Browsing by Subject "Confinement"
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Item Abelian and non-Abelian strings(2017-06) Monin, SergiiWe study world-sheet theories of Abelian and non-Abelian strings that arise in different models. Considering a model in which Abelian (Abrikosov-Nielsen-Olesen) string acquires rotational (quasi)moduli we analyze the parameter space to find examples in which these strings not only coexist but are degenerate in tension. We prove that both solutions are locally stable, i.e there are no negative modes in the string background. The tension degeneracy is achieved at the classical level and is expected to be lifted by quantum corrections. Moreover, using a representative set of parameters we numerically calculate the low-energy Lagrangian on the world sheet of the Abrikosov-Nielsen-Olesen string. The bulk model is deformed by a spin-orbit interaction generating a number of ``entangled" terms on the string world sheet. We also consider modifications of ${\mathcal N}=2\;$ supersymmetric QCD with the U$(N)$ gauge group and $N_f=N$ quark flavors. These models support non-Abelian strings. The dynamics of the orientational modes is described by two-dimensional CP$(N-1)$ model with varying degrees of supersymmetry. We used analytical methods to solve the CP$(N-1)\;$ model at finite string length $L$ assuming periodic boundary conditions. In the pure bosonic theory in the large-$N$ limit we detect a phase transition at $L\sim \Lambda_{\rm CP}^{-1}$ (which is expected to become a rapid crossover at finite $N$). At large $L$ the CP$(N-1)$ model develops a mass gap and is in the Coulomb/confinement phase, while at small $L$ it is in the deconfinement phase. In the ${\mathcal N}=(2,2)\;$ supersymmetric CP$(N-1)$ model at finite $L$ we find a large-$N$ solution which was not known previously. We use the power of holomorphy to deduce that the theory has a single phase independently of the value of $L\Lambda_{\rm CP}$. For any value of this parameter a mass gap develops and supersymmetry remains unbroken. So does the $SU(N)$ symmetry of the target space. In the heterotic ${\mathcal N}=(0,2)\;$ CP$(N-1)\;$ model we find a rich phase structure and discuss how it matches the ${\mathcal N}=(2,2)\;$ limit.Item Effect of FRCM Repair on the Bond Behavior of Corroded Reinforced Concrete Beams Subjected to Static and Cyclic Loading(2017-08) Anderson, MirandaThis paper presents the evaluation of the effectiveness of Fiber Reinforced Cementitious Matrix (FRCM) repair in improving the bond behavior of corroded reinforced concrete beams under both static and fatigue loading. The study consisted of 30 full-scale beams, both corroded and uncorroded. The variables used in this study were corrosion level based on mass loss, repair method used, type of loading (monotonic or repeated loading), and load range applied. Corrosion was found to reduce the fatigue strength of reinforced concrete beams by introducing internal stresses in the concrete that ultimately cause reduction in the bond between the reinforcement and the surrounding concrete. FRCM was found to increase the fatigue strength of corroded concrete beams by providing confinement, thus making it an effective method for repairing beams damaged from corrosion. The use of a cementitious substrate with FRCM allowed for easier monitoring of the cracks developed in the concrete while testing.Item Equilibrium properties of DNA and other semiflexible polymers confined in nanochannels(2016-01) Muralidhar, AbhiramRecent developments in next-generation sequencing (NGS) techniques have opened the door for low-cost, high-throughput sequencing of genomes. However, these developments have also exposed the inability of NGS to track large scale genomic information, which are extremely important to understand the relationship between genotype and phenotype. Genome mapping offers a reliable way to obtain information about large-scale structural variations in a given genome. A promising variant of genome mapping involves confining single DNA molecules in nanochannels whose cross-sectional dimensions are approximately 50 nm. Despite the development and commercialization of nanochannel-based genome mapping technology, the polymer physics of DNA in confinement is only beginning to be understood. Apart from its biological relevance, DNA is also used as a model polymer in experiments by polymer physicists. Indeed, the seminal experiments by Reisner et al. (2005) of DNA confined in nanochannels of different widths revealed discrepancies with the classical theories of Odijk and de Gennes for polymer confinement. Picking up from the conclusions of the dissertation of Tree (2014), this dissertation addresses a number of key outstanding problems in the area of nanoconfined DNA. Adopting a Monte Carlo chain growth technique known as the pruned-enriched Rosenbluth method, we examine the equilibrium and near-equilibrium properties of DNA and other semiflexible polymers in nanochannel confinement. We begin by analyzing the dependence of molecular weight on various thermodynamic properties of confined semiflexible polymers. This allows us to point out the finite size effects that can occur when using low molecular weight DNA in experiments. We then analyze the statistics of backfolding and hairpin formation in the context of existing theories and discuss how our results can be used to engineer better conditions for genome mapping. Finally, we elucidate the diffusion behavior of confined semiflexible polymers by comparing and contrasting our results for asymptotically long chains with other similar studies in the literature. We expect our findings to be not only beneficial to the design of better genome mapping devices, but also to the fundamental understanding of semiflexible polymers in confinement.Item Modeling DNA electrophoresis in confined geometries.(2010-08) Laachi, NabilSize-based DNA separation is at the heart of numerous biological applications. While gel electrophoresis remains widely utilized to fractionate DNA according to their size, the method has several shortcomings. Recent advances in micro- and nano-fabrication techniques engendered several microfabricated devices aimed at addressing some of the limitations of gel electrophoresis for DNA separations. In this thesis, we employ a combination of analytical and computational methods to characterize the electrophoretic motion of DNA molecules in microfabricated, confining geometries. In particular, we consider three situations: (i) the migration of short DNA in nanofilters (a succession of narrow slits, connecting deep wells) under a high electric field; (ii) the metastable unhooking of a long DNA chain wrapped around a cylindrical post; and (iii) the dynamics of long DNA chains in an array of spherical cavities connected by nanopores. We provide insights on the physical mechanisms underlying the transport of DNA in such geometries. Useful guidelines for the optimal design of new separation devices result from the fundamental understanding gained by the approach we propose.Item Topics in generalized symmetries in the continuum and on the lattice(2023-06) Jacobson, TheodoreThis dissertation explores topics in quantum field theory from the perspective of generalized symmetries. Driven by new ideas in condensed matter and high energy physics, the notion of symmetry has been significantly expanded in recent years, giving rise to new insights and constraints on strongly-coupled quantum field theories. In this thesis we focus on the implications of higher-form symmetries for confining gauge theories, and discuss lattice discretizations of continuum quantum field theories where such global symmetries can be analyzed in a concrete setting. In the continuum, we examine the interplay between confinement and 1-form symmetries in gauge theories. We point out that in two spacetime dimensions, theories with 1-form symmetries necessarily have relevant deformations which directly impact confinement. We also show that SU(N) QCD with fundamental quarks has no emergent 1-form symmetry in the large N limit, despite the fact that the theory is confining at large N. On the lattice, we employ a recently-discovered approach known as the modified Villain formulation to discretize abelian Chern-Simons theory. We take particular care to maintain its global structure, symmetries, and 't Hooft anomalies at the lattice level. This thesis also contains an introduction to some basic concepts in generalized symmetries along with illustrative examples.Item Writing beyond Redress: Slavery and the Work of Literature(2019-07) Gildersleeve, CourtneyWriting beyond Redress: Slavery and the Work of Literature is a comparative study of literary works by Afro-Caribbean writers which illuminate the entanglements of slavery, imperialism, and imprisonment. Spanning a period from the early nineteenth century to the early twenty-first century, the project traces in literary writing a dialectic of confinement and emancipation in the long fight against the system of slavery and its attendant ideologies. Each chapter focuses on a primary text that foregrounds either a specific site of confinement during slavery, or an instantiation of its afterlife: the prison (The Memoir of General Toussaint Louverture, by Louverture himself), the sugar plantation (Autobiografía de un esclavo, Juan Francisco Manzano), the isolated peasant village (Gouverneurs de la rosée, Jacques Roumain), and the immigration detention center (Brother, I’m Dying, Edwidge Danticat). Calling us to rethink the labor involved in the act of writing and the stakes—including physical risk—of speaking from within and against systems of oppression, these texts illuminate the inhibitions of speech and activity that slavery and the institutions that arose in its aftermath were designed to maintain. Confronting, too, the often dissimulating uses of language by the dominant society, these texts reimagine the potency of the written word to combat social wrongs and to forge other possible forms of social being. While writing alone cannot redress the damages of slavery, at the same time, writing must be claimed for the ongoing work of emancipation.