# Browsing by Subject "AdS/CFT"

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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 Holographic complexity : bulk tests and implications(2021-05-06) Eccles, Stefan Vincent; Fischler, Willy; Caceres, Elena; Kilic, Can; Paban, Sonia; Shapiro, PaulShow more This dissertation consists of four chapters. The first broadly and briefly orients the reader through an introduction to holographic complexity within the AdS/CFT correspondence. The next three chapters correspond to distinct lines of research conducted during my time as a graduate student, chosen for their thematic relation to holographic complexity, and particularly the two conjectures known as "complexity equals volume" (CV), and "complexity equals action" (CA). Chapter two is based on work conducted with Josiah Couch, Willy Fischler, and Ming-Lei Xiao, studying the holographic complexity of noncommutative field theories under the CA conjecture [1]. Chapter three is based on work with Josiah Couch, Phuc Nguyen, and Ted Jacobson, studying general aspects of the CV conjecture, and addressing certain challenges to that proposal [2]. Chapter four is based on work with Elena Caceres, Josiah Couch, and Willy Fischler, testing proposed extensions of both CA and CV that apply them to subsystem complexity [3].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 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