Tag: particle physics
-
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…
-
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…
-
What are RG flows?
In this post, I will explain what Renormalization Group (RG) flow is. I will assume the knowledge of the basics of QFT for this post. The idea of an RG flow is intimately related to the idea of effective field theories (EFTs). An EFT is a theory that makes predictions upto some energy scale (called…
-
How to make the Standard Model?
This is a post to describe how we construct the standard model lagrangian and generate the masses for gauge bosons and fermions. I will assume basic familiarity with QFT, lagrangians, gauge transformations and gauge groups (like U(1), SU(2)). Recall that the mass term of a scalar field φ is simply proportional to φ2. Vector fields…
-
Why the (-+++) metric is objectively better than (+ – – -)?
This is a small post to argue that (-+++) metric is objectively better than the (+ – – -) metric. Before starting, let me mention that I studied QFT in the (+ – – -) metric (from Peskin and Schroeder) and I am still more used to (+ – – -) conventions for some calculations.…
-
What is supersymmetry?
This post summarizes the main ideas behind supersymmetry. Pre-requisites to read this post include some familiarity with Poincare algebra and basics of quantum field theory (especially the basics of fermions) In relativistic quantum field theory, we have a certain amount of spacetime symmetries. These symmetries include 3 rotational symmetries (along three space directions), 3 boost…
-
Some problems that I faced while studying Physics
This is a post in which I am just thinking out loud (writing your thoughts down is a great way to think out loud and organize your thoughts). The things that I write in this post may also be beneficial for some younger student of theoretical physics (which, if true, will be a bonus for…
-
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…
-
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…
-
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…
Hassaan Saleem 