Author Archives: Sung Lee

The Curvature, the Einstein Equations, and the Black hole II: The Curvature

In this lecture, we study different notions of curvatures of a Riemannian or a pseudo-Riemannian $n$-manifold $M$ with metric tensor $g_{ij}$. We will discuss only local expressions of curvatures as those are the ones we actually use for doing physics … Continue reading

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The Curvature, the Einstein Equations, and the Black Hole I: Riemannian and Pseudo-Riemannian Manifolds

This is the first part of the lecture note that is an extended version of the series of lectures I have given in the physics seminar at the University of Southern Mississippi. The majority of the audience were graduate students … Continue reading

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Twitter and Math

I opened a Twitter account back in March 2016 but had not been active at all without even a single tweeting until this May 2018 simply because I thought it would be just wasting my time. I was so wrong about … Continue reading

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E-mail Issue

I just noticed that I am not getting any e-mail notifications and I am sure neither are you. I ran diagnostics on my mail server and it is working fine without any problem. So I concluded that certain ports (like … Continue reading

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A Long-Lost NASA Spacecraft Comes Back Alive

A NASA spacecraft IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) was launched in March 2000 to study Earth’s magnetosphere where charged particles from solar winds trapped by Earth’s magnetic field. In December 2005, it suddenly stopped talking and since then it … Continue reading

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