Conservation of Bayron number, Lepton number and strangeness

Yael

Hi,

i'm stuck on my homework.. and this particle physics and cosmology chapter is killing me

a question asks me to discuss the following conservation laws: energy, linear momentum, angular momentum, electric charge (ok so far) AND bayron number, lepton number and strangeness.
are all of these laws based on fundamental properties of nature? Explain.

Now i do get the laws of conservation of bayron, lepton and strangeness...
but what do they mean exactly by fundamental properties?

Thanks.

Chi Meson

Fundamental properties of matter are those things that have no "why" beneath them. Mass is a property that matter has, so is charge. Turns out, as quantum was figured out, that there are more properties that just "are." "strangeness" is a property of matter. Its a strange property, hence its name. Don't worry about it now, it just "is."

Baryons and leptons are classifications for fundamental particles. There are many types of each, so "baryon-ness" is NOT a property. Energy and momentum are derived quantities.

1co1co1

Excuse me for responding so far, but I think this can be helpful for somebody who visit this page.I´m gonna talk about the baryon number. For example, in a neutron decay we can get a proton+electron+antineutrino; this transformation doesn´t violate the energy and charge conservation laws, and so we can set a question, why can't we obtain from this decay the combination electron+positron+one or more neutrinos and antineutrinos if that laws aren´t also broken?
The answer to this question was answered by Ernest Stückelberg (or something like that) that introduced heavy charges (now known as the bayron quantum number) who said that that number must be conservated as well in all the possible combinations of a decay and not into the forbidden ones, so neutron and proton are assumed to have the value of 1 for this number, electron, positron and neutrino are related to the 0 and the antiparticles to the additive inverse of the particle number.
So we get:
electron (0) +proton (1) + antineutrino (0)= 1 (neutron's bayron number), so this result is allowed.
electron (0) + positron (0) + neutrinos or antineutrinos (0)= 0 (the baryon number isn´t conserved and the result is forbidden)
I hope you find it useful. (For more information I reccomend see the book: facts and mysteries in elementary particle physics, written by Martinus Veltman)