/sci/ - Science & Math

[Anonymous No.4409274]

What is the point of studying classical mechanics when we have quantum which describes everything better? Why can't 1st year physics be spent studying just maths to build up for quantum?

[Anonymous No.4409279]

No one wants to do all that math for macro scale stuff. Plus relativity.

[Anonymous No.4409281]

>>4409274

Classical mechanics describe the macro universe sufficiently well that it's not necessary to know the complex mathematics need for quantum mechanics.

[Anonymous No.4409299]

>>4409274

I can't work out if you're a first year physics student at a shit uni that actually has to teach that, or if you're 17-18 and studying this without really understanding any of it. Either way, sage.

[theta !vacuaB.oEw No.4409552]

<div class="math">\langle q_{F} | e^{-(i / \hbar)HT} | q_{1} \rangle = \int D q(t) e^{(i / \hbar) \int_{0}^{T} dt L( \dot{q}, q)}</div>
take <span class="math">\hbar \to 0[/spoiler], what do you get? stop being a pretentious undergrad.

[Anonymous No.4409641]

>>4409552

Specify your parameters?

[theta !vacuaB.oEw No.4409645]

>>4409641
parameters? what the hell are you talking about? if you can't figure out what that is, i feel pretty bad for you.

[Anonymous No.4409650]

>>4409645

>doesn't know what parameters are
>thinks he's more intelligent than OP and not a condescending prick with delusions of self-worth

[Anonymous No.4409664]

It doesn't describe anything better beyond what it's formulated for describing, namely quantum scale phenomena.

You don't build bridges and shit or calculate rocket trajectories with quantum theory, because it's terribly inefficient when there are better theories at describing higher level systems.

[theta !vacuaB.oEw No.4409666]

>>4409650
>doesn't know what parameters are
it's surprising that you don't even know what a classical limit is.

<span class="math">\int_{0}^{T} dt L(\dot{q}, q)[/spoiler] is known as the action.

<span class="math">L(\dot{q}, q)[/spoiler] is clearly <span class="math">\frac{1}{2} m \dot{q}^{2} - V(q)[/spoiler]

<span class="math">Dq[/spoiler] implies that q is a function of t.

has babby even attempted finding out what quantum mechanics is instead of complaining about not learning it first year?

[Anonymous No.4409672]

>>440966

No one said I didn't know what a classical limit was, I merely asked you to specify your parameters and you were unable. I understood the maths, I was looking for you to clarify it for OP. It's a shame you haven't learned what a parameter is yet, when you get through babby's first topology course come back and talk to me.

[Anonymous No.4409675]

>>4409672

Meant

>>4409666

[Anonymous No.4409706]

>>4409552

>Mfw I can't do that

[theta !vacuaB.oEw No.4409707]

>>4409672
>It's a shame you haven't learned what a parameter is yet
i'm fully aware what a parameter is in mathematical context. it's fairly intuitive to see what everything is in there if you've ever seen it before. most quantum texts have an entire section or two dedicated to classical limits, and i assumed that op looked ahead at the material given his remark about it being taught first year. i initially imagined you to be the op, so i apologize for that.

>It's a shame you haven't learned what a parameter is yet, when you get through babby's first topology course come back and talk to me.
i've taken topology. what relevance does this have with classical limit of the dirac formulation?

[Anonymous No.4409714]

>>4409672
Saying he is dumb for not being able to specify his parameters is like saying a mechanic is dumb for not being able to get your car pregnant. It's an irrelevant concept to the point he was trying to make, and the reason he couldn't answer it is because it is not answerable because there are no parameters that need specification. That path integral is a complete mathematical statement.

[theta !vacuaB.oEw No.4409727]

>>4409706
you should obtain
<div class="math">e^{(i / \hbar) \int_{0}^{T} dt~L(\dot{q_{m}, q_{m})}</div>
by doing an exponential integral. <span class="math">q_{m}[/spoiler] can be denoted as a classical path by solving <span class="math">(d/dt)(\delta L/ \delta \dot{q}) - (\delta L / \delta q) = 0[/spoiler] with boundary conditions.

it's a bit difficult, i admit. i was being pretty arrogant with the original post (i can see that now). i've done so unintentionally because it's pretty eccentric to state that you can dive straight into quantum mechanics without an appreciation/understanding of the classical world.

[theta !vacuaB.oEw No.4409735]

>>4409727
that should be
<div class="math">e^{(i / \hbar) \int_{0}^{T} dt~L(\dot{q_{m}}, q_{m})}</div>