Browsing by Subject "Holography"
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Item A laser plotter for optical processing(Texas Tech University, 1982-05) Jones, Bailey HenryNot availableItem Chiral symmetry breaking and external fields in the Kuperstein-Sonnenschein model(2012-05) Alam, Muhammad Sohaib; Kaplunovsky, Vadim; Paban, SoniaA novel holographic model of chiral symmetry breaking has been proposed by Kuperstein and Sonnenschein by embedding non-supersymmetric probe D7 and anti-D7 branes in the Klebanov-Witten background. We study the dynamics of the probe flavours in this model in the presence of finite temperature and a constant electromagnetic field. In keeping with the weakly coupled field theory intuition, we find the magnetic field promotes spontaneous breaking of chiral symmetry whereas the electric field restores it. The former effect is universally known as the ``magnetic catalysis" in chiral symmetry breaking. In the presence of an electric field such a condensation is inhibited and a current flows. Thus we are faced with a steady-state situation rather than a system in equilibrium. We conjecture a definition of thermodynamic free energy for this steady-state phase and using this proposal we study the detailed phase structure when both electric and magnetic fields are present in two representative configurations: mutually perpendicular and parallel.Item Computer Generated Multiplex Holography(Texas Tech University, 1980-05) Irby, Carl ArthurNot Available.Item Correlation properties of diffusers for multiplex holography(Texas Tech University, 1979-08) Kral, Edward LeeA promising method of representing two-dimensional space-variant optical systems is through multiplex holography. The multiplexing operation requires the use of diffusers in the reference beam path to provide a unique code for each object wave. In this thesis, various types of diffusers are analyzed and compared within the framework of multiplex holography. A simple model is initially developed which can accommodate a wide range of diffuser families, including pure phase, pure amplitude, and combined amplitude and phase diffusers. Crosscorrelation and autocorrelation calculations are then presented for both spherical wave (chirp) illumination and plane wave illumination, and a signal-to-noise analysis based on these calculations is included. Finally, the implications of the analysis are thoroughly discussed, and recommendations for further research are given.Item Dynamics of asymptotically AdS spaces and holography(2015-08) Pedraza Avella, Juan Felipe; Fischler, Willy; Distler, Jacques; Kilic, Can; Neitzke, Andrew; Paban, SoniaThis thesis presents a series of studies on the evolution and out-of-equilibrium dynamics of strongly coupled quantum field theories by means of the AdS/CFT correspondence. We use a handful of analytic and semi-analytic techniques to investigate the response of the system due to different types of perturbations, some of them leading to thermalization, cooling down or coherent oscillations of the quantum fields. We characterize the processes by studying the evolution of non-local observables such as two-point functions, Wilson loops and entanglement entropy. Our results may be relevant to heavy-ion collision and condensed matter physics experiments.Item Fabrication of binary phase diffusers for space-variant processing(Texas Tech University, 1983-12) Chase, Scott BTechniques have previously been described for holographically representing space-variant systems. By spatially sampling the input plane and using phase mask diffusers to encode the multiple reference beams, one can sequentially record holograms exhibiting a minimal amount of crosstalk. Gold-coded binary phase masks have been shown to have good correlation properties with known cross-correlation bounds. This thesis describes a technique which generates phase masks using a laser scanner computer generated hologram (CGH) writing f a c i l i t y at a wavelength of 4579A. Methods for determining the proper resist thickness to achieve the necessary 180 degree phase shift between adjacent cells in a mask include analyzing the data taken by an interference microscope and quantitative analysis of the dc component present in the Fourier spectrum of the mask. Comparisons of the effectiveness of the phase masks with that of ground-glass were obtained using two different tests. First, the phase masks were used in a space-variant processor, and the results of the multiplexed holograms were compared to those obtained earlier using a ground-glass diff user. Secondly, computer-generated holograms were made using the phase masks as diffusers and the results were compared with those previously obtained using amplitude masks.Item Film grain noise limitations in interferometric measurements(Texas Tech University, 1973-05) De Journett, Stewart LanceNot Available.Item Frequency Domain Holography of laser wakefields(2006) Matlis, Nicholas Hill; Downer, Michael CoffinIn this dissertation, single-shot measurement of longitudinal and transverse structure of resonantly driven laser wakefields by Frequency Domain Holography (FDH) is demonstrated. Visualization of laser wakefield structure is crucial for understanding the complex dynamics of the mutual interaction between the driving pulse, wake- field density oscillations and accelerated electron bunch. This diagnostic therefor provides a necessary tool for researchers to learn how to control and fine tune the interaction to produce electron beams with desirable properties. Wakefields were measured in a 2 mm Helium gas jet, for electron densities between 1 x 1018 and 6 x 1018 cm−3 , and laser pulses of 30 fs duration and peak powers between 10 TW and 30 TW. Detailed structural features of the wakefields, including radial extent of the wake, longitudinal wake development, and wavefront curvature, as well as features of the accompanying ionization front and plasma column are resolved. Results are compared with PIC simulations, and show a high degree of correspondence. Weaknesses of the current implementation of the technique and extensions to other parameter regimes are discussed.Item Generalized optical linear filtering of one-dimensional signals(Texas Tech University, 1985-08) Blanchard, Lorena AnnNot availableItem Holographic Representations of Optical Systems.(Texas Tech University, 1975-05) Deen, Lewis MonroeNot Available.Item Investigation on the holographic principle(2003) Jiang, Li; Fischler, WillyThe holographic principle asserts that any given codimension two spacelike surface limits the information content of adjacent regions. We first review various entropy bounds which lead to the formulation of this conjecture, putting great emphasis on the UV-IR connection. We propose to use noncommutative field theory as a toy model to study the holographic mapping mechanism. In particular, we investigate how the fundamental dipole structure emerges in noncommutative gauge theories by using matrix formulation. The momentum dependent growing behavior of the dipoles can provide a simple way to map the bulk degrees of freedom onto the boundary. In the context of the AdS/CFT correspondence, which is the best known example of a holographic theory, we study the thermodynamics of N = 4 supersymmetric Yang-Mills theory at two-loop level and compare the result to the supergravity calculation. This provides an excellent example to illustrate the idea of strong/weak duality. Questions about a possible large N phase transition still remain unsolved.Item Laboratory visualization of laser-driven plasma accelerators in the bubble regime(2010-08) Dong, Peng; Downer, Michael Coffin; Becker, Michael; Ditmire, Todd; Lang, Karol; Shvets, GennadyAccurate single-shot visualization of laser wakefield structures can improve our fundamental understanding of plasma-based accelerators. Previously, frequency domain holography (FDH) was used to visualize weakly nonlinear sinusoidal wakes in plasmas of density n[subscript e] < 0.6 × 10¹⁹/cm³ that produced few or no relativistic electrons. Here, I address the more challenging task of visualizing highly nonlinear wakes in plasmas of density n[subscript e] ~ 1 to 3× 10¹⁹/cm³ that can produce high-quality relativistic electron beams. Nonlinear wakes were driven by 30 TW, 30 fs, 800 nm pump pulses. When bubbles formed, part of a 400 nm, co-propagating, overlapping probe pulse became trapped inside them, creating a light packet of plasma wavelength dimensions--that is, an optical "bullet"--that I reconstruct by FDH methods. As ne increased, the bullets first appeared at 0.8 × 10¹⁹/cm³, the first observation of bubble formation below the electron capture threshold. WAKE simulations confirmed bubble formation without electron capture and the trapping of optical bullets at this density. At n[subscript] >1× 10¹⁹/cm³, bullets appeared with high shot-to-shot stability together with quasi-monoenergetic relativistic electrons. I also directly observed the temporal walk-off of the optical bullet from the beam-loaded plasma bubble revealed by FDH phase shift data, providing unprecedented visualization of the electron injection and beam loading processes. There are five chapters in this thesis. Chapter 1 introduces general laser plasma- based accelerators (LPA). Chapter 2 discusses the FDH imaging technique, including the setup and reconstruction process. In 2006, Dr. N. H. Matlis used FDH to image a linear plasma wakefield. His work is also presented in Chapter 2 but with new analyses. Chapter 3, the main part of the thesis, discusses the visualization of LPAs in the bubble regime. Chapter 4 presents the concept of frequency domain tomography. Chapter 5 suggests future directions for research in FDH.Item Multiplex holography for space-variant optical processing(Texas Tech University, 1979-08) Jones, Mike IvorThis thesis describes extensive experimental implementations of multiplex holography for use in representing two-dimensional spacevariant optical systems. Diffusers are used to encode the reference beams for effective crosstalk suppression. The problem of hologramto-hologram crosstalk is both analytically and experimentally examined, and various methods for its suppression are discussed. The merits of using ground glass diffusers for crosstalk suppression are experimentally investigated, and the superiority of chirped-wave diffuser illumination over plane-wave illumination in crosstalk suppression is demonstrated. The first implementations of binary-coded diffuser masks for crosstalk suppression in multiplex holography are shown. The experimental proof of coherent addition in overlapping holographic outputs is presented, and the first holographic representation of an extremely space-variant optical system is shown. The holographic representation of an optical system using a large (10 x 10) array of input sampling points is also shown. With a working 2-D space-variant holographic processor thus available, a variety of space-variant processing operations for future investigations are suggested.Item Non-supersymmetric holographic engineering and U-duality(2012-08) Young, Stephen Christopher; Fischler, Willy; Caceres, Elena; Paban, Sonia; Dicus, Duane; Freed, DanIn this Ph.D. thesis, we construct and study a number of new type IIB supergravity backgrounds that realize various flavored, finite temperature, and non-supersymmetric deformations of the resolved and deformed conifold geometries. We make heavy use of a U-duality solution generating procedure that allows us to begin with a modification of a family of solutions describing the backreaction of D5 branes wrapped on the S^2 of the resolved conifold, and generate new backgrounds related to the Klebanov-Strassler background. We first construct finite temperature backgrounds which describe a configuration of N_c D5 branes wrapped on the S^2 of the resolved conifold, in the presence of N_f flavor brane sources and their backreaction i.e. N_f/N_c ~ 1. In these solutions the dilaton does not blow up at infinity but stabilizes to a finite value. The U-duality procedure is then applied to these solutions to generate new ones with D5 and D3 charge. The resulting backgrounds are a non-extremal deformation of the resolved deformed conifold with D3 and D5 sources. It is tempting to interpret these solutions as gravity duals of finite temperature field theories exhibiting phenomena such as Seiberg dualities, Higgsing and confinement. However, a first necessary step in this direction is to investigate their stability. We study the specific heat of these new flavored backgrounds and find that they are thermodynamically unstable. Our results on the stability also apply to other non-extremal backgrounds with Klebanov-Strassler asymptotics found in the literature. In the second half of this thesis, we apply the U-duality procedure to generate another class of solutions which are zero temperature, non-supersymmetric deformations of the baryonic branch of Klebanov-Strassler. We interpret these in the dual field theory by the addition of a small gaugino mass. Using a combination of numerical and analytical methods, we construct the backgrounds explicitly, and calculate various observables of the field theory.Item Optical inverse filtering for real-time echo removal(Texas Tech University, 1983-08) Mushtaq, ShehlaNot availableItem Phase transitions in holographic QCD and instanton crystals(2014-08) Alam, Muhammad Sohaib; Kaplunovsky, VadimWe investigate phase transitions in holographic models of QCD. In chapter I, we explore the effect of constant external U(1) fields on the physics of chiral symmetry breaking, as realized in the D3/D7 model. We discover that this model exhibits the phenomenon of magnetic catalysis, which is what one would expect from a weakly coupled field theory intuition. In chapter II, we continue exploring the effect of external U(1) fields but now on the backreacted D3/D7 model, where the backreaction is obtained via a smearing procedure. We again find the magnetic catalysis effect, however the results differ from the previous case depending on the backreaction parameters. In chapter III, we investigate lattices of instantons in the D4/D8 model of chiral symmetry breaking. These instanton lattices can change dimensionality, and in particular we investigate the 1D [right arrow] 2D transition as a simpler case of the more complicated 3D [right arrow] 4D transition which is conjectured to be holographically dual to the baryonic to quarkyonic phase transition. Besides this interpretation, one could also view this as a hypothetical condensed matter system. We have a lattice of instantons dominated by two-body forces, whose interactions depend not only on their mutual distance in physical space but also on their relative orientations in the internal isospace. We obtain a rich variety of instanton crystals whose description could serve to be useful beyond holography.Item Piecewise isoplanatic approximation in space-variant processing(Texas Tech University, 1985-05) Lin, Shing-hongNot availableItem Space-variant coherent optical processing(Texas Tech University, 1977-12) Marks, Robert JacksonNot availableItem Space-variant processing using phase codes and Fourier-plane sampling techniques(Texas Tech University, 1980-05) Kasturi, RangacharAny slowly varying linear space-variant system can, in principle, be represented holographically by spatially sampling the input plane and multiplexing the respective system transfer functions. A scheme reported earlier for implementing this technique makes use of phase diffusers in the reference beam paths to encode sequentially recorded holograms. However to minimize the cross talk between the holograms upon playback the diffusers should have good correlation properties, In this thesis extensive computer simulations to evaluate the correlation properties of a family of binary phase codes are conducted. An alternative multiplexing technique in which the transfer functions are sampled in the Fourier plane to generate a composite hologram is also described. In this technique the samples of the transfer functions are placed in non-overlapping regions and hence there will be no crosstalk upon playback. However multiple copies of the input function are required during the playback step. The results of preliminary experiments conducted to evaluate this approach for space-variant system representation are presented including the verification of coherent addition using computer multiplexed holograms.Item String theory, holography, and UV-IR mixing(2002-05) McNees, Robert Alfred; Fischler, Willy