c********s
发帖数: 123 | |
c*****t
发帖数: 1879 | 2 a negatively charged particle whose mass is about 1800th of that
proton :)
【在 c********s 的大作中提到】
: serious!
|
s**e
发帖数: 103 | 3
too what? it is a fundamental particle. besides mass and electical charge,
it also has weak isospin -1/2 and spin 1/2(which means it is a fermion). it
is the charged member of first lepton family. It takes part in electric and
weak interactions but neutral under strong interaction. ...
an abstract question what is electron does not make too much sense, all we can
say is a set of physical properties of an object.
【在 c********s 的大作中提到】
: serious!
|
s**e
发帖数: 103 | 4
there is no well defined size in the usual sense. it is treated as a point
particle in the quantum field theory |
m*****a
发帖数: 67 | 5
~~~~~~~you got
it. Actually the problem is it is treated as a point, always. That's
to say by now we don't know it's size. Only a upper limit.
【在 s**e 的大作中提到】
:
: there is no well defined size in the usual sense. it is treated as a point
: particle in the quantum field theory
|
c********s
发帖数: 123 | 6 so what is the best we can see?
or what is the best we understand?
Have we truly understood an electron yet? My knowledge stops at 1930.
【在 s**e 的大作中提到】
:
: there is no well defined size in the usual sense. it is treated as a point
: particle in the quantum field theory
|
l**n
发帖数: 67 | 7
If i remember correctly, there's arguement that rule out the
possibility
of an electron to be a black hole. Of course this does not
mean e has
a finite size, but just another piece of information.
【在 m*****a 的大作中提到】
:
: ~~~~~~~you got
: it. Actually the problem is it is treated as a point, always. That's
: to say by now we don't know it's size. Only a upper limit.
|
l**n
发帖数: 67 | 8 the mass of a particle is just a foudamental property which
is
independent of many other properties like spin and size.
in the standard model, the higgs particle is supposed to
bring
masses to gauge bosons by symmetry breaking and to fermions
by yukawa coupling(quite unsolid). But the numerical value
of
the fermion masses are free parameters in SM
【在 c********s 的大作中提到】
: so what is the best we can see?
: or what is the best we understand?
: Have we truly understood an electron yet? My knowledge stops at 1930.
|
s**e
发帖数: 103 | 9
in the thirties, we don't know weak interaction, don't know electron actually
took part in week interaction (depends on chirality or weak isospin). We don't
know there are three families of leptons, we don't know electron plus neutrino
consititute one of them.
Yes we measured the mass of electron, but we don't know even the mass of a
fundamental particle is not fundamental, it is a running parameter which
depends on the scale you perform your experiment.
【在 c********s 的大作中提到】
: so what is the best we can see?
: or what is the best we understand?
: Have we truly understood an electron yet? My knowledge stops at 1930.
|
s**e
发帖数: 103 | 10
It is not a wave in the usual sense. It has mass in the sense that you can
always find a frame in which it is at rest. We say it is a way in the sense
its distribution in space can be described by a wave function. Let's say wave
and mass just different properties of electron.
【在 c********s 的大作中提到】
: so what is the best we can see?
: or what is the best we understand?
: Have we truly understood an electron yet? My knowledge stops at 1930.
|
|
|
l**n
发帖数: 67 | 11 actually, the arguement is quite simple.
for a given particle of mass M, there is
always a compton wavelengh associated with
it, R_c = hbar/Mc. for an electron, we donot
know the radius of it, but we know its R_c
is about 100fm, which means that it's meaning-
less even to locate the position within this
distance.
for a given particle of mass M, we can relate
another length with it, the Schwarzschild
radius, R_s = 2GM/c^2. This is the critical
radius for a black hole(BH) of mass M.
in order to ma
【在 m*****a 的大作中提到】
:
: ~~~~~~~you got
: it. Actually the problem is it is treated as a point, always. That's
: to say by now we don't know it's size. Only a upper limit.
|
s**e
发帖数: 103 | 12
now there is speculation about the correspondance between the charged
blackhole and the tower of massive Kaluza -Klein states. But it's certainly
not the electron which should be massless at that scale. And it's only a
conjecture.
【在 l**n 的大作中提到】
: actually, the arguement is quite simple.
: for a given particle of mass M, there is
: always a compton wavelengh associated with
: it, R_c = hbar/Mc. for an electron, we donot
: know the radius of it, but we know its R_c
: is about 100fm, which means that it's meaning-
: less even to locate the position within this
: distance.
: for a given particle of mass M, we can relate
: another length with it, the Schwarzschild
|
e******n
发帖数: 9 | 13 It seems people here are all experimentalists. I agree you
can treat electron as a fundamental particle which has
properties like mass, charge, spin.
But what do you mean by a "fundamental particle"? Today the
accepted fundamental theory is QFT, which are theories about
fields. Particles are not building blocks of our world. And
mass, charge, etc. are simply some parameters in the theory.
You calculate some cross sections, etc from the theory and
compare with experiments to determine the value o |
s**e
发帖数: 103 | 14
It is a matter of taste of you calling it field or particle. Local
field theory means we are describing particles. If we have some extended
fundamental object like string, the field theory of it must be intrinsically
non-local.
Also, when people talking about mass, it is not bare mass, it is physical
mass depends on the scale you perform your experiment. Speaking of mass
does make sense although it is not a intinrsic quantum number as spin.
【在 e******n 的大作中提到】
: It seems people here are all experimentalists. I agree you
: can treat electron as a fundamental particle which has
: properties like mass, charge, spin.
: But what do you mean by a "fundamental particle"? Today the
: accepted fundamental theory is QFT, which are theories about
: fields. Particles are not building blocks of our world. And
: mass, charge, etc. are simply some parameters in the theory.
: You calculate some cross sections, etc from the theory and
: compare with experiments to determine the value o
|
e******n
发帖数: 9 | 15 【 : Also, when people talking about mass, it is not bare
mass, it is physical
Found a colleague. Yeah, I know people talk about physical
masses. Physical masses are dependent on experiment
conditions, so it's not a well-defined value as people
talked about. I just didn't point it out, thank you for
making this clear. |
