Browsing Mathematics by Title

Berić, Mladen (Belgrade , 1912)[more][less]

Daoub, Hamza (Beograd , 2013)[more][less]
Abstract: In this thesis, we are going to highligth two di erent relations between graphs and nite commutative rings. The rst one is the well known as Unitary Cayley Graph, where the study of this assocciation and some results are presented from [1]. The second one is a completely di erent; it connects digraphs with quadratic polynomials with coe tents in Zn under the mapping (a; b) 7! (a + b; ab), for some n < 1. A Computer calculations are involved to support the study. The algorithm which is used for these calculations is built on original Mathematica and Matlab Softwares. Furthermore, Some principles are needed in this thesis for the seek of support and completeness. . . URI: http://hdl.handle.net/123456789/4267 Files in this item: 1
phdHamza_Daoub.pdf ( 1.154Mb ) 
Daoub, Hamza (Belgrade , 2013)[more][less]
Abstract: In this thesis, we are doing to highlight two different relations between graphs and finite commutative rings. The first one is the well known as Unitary Cayley Graph, where the study of this association and some results are presented from (1). The second on is a completely different; it connects digraphs with quadratic polynomials with coeffitients in Zn under the mapping (a,b)> (a+b,ab), for some n<...... A Computer calculations are involved to support the study. The algorithm which is used for these calculations is built on original Mathematica and Matlab Softwares. Furthemore, Some principles are needed in this thesis for the seek of support and completeness... URI: http://hdl.handle.net/123456789/3834 Files in this item: 1
HDPhD_o.pdf ( 2.806Mb ) 
Grulović, Milan (Belgrade , 1984)[more][less]
Abstract: The thesis consists of five chapters. In the first part of Chapter 1 forcing relations for infinite logics are considered. It is shown that if in the case of infinite logic we want to extend syntactic apparatus adequately and that forcing joining stays deductive closed set which contains all logically valid formulas, then forcing joining has to formulate by "weak" formulas. In the second part of this chapter a correction of the proof of the interpolation theorem for infinite logics is presented. The result from Chapter 2 is the following: it is shown that all important properties of Robinson’s finite forcing are transmitted to nfinite forcing by corresponding "nnotions". Moreover, a construction of nfinite forcing joining by Henrard’s approximation chains is presented. The main result of Chapter 3 is that for each theory T of a language L there is an extension T' defined in the corresponding extension L' such that. Relations between a theory (the theory of dense linearly ordering with maximal and minimal elements, the theory of groups, the theory of Abelian groups, the theory of fields, full arithmetic, Peano’s arithmetic) and its corresponding nfinite forcing joins are studied in Chapter 4. Also relations between nfinite forcing joins are studied. A connection between nfinite forcing and the type theory are studied in Chapter 5, and some generalizations of the known results are given. URI: http://hdl.handle.net/123456789/56 Files in this item: 1
phdMilanGrulovic.pdf ( 2.377Mb ) 
Marić, Filip (Belgrade)[more][less]

Telebaković Onić, Sonja (Beograd , 2022)[more][less]
Abstract: n this dissertation the connection between Frobenius algebras and topological quantum field theories (TQFTs) is investigated. It is wellknown that each 2dimensional TQFT (2TQFT) corresponds to a commutative Frobenius algebra and conversely, i.e., that the category whose objects are 2TQFTs is equivalent to the category of commutative Frobe nius algebras. Every 2TQFT is completely determined by the image of 1dimensional sphere S1 and by its values on the generators of the category of 2dimensional oriented cobordisms. Relations that hold for these cobordisms correspond precisely to the axioms of a commutative Frobenius algebra. Following the pattern of the Frobenius structure assigned to the sphere S1 in this way, we examine the Frobenius structure of spheres in all other dimensions. For every d ≥ 2, the sphere Sd−1 is a commutative Frobenius object in the category of ddimensional cobordisms. We prove that there is no distinction between spheres Sd−1, for d ≥ 2, because they are all free of additional equations formulated in the language of multiplication, unit, comultiplication and counit. The only exception is the sphere S0 which is a symmetric Frobenius object but not commutative. The sphere S0 is mapped to a matrix Frobenius algebra by the Brauerian representation, which is an example of a faithful 1TQFT functor. We obtain the faithfulness result for all 1TQFTs, mapping the 0dimensional manifold, consisting of one point to a vector space of dimension at least 2. Finally, we show that the commutative Frobenius algebra QZ5 ⊗ Z(QS3), defined as the ten sor product of the group algebra and the centre of the group algebra, corresponds to the faithful 2TQFT. It means that 2dimensional cobordisms are equivalent if and only if the corresponding linear maps are equal. URI: http://hdl.handle.net/123456789/5353 Files in this item: 1
stoDisertacijaOnic.pdf ( 9.095Mb ) 
Tanović, Predrag (Montreal , 1994)[more][less]
Abstract: The thesis is a research about nonisolation properties of superstable types over finite domains in general. Two notions of nonisoltions, the notion of eventualstrong (i.e. esn) and the notion of internal are introduced. The thesis consists of three chapters. In Chapter 1 of the thesis the techniques of the stability theory which are used in Chapter 2 and Chapter 3 are overviewed. In Chapter 2 of the thesis NDFC theories are studied and the notions of dimension and U_αrank through partial orders are developed. It is proved that if the theory T is strictly stable and the the order type of rationals cannot be embedded into the fundamental order of $T$ and there is no strictly stable group interpretable in T^eq, then the theory T has continuum nonisomorphic countable models. It is noted that strongly nonisolated types can be present due to the dimensional discontinuity property. In Chapter 3 of the thesis small superstable theories are studied. In the first part of that chapter the eventualstrong and internally nonisolated types are considered, and some properties were proved. The second part of Chapter 3 contains the proof of the following theorem: if the theory T is a complete, superstable theory, the generic type of every simple group definable in T^eq is orthogonal to all NENI types and sup{U(p)pϵS(T)}≥ ω^ω holds, then the theory T has continuum nonisomorphic countable models. URI: http://hdl.handle.net/123456789/186 Files in this item: 1
phdPredragTanovic.pdf ( 2.221Mb ) 
Šehu, Isljam (Priština , 1985)[more][less]

Drešević, Milan (Beograd , 1973)[more][less]
URI: http://hdl.handle.net/123456789/4096 Files in this item: 1
Funkcionalni_prostori.PDF ( 2.559Mb ) 
Drešević, Milan (Belgrade)[more][less]

Krtinić, Djordje (MATEMATIČKI FAKULTET UNIVERZITETA U BEOGRADU , 2011)[more][less]

Šobot, Boris (Novi Sad , 2009)[more][less]
Abstract: The method of forcing is widely used in set theory to obtain various consistency proofs. Complete Boolean algebras play the main role in applications of forcing. Therefore it is useful to define games on Boolean algebras that characterize their properties important for the method. The most investigated game is Jech’s distributivity game, such that the first player has the winning strategy iff the algebra is not (!, 2)distributive. We define another game characterizing the collapsing of the continuum to !, prove several sufficient conditions for the second player to have a winning strategy, and obtain a Boolean algebra on which the game is undetermined. URI: http://hdl.handle.net/123456789/297 Files in this item: 1
phdBorisSobot.pdf ( 987.6Kb ) 
Šobot, Boris (UNIVERSITY OF NOVI SAD FACULTY OF SCIENCE DEPARTMENT OF MATHEMATICS AND INFORMATICS , 2009)[more][less]

Stanić, Marija (Kragujevac, Srbija , 2007)[more][less]
Abstract: The field of research in this dissertation is consideration of some nonstandard types of orthogonality and their applications to constructions of quadrature rules with maximal degree of exactness, i.e., quadrature rules of Gaussian type. The research in this dissertation is connected with the following subjects: Theory of Orthogonality, Numerical Integration and Approximation Theory. We have tried to produce a balanced work between theoretical results and numerical algorithms. URI: http://hdl.handle.net/123456789/1741 Files in this item: 1
PhD MS.pdf ( 784.9Kb ) 
Minčić, Svetislav (Novi Sad)[more][less]

Lopandić, Dragomir (Belgrade)[more][less]

Udovičić, Enes (Belgrade , 1980)[more][less]

Stanimirović, Zorica (Belgrade , 2007)[more][less]
Abstract: U ovom radu opisani su različiti genetski algoritmi (GA) za rešavanje četiri NPteška hab lokacijska problema: problem phab medijane neograničenih kapaciteta sa jednostrukim alokacijama (USApHMP), problem phab medijane/centra ograničenih kapaciteta sa jednostrukim alokacijama (CSApHMP/CSApHCP) i hab lokacijski problem ograničenih kapaciteta sa jednostrukim alokacijama (CSAHLP). Ovi hab lokacijski problemi nalaze veliku primenu u dizajniranju transportnih i telekomunikacijskih sistema, poštanskih i drugih sistema isporuke, lokalnih i globalnih računarskih mreža, itd. Za problem phab medijane neograničenih kapaciteta sa jednostrukim alokacijama (USApHMP), razvijene su GA metode koje koriste dva različita načina kodiranja i adekvatne modifikovane genetske operatore. U cilju poboljšanja efikasnosti predloženih genetskih algoritama, primenjena je hibridizacija oba GA koncepta sa heuristikom lokalnog pretraživanja, pa su tako nastale hibridne HGA1 i HGA2 metode koje su veoma uspešne i pri rešavanju problema velikih dimenzija. Za rešavanje hab lokacijskih problema ograničenih kapaciteta CSApHMP, CSApHCP i CSAHLP takođe su predložene razne verzije genetskih algoritama. Primenjene su dve razičite reprezentacije rešenja i odgovarajući genetski operatori razvijeni u skladu sa prirodom problema. Implementirani genetski operatori čuvaju korektnost jedinki u tokom generacija GA i u smislu očuvanja broja uspostavljenih habova i u smislu ograničenja kapaciteta habova. Sve opisane genetske (evolutivne) metode testirane su na odgovarajućim standardnim ORLIB instancama iz literature. Za sva četiri hab lokacijska problema koja su razmatrana u ovom radu, predloženi (hibridni) genetski algoritmi dostižu sve do sada poznate optimalne vrednosti na datim instancama u zadovoljavajućem vremenu izvršavanja. U radu su data rešenja i za probleme velikih dimenzija (n=100,200 p≤20) za koje optimalna rešenja nisu poznata, a neki od ovih problema do sada nisu rešavani u literaturi. Dobijeni rezultati predloženih GA metoda jasno ukazuju na značaj i potencijal genetskih pristupa rešavanju hab i drugih lokacijskih problema.In this paper some new genetic algorithms (GA) for solving four NPhard hub location problems are described: Uncapacitated Single Allocation phub Center Problem (USApHCP), Capacitated Single Allocation phub Median/Center Problem (CSApHMP/CSApHCP) and Capacitated Single Allocation Hub Location Problem (CSAHLP). These hub ploblems have various applications in designing transportation and telecommunications systems, postal and other delivery systems, local and golobal computer area networks, etc. For the Uncapacitated Single Allocation phub Center Problem (USApHCP), two hybrid heuristic methods, named HGA1 and HGA2 are proposed. These methods are a combination of a genetic algorithm and a generalization of the wellknown fast interchange heuristic (IH). In order to investigate the effect of encoding on GA performance, two different encoding schemes are implemented: binary encoding in HGA1, and integer representation in HGA2. Modified genetic operators that keep the feasibility of individuals are designed and implemented in both HGA1 and HGA2. The performed computational experiments showed the effectiveness of both hybrid methods, even for solving largescaled problem instances For the capacitated variants of hub location problems CSApHMP, CSApHCP i CSAHLP, new genetic approaches are also described. In proposed genetic algorithms, new encoding schemes are implemented with appropriate objective functions. By using specific representation and modified genetic operators, proposed GA approaches keep the feasibility of individuals, i.e. the fixed number of established hubs and/or satisfying the capacity constraints on hubs. The numerical experiments were carried out on the standard hub data set from the literature. For all four hub problems that were studied, the corresponding GA method proved to be robust and efficient in solving the problem instances with up to 200 nodes and 20 hubs. Computational experiments demonstrate that all proposed GA methods reach all previously known optimal solutions on tested hub instances. The algorithm is also benchmarked on large scale hub instances with n=100,200 nodes and p≤20 hubs that are not solved (to optimality) so far. The presented computational results clearly indicate the usefulness of the proposed GA approaches. URI: http://hdl.handle.net/123456789/298 Files in this item: 1
phdZoricaStanimirovic.pdf ( 666.6Kb ) 
Đorić, Miloš (Beograd , 2022)[more][less]
Abstract: In this dissertation, the classification of some important classes od hypersurfaces M of the nearly Kähler S3 × S3 is considered, along with the parametrisation of the geodesic lines of this manifold. This manifold is one of only four examples of homogeneous, 6dimensional, nearly Kähler manifolds. In addition to the almost complex structure J, this manifold is en dowed with an almost product structure P , which anticommutes with J. Owing to these facts, there are two families of interesting tangent vector fields on S3 × S3, called P−singular vector fields, having similar properties as A−singular vector fields on complex quadrics Q, which are already known. The notion of P−principal and P−isotropic tangent vector fields of S3 × S3 is defined, along with their basic properties. In the case of P−principal normal vector field ξ of the hypersurface M , the partial classification is given, while the immersion of the hypersurfaces M with P−isotropic normal vector field ξ is stated explicitly. URI: http://hdl.handle.net/123456789/5324 Files in this item: 1
MilosDjoricDoktorat.pdf ( 800.8Kb ) 
Šukilović, Tijana (Beograd , 2015)[more][less]
Abstract: In the present work we classify left invariant metrics of arbitrary signature on fourdimensional nilpotent Lie groups. Their geometry is extensively studied with special emphasis on holonomy groups and decomposability of metrics. Also, isometry groups are completely described and we give examples of metrics where strict inequalities Isplit < Iaut < I hold. It is interesting that Walker metrics appear as the underlying structure of neutral signature metrics on the nilpotent Lie groups with degenerate center. We nd necessary and su cient condition for them to locally admit nilpotent group of isometries. Finally, we solve the problem of projectively equivalent metric on fourdimensional nilpotent Lie groups by showing that left invariant metric is either geometrically rigid or have projectively equivalent metrics that are also a nely equivalent. All a nely equivalent metrics are left invariant, while their signature may change. URI: http://hdl.handle.net/123456789/4453 Files in this item: 1
Doktorska_disertacija__Tijana_Sukilovic.pdf ( 1.501Mb )