Applying Hallgren’s algorithm for solving Pell’s equation to finding the irrational slope of the launch of a billiard ball

This thesis is an exploration of Quantum Computing applied to Pell’s equation in an attempt to find solutions to the Billiard Ball Problem. Pell’s equation is a Diophantine equation in the form of x2 − ny2 = 1, where n is a given positive nonsquare integer, and integer solutions are sought for x and y. We will be applying Hallgren’s algorithm for finding irrational periods in functions, in the context of billiard balls and their movement on a friction-less unit square billiard table. Our central research question has been the following: Given the cutting sequence of the billiard ball’s movement, can you find the irrational slope value in which the billiard ball was put in motion

Cyclic cohomology for graded C∗,rC^{*,r}-algebras and its pairings with van Daele KK-theory

We consider cycles for graded $C^{*,r}$-algebras (Real $C^{*}$-algebras) which are compatible with the $*$-structure and the real structure. Their characters are cyclic cocycles. We define a Connes type pairing between such characters and elements of the van Daele $K$-groups of the $C^{*,r}$-algebra and its real subalgebra. This pairing vanishes on elements of finite order. We define a second type of pairing between characters and $K$-group elements which is derived from a unital inclusion of $C^{*}$-algebras. It is potentially non-trivial on elements of order two and torsion valued. Such torsion valued pairings yield topological invariants for insulators. The two-dimensional Kane-Mele and the three-dimensional Fu-Kane-Mele strong invariant are special cases of torsion valued pairings. We compute the pairings for a simple class of periodic models and establish structural results for two dimensional aperiodic models with odd time reversal invariance.Comment: 57 page

Boundary algebras and Kac modules for logarithmic minimal models

Virasoro Kac modules were initially introduced indirectly as representations whose characters arise in the continuum scaling limits of certain transfer matrices in logarithmic minimal models, described using Temperley-Lieb algebras. The lattice transfer operators include seams on the boundary that use Wenzl-Jones projectors. If the projectors are singular, the original prescription is to select a subspace of the Temperley-Lieb modules on which the action of the transfer operators is non-singular. However, this prescription does not, in general, yield representations of the Temperley-Lieb algebras and the Virasoro Kac modules have remained largely unidentified. Here, we introduce the appropriate algebraic framework for the lattice analysis as a quotient of the one-boundary Temperley-Lieb algebra. The corresponding standard modules are introduced and examined using invariant bilinear forms and their Gram determinants. The structures of the Virasoro Kac modules are inferred from these results and are found to be given by finitely generated submodules of Feigin-Fuchs modules. Additional evidence for this identification is obtained by comparing the formalism of lattice fusion with the fusion rules of the Virasoro Kac modules. These are obtained, at the character level, in complete generality by applying a Verlinde-like formula and, at the module level, in many explicit examples by applying the Nahm-Gaberdiel-Kausch fusion algorithm.Comment: 71 pages. v3: version published in Nucl. Phys.

Noncommutative Spheres and Instantons

We report on some recent work on deformation of spaces, notably deformation of spheres, describing two classes of examples. The first class of examples consists of noncommutative manifolds associated with the so called $\theta$-deformations which were introduced out of a simple analysis in terms of cycles in the $(b,B)$-complex of cyclic homology. These examples have non-trivial global features and can be endowed with a structure of noncommutative manifolds, in terms of a spectral triple (\ca, \ch, D). In particular, noncommutative spheres $S^{N}_{\theta}$ are isospectral deformations of usual spherical geometries. For the corresponding spectral triple (\cinf(S^{N}_\theta), \ch, D), both the Hilbert space of spinors \ch= L^2(S^{N},\cs) and the Dirac operator $D$ are the usual ones on the commutative $N$-dimensional sphere $S^{N}$ and only the algebra and its action on $\ch$ are deformed. The second class of examples is made of the so called quantum spheres $S^{N}_q$ which are homogeneous spaces of quantum orthogonal and quantum unitary groups. For these spheres, there is a complete description of $K$-theory, in terms of nontrivial self-adjoint idempotents (projections) and unitaries, and of the $K$-homology, in term of nontrivial Fredholm modules, as well as of the corresponding Chern characters in cyclic homology and cohomology.Comment: Minor changes, list of references expanded and updated. These notes are based on invited lectures given at the ``International Workshop on Quantum Field Theory and Noncommutative Geometry'', November 26-30 2002, Tohoku University, Sendai, Japan. To be published in the workshop proceedings by Springer-Verlag as Lecture Notes in Physic

Spectacular narratives: Twister, independence day, and frontier mythology

Big-screen spectacle has become increasingly important to Hollywood in recent decades. It formed a central part of a post-war strategy aimed at tempting lost audiences back to the cinema in the face of demographic changes and the development of television and other domestic leisure activities. More recently, in an age in which the big Hollywood studios have become parts of giant conglomerates, the prevalence of spectacle and special effects has been boosted by a demand to engineer products that can be further exploited in multimedia forms such as computer games and theme-park rides, secondary outlets that can sometimes generate more profits than the films on which they are based. These and other developments have led some commentators to announce, or predict, the imminent demise of narrative as a central component of Hollywood cinema. But the case has been considerably overstated. Narrative is far from being eclipsed, even in the most spectacular and effects-oriented of today’s blockbuster attractions. These films still tend to tell reasonably coherent stories, even if they may sometimes be looser and less well integrated than classical models. More important for my argument, contemporary spectaculars also continue to manifest the kinds of underlying thematic oppositions and reconciliations associated with a broadly ‘structuralist’ analysis of narrative. This very important dimension of narrative has been largely ignored by those who identify, celebrate or more often bemoan a weakening of plot or character development in many spectacular features

Bulk and Boundary Invariants for Complex Topological Insulators: From K-Theory to Physics

This monograph offers an overview on the topological invariants in fermionic topological insulators from the complex classes. Tools from K-theory and non-commutative geometry are used to define bulk and boundary invariants, to establish the bulk-boundary correspondence and to link the invariants to physical observables.Comment: Monograph in Springer Series in Mathematical Physics Studies, see ISBN below. Correction of a few remaining typos. ISBN 978-3-319-29350-9, eBook ISBN 978-3-319-29351-6, (Springer, 2016