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(Program updated) Workshop: Diagrammatics for Combinatorics, Algebra, and Topology (Jul 20-24, SKKU)
by 이신명 24 Jun '26

24 Jun '26

Dear colleagues, Hello, it is Sin-Myung Lee from KIAS. This is the second announcement of the upcoming workshop "Diagrammatics for Combinatorics, Algebra, and Topology" on July 20-24, held at Sungkyunkwan University, Suwon. The workshop is intended to provide an open, accessible space to learn and discuss diagrammatic methods in combinatorics, algebra and topology, welcoming everyone from students to working mathematicians. To this end, the workshop will begin with three lecture series (3 hours each plus exercise sessions) covering the following keywords: Ben Elias (University of Oregon) : Soergel bimodules and their diagrammatics Matthew Hogancamp (Northeastern University)* : link invariants, categorification of braid groups Linhui Shen (Michigan State University)* : braid varieties, cluster structures via weaves, connections with Legendrian knots and representations (*:subject to change, title and abstract will be updated on the website shortly) and then conclude with six research talks for more recent developments, delivered by Elise Catania (University of Minnesota - Twin Cities) Donghyun Kim (Ewha Womans University) Myungho Kim (Kyung Hee University) Hankyung Ko (Uppsala University) Mikhail Mazin (Kensas State University) Nathan Williams (University of Texas at Dallas). whose titles and abstracts can be found from our website: https://sites.google.com/view/dcat2026/home If you are interested, kindly register from https://sites.google.com/view/dcat2026/registration before June ends to stay updated and help us prepare the workshop smoothly. Please feel free to forward this announcement to anyone who might be interested, especially to students. We are looking forward to your participation! Best regards, Sin-Myung Lee Jaeseong Oh

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(Reminder) CART seminar announcement (Grigori Olshanski, Jun 12 (Fri), 16:30PM)
by 이신명 11 Jun '26

11 Jun '26

Dear all, This is a gentle reminder of the CART seminar by Grigori Olshanski (HSE University) tomorrow at 16:30 - 17:30 in Korea time (15:30 - 16:30 in Beijing). Hope to see you at the seminar! Best regards, Sin-Myung Lee -----------------------원본 메세지----------------------- 보낸사람: "이신명"<sinmyunglee(a)kias.re.kr> 받는사람: "Mathematics Members(mathall)" <mathall(a)kias.re.kr>, cart-seminar(a)snurep.crystalline.site 참조: "Grigori Olshanski" <olsh2007(a)gmail.com>, "Cesar Cuenca" <cesar.a.cuenk(a)gmail.com> 보낸날짜: 2026-06-07 20:59:54 GMT +0900 (Asia/Seoul)제목: CART seminar announcement (Grigori Olshanski, Jun 12 (Fri), 16:30PM) Dear all, The last CART seminar of this semester is scheduled for June 12th (Fri), at the unusual time 16:30 - 17:30 in Korea time (15:30 - 16:30 in Beijing). Speaker: Grigori Olshanski (HSE University) Title: Infinite-dimensional groups over finite fields and a related positivity problem in symmetric function theory Abstract: Sergei Kerov and Anatoly Vershik discovered a remarkable family of infinite-dimensional matrix groups over finite fields. These groups are locally compact, totally disconnected and bear some resemblance with reductive p-adic groups. The study of these infinite-dimensional groups and their representations is in the beginning stages. However, there are a number of promising results and a lot of intriguing open problems, some of which admit a reformulation in the language of symmetric functions. I will present an introduction to this area. The talk is based on joint work with Cesar Cuenca. You can join the seminar via the following Zoom link: https://kias-re-kr.zoom.us/j/82020074666?pwd=zTWOBlcmPxFYpcRfObhMqXPfCai7Xm… ID: 820 2007 4666 password: 764471 Please feel free to forward this to anyone who might be interested. You can check out further information on CART seminar on our website (https://sites.google.com/view/cart-kias/). Looking forward to seeing you at the seminar! Best regards, Sin-Myung Lee

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CART seminar announcement (Grigori Olshanski, Jun 12 (Fri), 16:30PM)
by 이신명 07 Jun '26

07 Jun '26

Dear all, The last CART seminar of this semester is scheduled for June 12th (Fri), at the unusual time 16:30 - 17:30 in Korea time (15:30 - 16:30 in Beijing). Speaker: Grigori Olshanski (HSE University) Title: Infinite-dimensional groups over finite fields and a related positivity problem in symmetric function theory Abstract: Sergei Kerov and Anatoly Vershik discovered a remarkable family of infinite-dimensional matrix groups over finite fields. These groups are locally compact, totally disconnected and bear some resemblance with reductive p-adic groups. The study of these infinite-dimensional groups and their representations is in the beginning stages. However, there are a number of promising results and a lot of intriguing open problems, some of which admit a reformulation in the language of symmetric functions. I will present an introduction to this area. The talk is based on joint work with Cesar Cuenca. You can join the seminar via the following Zoom link: https://kias-re-kr.zoom.us/j/82020074666?pwd=zTWOBlcmPxFYpcRfObhMqXPfCai7Xm… ID: 820 2007 4666 password: 764471 Please feel free to forward this to anyone who might be interested. You can check out further information on CART seminar on our website (https://sites.google.com/view/cart-kias/). Looking forward to seeing you at the seminar! Best regards, Sin-Myung Lee

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(Reminder) CART seminar announcement (Soyeon Kim, Jun 5 (Fri), 10:30AM)
by 이신명 03 Jun '26

03 Jun '26

Dear all, This is a gentle reminder of the CART seminar by Soyeon Kim (UC Davis) tomorrow at 10:30 - 11:30 in Korea time (9:30 - 10:30 in Beijing). Hope to see you at the seminar! Best regards, Sin-Myung Lee -----------------------원본 메세지----------------------- 보낸사람: "이신명"<sinmyunglee(a)kias.re.kr> 받는사람: "Mathematics Members(mathall)" <mathall(a)kias.re.kr>, cart-seminar(a)snurep.crystalline.site 참조: syxkim(a)math.ucdavis.edu 보낸날짜: 2026-05-26 22:59:38 GMT +0900 (Asia/Seoul) 제목: CART seminar announcement (Soyeon Kim, Jun 5 (Fri), 10:30AM) Dear all, The next CART seminar is scheduled for June 5th (Fri), 10:30 - 11:30 in Korea time (9:30 - 10:30 in Beijing). Speaker: Soyeon Kim (UC Davis) Title: Unexpected toric Richardson varieties Abstract: In this talk, we introduce a new class of toric Richardson varieties, which we call unexpected toric Richardson varieties. These Richardson varieties are toric varieties with respect to the action of a torus of higher dimension (compared to the standard torus case), whose torus action was previously completely unexplored. The standard torus action on Richardson varieties and a characterization of (expected) toric Richardsons with respect to the standard torus were well understood. The existence of such unexpected toric Richardsons were implied by our characterization result for all toric Richardson varieties: the open Richardson variety $R_{v,w}$ in the complete flag variety is a torus $\mathbb{T}$ if and only if the closed Richardson variety $\overline{R}_{v,w}$ is a toric variety with respect to $\mathbb{T}$. Equivalently, this can be said that when the Bruhat interval $[ v , w ] $ is a lattice. Moreover, we prove that similar to the standard torus case, the moment polytopes for all toric Richardson varieties have a nice combinatorial description in terms of Bruhat interval. This is based on my joint work with Eugene Gorsky and Melissa Sherman-Bennett. You can join the seminar via the following Zoom link: https://kias-re-kr.zoom.us/j/86733679216?pwd=K7Nm3op6PSzkL4PRDtyKiKSavdIayw… ID: 867 3367 9216 password: 067888 Please feel free to forward this to anyone who might be interested. You can check out further information on CART seminar on our website (https://sites.google.com/view/cart-kias/). Looking forward to seeing you at the seminar! Best regards, Sin-Myung Lee

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CART seminar announcement (Soyeon Kim, Jun 5 (Fri), 10:30AM)
by 이신명 29 May '26

29 May '26

Dear all, The next CART seminar is scheduled for June 5th (Fri), 10:30 - 11:30 in Korea time (9:30 - 10:30 in Beijing). Speaker: Soyeon Kim (UC Davis) Title: Unexpected toric Richardson varieties Abstract: In this talk, we introduce a new class of toric Richardson varieties, which we call unexpected toric Richardson varieties. These Richardson varieties are toric varieties with respect to the action of a torus of higher dimension (compared to the standard torus case), whose torus action was previously completely unexplored. The standard torus action on Richardson varieties and a characterization of (expected) toric Richardsons with respect to the standard torus were well understood. The existence of such unexpected toric Richardsons were implied by our characterization result for all toric Richardson varieties: the open Richardson variety $R_{v,w}$ in the complete flag variety is a torus $\mathbb{T}$ if and only if the closed Richardson variety $\overline{R}_{v,w}$ is a toric variety with respect to $\mathbb{T}$. Equivalently, this can be said that when the Bruhat interval $[ v , w ] $ is a lattice. Moreover, we prove that similar to the standard torus case, the moment polytopes for all toric Richardson varieties have a nice combinatorial description in terms of Bruhat interval. This is based on my joint work with Eugene Gorsky and Melissa Sherman-Bennett. You can join the seminar via the following Zoom link: https://kias-re-kr.zoom.us/j/86733679216?pwd=K7Nm3op6PSzkL4PRDtyKiKSavdIayw… ID: 867 3367 9216 password: 067888 Please feel free to forward this to anyone who might be interested. You can check out further information on CART seminar on our website (https://sites.google.com/view/cart-kias/). Looking forward to seeing you at the seminar! Best regards, Sin-Myung Lee

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(Reminder) CART seminar announcement (Reuven Hodges, May 22 (Fri), 10:30AM)
by 이신명 21 May '26

21 May '26

Dear all, This is a gentle reminder of the CART seminar by Reuven Hodges (University of Kansas) tomorrow at 10:30 - 11:30 in Korea time (9:30 - 10:30 in Beijing). Hope to see you at the seminar! Best regards, Sin-Myung Lee -----------------------원본 메세지----------------------- 보낸사람: "이신명"<sinmyunglee(a)kias.re.kr> 받는사람: "Mathematics Members(mathall)" <mathall(a)kias.re.kr>, cart-seminar(a)snurep.crystalline.site 참조: "Hodges,Reuven Moses" <rmhodges(a)ku.edu> 보낸날짜: 2026-05-13 18:29:19 GMT +0900 (Asia/Seoul) 제목: CART seminar announcement (Reuven Hodges, May 22 (Fri), 10:30AM) Dear all, The next CART seminar is scheduled for May 22nd (Fri), 10:30 - 11:30 in Korea time (9:30 - 10:30 in Beijing). Speaker: Reuven Hodges (University of Kansas) Title: Orbits structures and complexity in Schubert and Richardson varieties Abstract: The study of orbits and orbit closures in the flag variety has a long and storied history with deep connections to algebraic combinatorics, Lie theory, and representation theory. The orbits of Borel subgroups and their Zariski closures, the Schubert varieties, have been of particular import. A central notion in this area is the complexity of a reductive group action on a variety, which equals the minimum codimension of a Borel subgroup orbit. In this talk we provide a type-uniform formula for the torus complexity of the usual torus action on a Richardson variety by developing the notion of algebraic dimensions of Bruhat intervals. Then, when a Levi subgroup acts on a Schubert variety, we exhibit a codimension preserving bijection between the Levi-Borel subgroup orbits in the big open cell of that Schubert variety and the torus orbits in the big open cell of a distinguished Schubert subvariety. This allows us to give a type-uniform formula for the Levi-Borel complexity of that Schubert variety. You can join the seminar via the following Zoom link: https://kias-re-kr.zoom.us/j/82665363913?pwd=7PO3Wck3khxsA6asEIHalVcjYDQDKV… Meeting ID: 826 6536 3913 Password: 236303 Please feel free to forward this to anyone who might be interested. You can check out further information on CART seminar on our website (https://sites.google.com/view/cart-kias/). Looking forward to seeing you at the seminar! Best regards, Sin-Myung Lee

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CART seminar announcement (Reuven Hodges, May 22 (Fri), 10:30AM)
by 이신명 15 May '26

15 May '26

Dear all, The next CART seminar is scheduled for May 22nd (Fri), 10:30 - 11:30 in Korea time (9:30 - 10:30 in Beijing). Speaker: Reuven Hodges (University of Kansas) Title: Orbits structures and complexity in Schubert and Richardson varieties Abstract: The study of orbits and orbit closures in the flag variety has a long and storied history with deep connections to algebraic combinatorics, Lie theory, and representation theory. The orbits of Borel subgroups and their Zariski closures, the Schubert varieties, have been of particular import. A central notion in this area is the complexity of a reductive group action on a variety, which equals the minimum codimension of a Borel subgroup orbit. In this talk we provide a type-uniform formula for the torus complexity of the usual torus action on a Richardson variety by developing the notion of algebraic dimensions of Bruhat intervals. Then, when a Levi subgroup acts on a Schubert variety, we exhibit a codimension preserving bijection between the Levi-Borel subgroup orbits in the big open cell of that Schubert variety and the torus orbits in the big open cell of a distinguished Schubert subvariety. This allows us to give a type-uniform formula for the Levi-Borel complexity of that Schubert variety. You can join the seminar via the following Zoom link: https://kias-re-kr.zoom.us/j/82665363913?pwd=7PO3Wck3khxsA6asEIHalVcjYDQDKV… Meeting ID: 826 6536 3913 Password: 236303 Please feel free to forward this to anyone who might be interested. You can check out further information on CART seminar on our website (https://sites.google.com/view/cart-kias/). Looking forward to seeing you at the seminar! Best regards, Sin-Myung Lee

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CART Seminar announcement (Aritra Bhattacharya, Apr 17 (Fri), 10:30AM)
by 이신명 16 Apr '26

16 Apr '26

Dear all, The next CART seminar is scheduled for Apr 17th (Fri), 10:30 - 11:30 in Korea time (9:30 - 10:30 in Beijing). Speaker: Aritra Bhattacharya (Beijing International Center for Mathematical Research) Title: On factorization of matrix of Kazhdan-Lusztig polynomials Abstract: The famous Kazhdan-Lusztig positivity states that the transition matrix between the canonical basis and the standard basis of the Hecke algebra (of a Weyl group) is a matrix with polynomial entries with non-negative integer coefficients. In this talk we will describe a factorization of this positivity via certain intermediate bases called the hybrid bases. We will also present a reformulation of the statements in terms of a natural restriction map on Hecke algebras. This framework also subsumes the positivity of parabolic Kazhdan-Lusztig polynomials corresponding to the sign representations. This is joint work with Ashish Mishra and Shraddha Srivastava. You can join the seminar via the following Zoom link: https://kias-re-kr.zoom.us/j/89659176224?pwd=TLxuQ7yKEqgGCnnBb6NxDE8z20J6lM… Meeting ID: 896 5917 6224 Password: 947850 Please feel free to forward this to anyone who might be interested. You can check out further information on CART seminar on our website (https://sites.google.com/view/cart-kias/). Looking forward to seeing you at the seminar! Best regards, Sin-Myung Lee

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Workshop announcement: Diagrammatics for Combinatorics, Algebra, and Topology (Jul 20-24, SKKU)
by 이신명 06 Apr '26

06 Apr '26

Dear colleagues, This is Sin-Myung Lee at KIAS. I hope this email finds you well. Jaeseong and I are very happy to announce the upcoming workshop "Diagrammatics for combinatorics, algebra and topology", which will be held at Sungkyunkwan university (Natural Sciences campus), Suwon, from this July 20(Mon) to 24(Fri). The central theme of the workshop is diagrammatic calculus and its applications in combinatorics, algebra, and topology. In particular, we aim to foster informal exchanges beyond the lectures, creating a space for participants to actively explore these growing fields, from basics to practical applications. Here is the list of invited speakers: Lecture series (3*1h) Ben Elias (University of Oregon) Matthew Hogancamp (Northeastern University) Linhui Shen (Michigan State University) Research talk Elise Catania (University of Minnesota - Twin Cities) Donghyun Kim (Ewha Womans University) Myungho Kim (Kyung Hee University) Hankyung Ko (Uppsala University) Mikhail Mazin (Kensas State University) Nathan Williams (University of Texas at Dallas) More information is (and will be) available on the workshop website: https://sites.google.com/view/dcat2026 If you plan on attending, please register by June 5 to stay updated and help us prepare the workshop smoothly. We would appreciate it if you could share this announcement with anyone who might be interested. We are looking forward to your participation! Best regards, Sin-Myung Lee Jaeseong Oh

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(Reminder) CART seminar announcement (Heizo Sakamoto, Apr 3 (Fri), 10:30AM)
by 이신명 01 Apr '26

01 Apr '26

Dear all, This is a gentle reminder of the CART seminar by Heizo Sakamoto (The University of Tokyo) tomorrow at 10:30 - 11:30 (in Korea time). Hope to see you at the seminar! Best regards, Sin-Myung Lee -----------------------원본 메세지----------------------- 보낸사람: "이신명"<sinmyunglee(a)kias.re.kr> 받는사람: "Mathematics Members(mathall)" <mathall(a)kias.re.kr>, cart-seminar(a)snurep.crystalline.site 보낸날짜: 2026-03-26 03:12:12 GMT +0900 (Asia/Seoul)제목: CART Seminar announcement (Heizo Sakamoto, Apr 3 (Fri), 10:30AM) Dear all, The next CART seminar is scheduled for Apr 3rd (Fri), 10:30 - 11:30 (Korea time). Speaker: Heizo Sakamoto (The University of Tokyo) Title: Classification of real and imaginary modules of quantum affine algebras in monoidal categorifications of affine cluster algebras Abstract: A finite-dimensional module $L$ over an affine quantum group is called real if the tensor product $L \otimes L$ is irreducible. It is known that for an appropriately chosen subcategory $\mathcal{C}$ of the category of finite-dimensional representations, the Grothendieck ring $K(\mathcal{C})$ has a cluster algebra structure in which cluster monomials correspond to irreducible modules (categorification of cluster algebras).In such a category $\mathcal{C}$, Hernandez-Leclerc conjectured that an irreducible module corresponds to a cluster monomial if and only if it is a real module. This conjecture remains generally open, except for cases where the categorified cluster algebra is of finite type. In this talk, I will construct subcategories that categorify cluster algebras of affine type and explain that the conjecture holds within these categories. You can join the seminar via the following Zoom link: https://kias-re-kr.zoom.us/j/86178377083?pwd=znH3EbxqjXmDCiVnv4OTl3SgJHlxva… Meeting ID: 861 7837 7083 Password: 172764 Please feel free to forward this to anyone who might be interested. You can check out further information on CART seminar on our website (https://sites.google.com/view/cart-kias/). Looking forward to seeing you at the seminar! Best regards, Sin-Myung Lee

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