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Richard Penner

Arpie4Math@mathstodon.xyz

<p>SW Engineer, Amateur mathematician (contributed to metamath.org, oeis.org, ...), Legal Tourist (went to Honolulu in 2010 to watch the end of Sancho v. DOE).</p>

Posts

  • Post #4384045

    New: The Donald J. Trump Revocable Trust v. Capital One, N.A. (25-cv-21596) District Court, S.D. Florida https://www.courtlistener.com/docket/69853458/the-donald-j-trump-revocable-trust-v-capital-one-na/ 2013-2017 DOJ ran &quot;Operation Choke Point&quot; using informal pressure on banks to sever ties (&quot;de-banking&quot;) with high-risk-for-fraud businesses like payday lenders, firearm dealers, and pornographic film producers. 2021/01/06 #Trump holds #Jan6 rally 2021/01/20 Trump leaves of...

  • Post #4239594

    Cantor&amp;#39;s claim is that the infinity of the set real numbers, |ℝ|, is larger than the infinity of the set of counting numbers, |β„•|. If Cantor is wrong, then there must be a function 𝑓:β„•βŸΆβ„ such that the set of real numbers, ℝ, is exactly the same as the image of all natural numbers under function 𝑓, 𝑓(β„•) = { 𝑓(1), 𝑓(2), 𝑓(3), ... }. If Cantor is right, then there is no such function, 𝑓 where 𝑓(β„•) = ℝ. Cantor&amp;#39;s diagonal argument is, at its heart, a proof that a set of size 2^n is s...

  • Post #1728984

    Take a set, π‘₯. Is it finite or infinite? Well what definition do you use? β‘  βˆƒπ‘¦ ∈ Ο‰β‚€ π‘₯ β‰ˆ 𝑦 ; There is a natural number, 𝑦, such that you may may map 𝑦 one-to-one onto the set π‘₯, enumerating each of its members. So π‘₯ is finite for the same reason { 1, 2, 3 } is finite. β‘‘ Β¬ βˆƒπ‘§ ∈ (On βˆ– Ο‰β‚€) π‘₯ β‰ˆ 𝑧 ; There is no such infinite ordinal, 𝑧, such that you may map 𝑧 one-to-one onto the set π‘₯. So π‘₯ is finite because Ο‰β‚€, the smallest infinite ordinal, cannot be mapped 1-to-1 into it. Do β‘  and β‘‘ say the sam...

  • Post #1728983

    Begriffsschrift (1879), is one of the first manuscripts on #SymbolicLogic. As such, it literally invents a new language to describe the subjects the author, #GottlobFrege, wants to introduce. And this notation is very unlike what we see in math before or after this. So I will list some theorems adapted (by me, circa 2020) from #Frege with proper set-theoretical bounds. #SetTheory #Logic #Metamath