7 research outputs found
Probing space-time geometry using young diagrams
A thesis submitted to the University of the Witwatersrand, Faculty of Science in fulļ¬llment of the academic requirements of the degree of Doctoral of Philosophy.Quantum ļ¬eld theories and theories of gravity play an essential role in understanding nature. A dramatic recent development has been the discovery that quantum ļ¬eld theories are equivalent or dual to theories of quantum gravity on negatively curved spacetime. This duality goes under the name of the AdS/CFT correspondence. Sometimes the computation of certain observables in ļ¬eld theory are more diļ¬cult than the computation of the same observables in the theory of gravity and the opposite is also true. This makes the correspondence a powerful tool, that might provide an approach to strong coupling dynamics.
We explore the AdS/CFT correspondence between type IIB string theory on asymptotically AdS5ĆS5 backgrounds as our gravity theory and N = 4 super Yang-Mills as our conformal ļ¬eld theory. We study BPS operators with bare dimension of order N2 in the ļ¬eld theory and identify them with BPS geometries on the gravity side of the correspondence. The dynamics of 1/2 BPS geometries are identiļ¬ed with gauge invariant operators constructed using a single ļ¬eld in the ļ¬eld theory, while the dynamics of 1/4 BPS geometries are identiļ¬ed with gauge invariant operators constructed using two ļ¬elds. We ļ¬nd a sector of the two matrix model deļ¬ned by the SU(2) sector in the ļ¬eld theory, that can be reduced to eigenvalue dynamics. The BPS operators in this sector are associated to solutions on the gravity side of the correspondence. We also identify the gauge invariant operators with bare dimension of order N, constructed using three ļ¬elds, with 1/8 BPS giant graviton states. We count these gauge invariant operators constructed using three ļ¬elds in the ļ¬eld theory and show that the counting of these operators is in agreement with the number of giant graviton states. We also demonstrate a correspondence between correlation functions of the ļ¬eld theory and the overlaps of the giant graviton wave functions.
By working in terms of the eigenvalues we have managed to go from the matrix, which contains O(N2) degrees of freedom, to the eigenvalues which are O(N) degrees of freedom. Thus our work points to a signiļ¬cant simpliļ¬cation of the dynamics, something that deserves to be understood better. Another concrete result that we have achieved, is a proposal for some of the operators that are dual to the 1/4 BPS geometries. This is a genuine two matrix problem so it represents a novel extension of the understanding achieved by LLM of the 1/2 BPS geometries, constructed using a single matrix. The observables dual to new geometries have a bare dimension of O(N2). We have also considered operators with a bare dimension O(N), which are dual to 1/4 BPS giant gravitons. In this case too, we demonstrate that the eigenvalue description is useful.
Almost all of the studies of the large N limit of CFT have focused on the planar limit. Here, since the operator dimensions scale as we take N āā, we are considering large N but non-planar limits of the CFT. In these limits non-planar diagrams are not suppressed and the problem is considerably more diļ¬cult. The fact that we are able to explore this limit is concrete evidence for the power of the eigenvalue description and it suggests that a systematic treatment of large N but non-planar limits is possible.XL201
The simplest gauge-string duality
A dissertation submitted to the University of the Witwatersrand, Faculty of Science in
ful lment of the academic requirements of the degree of Master of Science.
Johannesburg, 2015.The gauge/gravity correspondence is a conjectured exact duality between quantum eld
theories and theories of quantum gravity. A very simple gauge/string duality, claims an
equivalence between the Gaussian matrix model and the topological A-model string theory
on P1. In this dissertation we study this duality, proposing concrete operators in the
matrix model that are dual to gravitational descendants of the puncture operator of the
topological string theory. We test our proposal by showing that a large number of matrix
model correlators are in complete agreement with correlators in the dual topological
string theory. Contact term interactions, as proposed by Gopakumar and Pius, play an
interesting and non-trivial role in the duality
From Gauss Graphs to Giants
We identify the operators in super Yang-Mills theory that
correspond to -BPS giant gravitons in AdSS. Our
evidence for the identification comes from (1) counting these operators and
showing agreement with independent counts of the number of giant graviton
states, and (2) by demonstrating a correspondence between correlation functions
of the super Yang-Mills operators and overlaps of the giant graviton wave
functions.Comment: 16 pages; v2: matches published versio
Topological String Correlators from Matrix Models
We discuss how to compute connected matrix model correlators for operators
related to the gravitational descendants of the puncture operator, for the
topological A model on P^1. The relevant correlators are determined by
recursion relations that follow from a systematic 1/N expansion of well chosen
Schwinger-Dyson equations. Our results provide further compelling evidence for
Gopakumar's proposed "simplest gauge string duality" between the Gaussian
matrix model and the topological A model on P^1.Comment: 25 pages; v2. refs adde