Communities

Writing
Writing
Codidact Meta
Codidact Meta
The Great Outdoors
The Great Outdoors
Photography & Video
Photography & Video
Scientific Speculation
Scientific Speculation
Cooking
Cooking
Electrical Engineering
Electrical Engineering
Judaism
Judaism
Languages & Linguistics
Languages & Linguistics
Software Development
Software Development
Mathematics
Mathematics
Christianity
Christianity
Code Golf
Code Golf
Music
Music
Physics
Physics
Linux Systems
Linux Systems
Power Users
Power Users
Tabletop RPGs
Tabletop RPGs
Community Proposals
Community Proposals
tag:snake search within a tag
answers:0 unanswered questions
user:xxxx search by author id
score:0.5 posts with 0.5+ score
"snake oil" exact phrase
votes:4 posts with 4+ votes
created:<1w created < 1 week ago
post_type:xxxx type of post
Search help
Notifications
Mark all as read See all your notifications »
Q&A

Construction, similar to Chow's EL-numbers. Is it valid? What are the properties?

+0
−2

The idea of EL-numbers, proposed by Chow, impressed me very much, so I decided to build something similar and look what this will turn out.

Instead of $\exp(x)$ and $\ln(x)$ functions as the building blocks, let us take the following ones:

$l(x)=\ln \Gamma(x)$ and its derivative, digamma function:

$\psi(x)=l'(x)$

We apply these functions, as well as field operations, starting with number $1$.

So, what do we get? $$\pi=\psi(3/4)-\psi(1/4)$$ $$\gamma=-\psi(1)$$ $$i=\frac{l(2)-l(3)+l\left(-\frac{1}{2}\right)-l\left(\frac{1}{2}\right)}{\psi\left(\frac{3}{4}\right)-\psi\left(\frac{1}{4}\right)}$$ $$e=\frac{i \pi +\left(\psi \left(\frac{i}{2 \pi }+\frac{1}{2}\right)-\psi \left(\frac{1}{2}-\frac{i }{2 \pi }\right)\right)}{i \pi -\left(\psi \left(\frac{i }{2 \pi }+\frac{1}{2}\right)-\psi \left(\frac{1}{2}-\frac{i }{2 \pi }\right)\right)}$$

Moreover, we can express $e^x$ and $\ln x$ via these two functions:

$$e^x=\frac{i \pi +\left(\psi \left(\frac{i x}{2 \pi }+\frac{1}{2}\right)-\psi \left(\frac{1}{2}-\frac{i x}{2 \pi }\right)\right)}{i \pi -\left(\psi \left(\frac{i x}{2 \pi }+\frac{1}{2}\right)-\psi \left(\frac{1}{2}-\frac{i x}{2 \pi }\right)\right)}$$$$\ln x=l(x+1)-l(x)$$

As such, it turns out that the EL-numbers are a subset of this system.

That said, I wonder whether one of the functions I took as the elements is excessive? Can we keep the same system, using only one of them? Or, maybe, $\psi^{(1/2)}(x)$? What would be the qualities of the respective systems if we included only one?

What if, instead, we include all integer derivatives of digamma $\psi^{(n)}(x)$? It seems, in the later case, Catalan constant also can be expressed (as $\frac1{16}(\psi'(3/4)-\psi'(1/4))$).

P.S. It seems, if we take $i$ as the basic number, we can express $\pi, \gamma, e$ using only digamma function, without need for the first function.

History

2 comment threads

If you cross-post the same question on multiple sites, you should include links to all other versions... (1 comment)
Copied from https://math.stackexchange.com/questions/4552218/construction-similar-to-chows-el-numbers... (1 comment)

Sign up to answer this question »