Displaying theses 110 of 436 total
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N.G. Lamoree 
Master programme: Mathematical Physics  January 28th, 2019  
Institute: KdVI  Research group: Mathematical Physics  Graduation thesis  Supervisor: Dr. R.R.J. Bocklandt 

Homological mirror symmetry and deformation theory for punctured Riemann surfaces We use an idea from string theory, made rigorous by mathematicians, to translate a problem in geometry to a problem in algebra. We solve the algebraic problem and translate this back to geometry and interpret the result. 

Scientific abstract (pdf 1K) For more info or full text, mail to: raf.bocklandt@gmail.com 
H. Ahmadan 
Master programme: Stochastics and Financial Mathematics  January 16th, 2019  
Institute: KdVI  Research group: Stochastics  Graduation thesis  Supervisor: dr. B. Kleijn 
Phase transitions in random graphs Random graphs exhibit phase transitions of certain graph properties. These graph properties change abruptly when the edge probability passes through a threshold. In this thesis we study two phase transition of random graphs: the transition from a connected graph to a disconnected graph and the transition from containing a giant connected component to containing "small" connected components. 

Scientific abstract (pdf 1K) Full text (pdf 3029K) 
L. Haringa 
Master programme: Stochastics and Financial Mathematics  December 20th, 2018  
Institute: KdVI  Research group: Stochastics and Financial Mathematics  Graduation thesis  Supervisor: dr. A.J. van Es 

Learning to distinguish—agnostic unsupervised classification Neural networks provide a link from mathematics to data by fitting to arbitrary relationships, requiring no prior knowledge about these relationships. While already very successful as supervised classifiers, they may also work in a setting where no prior knowledge at all is used. It is shown that a useful classifier can still emerge under an informationtheoretic objective function which compares model values to each other, rather than to a target value. The objective function is a novel proposition, which is intuitively motivated, tested empirically, and further investigated mathematically in this thesis. Fitting a neural network under the objective results in promising behaviour on a benchmark dataset of handwritten digits (MNIST). Furthermore, a second application to text distinguishes meaningful clusters in pop music lyrics, which have predictive power for the probability of a Billboard Hot 100 notation. 

Scientific abstract (pdf 177K) Full text (pdf 17120K) 
W. Swijgman 
Master programme: Mathematics  November 9th, 2018  
Institute: KdVI  Research group: Dynamical Systems and Numerical Analysis  Graduation thesis  Supervisor: Ale Jan Homburg 
Growth dynamics of crossfeeding microbes Crossfeeding means that an essential (scarce) nutrient for a microbe is produced by another microbe. Several systems of microbial crossfeeding communities are studied in which for every microbial species (at least) one nutrient is scarce in the environment and only produced by another species in the system. In certain settings it is possible that this crossfeeding can keep on going so that the microbial concentrations grow infinitely large as time approaches infinity. Since we want to study what happens to the growth rates and the relative concentrations in this case, a transformation of the space to a compact set (the Poincare sphere) is done. That is, the original (planar) dynamics are projected onto a sphere such that infinity is mapped onto the equator; we can now study what happens on the sphere and in particular what the dynamics near/on the equator are. 

Scientific abstract (pdf 1K) Full text (pdf 7970K) 
G. Puccetti 
Master programme: Mathematics  November 8th, 2018  
Institute: KdVI  Research group: Stochastics  Graduation thesis  Supervisor: Michel Mandjes 

Average nearest neighbor degree in geometric inhomogeneous random graph Random graphs are a mathematical way to describe real networks, such as social networks or the world wide web. In the model we study, vertices are provided with weights and positions in a circle. The probability for two nodes to be connected is dependent on both these quantities. We describe the effect that the presence of distance has in this model, particularly on the average nearest neighbor degree, a quantity that makes us understand the degree of the neighbors of certain vertices. After this is done we implement an algorithm to simulate instances of this model and to study it numerically, looking at its clustering coefficient. 

Scientific abstract (pdf 1K) For more info or full text, mail to: m.r.h.mandjes@uva.nl 
H. Zhang 
Master programme: Stochastics and Financial Mathematics  October 30th, 2018  
Institute: KdVI  Research group: Stochastics and Financial Mathematics  Graduation thesis  Supervisor: prof.dr. R. Nunez Queija 

Capacity and Efficiency Analysis of MultiserverQueuing Systems Imagine you are a member of a strategy committee and are supposed to decide to put some servers in the system. You can either put a fast single server or c servers that the sever speed is c times slower than the single one. What will you choose? This research focuses on some specific queuing systems and both theoretically and numerically comparison based on firstcomefirstserve service discipline and onebyone arrival assumption. For $M/M/cdot$ systems, single fast server is the best, but for more variable distributions that will not be true. Analytical solutions of multiserver systems are hard to obtain. For that matrixgeometric approach allows to study multiserver systems with socalled phasetype distributions, that can be used to approximate any general distribution as closely as desired. For future studies it may be relevant to reconsider some of the assumptions made in this thesis. For example, some features of systems like the service discipline (first come first serve, random order, last come first serve), the behavior of customers, the arrival process (one by one or in batches) and service capacity, all lead to different level of efficiency to systems. 

Scientific abstract (pdf 1K) Full text (pdf 2566K) 
T.M.R. Hesselink 
Master programme: Mathematics  October 29th, 2018  
Institute: KdVI  Research group: Stochastics  Graduation thesis  Supervisor: J.H. van Zanten 
Optimal Bayesian distributed methods for nonparametric regression In this thesis we will consider Gaussian processes making use of both the Matérn kernel and the squared exponential kernel. However neither of these Gaussian process priors lead to scalable Bayesian methods and therefore they are highly impractical for large data sets. To solve this, we turn to the distributed setting where we divide the data of size $n$ over $m$ machines, which collectively help to compute a global posterior. For the distributed setting, we will consider multiple methods, which consist of changing the local posterior and different aggregation methods for the local posteriors. These methods will be studied via simulation. We will pose theoretical results for some of the methods. Finally, we will perform simulation studies using the squared exponential kernel, which will show to perform similarly to the Matérn kernel. 

Scientific abstract (pdf 1K) Full text (pdf 1419K) 
B. van Brussel 
Master programme: Stochastics and Financial Mathematics  October 23rd, 2018  
Institute: KdVI  Research group: Stochastics and Financial Mathematics  Graduation thesis  Supervisor: JanPieter Dorsman 

Simulating the patient flow on the Short Stay Unit For this thesis I did an internship at the Amsterdam UMC. The subject of this thesis is the bed occupation of the Short Stay Unit at the VUmc. I have built a simulation model for the arrivals and departures. With this model I was able to predict the effects of certain policy changes. Examples of these changes were the increased inflow of patients from other wards and the effects of changing the opening times. 

Scientific abstract (pdf 1K) Full text (pdf 3337K) 
L. Raounas 
Master programme: Stochastics and Financial Mathematics  October 17th, 2018  
Institute: UvA / Other  Research group: Kortewegde Vries Institute for Mathematics  Graduation thesis  Supervisor: Asma Khedher 
Conic Swaption Pricing With Displaced SABR If the market is liquid and complete, then the classical financial framework offers an unambiguous pricing method for all financial products, through the use of the riskneutral measure. We thus have the rule of the "one price". However, in illiquid markets, the price of a product depends on the market direction, i.e. whether it is being bought or sold. This leads to the difference between the buying and the selling price, called the "bidask spread", to become nonnegligible. Conic Finance offers a framework in which easy to compute formulas are derived for the direct calculation of both the bid and the ask prices. The SABR ("Stochastic Alpha Beta Rho") model is a stochastic volatility model used to calculate forward values of a derivative's underlying, for example the price of a stock or an interest rate. In the current postcrisis environment, interest rates are very low and sometimes even negative. To deal with this situation, the Displaced SABR extension of SABR was developed. In this thesis, we follow the Conic Finance approach and use the Displaced SABR model in order to directly price the bid and ask prices of swaptions, i.e. derivatives in which the underlying is a swap. 

Scientific abstract (pdf 1K) Full text (pdf 1808K) 
T.E. ter Bogt 
Master programme: Stochastics and Financial Mathematics  October 17th, 2018  
Institute: KdVI  Research group: Stochastics and Financial Mathematics  Graduation thesis  Supervisor: dr. Asma Khedher, prof. dr. Michel Vellekoop 
ArbitrageFree Interpolation in the LIBOR Market Model The LIBOR Market Model is a mathematical model for interest rates, which provides information on a limited number of (forward) interest rates, applying to some specific time periods. Sometimes, an interest rate applying to a different time period is required. This thesis develops a new interpolation method for interest rates in the LIBOR Market Model. Unlike some other methods, it can be used when interest rates are negative. The new interpolation method ensures that interpolated interest rates have a volatility which is close to the volatility of the interest rates provided by the LIBOR Market Model, which is important in applications. The effects of the new interpolation method on the calculation of CVA for interest rate derivatives using the LIBOR Market Model are also considered. 

Scientific abstract (pdf 1K) Full text (pdf 2089K) 
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