Ana Carpio (09/07/15)

Benedikt Magnússon, júlí 7, 2015

Málstofa í stærðfræði

Fyrirlesari: Ana Carpio, Universidad Complutense de Madrid
Titill: Well posedness of a kinetic model for angiogenesis

Staðsetning: VR-II, 158.
Tími: Fimmtudagur 9. júlí, klukkan 15:00-16:00.

Ágrip:

Tumor induced angiogenesis processes including the effect of stochastic motion and branching of blood vessels can be described coupling an integrodifferential kinetic equation of Fokker-Planck type with a diffusion equation for the tumor induced angiogenic factor. The chemotactic force field depends on the first velocity moment (flux of blood vessels) through the angiogenic factor. We develop an existence and uniqueness theory for this system under natural assumptions on the initial data. Our theory combines the construction of fundamental solutions for associated linearized problems with comparison principles, sharp estimates of the velocity moments and compactness results for this type of kinetic and parabolic operators.

Luis Bonilla (09/07/15)

Benedikt Magnússon, júlí 7, 2015

Málstofa í stærðfræði

Fyrirlesari: Luis L. Bonilla, Universidad Carlos III de Madrid
Titill: Hybrid modeling of tumor induced angiogenesis

Staðsetning: VR-II, 158.
Tími: Fimmtudagur 9. júlí, klukkan 13:30-14:30.

Ágrip:

Angiogenesis is the formation of blood vessels induced by a deficit of oxygen in tissues. It is a basic process in wound repair, formation of vessel networks during growth. diseases of inflammatory character, cancer, etc. When modeling of tumor-driven angiogenesis, a major source of analytical and computational complexity is the strong coupling between the kinetic parameters of the relevant stochastic branching-and-growth of the capillary network, and the family of interacting underlying elds. To reduce this complexity, we take advantage of the system intrinsic multiscale structure: we describe the stochastic cell dynamics at their natural microscale, whereas we describe the deterministic dynamics of the underlying fields at a larger macroscale. We set up a conceptual stochastic model including branching, elongation, and anastomosis of vessels and derive a mean eld approximation for their densities. This leads to a deterministic integro-partial differential system that describes the formation of the stochastic vessel network. We discuss the proper capillary injecting boundary conditions and the results of relevant numerical simulations.

Oleg Evnin (30/07/15)

Benedikt Magnússon, júní 22, 2015

Málstofa í stærðfræði

Fyrirlesari: Oleg Evnin
Titill: Non-linear perturbations of AdS space-time

Staðsetning: VR-II, 147.
Tímasetning: Þriðjudaginn 30. júní, klukkan 15:00-16:00.

Ágrip:

Recent, mostly numerical investigations have revealed a complex interplay of stability and instability in the dynamics of classical AdS perturbations. I’ll review some attempts to develop an analytic understanding of these fascinating phenomena, based on methods of non-linear dynamical perturbation theory.

Doktorsvörn – Warsha Singh

Benedikt Magnússon, júní 12, 2015
Hvenær hefst þessi viðburður: 12. júní 2015 – 10:00
Staðsetning viðburðar: Aðalbygging
Nánari staðsetning: Hátíðarsalur

Háskóli ÍslandsFöstudaginn 12. júní ver Warsha Singh doktorsritgerð sína í vistfræðilíkönum við Raunvísindadeild Háskóla Íslands. Ritgerðin ber heitið: Bættar aðferðir við stofnmat sjávarbotndýra með notkun djúpfars (Towards efficient benthic survey design with the use of autonomous underwater vehicles).

Andmælendur eru dr. Michael Fogarty, forstöðumaður Ecosystem management program við Northeast Fisheries Science Center, Bandaríkjunum, og dr. Arthur Trembanis, dósent í haffræði og jarðvísindum við University of Delaware, Bandaríkjunum.

Leiðbeinandi var dr. Gunnar Stefánsson, prófessor við Raunvísindadeild Háskóla Íslands. Auk hans sátu í doktorsnefnd dr. Erla Björk Örnólfsdóttir, rektor Háskólans á Hólum, Jörundur Svavarsson, prófessor við Líf- og umhverfisvísindadeild Háskóla Íslands, og dr. Tómas Philip Rúnarsson, prófessor við Iðnaðarverkfræði-, vélaverkfræði- og tölvunarfræðideild Háskóla Íslands.

Dr. Hafliði Pétur Gíslason, prófessor og deildarforseti Raunvísindadeildar, stjórnar athöfninni.

 

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Evgeny Poletsky (11/06/15)

Benedikt Magnússon, júní 9, 2015

Málstofa í stærðfræði

Fyrirlesari: Evgeny Poletsky, Syracuse University
Titill: Hardy spaces on hyperconvex domains: recent advances

Staðsetning: Naustið, Endurmenntun (hér)
Tími: Fimmtudagur 11. júní, klukkan 15:00-16:00.

Ágrip:

In 2008 M. Stessin and the speaker introduced on a general hyperconvex domain \(D\) the spaces of holomorphic functions \(H^p_u(D)\) as analogs of the classical Hardy spaces on the unit disk. This spaces are parameterized by plurisubharmonic exhaustion functions \(u\) of \(D\). When \(D\) is strictly pseudoconvex they all are the subsets of classical Hardy spaces \(H^p(D)\) and coincide with \(H^p(D)\) when \(u\) is a pluricomplex Green function.
In my talk we will provide all necessary definitions and discuss recent advances: complete description of these spaces on the unit disk and their projective limits on strongly pseudoconvex domains.

Bjarni Jens Kristinsson and Henning Úlfarsson (04/06/15)

Benedikt Magnússon, júní 1, 2015

Málstofa í stærðfræði

Fyrirlesarar: Bjarni Jens Kristinsson, Háskóla Íslands, og Henning Úlfarsson, Háskólanum í Reykjavík
Titill: Occurrence graphs of patterns in permutations

Staðsetning: Naustið, Endurmenntun (hér)
Tími: Fimmtudagur 4. júní, klukkan 15:00-16:00.

Ágrip:

This paper is based on a generalisation of the idea behind the proof of the Simultaneous Shading Lemma by Claesson et al. (2014). We define the occurrence graph \(G_p(\pi)\) of a pattern \(p\) in a permutation \(\pi\) as the graph with the occurrences of \(p\) in \(\pi\) as vertices and edges between the vertices if the occurrences differ by exactly one element. We study the general properties of the occurrence graphs and some interesting extreme cases. The main theorem in this paper is that every hereditary property of graphs produces a permutation class.

Hermann Þórisson (28/05/15)

Benedikt Magnússon, maí 26, 2015

Málstofa í stærðfræði

Speaker: Hermann Thorisson, University of Iceland
Title: Mass-Stationarity, Shift-Coupling, and Brownian Motion

Staðsetning: Naustið, Endurmenntun (hér)
Tími: Fimmtudagur 28. maí, klukkan 15:00-16:00.

Ágrip:

After considering mass-stationarity and shift-coupling briefly in an abstract setting, we focus on the special case of stochastic processes on the line associated with diffuse random measures. The main examples are Brownian motion and the Brownian bridge.

Christer O. Kiselman (26/05/15)

Benedikt Magnússon, maí 22, 2015

Málstofa í stærðfræði

Speaker: Christer O. Kiselman, Uppsala University
Title: Discrete convolution operators, the Fourier transformation, and its tropical counterpart: the Fenchel transformation

Staðsetning: Naustið, Endurmenntun (hér)
Tími: Þriðjudagur 26. maí, klukkan 15:00-16:00.

Ágrip:

We study solvability of convolution equations for functions with discrete support in \(\mathbb R^n\), a special case being functions with support in the integer points. The more general case is of interest for several grids in Euclidean space, like the body-centered and face-centered tesselations of three-space.
The theorem of existence of fundamental solutions by Boor, Höllig & Riemenschneider is generalized to general discrete supports using only elementary methods. We also study the asymptotic growth of sequences and arrays using the Fourier and Fenchel transformations.

Rögnvaldur Möller (21/05/15)

Benedikt Magnússon, maí 15, 2015

Málstofa í stærðfræði

Speaker: Rögnvaldur Möller
Title: Infinite cubic vertex-transitive graphs

Staðsetning: Naustið, Endurmenntun (hér)
Tími: Fimmtudagur 21. maí, klukkan 15:00-16:00.

Ágrip:

Tutte’s two papers from 1947 and 1959 on cubic graphs were the starting point of the in-depth study of the interplay between the structure of a group and the structure of a graph that the group acts on. In this talk I will describe applications of Tutte’s ideas where it is assumed that the graph is infinite and the stabilizers of vertices are infinite.

Ville Keränen (18/05/15)

Benedikt Magnússon, maí 15, 2015

Málstofa í stærðfræði

Speaker: Ville Keränen, University of Oxford
Title: Thermalization in the AdS/CFT duality

Staðsetning: V-155, VR-II
Tími: Mánudaginn 18. maí, klukkan 15:00-16:00.

Ágrip:

The AdS/CFT duality relates the dynamics of certain strongly interacting quantum field theories to the dynamics of certain gravitational theories in spacetimes with one higher dimension. Thus, it provides an interesting tool in which one can approach unsolved questions in either side by rephrasing them in the dual theory. One hope is to learn about the long standing problem of non-equilibrium dynamics in strongly interacting quantum field theories using the gravitational description. I will describe some work towards this goal. More precisely, by studying a few relatively simple examples, I will describe how the process of thermalization in the strongly coupled quantum field theory is captured in the gravitational description.