The h Bar

12:03 AM

@0celo7 it's completely ridiculous, and demonstrates a lack of understanding of mathematics.

1:34 AM

@Danu You are incorrect. It demonstrates a mind which values putting other down and making itself look authoritative more than it values conveying and receiving useful information. I've had some long discussions with CuriousOne in the past, and when he/she finally agrees to stop ranting and actually pay attention, there is a thoughtful brain on the other side. There's no completely lack of understanding of math, there's a complete lack of interest in discourse.

George Smyridis

Hey guys! Quick question. Is the intensity of the electrostatic field of a homogeneously electrically charged plate prerpendicular to it only when is has infinite dimensions? That's what i find.

However in every source i search they state that it is without stating first that the plate has infinite dimensions

0celo7

3:37 AM

@DanielSank QUANTUM GRAVITY vs QUANTUM FIELD THEORY IN CURVED SPACETIME

0

Q: Determine the constants for a black holes solution

I'm a new physics student. Currently I'm doing my first homework in black holes. Here's an introduction: Consider the following action: $$ I[g_{\mu \nu}, \phi, A_{\mu}] = \int d^4x \sqrt{-g} \left[ \dfrac{R-2\Lambda}{16\pi G} - \dfrac{1}{2} g^{\mu \nu}\partial_{\mu}\phi\partial_{\nu}\phi - \dfr...

> I'm a new physics student. Currently I'm doing my first homework in black holes. Here's an introduction:

I bet he's German.

Sidarth

@JohnDuffield please do....

user54412

5:09 AM

@GeorgeSmyridis yes

user54412

or at least the field some distance off the plate is only in that direction everywhere in the infinite case

user54412

the field is always perpendicular to the surface of a conductor at the surface itself, since any parallel component of the field will be effortlessly cancelled by charge rearrangement

user54412

@dmckee These days whenever I see a terrible question and I check the vote breakdown, it seems there's always a +1 mixed in with the -6 or so. I feel this has been going on for a while, yet I feel it wasn't always the case. I don't suppose there's any way for the system to handle someone whose method of trolling is upvoting trash?

0celo7

5:32 AM

@ChrisWhite I thought votes were anonymous

user116211

Wow! A nice tactic to post HW questions of physics and get answered by posting at Math SE instead of posting at Physics SE

user116211

0

Q: Static Friction

The coefficient of static friction between car’s tires and a level road is 0.80. If the car is to be stopped in a maximum time of 3.0 s, its maximum speed is (a) 2.4 m/s (b) 23.5 m/s (c) 7.8 m/s (d) 2.6 m/s Perhaps an easy question for some, but I simply do no...

mathematical-physics

user116211

How could they tolerate HW questions?

0celo7

@user36790 going to attempt the final boss ship in AC Rogue now

got my ship mostly leveled up

user116211

@0celo7 O.O

0celo7

5:45 AM

What

user116211

@0celo7 I've not played it ;/

user116211

Don't make me jealous ;P

Secret

6:23 AM

@DanielSank From my experience, It takes patience to comprehend CuriousOne. Often I will simply ignore all the emotional words in the paragraph and focus on understanding the facts presented, and then I ask for clarification on those facts to learn more ideas from the discussion topic at hand

Secret

The emotions emphasise the facts, but ultimately it is the facts that are worth discussing

DanielSank

6:44 AM

@Secret In my experience, roughly 80% of what he says is just wrong, another 19% is true but totally clouded in judgmental self-indulgence, and the remaining 1% is useful, un-corrupted communication.

Secret

ya, it takes effort to extract those 20%

Sidarth

7:05 AM

hello

curiousone huh?

Danu

8:37 AM

@DanielSank No, I insist that my assertion is correct in that, if this is the only quote you see, my conclusion is reasonable. Of course you've talked to him more and are therefore able to conclude different things about him, but that doesn't make my interpretation of the quote wrong per se.

DanielSank

9:08 AM

@Danu It is curious how enraging I find this comment.

I haven't felt like this since I took metaphysics in college.

Physics Meta

9:36 AM

0

Q: What is the reason that there are so many questions at this stack (physics) comparing to the others?

As far as I know on this physics stack are far more questions posted than other stacks. But why is that. I cann't imagine that a study of biology, chemistry or history etc. would comprise more detailled information or question. Is that because in physics is so much unclear comparing to other stud...

discussion questions

John Rennie

@DanielSank I can't comment on the role of infinity in maths, but I was under the impression most physicists don't believe there are any infinite quantities in physics - with the possible exception of the size of the universe.

Danu

@DanielSank Hmm?

my comment, that enraging?

@DanielSank plis

@JohnRennie I wonder about the total energy of the universe sometimes

Slereah

@Danu It is 13 Joules

Danu

Of course with nonzero $\Lambda$ this would be a corollary

innisfree

9:56 AM

What do you mean no infinite quantities? I can reparameterize a finite quantity to a infinite one. E.g. neutrino has infinite 1/charge

Slereah

1/0 is not defined

Danu

@innisfree The point is that one cannot measure infinite things

No meter can read "infinity"

innisfree

Ah, well, suppose you take a ruler, which obviously stops at a finite point

I can make a reparameterisation of the scale on the ruler x \to f(x) that blows up somewhere

Hari Prasad

1+2+3+4+5+6+............ = -1/12

Danu

@innisfree But you can never make any meter read "infinity"

Reparametrizations are just math, not readings from a meter

The point is that physics cannot distinguish arbitrarily big from infinity

innisfree

10:04 AM

Why? I'll put my reparameterized scale on the ruler

One of the markings on my ruler would read infinity

Danu

Like I said, you will not be able to distinguish it from arbitrarily large but finite

I think this should be obvious

Hari Prasad

"Infinity is just an illusion"

Danu

^stop posting random things please :P

Hari Prasad

ok :P

innisfree

Would you say the same about eg 11cm? One can never distinguish close to 11 cm from 11 cm, therefore you cannot measure 11 cm on a ruler?

Danu

10:08 AM

@innisfree Lol, I'm saying you can never measure anything arbitrarily precisely

So you will never be able to read exactly 11cm, indeed.

The point is, now, that $\infty$ is exact

It's obvious we can get arbitrarily large but finite things

but you can never claim it's infinite

innisfree

Yes, I agree, the infinity marking on my ruler would have zero probability of a measurement (but finite density)

Secret

Below is a weird question of mine which is incomplete because I don't know how to break open tensor product expressions:

Suppose there's an entangled state is denoted by
$$\lvert \Psi\rangle_{AB}=\sum_{i,j}c_{ij}\left(\lvert i\rangle_{A} \otimes \lvert j\rangle_{B}\right)$$
for some orthonormal basis $\lvert i\rangle \in \mathcal{H}_A$ and $\lvert j\rangle \in \mathcal{H}_B$ and $\exists c_{ij}\neq c_ic_j$ (NB $\langle i\lvert j\rangle\neq\delta_{ij}$ in general)

Since states in this framework are geometrically vectors in hilbert space, is the entangled state geometrically a 2nd order tensor?

If it is a tensor, can it also behave like a multilinear map such that e.g. given some states $\lvert \phi\rangle=\s…

Danu

@innisfree No, this is completely independent of probability

I also don't know what you mean by finite density

innisfree

Finite probability density

So I cannot measure 11cm. Are there any numbers I can measure on a ruler?

Hari Prasad

@Danu Can i know what is the geometrical shape used as your profile pic?

Secret

10:14 AM

danu's pics seemed to be depicting hopf fibration of some sort

Hari Prasad

@Secret yes it seems so

innisfree

Anyway, I agree my parameterization ofa ruler would fail because the infinity point would have zero measure. But if I took something discrete eg the 1/number of cars that pass my window in an hour, I can measure infinity

Hari Prasad

@Secret Hopf fibration or Hopf map is the first example discovered of a map from a higher-dimensional sphere to a lower-dimensional sphere which is not null-homotopic. Its discovery was a shock to the mathematical community, since it was believed at the time that all such maps were null-homotopic, by analogy with homology groups.

Danu

@innisfree Give me a meter that tells me "infinity" for that measurement, then

You seem to be missing the essential point that you can only get infinity in some limiting procedure

$1/0$ by itself is not defined

You can speak of $\lim_{x\searrow 0}1/x$, but you're not going to get that from a discrete measurement

John Rennie

innisfree is being provocative rather than pragmatic, but nevertheless raises an interesting point that if there are no finities then there are no zeros either.

We might say resistance can never be infinite and I doubt many physicists would find this controversial.

Danu

10:26 AM

@JohnRennie No, that's wrong as per my above explanation IMO

John Rennie

The converse would be to say that conductance can never be infinite, and that's probably not controversial either.

Danu

Infinity can only be defined in some sort of limiting procedure

John Rennie

Actually forget that - I forgot about superconductivity ;-)

Danu

We already agreed on the continuous case not giving exactly $0$ or $\infty$ and I just argued that the discrete case cannot support any infinities because there is no limiting procedure

This breaks the symmetry between $0$ and $\infty$ and makes it possible for us to consistently measure zero cars going by our window, yet never measuring $\infty$-anything.

John Rennie

I might have had a whisky too many last night, and my concentration isn't all it might be this morning :-)

Danu

10:29 AM

@JohnRennie Do you find my argument convincing, or not?

By the way, you never answered: What's your favorite whisky?

innisfree

What values can I measure with a ruler? Why not te infinity mark on my customized ruler?

John Rennie

I don't really have a favourite.

My brother used to work in the wine trade and still has loads of contacts there

Danu

@JohnRennie Do you know a lot of different ones, or are you kind of indifferent :P

Hari Prasad

@innisfree where will you mark the infinity? At infinity? : P

John Rennie

He gives me bottles of single malts that I've never heard of

Danu

10:30 AM

@innisfree As I said, you cannot measure it exactly. On your ruler you have continuous scales and we agreed you cannot distinguish $\infty$ from arbitrarily large numbers there.

John Rennie

Some of them are really fantastic, while others are, shall we say, an acquired taste.

Danu

@JohnRennie I collect whisky, so I'm interested to hear any names

innisfree

So I can't measure any number with a ruler?

ACuriousMind

@Danu You cannot distinguish 0 from arbitarily small values, or 2435625 from values arbitrarily close to 2435625 either. That's not an argument

John Rennie

I can't remember any at the moment, but then I'm struggling to remember my own name at the moment :-)

Secret

10:31 AM

Suppose you have a ruler where you define infinity as a marking on it, then you will now run into trouble on measuring zero with this ruler, because there is no telling how far out on the ruler you have to mark in order to makr the point zero

Danu

@ACuriousMind It is; A claim that you can measure exactly $\infty$ is the same as claiming you can measure exactly $2$ on a continuous scale, which I think is wrong (also @innisfree)

I already laid out how to resolve the apparent contradiction in the discrete case

Hari Prasad

@Danu Does whisky contain alcohol?

Danu

@HariPrasad lol

John Rennie

last night was a bit of a mixture. Some friends dropped by and we chattered long into the night. I have a bottle of Ukranian brandy that looks a lot emptier than it was yesterday.

Danu

@JohnRennie :(

@JohnRennie Ukranian? :P wow

innisfree

10:33 AM

@danu, once more, what numbers can I measure on a ruler?

Danu

@innisfree Sorry ,I was typing a response when ACM barged in. You cannot measure exact numbers on a ruler.

Hari Prasad

@innisfree common just leave it. Change topic!

Danu

You can determine things up to small intervals

Btw related notions are nicely encapsulated in the axioms of topology

Let me find the relevant math.se thread

John Rennie

@Danu How do I post pictures here? I'll show you the label.

ACuriousMind

@Danu It's an MO thread you're thinking of.

Danu

10:35 AM

@JohnRennie On the right, bottom, there is "upload..." next to "send"

John Rennie

Tastes like paint stripper :-)

innisfree

I somewhat agree. If we consider a measurement as a continuous random variable, centered hopefully at the true lenth of something, my infinity marking would have zero probability, just like any other exact measurement (but finite probability density)

Hari Prasad

@JohnRennie which language is that?

and what does it say

John Rennie

Ukranian I suppose ...

It says "Don't drink this it will give you brain damage"

Danu

@ACuriousMind Heh...

You knew it too?

ACuriousMind

10:39 AM

Yes, and I think KevinBuzzard's objection to the ruler post is completely valid.

Hari Prasad

@JohnRennie lol.

John Rennie

Incidentally, I note my bitchy comment about JT and JD now has nine stars.

Danu

@ACuriousMind and I think this counterpoint is also good

@Kevin: I think the point is that we should think about the rulers as open sets, because the property of belonging to an open set is more 'stable' than the property belonging to a closed set. For example, it is better to have a (95cm, 105cm) ruler rather than a [95cm, 105cm] ruler because if someone is exactly 95cm tall, then the [95cm, 105cm] ruler will answer yes, which is undesirable because she is actually on the boundary. On the other hand, if the (95cm, 105cm) ruler says yes, then we are more sure of the answer because our set is disjoint from its boundary (open). — Tony Huynh Mar 25 '10 at 18:14

John Rennie

The last time that happened the moderators deleted the comment :-)

innisfree

@JohnRennie how old is it?

John Rennie

10:42 AM

@innisfree The brandy?

innisfree

Yes

Danu

But I agree that it's not a perfect argument (and it's also not really relevant for what we're discussing now---I just thought it was interesting as a side remark)

John Rennie

@innisfree I don't know - I can't read Ukranian. It was a present from a Ukranian lady I met a few years back. It's actually pretty awful but I keep it for sentimental reasons.

Though it's nearly all gone now.

innisfree

You know, I heard all ersatz Soviet alcoholic spirits were just basically paint stripper plus colourings

John Rennie

I doubt it - drinking paint stripper will kill you

innisfree

10:46 AM

Well not literally :)

John Rennie

Anyway, do we agree that there are no infinities in physics or not?

Danu

@JohnRennie I have yet to see anyone react substantially to my arguments.

I think everybody at least agrees about the continuous case.

(but the countable case seems clearer to me, so hopefully everybody agrees there, too!)

ACuriousMind

@Danu I don't think you have countered innisfree's reparametrization argument. Why not mark 1/x instead of x on a ruler, and measure infinity with ease?

Danu

@ACuriousMind What?

Please reread the thread

Hari Prasad

@JohnRennie where do we encounter infinity in physics as an answer?

Danu

10:50 AM

Innisfree even agreed ("somewhat")

John Rennie

I suppose I believe, without proof, that a submanifold of our universe with constant comoving time is unbounded. Is that infinite?

Danu

You can always achieve $|x|>M$ for any fixed, finite $M>0$ but nothing more than that

@JohnRennie Sure---but it's not a measurement :P

John Rennie

@HariPrasad there are lots of examples where our mathematical models predict singularities - the question is whether these are just an artefact of the model or whether they are real.

@Danu why do I need to measure infinity for it to exist?

Danu

@JohnRennie Because you shouldn't be making any ontological claims in physics.

You should know that!

"why do I need to measure [the position of a particle] for it to [be somewhere]?"

ACuriousMind

@Danu I don't see where it was resolved, really. Or have we decided that "we can never measure anything exactly" counts as a resolution?

Danu

10:54 AM

@ACuriousMind Of course it does. Combined with the fact that $\infty$ is exact

Secret

ACuriousMind

@Danu 0 is exact too. So you say the resolution is that we never actually measure numbers? 2 doesn't exist?

Danu

@ACuriousMind Ugh, come on dude, read the whole discussion. It's of vital importance to distinguish the continuous and discrete cases. You're attacking strawmen.

Hari Prasad

@Secret Kaspersky?

ACuriousMind

@Danu Then take $\pi$ - does it not exist because you can't measure it exactly?

John Rennie

10:55 AM

It seems to me, in a rather vague and ill thought out way, that an infinite density is a different kind of infinity to an infinite universe.

Danu

@ACuriousMind I argue that we can never exactly measure $\pi$ and therefore it is completely out of place in physics to claim existence in the ontological sense. Of course it can be exactly defined in mathematics.

Hari Prasad

@JohnRennie yes there are different flavours of infinity

John Rennie

While I'm happy to believe the universe may be infinite I don't believe an infinite density can exist.

ACuriousMind

@Danu What does "existence in the ontological sense" even mean for a continuous number?

John Rennie

@HariPrasad I wasn't thinking of the Aleph numbers

Danu

10:57 AM

@ACuriousMind What you want to denote by "exist". Can you define "exist"?

If it means* [<-- correction] "possible to measure exactly" then I think you're wrong to claim $\pi$ exists. If it means something else then I believe you'll have an awful time trying to make it precise.

Secret

@Acuriousmind above workings showed the context of that question with the special case of a 2 level system, not sure if I evaluated the entangled state properly

But the workings seemed to suggest if I have a state in subsystem B interacting with the entangled state, then I end up with a state entirely in subsystem A

However the converse seemed to not hold if I start with a state in subsystem A then allowed to interact with the entangled system, because $\langle i|_A j\rangle_B \neq \delta_{ij}$ in general

Hari Prasad

@Danu why don't we still know why these fundemental physical constants exist in nature?

Secret

@HariPrasad the notepad is from a gift along with the software

ACuriousMind

@Danu I'd say numbers/abstractions don't have existence at all. Infinity exists exactly as much as 0, or 3, or pi.

Danu

@HariPrasad Ehh... What? Your sentence is unclear to me.

Hari Prasad

11:00 AM

@Danu like pi, fine struct const, plank const etc .........

innisfree

@ACuriousMind the resolution is that a measurement of a continuous quantity is something like sampling from a PDF. My mark at infinity would have probability zero (but finitie probability density). Other finite intervals would have finite probabilities.

Danu

@ACuriousMind So you claim we can never see 3 cars pass just as much as we cannot see $\infty$ of them? I find that absurd.

@HariPrasad What about them?

@ACuriousMind This is, again, where the continuous vs. discrete situation is important, and it seems you neglect that.

ACuriousMind

@Danu No. But "3 cars" is different from the number 3. 3 is a concept, not an entity that has ontology. (I realize that sounds somewhat platonist)

innisfree

The discrete case is easy. If I measure 1/n in a counting experiment, 0 counts and thus infinity is a possibility

ACuriousMind

@Danu No, I think you're neglecting my willingess to doubt the existence of discrete numbers ;)

John Rennie

11:03 AM

And to think that this all started when we criticised CuriousOne for saying infinity existed only to give mathematicians something to argue about.

Danu

@ACuriousMind Okay, that's fine. We'll fundamentally disagree on that. I cannot agree with you because it is obvious in my mind that at the very least natural numbers have a meaning outside of mathematics.

Hari Prasad

@Danu what i am saying is , why the ratio of circumference of a circle to its diameter is always equal to pi even if the circle is as large as the whole observable universe or a circle of radius equal to a plank length.

Danu

@JohnRennie I think it's an interesting discussion---more so than 95% of what happens in the chat these days.

@HariPrasad You're not making any sense.

The proportionality constant $\pi$ is purely mathematical abstraction.

There is no way to exactly determine anything measuring $\pi$

ACuriousMind

@innisfree Okay, that distinguishes infinity from the rest of the continuous numbers, I agree.

Danu

@ACuriousMind It's actually nice that you mentioned this because it much clarifies the reasons why I'm arguing what I'm arguing

innisfree

11:06 AM

@JohnRennie I didn't mean that alcoholic spirits were literally paint stripper! Just that they only superficially resembled the genunie items as cheaply as possible

Danu

I've always considered natural numbers as "physically meaningful"---I'm not sure about extensions or where to cut that off but I know that $\Bbb N$ is meaningful.

John Rennie

@innisfree yes, I think you've described Ukranian brandy fairly well :-)

ACuriousMind

@Danu "Have a meaning" is not the same as "existing". We humans tend to tell many stories about the world that imbue it with meaning - that doesn't make the relations and ideas in those stories existent.

Danu

@ACuriousMind I give meaning in the sense of 3 cars passing by my window.

Counting is enough to establish reality (in the sense of admitting precise measurement---e.g. the cars example) of natural numbers to me.

ACuriousMind

Yes, so you use "3" to describe the world. "3 objects" is something that can exist. "3" alone is not, to me.

Danu

11:08 AM

@ACuriousMind Okay. Semantics ;)

Now let's move on to the more interesting question: Do $\pi$ units of length exist?

And also, you still have to define "exist" for me, or I will stick to my choice of definition

innisfree

Like infinity, pi has got zero probability in a pdf.

Cannot be measured or even marked on a ruler

Danu

Exactly, and it cannot be measured in a discrete sense either---hence it cannot be ascribed physical "reality" in the sense of the natural numbers.

Secret

Infinity existience

Danu

I feel like @innisfree agrees with me. What do you think about the existence of natural numbers, @innisfree?

ACuriousMind

@Danu An object exists when I can test its existence - the world would be different when it would not exist, and I can detect that that difference is not the case.

Danu

11:11 AM

@Secret We've finally got something interesting in this chat room.

@ACuriousMind So the notion of "$n$ objects" exists, right?

ACuriousMind

Or, more positively, I derive a prediction from assuming its existence and can test that that is the case. I'm not big on choosing falsification over verification here.

@Danu Yes

Danu

So @ACM actually the only point we haven't settled on is this: Does something like "$\pi$ (or other only continuously-definable) units of something" exist?

innisfree

Pi could be the asymptotic outcome of a Monte-Carlo experiment - you know you can measure pi by scattering and counting sticks?

So I say pi cannot be measured in a finite number of experiments

Danu

@ACuriousMind We agree on everything else already, as far as I can tell. You just insist on the (to me pedantic) semantics of distinguishing $n$ and $n$ objects

innisfree

en.m.wikipedia.org/wiki/Buffon%27s_needle

Danu

11:14 AM

Your definition, too, marks out at least the natural numbers from e.g. $\pi$, so I think there is only one answer to my above question

ACuriousMind

@Danu No, I think it follows directly from the reasoning about infinity that you only get $(\pi-\epsilon,\pi+\epsilon)$ lengths.

Danu

@ACuriousMind Exactly.

So we agree on everything.

Cheers all around

innisfree

I didn't agree to that

jk

ACuriousMind

@Danu It's not semantics to me. I really feel that an abstract concept is different from its instantiation. Abstractions are things that cannot exist, they are just...patterns that may or may not match something real

Danu

@innisfree Okay, so where do you disagree with anything? :P

@ACuriousMind Okay. You're entitled to that opinion, but I think that (again, I'll stick to the natural numbers because I haven't thought much about other cases) it's needlessly pedantic.

innisfree

11:17 AM

Anyone read any good popular science/math books/biographies lately?

ACuriousMind

@Danu If I contradict that again, I'll be guilty of being pedantic about whether I'm being pedantic, right? ;)

Danu

@innisfree I don't read any "popular" stuff but I read biographies---the ones on Einstein & Bohr by Pais are great.

@ACuriousMind Please, indulge yourself!

John Rennie

@innisfree Mark Ronan - Symmetry and the Monster

innisfree

Cool I'll give them a go, thanks

John Rennie

It's about the classification of the finite groups. I found it fascinating without being too hard work.

Danu

11:20 AM

Mehra's book on Feynman is super in-depth and therefore interesting, but his writing style is bad.

It's very nice in terms of really digging deep into his theories of e.g. time-symmetric electrodynamics.

innisfree

@JohnRennie only £2.48 on Kindle, great

John Rennie

@Danu Assuming you mean "Subtle is the Lord" I found the first half fascinating but it dragged a bit towards the end.

Danu

@JohnRennie Yes, I did mean that book.

They're long, serious reads. Not very "entertaining" but you learn a lot.

John Rennie

Pais wrote a book of brief biographies of physicists that was interesting, though i forget the name.

Danu

I've sadly not found time to read any non-textbooks for the past 2 years :\

The last I read was "A Life of Erwin Schroedinger" by Moore, which was decent but not amazing.

John Rennie

11:24 AM

Aha, it's "The Geniius of Science":

amazon.co.uk/Genius-Science-Portrait-Gallery-Physicists/dp/…

innisfree

@JohnRennie not on Kindle bah

John Rennie

Also there's a book by John Derbyshire on the Riemann Hypothesis that is my favourite popular math book ever.

Danu

I also read a biography of Dirac but thought it was too life-oriented instead of science-oriented.

It had a priceless anecdote about a parrot though :3

ACuriousMind

@Danu Think about it like a programmer: Things have types and values. A type specifies the admissible values for a thing. The natural numbers are a type, and 0 and 1 and 2 and so on are values. But they are not things. The variable "number of cars" is a thing, and "number of cars is 3" makes an existence claim. But for an existence claim to make sense, at least one of the two things must be a thing, not a value, since "3 is 3" or "pi is 3" are tautologically true/false.

John Rennie

I think it's:

amazon.co.uk/…

innisfree

11:27 AM

My favourite is Simon Singh's Fermat's Last Theorem. It made a big impression on me when I was 15 or so

ACuriousMind

::waits for programmer to assult me over not understanding types::

Danu

@innisfree But would it still be interesting to someone who actually is interested in the technical background?

@ACuriousMind I don't think like a programmer, sorry. But I see what you're saying.

John Rennie

@innisfree Ah yes, I enjoyed that too. Did you see the BBC Horizon programme on Wiles' proof?

Singh wrote another book "The Simpsons and Their Mathematical Secrets" though that's more fun than deep

Do you want a listing of my pop science (e-book) collection? 180 or so books.

Hari Prasad

@JohnRennie I solved Riemann Hypothesis a few years ago but then dumped the solution since it was a Millennium Prize problem. Also i will reject Field's medal

John Rennie

Fields medal not Field's medal

Secret

11:31 AM

@Acuriousmind @DanielSank @yuggib
http://chat.stackexchange.com/transcript/message/28036004#28036004
http://chat.stackexchange.com/transcript/message/28036031#28036031

innisfree

@john I think the best 5 or so will keep me going

John Rennie

"Guilia Enders - Gut" is highly entertaining but not really scientific.

Danu

@Secret Dude, stop spamming people with your stuff :P

Hari Prasad

@JohnRennie yah sorry. But i don't care. I hate mathematics after all. I'am trying to come up with a different tool other than 'mathematics' to describe physics, since mathematics is not perfect for the real world

Danu

^lolwut.

Let me tell you: You're going to have a bad time

ACuriousMind

11:33 AM

@Danu You will regret your mode of thinking the day we realize we live in the Matrix ;)

Danu

@ACuriousMind I'm taking the... blue (?) pill

I have no moralistic objections against choosing a nice life

Secret

@Danu I am asking a question, not showing random stuff (otherwise they will nto be tagged)

Hari Prasad

@Danu i took both pills at the same time.

ACuriousMind

@Danu Then the blue one is indeed the correct choice

innisfree

Anyone gonna watch Arsenal-Spurs?

ACuriousMind

11:35 AM

What's that?

John Rennie

Football

ACuriousMind

Ohhhh

Hari Prasad

guys whats the current time in your respective places? mine is 5:06 pm

Danu

12:38 PM

Hari Prasad

@Danu GMT?

ACuriousMind

11:38 AM

@Danu :O You're one minute ahead of me

John Rennie

Actually I've changed my mind about my favourite popular maths book because i've just remebered "The Shape of Inner Space", which I thought was absolutely fantastic.

Danu

@JohnRennie You did? I wasn't sure whether to read it or not.

John Rennie

amazon.co.uk/Shape-Inner-Space-Universes-Dimensions-ebook/dp/…

Hari Prasad

@JohnRennie Is string theory really fancy stuff?

Mr. Y

Hello guys ,I would like to ask you a surely banal question but really important for me:does the study of physics start from scratch at university (of course with a more detailed method + calculus etc.. ) ?Is it best to have a solid base in mathematics rather than physics ?

John Rennie

11:39 AM

@Danu it's a popular maths book, so of little use to anyone serious about the subject, but fascinating reading for the non-non-nerd.

Hari Prasad

@Mr.Y Its good to have a solid base in mathematics and physics as well.

John Rennie

@Mr.Y there's obviously a subtext here. Can you give us some idea why you are asking? Otherwise all we can say is that it depends on the university.

Another entertaining book, for rather different reasons, is "Florence Williams - Breasts, A Natural & Unnatural History"

Mr. Y

Surely.I am on a gap year and in 4 month I will have to take a text for physics and math at uni .Surfing on the internet I've read that it's better to have a solid base in mathematics rather than physics since at uni you will start again from scratch and then you will learn the physics along the way.I don't know if this is true or just blind talk about the real truth.

John Rennie

On that note perhaps I will stop rummaging through my book collection.

ACuriousMind

@JohnRennie lol

John Rennie

11:44 AM

@ACuriousMind Despite the title it is a serious book. Sadly without colour photos :-)

amazon.co.uk/Breasts-Natural-Unnatural-Florence-Williams-ebook/…

Available in Kindle format @innisfree

ACuriousMind

@Mr.Y A good course should start "from scratch" in both physics and mathematics, but most will do so in a pace that assumes you actually already know the material and just need a refresher. Without looking at your specific courses and your specific university, it's pretty impossible to say which you should be focusing more on

Hari Prasad

@JohnRennie is that essential for a university physics student?

innisfree

@JohnRennie lol

ACuriousMind

@HariPrasad Most students will prefer to have more...hands-on experience with the subject

3

John Rennie

@innisfree Re the Kindle - I started on a Kindle but now use a tablet (Nexus 7) as I found the Kindle too slow and the screen too small.

Hari Prasad

11:49 AM

@ACuriousMind What do you mean by Hands on experience?

ACuriousMind

I'm not explaining that joke

Hari Prasad

@ACuriousMind alright

innisfree

@JohnRennie no way! I prefer the e-ink screen. And besides, with a fully fledged tablet in my hands, my concentration is decimated!

Mr. Y

Thanks for the advices.Cya all :)

John Rennie

If Amazon did a Kindle with an 8 inch screen I would be tempted, but the 6 inch screen is just too small for me.

Re the tablet: the secret is to leave the wi-fi off :-)

innisfree

11:53 AM

Easier said than done

John Rennie

I almost exclusively read on the tablet now. I only use paper for science books, largely because I need to keep flicking backwards and forwards in a vain attempt to understand them.

Hari Prasad

12:07 PM

what are some of the most underrated physics theories

user116211

@HariPrasad that we still believe in Wave-Particle Duality.

Secret

It's so painful to type a questiono on the main site now cause after some time the latex ceased to render

user116211

@Secret what?

Hari Prasad

@user36790 But why? It led to Quantum Mechanics after all.

user116211

@HariPrasad So?

Secret

12:09 PM

@user36790

Hari Prasad

@user36790 Then why do you think it is an underrated physics theory

Secret

I am going to check my typiing on overleaf and the move it into the main site

user116211

@Secret Ha! I also experience this when my connectivity is slow.

user116211

@HariPrasad Let me complete my statement

user116211

@HariPrasad No. Ultraviolet Catastrophe played the role in bringing the Old Quantum Theory.

Hari Prasad

12:12 PM

@Secret Clear your cache and save the written work into notepad the refresh your page. It will be ok

user116211

@HariPrasad Actually it is overrated; in most of the books, it has been mentioned; but actually there is no such thing.

ACuriousMind

@Secret What exactly is supposed to be your question there? Any state in the combined state space is "geometrically a tensor" because the combined state space is a tensor product. You have to note that $\mathcal{H}_1\otimes\mathcal{H}_2$ is not the space of multilinear maps $\mathcal{H}_1\to \mathcal{H}_2$, which would be $\mathcal{H}_1^\ast\otimes\mathcal{H}_2$.

(the two spaces are isomorphic in the finite-dimensional case, but not the same, the latter has one bra and one ket, while the former has two kets)

user116211

2

A: Electrons - What is Waving?

According to quantum electrodynamics (QED), which encodes the properties of electrons and photons, electrons are excitations of an electron fiueld in the same way as photons are excitations of the electromagnetic field. The fields wave, and the electrons (or photons), as far as they can be cons...

user116211

@HariPrasad: Read the ans above^

Secret

12:34 PM

@ACuriousMind I think you clarified the part of the question where "is the entangled state gemetrically a 2nd order tensor in hilbert space?", the $\mathcal{H}_1^* \otimes \mathcal{H}_2$ somewhat clarified the second part of my question, but (now that I look at my question again in more detail) I still have some doubts (that I am not sure how to describe it in words). Thus for this question I am deciding to post it on the main site once I organised my query properly

Hari Prasad

The following statement is true.

The preceding statement is false.

@ACuriousMind Does physics.SE have a community blog?

ACuriousMind

Nope

Hari Prasad

@ACuriousMind why don't the start one?

ACuriousMind

@HariPrasad I guess there just was never the critical mass of writers and interested people needed to get serious about it, see this meta post.

Hari Prasad

12:49 PM

@ACuriousMind I think we need to raise the idea in physics meta once again. The last one was 4 years ago.

I'am pretty sure that now we have enough people out there

@DavidZ What do you think?

David Z

I think the situation hasn't changed - that there still isn't sufficient interest - but you're certainly welcome to ask. I would be happy to be proven wrong on that.

Hari Prasad

I could do blogging all day

ACuriousMind

@HariPrasad The point is not to have one or two people write on that blog whatever they like.

Hari Prasad

@ACuriousMind yes i know it its a community blog.

user116211

@HariPrasad why should we need a community blog, BTW?

Hari Prasad

1:01 PM

I have an idea what about inviting articles from physics.SE members for this very purpose and then if we have enough of them in a limited time (say in one day) the we can be sure that there are interested people out there. Also we can do this process to get articles for the blog later on.

ACuriousMind

@HariPrasad 1. One day is far too short. 2. Why should people write articles of which they cannot be sure they'll ever even appear anywhere?

Hari Prasad

@user36790 A community blog will be great to showcase trending Q&A in form of articles and it will benifit not only Physics.SE members but also others outside

user116211

@HariPrasad We have newspaper for that.

ACuriousMind

@HariPrasad How will it benefit users?

user116211

@HariPrasad: stackexchange.com/newsletters/…

Hari Prasad

1:05 PM

@user36790 Then why does physics and science BLogs and bloggers exist?

@user36790 That can't be used to showcase to a large group of people.

user116211

@HariPrasad The point is that they have not Q&A site like PSE.

user116211

@HariPrasad How can you say so?

Hari Prasad

@ACuriousMind Users can gather their answers from similar questions and make it an article to showcase their work

ACuriousMind

@HariPrasad Their work is already showcased on their profile. I think the blog should be a place for the kind of things for which the Q&A format is not suited, like longer expository articles

user116211

@ACuriousMind And that is what PSE is not meant for.

ACuriousMind

1:12 PM

@user36790 That's why it would be in the blog

user116211

@HariPrasad: Let you make a shot by asking at meta.

user116211

Also don't forget to mention how it would be different from the newsletters.

ACuriousMind

If we had a sizable number of people willing to write for it, I'd be all for it, but I don't see it happening. The math.SE blog seems to have died a slow death of inactivity, too.

user116211

Let everyone decide on it.

user116211

@yuggib: o/

yuggib

1:14 PM

\o/

user116211

@yuggib Wow! So, happy today!!

yuggib

yeah...I'm home with my girlfriend ;-)

user116211

@yuggib oh! Enjoy!!

Hari Prasad

@ACuriousMind Questions which are too broad needs an answer which is not scattered in different locations so we need a blog

yuggib

thanks ;-)

user116211

1:16 PM

@ACuriousMind: Do you celebrate St. Patrick's day?

yuggib

I could celebrate (it's my middle name)...but celebrating saints is silly

user116211

@yuggib wtf! You don't enjoy those green hats?

ACuriousMind

@user36790 I think it's safe to say no one here cares about that day

user116211

@ACuriousMind ;/

yuggib

i

I'm pretty positve that neither Irishmen like those silly hats

ACuriousMind

1:19 PM

@HariPrasad No. We're not under an obligation to provide answers to every possible question. And questions which are "too broad" tend to be either also opinion-based or really require textbooks to answer them.

You'll not find many people willing to write textbooks for free for a blog _P

yuggib

terry tao wrote stuff for free on his blog, and then made book(s) out of it

user116211

@yuggib this prodigy!

Hari Prasad

@yuggib yes we could publish yearly ebook of best answers too

user116211

@HariPrasad why? What's the point for that?

user116211

After all, PSE is going to be an AI :P

Hari Prasad