Efficiency in algorithms is important, especially in terms of execution time, as it directly impacts user experience. For example, when a customer visits a website, even a mere one-second delay can significantly reduce their patience, and the likelihood of them abandoning the site increases. This principle applies to search algorithms as well. This project is about implementing a time-efficient tree-based search algorithm that focuses on finding similarities between search input and stored data. The objective is to achieve an execution time as close to O(1) regardless of the data size. The implemented algorithm will be compared with a linear search algorithm, which has an execution time that grows along with the data size. By measuring the executiontimes of both search methods, the project aims to demonstrate the superiority of the tree-based search algorithm in terms of time efficiency.

Authentication in digital systems is still prominently done through passwords. These passwords should simultaneously be easy to remember, unique, and change over time. Humans, however, have a limited ability to remember complex passwords. To make this easier, users often adopt schemes where a base word is only modified slightly. While such schemes can easily fulfil basic password requirements based on length or the symbols used, they can leave users vulnerable. Leaked passwords, even expired ones, can be exploited by malicious actors and a single compromised account can cascade to multiple services.  We propose a v-gram based approach to detect similarity with a set of passwords, which could be used to improve user password habits. The proposed scheme utilizes a Cuckoo Filter, which allows for inherent obfuscation of the stored passwords and the integration of encryption techniques natively. The system could for example be embedded in a password manager to inform users when they are using a password that is too similar to a previous password. This work comprises an analysis of several aspects of the system in order to assess its suitability.  A Cuckoo Filter using a single byte fingerprint for each v-gram can achieve load factors exceeding 95%, while maintaining a false positivity rate of less than 3%. The computational cost of guessing a password based on the information stored within the filter is relatively low. While the false positivity rate of the filter and the size of the alphabet have an impact, they are only logarithmically proportional to the cost, and the attack is considered a significant vulnerability. Nevertheless, the proposed system can be a viable alternative for detecting similarity between passwords — if configured correctly — and could be used to guide user behaviour to more secure password habits.

Le détachement d'une goutte est un phénomène que nous observons quotidiennement. Il résulte de la rupture de l'interface entre le fluide dispersé en goutte et le fluide environnant. Cette rupture a fait l'objet de nombreuses études. Il est bien établi que sa dynamique est régie par une compétition entre la capillarité, l'inertie, et la viscosité du fluide. Ce manuscrit décrit l'influence sur la dynamique de rupture d'une modification des propriétés de l'interface entre deux fluides à l'aide d'agents de surface. Lorsque l'agent de surface est un surfactant (SDS), la dynamique d'amincissement peut se faire selon deux modes. Deux régimes linéaires en temps constituent le premier mode. Le second mode comporte trois régimes linéaires. Dans les deux cas, l'aminicissement commence par un premier régime, suivi d'un deuxième régime de pente plus forte. Lorsque le troisième régime existe, sa pente est inférieure à celle du second régime. La variation des pentes des régimes linéaires témoigne du comportement dynamique du surfactant à l'interface. La valeur de la tension interfaciale $\gamma$ extraite du premier régime linéaire correspond à la valeur à l'équilibre de la tension interfaciale du système, $\gamma_{eq}$. La vitesse d'amincissement plus élevée au cours du second régime est reliée à une dépletion partielle en surfactant de la zone d'amincissement maximal. Le ralentissement constaté pendant le troisième régime est lié au déplacement de cette zone vers une région plus riche en surfactant, où la tension $\gamma$ est plus faible. La dynamique d'amincissement du cou est très différente lorsque des polymères de poids moléculaire intermédiaire ($\sim$ 100 kDa) sont présents simultanément avec du SDS dans la phase continue. Lorsque $C_{SDS}$ est supérieure à 0,15 fois la concentration micellaire critique (CMC), le comportement est identique à celui observé en présence de surfactant seul. En dessous de 0,15 CMC, l'amincissement ralentit exponentiellement à l'approche de la rupture, et un phénomène de beads-on-a-string apparaît. Ces constatations sont analogues à celles faites lorsqu'une solution de polymères est menée à la rupture. Dans notre cas, les polymères sont uniquement à la surface du jet et non dans son volume! Une analyse des profils du cou au cours du temps démontre l'existence d'une auto-similarité à l'approche de la rupture. Bien que les systèmes étudiés soient plus complexes, ils présentent des caractéristiques qualitativement analogues à celles observées dans des systèmes de fluides simples. Toutefois, il existe une grande différence quantitative. / Droplet detachment is ubiquitous in everyday life. It results from the rupture of an interface separating two fluids. This rupture has been widely studied. It is now well established that it relies on a competition between capillary, inertial and viscous phenomena. In this manuscript, we report on the influence on the breakup dynamics of the presence of surface agents at the interface. When SDS is used as a surface agent, thinning can proceed in two ways. In the first mode, the dynamics of thinning are characterized by two linear-in-time regimes. The second mode is made of three linear-in-time regimes. In both cases, thinning starts with a first regime, followed by a steeper second regime. When a third regime exists, its slope is softer. Slope variation bears witness to a dynamical behaviour of the surfactants at the interface. The value for the interfacial tension $\gamma$ calculated from the slope of the first linear regime is in agreement with the equilibrium interfacial tension of the system, $\gamma_{eq}$. The higher thinning speed during the second regime is linked to a partial depletion in surfactant of the maximal thinning zone. The slowdown in the tihrd regime is related to a displacement of the thinning zone in a region of higher surfactant concentration, where $\gamma$ is lower. The thinning dynamics is very different when polymers are added to the surfactant solution. If $C_{SDS}$ is higher than 0.15 times the critical micellar concentration (CMC), a behaviour similar to the pure-surfactant case is observed. Below 0.15 CMC, an exponential slowdown is observed in the last instants, as well as a "`beads-on-a-string"' phenomenon. These observations are analogous to what is seen when a solution of polymers is led to breakup. In our case, polymers are not in the bulk; they are at the interface of the two fluids! Analysis of the profiles of the neck in both cases showed that profiles are self-similar. Qualitatively, they share features with profiles observed in the case of breakup of interfaces between simple fluids. Quantitatively, slopes and angles are different.

Das Wechselspiel zwischen String- und Eichtheorien hat in den letzten Jahren zu vielen neuen Einsichten geführt. Das herausragendste Beispiel ist die sogenannte AdS/CFT Korrespondenz, eine Dualität zwischen Stringtheorien auf Anti-de Sitter-Räumen (AdS) und konformen Eichtheorien auf deren Rand. Die Untersuchung von Stringtheorie auf ebenfrontigen Gravitationswellen, die sich im sogenannten Penrose-Limes aus AdS-Raumzeiten gewinnen lassen, erlaubt es, diese Dualität über die niederenergetische Supergravitationsnäherung hinausgehend zu überprüfen. Verallgemeinerte ebenfrontige Gravitationswellen sind auch für sich gesehen interessant, da sie eine grosse Klasse von Raumzeiten bilden, die exakte klassische Lösungen der Stringtheorie sind. In dieser Arbeit werden Aspekte der Stringtheorie auf ebenfrontigen Gravitationswellen untersucht. Besonderes Interesse gilt dabei der Verbindung dieser Stringtheorien zu Eichtheorien. Wechselwirkungen von Strings in derjenigen Gravitationswellen-Raumzeit mit maximaler Supersymmetrie werden im Rahmen der Lichtkegel-Stringfeldtheorie behandelt. Viele Ergebnisse, die für den Fall der flachen Minkowski-Raumzeit bekannt sind, werden dabei vollständig auf die komplizierteren ebenfrontigen Gravitationswellen verallgemeinert. Die führenden nicht-planaren Korrekturen zu den anomalen Dimensionen von Operatoren in der Eichtheorie, die eine duale Beschreibung von Stringzuständen liefern, werden innerhalb der Lichtkegel-Stringfeldtheorie reproduziert. / The interplay between string and gauge theory has led to many new insights in recent years. The most prominent example is the AdS/CFT correspondence, a duality between string theory on Anti-de Sitter (AdS) spaces and conformal gauge theories defined on their boundary. The study of string theory on plane wave backgrounds, which are connected to AdS by the Penrose limit, opens up the possibility of testing this duality beyond the low-energy supergravity approximation. Generalized plane wave geometries are interesting in themselves, as they provide a large class of exact classical space-time backgrounds for string theory. In this thesis aspects of string theory on plane wave backgrounds are studied, with an emphasis on the connection to gauge theory. String interactions in the plane wave space-time with maximal supersymmetry are investigated in the framework of light-cone string field theory. In the process, many results that had been found for the case of flat Minkowski space-time are generalized to the more complex plane wave background. The leading non-planar corrections to the anomalous dimensions of gauge theory operators dual to string states are recovered within light-cone string field theory.

In meiner Doktorarbeit habe ich das Potential zwischen zwei statischen Quarks in der Confinement ``Phase'' des SU(2) Higgs Modells untersucht. Statische Quarks sind externe Quellen in der fundamentalen Darstellung der Eichgruppe. In reinen nicht-Abelschen Eichtheorien w\"achst das Potential zwischen einem statischen Quark und einem statischen Anti-quark (statisches Potential genannt) linear mit dem Abstand zwischen den Quarks. Dieses Verhalten des Potentials wird lineares Confinement genannt und wurde mit Gittersimula tionen bis zu grossen Abst\"anden und nahe am Kontinuumslim es beobachtet. Wenn dynamische Materiefelder vorhanden sind, wird erwartet, dass das statische Potential bei grossen Abst\"anden abflacht: Der Grund ist die Abschirmung der statischen Quarks durch Paarerzeugung von leichten Quark Anti-quark Paaren. Die Abflachung des statischen Potentials nennt man String Breaking. Der Stand der Dinge am Anfang meiner Doktorarbeit war, dass String Breaking in nicht-Abelschen Eichtheorien mit Materiefeldern noch nicht beobachtet wurde. Im Gegenteil, die Gittersimulationen von QCD mit dynamischen Fermionen zeigten (und zeigen noch) einen linearen Zuwachs des Potentials bei Abst\"anden, wo das String Breaking eigentlich erwartet wird (aus einer Sch\"atzung in der quenched Approximation der QCD). Die Confinement ``Phase'' im SU(2) Higgs Modell hat Eigenschaften, die der QCD \"ahnlich sind, insbesondere wird das String Breaking erwartet. Deswegen ist die Bestimmung des statischen Potentials im SU(2) Higgs Modell eine wichtige Untersuchung der relevanten Eigenschaften des String Breaking Ph\"anomens. Ich habe das SU(2) Higgs Modell in der Confinement ``Phase'' auf dem Gitter simuliert: Die Resultate zeigen deutlich das String Breaking. Desweiteren kann auch das erste angeregte statische Potential bestimmt werden. Der entscheidende Punkt sind die Korrelationen, die man benutzt, um das statische Potential zu bestimmen. In der reinen Eichtheorie wird das statische Potential aus den Wilson Loops bestimmt, die den ``String Zustand'' des Eichfeldes gut beschreiben. String steht hier f\"ur die Eichfeldkonfiguration, die das lineare Confinement der Quarks verursacht. In Anwesenheit von Materiefeldern erwartet man, dass bei grossen Abst\"anden das statische Pot ential durch das Potential zwischen zwei statisch- leichten Mesonen (Bindungszust\"anden eines statischen Quarks mit dem dynamischen leichten Quarkfeld) beschrieben wird. Die Methode, die ich verwendet habe, um das statische Potential zu bestimmen, basiert auf eine Mischung von ``String-'' und ``Zwei-Meson Zust\"anden''. Mit einem Variationsprinzip wird die beste lineare Kombination solcher ``Zust\"anden'' bestimmt, welche die Eigenzust\"ande des Hamiltonoperators approximiert. Dank der Bestimmung des ersten angeregten Potentials, konnte auch die Interpretation des String Breakings als Level Crossing Ph\"anomen zwischen ``String'' und ``Meson Zust\"anden'' best\"atigt werden. In dem zweiten Teil meiner Doktorarbeit habe ich die Frage des ``Kontinuumlimes'' untersucht. Das String Breaking wurde f\"ur einen speziellen Satz von Parametern beobachtet: die Frage war, wie stark diese Resultate vom gew\"ahlten Gitterabstand abh\"angig sind (Cutoff-Effekte). Diese Frage f\"uhrt unmittelbar zur Untersuchung von Linien konstanter Physik im Parameterraum des SU(2) Higgs Modells. Obwohl in m einer Arbeit noch keine definitive Methode gefunden worden ist, um diese Linien zu konstruieren, konnte ich das Skalierungsverhalten der statischen Potentiale bei Variation des Gitterabstandes um einen Faktor zwei untersuchen. Die Resultate zeigen \"uberraschend kleine Cutoff-Effekte! Die M ethode, welche ich in meiner Arbeit verwendet habe, ist auch in der QCD zu verwenden, um das String Breaking zu beobachten. / The static potential in the confinement ``phase'' of the SU(2) Higgs model is studied. In particular, the observation of the screening (called {\em string breaking}) of the static quarks by the dynamical light quarks leading to the formation of two static-light mesons was not observed before my work in non-Abelian gauge theories. The tool that I employ is lattice gauge simulation. The observable from whic h the spectrum of the Hamiltonian in presence of two static quarks can be extracted, is a matrix correlation whose elements are constructed not only from string-type states represented by Wilson loops (like in pure gauge theories). Additional matrix elements representing transitions from string-type to meson-type states and the propagation of meson-type states are taken into account. From this basis of states it is possible to extract the ground state and first excited state static potentials employing a variational method. The crossing of these two energy levels in the string breaking region is clearly visible and the inadequacy of the Wilson loops alone can be demonstrated. I also address the question of the lattice artifacts. For this purpose lines of constant physics in the confinement ``phase'' of the model have to be constructed. This problem has only partially been solved. Nevertheless it is possible to show that the static potentials have remarkable scaling properties under a variation of the lattice spacing by a factor two and are almost independent of the quartic Higgs coupling.

This submission comprises a portfolio of fifteen original musical works and an exegesis that comments on five of these works. Recordings of twelve of the fifteen compositions are included. These pieces demonstrate an ongoing investigation into structure, and the discussion will provide an insight into the constant process of experimentation and consolidation involved in developing such a body of work. In the exegesis I open with a general conversation on the compositional process and then focus on the formal problems inherent in this process. I then discuss the five scores included in the main volume, looking at how each are formed, and comparing their formal characteristics. This involves an analysis of the musical materials and how such materials are treated through repetition and transformation. I will also look at the aesthetic and stylistic concerns and how they inform the formal architecture of each work. An appendix includes the scores of a further ten works, with a brief introductory commentary on each. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1351235 / Thesis (Ph.D.) -- University of Adelaide, Elder Conservatorium of Music, 2008

Black Snow, an orchestral work composed by Michael Smetanin in 1987, was named after the book Black Snow by Mikhael Bulgakov. Newspaper articles, reviews and the literature researched, all comment on Smetanin’s style and on the influences that shaped that style. The aggressive and confrontational style of much of Smetanin’s music can be attributed partly to his love of rock music and jazz and partly to his mentor in the Netherlands, Louis Andriessen. The same sources quote other composers who also influenced Smetanin’s style. Three works in particular are named, that is, Trans by Stockhausen, Keqrops by Xenakis and De Tijd by Andriessen. It was decided, in the light of previous investigations into Smetanin’s music, to take one of these composers, namely Stockhausen and his work Trans, and discover how much Smetanin was influenced by this composer and this particular work. Trans was chosen because the similarities with Black Snow are less obvious. All aspects of Black Snow were examined - namely the harmony, rhythms, the important textures, serial/mathematical techniques, orchestration, the dramatic program, how the instruments are played - and then compared with Trans for similarities and differences. The results of the analytical investigation show that, while the internal organisation of the two works is very different, there are significant similarities between the two works in most of these areas. Serial/mathematical techniques could only be demonstrated in one area, and this is only conjecture.

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-01-10T14:58:33Z No. of bitstreams: 1 franciscodelgaudiooliveirafigeuiredo.pdf: 778762 bytes, checksum: 462fd065a0a2a277102c64e0a2ecf79c (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-01-23T11:51:06Z (GMT) No. of bitstreams: 1 franciscodelgaudiooliveirafigeuiredo.pdf: 778762 bytes, checksum: 462fd065a0a2a277102c64e0a2ecf79c (MD5) / Made available in DSpace on 2018-01-23T11:51:06Z (GMT). No. of bitstreams: 1 franciscodelgaudiooliveirafigeuiredo.pdf: 778762 bytes, checksum: 462fd065a0a2a277102c64e0a2ecf79c (MD5) Previous issue date: 2017-03-02 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / As exigências de localidade, positividade dos estados e positividade da energia dão origem a comportamentos ruins dos campos quânticos em distâncias pequenas (singularidadesUV). Quando tenta-se construir campos quânticos para partículas de spin s ≥ 1 que satisfazem esse princípios fundamentais, acaba-se ganhando interações não-renormalizaveis. Para spins um e dois, existem campos, no contexto de teorias de calibre, com o mesmo bom comportamento UV que o campo escalar para spin zero. Entretanto, é necessária a introdução de um espaço de estados não-físico, assim como campos não-físicos (ghosts). Motivado por trabalhos anteriores, nós investigamos campos quânticos, para bósons massivos de spin arbitrário, possuindo o mesmo comportamento UV que o campo escalar (s = 0), porém que agem num espaço de Hilbert sem ghosts e são covariantes por transformações de Poincaré. Esses campos, entretanto, não possuem mais localização pontual, estando localizados, ao invés, em semi-retas no espaço de Minkowski que se extendem em direções tipo-luz (strings tipo-luz). / The combined requirements of locality, positivity of states and positivity of energy lead to bad short distance behaviour of quantum fields (UV singularities). When one tries to build quantum fields for particles of spin s ≥ 1 that still satisfy these fundamental principles, one ends up with non-renormalizable interactions. For spin one and two, there exist fields in the context of gauge theory with the same good UV behaviour as the scalar field for spin zero. However, for this one has to introduce an unphysical state space, as well as unphysical fields (ghosts). Motivated by previous works, we begin to investigate quantum fields, for massive bosons of any spin, that have the same good UV behaviour as the scalar field (s = 0), act in a Hilbert space without ghosts and are Poincaré covariant. These fields are, however, no longer point-local, being localized instead on semi-infinite lines in Minkowski space extending to lightlike infinity (lightlike strings).

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-08-18T17:45:24Z No. of bitstreams: 1 lucastavarescardoso.pdf: 837625 bytes, checksum: 3abd29cb3035fdd6ec6e11d4ea0ae1ae (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-08-24T12:02:18Z (GMT) No. of bitstreams: 1 lucastavarescardoso.pdf: 837625 bytes, checksum: 3abd29cb3035fdd6ec6e11d4ea0ae1ae (MD5) / Made available in DSpace on 2017-08-24T12:02:18Z (GMT). No. of bitstreams: 1 lucastavarescardoso.pdf: 837625 bytes, checksum: 3abd29cb3035fdd6ec6e11d4ea0ae1ae (MD5) Previous issue date: 2017-08-03 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A construção de campos com localização em cordas foi realizada rigorosamente há pouco mais de uma década. Nesta abordagem, os campos são operadores em algum espaço de Hilbert, e portanto não há graus de liberdade não-físicos tais como "ghosts". Além de permitir a construção de campos carregados inteiramente num espaço espaço de Hilbert, os campos com localização em cordas exibem um bom comportamento no regime ultravioleta e, entre outras características, são possíveis candidatos para descreverem consistentemente a matéria escura. No intuito de obter uma prova da renormalizabilidade em modelos perturbativos no esquema de Epstein-Glaser com campos quânticos localizados em cordas, é necessário evidenciar a liberdade que se tem ao definir produtos temporalmente ordenados do Lagrangeano de interação. Este trabalho proporciona um primeiro passo significativo nesta direção. O problema básico é a presença de um conjunto aberto de n-uplas de cordas que não podem ser cronologicamente ordenadas. Nós resolvemos este problema ao mostrar que quase todas (i.e. exceto num subconjunto de medida nula) tais configurações de cordas podem ser dissecadas num número finito de pedaços, os quais por sua vez podem ser cronologicamente ordenados. Com isso, tem-se que o produto temporalmente ordenado de fatores lineares de campos está fixo fora de um conjunto de medida nula de configurações de cordas. A construção do ordenamento temporal geométrico de cordas é feita de modo a servir para o estudo da renormalizabilidade de quaisquer teorias quânticas de campos com localização em cordas. / The construction of string-localized fields was rigorously accomplished a little over a decade ago. In this approach, the fields are operators in some Hilbert space, and therefore there are no unphysical degrees of freedom such as ghosts. In addition to allowing the construction of charged fields entirely in a Hilbert space, the string-localized fields exhibit, in general, a good behavior in the ultraviolet regime and, among other features, the class (representation) of string-localized fields with m = 0 and s = oo are possible candidates to consistently describe dark matter. In order to obtain a proof of renormalizability of perturbative models in the Epstein—Glaser scheme with string-localized quantum fields, one needs to know what freedom one has to define time-ordered products of the interaction Lagrangian. This work provides a first significant step in that direction. The basic issue is the presence of an open set of n-tuples of strings which cannot be chronologically ordered. We resolve it by showing that almost all (i.e. outside a null set) such string configurations can be dissected into finitely many pieces which can indeed be chronologically ordered. This fixes the time-ordered products of linear field factors outside a nullset of string configurations. The construction of the geometric time ordering of strings is realized in such a way that it will serve to study the renormalizability of any quantum field theories with string-localized fields

In this project we review the method of using c-extremization and computing anomalies to obtain AdS/CFT theories. We start with a quick introduction to CFT's and AdS/CFT correspondence which gives us the tools to later understand the 2D N= (2,0) SCFT and its gravity duals in particular AdS_5xS^5 and AdS_7xS^4 compactified on Riemann surfaces.