does anyone have any experience with theoretical physics vs philosophy of physics? What would be the main difference between the two disciplines (to say Msc or DPhil level? :)

Theoretical physics makes predictions :p

Philosophy of science is more about methodology and existence

Quantum mechanics is theoretical physics, quantum interpretation is more philosophy

The interpretation tells you what "really" happens

Basically parsing QM so that our thick monkey brain can understand it

ah i see! haha indeed

Is one or the other more highly recommended or employable at the end?

Well, the main one is Copenhagen

Mostly because it's the simplest one in the end

@AngusTheMan Uh, they are not alike at all. Philosophy of physics is either about epistemology, i.e. How/What can we know?, or about the ontology underlying physics, i.e. the "reality" causing the world to behave in the prescribed fashion (this requires an epistemological position that thinks such a reality exists)

Theoretical physics is about, well, conceiving of and solving theoretical models.

They will also talk about hours on end about time and space

Eternalism, presentism, block time

All that

Philosophy of physics isn't useless, either, it's a nice reflexion tool to come up with theories and it's also a nice pedagogical tool to learn about existing ones

But be careful to not confuse the theory with its interpretation

interesting, I have been thinking of switching my career pathway and wanted to get into something along these lines. But am going to start by doing another MSc rather than commit to the Dphil straight off ... do you know if a philosopher would be employable in a theoretical physics job?

The theory in the end should tell you what you can expect to measure

It doesn't say anything about if all the math objects you use in between are real

Not unless you also have a degree in physics, no

ah :/

@AngusTheMan No, a philosopher of physics is generally completely unfit to do a theoretician's job.

Which is one of the reason why few physicists take those philosophers seriously

@ACuriousMind Why would that be?

(of course that notion about a physical theory is itself a philosophical notion)

They discuss modern theoretical results without actually having the training to understand them.

I see

I suppose the prerequisite mathematics is non-standard for a philosopher?

Yeah it is a bit embarrassing when someone with no training in physics tries to pontificate about its deep philosophy

Not the math you need for physics, anyway

I suppose some philosophy degree will go into logic

@AngusTheMan Exactly. Philosophers rarely have any training in formal mathematics, except maybe basic formal logic.

What would be the difference between an applied mathematics phd or a theoretical physics one?

because I have read into a lot of courses here in the UK

and applied maths seems quite a lot like physics!

@AngusTheMan Well, that depends entirely on what you want to apply the mathematics to and what kind of theoretical physics you do

fair enough :)

The two can be anything from very similar to completely different

Rovelli does some decent science philosophy in his book

Physicists that go into philosophy tend to be a bit like

They want to tell the universe how it is

It's easy to get into "My theory is right because of philosophy"

hmm well I have a lot to think about! I have been looking at a philosophy of physics dphil at Oxford here in the UK, but I am really confused with what direction that would take me. On the other hand I have contacted a chap at Durham who is offering an applied maths taught Msc. Do you think it would be easier to go to theoretical phys (ultimate end point) from the maths or philosophy?

Math.

There's no getting around math to do physics

@Slereah Yeah, the old physicist stage of life is particularly bad with philosphy

I see.

Yeah

Philosophy of science is interesting but you have to keep in mind that they are things that cannot be proven, in the end

None of them are more valid than the others

Some of them just feel more reasonable

@AngusTheMan Definitely math. We don't need more theorists who don't know the math they're talking about :P

haha cheers for the advice guys!

C. Broad's book called philosophies that cannot be proven wrong but feels unreasonable silly theories

"By a silly theory I mean one which may be held at the time when one is talking or writing professionally, but which only an inmate of a lunatic asylum would think of carrying in daily life."

You see from outside the "know" we see all you guys as pretty much the same. So it is interesting that there is actually this wide disparage between the disciplines!

Well here is the secret of doing theoretical physics then

One third of the time is doing bibliography

One third is doing math

One third I slack a bit on the internet

Also when you do a math thing and you're not sure how to proceed, take a sheet of paper, write the beginning of the math until you get stuck, look at it very hard, take another sheet and start again

you see the life of a chemist is 50% lab, and 50% writing about said lab. ;)

unless your a material scientist then you can goof around on STMs and microscopes all day

Unless your me that is ... in which case your department gives you all the coding for softwares and programs to do, because chemists can't code :(

sorry I'll stop complaining now!

@Slereah Since when are you doing theoretical physics again? :P

I did it back when I was still a physics student :(

But those days are gone

I didn't include the "Translate things in French because my thesis advisor was a russian" part because I felt it was not universal

anyone mind solving $$(x^2-2x)y''+4(x-1)y'+2y=\mathrm{e}^{2x}$$

oh, looks like Wolfram decided to figure it out

@ACuriousMind thanks, I know you were already hard at work <3

@0celo7 You do realize that my first attempt would've been typing it into Wolfram? :D

That is the correct procedure

1) Wolfram Alpha

2) Mathematica

3) Eq. World

4) Actually do it by hand

5) Hawking Ellis theorem

@Slereah How many times have you succeded at 4) if 1)-3) failed?

Not quite sure

Not a lot

If 4) fails then it's time to look for papers and books

One thing I try to do sometimes is the opposite

I find a cool looking PDE and I try to make it fit to a physics problem

who wants to do $$\int\frac{4x^2-4x+2}{2x^2+1}\mathrm{d}x$$

anyone?

Well

@ACuriousMind ?

I can look up my book of integrals if you want?

btw how do you even do that

@0celo7 Looks like partial fractions.

what are the denominators

Or whatever that method is called in English

you can do decomposition of rational functions, no?

partial fractions is a thing

I forget how, though

yes, but what real rational functions make $2x^2+1$

@0celo7 Well, find the roots of the denominator

complex!

Well who cares if it's imaginary

Just do it and integrate it

If you do it properly the imaginary part should vanish

no

Wolfram has an easier method

jeez you ppl are complicated

no wonder you can't solve quantum things

Well why even ask if Wolfram can do it

lazy

You may as well ask us to show you naked ladies instead of asking google

@0celo7 Do polynomial division to get rid of hte $x^2$ term in the denominator, then find the integral of "linear function"/"quadratic function", which is a bit ugly, but can be done.

@ACuriousMind pretty much

Aren't the integrals of quadratic functions pretty much all hyperbolic functions

what

no?

Hm

I forget

I am old :(

@Slereah No, integrating constant/quadratic function gives an arctan, for example

Ah yes

$$2x-\log(2x^2+1)$$

took one line

I might have been thinking of $\frac{1}{\sqrt{1+x^2}}$

Or somesuch

yaaaaaaay I figured out how to do it

take THAT calc 1 prof!!!

calc 1?

@Slereah Ah yes, depending on the sign that gives normal trig or hyperbolic function

that's calc 2

@0celo7 idr the class name

calc 1 $\pm 1.00015$

Basically all integrals are a mix of logs, trigs and hyperbolics

and bessels and hermites and jacobis

also sometimes Bessel functions

and gammas and polynomials and legendres

some elliptic and more

Thermodynamics is kicking my butt but I got a 72/72 on my quantum midterm :D (avg 43)

Does anyone here have not positive opinions about the landau and lifshitz books?

too short

b/c I spent a few hours mixed up on definitions on their statistical physics book...

I've heard bad things about Landau

Basically that they try to cover too many topics and they are not always too specialized in them

Although I like their QM book, anyway

well, that integral was wrong anyway

@NeuroFuzzy Some things are discussed in L&L better than almost anywhere else. That said, I would not use those to first learn the subjects. I think it would be difficult to understand what really matters reading the books for the first time, also because they are in many ways outdates and more modern material gets to the point better (from a pedagogical view in particular).

oh for the sake of pete

$$\int\frac{\mathrm{d}x}{(2x^2+1)x}$$

I give up

this is too hard

now THAT looks like partial fractions

no, it's u sub

oh you're right

durn.

it's not right either ;_;

I'm so bad at math

oh no, it's totally partial fractions

yeah, it is

sigh

what the hell now

@0celo7 Do you want me to get

THE BOOK

AS can't help me

oooh, I don't have that book

jesus I've been stuck on simple calculus for half an hour

random logs now

wait a moment

nope, still wrong

I give up!

[redacted]

"Forms containing the quadratic trinomial $a+bx+cx^2$ and powers of x"

wait how did I screw that up so badly

nevermind

I'm going to do thermodynamics

fuck it, I'm gonna cheat

The integral of $\int\frac{dx}{x(a+bx+cx^2}$ is

this is ridiculous

$\frac{1}{2a} \ln(\frac{x^2}{a+bx + cx^2}) - \frac{b}{2a} \int \frac{dx}{a+bx+cx^2}$

dude

So in your case $\frac{1}{2} \ln(\frac{x^2}{1+ 2x^2})$

I think

ok this book has an error somewhere

$$\int\frac{\log(2x^2+1) dx}{x^2}$$

what the shit

how??

Integrate by part?

still gives the wrong answer :(

also you might wanna change the variable

y = x^2

Hm wait

Maybe not

dude that integral is worthless

the problem can't be solved, I'm convinced of this.

It's just a rational function dude

that integral is wrong!

it doesn't help solve the ODE

I think

The GDP

@0celo7 Less posting your wrong attempts to chat, more trying new things. You'll never learn how to come up with tricks and proofs yourself if you give up that easily :P

there aren't that many tricks to integrating

@ACuriousMind on my third page!

Integrating by part, change of variables, decompose the rational functions

I've been asked by people about every problem except for this one!!

And I can't figure it out!!

Also keep in mind logs and all the trigs and hyps?

dude the integral is not the issue

then what is

I can't figure out the right integral to use

Did you try using

The right one

holy balls I'm literally wrong all of these problems

what the hell

@ACuriousMind I've been working for the past hour, I have NO CLUE what I'm doing wrong

Ha, well, that happens. If you find no error after retracing all the steps, let it rest for a while and then start from scratch.

like I find one error

then there are more!

what is this!

That might be you either being paranoid and seeing errors where there are none, or you sucking at this :P

The worst errors you will ever do are sign errors and factors of 2 missing

those take forever to find

Factor of $\pi$ are also annoying

I do suck

thanks for finally saying it

FOUND THE ERROR

ON ONE OF THEM

turns out 8-2=6

never knew that

Does it

Maybe I should look up THE BOOK

YES THERE YOU ARE BEAUTIFUL FACTOR OF 3

Did you divide that 6 by 2

no I got a 12 after integrating a thing

then I divided by 4

wait a moment

am I stupid

this is the question we must all ask today

I...I did it

Can I get a Clay Prize for this achievement?

You can get some clay. That has to suffice

are you offering?

Here is your award

I deserve that.

I wish you people were meaner

Really?

The big error I had: turns out 2 times 1 isn't 4. I'm shocked and appalled by this turn of events.

related

But in my case both are going down.

@Slereah 0celo7 has zero years in grad school :P

well it's not gonna get better then!

@ACuriousMind Yes, passive aggressive meanness like that is what I need