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Physics Meta

4:21 AM

-2

Q: If this considered an inappropriate answer, what is an appropriate? (origin linked)

The origin problem. Mark the current for each segment. There are three unknowns $I_0$, $I_1$, and $I_5$, therefore set up a set of 3 linear equations for these three unknowns. Then solve the coupled linear equations. Gook luck!

discussion

1 hour later…

More Anonymous

5:26 AM

@Shing What if I'm thinking of molecules?

1 hour later…

Nihar Karve

6:39 AM

Here's the timeline for daily questions asked on Physics.SE

I wonder what happened on that one day in early 2016

2 hours later…

Slereah

8:33 AM

You can just check

probably something physics related in the news

Nihar Karve

I think it's just a routine statistical anomaly

LIGO had published their paper about 5 days prior to that day, but only 8 questions are about gravitational waves

Slereah

8 out of 100 could be enough to do that I guess

Nihar Karve

Apart from that, Boutros Boutros-Ghali passed away that day

don't think there's a correlation there

@Slereah for comparison, the day after the paper there were a whopping 28 posts with [gravitational-waves]

ACuriousMind

9:00 AM

there can be secondary effects - people are googling LIGO because it's in the news, find the popular posts from a few days earlier, then think "huh, this site is neat, let's ask this other question I've always had"

Slereah

Also IIRC rise and fall of questions on PSE correlate a lot with school seasons

ACuriousMind

yeah, that's the overall periodic pattern you see there

1 hour later…

Nihar Karve

10:20 AM

the real question is about quality

I can make a query that uses the fraction of (non-deleted) [homework-and-exercises] questions as a proxy, but I'm not sure how effective that would be

3 hours later…

Vincent Thacker

1:31 PM

@NiharKarve I recall the most recent one being Veritasium uploading his faster-than-wind video

which resulted in quite a few questions here about it

Nihar Karve

2:10 PM

I think Veritasium's one-way speed of light video has resulted in 100+ questions on this site

quite remarkable

Shamina

2:57 PM

Any inputs can be extremely helpful!!!! Billion thanks in advance!!!!

Q: Calculating cyclotron orbits in a lattice

I have a naive question, is it possible to obtain the wavepacket dynamics that give rise to cyclotron orbits from a real space tight-binding Hamiltonian? Consider a square lattice in the presence of a constant magnetic field that amounts to say that the hopping elements acquire a phase. Let $H = ...

quantum-mechanics solid-state-physics

ACuriousMind

3:29 PM

@NiharKarve quality is extremely hard to measure over time because as the userbase fluctuates, the number of voters does, too

additionally it's influenced by the topic - there are some tags where a total vote of 10 is very high, and some where it's merely quite good

votes per view is similarly a flawed metric because you don't know how many of these views are even elegible to vote

I would see HW questions as orthogonal to "quality" because you can have well-written questions that run afoul of the HW policy and complete garbage that is technically on-topic :P

Physics Meta

3:45 PM

-2

Q: Free fall of different bodies at same rate

From brief history of time- One can now see why all bodies fall at the same rate: a body of twice the weight will have twice the force of gravity pulling it down, but it will also have twice the mass. According to Newton’s second law, these two effects will exactly cancel each other, so the accel...

discussion support

Nihar Karve

4:08 PM

@ACuriousMind do you know why there's a drop in the % of HW-tagged questions circa 2018?

satan 29

Hi everyone!

I wanted to do a calculation, I have a matrix m = {{t,t+1},{t-1,t}}. I wanted to find an expression for m^n
in terms of t and n

wolfram isnt able to answer properly when the index is variable..

Any idea how to do this in mathematica?

ACuriousMind

@NiharKarve not off the top of my head, no

maybe Qmechanic got lazy tagging them :P

Nihar Karve

4:37 PM

and on that note, here is the progression of edits performed by Qmechanic as a fraction of all edits!

incredible consistency

...although sorry, the graph is a bit faulty (the consistency point still stands)

Physics Meta

5:02 PM

Q: Is use of "spoiler" formatting appropriate on this site?

I've seen the spoiler formatting used on other sites where, say, they discuss plot elements of movies and people don't want to give away a key element to someone who hasn't seen the movie and is browsing casually. I didn't realize that this was implemented by a generic feature of the markup that...

discussion formatting

ACuriousMind

@NiharKarve did you recently learn SQL or why are you crawling SEDE for random data? :D

Nihar Karve

5:17 PM

I only discovered the graph feature today :)

satan 29

@ACuriousMind SEDE?

ACuriousMind

stack exchange data explorer

5 hours later…

Nike Dattani

10:01 PM

I worry that the MMSE community might not have enough experts in this specific area yet to get a timely answer, does anyone know people working in this area?

Q: Tools for symbolic calculations of quantum transport using the Keldysh NEGF formalism

I am looking for tools for symbolic calculation of quantum transport or quantum mechanics that involves Keldysh NEGF (non-equilibrium Green's function) formalism. The closest tool I heard/seen is symGF.m for Mathematica but I could not find the library/file for it. Have anyone seen this file o...