Theses  Department of Mathematics
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Monoid actions, their categorification and applications
(Bilkent University, 201701)We study actions of monoids and monoidal categories, and their relations with (co)homology theories. We start by discussing actions of monoids via biactions. We show that there is a welldefined functorial reverse action ... 
Deformation classes of singular quartic surfaces
(Bilkent University, 201701)We study complex spatial quartic surfaces with simple singularities and give their classication up to equisingular deformation. Simple quartics are K3surfaces and as such they can be studied by means of the global Torelli ... 
On the Nẹ́ronseveri lattice of Delsarte surfaces
(Bilkent University, 201610)The Nẹ́ronSeveri group, NS(X), of a given (nonsingular projective) variety, X, is defined in only algebrogeometric terms, however it is also known to be an arithmetic invariant. So it is an important study that helps ... 
Numerical study of orthogonal polynomials for fractal measures
(Bilkent University, 201607)In recent years, potential theory has an essential effect on approximation theory and orthogonal polynomials. Basic concepts of the modern theory of general orthogonal polynomials are described in terms of Potential Theory. ... 
On some of the simple composition factors of the biset functor of Ppermutation modules
(Bilkent University, 201607)Let k be an algebraically closed field of characteristic p, which is a prime, and C denote the field of complex numbers. Given a finite group G, letting ppk(G) denote the Grothendieck group of ppermutation kGmodules, we ... 
Geodesics of threedimensional walker manifolds
(Bilkent University, 201607)We review some basic facts of Lorentzian geometry including causality and geodesic completeness. We depict the properties of curves and planes in threedimensional Minkowski space. We deffne the Walker manifolds, that is, ... 
Homotopy colimits and decompositions of function complexes
(Bilkent University, 201607)Given a functor F : C→ GSp, the homotopy colimit hocolimCF is defined as the diagonal space of simplicial replacement of F. Let G be a finite group and F be a family of subgroups of G, the classifying space EFG can be taken ... 
Groebner basis approach in graphtheoretical problems
(Bilkent University, 201606)In the study of graphs, it is often desirable to know about the colorability properties of a given graph or whether it is planar or if it contains a Hamiltonian cycle. We consider such problems and describe corresponding ... 
On complete intersections and connectedness
(Bilkent University, 2002)In this thesis, we study the relation between connectedness and complete intersections. We describe the concept of connectedness in codimension k. We also study the basic facts about CohenMacaulay rings, and give ... 
On the minimal number of elements generating an algebraic set
(Bilkent University, 2002)In this thesis we present studies on the general problem of finding the minimal number of elements generating an algebraic set in nspace both set and ideal theoretically. 
Concrete sheaves and continuous spaces
(Bilkent University, 2015)In algebraic topology and differential geometry, most categories lack some good ”convenient” properties like being cartesian closed, having pullbacks, pushouts, limits, colimits... We will introduce the notion of continuous ... 
Blocks of quotients of mackey algebras
(Bilkent University, 2015)We review a theorem by Boltje and K¨ulshammer which states that under certain circumstances the endomorphism ring EndRG(RX) has only one block. We study the double Burnside ring, the Burnside ring and the transformations ... 
Biset functors and brauer's induction theorem
(Bilkent University, 2014)We introduce two algebras on the endomorphism ring of the direct sum of character rings of groups from some collection. We prove the equality of these algebras to simplify a step in the proof of Brauer’s Induction Theorem. ... 
Kuroda's class number formula
(Bilkent University, 2007)In number theory theory, the class number of a field is a significant invariant. All over the time, people have come up with formulas for some cases and in this thesis I will discuss a proof of a class number formula for ... 
Distance between a maximum point and the zero set of an entire function
(Bilkent University, 2006)We obtain asymptotical bounds from below for the distance between a maximum modulus point and the zero set of an entire function. Known bounds (Macintyre, 1938) are more precise, but they are valid only for some maximum ... 
Logarithmic dimension and bases in whitney spaces
(Bilkent University, 2006)In generalization of [3] we will give the formula for the logarithmic dimension of any Cantortype set. We will demonstrate some applications of the logarithmic dimension in Potential Theory. We will construct a polynomial ... 
Complete positivity in operator algebras
(Bilkent University, 2006)In this thesis we survey positive and completely positive maps defined on operator systems. In Chapter 3 we study the properties of positive maps as well as construction of positive maps under certain conditions. In ... 
Interpolating bases in the spaces of C(formula)functions on cantortype sets
(Bilkent University, 2006)In this work by using the method of local interpolat ions suggested in [9] we construct topological bases in the spaces of CPfunctions defined on uniformly perfect compact sets of Cantor type. Elements of the basis are ... 
Applications of duality for Hp spaces
(Bilkent University, 2006) 
Modular vector invariants
(Bilkent University, 2006)Vector invariants of finite groups (see the introduction for definitions) provides, in general, counterexamples for many properties of the invariant theory when the characteristic of the ground field divides the group ...