

###
Algebra Seminar

Mutation of type D friezes

Ana Garcia Elsener (University of Graz)

Wednesday, April 10th, 201911:15 AM - 12:05 PM

Storrs Campus

Monteith, 313

We provide a combinatorial formula for the entries in a frieze of type D after mutation. The two main ingredients in the proof include a certain transformation of a type D frieze into a sub pattern of a frieze of type A, and the mutation formula for type A friezes recently described by K. Baur et al. This is all in joint work with K. Serhiyenko.

Contact Information: Mihai Fulger, (734)883-5904, mihai.fulger@uconn.edu
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###
S.I.G.M.A. Seminar

Introduction to Finite Elements and the Discrete Green's Function

Andrew Miller

Wednesday, April 10th, 201912:20 PM - 01:10 PM

Storrs Campus

MONT 214

In this talk we will give an introduction to the Finite Element Method (FEM) for solving elliptic partial differential equations and discuss some advantages to FEM and why we want to use it. We will then introduce the discrete Green’s function and explore its implications on proving a discrete Harnack inequality as well as compare differences in two dimensions versus three dimensions.

Contact Information: Lisa Naples
More

###
Mathematical Finance and Applied Probability Seminar

Pricing without martingale measure

Laurence Carassus (ESILV)

Wednesday, April 10th, 201904:00 PM - 05:00 PM

Storrs Campus

MONT 313

For several decades, the no-arbitrage (NA) condition and the martingale measures have played a major role in the financial asset's pricing theory. Here, we propose a new approach based on convex duality instead of martingale measures duality: our prices will be expressed using Fenchel conjugate and bi-conjugate.

This naturally leads to a weak condition of (NA) called Absence of Immediate Profit (AIP). It asserts that the price of the zero claim should be zero or equivalently that the super-hedging cost of some call option should be non-negative. We propose several characterizations of the (AIP) condition and also study the relation with (NA) and a stronger notion of (AIP) linked to the no-free lunch condition. We show in a one step model that under (AIP) the super-hedging cost is just the payoff's concave envelop. In the multiple-period case, for a particular, but still general setup, we propose a recursive scheme for the computation of a the super-hedging cost of a convex option. We also give some promising numerical illustrations. Joint work with Julien Baptiste and Emmanuel Lépinette.

This naturally leads to a weak condition of (NA) called Absence of Immediate Profit (AIP). It asserts that the price of the zero claim should be zero or equivalently that the super-hedging cost of some call option should be non-negative. We propose several characterizations of the (AIP) condition and also study the relation with (NA) and a stronger notion of (AIP) linked to the no-free lunch condition. We show in a one step model that under (AIP) the super-hedging cost is just the payoff's concave envelop. In the multiple-period case, for a particular, but still general setup, we propose a recursive scheme for the computation of a the super-hedging cost of a convex option. We also give some promising numerical illustrations. Joint work with Julien Baptiste and Emmanuel Lépinette.

Contact Information: Oleksii Mostovyi
More

### TBA

Wednesday, April 10th, 201904:00 PM - 05:00 PM

Storrs Campus

MONT 313

Laurence Carassus's talk

Contact Information: Oleksii Mostovyi
More

###
Math Club

The Projective Plane and Projective Space

Mihai Fulger (UConn)

Wednesday, April 10th, 201905:45 PM - 06:35 PM

Storrs Campus

Monteith 321

For every real number t, draw the line L(t) through (0,1) and (t,0). When you take your t for a walk on the x-axis to infinity (positive or negative), the line L(t) gets closer and closer to the line y=1, which is parallel to the x-axis. This supports the idea that parallel lines "meet at infinity". But what is this infinity? What if you want to "go to there''? Then projective spaces are your thing.

The projective plane enlarges the real plane by adding one point ("at infinity") for each line direction. It gives a new way of understanding asymptotes. It can be used to reduce results in Euclidean geometry about incidence of lines and collinearity to the easier case where many of the lines are parallel.

Note: Free pizza and drinks!

The projective plane enlarges the real plane by adding one point ("at infinity") for each line direction. It gives a new way of understanding asymptotes. It can be used to reduce results in Euclidean geometry about incidence of lines and collinearity to the easier case where many of the lines are parallel.

Note: Free pizza and drinks!

Contact Information: Keith Conrad (kconrad@math.uconn.edu)
More

###
Analysis and Probability Seminar

Boundary value problems and Fatou theorems for elliptic systems in the upper half-space

Jose Maria Martell (Institute of Mathematical Sciences, Madrid)

Thursday, April 11th, 201911:00 AM - 12:00 PM

Storrs Campus

MONT 214

Abstract: In this talk we will consider the Dirichlet problem in the upper half-space for second-order, homogeneous, elliptic systems, with constant complex coefficients, such as the Laplacian or the Lam\'e system of elasticity. The goal is to show that the Dirichlet problem is well-posed with data in Lebesgue spaces (with and without weights), Köte function spaces, BMO, VMO, Hölder spaces, etc. By the work of S. Agmon, A. Douglis, and L. Nirenberg, there exists a Poisson kernel associated with each of the previous operators which can be used to construct solutions in a quite general class of functions containing all the previous spaces. Uniqueness is more delicate and the main idea consists in establishing Fatou type results on which one can recover null solutions from their nontangential boundary traces using the associated Poisson kernel.

Contact Information: Scott Zimmerman, scott.zimmerman@uconn.edu
More

###
Mathematics Colloquium

Geometric Partial Differential Equations from M Theory

Duong Phong (Columbia University)

Thursday, April 11th, 201904:00 PM - 05:00 PM

Storrs Campus

MONT 214

Since the mid 1990’s, the leading candidate for a unified theory of all fundamental physical interactions including gravity has been M Theory. A full formulation of M Theory is still not available, and it is only understood through its limits in certain regimes, which are either one of five 10-dimensional string theories, or 11-dimensional supergravity. The equations for these theories are mathematically interesting in themselves, as they reflect, either directly or indirectly, the presence of supersymmetry. We discuss recent progresses and open problems about two of these theories, namely supersymmetric compactifications of the heterotic string and of 11-dimensional supergravity. This is based on joint work of the speaker with Sebastien Picard and Xiangwen Zhang, and with Teng Fei and Bin Guo.

Contact Information: Ovidiu Munteanu
More

###
Connecticut Logic Seminar

Encodable by thin sets

Peter Cholak (Notre Dame)

Thursday, April 11th, 201904:30 PM - 05:45 PM

Storrs Campus

Exley Science Center 121, Wesleyan University

Let $$c$$ be a coloring of $$n$$-tuples (of $$\omega$$) by finitely many colors. For $$l$$ less than the number of colors, a set $$T$$ is $$l$$-thin iff $$c$$ uses at most $$l$$ colors to color all the $$n$$-tuples from $$T$$. We say a set $$S$$ is $$RT^n_{< \infty,l}$$-encodable iff there is a coloring $$c$$ as above such that every $$l$$-thin set computes $$S$$. Wang and others showed that when $$l$$ is "big'' only the computable sets are $$RT^n_{< \infty,l}$$-encodable. Dorais, Dzhafarov, Hirst, Mileti, and Shafer showed that the hyperarithmetic sets are $$RT^n_{< \infty,l}$$-encodable for $$l<2^{n-1}$$. Cholak and Patey showed that the arithmetic sets are $$RT^n_{< \infty,l}$$-encodable for "medium'' $$l$$. In the talk we will provide exact definitions of "medium'' and "big''. What is also of interest is the role that cone avoidance plays in determining "medium'' and "big''. This is joint work with Ludovic Patey.

Contact Information: Reed Solomon, david.solomon@uconn.edu
More

###
S.I.G.M.A. Seminar

Informational Meeting for Teaching Assistants

Friday, April 12th, 201912:20 PM - 01:00 PM

Storrs Campus

MONT 214

TBA

Contact Information: Lisa Naples
More

###
Analysis and Probability Seminar

Lipschitz differentiability, embeddings, and rigidity for group actions

Guy David (Ball State University)

Friday, April 12th, 201901:30 PM - 02:30 PM

Storrs Campus

MONT 313

Abstract: We discuss a class of metric spaces that, despite being non-Euclidean, support a first-order calculus for Lipschitz functions developed by Cheeger. After introducing these spaces, we will survey some of their embedding properties and explain a theorem of the speaker and Kyle Kinneberg concerning embeddings in Carnot groups. Then we will explain an application of this last result to a problem on group actions in hyperbolic geometry.

Contact Information: Scott Zimmerman, scott.zimmerman@uconn.edu
More

### Logic Colloquium: Branden Fitelson (Northeastern)

Friday, April 12th, 201902:30 PM - 04:00 PM

Storrs Campus

Humanities Institute seminar room, Babbidge Library, 4th Floor

Join us for a talk by Branden Fitelson (Northeastern) in the Logic Colloquium!

https://logic.uconn.edu/

Branden Fitelson (Northeastern)

How to model the probabilities of conditionals

David Lewis (and others) have famously argued against Adams’s Thesis (that the probability of a conditional is the conditional probability of its consequent, given it antecedent) by proving various “triviality results.” In this paper, I argue for two theses — one negative and one positive. The negative thesis is that the “triviality results” do not support the rejection of Adams’s Thesis, because Lewisian “triviality based” arguments against Adams’s Thesis rest on an implausibly strong understanding of what it takes for some credal constraint to be a rational requirement (an understanding which Lewis himself later abandoned in other contexts). The positive thesis is that there is a simple (and plausible) way of modeling the probabilities of conditionals, which (a) obeys Adams’s Thesis, and (b) avoids all of the existing triviality results.

https://logic.uconn.edu/

Branden Fitelson (Northeastern)

How to model the probabilities of conditionals

David Lewis (and others) have famously argued against Adams’s Thesis (that the probability of a conditional is the conditional probability of its consequent, given it antecedent) by proving various “triviality results.” In this paper, I argue for two theses — one negative and one positive. The negative thesis is that the “triviality results” do not support the rejection of Adams’s Thesis, because Lewisian “triviality based” arguments against Adams’s Thesis rest on an implausibly strong understanding of what it takes for some credal constraint to be a rational requirement (an understanding which Lewis himself later abandoned in other contexts). The positive thesis is that there is a simple (and plausible) way of modeling the probabilities of conditionals, which (a) obeys Adams’s Thesis, and (b) avoids all of the existing triviality results.

Contact Information: https://logic.uconn.edu/
More

###
Analysis Learning Seminar

Title: Introduction to Hardy-Sobolev-Maz’ya inequalities and Hardy-Adams inequalities

Jungang Li

Friday, April 12th, 201903:30 PM - 04:30 PM

Storrs Campus

MONT 313

Abstract: In this talk, we will first talk about Hardy-Sobolev-Maz’ya inequalities on upper half spaces. The proof of higher order Hardy-Sobolev-Maz’ya inequalities, which is done by G. Lu and Q. Yang, relies on the Fourier analysis on the hyperbolic space. This new idea is then applied to study other sharp geometric inequalities. We will also introduce the Hardy-Adams inequality, which is the borderline case of the Hardy-Sobolev-Maz’ya inequality.

Contact Information: Murat Akman and Vyron Vellis
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### American Mathematical Society Meeting

Saturday, April 13th, 201912:00 AM - 11:59 PM

Storrs Campus

Main Building

AMS Sectional Meeting hosted by UConn

http://www.ams.org/meetings/sectional/2265_special.html

http://www.ams.org/meetings/sectional/2265_special.html

Contact Information: Ambar Sengupta
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### American Mathematical Society Meeting

Sunday, April 14th, 201912:00 AM - 11:59 PM

Hartford Campus

Main Building

AMS Sectional Meeting hosted by UConn Mathematics Department

http://www.ams.org/meetings/sectional/2265_special.html

http://www.ams.org/meetings/sectional/2265_special.html

Contact Information: Ambar Sengupta
More

###
Actuarial Science Seminar

Predictive Actuarial Analytics Using Tree-Based Models

Zhiyu Quan

Monday, April 15th, 201911:00 AM - 12:00 PM

Storrs Campus

MONT 214

Because of its many advantages, the use of tree-based models has become an increasingly

popular alternative predictive tool for building classification and regression models. Innovations to the original methods, such as random forests and gradient boosting, have further improved

the capabilities of using tree-based models as a predictive model. Quan et al. (2018) examined the performance of tree-based models for the valuation of the guarantees embedded in variable

annuities. We found that tree-based models are generally very efficient in producing more

accurate predictions and the gradient boosting ensemble method is considered the most superior. Quan and Valdez (2018) applied multivariate tree models to multi-line insurance claims data with correlated responses. We were able to capture the inherent relationship among the response variables and improved marginal predictive accuracy. We propose to use tree-based models with a hybrid structure as an alternative approach to the Tweedie Generalized Linear Model (GLM). This hybrid structure captures the benefits of tuning hyperparameters at each step of the algorithm thereby allowing for an improved prediction accuracy. We examined the performance

of this model vis-à-vis the Tweedie GLM using the LGPIF and simulated datasets. Our empirical results indicate that this hybrid tree-based model produces more accurate predictions without loss of intuitive interpretation.

popular alternative predictive tool for building classification and regression models. Innovations to the original methods, such as random forests and gradient boosting, have further improved

the capabilities of using tree-based models as a predictive model. Quan et al. (2018) examined the performance of tree-based models for the valuation of the guarantees embedded in variable

annuities. We found that tree-based models are generally very efficient in producing more

accurate predictions and the gradient boosting ensemble method is considered the most superior. Quan and Valdez (2018) applied multivariate tree models to multi-line insurance claims data with correlated responses. We were able to capture the inherent relationship among the response variables and improved marginal predictive accuracy. We propose to use tree-based models with a hybrid structure as an alternative approach to the Tweedie Generalized Linear Model (GLM). This hybrid structure captures the benefits of tuning hyperparameters at each step of the algorithm thereby allowing for an improved prediction accuracy. We examined the performance

of this model vis-à-vis the Tweedie GLM using the LGPIF and simulated datasets. Our empirical results indicate that this hybrid tree-based model produces more accurate predictions without loss of intuitive interpretation.

Contact Information: Guojun Gan
More

###
Analysis and Probability Seminar

Large-N Segal-Bargmann transform and eigenvalues of random matrices

Brian C. Hall (University of Notre Dame)

Monday, April 15th, 201901:30 PM - 02:30 PM

Storrs Campus

MONT 313

Abstract: I will describe a generalized Segal-Bargmann transform for compact Lie groups. The transform is a unitary map of Hilbert space of functions on a compact Lie group (for example, the unitary group $$U(N)$$) to a Hilbert space of holomorphic functions on the associated complex group (for example, the general linear group $$GL(N;\mathbb{C})$$). I will then discuss the large-$$N$$ limit of this construction. Finally, I will describe an application of these constructions to random matrix theory: for a certain class of random matrices in $$GL(N;\mathbb{C})$$, the transform allows us to identify the region in the complex plane into which the eigenvalues cluster.

The talk will be self-contained and will include lots of pictures. It is a prequel to the talk I will give at the AMS meeting in Hartford on April 13.

The talk will be self-contained and will include lots of pictures. It is a prequel to the talk I will give at the AMS meeting in Hartford on April 13.

Contact Information: Scott Zimmerman, scott.zimmerman@uconn.edu
More

###
Algebra Seminar

Cohen-Lenstra heuristics and counting number fields

Jack Klys (University of Calgary)

Tuesday, April 16th, 201911:00 AM - 11:50 AM

Storrs Campus

Monteith, 214

We will discuss the Cohen-Lenstra heuristics, both in the classical and non-abelian setting. In particular we will make the connection between these heuristics and the problem of counting extensions of quadratic fields with fixed Galois groups, and when knowledge of the latter implies such heuristics. Finally we will discuss our recent work on the non-abelian case and counting unramified 2-group extensions of quadratic fields.

Contact Information: Mihai Fulger, mihai.fulger@uconn.edu
More

###
Analysis and Probability Seminar

Translation invariant operators in $$L^p$$

Piotr Hajlasz (University of Pittsburgh)

Tuesday, April 16th, 201902:00 PM - 03:00 PM

Storrs Campus

MONT 313

We say that a bounded linear operator $$T:L^p(\mathbb{R}^n)\to L^q(\mathbb{R}^n)$$ is translation invariant if

$$T(\tau_y f)=\tau_y(Tf)$$ for all $$f\in L^p(\mathbb{R}^n)$$ and all $$y\in\mathbb{R}^n$$,

where $$(\tau_y f)(x)=f(x+y)$$.

The following result of Hormander plays a fundamental role in harmonic analysis since it applies to all convolution type operators.

Theorem (Hormander 1960). If $$T:L^p(\mathbb{R}^n)\to L^q(\mathbb{R}^n)$$, $$1\leq p

$$T(\tau_y f)=\tau_y(Tf)$$ for all $$f\in L^p(\mathbb{R}^n)$$ and all $$y\in\mathbb{R}^n$$,

where $$(\tau_y f)(x)=f(x+y)$$.

The following result of Hormander plays a fundamental role in harmonic analysis since it applies to all convolution type operators.

Theorem (Hormander 1960). If $$T:L^p(\mathbb{R}^n)\to L^q(\mathbb{R}^n)$$, $$1\leq p

Contact Information: Scott Zimmerman, scott.zimmerman@uconn.edu
More

###
Mathematical Finance and Applied Probability Seminar

Adaptive Robust Control Under Model Uncertainty

Igor Cialenco (Illinois Institute of Technology)

Wednesday, April 17th, 201904:00 PM - 05:00 PM

Storrs Campus

MONT 313

We propose a new methodology, called adaptive robust control, for solving a discrete-time Markovian control problem subject to Knightian uncertainty. We apply the general framework to a financial hedging problem where the uncertainty comes from the fact that the true law of the underlying model is only known to belong to a certain family of probability laws. We develop a learning algorithm that reduces the model uncertainty through progressive learning about the unknown system. One of the pillars in the proposed methodology is the recursive construction of the confidence sets for the unknown parameter, which, in particular, allows to establish the Bellman system of equations corresponding to the original stochastic control problem.

Contact Information: Oleksii Mostovyi
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Math Club

The Isoperimetric Inequality

Masha Gordina (UConn)

Wednesday, April 17th, 201905:45 PM - 06:35 PM

Storrs Campus

Monteith 321

The classical isoperimetric problem asks: among all figures with a given perimeter, which one encloses the greatest area? There are many different proofs of the isoperimetric inequality and many jokes about the authors of these proofs. We will review different tools that can be used to prove such an inequality (plane geometry, calculus of variations and maybe even Fourier series), and if time permits we'll describe how this type of problem is still an active area of research in analysis and geometry.

Note: Free pizza and drinks!

Note: Free pizza and drinks!

Contact Information: Keith Conrad (kconrad@math.uconn.edu)
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Analysis and Probability Seminar

Non-local curvatures and the geometry of measures

Max Goering (University of Washington)

Thursday, April 18th, 201904:00 PM - 05:00 PM

Storrs Campus

MONT 313

Abstract: Uniformly rectifiable sets have played a fundamental role in the development of harmonic analysis in on-smooth settings. In one-dimension the 1996 paper of Mattila, Melnikov, and Verdera first made use of the classical Menger curvature to provide a new proof that Uniformly Rectifiable (UR) curves are characterized by the $$L^{2}$$-boundedness of the Cauchy integral operator in the plane. This opened the floodgates in relating the analytic and geometric properties of one-dimensional sets and measures. Higher-dimensional analogs of the Menger curvature were much sought after until Farag showed that there was no algebraic generalization of the Menger curvature which could relate to the $$L^{2}$$-boundedness of the Riesz kernels. Nonetheless, Lerman and Whitehouse proved that geometrically motivated generalizations can be used to characterize uniformly rectifiable sets in real-separable Hilbert spaces. In this talk, we discuss a new characterization of the wilder class of rectifiable measures in terms of these types of discrete curvatures.

Contact Information: Scott Zimmerman, scott.zimmerman@uconn.edu
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### UConn Math Distinguished Lecture: Mathematical ideas in public key cryptography, by Jill Pipher

Friday, April 19th, 201903:30 PM - 05:00 PM

Storrs Campus

Schenker Lecture Hall

First UConn Mathematics Distinguished Lecture. Speaker: Jill Pipher

https://www.math.brown.edu/~jpipher/

Mathematical ideas in public key cryptography

https://www.math.brown.edu/~jpipher/

Mathematical ideas in public key cryptography

Contact Information: Ambar Sengupta
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Algebra Seminar

Partial cluster-tilted algebras

Amit Shah (University of Leeds)

Monday, April 22nd, 201904:00 AM - 04:50 PM

Storrs Campus

Monteith, 313

A partial cluster-tilted algebra is the endomorphism ring of a rigid object in a cluster category, and is a generalisation of a cluster-tilted algebra. Unlike cluster-tilted algebras, partial cluster-tilted algebras do not necessarily have global dimension 0, 1 or infinity. Indeed, for each non-negative integer n I will show how to construct a partial cluster-tilted algebra (coming from a cluster category of Dynkin type A) of global dimension n. In studying these algebras, I have been interested in their Auslander-Reiten theory and how it is induced from that of the corresponding cluster category. I will report on the progress so far in this direction and give some idea of other approaches that might be fruitful.

Contact Information: Mihai Fulger, mihai.fulger@uconn.edu
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Analysis Learning Seminar

Title: Global Dynamics and Boundedness of Discrete Population Models

David McArdle

Monday, April 22nd, 201902:30 PM - 03:30 PM

Storrs Campus

MONT 214

Abstract: The theory of difference equations will be introduced and global dynamic results will be presented for several 2-dimensional models originating from biological contexts. In particular, we will consider the system of difference equations

xn+1 = (αxn)/(1+βyn),

yn+1 = (γxnyn)/(xn + δyn), n=0,1,2,...

where α, β, γ, δ, x0, y0 are positive real numbers. This system was formulated by P. H. Leslie in 1948 as a model of host-parasite interactions. We will establish boundedness and persistence results along with global attractivity results for various parameter regions.

xn+1 = (αxn)/(1+βyn),

yn+1 = (γxnyn)/(xn + δyn), n=0,1,2,...

where α, β, γ, δ, x0, y0 are positive real numbers. This system was formulated by P. H. Leslie in 1948 as a model of host-parasite interactions. We will establish boundedness and persistence results along with global attractivity results for various parameter regions.

Contact Information: Murat Akman and Vyron Vellis
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Math Club

Preparing for math grad school

Panel discussion

Wednesday, April 24th, 201905:45 PM - 06:35 PM

Storrs Campus

Monteith 321

If you are considering graduate school in mathematics or related areas after college, come to this panel discussion where you will hear from members of the UConn math department about their experiences planning for and applying to graduate school. The discussion will then be opened to answer your questions. A packet containing a suggested reading list and some general advice will be distributed too.

Note: Free pizza and drinks!

Note: Free pizza and drinks!

Contact Information: Keith Conrad
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S.I.G.M.A Seminar

How to Draw a Graph

Donald Sheehy

Friday, April 26th, 201912:20 PM - 01:10 PM

Storrs Campus

MONT 214

I will discuss a classic result of Tutte from 1963 that shows an elegant connection between graph theory, physics, geometry, and linear algebra. Tutte addressed the problem of how to draw a planar graph (a collection of vertices and edges that can be drawn without crossing edges in the plane) so that every edge is a straight line and the resulting faces are all convex polygons.

With the advantage of hindsight, I will also show how this result has influenced many modern ideas in graph theory and graph drawing. Despite covering a lot of ground, the talk should be widely accessible.

With the advantage of hindsight, I will also show how this result has influenced many modern ideas in graph theory and graph drawing. Despite covering a lot of ground, the talk should be widely accessible.

Contact Information: Lisa Naples (lisa.naples@uconn.edu)
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Analysis and Probability Seminar

Non-commutative regular conditional probability

Arthur Parzygnat (UConn)

Friday, April 26th, 201901:30 PM - 02:30 PM

Storrs Campus

MONT 313

Abstract: By diagrammatically reformulating the notion of a regular conditional probability (RCP), we are able to abstract the idea to a variety of categories. However, the interpretation of the RCP may be different from our usual probabilistic intuition and typically depends on the specific category. We will specialize this abstraction of a RCP to the category of finite-dimensional $$C^*$$-algebras and completely positive maps, a setting for non-commutative spaces and quantum information theory. Our main result is a necessary and sufficient condition for the existence and uniqueness of non-commutative RCPs. As a corollary, we reproduce a familiar theorem in the commutative (classical) setting. This talk should be accessible to a wide (mathematically-minded) audience. This is joint work with Benjamin Russo at SUNY Farmingdale.

Contact Information: Scott Zimmerman, scott.zimmerman@uconn.edu
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### Logic Colloquium: Adrian Brasoveanu (UC Santa Cruz)

Friday, April 26th, 201902:30 PM - 04:00 PM

Storrs Campus

Humanities Institute seminar room, Babbidge Library, 4th Floor

Join us for a talk by Adrian Brasoveanu (UC Santa Cruz) in the Logic Colloquium!

"Computational Cognitive Modeling for Syntax and Semantics"

Adrian Brasoveanu (joint work with Jakub Dotlacil)

Abstract: I introduce a typical experimental task in psycholinguistics -- self-paced reading -- and show how to build end-to-end simulations of a human participant in such an experiment; end-to-end means that we model visual and motor processes together with specifically linguistic processes (syntactic and semantic parsing) in a complete model of the experimental task. The model embeds theoretical hypotheses about linguistic representations and parsing processes in an independently motivated cognitive architecture (ACT-R). In turn, the resulting cognitive models can be embedded in Bayesian models to fit them to experimental data, estimate their parameters and perform quantitative model comparison for qualitative theories.

All welcome!

https://logic.uconn.edu/

"Computational Cognitive Modeling for Syntax and Semantics"

Adrian Brasoveanu (joint work with Jakub Dotlacil)

Abstract: I introduce a typical experimental task in psycholinguistics -- self-paced reading -- and show how to build end-to-end simulations of a human participant in such an experiment; end-to-end means that we model visual and motor processes together with specifically linguistic processes (syntactic and semantic parsing) in a complete model of the experimental task. The model embeds theoretical hypotheses about linguistic representations and parsing processes in an independently motivated cognitive architecture (ACT-R). In turn, the resulting cognitive models can be embedded in Bayesian models to fit them to experimental data, estimate their parameters and perform quantitative model comparison for qualitative theories.

All welcome!

https://logic.uconn.edu/

Contact Information: https://logic.uconn.edu/about/
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### Math Department Awards Day Ceremony

Friday, April 26th, 201903:30 PM - 05:00 PM

Storrs Campus

SCHN 151

All are invited to celebrate our undergraduate and graduate students! Ceremony will be followed by a talk from Dr. Steven Miller (Williams College), entitled "The German Tank Problem: Math/Stats At War!"

Abstract: During World War II the German army used tanks to devastating advantage. The Allies needed accurate estimates of their tank production and deployment. They used two approaches to find these values: spies, and statistics. In this talk we describe the statistical approach and its generalization. Assuming the tanks are labeled consecutively starting at 1, if we observe $k$ serial numbers from an unknown number $N$ of tanks, with the maximum observed value $m$, what is the best estimate for $N$? This is now known as the German Tank Problem, and is a terrific example of the applicability of mathematics and statistics in the real world. We quickly review some needed combinatorial identities (which is why we are able to obtain clean, closed form expressions), give the proof for the standard problem, discuss the generalization, and show how if we were unable to do the algebra we could guess the formula by an application of linear regression, thus highlighting its power and applicability. Most of the talk only uses basic algebra and elementary knowledge of WWII.

Abstract: During World War II the German army used tanks to devastating advantage. The Allies needed accurate estimates of their tank production and deployment. They used two approaches to find these values: spies, and statistics. In this talk we describe the statistical approach and its generalization. Assuming the tanks are labeled consecutively starting at 1, if we observe $k$ serial numbers from an unknown number $N$ of tanks, with the maximum observed value $m$, what is the best estimate for $N$? This is now known as the German Tank Problem, and is a terrific example of the applicability of mathematics and statistics in the real world. We quickly review some needed combinatorial identities (which is why we are able to obtain clean, closed form expressions), give the proof for the standard problem, discuss the generalization, and show how if we were unable to do the algebra we could guess the formula by an application of linear regression, thus highlighting its power and applicability. Most of the talk only uses basic algebra and elementary knowledge of WWII.

Contact Information: rachel.d'antonio@uconn.edu
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PDE and Differential Geometry Seminar

Building quasiregular mappings between sub-Riemannian manifolds

Anton Lukyanenko

George Mason University

Monday, April 29th, 201902:30 PM - 03:30 PM

Storrs Campus

MONT 214

Abstract: A quasiregular (qr) mapping folds one space over, with limited distortion of topology and of relative distances. The theory of qr mappings in Euclidean spaces is rich with examples and connections complex analysis, dynamical systems, and PDEs. In the early 2000s, Heinonen and Rickman initiated a broader study of qr mappings in more general metric spaces, such as the Heisenberg group. In this talk, I will give an introduction to the field, and discuss some recent results on building and forbidding qr mappings between sub-Riemannian manifolds.

Contact Information: Wang, lihan.wang@uconn.edu
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Algebra Seminar

Title TBA

Yifeng Liu (Yale University)

Wednesday, May 1st, 201911:15 AM - 12:05 PM

Storrs Campus

Monteith, 313

TBA

Contact Information: Mihai Fulger, mihai.fulger@uconn.edu
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### Annnual Logic Lecture: Sara Negri (Helsinki)

Wednesday, May 1st, 201904:00 PM - 05:30 PM

Storrs Campus

Humanities Institute seminar room, Babbidge Library, 4th Floor

Each year, the UConn Logic Group bestows the title of Scholar of Consequence to an eminent logician whose work shaped the field.

The 2019 Scholar of Consequence is Sara Negri (Helsinki, Finland).

Professor Negri will give the following public the Annual Logic Lecture:

A three-fold method for non-classical logics

Abstract:

There are three established ways of analysing the validity of a logical argument: axiomatic, semantic, and inferential; they correspond to what could be called the normative, the descriptive, and the deductive face of a logical system and are tightly related to each other by fundamental meta-theorems.

For non-classical logics, each of the three aspects has drawbacks when considered in isolation. The situation changes, however, drastically when the three aspects are developed in parallel. Through the labelled formalism, by now is a well-developed methodology, models can be considered as purely mathematical objects with no ontological assumptions upon them: the semantics is turned into an essential component in the syntax of sequent calculi with invertible rules. Such calculi not only provide a tool for the automatisation of reasoning, but can also be used to establish very general properties of logical systems.

All welcome!

https://logic.uconn.edu/annual-logic-lecture/

The 2019 Scholar of Consequence is Sara Negri (Helsinki, Finland).

Professor Negri will give the following public the Annual Logic Lecture:

A three-fold method for non-classical logics

Abstract:

There are three established ways of analysing the validity of a logical argument: axiomatic, semantic, and inferential; they correspond to what could be called the normative, the descriptive, and the deductive face of a logical system and are tightly related to each other by fundamental meta-theorems.

For non-classical logics, each of the three aspects has drawbacks when considered in isolation. The situation changes, however, drastically when the three aspects are developed in parallel. Through the labelled formalism, by now is a well-developed methodology, models can be considered as purely mathematical objects with no ontological assumptions upon them: the semantics is turned into an essential component in the syntax of sequent calculi with invertible rules. Such calculi not only provide a tool for the automatisation of reasoning, but can also be used to establish very general properties of logical systems.

All welcome!

https://logic.uconn.edu/annual-logic-lecture/

Contact Information: https://logic.uconn.edu/about/
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### Logic Colloquium: Sara Negri (Helsinki)

Thursday, May 2nd, 201904:00 PM - 05:30 PM

Storrs Campus

Humanities Institute seminar room, Babbidge Library, 4th Floor

Join is for the Logic Colloquium given by the 2019 Scholar of Consequence!

Sara Negri (Helsinki, Finland)

"Unveiling the constructive core of classical theories: A contribution to 90 years of Glivenko’s theorem"

Abstract:

Glivenko’s well known result of 1929 established that a negated propositional formula provable in classical logic is even provable intuitionistically. Similar later transfers from classical to intuitionistic provability therefore fall under the nomenclature of Glivenko-style results: these are results about classes of formulas for which classical provability yields intuitionistic provability. The interest in isolating such classes lies in the fact that it may be easier to prove theorems by the use of classical rather than intuitionistic logic. Further, since a proof in intuitionistic logic can be associated to a lambda term and thus obtain a computational meaning, such results have more recently been gathered together under the conceptual umbrella “computational content of classical theories.” They also belong to a more general shift of perspective in foundations: rather than developing constructive mathematics separately, as in Brouwer’s program, one studies which parts of classical mathematics can be directly translated into constructive terms.

We shall survey how Glivenko-style results can be easily obtained by the choice of suitable sequent calculi for classical and intuitionistic logic, by the conversion of axioms into inference rules, and by the procedure of geometrization of first order logic.

All welcome!

https://logic.uconn.edu/calendar/

Sara Negri (Helsinki, Finland)

"Unveiling the constructive core of classical theories: A contribution to 90 years of Glivenko’s theorem"

Abstract:

Glivenko’s well known result of 1929 established that a negated propositional formula provable in classical logic is even provable intuitionistically. Similar later transfers from classical to intuitionistic provability therefore fall under the nomenclature of Glivenko-style results: these are results about classes of formulas for which classical provability yields intuitionistic provability. The interest in isolating such classes lies in the fact that it may be easier to prove theorems by the use of classical rather than intuitionistic logic. Further, since a proof in intuitionistic logic can be associated to a lambda term and thus obtain a computational meaning, such results have more recently been gathered together under the conceptual umbrella “computational content of classical theories.” They also belong to a more general shift of perspective in foundations: rather than developing constructive mathematics separately, as in Brouwer’s program, one studies which parts of classical mathematics can be directly translated into constructive terms.

We shall survey how Glivenko-style results can be easily obtained by the choice of suitable sequent calculi for classical and intuitionistic logic, by the conversion of axioms into inference rules, and by the procedure of geometrization of first order logic.

All welcome!

https://logic.uconn.edu/calendar/

Contact Information: https://logic.uconn.edu/about/
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S.I.G.M.A. Seminar

3 types of Hopf fibrations, connecting geometry, algebra, physics, and probability

Gunhee Cho

Friday, May 3rd, 201912:20 PM - 01:10 PM

Storrs Campus

MONT 2014

This is the soft introduction to the very recent paper (https://arxiv.org/abs/1904.08568) which is joint work with a prof. F. Baudoin. From Hurwitz's theorem, all normed division algebra over real numbers up to isomorphism is the algebras of real numbers, complex numbers C, quaternions H, and octonions O. One way to understand those division algebras is by investigating so-called the Hopf fibration. We will try to see which geometric structures and probability tools play a role to understand each division algebras. This talk would be accessible to a general math audience.

Contact Information: Lisa Naples (lisa.naples@uconn.edu)
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Analysis and Probability Seminar

Nonlocal Operators with singular anisotropic kernels

Jamil Chaker (University of Chicago)

Friday, May 3rd, 201901:30 PM - 02:30 PM

Storrs Campus

MONT 313

Abstract: We study nonlocal operators that generate anisotropic jump processes, such as a jump process that behaves like a stable process in each direction but with a different index of stability. Its generator is the sum of one-dimensional fractional Laplace operators with different orders of differentiability. We study such operators in the general framework of bounded measurable coefficients.

The objective of this talk is to provide regularity results for weak solutions to corresponding integro-differential equations.

Joint work with Moritz Kassmann.

The objective of this talk is to provide regularity results for weak solutions to corresponding integro-differential equations.

Joint work with Moritz Kassmann.

Contact Information: Scott Zimmerman, scott.zimmerman@uconn.edu
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Analysis Learning Seminar

Title: TBA

Gianmarco Molino

Friday, May 3rd, 201903:30 PM - 04:30 PM

Storrs Campus

MONT 313

Abstract: TBA

Contact Information: Murat Akman and Vyron Vellis
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