Author/Authors :
-، - نويسنده Departamento de Matem?ticas, Universidad de Oviedo. Avenida Calvo Sotelo s/n, 33007 Oviedo, Spain. Grau, J. M. , -، - نويسنده Centro Universitario de la Defensa de Zaragoza. Carretera de Huesca s/n, 50090 Zaragoza, Spain. Oller-Marcén, A. , -، - نويسنده Departamento de Matem?ticas, Universidad de Oviedo. Avenida Calvo Sotelo s/n, 33007 Oviedo, Spain. Tasis, C.
Abstract :
In a recent paper C. Miguel proved that the diameter of the commuting graph of the matrix ring $mathrm{M}_n(mathbb{R})$ is equal to $4$ if either $n=3$ or $ngeq5$. But the case $n=4$ remained open, since the diameter could be $4$ or $5$. In this work we close the problem showing that also in this case the diameter is $4$.
