### Department of Mathematics and Systems Analysis

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* Dates within the next 7 days are marked by a star.

Dr. Razane Tajeddine (HIIT)**Machine learning talk series: Privacy preserving data sharing on vertically partitioned data***** ** Wednesday 12 May 2021, 15:15, Zoom

Further information

Predictive machine learning uses big amounts of data to predict the likelihood of future outcomes. To build predictive models, confidential personal data needs to be collected and shared. Therefore, user data privacy is a major concern when training such models. In many cases, the data is partitioned between multiple servers or parties, where each party holds parts of the data which can not be revealed to the other parties due to privacy concerns. Combining data from different parties gives additional information, and thus the quality of the model is significantly improved. Applying machine learning algorithms to a partitioned dataset without violating the privacy of the users is a challenging task. This talk will be concerned with methods for building predictive models on partitioned data while preserving user privacy.

ANTA Seminar

Dr. Taoufiq Damir**Lattices and wiretap channels (talk series for PhD students in number theory)**

Thursday 20 May 2021, 15:00, Zoom

Further information

ANTA Seminar

Dr. Taoufiq Damir**Lattice-based cryptography, part 1 (talk series for PhD students in number theory)**

Thursday 27 May 2021, 15:00, Zoom

Further information

ANTA Seminar

Dr. Taoufiq Damir**Lattice-based cryptography, part 2 (talk series for PhD students in number theory)**

Thursday 03 June 2021, 15:00, Zoom

Further information

ANTA Seminar

Dr. Taoufiq Damir**Introduction to lattices (talk series for PhD students in number theory)**

Thursday 06 May 2021, 15:00, Zoom

Further information

ANTA Seminar

Dr. Laura Jakobsson**Machine learning talk series: Machine learning meets commutative algebra: Table ideal identification**

Wednesday 05 May 2021, 15:15, Zoom

Further information

Table ideals are monomial ideals that come from tables, i.e. arrangements of integers that satisfy some conditions on the entries, and these ideals have many nice properties. Given a table, the ideal coming from it in a non-minimal form is easy to compute. However, the other direction is not as easy, that is, given a monomial ideal how do we know if it is a table ideal? In this talk, I will introduce the machine learning problem of distinguishing table ideals from non-table ideals, and the results we have obtained from using machine learning to this maths question.

ANTA Seminar

Camilla Hollanti**Wireless communications and number field lattice codes (talk series for PhD students in number theory)**

Thursday 29 April 2021, 15:00, Zoom

Further information

ANTA Seminar

Dr. Mika Malinen ( Aalto University)**A local reparametrization by approximate lines of curvature coordinates**

Thursday 29 April 2021, 13:15, Zoom

Further information

A surface parametrization by orthogonal curvilinear coordinates offers many benefits from the viewpoint of both analysis and practical implementation. However, ways to construct such representations are not immediate. The utility of lines of curvature as a strategy for obtaining such coordinates globally in a smooth surface is severely limited by the presence of umbilical points. Nevertheless, a global parametrization is not necessarily needed in the numerical solution of PDE problems on surfaces, which gives us a motivation for developing
methods to obtain a local reparametrization by consistently accurate lines of curvature coordinates. A way to avoid the possible instabilities of reparametrization in a vicinity of an isolated umbilical point is considered via a sensitivity analysis. Some illustrative examples are also shown.

Dr. Laia Amoros**Machine learning talk series: Practical introduction to machine learning for mathematicians**

Wednesday 28 April 2021, 15:15, Zoom

Further information

This talk is aimed at mathematicians that have heard about machine learning and are interested in getting more familiar with the field, but dont know where to start. Machine learning (ML) covers a huge amount of algorithms that aim at learning useful information from data. Whether the best learning option is supervised, unsupervised or any other kind of learning depends on the type of our data. It turns out that handling the data takes most of the effort, and defining a model to make predictions out of the data can be done with a few simple lines of Python. We will see some easy examples in a Python notebook environment, so the interested mathematician can reproduce the experiments with their own data. We will show how ML can in particular be used to learn information about mathematical objects, which in turn can be useful to better know your data, be it monomial ideals, number fields or Calabi-Yau hypersurfaces.
For the slides and related material, click "further info".

ANTA Seminar

Samuel Nurmi**(Bachelor Thesis Talk) Controlling coil overlap in multi-locus transcranial magnetic stimulation transducers **

Thursday 22 April 2021, 13:00, Zoom

Further information

Bachelor thesis talk

Dissertation

Stavros Evdoridis**On geometric properties of harmonic and polyharmonic mappings**

Wednesday 14 April 2021, 12:00, Zoom

Link to the event https://www.aalto.fi/en/events/defense-of-dissertation-in-the-field-of-mathematics-msc-stavros-evdoridis

Tuomas Leidén**Predictive Multi-target Learning for Industrial Plant Engineering (Master's thesis presentation)**

Thursday 08 April 2021, 13:00, Teams

Further information

Prof. Paul Van Dooren, Université catholique de Louvain**Detecting roles in large graphs**

Thursday 01 April 2021, 13:15, https://aalto.zoom.us/j/67710120716

Computing meaningful clusters of nodes is crucial to analyze very large networks, but since this is a combinatorial optimization problem, its complexity can be prohibitive. In this talk, we present a pairwise node similarity measure that allows to extract roles, i.e. group of nodes sharing similar flow patterns within a network. We then propose a low rank iterative scheme to approximate the similarity measure for very large networks and we show that our low rank similarity score successfully extracts the different roles in random graphs of Erdos-Renyi type. We then argue that when projecting our similarity measure onto a low rank manifold (say, of rank r), the role models can be recovered using classical clustering techniques in a r-dimensional space, which reduces the complexity significantly. We illustrate these ideas with a number of real-world examples.

Perttu Yli-Opas**Detumble algorithm for the AuroraSat-1 propulsive attitude control system**

Thursday 25 March 2021, 14:15, https://aalto.zoom.us/j/67618085167

Bachelor's thesis talk

Luca Ferranti (University of Vaasa)**Optimised polynomial solvers for computer vision and positioning**

Monday 22 March 2021, 10:15, https://aalto.zoom.us/j/68512634218

Systems of polynomial equations naturally arise in several engineering applications. General polynomial solving techniques may not be enough to solve these problems, especially at higher robustness and efficiency requirements. For this reason, specialised polynomial solvers, exploiting the specific structure of the problem, are desired. In the talk, I will describe how optimised polynomial solvers can be automatically generated using Gröbner bases. I will also give an overview of several success stories of these techniques in computer vision and positioning applications, where these automatically generated solvers could solve challenging problems in microseconds. Finally, I will briefly discuss what problems are still open and what are current research trends in this area.

Algebra and Discrete Mathematics Seminar

Lauri Nyman**Solving Systems of 3 Equations in 3 Variables via Resultants**

Thursday 18 March 2021, 13:15, https://aalto.zoom.us/j/67710120716

This talk is a presentation of my master's thesis.
I will discuss a root-finding algorithm that computes numerically the real solutions of a system of three equations in three variables by using the Cayley resultant method. The Cayley resultant method works by first approximating the system of functions by polynomials, and then transforming the resulting multidimensional polynomial root-finding problem into a polynomial eigenvalue problem. The resulting polynomial eigenvalue problem is solved through a linearization given by the colleague pencil. I will present the details of the implementation as well as numerical results.

Olli Winberg**Compressed Sensing of Fourier sparse quasiparticle-interference map**

Wednesday 10 March 2021, 11:00, Zoom: https://aalto.zoom.us/j/62501058048

Bachelor's thesis talk

Emilia Blåsten (Aalto University)**Inverse spectral problem on discrete graphs**

Thursday 04 March 2021, 13:15, https://aalto.zoom.us/j/67710120716

I will introduce the results of my latest publication, arXiv:2101.10026, and its background. The inverse spectral problem in partial differential equation asks for determining unknown coefficients of given partial differential equation, or the underlying manifold structure, from boundary spectral measurements. These are the pairs of all eigenvalues with the boundary normal derivatives of their corresponding Dirichlet eigenfunctions to a fixed partial differential operator. The eigenvalues themselves are not enough to determine the underlying geometry: one cannot hear the shape of a drum. The question has been studied extensively for quantum graphs, but with limited success except for trees. My latest publication takes this topic into the context of discrete graphs. Given a subset of vertices (call it the boundary), and boundary values of Neumann eigenvectors to a graph Laplacian, we show that the rest of the graph structure can be determined assuming that there is "enough" boundary vertices.

Jaakko Pere**On estimation of extreme probability contours under multivariate elliptical Fréchet distributions (Master's thesis presentation)**

Wednesday 03 March 2021, 09:00, https://aalto.zoom.us/j/9150514867

Maija Vahteristo**On the effects of cervical cancer screening (Master's thesis presentation)**

Friday 19 February 2021, 10:00, https://us04web.zoom.us/j/75952975071?pwd=YVJSL3lhS2U4ck1GaWlJMEF1Y0xJZz09

Passcode:0yF0Vh

María Quintana Ponce, Aalto University**Linearizations of Rational Matrices**

Thursday 18 February 2021, 13:15, https://aalto.zoom.us/j/67710120716

Zoom-link : https://aalto.zoom.us/j/67710120716
The numerical solution of rational eigenvalue problems (REPs) is getting a lot of attention. REPs appear directly from applications or they can be used for solving arbitrary nonlinear eigenvalue problems (NLEPs) by approximating the corresponding NLEP by a REP and, then, solving the REP. They also play a fundamental role in system and control theory. Nowadays, one of the most competitive methods for solving REPs is based on linearizations of the corresponding rational matrix. In this talk, we introduce a new notion of linearization for rational matrices, and we provide very simple criteria to determine when a linear polynomial matrix is one of these linearizations. As an application, we study the structure of linearizations constructed in the literature for rational approximations of NLEPs.

Leevi Lindgren**On Moment-Based Estimation of Extreme Probability Contours Under Ellipticity (Master's thesis presentation)**

Wednesday 10 February 2021, 10:00, in Teams

https://teams.microsoft.com/l/meetup-join/19%3ameeting_OGI4YTk3YjktOGVkOC00MzBiLThlZmUtMmQzY2U5NTU3NWUz%40thread.v2/0?context=%7b%22Tid%22%3a%22af2afc02-96d2-4cff-b1b5-d43897ff97ad%22%2c%22Oid%22%3a%22e36756e7-9e4d-48ef-bad1-d1a1e6d333ec%22%7d

Tuomas Tuukkanen**Haar measures on locally compact groups (harmonic analysis workshop)**

Friday 05 February 2021, 10:15, https://aalto.zoom.us/j/67515140063

Seminar on analysis and geometry

Timo Takala**The duality of Hardy functions and BMO functions (harmonic analysis workshop)**

Friday 29 January 2021, 10:15, https://aalto.zoom.us/j/61457600970

Seminar on analysis and geometry

Laura Jakobsson**A survey of the Miyata-Proudfoot-Ramos category of graphs, 2**

Friday 15 January 2021, 11:00, https://aalto.zoom.us/j/62497682030

https://aalto.zoom.us/j/62497682030

Alexander Engström

Christoffer Lundström **Primtalssatsen**

Monday 21 December 2020, 14:15, https://aalto.zoom.us/j/68077881815

BSc thesis presentation. The presentation will be in Swedish.

Laura Jakobsson**A survey of the Miyata-Proudfoot-Ramos category of graphs, 1**

Friday 18 December 2020, 11:00, https://aalto.zoom.us/j/65122897296

https://aalto.zoom.us/j/65122897296

Engström

Kim Myyryläinen**Rubio de Francia extrapolation theorem (harmonic analysis workshop)**

Wednesday 16 December 2020, 10:15, https://aalto.zoom.us/j/63006317735

Seminar on analysis and geometry

Napoleon Freitas Paajanen**Connection between Littlewood-Paley operators and Calderón-Zygmund integral kernels (harmonic analysis workshop)**

Tuesday 15 December 2020, 14:15, https://aalto.zoom.us/j/69928590389

Seminar on analysis and geometry

Niklas Miller**Algebraic number theory: an analysis of well-rounded lattices (MSc thesis presentation)**

Tuesday 15 December 2020, 14:00, https://aalto.zoom.us/j/68470667079

ANTA

Lari-Matti Tuomala**Secure coded multi-party matrix multiplication (MSc thesis presentation)**

Tuesday 15 December 2020, 13:00, https://aalto.zoom.us/j/68470667079

ANTA

Lauri Särkiö**Boundedness of convolution type Calderón-Zygmund operators (harmonic analysis workshop)**

Tuesday 15 December 2020, 10:15, https://aalto.zoom.us/j/69928590389

Seminar on analysis and geometry

Kristian Moring**Supercaloric functions to the singular parabolic p-Laplace equation in the supercritical case**

Monday 14 December 2020, 14:15, https://aalto.zoom.us/j/64913244648

Seminar on analysis and geometry

Napoleon Freitas Paajanen**Sobolev characterization based on Marcinkiewicz integral transform (diploma thesis presentation)**

Monday 14 December 2020, 10:15, https://aalto.zoom.us/j/64913244648

Seminar on analysis and geometry

Pasi Hakulinen**On the Backward Monte-Carlo Method with Application to Fast Ion Simulation in Magnetized Plasma**

Friday 11 December 2020, 14:15, https://aalto.zoom.us/j/2126347484

https://aalto.zoom.us/j/2126347484

Dissertation

Henri Södergård (Aalto University)**Image deblurring by numerical linear algebra (BSc thesis)**

Wednesday 09 December 2020, 14:15, https://aalto.zoom.us/j/67899163157

When taking a photograph, we usually want the resulting image to be a faithful reconstruction of the reality we see with our own eyes. However, almost all images will inevitably suffer from some form of imperfections such as blurriness. To fix this, we can deblur the image employing methods and techniques from numerical linear algebra to mathematically. This way, we can restore the maximum amount of information about the true image from a blurry image.
In this talk, I plan to introduce some basic concepts in image deblurring, including the naive solution, the point spread function, spectral filtering (such as Truncated Singular Value Decomposition or the Tikhonov method) and regularisation methods (such as Generalised Cross Validation, the Discrepancy Principle and the L-Curve Criterion). I will also present the results of some experiments that I have run to compare some of these methods in practice, by testing them on some blurred images.

BSc Seminar

Lauri Hitruhin**Boundary behaviour of conformal and quasiconformal mappings**

Monday 07 December 2020, 14:15, https://aalto.zoom.us/j/68924190377

Seminar on analysis and geometry

Cintia Pacchiano**Regularity properties for quasi-minimizers of a (p,q)-Dirichlet integral**

Monday 07 December 2020, 10:15, https://aalto.zoom.us/j/68924190377

Seminar on analysis and geometry

Dr Jeta Molla (Aalto University)**Numerical methods for the stochastic wave equation**

Tuesday 24 November 2020, 16:00, https://aalto.zoom.us/j/68911259210

Further information

The objective of this talk is to propose a full discretization for the stochastic wave equation. More specifically, the discontinuous Galerkin finite element method is used in space and analyzed in a semigroup framework, and an explicit stochastic position Verlet scheme is used for the temporal approximation. Numerical experiments illustrate our theoretical results on strong convergence rates. Further, we analyze and bound the expected energy and numerically show excellent agreement with the energy of the exact solution.
Join Zoom Meeting
https://aalto.zoom.us/j/68911259210
Meeting ID: 689 1125 9210

Aalto Stochastics & Statistics Seminar / Leskelä

Emma-Karoliina Kurki**Integral estimates on Whitney chains**

Monday 09 November 2020, 14:15, M237

Seminar on analysis and geometry

Kim Myyryläinen**Median-type JohnNirenberg spaces**

Monday 09 November 2020, 10:15, M237

Seminar on analysis and geometry

Dissertation

Mohamed Taoufiq Damir**Well-rounded lattices and applications to physical layer security (Doctoral defence)**

Friday 06 November 2020, 15:00, Zoom https://aalto.zoom.us/j/65632983027

Further information

ANTA

Julian Weigt **The dyadic maximal function has bounded variation**

Monday 02 November 2020, 14:15, M237

Seminar on analysis and geometry

Carlos Mudarra**Extensions of jets with smooth convex functions and applications**

Monday 02 November 2020, 10:15, M237

Seminar on analysis and geometry

Prashanta Garain**Nonexistence of variational minimizers related to a quasilinear singular problem in metric measure spaces**

Monday 05 October 2020, 14:15, M237

Seminar on analysis and geometry

Sauli Lindberg**Convex integration in magnetohydrodynamics**

Monday 05 October 2020, 10:15, M237

Seminar on analysis and geometry

Afrin Hossain**Fatou and Julia sets in Rational Iteration (kandiesitelmä)**

Monday 21 September 2020, 13:15, M237

Oona Oinonen**Dihedraalisen piilotetun aliryhmän ongelma (kandiesitelmä)**

Monday 21 September 2020, 11:00, Zoom https://aalto.zoom.us/j/63992296777

ANTA

Antti Immonen**Secure Distributed Matrix Multiplication (BSc presentation)**

Monday 21 September 2020, 10:15, Zoom https://aalto.zoom.us/j/63992296777

ANTA

Kalle Kytölä**Euler integrals and a quantum group**

Monday 31 August 2020, 15:45, https://aalto.zoom.us/j/62494927603

mathematical physics end-of-summer seminar day (Kytölä)

Shinji Koshida**Point processes and fermionic algebras**

Monday 31 August 2020, 15:00, https://aalto.zoom.us/j/62494927603

mathematical physics end-of-summer seminar day (Kytölä)

Eveliina Peltola**On large deviations of multiple SLEs**

Monday 31 August 2020, 14:15, https://aalto.zoom.us/j/62494927603

mathematical physics end-of-summer seminar day (Kytölä)

Aapo Pajala**Euclidean Distance Geometry and Its Applications in 3D Genome Reconstruction (Bachelor thesis presentation)**

Monday 31 August 2020, 14:00, https://aalto.zoom.us/j/69001841503

Konstantin Izyurov**Asymptotics of determinants of discrete Laplacians**

Monday 31 August 2020, 13:30, https://aalto.zoom.us/j/62494927603

mathematical physics end-of-summer seminar day (Kytölä)

Tuomas Tuukkanen**Probabilistic Liouville conformal field theory**

Monday 31 August 2020, 11:45, https://aalto.zoom.us/j/62494927603

mathematical physics end-of-summer seminar day (Kytölä)

Osama Abuzaid**TBA**

Monday 31 August 2020, 11:00, https://aalto.zoom.us/j/62494927603

mathematical physics end-of-summer seminar day (Kytölä)

Nerissa Shakespeare**Äärellisistä heijastusryhmistä (kandiesitelmä)**

Monday 31 August 2020, 10:00, https://aalto.zoom.us/j/64382365198

matematiikan kandiseminaari

Perttu Saarela**Hansen polytopes of split graphs (Bachelor thesis presentation)**

Friday 28 August 2020, 11:30, U5 (U147)

https://aalto.zoom.us/j/61788754640

Kai Hippi**Tutte-polynomien laskeminen (Kandiesitelmä)**

Friday 28 August 2020, 10:45, U5 (U147)

https://aalto.zoom.us/j/61788754640

Meri Aho**Cyclic flats and graphical matroids (Bachelor thesis presentation)**

Friday 28 August 2020, 10:00, U5 (U147)

https://aalto.zoom.us/j/61788754640

Selim Virtanen**Johdatus p-adisiin lukuihin ja lokaali-globaali-periaatteeseen (kandiesitelmä)**

Thursday 27 August 2020, 14:00, U5 and Zoom https://aalto.zoom.us/j/64748623259

ANTA

Okko Makkonen**Tuplaavuus ja Sobolevin upotus (Kandityöesitelmä)**

Thursday 27 August 2020, 13:15, U5

Kandiseminaari

Joonas Laaksonen**Legendren sarjakehitelmän suppenemisesta 2D:ssä (Kandiesitelmä)**

Thursday 27 August 2020, 11:00, https://aalto.zoom.us/j/67335018504

Kandiesitelmä

Etna Lindy**Parameter estimation for group-based phylogenetic models in the probability and Fourier coordinates (Bachelor thesis presentation)**

Wednesday 26 August 2020, 11:00, zoom

https://aalto.zoom.us/j/69001841503

Aleksi Lahti**Classifying critical points of the Euclidean Distance from real plane curves (Bachelor thesis presentation)**

Wednesday 26 August 2020, 10:00, zoom

https://aalto.zoom.us/j/69001841503

Dr Mikhail Shubin (THL)**Fitting SEIR models to COVID wave in Finland: Lessons and open questions**

Thursday 25 June 2020, 15:00, Teams

Further information

The seminar is intended for epidemiological modellers.
I will present a set SEIR models used by THL to model the COVID outbreak in Finland.
I will analyse particular model features, discussing whatever they there useful for inference.
I will describe different questions which we tried to answer with these models, and wherever modelling was able to provide useful insight.
For any questions, contact Mikhail (Mikhail.shubin@thl.fi
https://teams.microsoft.com/l/meetup-join/19%3ameeting_NjE4MDVkYWUtOGQ5MS00YWIxLWIwNDYtMzUxZjQyNmExOTE5%40thread.v2/0?context=%7b%22Tid%22%3a%2281d1db0d-c492-4225-a66c-3c3a9e4b8360%22%2c%22Oid%22%3a%221373e033-bd9e-4fa9-898a-a07b58e1f61e%22%7d

Aalto Stochastics & Statistics Seminar / Leskelä

Alex Karrila (IHÉS, Paris)**Delocalization of the six-vertex height function**

Thursday 11 June 2020, 10:15, https://aalto.zoom.us/j/66281157229

The six-vertex model is a planar random model for the crystalline structure of water ice. It has recently given important insights to the connection of Conformal field theory and critical 2D random models, due to its natural representation as a random field, called the height function, and due to couplings to several other important random models (e.g. FK cluster model, Ising and Potts models, dimers, random graph homomorphisms)
We prove that the six-vertex height function has a localization/delocalization phase transition. Delocalization means roughly speaking that the model is not sensitive to a boundary condition far away; indeed our result for instance implies that there exists a unique whole-plane six-vertex model in the delocalized phase. The main tools of the proof are an explicit solution of the free energy of the model, and RSW and FKG inequalities similar as in the study of various percolation models.
(Based on ongoing work with Hugo Duminil-Copin, Ioan Manolescu, and Mendes Oulamara.)
Zoom-link: https://aalto.zoom.us/j/66281157229

Kytölä

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