A. C. Cem Say, Abuzer Yakaryılmaz, "Computation with multiple CTCs of fixed length and width," Natural Computing, Vol. 11, No. 4, pp. 579-594, 2012. doi: 10.1007/s11047-012-9337-6, Theorem 10: The expression for the infinite sum is wrong and the sum should equal 4, which causes the bound for the expected runtime to be higher (but still a constant).
A. C. Cem Say, Abuzer Yakaryılmaz, "Finite state verifiers with constant randomness," Logical Methods in Computer Science, Vol. 10(3:6)2014, pp. 1-17: The proof of Theorem 3.7 is wrong, and we do not know how to prove that statement. Fortunately, we have found a correct proof of Fact 3.6, which is Theorem 6 in https://arxiv.org/pdf/2306.09542
Fırat Kıyak, A. C. Cem Say, “Energy complexity of regular languages,” Theoretical Computer Science, Vol. 982, January 2024, 114291 https://doi.org/10.1016/j.tcs.2023.114291: Inner product notation is consistently wrong throughout Lemma 7. For any s1, s2, replace "<s1>s2" with "<s1|s2>".
A. C. Cem Say, M. Utkan Gezer, “Unconditional Proofs of Quantumness Between Small-Space Machines,” Quantum Information & Computation, Vol. 25, March 2025, 36-56: Change "c" to "s" on the last line of page 45.
A. C. Cem Say, "Time hierarchies for sublogarithmic-space quantum computation" Theoretical Computer Science Vol. 1061, January 2026, 115639: The runtime analysis in the proofs of Theorem 6 and Theorem 11 is flawed. See Section 6 of https://arxiv.org/pdf/2601.16695 to see how one can fix those proofs so that all results stand without the need to reword any theorem statements.
Ahmet Celal Cem Say, "Short and useful quantum proofs for sublogarithmic-space verifiers", LNCS Vol. 16364, Unconventional Computation and Natural Computation (22nd International Conference, UCNC 2025, Nice, France, September 1–5, 2025, Proceedings) pp. 88-99, 2026: Change "=" to "\in" in Expression (2).