Recent content by Steve Rogers

Hello, please check out the original paragraph. I said that we have to keep a little air in the bottle when we soak the bottle into the bucket.

Dear friend, It is tacitly assumed that the equation in my explanation is evaluated at the cut with ##P_\text{water}## denoting the water inside the bottle. I'm not sure what you meant by saying the pressure in water is not constant due to gravity, but when I talk about ##P_\text{water}##, I do...

I'd like to ask about an experiment on atmospheric pressure. To conduct the experiment, we need an empty PET bottle and make a small cut on the lower part of the bottle. A cut no greater than one-half the circumference is acceptable. Then, we press a table tennis ball against the cut to open the...

Hello, a quick reference for this topic can be found on arXiv, as follows. https://arxiv.org/abs/1510.02931 I guess the term "quasi-local mass" is more familiar to people working on mathematical relativity or mathematical physics, such as Shing-Tung Yau and Robert Geroch. Thank you for replying.

I'm self-studying the mathematical aspects of quasi-local mass, or quasi-local energy (e.g. Hawking energy), and a fundamental question has been lingering in my mind for a long time: why does quasi-local mass provide us with a measure of the gravitational energy? In general relativity...

Thank you. The chapter you mentioned does contain some information about vielbein, but to crack the problem, I need to find the variations of ##e_a^\mu## and ##\omega_a^{bc}##. This confuses me a lot because those ##\lambda##'s and partial derivatives in the formulas came out of nowhere.

I am taking a course on General Relativity. Recently, I was given the following homework assignment, which reads > Derive the following transformation rules for vielbein and spin connection: $$\delta e_a^\mu=(\lambda^\nu\partial_\nu e_a^\mu-e_a^\nu\partial_\nu\lambda^\mu)+\lambda_a^b e_b^\mu$$...

Thank you. Yeah, maybe you got a point, but I used the term "commercial" to distinguish the transformer in the clip from the one in physics textbooks. And I really want to know what role the silicon iron sheets play in a "commercial" setting. Do they make the transformer work better? If not, can...

Hi, everyone. I just finished studying the principle on which a transformer works. It relies on Faraday's law of induction. And my high school physics book uses the following picture for illustration: Roughly speaking, the...