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02:05
0
Q: Why are administrators trying to cover up their mistakes?

John RawlsIt has come to my attention that I agree, I did make some mistakes as coming off as hostile in this post. However, it should be noted that the substantive message within this meta post still stands. The moderators on this exchange clearly have no "chill" at all as they would automatically downvo...

@ACuriousMind Are you around?
03:10
@Semiclassical @Slereah Suppose by division by zero, you mean adjoining a multiplicative inverse of zero to the algebraic system. Then I proved the following:
Division by zero algebra Theorem 1: Given any algebraic structure $(S,\cdot,+)$ such that $\cdot$ left distribute over $+$ and the underlying set $S$ arbitrary, and that there exists a left or right multiplicative inverse to a left or right additive identity, the addition structure must have the following form:
(see in my main chat room in the above link for the proof)
But basically, the main thing about zero inverse that really messed up what we knew about numbers, is that multiplicative identities become idempotent under +
$1+1=1$
which one can easily show that (since the non necessary associative algebraic structure is left distributive)
$x+x=x$
for any $x$ in the algebra
In other words, natural number addition no longer makes sense in these algebraic structures because you ether get something unchanged, or you frequently have $x+y=y$
I have yet to fully investigate what happens for the multiplication structure, because that one is a lot less trivial for an underlying set of infinite cardinality
In addition, for finite structures, there are around 5 no-go theorems I proved 2 years ago which show that the addition becomes quite trivial since you have for some given $x$, $x+y=y$ for all $y$
(and hence for finite structures, I don't consider that division by zero since every element becomes a left or right absorber)
Meanwhile in the literature, there are only 2 known structures that allows some notion of division by zero: Wheels and Meadows.
Wheels modified the distributive law and introduce an involution operator to mean division thus result it to become an extension of rational fields
Whereas meadows deals with the issue of division by zero by introducing some sort of pseudoinverse $yxy^{-1}-(something)=x$
Both structures does not permit a zero inverse. Particular, for wheels, it has been shown in the paper that attempt to put in a zero inverse collapse the wheel into the trivial wheel $\{0\}$
Proposition 4.4 in particular for the claim I made about collapsing into the trivial wheel
Actually I might have misinterpreted proposition 4.4, it only said that if any of the new elements is the same as 0 or 1 then the wheel becomes trivial
Thus I am actually not sure what will happen if we adjoin a zero inverse into wheels
03:39
@CaptainBohemian wdup dawg
I might check that out after my PhD
03:57
my point was that JD's answer was not a middle school answer to the question "why can you never divide by zero in the set of real numbers," instead he gave the "elementary school" answer.
ie asking "how many nothings are in something" doesn't take into account negative numbers; which should have been presented by the middle school years
Indeed
For a middle school answer. Tell them to note that since everything multiplied by zero is zero, and since division is defined to be a number which multiplied to a hive number is 1, then you cannot find such number q for q0=1 because of the aforemented property
For a graduate answer. 0x=0 for all x in rings, thus there exists no such q which q0=1. In other words, the zero map is not injective nor surjective, and hence it is not invertible
Meanwhile, I am not sure if my own answer is the most general answer to the existence of a zero inverse without modifying any of the axioms other then throwing away cancellation (and hence negative numbers)
04:14
Ok, but if you had a ratio that has degrees Celsius in the denominator there is a real situation that can not be described at 0 C
or even (profit/loss) in the denominator
What situation when we have 1/x degC where x tends to zero?
I cannot envision anything physical that will have "1/0" degree celcisus
Let's say we counted the number of birds in an area as the the temperature falls from above zero to below zero
birds/temperature
O. Then you are dealing with functions of the form bird(t)/T(t), which what happens as you approach T(t)=0 depends on the limit of this ratio if exists
Yup, so dividing by zero does make physical sense in this situation.
The point here is that what happens in the neighbourhood of that point "n/0" depends on how the two functions values behave as they approach it and since there are many possible ways for a pair of functions to approach a point, "n/0" is no unique and sensitive to the details of the functions near that point
So at "n/0", it can be defined as any number without changing the outcome
which makes it meaningless in the context of functions assuming you don't allow projective space stuff)
04:28
Also there can be no birds at 0 C and it still makes sense here.
which makes it meaningless in the context of functions assuming you don't allow projective space stuff
@skullpatrol yes, that will be the 0/0 scenario
Indeed.
Though, if n is positive n/0 goes to infinity since the denominator is getting smaller in magnitude and hence the ratio must grow without bound
In my opinion, the stronger elementary school answer is to talk about division as "sharing among" rather than JD's answer.
Indeed. If no one is sharing nothing, we cannot make sense on how many things everyone gets since they are no people for you to count
04:38
Yup, the question itself does not exist.
05:10
@bolbteppa I need to memorize the Riemann tensor
@0celo7 I memorised the Riemann tensor for Minkowski space
 
2 hours later…
07:04
> Villani is part of Macron’s effort to change France’s political landscape, drawing into parliament people who are not professional politicians. The scientist has attempted to be more than just a new face. A fan of Marvel Comics’s Amazing Fantasy, Villani abides by the superhero’s mantra that “with great power comes great responsibility.”
Looks like politics are also starting to join the intermix party
But yeah, scientists are a rare breed in politics, even in australia
07:32
Don't forget that just over a year ago, the people of the United States elected a man with absolutely no political experience to do what's probably the most challenging political job in the world. Maybe Macron's thinking "I gotta get me some of that".
07:46
lol
well ,true though
I am not sure what pro-mathematics policy will do though, other than the obvious AI and data science stuff
08:06
@Slereah the problem is not that John Duffield doesn't know any maths beyond school level, it's that he is proud of not knowing any maths beyond school level and contemptuous of anyone using maths beyond school level in physics. This sets a dreadful example to any students unfortunate enough to take him seriously.
> The problem is that he is proud of not knowing any maths beyond school level and contemptuous of anyone using maths beyond school level in physics
yesterday, by Secret
$$\huge{\text{We need maths for this discussion to even go anywhere}}$$
Anonymous
I do see him linking papers which use some pretty rigorous differential geometry. I wonder how much of that he actually understands, before citing the quotes
and this is no good, because maths is needed for us to cross check models
Anonymous
I still can't get over the fact that he said that "Electron's mass alters when we lift it up"
Anonymous
That was the epitome
08:12
@Blue I am not sure how much he had changed during that one year absence, but back in 2011-2014, he is known as Farsight in sciforums.com and members there have repeatedly pointed out he is cherry picking quotes that support his views without understanding what the full context of the readings
Anonymous
@Secret "repeatedly pointed out he is cherry picking quotes that support his views without understanding what the full context of the readings" I told him the same thing several times. The problem is he feels we are saying "Einstein was wrong" when actually we are saying "JD is wrong"
1
Q: Why is a collection of non-interacting bosons pathological?

SRSIn this lecture titled "Disorder and Interactions: From Spin Chains to Cold Atoms" the speaker Thierry Giamarchi claims that a collection of non-interacting bosons is totally pathological. His argues it as follows (around 5.43 minutes of the lecture): If you take free bosons they fall into th...

Interesting question.
Why is that interesting? It asks about an out of context statement from a talk that none of us have access to. How can we possibly answer that?
Anonymous
Isn't the talk accessible on the Youtube lecture link the OP provided?
08:26
OK, so we have to watch a 43 minute video to find out what the speaker meant. Great.
Anonymous
@JohnRennie Well, you could mention in a comment that you would like the OP to try to summarize the talk in the post as much as possible...
Or I could just ignore the question and vote to close it as unclear.
Anonymous
I was just not sure what you meant by "none of us have access to"
@Blue is there a link to the talk in the question? At a quick glance I didn't see one.
Ah yes. The word this is the link.
Anonymous
Yep, the link is given. The hyperlink highlighting on PSE is not so clear
Anonymous
08:30
Camouflages with the rest of the text
Anonymous
The question looks reasonable to me though. Having been in such situations before (misunderstanding what a lecturer means in a video lecture), I don't think would be a good idea to close questions citing particular portions of a lecture, as off-topic. That said, you could down-vote it for not summarizing the lecture sufficiently, so that people don't have to watch the lecture fully, and mention that in a comment.
For me, interesting is more like a feeling (e.g. in this case, I never thought about what is piling up when you have n bosons in the same energy level and n tends to infinity), but it is not the same as this is a good question
Perhaps my thinking is not quantum enough and still think of bosons as some ball shaped clouds that passes through each other
Put it simply:
$$\text{This question is interesting} = \text{I have never thought about this} \neq \text{This question is a good question}$$
Anonymous
At least it's a good question compared to the 50% homework questions which cover the front page of the PSE site :P
Anonymous
I have stopped visiting the main page since several months now due to the quality drop
08:46
yeah, questions that pop up at the new feed items are usually interesting or good in some way
as for front page, occassionally, one of the first 10 questions contains something interesting or is good, but most of the time they are homework questions
I think the speaker is arguing that modelling the interaction as a perturbation is pathological.
That is, if you start with non-interacting bosons they settle into a BEC. If you now attempt to turn on a small interaction as a perturbation then because the you have lots of bosons in the same state even a tiny interaction results in a large total interaction energy and spoils your attempt to treat it as a perturbation.
This comment is overtly aggressive, could you please remove it? @JohnRennie
@skullpatrol I have a policy of not engaging with John Duffield. If you think the post is unacceptable either ping a moderator or flag the post.
ok, np
thanks for checking :-)
::reviews personal engagement policy::
09:05
@JohnRennie yeah I recall BECs are highly correlated states which is why they are such a challenge to model computationally
On a slightly related note, is it really true there are no upper bound on the number of bosons we can cramp into the same state?
@skullpatrol there are lots of interesting people who visit the chat room, and you can learn a lot from them. John Duffield isn't one of those people.
because I will imagine any interaction in a state with unbounded number of bosons will diverge very quickly even without perturbations?
@Secret in principle yes. The density can increase without limit - subject to turning into a black hole of course.
ah right
Anonymous
Hey there! I have a question, if you could help me with it. I have a soap film with a closed elastic thread inside. There is a sliding wire at one side of film. What will happen to the radius of the elastic thread when the wire is moved outwards?
Anonymous
09:15
I thought, the film will of course try to reduce its area and hence the radius will increase, but it is not so :(
Anonymous
My teacher confused me and got confused himself on this question. Help :/
@DivyankaS.Chaudhari The surface tension of a soap film is constant, so it is not changed when you slide the wire inwards of outwards.
A soap film is not like a rubber sheet. With a rubber sheet the tension increases when you stretch it, but with a soap film the tension stays constant.
Anonymous
So, what happens to the elastic thread circle in there?
Nothing. It remains unchanged.
Anonymous
Oh, I see. Thanks for that, I was unaware! My teacher gave me such explanations that.. Nevermind! Thanks!
09:32
Does anyone here have the pdf of Einstein Gravity in a Nutshell by Anthony Zee?
@Blue The homework questions on MSE are sometimes interesting though :P
@SwapnilDas Ah, I see you're following up on my advice? Wait i'll send you a link
@PrathyushPoduval Of course, you're followable ;)
@SwapnilDas I might know someone who has a copy. Allegedly :-)
It's somewhere in there
Thanks a ton.
09:33
No problem!
@JohnRennie You meant Slereah?
@PrathyushPoduval I was about to say you should probably delete that :-)
Dang
I went to buy some pastry supplies
Anonymous
@SwapnilDas libgen is the place to go, for books ;)
Turns out I was also out of yeast!
Gonna have to go back
So that I can bake some bunnies
09:34
:P
@JohnRennie Yeah, I shouldn't put it up for everyone :P
@Slereah Aren't you french?
Yes, yes I am
Why is that relevant
Are French people supposed to never run out of pastry supplies
@PrathyushPoduval You are an UG?
@Slereah Aren't there rules preventing you from baking on sunday? (I read some news about a pastry guy getting fined it)
Ah, right. I should go buy groceries today or I'll starve the next two days :P
09:36
@SwapnilDas After a few months, i will be
Wait, you're in 12th in India?
@PrathyushPoduval I think you may be confusing France with some kind of imaginary land
Nope
I'm pretty sure, lemme search for it
also it's not sunday, so
Not really a problem
Anonymous
Villani says the French are good whiners :P
09:36
@SwapnilDas I passed out 2 weeks ago
@Blue Cedric?
Anonymous
@SwapnilDas Yea
@PrathyushPoduval JEE mains next week?
@Slereah shit it isn't a sunday today? I forgot that..
@SwapnilDas Yeah
Still 3 full days off!
09:37
@PrathyushPoduval you've been working too hard :-)
@PrathyushPoduval ...and when did you regain consciousness? :P
@PrathyushPoduval How did you manage to do so much study in such a young age? :P
@PrathyushPoduval please note that this doesn't specify sunday :p
@JohnRennie Too less would be more like it :P, I've been sitting in my home doing nothing all the time, no classes so everyday's the same
09:38
Many bakeries are open on sunday
("pass out" means to fall unconscious, and not much else)
@PrathyushPoduval installing Linux counts as work :-)
@ACuriousMind I meant graduate :P
Anonymous
"BRITISH
complete one's initial training in the armed forces."
passing grade?
09:39
@JohnRennie Lol yeah, but these holidays havemade me more lazy, don't know how i'll be able to adapt to the college load now :P
@SwapnilDas Well, I kept reading random stuff, eventually all the random stuffs started connecting with each other
@PrathyushPoduval You want to do physics in future?
Yeah, I'll be joining IISc, so the future is near :P
You're ready to study Chem and Bio for 3 years?
@Slereah Oh okay, i automatically assumed sunday would be that free day :P
Ah, well, it appears to "pass out" is one more thing specific to Indian English
09:41
@SwapnilDas 3 semester
@PrathyushPoduval Oh three sems, then fine.
Anonymous
Knowing a little bit of Chemistry and Biology is good
Anonymous
Even for Physics
@ACuriousMind Yeah, there are lot of such slangs somehow being used here
that's why English is such a mixed bag :P
09:43
@Blue Yeah, knowing other subjects ateast in the basics can help interconnect different topics at the basic level
There was this bio reasearcher from tifr who gave a talk at the vijyoshi camp
Anonymous
True, I'm not really a fan of specializing early
Anonymous
@PrathyushPoduval Cool, name?
she made it look like her work was damn interesting and simple, studying how the whiskers connect to the brain
Shubha Tole
Wife of Sandip Trivedi?
Anonymous
Shubha Tole (born August 1967) is an Indian neuroscientist, Professor and Principal Investigator at the Tata Institute of Fundamental Research in Mumbai, India. Her research involves investigating the development and evolution of the mammalian brain, and she has won many accolades for her work. She is famous for having discovered a gene that is crucial to the proper formation of the hippocampus, amygdala, and cortex of the brain, winning the Infosys Prize in the Life Sciences category in 2014. However, Tole’s work does not end in her lab. She is dedicated to fostering an appreciation and application...
Anonymous
09:44
Interesting profile
@SwapnilDas wife of who?
Anonymous
Nice
Cosmologist Sandip Trivedi, working on Inflationary Universe
huh google knows him, it autocompleted his name almost immediately
Anonymous
09:46
Probably because you searched for Shubha Tole before that
@SwapnilDas google says yes
Anonymous
Google's search algorithms are getting better everyday
@PrathyushPoduval Oh yeah!
@Blue the next facebook
you know the guy?
Anonymous
@PrathyushPoduval It's already way way ahead of Facebook in terms of user data ;)
Anonymous
09:47
The Americans know everything about each of us :P
heh heh, cia gonna come knocking on your roof one day
@PrathyushPoduval So you've planned to become a Theoretician?
what's to know?
well, i've not planned anything
@PrathyushPoduval Better
09:48
i'm just gonna go with what I find interesting
My JEE maths is going into hell
you giving jee this year?
Nope, next
just do olympiad maths, you'll be fine
Irrelevant right?
09:50
not at all lol
you'll be able to develop lots of trick on your own
Most things are out of syllabus, especially 12th portion?
because of my olympiad maths, i didn't have to study jee maths
Huh!
Most people say the opposite
all those jee books of mine are gathering dust, not being opened for the past 2 years
How about Calculus and all
They're not in Olympiad maths?
@PrathyushPoduval And as thing have gone so far, please tell me what books did you use for 12th mathematics? :P
09:53
@SwapnilDas there are lots of calculus olympiad problems too
like putnam ones
wait a minute
Putnam... Ham tumhare aukat ke nahin
lol you'll gain a lot
@SwapnilDas There are easy and moderate putnam problems too :P
I will start from 0 bro :P
see, olympiad maths is about thinking more on your feet, and applying what you know in creative ways
This will help you in competetive exams, where you've to do things in a short time
I developed many neat tricks during when I had given mock tests, they're quite useful
@PrathyushPoduval That creativity had to be developed long time ago
09:55
I started in 11th
started revising in
:P
lol nope, i never got selected in maths olympiad
till the camp
i did get selected for the astronomy camp though, this year
Anonymous
Isn't the astronomy camp mostly a physics camp?
well, there are lots of non physics things too
@PrathyushPoduval Qualified RMO right?
Anonymous
09:59
@PrathyushPoduval Example?
Anonymous
I don't have much idea about the Astro olympiad
@Blue Telescopes, coordinate systems, timekeeping systems, CCD photography, messier objects (have to mug all 110 of it), then most of them are physics

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