Fredagskollokviet i Matematikk og Fysikk

Foredragsserien er myntet på et bredt publikum, både studenter og ansatte, med bakgrunn fra matematikk eller fysikk. Alle interesserte er velkomne! Kontaktperson: Martin G. Gulbrandsen.

Tid og rom: fredager klokken 14:15, rom E541. Lett bevertning.

Enkel adresse til denne siden: http://fymat.ux.uis.no/

Program for høsten 2015

Fredag 4. september kl 14:15, rom E541: Patrick Sawerengera (University of Malawi)

Tittel: Constructing pairing-friendly ordinary elliptic curves with low embedding degree

Elliptic curves which are suitable for pairing based protocols are known as pairing friendly elliptic curves. These elliptic curves have small embedding degree with respect to a large prime order subgroup, as such are rare because are hard to construct and hence require specific constructions.

We propose a method of constructing pairing-friendly elliptic curves extending the method proposed by Brezing and Weng. In our method, we define the size of the subgroup to be the minimal polynomial of the cyclotomic polynomial and re-define the number field. Using a new method, we have constructed families of pairing friendly elliptic curves with small rho value as best reported in literature for for embedding degree k= 7, 8 ,10,14,15,20,21,24,28,42 and 48 with CM discriminant D=1 or D=3.

Fredag 11. september kl 14:15, rom E541: Riccardo Moschetti (UiS)

Tittel: The scheme of dual numbers and the description of its derived category

The derived category of an algebraic variety is a powerful tool to deal with geometric problems. I am interested in finding characterization and properties of the so-called Fourier-Mukai functors. This problem can be studied in the simple but meaningful example of the scheme of dual numbers. In this talk I will focus on the structure of the derived category of this scheme.

Fredag 25. september kl 14:15, rom E541: Matthew Terje Aadne (UiS)

Tittel: Spectral triples derived from lattice ordered semigroups

I will present the work i did during my master thesis in addition to giving a basic introduction to C*-algebras. The thesis centered around two structures in noncommutative geometry, namely spectral triples and quantum statistical mechanical systems.

Fredag 16. oktober kl 14:15, rom E541: Njål Foldnes (BI Stavanger)

Tittel: Covariance model simulation using regular vines: the VITA method

A new and flexible simulation method for non-normal data with user-specified marginal distributions, covariance matrix and certain bivariate dependencies is proposed.
The VITA (VIne To Anything) method is based on regular vines and generalises the NORTA (NORmal To Anything) method.
We prove fundamental theoretical properties of the VITA method, including weak conditions that secure its generality and convergence.
Two illustrations demonstrate the flexibility and usefulness of VITA in the context of structural equation models. We also discuss the use of VITA simulation to evaluate heteroscedastic, autocorrelation consistent (HAC) econometric methods

Fredag 30. oktober kl 14:15, rom E541: Bashar Dudin (University of Coimbra)

Tittel: Compactifying the Hurwitz scheme: moduli spaces through an example

Since the seminal work of Deligne and Mumford on the compactification of the moduli space of compact Riemann surfaces, much of the work on the degenerations of Riemann surfaces and related objects has lead to increasingly involved combinatorial structures. We give an example of this phenomenon by looking at various compactifications of the space of meromorphic functions on compact Riemann surfaces with prescribed order of poles.

Fredag 6. november kl 14:15, rom E541: Tuomas Tenkanen (Helsinki)

Tittel: Improving cosmic string simulations

In cosmic string network simulations, system is discretised on a lattice and one encounters several artificial effects when strings achieve relativistic velocities. In this presentation I'll talk about how one can study and quantify arising lattice artefacts, by constructing an isolated moving string on a lattice, and also discuss possible implications of arising artefacts to existing simulations. Furthermore I present how one can improve simulation algorithm in order to minimize arising artefacts.

Fredag 27. november kl 14:15, rom E541: Anders Kvellestad

Tittel: Adventures in parameter space - New Physics global fits

There exists a multitude of theories for physics beyond the Standard Model. Further, the expected phenomenology for any given theory may vary greatly across the parameter space of the theory. Which New Physics scenario is preferred by current data? And how will the situation change when new experimental results arrive?
To answer these questions we need to compare theory predictions to all available data in a statistically valid way, in so called global fits. In this talk I will give an introduction to New Physics global fits, highlighting some of the challenges currently facing this field. I will also introduce GAMBIT, a new tool for performing global fits, soon to be released open source. Although developed within a collaboration of particle and astroparticle physicists, GAMBIT is designed to be a completely general tool for performing global fits, and may therefore prove useful also for other fields of research.

Program for våren 2015

Fredag 6. februar kl 14:15, rom E541: Atanas Iliev (Seoul University)

Tittel: Fano manifolds, old and new

Notes around the topic in this talk.

Fredag 27. februar kl 14:15, rom E541: Angelo Ricciardone (UiS)

Tittel: New Light on the Early Universe: the Planck mission

The Cosmic Microwave Background (CMB) represents a snapshot of the Early Universe and an accurate measurement of this probes both the physics of those energy scales and the basic properties of the universe today. Recently Planck, the third generation of CMB satellite, has released the most detailed full-sky image of the CMB putting unprecedentedly tight constraints on the foundations of cosmology. In this talk I will give an overview of the most relevant cosmological results in light of the 2013 and 2015 Planck data release about temperature and (first release of) polarization. These results give an hint on the future of theoretical cosmology but still leaving many key cosmological questions unanswered.

Fredag 6. mars kl 14:15, rom E541: Pavel Gumenyuk (UiS)

Tittel: Recent advances in Loewner Theory

Abstract.

Fredag 8. mai kl 14:15, rom E541: Atle Øglend (UiS)

Tittel: Modeling Periodic Decoupling of Commodity Prices, Application to UK natural gas and Brent oil prices

When related commodity prices are subject to periodic decoupling conventional linear models of price dynamics such as the Vector Error Correction Model (VECM) can lead to erroneous inferences about long-run relationships, price adjustments towards the equilibrium and relative values. We propose the use of regime-switching models to address these issues. We apply our model to determine the long-run relationship between UK natural gas and Brent oil prices. The empirical model uses price data to infer whether pricing is oil-driven (integrated) or gas-specific (decoupled). We find that UK natural gas and oil (Brent) are cointegrated for the majority of the sample considered (1997-2014). Gas prices tend to decouple during fall and early winter, when they increase relative to oil consistent with heating demand for natural gas creating gas-specific pricing. Using the model to infer relative values when evidence favors integrated markets, we find that the industry 10-1 rule-of-thumb holds, meaning that the value of one barrel of oil is 10 times the value of one MMbtu of natural gas.

Fredag 22. mai kl 14:15, rom E541: Stein Andreas Bethuelsen (Universiteit Leiden)

Tittel: Random Walks in Random Environment

The classical random walk model is a central object within probability theory, mathematics and science in general. Random walks in random environment is a natural generalisation of this model where the random walk interacts with a second process (the environment). Motivation for such models comes from problems in biology, chemistry and physics. An example is the study of transport processes, for example propagation of heat or diffusion of matter through a medium with irregularities. From a mathematical viewpoint, such models exhibit new and surprising phenomena and open up for many interesting questions.
 In this talk, I will give a brief introduction to this fascinating field and guide you through some of the main questions and challenges. If time permits, I will also discuss some recent work in progress made for random walks in dynamically evolving environments, based on joint work with Florian Völlering (TU Berlin).

Fredag 29. mai kl 14:15, rom E541: Andreas Hohenegger (UiS)

Tittel: Creating the asymmetry by cutting a pie

Despite the absence of surprises in recent high-precision data from experiments on the particle-collider and the astronomy frontier, there is convincing evidence that our present description of phenomena at the intersection of these two realms is incomplete. This evidence comes from cosmological observations and includes the matter-antimatter asymmetry of the universe which represents perhaps the most apparent problem and is the motive for this talk. The theoretical problem of creating the asymmetry is known to have solutions within extensions of the standard model of particle physics. Based on the fundamental concepts of quantum field theory a large number of such theories were shown to offer explanations. While there are different plausibility arguments for one or the other, none of them was shown to be realized in nature, however. Instead of reviewing or highlighting on one of the many theories, I will attempt to expose the fundamental building blocks needed for a quantum field theory to produce an asymmetry. To this end I consider a simplified model which comprises the necessary ingredients and allows to present the relevant issues in a comprehensible way. I will also touch on recent advances in the consistent theoretical description of these matters.

Fredag 5. juni kl 14:15, rom E541: Andreas Hohenegger (UiS)

Tittel: Creating the asymmetry by cutting a pie (part II)

Fredag 12. juni kl 14:15, rom E541: Andreas Hohenegger (UiS)

Tittel: Creating the asymmetry by cutting a pie (part III)

Program for høsten 2014

Fredag 19. september kl 14:15, rom E541: Per Amund Amundsen (UiS)

Tittel: Den kopernikanske revolusjon

Sammendrag: Foredraget vil handle om hvordan vi gikk fra en geosentrisk modell hvor jorda ikke sto i sentrum, til en heliosentrisk modell hvor sola ikke sto i sentrum...

Fredag 26. september kl 13:15, rom E541: Sammy Alaoui Soulimani (UiS)

Tittel: Deformation of complex manifolds and applications

Sammendrag: The aim is to give an overview of classical deformation theory, mainly of compact complex manifolds, and to present some of its many applications on problems of classifications in geometry. The theory represents an active area of research nowadays, being important in many fields, especially in algebraic geometry and mathematical physics.

Fredag 3. oktober kl 14:15, rom E541: Reggie Davidrajuh (UiS)

Tittel: Discrete Event Simulation with GPenSIM

Sammendrag: Discrete event simulation is a multidisciplinary activity that is practiced in nearly all the branches of engineering (especially in computer science, industrial engineering, and production engineering) and also in management science, operations research, and economics. Discrete event simulation is a basically about computer-aided model-building of real-life systems with the aim of better understanding of how these systems work and to solve problems like poor performance, bottle-necks, and downtime.This lecture introduces a new tool for discrete event simulation, known as GPenSIM. GPenSIM have been developed at the department of electrical and computer engineering (IDE @ UIS) for the past ten years. GPenSIM is a mathematical modeling language implemented on MATLAB, and is based on graph theory. In this lecture: firstly, a brief overview of the successful applications of GPenSIM (in modeling of fish supply chain, oil drilling, and airport flow management) is given. Secondly, the mathematical basics of GPenSIM are introduced.

Fredag 17. oktober kl 14:15, rom E541: Letterio Gatto (Politecnico di Torino)

Tittel: The Cauchy problem for Linear ODEs with constant coefficients

Sammendrag: See here.

Fredag 24. oktober kl 14:15, rom E541: Kari Rummukainen (University of Helsinki).

Tittel: The standard model and beyond on the lattice

Sammendrag: Many processes in particle physics can be reliably studied only with the help of large scale numerical simulations, lattice Monte Carlo calculations. In this talk I give an overview of the lattice simulations, applied to the Standard Model of particle physics. I will also describe how the simulations can be used to study scenarios which go beyond the Standard Model physics.

Onsdag 29. oktober kl 11:00, rom E541: James Lucietti (University of Edinburgh).

Tittel: New black holes in five dimensions

Sammendrag: It has been known for some time that the black hole uniqueness theorem does not extend to higher dimensional spacetimes. I will argue that the classification of five dimensional asymptotically flat black hole solutions is far from complete, even for solutions with the same symmetry as the known spherical black holes and black rings. I will illustrate this by presenting two novel supersymmetric black hole solutions in this context. The first is a black hole with a horizon of lens space topology. The second is a spherical black hole with an exterior region which possesses non-trivial topology (a 2-cycle). The latter solution may carry the same conserved charges as the known spherical black hole, thereby demonstrating black hole non-uniqueness even amongst spherical black holes.

Fredag 7. november kl 13:15, rom E541: Børd Støve (UiB)

Tittel: A Test for Nonlinearity in Temperature Proxy Records

Sammendrag: A brief survey of temperature reconstructions methods are given. We then try to answer whether temperature proxy records are linear recorders of past temperature conditions? A statistical test for non-linearity is applied to 15 millennial-long proxy records with an annual resolution that was shown to significantly respond to Northern Hemisphere annual mean temperature selected from a collection of 30 proxies. The test, based on generalized additive modeling, shows that most of the proxies can indeed be shown to be linear functions of annual mean temperature, but two proxy records do not appear to have a linear relationship with temperature—this supports the assumption of linearity in most climate reconstruction work. The method tests for nonlinearity in a proxy relative to the group of proxies with which it is being used together. The robustness of the results is tested, and it was found that the results are stable to the choice of proxies. The linearity-testing method is quite general and could in the future be used for larger and more extensive sets of proxies.

Fredag 14. november kl 14:15, rom E541: Christer Hadland (University of St. Andrews/SR bank)

Tittel: Data Science in bank and finance

Sammendrag: Two projects involving data mining and multivariate statistical modelling will be presented: "Text Mining to detect hedge fund risk" and "Customer Recommendation Machine for Banking"

Tirsdag 18. november kl 12:15, rom H-317 i Ellen & Axel Lunds hus (fellesseminar med Handelshøgskolen): Per Mykland (University of Chicago)

Tittel: Financial high frequency data

Sammendrag: Recent years have seen a rapid growth in high frequency financial data. This is a form of "big data", and their existence has opened the possibility of accurately determining volatility, correlation, skewness, regression and hedging coefficients, and similar latent quantities. This can be done non-parametrically in small time periods, such as one day or even less. We introduce the types of data, and discuss what can be estimated. We then focus on four themes which are central to such data: (1) how to estimate in the presence of microstructure noise, (2) how to import methods from classical parametric inference, (3) how to use measure changes to better understand the data, and (4) how to set standard errors without pain. We finally discuss the limits to high frequency inference. (Joint work with Lan Zhang, UIC.)

Fredag 21. november kl 13:15, rom E541: Arttu Rajantie (Imperial College London)

Tittel: Magnetic monopoles in theory and experiment

Sammendrag: There are strong theoretical reasons to expect that magnetic monopoles, hypothetical particles with non-zero magnetic charge, may exist, including Dirac's famous observation that their existence would explain the quantisation of electric charge. Yet, in spite of extensive searches, they have not been found. It has also proved difficult to formulate a consistent quantum field theory description of them. I give a review of their theoretical and experimental status of magnetic monopoles, in light of the new MoEDAL experiment at the LHC. I also discuss theoretical problems in quantising magnetic monopoles and calculating their production rate in particle collisions, and possible ways to overcome them.

Fredag 28. november kl 13:15, rom E541: Dmitry Shogin (UiS)

Tittel: Irreversible thermodynamics in cosmology

Sammendrag: Perfect fluids in equilibrium manifest no ”frictional” effects and do not generate entropy, their dynamics being reversible and non-dissipative. Such models are adequate in many cases. However, the dynamics of real fluids is irreversible, and description of some processes in cosmology cannot be provided without a relativistic theory of dissipative fluids. In this seminar I will review the the most widely used theories of relativistic thermodynamics: the original Eckart theory and the more advanced full and truncated Israel-Stewart theories (also known as causal, or second-order thermodynamics).

Fredag 5. desember kl 13:15, rom E541: Dmitry Shogin (UiS)

Tittel: The instabilities of Israel-Stewart theory in anisotropic cosmological backgrounds

Sammendrag: The Israel-Stewart theory is derived under assumption that the fluid is close to equilibrium, which implies that dissipative fluxes are relatively small. The stability of this model has been proven for a Minkowski background. However, the situation can be essentially different in a cosmological context. We investigate the dynamics of an Israel-Stewart fluid in anisotropic Bianchi cosmologies and show that cosmological evolution can give an essential rise to dissipative fluxes.This drives the fluid substantially far from equilibrium, underlining the fact that a consistent model of nonlinear irreversible thermodynamics is required to provide a relevant physical description to such processes.

Fredag 12. desember kl 13:15, rom E541: Stephan Huber (University of Sussex)

Tittel: Electroweak baryogenesis after LHC8

Sammendrag: I will give a status report of electroweak baryogenesis and the electroweak phase transition in popular extensions of the standard model, after the first LHC run.
Topic revision: r1 - 2016-02-17, MartinGulbrandsen
 

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