@SpaceOtter ACM pointed out some of what I said about string theory could have been better phrased. if you're interested you might want to go back and check what he said.
First, relating string theory modes to ordinary particle modes is perfectly well understood: It can be shown that the tree-level string interactions always correspond exactly to the amplitudes of a quantum field theory. This QFT is called the "effective QFT" associated to a particular string model.
@SpaceOtter ACM knows a million times more than me about string theory and QFT so attend to what he says. Though I flatter myself I'm good at explaining things in a simple way. ACM's point is that sometimes my explanations simplify a bit too much and verge on the misleading side.
@SpaceOtter QFT is an awesomely successful theory. It's so successful that few doubt that it's basically the right way to describe fundamental physics.
However the formulations we have for QFT, i.e. the way we use maths to do the calculations, seem hideously complicated.
this has led to many, many years of physicists wondering if we are really going about QFT the right way.
What string theoy offers is a new insight into the way QFT really works.
A lot of us feel that if we really understood string theory then we would understand QFT far better and hopefully it would all get a lot simpler.
So lots of us believe that it's a fake distinction between string theory and QFT and that when we understand them well enough we'll understand that they are really the same thing.
@SpaceOtter : it's rather long-winded to explain that I'm afraid. I have to explain gravity, and how a magnet works and contrast the two. But to explain gravity I have to explain time then the speed of light. And to explain how a magnet works I have to explain the photon then pair production and the electron, then the Lorentz force. It isn't something I can tell you just like that.
it's a subset of the power set of $A\cup B$ (where $a\in A$ and $b\in B$)
@0celo7 $a$ is an element of a set (of which you don't a priori know the "internal structure": it may be just an element or another set), while $\{a\}$ is a set with one element $a$
@davidZ once you get a certain amount of flags, you get an automatic suspension don't you? Enough people flagged the picture for that to happen I think
For 30 minutes, yeah, but that's barely anything. Anyway, the point is that just because the picture was flagged once doesn't mean it will get flagged every time it gets posted. That's not how we work.
@DavidZ I'm reading a book called The Dumb House by John Burnside. It's won lot of awards, but it's written in the first person from the point of view of a psychopath and it's pretty unsettling.
It's weirdly fascinating to see into the worldview of a psychopath, but it's not a pretty view.
Robert L. Jaffe (born May 23, 1946)[1] is an American physicist and the Jane and Otto Morningstar Professor of Physics at the Massachusetts Institute of Technology (MIT). He was formerly director of the MIT Center for Theoretical Physics.
if he writes "garbagical" notes often then yup you are right
@Sanya I haven't read it yet, but I love John Baez's writing. His This week in mathematics blog was always a must read. I think he's very good at explaining things in an accessible way.
Case I:
Consider one atom having two electrons they have clockwise and anticlockwise spins.
Case II:
Consider two atoms they have single electrons ,these electrons having clockwise and anticlockwise spins
now my question is, which case can be considered as a entangled system.
@JohnRennie maybe because it is not nice to read too - even though I personally wouldn't downvote a quite reasonable question just because of that; enough worse stuff flying around after all
It seems a fair question. In a sense the two electrons in a helium atom are entangled i.e. you can't describe the total wavefunction as separable into two one electron wavefunctions.
@BalarkaSen Other danger of U besides radioactivity: compounds and salts of U and other tranuranic metals are particularly toxic. Thus you want to avoid any exposure to them possible. Perhaps wearing a hazmat and work in a glove box is a good idea
@DavidZ @dmckee I'm getting followed around the site, getting targeted downvotes and completely unrelated comments on my answers. Does this break any rule?
This seriously saps my motivation to answer anything at all.
@knzhou I just see a trickle of negative votes which probably won't trip any automatic system, and they seem to be coming on days when you are getting rep-capped anyway so they don't affect your total rep gain.
Though I recognize that they can be annoying. Been there. Done that.
Not enough hard exercises or illuminating notes. Seems to focus on the gritty details too much than leaving it to the reader. Doesn't tell me the big picture of things in general.
some questions/ dialog showing up in here on GR+QM one of the big/ open/ unsolved frontiers of physics. not sure of great/ best refs on this but these two turned up recently for me & cover history/ recent developments
Case I:
Consider one atom having two electrons they have clockwise and anticlockwise spins.
Case II:
Consider two atoms they have single electrons ,these electrons having clockwise and anticlockwise spins
now my question is, which case can be considered as a entangled system.
