文摘
Let class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0024379514005473&_mathId=si1.gif&_user=111111111&_pii=S0024379514005473&_rdoc=1&_issn=00243795&md5=457faa46d768e51bbde8a1444098dfaf" title="Click to view the MathML source">Dclass="mathContainer hidden">class="mathCode"> be any division ring and class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0024379514005473&_mathId=si2.gif&_user=111111111&_pii=S0024379514005473&_rdoc=1&_issn=00243795&md5=f2a512a157ac20eb5289a73a51842aa2" title="Click to view the MathML source">p,qclass="mathContainer hidden">class="mathCode"> positive integers. The optimal version of Hua's fundamental theorem of geometry of square matrices has been known in all dimensions but the class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0024379514005473&_mathId=si104.gif&_user=111111111&_pii=S0024379514005473&_rdoc=1&_issn=00243795&md5=32446c1890411a3337983c02f2dbb2bf" title="Click to view the MathML source">2×2class="mathContainer hidden">class="mathCode"> case. We solve the remaining case by describing the general form of adjacency preserving maps class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0024379514005473&_mathId=si156.gif&_user=111111111&_pii=S0024379514005473&_rdoc=1&_issn=00243795&md5=2ffe49fc873ec89ced93cb2d9f309a12" title="Click to view the MathML source">ϕ:M2(D)→Mp×q(D)class="mathContainer hidden">class="mathCode">. One of the main tools is a slight modification of known non-surjective versions of the fundamental theorem of affine geometry.