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Design theory is the subfield of combinatorics concerning the existence and construction of highly symmetric arrangements. Finite projective planes, latin squares, and Steiner triple systems are examples of designs.

9 votes
Accepted

Is every uniform hyperbolic linear space infinite?

The answer is "No".There exist a finite plane with required property. First of all, let's rephrase your question. Your uniform linear space is a synonym to a BIBD (balanced incomplete block design) wi …
Ihromant's user avatar
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5 votes
Accepted

Does every finite affine plane have the doubling property?

There is even stronger claim from which follows your answer. Claim. Any affine plane obtained from Veblen-Weddenburn projective plane by dropping one line don't have "doubling" property. Proof of this …
Ihromant's user avatar
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4 votes

Is every uniform hyperbolic linear space infinite?

First answer was just existence of such space. After routine computer search in large collection of BIBD collected by Vedran Krcadinac, I have two much smaller, nicer and more uniform examples. First …
Ihromant's user avatar
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3 votes

Is every uniform hyperbolic linear space infinite?

Other answer that satisfies your criteria. It's corrected $\operatorname{BIBD}(175, 7, 1)$ from Handbook of combinatorial designs VI.16.2 chapter. Corrected it is because this example is incorrect in …
Ihromant's user avatar
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2 votes

Is every uniform hyperbolic linear space infinite?

There is very simple example of hyperbolic $\textrm{BIBD}(91,7,1)$. It's following difference family: $[0, 8, 29, 51, 54, 61, 63]$ $[0, 11, 16, 17, 31, 35, 58]$ $[0, 13, 26, 39, 52, 65, 78]$ over cy …
Ihromant's user avatar
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1 vote

Is every uniform hyperbolic linear space infinite?

Obtained very interesting example (actually set of examples, but want to emphacise this one). It's classical (?) example of maximal $\{2^{m+n} - 2^n + 2^m;2^m\}$-arc in $PG(2,2^n)$ projective plane. D …
Ihromant's user avatar
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1 vote
Accepted

A graphic representation of classical unitals on 28 points

Using the answer of Taras Banakh, I have implemented an interactive example using HTML and Javascript. It shows all lines of the unital with random colors. Every line is clickable. After clicking on a …
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