Department Seminars & Colloquia




2014-06
Sun Mon Tue Wed Thu Fri Sat
1 2 2 3 4 5 1 6 7
8 9 1 10 11 12 1 13 7 14 4
15 16 17 18 19 20 21
22 23 2 24 1 25 1 26 1 27 3 28 4
29 30 1          
2014-07
Sun Mon Tue Wed Thu Fri Sat
    1 1 2 1 3 2 4 1 5
6 7 1 8 9 10 11 12 4
13 14 15 2 16 17 1 18 19
20 21 22 2 23 2 24 3 25 26 4
27 28 29 4 30 1 31    

When you're logged in, you can subscribe seminars via e-mail

 We use the results of the previous talk. Developing a mass formula for the space of binary quartic forms, and using a squarefree sieve, we show that the average size of the 2-Selmer groups of elliptic curves is 3. This yields an upper bound of 1.5 on the average rank of elliptic curves. This is joint work with ManjulBhargava

Host: 정준혁     To be announced     2014-07-23 16:54:16

Lecture 3

Date: 11:00, July 29, 2014

▶ Place: E2, Room 3221

▶ Speaker: Inwon Kim(UCLA)

▶ Title: Quasi-static evolution and congested crowd motion

▶ Abstract: In this talk we investigate the relationship between Hele-Shaw evolution with a drift and a transport equation with a drift potential, where the density is transported with a constraint on its maximum. The latter model, in a simplified setting, describes the congested crowd motion with a density constraint. When the drift potential is convex, the crowd density is likely to aggregate, and thus if the initial density starts as a patch (i.e. if it is a characteristic function of some set) then it is expected that the density evolves as a patch. We show that the evolving patch satisfies a Hele-Shaw type equation. This is joint work with Damon Alexander and Yao Yao.

Host: http://kmrs.kaist.ac.kr/activities/registration/?ee=57     English     2014-07-22 15:32:02

 ♦ Title:  Beyond Endoscopy and the Trace Formula

♦ Date : July 29, 2014 (Tuesday) / July 30, 2014 (Wednesday) / 

            August 1, 2014 (Friday) 15:00 ~ 16:00

Room : 자연과학동(E6-1) Room 1409

Speaker:  S. Ali Altug (Columbia University)

Abstract:

In his 2004 paper, "Beyond Endoscopy", Langlands proposed an approach to (ultimately) attack the general functoriality conjectures by means of the trace formula. For a (reductive algebraic) group G over a global field F and a representation r : L G GL(V ), the strategy, among other things, aims at detecting those automorphicrepresentations of G for which the L-function, L(s,   π, r), has a pole at s = 1. Langlands‘ suggestion is to use the the trace formula together with an averaging process to Capture these poles via “techniques", which may or may not be available, of analytic number theory.

In these lectures I will start by going over the aforementioned paper focusing on G =GL(2) over ,and describe the limiting procedure (and some of the dicultiesthat come with it).

I will then move on to some results (which there are not many) related to the problem, and discuss the current state of matters.

Host: 정준혁     To be announced     2014-07-23 16:49:52

Robertson and Seymour proved that graphs are well-quasi-ordered by the minor relation and the weak immersion relation. In other words, given infinitely many graphs, one graph contains another as a minor (or a weak immersion, respectively). Unlike the relation of minor and weak immersion, the topological minor relation does not well-quasi-order graphs in general. However, Robertson conjectured in the late 1980's that for every positive integer k, the topological minor relation well-quasi-orders graphs that do not contain a topological minor isomorphic to the path of length k with each edge duplicated. We will sketch the idea of our recent proof of this conjecture. In addition, we will give a structure theorem for excluding a fixed graph as a topological minor. Such structure theorem were previously obtained by Grohe and Marx and by Dvorak, but we push one of the bounds in their theorems to the optimal value. This improvement is needed for our proof of Robertson's conjecture. This work is joint with Robin Thomas.

Host: 엄상일 Andreas Holmsen 김연진     English     2014-07-24 14:00:32

 

In this talk, we adapt Bhargava's geometry-of-numbers-methods to determine the number of GL(2,Z)-orbits on integral binary quartic forms. We use this result, along with a parametrizationdue to Birch and Swinnerton-Dyer, to prove that the average rank of elliptic curves is finite.

This is joint work with Manjul Bhargava.

Host: 정준혁     To be announced     2014-07-23 16:52:15

In view of scheme language, we start from the beginning of the theory of elliptic curves and geometric modular forms, and further cover the topics about Jacobians and Galois representation as well as modularity problems.

Korean     2014-07-18 11:23:50

In this talk, we will survey the book "Arithmeticity in the theory of automorphic forms - G.Shimura (2000)".

Korean     2014-07-18 11:25:01

In this talk, we will survey the article "Modular forms and projective invariants - J.Igusa(1967)".

Korean     2014-07-18 11:28:53

In this talk, we will survey the article "Class fields over real quadratic fields and Hecke operators - G.Shimura(1972)".

Korean     2014-07-18 11:29:55

 Let X be a complex projective variety of dimension n equipped with a very ample line bundle L and a choice of valuation ν on its homogeneous coordinate ring R = R(L). Given this data, we can associate to(X, R, ν) a convex body of (real) dimension n, called the Okounkov body ∆ = ∆(X, R, ν). In many cases is in fact a rational polytope; indeed, in the case when X is a nonsingular projective toric variety, the ringR and valuation ν may be chosen so that is the Newton polytope of X. It has been proved (Anderson, Kaveh) that, in many cases of interest (such as those arising in representation theory and Schubert calculus), the Okounkov body gives rise to a toric degeneration of X; in particular, this construction simultaneously generalize many toric degenerations given in the literature (e.g. Alexeev-Brion, Caldero, Kogan-Miller).

However, Okounkov bodies (and the associated toric degenerations) depend in general on the valuationν in a subtle way which is not well-understood. In this talk we report on work in progress related to these ideas. Specifically, for a toric degeneration of a Bott-Samelson variety to a toric variety constructed by Pasquier (based on work by Grossberg and Karshon), we ask: does this toric degeneration arise as a special case of Anderson’s general construction?

To be announced     2014-07-14 09:23:58

Lecture 1

Date: 15:00~15:50, July 24, 2014

▶ Place: E2, Room 3221

Speaker: Soojung Kim(NIMS)

Title:Harnack inequality for nondivergent parabolic operators on Riemannian manifolds

Abstract: In this talk, I will discuss the Krylov-Safonov theory which is the analogue of the De Giorgi-Nash-Moser theory. In particular, I will explain the Krylov-Safonov Harnack inequality for parabolic operators on certain Riemannian manifolds. This result gives a new nondivergent proof for the Li-Yau Harnack inequality of the heat equation on manifolds with nonnegative Ricci curvature. This talk is based on a joint work with Seick Kim and Ki-Ahm Lee.

 

Lecture 2

Date: 16:00~16:50, July 24, 2014

▶ Place: E2, Room 3221

Speaker: Minha Yoo(NIMS)

Title: A drift approximation for nonlinear parabolic PDEs with oblique boundary data

Host: 권순식     English     2014-07-22 15:30:45

Lecture 1

Date: 15:00~15:50, July 24, 2014

▶ Place: E2, Room 3221

Speaker: Soojung Kim(NIMS)

Title:Harnack inequality for nondivergent parabolic operators on Riemannian manifolds

Abstract: In this talk, I will discuss the Krylov-Safonov theory which is the analogue of the De Giorgi-Nash-Moser theory. In particular, I will explain the Krylov-Safonov Harnack inequality for parabolic operators on certain Riemannian manifolds. This result gives a new nondivergent proof for the Li-Yau Harnack inequality of the heat equation on manifolds with nonnegative Ricci curvature. This talk is based on a joint work with Seick Kim and Ki-Ahm Lee.

 

Lecture 2

Date: 16:00~16:50, July 24, 2014

▶ Place: E2, Room 3221

Speaker: Minha Yoo(NIMS)

Title: A drift approximation for nonlinear parabolic PDEs with oblique boundary data

Host: 권순식     English     2014-07-22 15:30:48

This lecture is independent of the previous three lectures. Matching many mass distributions (measures) in an optimal way is an important mathematical problem and has natural applications, e.g. in economics and physics. Focusing on mathematical aspects, we will explain some of the key concepts and results. A key notion is the Monge-Kantorovich barycenter, which is itself a measure and a geometric barycenter with respect to the Monge-Kantorovich distance on the space of probability measures.

Host: 권순식     English     2014-06-25 11:00:16

We consider the unconditional uniqueness (UU) of solutions to the Cauchy problem for certain nonlinear dispersive equations on the torus. Our proof of UU is based on successive time-averaging arguments (integration by parts with respect to time variable). This approach was taken by Babin, Ilyin, and Titi (2011) for the periodic KdV equation, and has been applied to other equations such as the modified KdV equation and higher-order KdV-type equations. Recently, Guo, Kwon, and Oh (2013) obtained the optimal UU result for one-dimensional cubic NLS equation. We note that they needed to apply integration by parts infinitely many times, while for the KdV and the modified KdV cases the optimal results were obtained by finitely many applications of integration by parts. In this talk we prove UU for general NLS equations in higher dimensions and of higher (odd) degree nonlinearities, one-dimensional cubic derivative NLS, and the modified Benjamin-Ono equations by this method.

English     2014-07-15 15:17:31
Abstract: Mathematical biology is an ever more important field in the understanding of biological processes.  One of its growing subfields is mathematical modeling of infectious diseases and the evolution of pathogens, which is associated with predicting health policy effectiveness and best practices. Health policies must be developed to maximize the benefit to the public and to balance health, social, and economic considerations.  Achieving this aim requires combining molecular, individual, population, and national scales with evolutionary perspectives to understand the importance of trade-offs between disease control and the risk of pathogen replacement. Integrating mathematics, epidemiology, economics, and evolutionary biology, this interdisciplinary research generates predictions that could not be made by these disciplines alone, and has important impacts on these fields as well as for policy makers world-wide. 
To be announced     2014-07-14 10:32:43

Let X be a complex projective variety of dimension n equipped with a very ample line bundle L and a choice of valuation ν on its homogeneous coordinate ring R = R(L). Given this data, we can associate to(X, R, ν) a convex body of (real) dimension n, called the Okounkov body ∆ = ∆(X, R, ν). In many cases is in fact a rational polytope; indeed, in the case when X is a nonsingular projective toric variety, the ringR and valuation ν may be chosen so that is the Newton polytope of X. It has been proved (Anderson, Kaveh) that, in many cases of interest (such as those arising in representation theory and Schubert calculus), the Okounkov body gives rise to a toric degeneration of X; in particular, this construction simultaneously generalize many toric degenerations given in the literature (e.g. Alexeev-Brion, Caldero, Kogan-Miller).

However, Okounkov bodies (and the associated toric degenerations) depend in general on the valuationν in a subtle way which is not well-understood. In this talk we report on work in progress related to these ideas. Specifically, for a toric degeneration of a Bott-Samelson variety to a toric variety constructed by Pasquier (based on work by Grossberg and Karshon), we ask: does this toric degeneration arise as a special case of Anderson’s general construction?

 
To be announced     2014-07-14 09:21:24

 Let X be a complex projective variety of dimension n equipped with a very ample line bundle L and a choice of valuation ν on its homogeneous coordinate ring R = R(L). Given this data, we can associate to(X, R, ν) a convex body of (real) dimension n, called the Okounkov body ∆ = ∆(X, R, ν). In many cases is in fact a rational polytope; indeed, in the case when X is a nonsingular projective toric variety, the ringR and valuation ν may be chosen so that is the Newton polytope of X. It has been proved (Anderson, Kaveh) that, in many cases of interest (such as those arising in representation theory and Schubert calculus), the Okounkov body gives rise to a toric degeneration of X; in particular, this construction simultaneously generalize many toric degenerations given in the literature (e.g. Alexeev-Brion, Caldero, Kogan-Miller).

However, Okounkov bodies (and the associated toric degenerations) depend in general on the valuationν in a subtle way which is not well-understood. In this talk we report on work in progress related to these ideas. Specifically, for a toric degeneration of a Bott-Samelson variety to a toric variety constructed by Pasquier (based on work by Grossberg and Karshon), we ask: does this toric degeneration arise as a special case of Anderson’s general construction?

To be announced     2014-07-14 09:20:10

 Let X be a complex projective variety of dimension n equipped with a very ample line bundle L and a choice of valuation ν on its homogeneous coordinate ring R = R(L). Given this data, we can associate to(X, R, ν) a convex body of (real) dimension n, called the Okounkov body ∆ = ∆(X, R, ν). In many cases is in fact a rational polytope; indeed, in the case when X is a nonsingular projective toric variety, the ringR and valuation ν may be chosen so that is the Newton polytope of X. It has been proved (Anderson, Kaveh) that, in many cases of interest (such as those arising in representation theory and Schubert calculus), the Okounkov body gives rise to a toric degeneration of X; in particular, this construction simultaneously generalize many toric degenerations given in the literature (e.g. Alexeev-Brion, Caldero, Kogan-Miller).

However, Okounkov bodies (and the associated toric degenerations) depend in general on the valuationν in a subtle way which is not well-understood. In this talk we report on work in progress related to these ideas. Specifically, for a toric degeneration of a Bott-Samelson variety to a toric variety constructed by Pasquier (based on work by Grossberg and Karshon), we ask: does this toric degeneration arise as a special case of Anderson’s general construction?

To be announced     2014-07-14 09:18:49

 Current techniques for proving cases of Langlands reciprocity rely (in part) on understanding the geometry of certain local deformation spaces of Galois representations. In this talk, we will discuss a way to construct (the irreducible components of) semi-stable deformation rings in small Hodge-Tate weights of irreducible mod p representations of the absolute Galois group of Q_p.

Host: 구자경     To be announced     2014-07-08 11:16:02

In view of scheme language, we start from the beginning of the theory of elliptic curves and geometric modular forms, and further cover the topics about Jacobians and Galois representation as well as modularity problems.

Korean     2014-07-02 09:33:09

In this talk, we will survey the book "Arithmeticity in the theory of automorphic forms - G.Shimura (2000)".

Korean     2014-07-02 09:34:14

In this talk, we will survey the article "Modular forms and projective invariants - J.Igusa(1967)".

Korean     2014-07-02 09:35:10

In this talk, we will survey the article "Class fields over real quadratic fields and Hecke operators - G.Shimura(1972)".

Korean     2014-07-02 09:36:15


The choosability $chi_ell(G)$ of a graph $G$ is the minimum $k$ such that having $k$ colors available at each vertex guarantees a proper coloring.
Given a toroidal graph $G$, it is known that $chi_ell(G)leq 7$, and $chi_ell(G)=7$ if and only if $G$ contains $K_7$.
Cai, Wang, and Zhu proved that a toroidal graph $G$ without $7$-cycles is $6$-choosable, and $chi_ell(G)=6$ if and only if $G$ contains $K_6$.
They also prove that a toroidal graph $G$ without $6$-cycles is $5$-choosable, and conjecture that $chi_ell(G)=5$ if and only if $G$ contains $K_5$.
We disprove this conjecture by constructing an infinite family of non-$4$-colorable toroidal graphs with neither $K_5$ nor cycles of length at least $6$; moreover, this family of graphs is embeddable on every surface except the plane and the projective plane.
Instead, we prove the following slightly weaker statement suggested by Zhu: toroidal graphs containing neither $K^-_5$ (a $K_5$ missing one edge) nor $6$-cycles are $4$-choosable.
This is sharp in the sense that forbidding only one of the two structures does not ensure that the graph is $4$-choosable.

Host: 엄상일 Andreas Holmsen 김연진     To be announced     2014-06-16 10:59:15

In view of scheme language, we start from the beginning of the theory of elliptic curves and geometric modular forms, and further cover the topics about Jacobians and Galois representation as well as modularity problems.

Korean     2014-07-02 09:30:06

▶ Date: May 15 ~ July 3

Time: Thur. & Fri., 10:00-12:00 (Exercise session: 15:00-17:00)

▶ Description:

Many models in the sciences and engineering can be described by non-linear polynomial equations. This course offers an introduction to both theoretical and computational methods for working with such models. It is aimed at graduate students from across the mathematical sciences (Mathematics, EECS, Statistics, Physics, etc).

▶ Syllabus:

Each week of the semester is about a different topic in non-linear algebra, according to the schedule below. Auditors interested in a particular topic are welcome to attend just that week. Enrolled students will attend all weeks.

- Gröbner Basics, Elimination, Decomposing Varieties, Sparse Polynomial Systems, Semidefinite Programming, Moments and Sums of Squares,Representations and Invariants, Tensors and their Rank, Orbitopes, Maximum Likelihood, Numerical


http://kmrs.kaist.ac.kr/activities/registration/?ee=51

Host: 곽시종     English     2014-01-20 09:29:29

As an application of the methods explained in the previous two lectures, we explain a few recent results on optimal transport problems, regarding the nature of the singular set where the solution is not smooth.

Host: 권순식     English     2014-06-25 10:50:23

We explain some of the key concepts and techniques for regularity theory of the Monge-Ampere equation and optimal transport maps. This is the second lecture.

Host: 권순식     English     2014-06-25 10:48:50

Optimal transportation theory studies phenomena where mass distributions are matched in an efficient way, with respect to a given transportation cost. In the most standard case, optimal transport maps are given by the gradient of convex functions that solve the Monge-Ampere equation. We explain some of the most basic concepts and techniques for regularity theory of the Monge-Ampere equation.

Host: 권순식     English     2014-06-25 10:46:41

We introduce a discrete dynamical system on the set of partial orientations of a graph, which generalizes Gioan’s cycle-cocycle reversal system. We explain how this setup allows for a new interpretation of the linear equivalence of divisors on graphs (chip-firing), and a new proof of Baker and Norine’s combinatorial Riemann-Roch formula. Fundamental connections to the max-flow min-cut theorem will be highlighted.

Host: 엄상일 Andreas Holmsen 김연진     English     2014-06-24 09:34:59

In view of scheme language, we start from the beginning of the theory of elliptic curves and geometric modular forms, and further cover the topics about Jacobians and Galois representation as well as modularity problems.

Korean     2014-06-20 09:58:44

In this talk, we will survey the book "Arithmeticity in the theory of automorphic forms - G.Shimura (2000)".

Korean     2014-06-20 09:59:55

In this talk, we will survey the article "Modular forms and projective invariants - J.Igusa(1967)".

Korean     2014-06-20 10:00:53

In this talk, we will survey the article "Class fields over real quadratic fields and Hecke operators - G.Shimura(1972)".

Korean     2014-06-20 10:01:55

▶ Date: May 15 ~ July 3

Time: Thur. & Fri., 10:00-12:00 (Exercise session: 15:00-17:00)

▶ Description:

Many models in the sciences and engineering can be described by non-linear polynomial equations. This course offers an introduction to both theoretical and computational methods for working with such models. It is aimed at graduate students from across the mathematical sciences (Mathematics, EECS, Statistics, Physics, etc).

▶ Syllabus:

Each week of the semester is about a different topic in non-linear algebra, according to the schedule below. Auditors interested in a particular topic are welcome to attend just that week. Enrolled students will attend all weeks.

- Gröbner Basics, Elimination, Decomposing Varieties, Sparse Polynomial Systems, Semidefinite Programming, Moments and Sums of Squares,Representations and Invariants, Tensors and their Rank, Orbitopes, Maximum Likelihood, Numerical Algebraic Geometry, Nash Equilibria, Chemical Reaction Networks, Tropical Algebra


http://kmrs.kaist.ac.kr/activities/registration/?ee=51

Host: 곽시종     English     2014-01-20 09:28:23

 I will explain the basic concepts of moduli and how moduli spaces can be constructed in algebraic geometry. Exploring the moduli spaces and issues arising from their construction lead to interesting interplay of geometry, algebra and computation.

English     2014-06-17 09:28:03
Branch-width and path-width are width parameters of graphs and matroids, which measure how easy it is to decompose a graph or a matroid into a tree-like or path-like structure via separations of small order. These parameters have been used not only for designing efficient algorithms with the inputs of small branch-width or path-width, but also for proving theoretical structural theorems by providing a rough structural description. We will describe a polynomial-time algorithm to construct a path-decomposition or a branch-decomposition of width at most $k$, if it exists, for a matroid represented over a fixed finite field for fixed $k$. Our approach is based on the dynamic programming combined with the idea developed by Bodlaender for his work on tree-width of graphs. For path-width, this is a new result. For branch-width, this improves the previous work by Hlineny and Oum (Finding branch-decompositions and rank-decompositions, SIAM J. Comput., 2008) which was very indirect; their algorithm is based on the upper bound on the size of minor obstructions proved by Geelen et al. (Obstructions to branch-decompositions of matroids, JCTB, 2006) and requires testing minors for each of these obstructions. Our new algorithm does not use minor obstructions. As a corollary, for graphs, we obtain an algorithm to construct a rank-decomposition of width at most $k$ if it exists for fixed $k$. This is a joint work with Jisu Jeong (KAIST) and Eun Jung Kim (CNRS-LAMSADE).
To be announced     2014-06-17 09:36:56

▶ Date: May 15 ~ July 3

Time: Thur. & Fri., 10:00-12:00 (Exercise session: 15:00-17:00)

▶ Description:

Many models in the sciences and engineering can be described by non-linear polynomial equations. This course offers an introduction to both theoretical and computational methods for working with such models. It is aimed at graduate students from across the mathematical sciences (Mathematics, EECS, Statistics, Physics, etc).

▶ Syllabus:

Each week of the semester is about a different topic in non-linear algebra, according to the schedule below. Auditors interested in a particular topic are welcome to attend just that week. Enrolled students will attend all weeks.

- Gröbner Basics, Elimination, Decomposing Varieties, Sparse Polynomial Systems, Semidefinite Programming, Moments and Sums of Squares,Representations and Invariants, Tensors and their Rank, Orbitopes, Maximum Likelihood, Numerical Algebraic Geometry, Nash Equilibria, Chemical Reaction Networks, Tropical Algebra


http://kmrs.kaist.ac.kr/activities/registration/?ee=51

Host: 곽시종     English     2014-01-20 09:27:06

Date: 2014. 6. 25(wed)

Time: 16: 30~17: 30

Place: E6-1 Room 1409

Abstract: Hilbert's Tenth Problem asks whether there is a general algorithm to
determine, given any polynomial in several variables, whether there exists a zero
with all coordinates in Z. It was proved in the negative by Yu. Matiyasevich in
1970. In the 70's J. R. Buchi attempted to prove a similar statement for a system
of quadric equations, and he was able to relate it to the following Diophantine
problem~

Host: Andreas Schweizer     English     2014-06-05 10:32:03
I describe a construction that maps any connected graph G on three or more vertices into a larger graph, H(G), whose independence number is strictly smaller than its Lovasz number which is equal to its fractional packing number. The vertices of H(G) represent all possible events consistent with the stabilizer group of the quantum graph state associated with G, and exclusive events are adjacent. The graph H(G) corresponds to the orbit of G under local complementation. Physically, the construction translates into graph-theoretic terms the connection between a graph state and a Bell inequality maximally violated by quantum mechanics. In the context of zero-error information theory, the construction suggests a protocol achieving the maximum rate of entanglement-assisted capacity, a quantum mechanical analogue of the Shannon capacity, for each H(G). The violation of the Bell inequality is expressed by the one-shot version of this capacity being strictly larger than the independence number. The construction also describes a pseudo-telepathy game which is always won when using quantum resources but not always using classical resources. Finally we generalise the graph state to the mixed graph state and discuss how the previous construction may, therefore, be generalized. Joint work with: Cabello, Scarpa, Severini, Riera, Rahaman.
Host: 엄상일 Andreas Holmsen 김연진     English     2014-06-16 10:55:40
We develop a new paradigm to construct polytopes whose vertices can be obtained by an effective oracle in a unique fashion. Our main motivation comes from computational algebraic geometry. From this perspective these polytopes, called resultant polytopes, characterize polynomials better than total degree thus offering the fundamental representation in sparse elimination theory. We propose an output-sensitive algorithm that requires the minimum number of oracle calls, each reducing to the construction of a regular triangulation of the input set of points. Its implementation has been proven, among others, a valuable computational tool in our study of the combinatorial characterization of 4-dimensional resultant polytopes. We present the results of this study, that is, upper and lower bounds on the number of faces of 4-dimensional resultant polytopes.
Host: 엄상일 Andreas Holmsen 김연진     English     2014-06-16 10:53:56

The mixed method for elasticity with weakly symmetric stress is a successful application of the finite element exterior calculus. In this talk, we first exploit the elasticity complex approach for the problem by Arnold, Falk, Winther, and survey its follow-up research. Then we introduce an abstract framework for unified error analysis of the method. Through examples, we will show that the framework covers most previously known mixed methods and also provides new mixed methods for the problem.

To be announced     2014-06-16 17:34:08

In view of scheme language, we start from the beginning of the theory of elliptic curves and geometric modular forms, and further cover the topics about Jacobians and Galois representation as well as modularity problems.

Korean     2014-06-09 09:42:04

In this talk, we will survey the book "Arithmeticity in the theory of automorphic forms - G.Shimura (2000)".

Korean     2014-06-09 09:43:16

In this talk, we will survey the article "Modular forms and projective invariants - J.Igusa(1967)".

Korean     2014-06-09 09:45:16

In this talk, we will survey the article "Class fields over real quadratic fields and Hecke operators - G.Shimura(1972)".

Korean     2014-06-09 09:46:55

 First, we briefly review the derivation of nonlinear Schrodinger equation (NLS) from N-body linear Schrodinger equation via the cubic Gross-Pitaevskii (GP) hierarchy, which is an infinite system of coupled linear equations. Such a derivation was established by the seminal works of Erdos-Schlein-Yau. In the derivation, the most involved part is the proof of unconditional uniqueness of solutions to GP hierarchy. Recently, Chen-Hainzl-Pavlovic-Seiringer gave a simpler alternative proof of uniqueness via the quantum de Finetti theorem. Adapting this new approach, we established the unconditional uniqueness of solutions to the GP hierarchy in a low regularity Sobolev type space. Precisely, we reduce the regularity requirement down to the currently known regularity requirement for unconditional uniqueness of solutions to NLS. This is a joint work with Kenneth Taliaferro and Zhihui Xie at UT Austin.

 
Host: 권순식     To be announced     2014-06-11 10:33:33

▶ Date: May 15 ~ July 3

Time: Thur. & Fri., 10:00-12:00 (Exercise session: 15:00-17:00)

▶ Description:

Many models in the sciences and engineering can be described by non-linear polynomial equations. This course offers an introduction to both theoretical and computational methods for working with such models. It is aimed at graduate students from across the mathematical sciences (Mathematics, EECS, Statistics, Physics, etc).

▶ Syllabus:

Each week of the semester is about a different topic in non-linear algebra, according to the schedule below. Auditors interested in a particular topic are welcome to attend just that week. Enrolled students will attend all weeks.

- Gröbner Basics, Elimination, Decomposing Varieties, Sparse Polynomial Systems, Semidefinite Programming, Moments and Sums of Squares,Representations and Invariants, Tensors and their Rank, Orbitopes, Maximum Likelihood, Numerical Algebraic Geometry, Nash Equilibria, Chemical Reaction Networks, Tropical Algebra


tp://kmrs.kaist.ac.kr/activities/registration/?ee=51

Host: 곽시종     English     2014-01-20 09:22:32

 Amoebas and coamoebas are the images of varieties of the complex algebraic torus under coordinatewise logarithm and argument maps, respectively. As shadows of the original variety, they retain some of its structure. When the variety is a hypersurface, the connected components of the complements of both the amoeba and coamoeba are convex. Henriques introduced a homological generalization of convexity and proved that complements of amoebas satisfy a weak form of this higher convexity.
 In this talk, I will explain these notions and describe some of the structure of coamoebas, namely their phase limit sets and shells, and then sketch how to use this structure to show that complements of coamoebas have this higher convexity of Henriques. This is joint work with Mounir Nisse.

 

English     2014-06-09 09:49:03

 A matroid is a combinatorial notion that is a generalization of a spanning set of a vector space. To any loopless matroid, there correspond at least 3 kinds of convex polytopes: independent set polytope, base polytope, and spanning set polytope. In algebraic geometry context, base polytopes are preferred to the other two since base polytopes are closed under involution operation, and recovering the other two is easier. Moreover, in my recent research work, it turned out that base polytopes have a very special gluing property: when they glue through their codimension 2 common face, there are only finitely many cases! In this talk, I will first explain basics of matroids and base polytopes. After stating the gluing property (with a sketch of the proof), we will see how this gluing property plays its role concerning the classification of generic tropical planes of mathbb{TP}^5.

English     2014-06-09 09:50:31

After a brief introduction to  the Waring ranks and cactus ranks of polynomials, we verify additive property of ranks and cactus  ranks of polynomials which are sums of particaular types of polynomials. This work is a natural generalization of the result of Carlini, Catalisano and Geramitta concerning sum of coprime monomials.

English     2014-06-09 09:52:01

We discuss the notion of point scatterers, which is a renormalization of formal delta potentials for the Schrödinger equation in low-dimensional spaces. In particular, we will discuss the decomposition of periodic point scatterers which corresponds to Bloch's theorem of solid state physics.

Host: Prof.김용정     To be announced     2014-05-23 09:14:38

 In Abo and Wan's study of Waring's problem for systems of skew-symmetric forms several defective systems were identified.  The most interesting cases occur when a certain secant variety of a Segre-Grassmann variety does not fill its natural ambient space as expected, but is a hypersurface instead. 

In this note we study these Abo-Wan hypersurfaces by using Numerical Algebraic Geometry (Bertini) to determine their degrees. Knowing the degree we use Representation Theory to answer Problem 6.5 [AboWan13] by producing the equation of one of the hypersurfaces.  In two other cases, knowing the degree (provided by Bertini) allows us to show that an Ottaviani-type construction produces the equations of the hypersurfaces.
This is joint work with Hirotachi Abo, Noah Daleo and Jon Hauenstein.
English     2014-06-09 09:53:23

▶ Date: May 15 ~ July 3

Time: Thur. & Fri., 10:00-12:00 (Exercise session: 15:00-17:00)

▶ Description:

Many models in the sciences and engineering can be described by non-linear polynomial equations. This course offers an introduction to both theoretical and computational methods for working with such models. It is aimed at graduate students from across the mathematical sciences (Mathematics, EECS, Statistics, Physics, etc).

▶ Syllabus:

Each week of the semester is about a different topic in non-linear algebra, according to the schedule below. Auditors interested in a particular topic are welcome to attend just that week. Enrolled students will attend all weeks.

- Gröbner Basics, Elimination, Decomposing Varieties, Sparse Polynomial Systems, Semidefinite Programming, Moments and Sums of Squares,Representations and Invariants, Tensors and their Rank, Orbitopes, Maximum Likelihood, Numerical Algebraic Geometry, Nash Equilibria, Chemical Reaction Networks, Tropical Algebra


http://kmrs.kaist.ac.kr/activities/registration/?ee=51

Host: 곽시종     English     2014-01-20 09:19:06

 

An r-dynamic proper k-coloring of a graph G is a proper k-coloring of G such that every vertex in V(G) has neighbors in at least min{d(v),r} different color classes. The r-dynamic chromatic number of a graph G, written χr(G) , is the least k such that G has such a coloring. By a greedy coloring algorithm, χr(G)≤(G)+1 and the equality holds if and only if G is r-regular with diameter 2 and girth 5. We improve the bound to χr(G)≤Δ(G)+2r when δ(G)≥2rlnn . In terms of the chromatic number, we prove χr(G)≤(G) when G is k-regular with k≥(3+o(1))rlnr and show that χr(G) may exceed r1.377χ(G) when k=r. We prove χ2(G)≤χ(G)+2 when G has diameter 2, with equality only for complete bipartite graphs and the 5-cycle. Also, χ2(G)≤3χ(G) when G has diameter 3, which is sharp. This is joint work with SogolJahanbekam, Suil O, and Douglas B. West.

Host: 엄상일 Andreas Holmsen 김연진     To be announced     2014-05-28 10:01:27

▶ Date: May 15 ~ July 3

Time: Thur. & Fri., 10:00-12:00 (Exercise session: 15:00-17:00)

▶ Description:

Many models in the sciences and engineering can be described by non-linear polynomial equations. This course offers an introduction to both theoretical and computational methods for working with such models. It is aimed at graduate students from across the mathematical sciences (Mathematics, EECS, Statistics, Physics, etc).

▶ Syllabus:

Each week of the semester is about a different topic in non-linear algebra, according to the schedule below. Auditors interested in a particular topic are welcome to attend just that week. Enrolled students will attend all weeks.

- Gröbner Basics, Elimination, Decomposing Varieties, Sparse Polynomial Systems, Semidefinite Programming, Moments and Sums of Squares,Representations and Invariants, Tensors and their Rank, Orbitopes, Maximum Likelihood, Numerical Algebraic Geometry, Nash Equilibria, Chemical Reaction Networks, Tropical Algebra


tp://kmrs.kaist.ac.kr/activities/registration/?ee=51

Host: 곽시종     English     2014-01-20 09:17:48

We describe how to approximate, in quasi-polynomial time, the largest independent set of polygons, in a given set of polygons. Our algorithm works by extending the result of Adamaszek and Wiese [AW13, AW14] to polygons of arbitrary complexity. Surprisingly, the algorithm also works for computing the largest subset of the given set of polygons that has some sparsity condition. For example, we show that one can approximate the largest subset of polygons, such that the intersection graph of the subset does not contain a cycle of length 4 (i.e., K2,2). To appear in SoCG 2014.

 
Host: 엄상일, Andreas Holmsen, 김연진     English     2014-05-28 09:58:33

In recent year methods based on nonparametric estimation detection is more popular in signal processing community for estimating detecting the signal function from noisy degraded measurement. This is due to localized estimation. Recent approaches to processing and restoration of images and video brought together several powerful data-adaptive methods from different field of work. Examples include Moving Least Square (from computer graphics), the Bilateral Filter and Anisotropic Diffusion (from computer vision), Functional Gradient Decent, Kernel Regression and Iterative scaling (from Statistics).

In this talk we discussed basic of nonparametric estimation of density and distribution function followed by the class of robust nonparametric methods which are ideally suited for the reconstruction of signals and images ( in general function) form noise - corrupted and sparse or irregularly sampled data. As the framework of nonparametric the methods do not depend on strong assumption about noise; and it is applicable to a wide variety of problems. In this talk, we consider image denoising and deblurring in nonparametric framework.

Host: Prof.김성호     English     2014-05-29 17:45:14