Archives for October, 2026
write this out in expanded form
The repeated index \(\nu\) means sum over all four coordinates, while \(\mu\) labels which transformed coordinate we mean:\ Writing out all four equations:\ dx'^1 &= \frac{\partial x'^1}{\partial x^0}dx^0 +\frac{\partial x'^1}{\partial…
Scalar Lagrangian Full Expansion
For a real scalar field \(\phi(x)\), the standard interacting Lagrangian density is\ Using natural units, \(\hbar=c=1\), and the metric \(\eta_{\mu\nu}=\operatorname{diag}(+1,-1,-1,-1)\), let us expand each part. 1. Expand the spacetime derivatives…
It from Qubit paper by David Deutsch
It from Qubit: David Deutsch on Quantum Information and Reality David Deutsch’s “It from Qubit” (2002) argues that quantum information provides a powerful way to understand physical reality—but cannot, by…
Renormalization in QFT with a few examples
Renormalization is the process of relating the parameters in a quantum field theory to quantities we actually measure. It also explains why the effective strength of an interaction changes with…