secular

@secular@mathstodon.xyz

#Mathematics & #Physics PhD candidate @ University of Bath working on parallel #TensorNetwork #algorithms for #quantum lattice systems. Pro #equality, #education & #OpenScience. Anti #bigotry, #misogyny & #pseudoscience.

This profile is from a federated server and may be incomplete. Browse more on the original instance.

albertcardona, to Trains
@albertcardona@mathstodon.xyz avatar

In Europe, flying is cheaper than taking the train.

It's an embarrassment, and a major problem: we have to stop flying for silly short distances. Realise that the overheads of flying (reaching the airport, awaiting 2 hours, the flight, the unloading, reaching the destination) largely cancel out any time gains of flying. And the carbon costs are utterly untenable. Not to speak of the modern, dire conditions of the whole flying "experience".

Another embarrassment is that train connections can't be guaranteed when across countries or companies. They aren't even coordinated. As if those who commission and set the schedules didn't travel by train themselves, at least not internationally. In considering how tiny most European countries are, it's frankly bizarre.

There are so many destinations one could travel by train to, yet in practice, it's not sensible. A disgrace.

The upside is that it can be fixed.

#trains #EuroRail

secular,

@albertcardona So true! And even within the UK it's so expensive to travel from place to place that people are no doubt using cars or planes instead. Have a look at the cost of a return ticket from Bristol to London for example.

BartoszMilewski, to random
@BartoszMilewski@mathstodon.xyz avatar

One should be careful with the classical limit of a quantum theory. With the Planck constant going to zero, the frequency of a photon with a given energy (\nu=E/h) goes to infinity.

secular,

@BartoszMilewski @j_bertolotti This thread led to me coming across a nice paper on the topic from the 1990s.
https://journals.aps.org/pra/abstract/10.1103/PhysRevA.50.2854

secular, to random

I really like this online SVD image compression demo:
https://timbaumann.info/svd-image-compression-demo/

j_bertolotti, to physics
@j_bertolotti@mathstodon.xyz avatar

#PhysicsFactlet
A quantum simple pendulum.
The pendulum position is spread out, with opacity here being proportional to the probability that the pendulum is at that position at a given time. The average position of the quantum dynamics is the same as the classical pendulum dynamics (Ehrenfest theorem).

Technicalities: I used the Crank-Nicholson method to evolve the system in time. This is a 1D problem, and the only variable I considered was the angle, with the initial state being a Gaussian.

#QuantumMechanics #Physics #ITeachPhysics #Visualization

Schematic drawing of a simple pendulum oscillating, with its quantum version represented as a distribution of pendula with their transparency proportional to the probability to be at a certain position at any given time.

secular,

@j_bertolotti Since this is not a harmonic oscillator, I would have thought the position and momentum expectation values would follow classical trajectories only approximately and only while the wave function remains fairly localised?

secular,

@j_bertolotti Still not sure why this should be the case here. It's not true in general that Ehrenfest’s theorem implies classical dynamics, and for this system I would expect the QM expectation value of the amplitude to decay to zero (as the initial wavepacket spreads out), whereas the amplitude does not decay classically for an undamped pendulum.

secular,

@j_bertolotti By the way, this is a fun example, thanks for sharing! Especially as it behaves differently to a harmonic oscillator. I don't have Mathematica though, so have had to try to reproduce your code using Python.

secular, to Help

#Website #hosting #help needed!

Anyone able to #recommend any #free or #cheap #WebHosting that's also reliable? Ideally UK based.

#tsohost have suddenly announced that they are putting up annual #prices by a factor of between 5 and 10. As a poor #student with no #income, I cannot afford this!

#Recommendations anyone? I need basic features like #email but nothing fancy as my personal website #domain doesn't get a large number of visitors or emails.

Thanks so much in advance!

j_bertolotti, to random
@j_bertolotti@mathstodon.xyz avatar

🤬 🤬 🤬
#BritishAirways overbooked my flight, so now I am on standby, the queue to the "customer service" is neverending, and I have no clue if and when I will manage to travel 🤬

secular,

@j_bertolotti Oh that's horrible. Can't believe airlines are allowed to do this. And I actually thought it was something only the notorious budget companies did.

secular,

@j_bertolotti How rude! I've never travelled with BA but I would have expected better. Sorry you're having such a rotten experience and thanks for sharing.

j_bertolotti, to random
@j_bertolotti@mathstodon.xyz avatar

And today stopped working completely on my phone 😖

secular,

@j_bertolotti I also had problems getting it to work last time I tried. Hope you can sort it! (I gave up in the end)

ColinTheMathmo, (edited ) to random
@ColinTheMathmo@mathstodon.xyz avatar

Just a quick question for the people here on Mathstodon.xyz ... where are you based?

If you're not in any of these, please let me know in the comments!

Please, if you're not on mathstodon don't reply here, but I'd love to hear from you another time.

secular,

@ColinTheMathmo @jesusmargar @squark137 Out of interest, what is/are the reason(s) for limiting surveys to small numbers of options? Has always felt very limiting to me.

secular,

@ColinTheMathmo @jesusmargar @squark137 Many thanks for the reply! I certainly understand the second argument, but shouldn't that be left to the user and not imposed "from above" as it were? Regarding "abuse", however, I was wondering what that means in this context. Sadly, I realise bad actors will abuse anything they can, but wasn't sure what harm they could do with say 10 rather than 4 survey options.

secular,

@ColinTheMathmo @jesusmargar @squark137 There are always edge cases :) Not a complaint from me - I was just puzzled as to why such a small number. Like is it related to bandwidth or disk space or something? I mean, I'm not expecting to be able to list all of the world's countries or languages, but it does feel a shame not to be able to even list all 7 continents :) I suppose 4 does at least allow for "yes" / "no" / "don't know" / "other" type questions.

secular,

@ColinTheMathmo @jesusmargar @squark137 I guess that's another issue altogether - how much should user behaviour be dictated by the software. Personally, I'm more in favour of as much freedom as possible - as long as it doesn't promote abuse/harm. I realise that's often a very fine line. Cheers!

secular, to physics

Favourite tabletop #physics #experiments ?

#pedagogy #science #education

secular, to mastodon

Does anyone have any advice on how to find people to #follow based on #interests or #keywords etc ? Seems I fundamentally misunderstood how #hashtags and #search work on #Mastodon.

secular,

@ColinTheMathmo Thank you very much. Have already been doing this to some extent, but had hoped there might be an easier way.

secular, (edited )

@ColinTheMathmo Thank you for this. I particularly appreciate your describing the discoverability issue as a "known, hard problem" rather than, for example, describing it as a "feature" :)

christianp, to random
@christianp@mathstodon.xyz avatar

Meta, the company that owns Facebook and Instagram, is reportedly going to launch a new ActivityPub-compatible social network on the domain threads.net.

I and @ColinTheMathmo, the admins of mathstodon.xyz, are wary of the effect this will have on the fediverse, so we're pre-emptively blocking that domain until we see whether Meta plan on trying to federate, and if so, under what terms they do so.
Once it becomes clear how threads.net works, we'll decide whether to permanently block it.

secular,

@christianp @ColinTheMathmo How does your policy compare with that of other Mastodon instances, do you know?

BartoszMilewski, to random
@BartoszMilewski@mathstodon.xyz avatar

I thought follow requests meant somebody wanted me to follow them, and I routinly refused them. I thought anyone could follow me.

secular, (edited )

@BartoszMilewski Apparently not everyone on Mastodon likes being followed by people they don't know. That has been a surprise for me, as I assumed people would like being followed (it means I find their posts interesting).

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