doi:10.1016/j.jfa.2026.111492engOliva-Maza, J.Tomilov, Y.On similarity to contraction semigroups and tensor products, IART-2026-148821In the context of finite tensor products of Hilbert spaces, we prove that similarity of a tensor product of operator semigroups to a contraction semigroup is equivalent to the corresponding similarity for each factor, after an appropriate rescaling. A similar result holds with contractivity replaced by quasi-contractivity. This splitting phenomenon allows us to construct new and, in a sense, the strongest possible examples of C_0-semigroups not similar to contractions, thus completing an important chapter of the theory. We also address the discrete setting and relate it to our results.2026http://zaguan.unizar.es/record/17029210.1016/j.jfa.2026.111492http://zaguan.unizar.es/record/170292oai:zaguan.unizar.es:170292info:eu-repo/grantAgreement/ES/AEI/AEI PID2022-137294NB-I00info:eu-repo/grantAgreement/ES/DGA/E48-23RJOURNAL OF FUNCTIONAL ANALYSIS (2026), 111492 [37 pp.]All rights reservedhttp://www.europeana.eu/rights/rr-f/info:eu-repo/semantics/closedAccess