# Browsing by Subject "Holography"

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Item Chiral symmetry breaking and external fields in the Kuperstein-Sonnenschein model(2012-05) Alam, Muhammad Sohaib; Kaplunovsky, Vadim; Paban, SoniaShow more A 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.Show more Item Dynamics of asymptotically AdS spaces and holography(2015-08) Pedraza Avella, Juan Felipe; Fischler, Willy; Distler, Jacques; Kilic, Can; Neitzke, Andrew; Paban, SoniaShow more This 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.Show more Item Frequency Domain Holography of laser wakefields(2006) Matlis, Nicholas Hill; Downer, Michael CoffinShow more In 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.Show more Item Investigation on the holographic principle(2003) Jiang, Li; Fischler, WillyShow more The 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.Show more 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, GennadyShow more Accurate 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.Show more Item Measuring frame-dragging with LARES, and other topics in gravity(2017-05) Nguyen, Phuc Hong; Matzner, Richard A. (Richard Alfred), 1942-; Fischler, Willy; Paban, Sonia; Kilic, Can; Sadun, LorenzoShow more This dissertation is divided into two conceptually distinct parts, which both fall under the broad umbrella of gravitational physics. In the first part, we describe work done on the LARES experiment whose goal is to measure the Lense-Thirring effect of general relativity. We first review the derivation of the Lense-Thirring effect, then review past experimental efforts to confirm it, and finally describe our work to help model one of the major error sources of the experiment. In the second part, we give two sample of work done in the area of holography. The first sample presents a toy model for Schwinger pair creation in de Sitter space. The second sample establishes a link between quantum complexity and the thermodynamic volume of black holes.Show more Item Non-supersymmetric holographic engineering and U-duality(2012-08) Young, Stephen Christopher; Fischler, Willy; Caceres, Elena; Paban, Sonia; Dicus, Duane; Freed, DanShow more In 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.Show more Item Phase transitions in holographic QCD and instanton crystals(2014-08) Alam, Muhammad Sohaib; Kaplunovsky, VadimShow more We 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.Show more Item String theory, holography, and UV-IR mixing(2002-05) McNees, Robert Alfred; Fischler, WillyShow more Item Studies in holographic complexity(2021-05-06) Couch, Josiah D.; Fischler, Willy; Aaronson, Scott; Distler, Jacques; Kilic, Can; Paban, SoniaShow more This dissertation will present the work I have done on the conjectured relationship between various bulk quantities designed to capture the growth of the wormhole in eternal black hole spacetimes and the circuit complexity of the boundary state within the context of the AdS/CFT correspondence, i.e., on the topic of ’holographic complexity.’ Four papers are presented here, each focused on the bulk side of this proposed relationship. In these papers, my various co-authors and I seek to improve our understanding of the bulk quantities in question (action of a causal diamond, maximal volume) and test the internal consistency of these proposals and their consistency with our intuition and understanding of the boundary field theory. In particular, the first of these papers focuses on properties of maximal volume slices in black hole spacetimes, along with consequences for the ’complexity = volume’ conjecture. The next paper considers whether ’complexity = action’ is consistent with the intuition we develop about the time evolution of the boundary circuit complexity in space-times dual to non-commutative field theories. The third paper deals with a possible relationship between the rate of increase of complexity and the thermodynamic volume of black hole spacetimes. Finally, the last paper deals with restrictions of the ’complexity = action’ and ’complexity = volume’ conjectures to boundary subregions and their corresponding entanglement wedges and seeks to test the consistency of a conjecture relating these restrictions to the purification complexity of the reduced density matrixShow more Item Topics in Higgs phenomenology and holographic complexity(2018-06-13) Xiao, Minglei; Fischler, Willy; Distler, Jacques; Kaplunovsky, Vadim; Kilic, Can; Shapiro, PaulShow more This dissertation presents four sample work which are divided into two very distinct categories. The first category is particle phenomenology, for which I show a series of study on the Higgs potential effects. One effect is its vacuum stability, controlled by the renormalization group running of the Higgs self coupling. The other is the impact on baryogenesis from the electroweak phase transition. A scalar-assisted vector-like fermion model is used to study the two effects, and experimental constraints are found for this model. The second category is holography, or specifically the holographic complexity. Both the time dependence and the UV divergence structure for holographic complexity are investigated. The former is done for a class of finite temperature non-commutative field theory, where both late time behavior and finite time behavior are analysed. For the UV divergence structure study, we choose the 3D kink subregion on the boundary, which is the simplest subregion with singular surface. Properties of subregion complexity are examined.Show more Item Using complex light modulation for holographic applications(2016-05) Parthiban, Vikraman; Becker, Michael F.; Bovik, Alan CShow more Complex light modulation is the ability to control a light-wave’s phase and amplitude, thereby allowing complete control of the light-wave at any spatial location. The applied optics group at The University of Texas at Austin Electrical and Computer Engineering Department created a fully complex hologram by a combination of spatial light modulators. A digital micromirror device (DMD) was used to produce a precise amplitude profile, and a liquid crystal spatial light modulator (SLM) was used to produce the phase profile. A band-limited 4-f imaging system imaged the DMD onto the SLM to create a fully complex modulated wavefront, which reconstructed a holographic image at the desired location. With this capability, it is possible to create improved imaging methods for the consumer, medical, and defense industries as well as applications in holography. Our previous research has successfully created phase-only holograms (POH), amplitude-only beam-shaping patterns, and published simulation results on full-complex modulation. This thesis provides an in-depth experimental analysis of the full-complex hologram.Show more