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Galois geometry, finite projective and affine spaces, polar spaces, partial geometries, generalized polygons, near polygons, and other finite incidence geometries.

4 votes
1 answer
180 views

Is there a unique Baer subplane in a finite Desarguesian projective plane?

An order-$m$ subplane of a finite projective plane of order $n$ is called a Baer subplane if $n=m^2$. It is known that the projective plane $PG(2,q)$ is a Baer subplane of the Desarguesian projectiv …
LeechLattice's user avatar
  • 9,501
11 votes
1 answer
264 views

Does every $C_4$-free bipartite graph lies in some finite projective plane?

A projective plane $Π$ is a 3-tuple $(P,L,I)$ where $P$ and $L$ are sets, and $I$ is a relation between $P$ and $L$, such that: For every two elements $p_1$, $p_2\in P$, there exists a unique eleme …
LeechLattice's user avatar
  • 9,501
9 votes
1 answer
398 views

Are bipartite Moore graphs Hamiltonian?

This is motivated by a computer-generated conjecture that bipartite distance-regular graphs are hamiltonian. I decided to check the case of Moore graphs first. The cycles and complete bipartite graphs …
LeechLattice's user avatar
  • 9,501
16 votes
1 answer
392 views

Geometric interpretation of the exceptional isomorphism $PSp(4,3)=PSU(4,2^2)$

It is well-known that there is an isomorphism between $PSp(4,3)$ (the symplectic group of dimension $4$ over $\mathbb F_3$) and $PSU(4,2^2)$ (the unitary group defined by $4\times4$ unitary matrices …
LeechLattice's user avatar
  • 9,501