Matematiikan ja systeemianalyysin laitos

Ajankohtaista

Esitelmiä, seminaareja ja väitöksiä

* Seuraavan viikon tapahtumat merkitty tähdellä

Pihla Karanko
Protocol verification in Tamarin in an access sharing application
* Wednesday 25 July 2018,   15:15,   M3 (M234)
I study the use of formal methods in protocol verification, in particular Tamarin language. Tamarin (https://tamarin-prover.github.io) is an automated symbolic verification tool for security protocols. It allows you to specify a protocol and its security properties using so called facts, rewrite rules and lemmas. You can then use it to check the validity of the security properties. In the talk I explain the theory and syntax of Tamarin and show how to use it to specify and validate a part of an access protocol. I work for a company called Bitwards that provides access sharing software for electronic locks and the protocol I am going to present is part of their access sharing system that we want to formally validate. MSc thesis presentation. Thesis work is carried out at Bitwards. Advisor Chris Brzuska, supervisor Camilla Hollanti.
ANTA seminar

Augusto Gerolin (University of Jyväskylä)
TBA
Wednesday 03 October 2018,   12:15,   M3 (M234)
Seminar on Analysis and Geometry

Past events

Kanditöiden aihe-esittelyt, sessio 2
Tuesday 19 June 2018,   14:30,   M3 (M234)

Kanditöiden aihe-esittelyt, sessio 1
Tuesday 19 June 2018,   13:00,   M3 (M234)

Leo Tuhkanen
Differentiaaliyhtälöiden visualisointi verkko-opetuksessa
Monday 11 June 2018,   10:15,   M2 (M233)
Diplomityöesitelmä

Joonas Laukka (kandiesitelmä)
Satunnaiskävelyt ja niiden kasvattamat puut
Friday 08 June 2018,   14:00,   M3 (M234)

Departmental meeting
Tuesday 29 May 2018,   14:15,   Coffee room

Lauri Nyman (kandiesitelmä)
Binääristen luokitteluongelmien ratkaisu hypoteesitestauksen menetelmin
Monday 28 May 2018,   11:15,   M3 (M234)

Timo Takala (kandiesitelmä)
Elliptisen osittaisdifferentiaaliyhtälön heikko ratkaisu
Monday 28 May 2018,   10:15,   M3 (M234)

Ferenc Szöllösi (Aalto - Department of Communications and Networking )
Constructions of maximum few-distance sets
Wednesday 23 May 2018,   15:15,   M2 (M233)
Abstract: A finite set of distinct vectors X in the d-dimensional Euclidean space is called an s-distance set, if the set of mutual distances between distinct elements of X has cardinality exactly s. In this talk I will present a computer-aided approach for construction and classification of s-distances for small parameter values. In particular, I will discuss the largest 3-distance set in dimension 4.
ANTA seminar

Vedran Krčadinac (University of Zagreb)
Extensions of quasi-symmetric designs
Wednesday 16 May 2018,   15:15,   M2 (M233)
Let $D$ be a t-(v,k,\lambda) design. If there is a (t+1)-(v+1,k+1,\lambda) design E such that the derived design with respect to some point is D, then E is called an extension of D and D is called extendable. In 1973, P. Cameron classified the extendable symmetric designs. In this talk we shall look at extensions of quasi-symmetric designs. Although no parametric classification is in sight, there is a known infinite family and several sporadic examples. There are also numerous parameter sets for which extensions seem feasible, but it is not known whether the designs and their extensions exist.
ANTA seminar

Lauri Oksanen (University College London)
Teaching Demonstration
Wednesday 16 May 2018,   09:30,   M2 (M233)
Least squares problem/Numerical linear algebra

Vanni Noferini (University of Essex)
Teaching Demonstration
Wednesday 16 May 2018,   09:00,   M2 (M233)
Least squares problem/Numerical linear algebra

Jilu Wang (Florida State University)
Teaching Demonstration
Tuesday 15 May 2018,   09:30,   M1 (M232)
Least squares problem/Numerical linear algebra

Prof. Clément Hongler
Statistical Field Theory and the Ising Model
Tuesday 24 April 2018,   15:15,   D
The developments of statistical mechanics and of quantum field theory are among the major achievements of 20th century's science. In the second half of the century, these two subjects started to converge, resulting in some of the most remarkable successes of mathematical physics. At the heart of this convergence lies the conjecture that critical lattice models are connected, in the continuous limit, to conformally symmetric field theories. This conjecture has led to much insight into the nature of phase transitions and to beautiful formulae describing lattice models, which have remained unproven for decades. In this talk, I will focus on the planar Ising model, perhaps the most studied lattice model, whose investigation has initiated much of the research in statistical mechanics. I will explain how, in the last ten years, we have developed tools to understand mathematically the emerging conformal symmetry of the model, and the connections with quantum field theory. This has led one to the proof of celebrated conjectures for the Ising correlations and for the description of the emerging random geometry. I will then explain how these tools have then yielded a rigorous formulation of the field theory describing this model, allowing one to make mathematical sense of the seminal ideas at the root of the subject of conformal field theory.
Colloquim

Changsun Choi (Helsinki)
On the Lebesgue space of vector measures
Friday 20 April 2018,   15:15,   Kumpula Exactum C124
The Bochner integral, the integral of vector valued functions with respect to a measure, is well known. What if we integrate scalar functions with respect to a vector measure? In this talk we consider the Lebesgue space L^1(G) of scalar functions which are integrable with respect to a vector measure G in the sense of D. R. Lewis. First, we investigate simpler conditions on a scalarly integrable function f that guarantee f in L^1(G) Next, when a new vector measure F is obtained via the integral F(E)=/int_E f dG, we show that certain properties of the vector measure G are inherited to F; for instance, relative compactness or convexity of the range of vector measures. Along the presentation some of basic properties of vector measures will be explained.
Harmonic analysis and PDE seminar

Matias Vestberg (Aalto)
Local Boundedness of Shallow Water
Friday 20 April 2018,   14:15,   Kumpula Exactum C124
We show that weak solutions of the Diffusive Shallow Water Equation are locally bounded, and obtain an explicit estimate for the essential supremum. Also continuity w.r.t. time is considered. Joint work with Thomas Singer.
Harmonic analysis and PDE seminar

Gleb Pogudin (Courant Institute, New York University)
Teaching demonstration
Friday 13 April 2018,   15:30,   M1 (M232)

Katharina Jochemko (KTH)
Teaching demonstration
Friday 13 April 2018,   13:30,   M1 (M232)

Gleb Pogudin
Elimination for differential and difference equations
Friday 13 April 2018,   11:15,   M1 (M232)

Katharina Jochemko
Positivity and unimodality questions in geometric combinatorics
Friday 13 April 2018,   09:00,   M1 (M232)

Liam Solus
Geometry, Combinatorics, and the Shape of a Distribution
Thursday 12 April 2018,   15:15,   M1 (M232)

Mateusz Michalek
Algebraic Phylogenetics
Thursday 12 April 2018,   13:00,   M240

Liam Solus (KTH)
Teaching demonstration
Thursday 12 April 2018,   09:35,   M1 (M232)

Mateusz Michalek (Max Planck Institute, Leipzig)
Teaching demonstration
Thursday 12 April 2018,   09:00,   M1 (M232)

Amal Attouchi (University of Jyväskylä)
Qualitative properties of viscosity solutions of a degenerate or singular parabolic equation in non-divergence form.
Wednesday 11 April 2018,   12:15,   M3 (M234)
Seminar on analysis and geometry

Emma-Karoliina Kurki
Homogenisation of the Stokes equations in a perforated domain by the energy decomposition method (Master thesis talk)
Thursday 29 March 2018,   13:15,   M237

Augusto Gerolin (University of Jyväskylä)
Optimal Transport meets Density Functional Theory
Wednesday 28 March 2018,   12:15,   M3 (M234)
Seminar on analysis and geometry

STACK-koulutus / STACK-training
Wednesday 28 March 2018,   10:15,   Y342a
Koulutustilaisuus automaattisesti tarkastettavien STACK-tehtävien laadinnasta Aalto-yliopiston matematiikan laitoksen henkilökunnalle. Tilaisuudessa tutustutaan tehtävien laadinnan perusteisiin kuten käytettyyn syntaksiin, notaatioihin jne. -- A training session on the creation of STACK exercises for Aalto University Math Department staff. During the session we will cover the basics, i.e. how exercises are created, the used syntax, notation, etc.

Prof. Heikki Haario (Lappeenranta University of Technology)
Statistical invariance in chaos and random patterns
Tuesday 27 March 2018,   15:15,   D
We apply a recent statistical algorithm, originally developed for parameter estimation of chaotic dynamical systems, to identify model parameters of reaction-diffusion systems by ensembles of Turing patterns created by unknown random initial values. The method is tested using the Fitzhugh-Nagumo model, a classical model of excitable media. It is shown that the approach is able to detect small but systematic structural changes of patterns, practically impossible to distinguish by naked eye.
Colloquim

Study Group
Moduli of families of curves
Tuesday 27 March 2018,   12:15,   M2 (M233)

Ekaterina Kruglov
Pointwise Convergence of Jacobi Polynomials
Monday 26 March 2018,   13:00,   M2 (M233)
Diplomityöesitelmä / Hakula

Antti Vähäkangas (Jyväskylä)
Self-improvement results for two-measure Poincaré inequalities
Friday 23 March 2018,   15:15,   M3 (M234)
Harmonic analysis and PDE seminar

Henri Martikainen (Helsinki)
Boundedness properties of bilinear bi-parameter singular integrals
Friday 23 March 2018,   14:15,   M3 (M234)
Harmonic analysis and PDE seminar

Professor Hans-Georg Weigand (University of Würzburg)
Gottfried Wilhelm Leibniz (1646-1716) and the Invention of Calculus
Thursday 22 March 2018,   13:15,   U149 U6
Rasila/A!OLE

Sylvester Eriksson-Bique (UCLA)
A New proof of Keith-Zhong self improvement
Wednesday 21 March 2018,   12:15,   M3 (M234)
I will discuss how some curve based ideas lead to a fairly simple proof of Keith-Zhong self improvement with also simple bounds for the quantity of self improvement. Additionally I will discuss briefly some ways these ideas work in other contexts.
Seminar on analysis and geometry

Teaching meeting
Tuesday 20 March 2018,   14:15,   Coffee room

Study Group
Moduli of families of curves
Tuesday 20 March 2018,   12:15,   M2 (M233)

Ari-Pekka Perkkiö (LMU Munich)
Optional projection in duality
Monday 19 March 2018,   15:15,   M203
In this talks we characterize topological duals of Frechet spaces of stochastic processes. This is done by analyzing the optional projection on spaces of cadlag processes whose pathwise supremum norm belongs to a given Frechet space of random variables. We employ functional analytic arguments that unify various results in the duality theory of stochastic processes and also yields new ones of both practical and theoretical interest. In particular, we find an explicit characterization of dual of the Banach space of adapted cadlag processes of class (D). When specialized to regular processes, we obtain a simple proof of a result of Bismut on projections of continuous processes.
Aalto Stochastics & Statistics Seminar

Ilmari Kangasniemi (University of Helsinki)
A sharp uniformly quasiregular Bonk-Heinonen theorem
Wednesday 14 March 2018,   12:15,   M3 (M234)
Bonk and Heinonen have proved that if a closed connected oriented Riemannian n-manifold M receives a non-constant K-quasiregular map from R^n, there exists a bound C(n,K) on the dimension of the cohomology ring of M. It is conjectured that the sharp bound is actually 2^n, with the maximal example given by the n-torus. In this talk, a sharp counterpart of the theorem is presented for uniformly quasiregular maps. Furthermore, the proof of this counterpart theorem also yields a result on the Julia sets of uniformly quasiregular maps, which raises a question about an even stronger limitation. The talk is a continuation of my last talk in Fall 2017, but can be followed without having heard the previous one.
Seminar on analysis and geometry

Study Group
Moduli of families of curves
Tuesday 13 March 2018,   12:15,   M2 (M233)

Laura Jakobsson
The Category of Cellular Resolutions
Saturday 10 March 2018,   12:15,   Y229c
Workshop on Algebraic Combinatorics

Riikka Kangaslampi
Discrete Ricci curvatures
Saturday 10 March 2018,   11:15,   Y229c
We discuss discrete Ricci curvatures on graphs. We define Ollivier-Ricci curvature notion, give motivation to the definition and present a few examples. We also briefly mention the idea behind Bakry-Emery curvature notion. Then we present a few recent results on Ollivier-Ricci and Bakry-Emery curvatures, like classification results for non-negatively curved graphs and based on them, the non-existence of non-positively curved expanders. Joint work with D.Cushing, N.Peyerimhoff, S.Liu, V.Lipiäinen, Y.Lin, L.Lu, G.W.Stagg and S.-T.Yau.
Workshop on Algebraic Combinatorics

Patrik Noren
Discrete Morse theory and tropical convexity
Saturday 10 March 2018,   10:15,   Y229c
Tropical convexity has recently been used to prove results in commutative algebra. In particular it has been used to construct cellular resolutions of large classes of monomial ideals. In some important cases the classes of ideals have restrictions that are in some sense unnatural and it has been conjectured that the construction work in a larger setting where tropical methods will not work. We give two examples where discrete Morse theory can be used to prove the more general case.
Workshop on Algebraic Combinatorics

Milo Orlich
Algebraic invariants of Booth-Lueker graphs and their edge ideals
Friday 09 March 2018,   15:15,   Y229c
To understand modules over polynomial rings, we can study some of their homological invariants: the Betti numbers and the more recently introduced Boij-Söderberg coefficients. Whereas there are algorithms to compute these invariants, there are no general formulas for them. We will see that there are such formulas for the Booth-Lueker ideal associated to a graph.
Workshop on Algebraic Combinatorics

Alexander Engström
Transfer-Matrix Methods meet Ehrhart Theory
Friday 09 March 2018,   14:15,   Y229c
Workshop on Algebraic Combinatorics

Emanuele Ventura
Tight tensors
Friday 09 March 2018,   13:15,   Y229c
To study the complexity of the matrix multiplication tensor, Strassen introduced a class of tensors that vastly generalize it, the tight tensors. Tight tensors are essentially tensors with a ”good” positive dimensional symmetry group. In this talk, I will present some examples of tight tensors along with some of their combinatorial and geometric properties. This is joint work with A. Conner, JM Landsberg, and Y. Wang.
Workshop on Algebraic Combinatorics

Sebastian Schwarzacher (University of Bonn)
Parabolic non-linear Calderon Zygmund covering and the porous medium equation
Wednesday 07 March 2018,   12:15,   M3 (M234)
The talk is about some recent results in collaboration with U. Gianazza from Pavia. We introduce a technique that implies that the gradient of solutions to degenerate and singular parabolic equations of porous medium-type satisfy higher integrability properties. The core is to modify the by-now classical Gehring lemma by introducing an intrinsic Calderon-Zygmund covering argument.
Seminar on analysis and geometry

Departmental meeting
Tuesday 06 March 2018,   14:15,   Coffee room

Study Group
Moduli of families of curves
Tuesday 06 March 2018,   12:15,   M2 (M233)

Lassi Helanti (Diploma thesis talk)
Schauder estimates
Friday 02 March 2018,   14:15,   M3 (M234)

Pekka Alestalo (Aalto University)
Extension of bilipschitz maps: A survey
Wednesday 28 February 2018,   12:15,   M3 (M234)
Seminar on analysis and geometry

Acadamy Research Fellow Kaisa Matomäki (University of Turku)
Correlations of arithmetic functions
Tuesday 27 February 2018,   15:15,   D
Important arithmetic functions include the von Mangoldt function $\Lambda(n)$ which is essentially a weighted characteristic function of the primes, and the Liouville function $\lambda(n)$ which is $-1$ or $+1$ depending on whether $n$ has an odd or even number of prime factors. Mean values of these functions have been known for more than a century and in both cases the asymptotic evaluation of the mean value is equivalent to the prime number theorem which says that the number of primes up to $x$ is $x/\log x$. Much more difficult question is whether there is correlation between consecutive values of $\lambda(n)$ or between $\Lambda(n)$ and $\Lambda(n+2)$. Such questions are closely related to the notoriously difficult twin prime conjecture which claims that there are infinitely many primes $p$ such that $p+2$ is also prime. Though the twin prime conjecture is still a distant goal, there has been some recent progress on this sort of correlations which I will discuss.
Colloquim

Nick Lindemulder (TU Delft)
A randomized difference norm for vector-valued Bessel potential spaces
Friday 23 February 2018,   15:15,   Kumpula Exactum C124
In this talk we discuss a randomized difference norm characterization for Bessel potential spaces in the UMD Banach space-valued setting. The main ingredients are R-boundedness results for Fourier multiplier operators, which are of independent interest. As an application we characterize the pointwise multiplier property of the indicator function of the half-space on these spaces. All results are proved in the setting of weighted spaces
Harmonic analysis and PDE seminar

Pekka Lehtelä (Aalto)
Obstacle problem for the porous medium equation
Friday 23 February 2018,   14:15,   Kumpula Exactum C124
Harmonic analysis and PDE seminar

Jung-Tae Park (Seoul National University)
Global gradient estimates for measure data problems in nonsmooth domains
Wednesday 21 February 2018,   12:15,   M3 (M234)
Seminar on analysis and geometry

Stavros Evdoridis, Antti Rasila
Conformal geometry study group (first meeting)
Tuesday 20 February 2018,   12:15,   Y225a (Riihi)
Further information
The goal of the meeting is to study the book Moduli of Families of Curves for Conformal and Quasiconformal Mappings, by Alexander Vasil'ev. Everybody interested in geometric complex analysis is welcome.
Conformal geometry study group

Marzieh Arabi Kakavand
Cyclic Subspace Codes
Wednesday 14 February 2018,   15:15,   M205
Subspaces codes are of great interest due to their applications to multiple sender-receiver schemes. As in classical algebraic coding theory, one of the most important research area in random network coding is the existence and construction of subspace codes and cyclic subspace codes with good parameters. Recently Etzion et al. have presented a method for constructing cyclic subspace codes, which includes some special kind of linearized polynomials, namely subspaces polynomials and also Frobenius mappings. This new approach, especially the representation of some families of subspace codes via polynomials, is a very interesting contribution to this area of research. Some of the research on cyclic subspace codes, it becomes relevant the following conjecture. Conjecture: For every positive integers n, k such that k < n/2, there exists a subspace cyclic code of size (q^n-1)/(q-1) in G_q(n,k) and minimum distance 2k-2. For a fixed natural number k<= n let G_q(n,k) denote the set of all subspaces of F_q^n of dimension k and we call it the k-Grassmannian. I will talk about the efforts that were done for solving this Conjecture.
ANTA seminar

Tuomas Orponen (University of Helsinki)
On uniformly rectifiable surfaces in the Heisenberg group
Wednesday 14 February 2018,   12:15,   M3 (M234)
Abstract: A closed set in a metric space X satisfies Condition B, if for all x in S and r > 0, there exist two balls, which are contained in B(x,r), have radii comparable to r, and are contained in two distinct components of X \ S. In R^n, an (n - 1)-regular set satisfying Condition B is known to contain big pieces of Lipschitz graphs, by a result of G. David. I discuss joint work with K. Fässler and S. Rigot, where we prove an analogue of the result for 3-regular sets in the first Heisenberg group.
Seminar on analysis and geometry

Stanislav Nagy (Charles University)
Unified approach to the theory of functional data depth
Wednesday 07 February 2018,   17:00,   M3 (M234)
Depth has become a quite popular concept in functional data analysis. In the talk we discuss its general framework. We show that most known functional depths can be classified into few groups, within which they share similar theoretical properties. We focus on uniform consistency results for the sample versions of these functionals, and demonstrate that some well-known approaches to depth assessment are hardly theoretically adequate.
Workshop on statistical depths and functional data analysis

Joni Virta (Aalto SCI)
Independent component analysis of multivariate functional data
Wednesday 07 February 2018,   16:15,   M3 (M234)
We extend a classic method of independent component analysis, the fourth order blind identification (FOBI), to vector-valued functional data. The use of multivariate instead of univariate functions allows for natural definitions for both the marginals of a random function and their mutual independence. Our model assumes that the observed functions are mixtures of latent independent functions residing in suitable Hilbert spaces, mixed with a bounded linear operator from the product space to itself. To enable the inversion of the covariance operator we make the assumption that the dependency between the mixed component functions lies in a finite-dimensional subspace. In this subspace we define fourth cross-cumulant operators and use them to construct a novel Fisher consistent method for solving the independent component problem for vector-valued functions. Finally, both simulations and an application to hand gesture data set are used to demonstrate the advantages of the proposed method over its closest competitors.
Workshop on statistical depths and functional data analysis

Sami Helander (Aalto SCI)
On typicality of functional observations
Wednesday 07 February 2018,   15:00,   M3 (M234)
Most of the functional depth approaches presented in the literature are solely interested in the -pointwise- centrality of the observations as a measure of (global) centrality. As a result, they are missing some important features inherent to functional data such as variation in shape, roughness or range. Thus, due to the richness of functional data, we opt to talk about typicality rather than centrality of an observation. We discuss assessing typicality of functional observations. Moreover, we provide a new concept of depth for functional data. It is based on a new multivariate Pareto depth applied after mapping the functional observations to a vector of statistics of interest. These quantities allow incorporating the inherent features of the distribution, such as shape or roughness. In particular, in contrast to most existing functional depths, the method is not limited to centrality only. Properties of the new depth are explored and the benefits of a flexible choice of features are illustrated.
Workshop on statistical depths and functional data analysis

Germain Van Bever (Université libre de Bruxelles)
Halfspace depths for scatter, concentration and shape matrices
Wednesday 07 February 2018,   14:15,   M3 (M234)
We propose halfspace depth concepts for scatter, concentration and shape matrices. For scatter matrices, our concept extends the one from Chen, Gao and Ren (2015) to the non-centered case, and is in the same spirit as the one in Zhang (2002). Rather than focusing, as in these earlier works, on deepest scatter matrices, we thoroughly investigate the properties of the proposed depth and of the corresponding depth regions. We do so under minimal assumptions and, in particular, we do not restrict to elliptical distributions nor to absolutely continuous distributions. Interestingly, fully understanding scatter halfspace depth requires considering different geometries/topologies on the space of scatter matrices. We also discuss, in the spirit of Zuo and Serfling (2000), the structural properties a scatter depth should satisfy, and investigate whether or not these are met by the proposed depth. As mentioned above, companion concepts of depth for concentration matrices and shape matrices are also proposed and studied.
Workshop on statistical depths and functional data analysis

Ratan Kumar Giri (National Institute of Technology Rourkela, India)
Reduced limit corresponding to the second order semilinear elliptic PDEs with measure data
Wednesday 07 February 2018,   12:15,   M3 (M234)
Seminar on analysis and geometry

Teaching meeting
Tuesday 06 February 2018,   14:15,   Coffee room

Pekka Pankka (University of Helsinki )
Deformation of cubical Alexander maps
Wednesday 31 January 2018,   12:15,   M3 (M234)
I will discuss parts of a recent work with Jang-Mei Wu related to extension theory of spatial quasiregular mappings. The talk is mostly on the topological/combinatorial aspects of the extension theory and I will focus on a certain class PL branched covers, called cubical Alexander maps, and their branched cover homotopy theory following Rickman's ideas. As a particular result I will discuss a version of the Hopf theorem in this category: Two cubical and cubically shellable Alexander maps of an n-sphere are branched cover homotopic if and if they have the same degree.
Seminar on Analysis and Geometry

Prof. Petteri Kaski (Aalto Univeristy)
Proofs and computation
Tuesday 30 January 2018,   15:15,   D
A highly desirable property for a mathematical proof is that its correctness is easier to verify than it is to prepare the proof from scratch. One possibility to quantify such "ease of verification" is to view the tasks of preparing and verifying a proof from a computational perspective and in terms of the computational resources employed for a task. Indeed, such proof-system-based characterizations are in many ways fundamental to our current understanding of computational complexity and complexity classes such as P, NP, and beyond. This talk explores classical and recent work on proof systems for computational problems, including some of our own recent work involving proof systems that tolerate adversarial errors during proof preparation.
Colloquim

Teemu Murtola (University of Tampere, Faculty of Medicine and Life Sciences)
Benefits of cholesterol-lowering statins in prostate cancer
Tuesday 30 January 2018,   10:00,   M3 (M234)
Many commonly used drugs target intracellular signaling pathways that have importance in carcinogenesis and progression of cancer. One example is the mevalonate pathway which is targeted by cholesterol-lowering statin drugs. Examining possible anticancer effects of drug groups established for other indications requires comprehensive multidisciplinary approach including epidemiological studies to explore associations with cancer risk and prognosis, experimental laboratory studies to elucidate possible anticancer mechanisms and ultimately clinical trials to test for clinical benefit. This lecture describes such project testing statins' effects against prostate cancer.
Aalto Stochastics and Statistics Seminar

Jari Miettinen (Aalto ELEC)
Independent component analysis for graph data using graph-autocorrelation matrices
Monday 29 January 2018,   15:15,   M3 (M234)
The first independent component analysis estimators were designed for i.i.d. data, and they assume that at most one of the independent components has Gaussian density. Afterwards, methods have been developed for data with dependencies between the observations, including for example time series and spatial data. Those methods utilize solely or partially the structure of the data. For the most general case, graph data, Blochl et al. introduced an ICA estimator called GraDe (graph decorrelation) which uses approximate joint diagonalization of graph-autocorrelation matrices. GraDe contains the best-known time series and spatial methods as special cases. The structure of the graph is given in an adjacency matrix which is to be known or estimated prior to performing the ICA task. As one example in our paper on the effects of adjacency matrix estimation errors in graph signal processing, we study how the GraDe method is affected by misspecification of the adjacency matrix, using both theoretical and simulation results.
Aalto Stochastics and Statistics Seminar

Stefan Sturm (Universität Salzburg)
Regularity of weak solutions and supersolutions to the porous medium equation
Friday 26 January 2018,   15:15,   M3 (M234)
Harmonic analysis and PDE seminar

Paolo Marcellini (Università di Firenze)
Elliptic and parabolic equations under general and p,q growth conditions
Friday 26 January 2018,   14:15,   M3 (M234)
Harmonic analysis and PDE seminar

Jouni Parkkonen (University of Jyväskylä)
Equidistribution and counting in negatively curved spaces
Wednesday 24 January 2018,   12:15,   M3 (M234)
Seminar on analysis and geometry

Mindaugas Bloznelis (U Vilnius)
Local probabilities of randomly stopped sums of power law lattice random variables and clustering patterns in complex networks
Monday 22 January 2018,   15:15,   M3 (M234)
Let $X_1$ and $N$ be non-negative integer valued power law random variables. For a randomly stopped sum $S_N=X_1+\cdots+X_N$ of independent and identically distributed copies of $X_1$ we establish a first order asymptotics of the local probabilities $P(S_N=t)$ as $t\to+\infty$. Using this result we show the $k^{-\delta}$, $0\le \delta\le 1$ scaling of the local clustering coefficient (of a randomly selected vertex of degree $k$) in a power law affiliation network. http://arxiv.org/abs/1801.01035
Aalto Stochastics & Statistics Seminar

Prof. Ralph L. Keeney
Value-Focused Decisions
Thursday 18 January 2018,   16:00,   hall E
Further information
Aalto Systems Forum

Laia Amoros Carafi
Arithmetic of quaternion algebras and Shimura curves
Wednesday 17 January 2018,   15:15,   M205
I will introduce quaternion algebras and show how one can construct Shimura curves with them. Quaternion algebras arise as a natural generalisation of matrix algebras. In the same way that the action of SL(2,Q) (and of all its congruence subgroups) on the complex upper half-plane give us modular curves, the action of certain subgroups of quaternion algebras will give us some algebraic structure (the so called Shimura curves). After this introduction I will explain some applications of Shimura curves and sketch how one can compute the bad reduction of certain families Shimura curves, based on a joint work with P. Milione.
ANTA seminar

Timmavajjula Venkata Karthik (IISER)
Symmetric group action on the cohomology algebra of configuration space of particles in R^3
Wednesday 20 December 2017,   14:15,   M3 (M234)
We first give a brief introduction to the physics of the problem followed by descriptions of the cohomology algebra(H_n^∗) and the action of the symmetric group Σ_n on it, accompanied by computations for a few values of n. Then we get to our main aim which is: Determining the multiplicity(μ_{k,d,n}) of the k:th hook representation of S_n in H_n^d, by describing the Hook representations, Lehrer’s generating function method for computing characters of both representations of symmetric group on the algebra as well as that of Hook representations. Finally, using combinatorial techniques such as Moreau's Necklace counting function and the cyclotomic identity, we determine μ_{0,d,n}, μ_{n−1,d,n} and finally the general case μ_{k,d,n}.
Kytölä / Radnell

Eveliina Peltola (University of Geneva)
Multiple SLEs for \kappa \leq 4
Tuesday 19 December 2017,   15:45,   U3
Further information
Stochastic Sauna 2017 / Kytölä, Leskelä, Radnell, Webb

Mikko Pakkanen (Imperial College London)
Rough volatility: towards efficient Monte Carlo pricing and calibration
Tuesday 19 December 2017,   14:30,   U3
Further information
Stochastic Sauna 2017 / Kytölä, Leskelä, Radnell, Webb

Roland Bauerschmidt (University of Cambridge)
Eigenvectors and spectral measure of random regular graphs of fixed degree
Tuesday 19 December 2017,   13:30,   U3
Further information
Stochastic Sauna 2017 / Kytölä, Leskelä, Radnell, Webb

Dr David Cushing (Durham University)
Ollivier-Ricci idleness functions of graphs
Tuesday 19 December 2017,   12:15,   M2 (M233)
Ricci curvature plays a very important role in the study of Riemannian manifolds. In the discrete setting of graphs, there is very active recent research on various types of Ricci curvature notions and their applications. One such notion on graphs is the Ollivier-Ricci curvature. This notion has recently had many applications, ranging from modelling cancer growth to modelling WiFi connections. This stems from this curvature notion being a way to quantify local connectedness. Ollivier-Ricci curvature is motivated by optimal transport. I will begin by giving a crash course on optimal transport theory and defining Ollivier-Ricci curvature on graphs. Then we will study the Ollivier-Ricci curvature of graphs as a function of the chosen idleness. We show that this idleness function is concave and piecewise linear with at most 3 linear parts, with at most 2 linear parts in the case of a regular graph. We then apply our result to show that the idleness function of the Cartesian product of two regular graphs is completely determined by the idleness functions of the factors.
Discrete geometry seminar / Kangaslampi

Lauri Viitasaari (University of Helsinki)
On model fitting and estimation of stationary processes
Tuesday 19 December 2017,   11:15,   U3
Further information
Stochastic Sauna 2017 / Kytölä, Leskelä, Radnell, Webb

Aristides Gionis (Aalto University)
Mining temporal networks
Tuesday 19 December 2017,   10:15,   U3
Further information
Stochastic Sauna 2017 / Kytölä, Leskelä, Radnell, Webb

Prof. Felix Schwenninger (University of Hamburg)
Around the inverse generator problem
Tuesday 12 December 2017,   14:15,   M2 (M233)

Oscar Kivinen (UC Davis)
Hilbert schemes of singular plane curves and knot homology
Tuesday 12 December 2017,   14:15,   M3 (M234)
Conjectures of Gorsky, Oblomkov, Rasmussen, Shende and others relate the homologies of Hilbert schemes of points on plane curve singularities to homological invariants of the corresponding links. Representation-theoretic approaches to these conjectures have borne fruit in the case of torus links. I will give an overview of these conjectures and discuss how a subalgebra of the Weyl algebra acting on the homologies of the Hilbert schemes in question gives us a way to approach them, focusing on computations and simple examples.
Engström / Kytölä

Alex Karrila
Uniform spanning trees, scaling limits, and conformal invariance
Tuesday 12 December 2017,   12:05,   M205
Doctoral student talk / Engström

Joona Karjalainen
Moment-based parameter estimation in random intersection graphs
Tuesday 12 December 2017,   11:40,   M205
Doctoral student talk / Engström

Matias Heikkilä
On multivariate separating Hill estimator under estimated location and scatter
Tuesday 12 December 2017,   11:15,   M205
Doctoral student talk / Engström

Casimir Lindfors
On the degenerate two-phase Stefan problem
Friday 01 December 2017,   15:15,   M3 (M234)
Harmonic analysis and PDE seminar

Ella Tamir (Helsinki)
Constructing the Green function for a non-coercive PDE
Friday 01 December 2017,   14:15,   M3 (M234)
Harmonic analysis and PDE seminar

Prof. Kari Astala (Aalto University)
Random tilings, variational problems and the Beltrami equation.
Tuesday 28 November 2017,   15:15,   U1
Interactions between analysis and random geometry is a topical area in mathematics. In two dimensions, in particular, limit configurations of random structures often posses some conformal invariance properties, giving way to methods of geometric analysis. In this talk, based on joint work with E. Duse, I. Prause and X. Zhong, I describe our project where our goal is to apply methods of geometric analysis in describing limit configurations of random tilings, and parametrizations of the boundaries between the ordered and disordered, or liquid, limit regions. It turns out that the liquid domains carry a natural complex structure described by a quasilinear Beltrami equation, with surprising properties.
Colloquim

Taneli Luotoniemi (Aalto University)
Hyperspatial Intuitions Through Visual Props
Wednesday 22 November 2017,   12:15,   M3 (M234)
Four-dimensional space is a mathematical thought experiment of adding an extra spatial dimension perpendicular to our three dimensions of length, height and width. Originating in philosophy and mathematically formulated in geometry, the concept has evoked interpretations not only in theoretical physics and visual arts, but also in occultism and science fiction. Research on its properties is made possible by generalizing the methods acquired by studying more familiar spaces of lower dimensions. Just as 3-dimensional structures can be drawn, unfolded, sliced, photographed, or otherwise flattened onto a planar medium like paper or computer screen, these techniques can be generalized to produce 3D manifestations of various 4-dimensional structures. These objects provide a sensuous access to a provokingly counter-intuitive, but nevertheless logically consistent concept rich with scientific, historical and poetic significance.
Seminar on analysis and geometry

Joonas Pääkkönen
On an equality in wirless communications
Wednesday 15 November 2017,   15:15,   M205
In modern wireless communication systems, it is a well-known assumption that the received signal amplitude is $y = hx + n$, where $x$ is the transmitted amplitude, $h$ is the fading coefficient and $n$ is thermal receiver noise. This model has been the bedrock for deriving a myriad of mathematical results. However, it might be forgotten that this model does not always apply. In this lecture-like, rather informal talk, I will not present new results, but show from where this formula comes and under what circumstances it is reasonable.
ANTA seminar

Lauri Hitruhin (University of Helsinki)
Stretching and rotational multifractal spectra of mappings with integrable distortion
Wednesday 15 November 2017,   12:15,   M3 (M234)
Seminar on analysis and geometry

Vilma Virasjoki
Models for the Sustainable Transition of Energy Markets
Tuesday 14 November 2017,   12:15,   M205
Doctoral student talk / Engström

Edoardo Tosoni
Safety assessment of nuclear waste repositories
Tuesday 14 November 2017,   11:40,   M205
Doctoral student talk / Engström

Alessandro Mancuso
Portfolio optimization of risk management actions in safety critical systems
Tuesday 14 November 2017,   11:15,   M205
Doctoral student talk / Engström

Emil Vuorinen (Helsinki)
A representation theorem for bilinear singular integrals
Friday 10 November 2017,   15:15,   Kumpula Exactum C124
Harmonic analysis and PDE seminar

Matias Vestberg (Aalto)
An Excursion in Shallow Water
Friday 10 November 2017,   14:15,   Kumpula Exactum C124
We take a stroll in the world of shallow water dynamics as described by the diffusive wave approximation. This nonlinear parabolic PDE is used to model floods and dam breaks, and can be seen as a generalization of both the parabolic p-Laplace equation and the porous medium equation. We review results concerning local boundedness for weak solutions, and discuss in detail the fundamental solutions and their properties.
Harmonic analysis and PDE seminar

Marzieh Arabi Kakavand
On the Locality of Codeword Symbols
Wednesday 08 November 2017,   15:15,   M205
Consider a linear $[n, k, d]_q$ code $C$. The $i$th coordinate of $C$ has locality $r$, if the value at this coordinate can be recovered from accessing some $r$ other coordinates of $C$. Data storage applications require codes with low locality for information coordinates and low locality for parity coordinates. Motivated by applications to data storage, Gopalan and his collaborators (2012) introduce $(r, d)$-codes, which are systematic codes that have distance $d$ and also have the property that any information coordinate has locality $r$ or less. In this presentation, I will talk about results that are obtained on the linear codes and nonlinear codes with locality property.
ANTA seminar

Laura Venieri (University of Helsinki)
A Marstrand-type theorem for a one-dimensional family of projections in R^3
Wednesday 08 November 2017,   12:15,   M3 (M234)
Marstrand's projection theorem in R^3 states that the Hausdorff dimension of the projection of a set onto almost every line is the minimum between one and the dimension of the set. Here almost every is intended with respect to the surface measure on the sphere. In this talk I will show an improvement of the theorem based on joint work with A. Käenmäki and T. Orponen: the same conclusion holds if we replace the surface measure with the length measure on certain curves on the sphere.
Seminar on analysis and geometry

David Radnell (Aalto University)
Model of the Teichmuller space of genus-zero bordered surfaces by period maps
Wednesday 01 November 2017,   12:15,   M3 (M234)
The classical period mapping takes compact Riemann surfaces of genus g into the Siegel upper half-plane, which consists of symmetric g x g matrices with positive definite imaginary part. It is a classical fact that this map is holomorphic. We generalize the period mapping to the case of the Teichmuller space of genus-zero surfaces with n closed non-overlapping disks removed and prove it is holomorphic. The period mapping takes the Teichmuller space of this type into the direct product of the Teichmuller space of genus-zero surfaces with n punctures and a space of bounded operators on an n-fold sum of Bergman spaces of the disk. The construction relies on a generalization of the classical Grunsky operator, new extension and reflection results on quasidisks, as well as a coordinate system for the infinite-dimensional Teichmuller space inspired by conformal field theory. This talk will introduce these results which are joint work with Eric Schippers and Wolfgang Staubach. Background notions will be explained and technical details will be hidden.
Seminar on analysis and geometry

Prof. Lothar Nannen (TU Wien)
Numerical methods for resonance problems in open systems
Tuesday 31 October 2017,   15:00,   U1
Colloquim

Dissertation
Lauri Mustonen, Prof. Roland Griesmaier (Wuerzburg)
Approximations and surrogates for computational inverse boundary value problems
Friday 27 October 2017,   12:00,   M1 (M232)

Prof. Roland Griesmaier (University of Wuerzburg)
Uncertainty principles for far field patterns and applications to inverse source problems
Thursday 26 October 2017,   12:30,   M2 (M233)
Seminar on Applied Mathematics

Emil Sköldberg
The homologies of monomial ideals and incidence algebras.
Wednesday 25 October 2017,   15:15,   M2 (M233)
Given a set of monomials M ={m_1, ..., m_r} in a polynomial ring, one can form the set L of all least common multiples of subsets of M. This set is a partially ordered set, (even a lattice) ordered by divisibility. It is known that the betti numbers of the ring S/(M) can be computed as the homology of the simplicial complex of L. In the talk, I will explain how this relationship can be lifted to hold on the level of resolutions, between modules over S on one hand, and modules over the incidence algebra of L on the other hand.
ANTA seminar

Jia Huilian (Aalto Xián Jiaotong University)
Global regularity of elliptic p-Laplace equation on convex domain
Friday 20 October 2017,   15:15,   M3 (M234)
Harmonic analysis and PDE seminar

Tuomas Hytönen (Helsinki)
The matrix-weighted frontier of sharp norm inequalities
Friday 20 October 2017,   14:15,   M3 (M234)
Harmonic analysis and PDE seminar

Stavros Evdoridis
Bohr's inequality for harmonic mappings
Wednesday 18 October 2017,   12:15,   M3 (M234)
Seminar on analysis and geometry

Robin Rajamäki
Additive 2D bases
Wednesday 11 October 2017,   15:15,   M2 (M233)
Additive bases, i.e. sets of integers whose pairwise sums cover a desired set of integers, have been studied by number theorists since the early 20th century. In particular, the combinatorial problem of minimizing the number of elements required to cover a given set of consecutive integers is often of interest. Such optimal bases find applications in e.g. sparse linear sensor arrays, where the number of sensors is desired to be kept low in order to reduce costs and mitigate non-ideal coupling effects between array elements. Although much of the existing work on additive bases is directly applicable to 1D sparse array design, often 2D arrays are required in practice. However, additive 2D bases have not been studied as extensively as their 1D counterpart in the past. In our talk, we present some recent results on rectangular additive bases, i.e. additive bases whose sumsets cover a rectangular area of consecutive points in the plane. For example, optimal rectangular bases found through exhaustive computer search are shown. Furthermore, different rectangular bases with analytically tractable structure and a low element count are introduced.
ANTA seminar

Galia Dafni (Concordia University)
Local BMO and Van Schaftingen spaces
Wednesday 11 October 2017,   12:05,   M3 (M234)
Abstract: Based on an inequality of Bourgain and Brezis, Van Schaftingen introduced a scale of function spaces lying between the critical Sobolev space and BMO, and suggested that an analogous result should hold in the case of local BMO spaces on domains. We discuss recent work of A. Butaev, who constructed nonhomogeneous versions of Van Schaftingen spaces on Euclidean space, as well as on manifolds, and showed that they lie between the critical Sobolev space and the space bmo, defined by Goldberg. Moreover, he proved a corresponding version for the nonhomogeneous space of functions of vanishing mean oscillation (vmo). On a Lipschitz domain $\Omega$, Butaev answered the question of Van Schaftingen by showing that there are two scales of spaces lying between $W^{1,n}(\Omega)$ and $W^{1,n}_0(\Omega)$, respectively, and the local BMO spaces bmo_r and bmo_z studied by Chang-Krantz-Stein and Chang-Dafni-Stein.
Seminar on analysis and geometry

Kristian Moring (Diploma thesis talk)
Direct methods in the calculus of variations for parabolic problems
Thursday 05 October 2017,   15:15,   M3 (M234)

Niko Väisänen (Nokia/Aalto)
Beamforming -- Enabling Higher Data Rate Wireless Communications
Thursday 05 October 2017,   15:15,   M205
MSc thesis presentation
ANTA

Mateus Sousa (IMPA, Rio de Janeiro)
Existence for Fourier restriction on hyperboloids
Thursday 05 October 2017,   14:15,   M3 (M234)
In this talk we present some results about existence, as well as non existence, of extremizers for the adjoint Fourier restriction estimate on hyperboloids. We will discuss the Lorentz symmetries of the problem and the concentration-compactness arguments involved in the proofs, as well as connections to the Klein-Gordon equation.

Negin Karimi
LCD codes
Wednesday 04 October 2017,   15:15,   M3 (M234)
Error-correcting codes play an important role in digital communication among all types of codes. Linear codes are studied the most. Because of their algebraic structure, they are easier to describe, encode, and decode than nonlinear codes. A special class of linear codes is linear complementary dual code (LCD code). LCD codes are defined by Massy in 1992. He was shown that asymptotically good codes exist. LCD codes have been widely applied in data storage, communications systems, and cryptography. Also, they are interesting objects in the general framework of algebraic coding. In this talk will be presented some of the properties cyclic codes, quasi-cyclic codes and quasi-twisted codes with complementary dual.
ANTA seminar

Juha Videman (University of Lisbon)
A degenerate elliptic-parabolic system arising in competitive contaminant transport
Wednesday 04 October 2017,   12:15,   M3 (M234)
The transport of contaminants in subsurface environments is a complex process modeled by advection-diffusion-reaction equations. If the reactive adsorption process (accumulation of a pollutant on the porous matrix) is described by a nonlinear isotherm of Freundlich type, the evolution of the solute concentrations is governed by a degenerate parabolic equation. In the multi-species case (contamination by several solutes), this corresponds to a coupled system of degenerate elliptic-parabolic equations. After introducing the basic concepts of modeling contaminant transport in porous media, I will show that this system admits a unique weak solution provided the nonlinear adsorption isotherm associated with the reaction process satisfies certain physically reasonable structural conditions. Under these conditions, the system falls under the general quasi-linear elliptic-parabolic systems addressed by Alt and Luckhaus in their seminal work [1]. The main difference between our approach and that of [1] lies in the existence proof which we base on Rothes method and on solving a convex minimization problem at each time step. Our approach provides also a simple method for the numerical approximation of the system. This is a joint work with Margarida Baia (CAMGSD/IST), Farid Bozorgnia (CAMGSD) and Leonard Monsaingeon (CAMGSD/Universite de Lorraine). [1] W. H. Alt and S. Luckhaus, Quasilinear Elliptic-Parabolic Di erential Equations, Math. Z. 183 (1983), 311-341.
Seminar on analysis and geometry

Timo Hänninen (HY)
Two-weight Lp-Lq bounds for positive dyadic operators in the case 0
Friday 29 September 2017,   15:15,   Kumpula Exactum C124
Harmonic analysis and PDE seminar

Thomas Singer (Aalto)
Existence of variational solutions in non-cylindrical domains
Friday 29 September 2017,   14:15,   Kumpula Exactum C124
Harmonic analysis and PDE seminar

Esko Heinonen (University of Helsinki)
Existence and non-existence results for minimal graphic and p-harmonic functions
Wednesday 27 September 2017,   12:15,   M3 (M234)
In the Euclidean space, by the celebrated result due to Bombieri, De Giorgi, and Miranda, all positive entire solutions of the minimal graph equation are constant. It turns out that on Riemannian manifolds similar results can be obtained for solutions with at most linear growth if the manifold has only one end and asymptotically non-negative sectional curvature. In this talk I will discuss about recent results concerning the existence and non-existence of entire minimal graphic and p-harmonic functions. Talk is based on joint work with Jean-Baptiste Casteras and Ilkka Holopainen.
Seminar on analysis and geometry

Prof. Daniele Boffi (Università di Pavia, Aalto University)
Finite element approximation of resonant modes for the Maxwell cavity problem
Tuesday 26 September 2017,   15:15,   M1 (M232)
The resonant modes of time harmonic Maxwell equations can be identified with the eigensolutions of a problem represented by a variational formulation in mixed form. In this talk we review the finite element approximation of eigenvalue problems arising from partial differential equations. In particular, it will be shown that the analysis of mixed problems differs significantly from that of standard Galerkin formulations. We will show how these results can be applied to the a priori analysis of Maxwell's eigenvalue problem and we will give some indications on how the a posteriori analysis can be performed
Colloquim

Lauri Harhanen (KaVo Kerr), Antti Huhtala (SSF), Saara Hyvönen (DAIN Studios), Mika Juntunen (KONE), Juho Könnö (Wärtsilä), Otto Seiskari (IndoorAtlas), Stratos Staboulis (Eniram)
Sovelletut matemaatikot teollisuudessa
Thursday 21 September 2017,   14:00,   U6, Otakaari 1

Jeff Lindquist (University of California, LA)
Weak capacity in Ahlfors regular metric spaces
Wednesday 20 September 2017,   12:15,   M3 (M234)
We construct and use a hyperbolic filling of a $Q$-regular compact doubling metric space $Z$ to define the notion of the weak $p$-capacity between appropriate subsets of $Z$. This notion extends modulus and is preserved up to constants by quasisymmetric maps. We explore some applications involving Ahlfors regular conformal dimension and quasisymmetric uniformization of metric 2-spheres.
Seminar on analysis and geometry

Tuomo Tiilikainen
Lämpöyhtälön keskiarvoperiaate/Diplomityöesitelmä
Wednesday 13 September 2017,   15:15,   M2 (M233)

Ilmari Kangasniemi (University of Helsinki)
Cohomological behavior of uniformly quasiregular mappings
Wednesday 13 September 2017,   12:15,   M3 (M234)
Based on a joint work with Pekka Pankka. Given a uniformly quasiregular map f on a closed oriented Riemannian manifold, it turns out that all the complex eigenvalues of the induced pull-back map f* in real singular cohomology have a modulus of (deg f)^(k/n), and moreover the induced cohomological map is complex diagonalizable. This can be exploited to obtain limitations on the possible degrees of uniformly quasiregular maps on closed manifolds. The talk goes over some basics and context regarding uniformly quasiregular mappings, and presents the main ideas behind the proofs of the aforementioned results.
Seminar on analysis and geometry

D.Sc (Tech) Antti Punkka
Teaching demonstration: Pareto-optimality in solving multicriteria optimization problems
Friday 08 September 2017,   10:30,   M2 (M233)

Jan Hämäläinen
Elementtimenetelmä magnetostatiikassa
Thursday 07 September 2017,   11:15,   M237
Kandiseminaari

Tarmo Kivioja
Lokaalin sileyden estimoinnista
Thursday 07 September 2017,   10:15,   M237
Kandiseminaari

Ville Kujala
Achieving the capacity of coded PIR using arbitrary linear code (BSc presentation)
Friday 25 August 2017,   15:15,   M3 (M234)
Kandidaattiseminaari

Juuso Korvuo
Hilojen lähimmän vektorin ongelma (kandiesitelmä)
Thursday 24 August 2017,   14:15,   M3 (M234)
Kandidaattiseminaari

Aki Malinen
Algebraic methods in maximum likelihood estimation (BSc presentation)
Thursday 24 August 2017,   09:15,   M3 (M234)
Kandidaattiseminaari

Hoa Ngo [Stochastic afternoon]
Information spreading in a large network
Tuesday 22 August 2017,   16:10,   M3 (M234)
A simple mathematical model for information spreading is a complete graph where everyone knows everyone and everyone relays messages at random time instants to randomly chosen neighbours independently of each other. In this talk we will consider information spreading in the large configuration model, which is a more advanced model. One of the key quantity analysing the rumour spreading speed is the broadcast time, the time when the rumour has reached the entire population. We will also discuss the broadcast time taking into account the passive and active users.

Alex Karrila [Stochastic afternoon]
Boundary branches in a uniform random spanning tree of a planar graph
Tuesday 22 August 2017,   15:10,   M3 (M234)
A physics principle asserts that the scaling limit of a critical lattice model, as increasingly dense lattices approximate a continuum domain, is described by a conformal field theory (CFT). The aim of this talk is to prove rigorously conformal invariance properties in the scaling limit of the uniform spanning tree (UST) of a planar graph, i.e., a tree subgraph that covers all the vertices of the original graph, chosen uniformly at random. In a spanning tree, any two vertices are connected by a unique path, called a branch. We study multiple simultaneous UST boundary-to-boundary branches between given boundary vertices, as well as the boundary visits of a single such branch. The related probabilities have conformally invariant scaling limits, and solve partial differential equations as predicted by CFT. As a collection of curves, such multiple simultaneous branches converge weakly to a conformally invariant law, called the local multiple SLE(2). These are among the first verifications of third-order PDEs of CFT, as well as convergence results to multiple SLE.

Armando W. Gutiérrez [Stochastic afternoon]
The horofunction compactificacion of lp spaces and Hilbert's projective metric
Tuesday 22 August 2017,   14:00,   M3 (M234)
The horofunction compactification is the result of making any metric space into a compact topological space by only using the metric. The elements of this compactification have been recently shown to be very useful in the study of limit theorems for deterministic and random dynamical systems. In this talk I will give a complete description of the horofunction compactification of the classical lp spaces. I will also consider Hilbert's projective metric on the standard cone of positive real vectors, and describe its horofunction compactification. The latter will be used to give a new proof of the well-known Perron theorem.

Valentina Candiani (University of Genova)
The role of segmentation in kidney compartmental analysis
Tuesday 22 August 2017,   10:15,   M2 (M233)
Seminar on Applied Mathematics

Prof. Saminathan Ponnusamy (ISI Chennai/IIT Madras)
Bohr radius
Wednesday 16 August 2017,   12:15,   M3 (M234)
Seminar on Analysis and Geometry

Mikko Kivelä (Aalto University)
Randomized reference models and spreading in temporal networks
Monday 14 August 2017,   15:15,   M3 (M234)
For a long time network science concentrated on static graphs as representations of networked systems. This abstraction was used to analyse shortest path lengths, spreading of disease or information in networks, and many other things. Often the underlying assumption behind such analysis was that the activation of nodes and links is controlled by homogeneous Poisson processes. More recently there has been growing interest in analysing 'temporal networks' where the link activation times are determined directly from data. In this talk I will illustrate how this approach can be used to analyse a large communication network with hundreds of millions of link activation events. I will focus on how 'reference models', in which the data is shuffled in various ways, can be used for this data and how they are used in the literature on temporal networks in general. I will also discuss the challenges in the literature that are caused by the sudden increase in use of such shuffling methods of temporal network.
Aalto Stochastics & Statistics Seminar

Kaisa Nyberg / Chris Brzuska
Connections between linear and statistical independence of binary random variables / Survey about indistinguishability obfuscation
Monday 14 August 2017,   14:30,   M2 (M233)
Informal presentations during the visit of our new Cryptology professor Chris Brzuska
ANTA Seminar: Algebra, Number Theory, and Applications to Communications and Computing / Karpuk, Kaski, Hollanti, Greferath

Dissertation
Vesa Kaarnioja, Prof. Lars Grasedyck (RWTH Aachen University)
On sparse tensor structures in lattice theory and applications of the polynomial collocation method based on sparse grids
Wednesday 02 August 2017,   12:00,   M1 (M232)
Further information

Leevi Korkeala
Hyperbolisten ryhmien pinta-aliryhmät (kandiesitelmä)
Wednesday 02 August 2017,   11:15,   M3 (M234)
Kandidaattiseminaari

Miio Taarna
Julkisen liikenteen verkostojen tarkastelu verkkoteorian keinoin (kandiesitelmä)
Wednesday 02 August 2017,   10:15,   M3 (M234)
Kandidaattiseminaari

Pauliina Kärkkäinen
Positroniemissiotomografian käänteisongelma
Wednesday 02 August 2017,   09:15,   M3 (M234)
Kandidaattiseminaari

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