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Almost Sure

@almostsure

George Lowther. Author of Almost Sure blog on maths, probability and stochastic calculus https://almostsuremath.com Also on YouTube: https://www.youtube.com/@almostsure

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30.08.2023
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Latest posts by Almost Sure @almostsure

Wavefunction and Wigner phase-space distribution for a quantum harmonic oscillator. It just rotates at constant speed, as with classical mechanics

But for non-quadratic potential, such as pendulum type dynamics, the distribution spreads out and generates interference patterns

24.02.2026 03:21 πŸ‘ 2 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

hadn't really appreciated that the cross term is doing this, until I looked more closely at the visualization

19.02.2026 16:10 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

The visualization is interesting

Superposition of 2 gaussians has oscillating cross term. Cancels if you integrate along X or P direction

joint x-p direction, parallel to the troughs, cross term won't cancel

Instead it cancels with the gaussians to give diffraction pattern for X-P

19.02.2026 16:10 πŸ‘ 3 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
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in quantum physics position X and momentum P can’t be simultaneously measured.

But, linear combinations aX+bP 𝘒𝘳𝘦 observable, and their distributions can be used to back out the joint X,P probability density.

The Wigner distribution

but, it is 𝘸𝘦π˜ͺ𝘳π˜₯

19.02.2026 13:05 πŸ‘ 4 πŸ” 0 πŸ’¬ 0 πŸ“Œ 2

β€’ gamma function
β€’ Wigner quasiprobabilities
β€’ fractional Fourier transforms
β€’ Mistakes in probability (historical)
β€’ Ito’s lemma
β€’ Randomness in number theory
β€’ clickbait math, actually surprisingly interesting
β€’ probability doesn’t exist!

which YT vid you want to see next?

16.02.2026 13:40 πŸ‘ 2 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

bsky.app/profile/almo...

14.02.2026 16:11 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0
The Joy of Coupling
The Joy of Coupling YouTube video by Almost Sure

New YouTube video posted

β€œThe Joy of Coupling”

Happy Valentine’s Day!

youtu.be/rpW2ZYtXn6o?...

14.02.2026 16:11 πŸ‘ 6 πŸ” 3 πŸ’¬ 0 πŸ“Œ 2

YouTube video coming up tomorrow, on my channel, especially for Valentine’s Day!

β€œThe Joy of Coupling”

watch this space…

13.02.2026 18:48 πŸ‘ 5 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
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just invented perpetual motion

27.01.2026 21:33 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

I remember doing this stuff before. The coupon collectors problem. Could compute exactly and approximate, or approximate using a Poisson process from the start.

27.01.2026 14:50 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

something something Gumbel something

27.01.2026 14:45 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
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You’re probably familiar with Fourier transforms. But, did you know that it can be viewed as a 90Β° rotation in the time-frequency domain and we can rotate by any angle via fractional Fourier transform.
Explains why applying FT twice gives reflection (rotation by 180Β°).

12.01.2026 13:57 πŸ‘ 4 πŸ” 1 πŸ’¬ 2 πŸ“Œ 0

The Producers by Mel Brooks

22.01.2026 12:46 πŸ‘ 7 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0
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Inaugural Board of Peace meeting is under way

22.01.2026 10:58 πŸ‘ 416 πŸ” 162 πŸ’¬ 9 πŸ“Œ 12

Hey US-Americans, can you just give Trump Alaska? He won’t know the difference and might keep him quiet for a bit

21.01.2026 16:01 πŸ‘ 2 πŸ” 1 πŸ’¬ 0 πŸ“Œ 0

β€œagain! again!”

18.01.2026 21:08 πŸ‘ 0 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

OTOH, if things have gone wrong, and you have to use the slide, is it bad form to ask for another go?

18.01.2026 21:07 πŸ‘ 2 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0
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β€œdo you even lift bro?”

18.01.2026 20:56 πŸ‘ 7 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

#QOTD

β€œI never said even a fraction of the shit that’s ascribed to me”
– π΄π‘™π‘π‘’π‘Ÿπ‘‘ 𝐸𝑖𝑛𝑠𝑑𝑒𝑖𝑛

18.01.2026 15:15 πŸ‘ 5 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

that was sister sledge

17.01.2026 11:06 πŸ‘ 0 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

Woke up to this sight

16.01.2026 20:26 πŸ‘ 4 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0
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hey everyone!
I won the knowbell prize!

16.01.2026 16:14 πŸ‘ 3 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

Kids are really cute when they’re at that age where they haven’t yet worked out that giving you their snack means less for them

16.01.2026 15:49 πŸ‘ 2 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

Just cross off the last digit and take twice the last digit from what’s left

but…I usually combine with ad hoc techniques. Like…oh the number ends in 3, so add 7 and cross off the final 0.

15.01.2026 11:49 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

never mind, was just responding but it went away so I posted anyway. obvs a silly reply but you answered my question

14.01.2026 16:38 πŸ‘ 1 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
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hey @johnbull.wtf you can’t just post this and delete it!

14.01.2026 16:34 πŸ‘ 1 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
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A second hand yacht? Really? How poor do they think we are?

14.01.2026 16:30 πŸ‘ 3 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

so how hard are these ErdΓΆs problems anyway?

14.01.2026 16:24 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

Land line
analogue tape
analogue clock
real life

13.01.2026 23:40 πŸ‘ 3 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

it would be interesting to check exactly what happens if you do fractional FT to your two functions, then multiply and transform back. I expect convolution combined with a complex exponential exp(iaxy)

12.01.2026 14:32 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0