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Almost Sure

@almostsure.bsky.social

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

825 Followers  |  91 Following  |  293 Posts  |  Joined: 30.08.2023  |  1.4259

Latest posts by almostsure.bsky.social on Bluesky

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just invented perpetual motion

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

something something Gumbel something

27.01.2026 14:45 β€” 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 β€” πŸ‘ 4    πŸ” 1    πŸ’¬ 2    πŸ“Œ 0

The Producers by Mel Brooks

22.01.2026 12:46 β€” 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 β€” πŸ‘ 417    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 β€” πŸ‘ 2    πŸ” 1    πŸ’¬ 0    πŸ“Œ 0

β€œagain! again!”

18.01.2026 21:08 β€” 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 β€” πŸ‘ 2    πŸ” 0    πŸ’¬ 0    πŸ“Œ 0
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β€œdo you even lift bro?”

18.01.2026 20:56 β€” 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 β€” πŸ‘ 5    πŸ” 0    πŸ’¬ 0    πŸ“Œ 0

that was sister sledge

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

Woke up to this sight

16.01.2026 20:26 β€” 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 β€” 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 β€” 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 β€” 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 β€” 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 β€” 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 β€” πŸ‘ 3    πŸ” 0    πŸ’¬ 0    πŸ“Œ 0

so how hard are these ErdΓΆs problems anyway?

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

Land line
analogue tape
analogue clock
real life

13.01.2026 23:40 β€” 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 β€” πŸ‘ 1    πŸ” 0    πŸ’¬ 0    πŸ“Œ 0

so convolution is replaced by scaling your function by exp(iax) before convolving

12.01.2026 14:29 β€” πŸ‘ 1    πŸ” 0    πŸ’¬ 1    πŸ“Œ 0

convolution is linear combinations of translations.
Or, the infinitesimal generator (d/dx) of translations.

Fractional FT replaces by cos(theta)X+sin(theta)(d/dx)

or, in non-infinitesimal form, the translation operator is replaced by

f(x)->exp(iusx)f(x+uc)

for parameter u.

12.01.2026 14:28 β€” πŸ‘ 1    πŸ” 0    πŸ’¬ 1    πŸ“Œ 0
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Another aspect on fractional Fourier transforms. Its generator is the same as the quantum harmonic oscillator, so they are the same as time evolution of the quantum system!

12.01.2026 13:58 β€” πŸ‘ 2    πŸ” 1    πŸ’¬ 0    πŸ“Œ 0

In Quantum Mechanics, Fourier transforms are used to convert between position (X) and momentum (P) space.

Defining a mixture,

A(ΞΈ) = X cos ΞΈ + P sin ΞΈ

then the fractional Fourier transform converts from position to A(ΞΈ) space (for ℏ=1 in my formula for fractional FT)

12.01.2026 13:58 β€” πŸ‘ 2    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 β€” πŸ‘ 4    πŸ” 1    πŸ’¬ 2    πŸ“Œ 0
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Ghost fox?
So the other night a fox came up to me with a tennis ball in its mouth. Quite unusual so tried taking a picture, but fumbled trying to select camera app and it was already walking away by the time I was ready.
But why can you see through it?

12.01.2026 13:44 β€” πŸ‘ 1    πŸ” 0    πŸ’¬ 0    πŸ“Œ 0

β€œjones dual” to avoid confusion

12.01.2026 10:01 β€” πŸ‘ 5    πŸ” 0    πŸ’¬ 0    πŸ“Œ 0

The hat really made a difference!

11.01.2026 18:29 β€” πŸ‘ 0    πŸ” 0    πŸ’¬ 0    πŸ“Œ 0

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