Why Korean alphabet start with ㄱ? Tradition. The traditional Chinese phonology had a custom of arranging velar sounds (아음 - ㄱ, ㅋ; g and k in English) when classifying consonants. Hunminjeongeum (훈...

Tight-binding approximation in the second quantization formalism The second quantization gives a viewpoint that the particle (or wave) is a state, not a function. The characteristics of the second...

Tight-binding approximation in the first quantization formalism The tight-binding approximation is one of the methods that calculates the electronic structure of a crystal structure on the premise...

Jacobian Q. Jacobian은 무엇이며 왜 필요한가? Jacobian은 보존량이 좌표계에 무관하게 동일한 값을 주기 위해 필요하다. $q\rightarrow q’$로 좌표계를 변환할때 $q$ 좌표계에서의 체적/면적 등을 $q’$ 좌표계에서 미소 변위 $d\mathbf{s}(q’_i)/dq’_i$를 적절히 스케일함으로써 쉽게 구...

Why “random phase approximation”? This document is based on Xinguo Ren’s “Basics and Recent Progress of Random Phase Approximation for First-principles GroundState Energy Calculations” (p. 8) a...

Theorems in magnetism This note shows the summary of well-known theorems in magnetism. The proofs for these theorems are not discussed yet. Goldstone’s theorem. With the locality condition $|J...

Landauer formalism Consider a one-dimensional conductor with two sides: the source and the drain. The chemical potential of the source $\mu_{s}$ is higher than that of the drain $\mu_{d}$. The cur...

Quantum distance The Schrödinger equation that has a parametric dependence is given by: [\begin{equation} H(\mathbf{R})\ket{\Psi(\mathbf{R})} = E(\mathbf{R})\ket{\Psi(\mathbf{R})} \end{equation}]...

Check the worktree status git status --short --branch && git diff --stat && git log -1 --oneline Find committed files in the repository history In order to find the uploaded fil...

Google Play requires an active, publicly accessible URL that identifies the app/developer, contacts, collected data, sharing parties, security practices, and data retention/deletion policy. Here, I...