Tag: #gravity
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Quintessence: The basic idea
Following the recent results announced by DESI, the interest in quintessence models may increase dramatically. So, this is a good time to write a small post on the basic ideas behind quintessence. Basics of GR and QFT are assumed for this post. Firstly, let’s review the basic idea of a cosmological constant. The Einstein equation…
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What are conformal field theories? (Part 1)
In this series of posts, I will explain what conformal field theories (CFTs) are. Basic familiarity with Quantum Field Theories (QFTs) is assumed. In usual relativistic QFTs have some spacetime symmetries. These symmetries are rotations (one about every space direction), boosts (one along every space direction) and translations (one along every spacetime direction). The set…
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How to derive the Schwarzchild metric?
In this post, we will go through the reasoning that gives us the Schwarzchild solution of Einstein field equations. Prerequisites for this post include familiarity with Einstein field equations. We start with the Einstein field equation (EFE) and convert it to a form that is used to solve this equation. This form is called the…
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First corrections to GR
In this small post, I will show why the first few possible corrections to the Einstein-Hilbert action are the way they are. Basic familiarity with General Relativity is assumed. I will use the natural units (units used in high energy physics) in this article. In these units, the unit of length is the inverse of…
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AdS3/CFT2 correspondence (Part 2: WZW models)
This is second of my series of posts on AdS3/CFT2 correspondence (for the first post, click here). In this post, I will describe what WZW (Wess-Zumino-Witten) models are. They are relevant here because a WZW model is used to decribe string theory on AdS3 . Basics of field theory, little familiarity with Lie groups and…
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AdS3/CFT2 correspondence (Part 1: AdS3 space)
This is first in a series of posts on duality between strings moving on AdS3 x S3 x T4 spacetime (don’t get intimidated by this) and a conformal field theory living on the boundary of the AdS3 spacetime (which is two dimensional). I will try to explain the basics required to understand this duality. In…
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Why string theory ‘may have’ extra dimensions?
This is a post that tries to answer the question, “How do we come to know that in string theory, there ‘can be’ extra dimensions in space?”. Some basic understanding of quantum field theory and general relativity is assumed as a prerequisite. Firstly, I want to point out why I have written ‘can be’ instead…
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How to derive Einstein’s field equation?
This post summarizes the reasoning that goes in deriving Einstein’s field equation. There are more than one ways to derive this field equation but I will focus on the most conventional path to derive it. Basic understanding of tensor analysis and special realtivity is assumed to understand this post. What we need is an equation…
Hassaan Saleem 