Recent content by William Nelso

Yes but that just moves the charges around. The fact remains that there is a large free positive charge in the interstellar medium, which presumably must be balanced by an equal negative charge which is attached to various kinds of matter. Since the volume of interstellar space is far greater...

Indeed I am sure this is the reason. But regardless of reason, the fact is that positive charges are permeating space, while negative charges are not seen. Assuming that charge is overall neutral, where are the corresponding electric charges? That is my question. And it interested me primarily...

Ok, I made at least one error. The cosmic ray density 10^-3 m^-3 is intragalactic, not intergalactic. Most of the rays are trapped in galaxies. So I redo my estimate for a single galaxy, say the milky way, diameter 40 kpc and thickness 0.3 kpc. This volume is less than the previous cluster...

A simpler way to look at it is that the mass of a galaxy is about 10^45 g. If the charge is really around 10^64 (negative), as estimated above, then there would be charge of 10^19 per gram, or roughly one Coulomb per gram of mass. This is clearly ridiculous since the electrostatic forces would...

Well, let's estimate it. Cosmic ray density is believed to be basically one per 1000 cubic meters, almost all protons (I read this here: http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/cosmic.html) So charge density is 10^-3/m^3. The Laniakea galaxy supercluster that we are in is approximately...

Are you saying that no charge at all will be built up, or that it doesn't have to be large?

Cosmic rays are overwhelmingly positively charged. Hence, whatever is emitting them must be building up an enormous negative charge. So should we expect to see highly charged Reissner-Nordstrom black holes out there? Perhaps even near extremality?

I like the spectral-flow viewpoint on chiral anomalies, as described for instance in Peskin & Schroeder, last part of Ch. 19.1 This appears to depend crucially on the concept of fermi sea level, making it specific to fermions. However, bosonic self-dual tensor fields also have an anomaly...

I've run across a Lie group notation that I am unfamiliar with and having trouble googling (since google won't seem to search on * characters literally). Does anyone know the definition of the "star groups" notated e.g. SU*(N), SO*(N) ?? The paper I am reading states for example that SO(5,1)...

Ok, it may be slightly better now, but it still doesn't work. The videos just constantly buffer and are not watchable.

Here's the first day's worth http://ymsc.tsinghua.edu.cn:8090/strings/?page_id=706

Is it just me or are the videos at Strings 2016 unwatchable? They start and stop and continually seem to buffer, as if the bandwidth is not sufficient. The organizers did not respond to my email. I don't see a way to download and view offline, and I can't tell anything about the streams, e.g...

It's not really a well-defined question since the medium breaks lorentz invariance so that there is a-priori no simple way to compute what observers in different states of motion will see. The observers, and all of their measuring apparatus, are moving through the medium and they will be...

Length contraction is real. You can compute the length of a moving ruler using E&M and Quantum Mechanics, without ever using Relativity or the Lorentz Transformation. Relativity comes from the physics, not the other way around.

By "description" I mean of course a description in terms that you can define. One can define an electron, using mathematics, but good luck defining a god or demon. As for "explanation", that is not the role of science. That is the role of fairy tales.