Browsing by Subject "Witten-Sakai-Sugimoto"

This thesis reviews state-of-the-art top-down holographic methods used for modeling dense matter in neutron stars. This is done with the help of the Witten-Sakai-Sugimoto (WSS) model, which attempts to construct a holographic version of quantum chromodynamics (QCD) to mimic its features. As a starting chapter, string theory is reviewed in a quick fashion for the reader to understand some of the (historical) developments behind this construction. Bosonic and superstrings are reviewed along conformal field theory, and focus is put on Dp-branes and compactifications of spacetime. This chapter will also explain much of the jargon used in the thesis, which otherwise easily obstructs the main message. After a sufficient understanding of string theory has been achieved, we will move on to holography and holographic dualities in the next chapter, focusing on AdS/CFT and actual computations using holography. Matching of theories is discussed to set up a holographic dictionary. After this, we need to choose either a top-down or a bottom-up approach, from which we will use the former since we are going to use the WSS model. After this comes a brief review of QCD and its central features to be reproduced in holographic QCD. Immediately following this, we will review the Witten-Sakai-Sugimoto model, which is qualitatively and sometimes also quantitatively a reasonable holographic version of QCD. We will discuss WSS’s successes and room for improvement, especially in places that might affect the analysis that we are about to perform on neutron stars. Finally, after all this theoretical development, we will delve into the world of neutron stars. A quick review of the basic features and astrophysical constraints of neutron stars, along with difficulties in modeling them, is given. After this, we will discuss two models of neutron stars, the first one being a toy model with simplified physics and the other a more realistic one. The basic workflow that is required to get to the equation of state data and other relevant observables from a string theoretic action is given step-by-step, and many recent results using this model are reviewed. In the end, the future of the development of the holographic duality, constructing models with it, and modeling of neutron stars is discussed.