立命館大学数理科学科

立命館大学数理科学科 http://www.math.ritsumei.ac.jp/home2 立命館大学理工学部数理科学科です。幅広い領域での数学の研究・活用を通して人類の福祉と発展に貢献できる人材を育成することを目標としています。 Fri, 05 Jun 2026 05:15:26 +0000 ja hourly 1 https://wordpress.org/?v=3.9.40 Math-Fi seminar on 4 Jun. (Co-organized as a Quantum Walk Seminar) http://www.math.ritsumei.ac.jp/home2/?p=2306 http://www.math.ritsumei.ac.jp/home2/?p=2306#comments Thu, 04 Jun 2026 03:08:51 +0000 http://www.math.ritsumei.ac.jp/home2/?p=2306

Date: 4 Jun. (Thu.)

Place: West Wing, 6th floor, Colloquium Room and on the Web (zoom)

Time: 17:00-19:10

Speaker 1: Santhosh K. Pamula (IISER, Mohali)

Time:17:00-18:00

Title: Structure of local completely contractive maps

Abstract:

Local completely contractive maps are a particular class of continuous linear maps on

locally C∗-algebras, which are inverse limit of inverse system of C∗-algebras in the category of

topological ∗-algebras. In this talk, we present a structure theorem for unbounded operator valued

local completely contractive map ψ on a locally C∗-algebra A. There is a unique commutant

operator T in the structure of ψ with norm at most 2. We show that the operator T is a contraction

if and only if the block map

Φ= φ ψ

ψ∗ φ

defined on M2(A) is local completely positive, for some local completely positive and local

completely contractive map φ on A. In general, such a map φ may not exist for a given ψ, we

illustrate this situation with an example. However, we prove a block representation of ψ in the sense

that there always exist a local completely positive and local completely bounded map φ such that Φ

is a local completely positive map. This is a joint work with R. Siddique

Speaker 2: Takuya Machida (Nihon University)
Time:18:10-19:10
Title:非局在化状態を初期状態とする量子ウォークの極限分布

]]> http://www.math.ritsumei.ac.jp/home2/?feed=rss2&p=2306 0 Math-Fi seminar on 21 May. http://www.math.ritsumei.ac.jp/home2/?p=2302 http://www.math.ritsumei.ac.jp/home2/?p=2302#comments Thu, 21 May 2026 04:05:29 +0000 http://www.math.ritsumei.ac.jp/home2/?p=2302

Date: 21 May. (Thu.)

Place: West Wing, 6th floor, Colloquium Room and on the Web (zoom)

Time: 16:50-18:20

Speaker : Naoki Masuda (University of Michigan)

Title: 高次ネットワーク上の意見形成確率モデル

Abstract:

本講演では、まず、ネットワーク科学という研究分野の簡単な紹介を行う。次に、いくつかの種類の高次ネットワーク上の進化ダイナミクスの研究について紹介する。進化ダイナミクスは、本研究の範囲で言えば、平たく言うと、集団意見形成ダイナミクスを表す確率過程である。高次ネットワークとしては、近年のネットワーク科学で盛んに研究されている構造でもあるハイパーグラフ、多層ネットワーク、テンポラル（＝ネットワーク自体が時間変化する）・ネットワークを考える。（逆に、高次でないネットワークは、典型的なネットワーク、すなわち数学で言う「グラフ」のことを表す。）これらの高次ネットワーク上での上記確率過程の振る舞いは、典型的なネットワークの上での同じ確率過程と比べてかなり異なる。具体的には、ネットワークが進化の「増幅器」でありやすいか、「抑制器」でありやすいか、が異なる。このことを、マルチンゲール解析、数値計算などによって示す。

]]> http://www.math.ritsumei.ac.jp/home2/?feed=rss2&p=2302 0 Math-Fi seminar on 14 May. http://www.math.ritsumei.ac.jp/home2/?p=2300 http://www.math.ritsumei.ac.jp/home2/?p=2300#comments Thu, 14 May 2026 02:51:49 +0000 http://www.math.ritsumei.ac.jp/home2/?p=2300

Date: 14 May. (Thu.)

Place: West Wing, 6th floor, Colloquium Room and on the Web (zoom)

Time: 16:50-18:20

Speaker : Alessio Rondelli (University of Bologna)

Title: McKean-Vlasov SDEs and particle systems: What, Why and How.

Abstract:

McKean-Vlasov SDEs are a class of Stochastic Differential Equations
where the coefficients depend upon the marginals of the solution. Their
study is justified by their usefulness in modeling the evolution of
multi-agent systems using the mean-field approximation. Both classical
and modern techniques are presented for strong and weak well-posedness
and the concept of propagation of chaos gets explored.

]]> http://www.math.ritsumei.ac.jp/home2/?feed=rss2&p=2300 0 Math-Fi seminar on 23 Apr. (Co-organized as a Quantum Walk Seminar) http://www.math.ritsumei.ac.jp/home2/?p=2297 http://www.math.ritsumei.ac.jp/home2/?p=2297#comments Thu, 23 Apr 2026 07:15:53 +0000 http://www.math.ritsumei.ac.jp/home2/?p=2297

Date: 23 Apr. (Thu.)

Place: West Wing, 6th floor, Colloquium Room and on the Web (zoom)

Time: 16:50-17:50

Speaker : Hiromichi OHNO (Shinshu University)

Title: Maze solving by quantum walk

Abstract:

本講演では，グラフを迷路に見立て，スタートとゴールを設定し，グローバーウォークを用いてスタートからゴールまでの経路を発見するアルゴリズムについて解説する．このアルゴリズムでは，量子ウォークの収束することは示せているが，収束先の確率分布から経路を発見できるかどうかは部分的な解答しか得られていない．これらの内容について数学的な証明を与えながら，具体的ないくつかの例を紹介する．

]]> http://www.math.ritsumei.ac.jp/home2/?feed=rss2&p=2297 0 Math-Fi seminar on 17 Apr. http://www.math.ritsumei.ac.jp/home2/?p=2295 http://www.math.ritsumei.ac.jp/home2/?p=2295#comments Thu, 16 Apr 2026 07:41:03 +0000 http://www.math.ritsumei.ac.jp/home2/?p=2295

Date: 17 Apr. (Thu.)

Place: West Wing, 6th floor, Colloquium Room and on the Web (zoom)

Time: 16:20-17:50

Speaker : Antoine Jacquier (Imperial College)

Title: Quantum Computing, a new toolbox for Stochastic Analysis & Machine Learning?

Abstract:

We are interested here in recent developments in Quantum Computing from an algorithmic standpoint and with a view towards applications (with an emphasis on Mathematical Finance and Stochastic Analysis). We shall in particular focus on Universal Approximations theorems for Parameterised Quantum Circuits as well as on the links between (partial) measurements of Quantum systems and Stochastic diffusions.

]]> http://www.math.ritsumei.ac.jp/home2/?feed=rss2&p=2295 0 Math-Fi seminar on 9 Apr. (Co-organized as a Quantum Walk Seminar) http://www.math.ritsumei.ac.jp/home2/?p=2291 http://www.math.ritsumei.ac.jp/home2/?p=2291#comments Thu, 09 Apr 2026 06:15:09 +0000 http://www.math.ritsumei.ac.jp/home2/?p=2291

Date: 9 Apr. (Thu.)

Place: West Wing, 6th floor, Colloquium Room and on the Web (zoom)

Time: 16:50-17:50

Speaker : Yohei Tanaka (Ritsumeikan University)

Title: On understanding chiral unitaries via real parts

Abstract:

We study unitary operators with chiral symmetry, that is, unitary operators associated with a fixed involution. Such operators naturally arise in the study of quantum walks and related areas. A standard approach is to decompose the underlying Hilbert space according to this symmetry, which leads to a convenient block representation. In this framework, we focus on the real part of the unitary and use it as a useful tool to understand its spectral structure. Based on this viewpoint, we present several related topics and results, illustrating how the real-part perspective provides a simple and unified way to analyze chiral unitaries.

]]> http://www.math.ritsumei.ac.jp/home2/?feed=rss2&p=2291 0 立命館大学集中セミナー http://www.math.ritsumei.ac.jp/home2/?p=2288 http://www.math.ritsumei.ac.jp/home2/?p=2288#comments Tue, 07 Apr 2026 02:34:38 +0000 http://www.math.ritsumei.ac.jp/home2/?p=2288

Date: 9月14日－18日

Place: ウエストウィング6階談話会室あるいは７階のセミナー室　対面およびオンライン

Time:

9月14日(月)～17日 (木)

2コマ:

(1) 13:30～15:00

(2) 15:15～16:45

9月18日 (金)

1コマ13:30～15:00

Speaker : 日合文雄（東北大学名誉教授）
Title: 行列解析と量子情報への応用
Abstract:

この集中セミナーでは，最初に作用素平均と作用素パースペクティブを復習してから，作用素・

行列の作用素不等式，マジョリゼーション，トレース不等式などを解説する．次に，量子情報

で重要な種々の量子f-ダイバージェンスを説明する．特に最近発展しているホッケースチック

f-ダイバージェンスを取り上げる．さらに，量子情報幾何で重要なFisher 情報量（単調計量）

と関連するいくつかの話題を解説する．

]]> http://www.math.ritsumei.ac.jp/home2/?feed=rss2&p=2288 0 Math-Fi seminar on 2 Apr. http://www.math.ritsumei.ac.jp/home2/?p=2287 http://www.math.ritsumei.ac.jp/home2/?p=2287#comments Tue, 07 Apr 2026 01:51:01 +0000 http://www.math.ritsumei.ac.jp/home2/?p=2287

Date: 2 Apr. (Thu.)

Place: West Wing, 6th floor, Colloquium Room and on the Web (zoom)

Time: 12:00-13:30

Speaker : VU HUY HOANG (University of California, Santa Barbara)

Commentator : Ju-Yi Yen (University of Cincinnati)

Title: Molchanov’s Formula and Quantum Walks: A Probabilistic Approach

Abstract:

This paper establishes a robust link between quantum dynamics and classical ones by deriving a probabilistic representation for both continuous-time and discrete-time quantum walks. We first adapt the Molchanov formula, originally employed in the study of Schrodinger operators on multidimensional integer lattices, to characterize the evolution of continuous time quantum walks. Extending this framework, we develop a probabilistic method to represent discrete time quantum walks on an infinite integer line, bypassing the locality constraints that typically inhibit direct application of the Molchanov formula. The validity of our representation is empirically confirmed through a benchmark analysis of the Hadamard walk, demonstrating high fidelity with traditional unitary evolution. Our results suggest that this probabilistic lens offers a powerful alternative for learning multidimensional quantum walks and provides new analytical pathways for investigating quantum systems via classical stochastic processes.

]]> http://www.math.ritsumei.ac.jp/home2/?feed=rss2&p=2287 0 Math-Fi seminar on 31 Mar. http://www.math.ritsumei.ac.jp/home2/?p=2280 http://www.math.ritsumei.ac.jp/home2/?p=2280#comments Tue, 07 Apr 2026 01:17:58 +0000 http://www.math.ritsumei.ac.jp/home2/?p=2280

Date: 31 Mar. (Tue.)

Place: West Wing, 6th floor, Colloquium Room and on the Web (zoom)

Time: 16:00–17:30

Speaker : Joseph Najnudel (University of Bristol)

Commentator : Ju-Yi Yen (University of Cincinnati)

Title: The Riemann zeta function and its connection with random matrix theory.

Abstract:

In this talk, we present some results and conjectures on the Riemann zeta function, its moments on the critical line, its extreme values, and its behaviour at the scale of the average spacing of the zeros. We then connect these results to similar properties satisfied by the characteristic polynomial of random unitary matrices.

]]> http://www.math.ritsumei.ac.jp/home2/?feed=rss2&p=2280 0 Ritsumeikan Geometry Seminar on 13 Mar. http://www.math.ritsumei.ac.jp/home2/?p=2276 http://www.math.ritsumei.ac.jp/home2/?p=2276#comments Fri, 27 Feb 2026 07:14:01 +0000 http://www.math.ritsumei.ac.jp/home2/?p=2276 Date: March 13, Friday, 2026

Place: Colloquium room, West-Wing 6F, Biwako-Kusatsu Campus + Zoom meeting

Registration URL for Zoom:

https://ritsumei-ac-jp.zoom.us/meeting/register/A90nnMv0RNC7PFizhntG_w

-Program- (modified on March 1)

15:20-16:20 Steven Hurder (University of Illinois at Chicago)

The dynamics of commensurators

16:30-17:30 Olga Lukina (Leiden University)

Cantor actions in dynamical systems

-Abstract-

Speaker 1: Steven Hurder (University of Illinois at Chicago)

Title: The dynamics of commensurators
Abstract:

A commensurator of a countable group G is a virtual automorphism. That is, it is an isomorphism f : H -> K where H and K are subgroups of finite index of G. We associate to a commensurator f of G, a homeomorphism F : C -> C of a Cantor set C. In the general case the space C is the profinite completion of G, but our interest is in more general case where C is a quotient of the profinite completion of G. We study the dynamical properties of the map F : C -> C.

Speaker 2: Olga Lukina (Leiden University)
Title: Cantor actions in dynamical systems
Abstract:

In this talk, we consider dynamical systems on Cantor sets, given by group actions. Such systems arise as transverse dynamical systems in strange attractors and exceptional minimal sets of foliations. We present a few classification results.

Organizers:

Fukumoto Yoshihiro, Tarama Daisuke, Nozawa Hiraku

Contact:

hnozawa@fc.ritsumei.ac.jp

]]> http://www.math.ritsumei.ac.jp/home2/?feed=rss2&p=2276 0