Natural Science Forum / Physics / Particle Physics / December 2006

On Dec 7, 4:56 am, nayakmg....@gmail.com wrote:

Re your questions about isosping and hypercharge: What you are reading
about are two different interactions, the electromagnetic interaction
and the weak interaction. If a particle influences another particle via
a particular interaction, the strength of that interaction has to so
with some kind of charge associated with that interaction. An electron
has both an electrical charge (by which it interacts with other
electrically charged particle via the electromagnetic interaction) and
a weak hypercharge (by which it interacts with other hypercharged
particles via the weak interaction). What this means, for example, is
that an electron in an atom interacts with the proton in that atom by
not one interaction but at least two: electromagnetic and weak. As it
turns out, the weak interaction is much weaker than the electromagnetic
interaction -- hence the name.

Isospin is a property that is related to hypercharge and it expresses a
symmetry that the weak interaction has that the electromagnetic
interaction does not have -- this is one of the ways we can distinguish
the two interactions. Its name stems from the fact that that symmetry
is very similar to a symmetry seen elsewhere -- in quantum mechanical
angular momentum. However, there is no deeper physical connection other
than the name. This happens a lot in physics. For example, a third
interaction (the strong interaction) involves a charge that physicists
call color because of the symmetry of that interaction, but it has
nothing whatsoever to do with the color we see in light --- it's just a
suggestive name which is, as you can see, sometimes confusing to
beginners or hobbyists.

Re your question about physical nature of spherical harmonics: If a
physical law takes a certain mathematical form, then you can predict
that systems that obey that physical law will exhibit properties of
mathematical solutions of that mathematical equation. For example, if
any physical system whatsoever happens to be governed by a physical law
that takes the form of something that is recognized as the "wave
equation", then you can predict that the system will likely be found to
exhibit waves. (This is what ties together pendulums to sound to
chemical clock reactions to lasers and so on...) Likewise, the physical
law that governs the structure of atoms, for example, has a
mathematical form with spherical harmonics as mathematical solutions.
And sure enough, when we look at the physical states of atoms, they
look like spherical harmonics.

PD