### Table of Contents

# Schedule

## Fall 2019

#### October 16

##### Speaker: TBA

The first meeting of the semester.

Let us gather, greet new members to the Department, and set a plan for the semester before us.

We can play some warm-up board games to get to know each other, and hear some information on the ICT-Innovations event from experienced participants.

#### October 21

##### Speaker: Shoya Motonaga

*link,*

**Topic: TBA**

#### October 28

##### Speaker: Kaito Ito

*link,*

**Topic: Stochastic dynamical models with heavy-tailed noise**

In order to evaluate the effect of probabilistic uncertainty, stochastic dynamical models play an important role. In particular, a linear dynamical system driven by the Wiener process is a popular framework. Although this framework is tractable analytically, it cannot represent outliers due to the Gaussianity. On the other hand, a modeling method for uncertainty that utilizes stable processes instead of the Wiener process is proposed recently. This method can model dynamics equipped with extreme outliers, and the model has similar mathematical properties to the linear Gaussian model. Then we first explain the non-Gaussian framework and its properties. In addition, we introduce our recent work using this framework. This work provides the error analysis for linearization of nonlinear feedback systems.

#### November 6

##### Speaker: Naveed Ahmed Azam

*link,*

**Topic: Counting Tree-Like Graphs with a Given Number of Vertices and Self-loops**

Graph enumeration with given constraints is an interesting problem considered to be one of the fundamental problems in graph theory, with many applications in natural sciences and engineering such as bio-informatics and computational chemistry. For any two integers n ≥ 1 and ∆ ≥ 0, we propose a method to count all non-isomorphic trees with n vertices, ∆ self-loops, and no multi-edges based, on dynamic programming. To achieve this goal, we count the number of non-isomorphic rooted trees with n vertices, ∆ self-loops and no multi-edges, in O(n^2(n + ∆(n + ∆ · min{n, ∆}))) time and O(n^2(∆^2 + 1)) space, since every tree can be uniquely viewed as a rooted tree by either regarding its unicentroid as the root, or in the case of bicentroid, by introducing a virtual vertex on the bicentriod and assuming the virtual vertex to be the root.

#### November 18

##### Speaker: Shogo Yamanaka

*link,*

**Topic: Convergent normalization and integrability of two-dimensional systems of differential equations**

We consider systems of differential equations with equilibrium points. These systems are formally transformed to Poincaré-Dulac normal forms, but the normalization may not be convergent. Such an convergent normalization is a classical problem that dates back to Poincaré. Zung proved that analytically integrable systems of differential equations have convergent normalizations. In this talk, we prove thet a special class of two-dimensional systems have no convergent normalizations so that they are not integrable.

#### December 2

##### Speaker: Hiroki Tanabe

*link,*

**Topic: Introduction to multiobjective optimization: Pareto optimality and multiobjective descent methods**

We present a basic notions of multiobjective optimization and multiobjective extensions of two well-known scalar optimization algorithms. First, we explain Pareto optimality, which is an optimality for multiobjective optimization. Next, we introduce two multiobjective versions of descent methods: steepest descent method and proximal gradient method. They are both computed by solving scalar-valued subproblems, and line-search procedure.

#### December 16

##### Speaker: TBA

*link,*

**Topic: TBA**

#### December 23

##### Speaker: Zhen Man

*link,*

**Topic: TBA**

#### January 6

##### Speaker: Hardik Tankaria

*link,*

**Topic: TBA**

#### January 14

##### Speaker: Tomoyuki Mao

*link,*

**Topic: TBA**