Tag: #research
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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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All three laws of motion matter
In this post, I will try to explain why all three laws of motion are independent and why the first and third laws of motion aren’t special cases of the second law. Newton’s first law of motion says that “An object continues its state of motion until an external force is applied on it”. However,…
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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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My 10 years in Physics
Today (20th October 2024) completes my 10 years as a university student (studying Physics). I took my first class as a Physics undergraduate on 20th October 2014 at the University of the Punjab, and in these 10 years, so much happened. There have been a lot of ups and downs that I have gone through…
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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…
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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…
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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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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.…
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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…
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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…
Hassaan Saleem 