This problem was posed in
L. Elliott, J. Jonusas, Z. Mesyan, J. D. Mitchell, M. Morayne and Y. Peresse: "Automatic continuity, unique Polish topologies, and Zariski topologies on monoids and clones", Trans. Amer. Math. Soc. 376 (2023), 8023--8093.
A negative answer is published in
S. Bardyla, L. Elliott, J. D. Mitchell and Y. Péresse: "Topological embeddings into transformation monoids", Forum Mathematicum (2024), published online.
These problems were posed by Tzannes in
E. Pearl: "Problems from Topology Proceedings", Topology Atlas, Toronto, 2003.
The affirmative ZFC answer to both problems without properties in parentheses is published in
S. Bardyla, A. Osipov: "On regular \kappa-bounded spaces admitting only constant continuous mappings into T_1 spaces of pseudo-character \leq \kappa", Act. Math. Hung. 163 (2021), 323--333.
Consistent solutions of these problems with additional nice properties can be found in
S. Bardyla, L. Zdomskyy: "On regular separable countably compact R -rigid spaces", Israel Journal of Mathematics 255 (2023), 783--810.
The first problem was originally posed by Gerlits and Nagy in
J. Gerlits, Zs. Nagy: "Some properties of Cp(X), I", Topology Appl. 14 (1982), 151--161.
Later it was reposed by Orenshtein and Tsaban in
T. Orenshtein, B. Tsaban: "Pointwise convergence of partial functions: The Gerlits–Nagy Problem", Advances in Mathematics 232 (2013), 311--326.
The second problem was posed by Sakai in
M. Sakai: "Special subsets of reals characterizing local properties of function spaces", in: Koˇcinac L. (eds), Selection Principles and Covering Properties in Topology, quaderni di matematica 18, Caserta, 2006, 196--225.
Affirmative consistent solutions to both problems are published in
S. Bardyla, J. Šupina, L. Zdomskyy: "Ideal approach to convergence functional spaces", Trans. Amer. Math. Soc. 376 (2023), 8495--8528.
This problem was posed by Arhangelskii and Choban in
A. Arhangelskii, M. Choban: "Completeness type properties of semitopological groups, and the theorems of Montgomery and Ellis", Topology Proceedings 37 (2011), 33--60.
The affirmative answer is published in
S. Bardyla, O. Gutik, A. Ravsky: "H-closed quasitopological groups", Topology Appl. 217 (2017), 51--58.
These problems were posed by Mooney in
D. Mooney: "Spaces with unique Hausdorff extensions", Topology Appl. 61 (1995), 241–256.
The affirmative answer to both problems is published in
S. Bardyla, J. Supina, L. Zdomskyy: "Open filters and measurable cardinals", preprint, arXiv:2301.08704.
This problem was posed by Mesyan, Mitchell, Morayne and Péresse in
Z. Mesyan, J. D. Mitchell, M. Morayne, and Y. H. Péresse: "Topological graph inverse semigroups", Topology Appl. 208 (2016), 106--126.
The characterization of graph inverse semigroups which admit only the discrete semigroup topology is published in
S. Bardyla: "On locally compact topological graph inverse semigroups", Topology Appl. 267 (2019), 106873.
This problem was posed by Koch in
R. Koch: "On monothetic semigroups", Proc. Amer. Math. Soc. 8 (1957), 397--401.
It took more that 50 years until Zelenyuk constructed a counterexample to the above problem. We proved that a Hausdorff locally compact monothetic topological monoid S is a compact topological group if and only if S can be embedded into a Hausdorff quasitopological group. This result can be found in
T. Banakh, S. Bardyla, I. Guran, O. Gutik, A. Ravsky: "Positive answers to Koch's problem in special cases", Topol. Alg. Appl. 8:1 (2020), 76--87.
This problem was posed by Ravsky in 2010 in the first version of the following paper
T. Banakh, A. Ravsky: "On feebly compact paratopological groups", Topology Appl. 284 (2020), 107363.
In 2018 Garcia-Ferreira and Tomita under CH provided a counterexample to the above problem. Assuming MA we constructed a Boolean countably compact topological group whose square is not countably pracompact. This example can be found in
S. Bardyla, A. Ravsky, L. Zdomskyy: "A countably compact topological group with the non-countably pracompact square", Topology Appl. 279 (2020), 107251.
This problem was posed by Banakh, Dimitrova, and Gutik in
T. Banakh, S. Dimitrova, O. Gutik: "Embedding the bicyclic semigroup into countably compact topological semigroups", Topology Appl. 157(18) (2010), 2803--2814.
The affirmative answer is published in
S. Bardyla, A. Ravsky: "Closed subsets of compact-like topological spaces", Applied General Topology, 21:2 (2020), 201--214.
This problem was posed by Stepp in
J.W. Stepp: "Algebraic maximal semilattices", Pacific J. Math. 58:1 (1975), 243--248.
The affirmative answer is published in
S. Bardyla, O. Gutik: "On H-complete topological semilattices", Mat. Stud. 38:2 (2012), 118--123.
This problem was posed by Yokoyama in
T. Yokoyama: "On the relation between completeness and H-closedness of pospaces without infinite antichains", Alg. Discr. Math. 15:2 (2013), 287--294.
The affirmative answer is published in
T. Banakh, S. Bardyla: "Completeness and absolute H-closedness of topological semilattices", Topology Appl. 260 (2019) 189--202.