Acta Polytechnica https://doi.org/10.14311/AP.2025.65.0500 Acta Polytechnica 65(5):500–514, 2025 © 2025 The Author(s). Licensed under a CC-BY 4.0 licence Published by the Czech Technical University in Prague THE SCIENTIFIC LEGACY OF MILOSLAV HAVLÍČEK Rutwig Campoamor-Stursberg Universidad Complutense de Madrid, Instituto de Matemática Interdisciplinar, Plaza de Ciencias 3, E-28040 Madrid, Spain correspondence: rutwig@ucm.es Abstract. We review the main research achievements of Miloslav Havĺıček in algebraic methods in Quantum Theory, his extensive work on realisations of Lie algebras and superalgebras and their representation theory, quantum groups and differential equations. Keywords: Realisations of Lie algebras, Lie gradings, quantum groups, differential equations, quantum mechanics. 1. Introduction. academic and professional trajectory It is certainly not an easy task to condense the life and work of Miloslav Havĺıček (1938–2024) to few pages, nor is to emphasise his influence at the Faculty of Nuclear Sciences and Physical Engineering of the Czech Technical University in Prague and the Faculty of Mathematics and Physics at Charles University, where he has, for many decades, trained dozens of leading specialists, firmly contributing to the solid reputation of these institutions as centres of excel- lence in mathematical physics. It is our purpose to recall some of the main achievements of Miloslav in algebraic methods in quantum theory, emphasising various problems that have determined and motivated important research topics that are still of current in- terest and application. Havĺıček’s academic and professional trajectory has been marked for many years by the difficulties and mistrust of the government and university officials, plenty of bitter experiences and privations, as well as some endearing anecdotes, like the confiscation of his doctoral dissertation by Soviet custom officers due to the extremely suspicious name of “Li” in the ti- tle (with Li being the Russian form of Sophus Lie’s surname, written and spelled as the Chinese surname Li), in a time where the confrontation of the People’s Republic of China and the Soviet Union was at its highest point. This arbitrary intervention did, how- ever, not prevent Miloslav from demonstrating his exceptional scientific ability during the examination. Despite all obstacles, Miloslav never lost faith that education should be devoid of any political interven- tionism and favoritism, and based solely on personal qualifications. These were the precepts he maintained while being the Dean of the Faculty, as well as a mem- ber of the various scientific associations to which he belonged, such as the International Association of Mathematical Physics (IAMP) or the Union of Czech Mathematicians and Physicists (JČMF). Miloslav also served as Scientific Council Member of the ČVUT for the terms 1990–1994 and 2000–2006, of the Faculty of Mathematics and Physics at Charles University for the terms 1999–2002 and 2002–2005, and of the Institute of Informatics of the Czech Academy of Sci- ences (AV ČR) between 2001 and 2005, also acting as Vice-Chair of the Academic Assessment Board at this institution between 1993 and 1999. His efforts, devo- tion, and altruistic dedication were finally recognised officially in 1998, when Miloslav was awarded with the Prize of the Minister of Education (1st degree). Rigour and scientific excellence were also the guiding principles in the foundation of the Doppler Institute in 1993, where Miloslav’s efforts, among other colleagues, managed to finally found a research institute that crystallised the high scientific level of the seminars they had led for many years. To offer a glimpse into the captivating and hum- ble personality of Miloslav, who always avoided the spotlight and the pursuit of fame, let us recall his response when asked about his experiences as Dean of the faculty in the terms 1990–1994 and 2000–2006, Havĺıček answered, “The faculty actually runs itself”, As a teacher, he was well-known to be strict and demanding, but impartial and fair. He was perfectly aware that, in order to create a really selective, repre- sentative, and competitive scientific school, rigor was the first commandment. In his own words, on the occasion of the 50th anniversary of FJFI, he stated: “We don’t pretend to be an easy school, but for the effort, we offer individual attention, quick involvement in faculty research teams and an emphasis on our students’ own creative work. These students are then able to establish themselves at the top workplaces in the Czech Republic and abroad”. At the same occasion, and concerning the social relevance of the rôle that higher education had to play in the devel- opment of the country, deprived from any political fanatism, he declared that “You may be surprised, but applied natural sciences penetrate into virtually all components of human activities, from theoretical physics and research into the construction of matter through medicine, energy, environmental protection, 500 https://doi.org/10.14311/AP.2025.65.0500 https://creativecommons.org/licenses/by/4.0/ https://www.cvut.cz/en vol. 65 no. 5/2025 The scientific legacy of Miloslav Havĺıček monument research, food science and many others. We have a good historical basis, excellent scientific and technological level and capable people, our stu- dents are among the elite of the Czech intelligentsia – what other field can say this?” Despite the fact that Havĺıček was by no means con- sidered a political activist “by the book”, a fact which would cause difficulties for him until 1989, but without bending either his spirit or convictions, he was allowed to defend the DrSc. Dissertation in the Laboratory of Theoretical Physics at JINR in Dubna, showing that his work had truly impressed the authorities there, as well as in Prague. In this context, it is not surprising, that, despite his political convictions, Miloslav was awarded the First Prize for Theoretical Physics at the JINR in Dubna in 1985, jointly with Jǐŕı Blank, Jaroslav Dittrich, Pavel Exner and Genrikh Ivanovich Kolerov, in recognition of their important work on operator methods in quantum physics, with Miloslav’s contributions to realisations of Lie algebras being part of the awarded collection of papers. The Disserta- tion, dealing with canonical realisations of classical Lie algebras [1], was brilliantly defended in Dubna in 1979. The opponents of the thesis were three highly reputed and influential scientists, Vladas Vladovich Vanagas from the Lithuanian Academy of Sciences, Alexander Aleksandrovich Kirillov from the Moscow State University, and Yakov Abramovich Smorodinsky from JINR, all of them world leading experts in group theoretical methods in physics. The wide range of Miloslav’s scientific interests is well reflected by enumerating his (main) collaborators, also illustrating that, despite the disparity of specific subjects, the nucleus was always related to his passion for group theory. Among the collaborators whose main affiliation belongs to an establishment in Prague1, we mention (given in alphabetical order): Martin Ba- covský, Miroslav Bednář, Jǐŕı Blank, Čestmı́r Burd́ık, Goce Chadzitaskos, Pavel Exner, Jǐŕı Hořeǰśı, Jan Kotrbatý, Ondřej Navrátil, Edita Pelantová, Severin Pošta, Jǐŕı Tolar, Ivan Úlehla, and Jan Votruba. Besides them, Miloslav actively worked with Jǐŕı Patera and Pavel Winternitz from the Centre de Recherches Mathématiques in Montréal (Canada), Anatoly Ul’yanovich Klimyk from the Institute of The- oretical Physics in Kiev (Ukraine), Raisa Moiseevna Asherova, Yuri Fedorovich Smirnov, and Valeriy Niko- laevich Tolstoy from the Skobeltsyn Institute of Nu- clear Physics at the Lomonosov Moscow State Uni- versity, as well as Wolfgang Lassner from the Leipzig University (at the times of the German Democratic Republic, Karl-Marx Universität) and Patrick J. Moy- lan from the University of Pennsylvania in Abington (USA). These names by no means exhaust the collaboration of Havĺıček with other scholars. He was always willing to help and counsel, and has motivated many people 1Or whose principal affiliation was related to Prague when the publications appeared. to pursue their researches and to clear up doubts or apparently unsurmountable difficulties. Anecdotally, I remember Miloslav’s astonishing ability to find rare or untraceable references, like a series of articles in hard-to-find Soviet journals that I had, after several desperate attempts in many places, asked him for during a visit back in 2006, and that he managed to procure within a few days. 2. The infinite dimensional Lie algebra A(P, S) The topic of Miloslav’s CSc. thesis [2], defended in December 1968, benefitted from a productive collabo- ration (and lifetime friendship) with Jan Votruba, son of the eminent physicist and pioneer of modern theoret- ical physics in Czechoslovakia, Václav Votruba, with both Votrubas being undoubtedly very influential in the formation of Miloslav’s scientific interests. These works already show the deep interest that Miloslav took in combining the algebraic/geometric formalism with real physical phenomena and modelization, a sub- ject that had begun to be considered systematically in the mid 1960’s (see e.g. [3]), based on the pioneering work by Giulio Racah in the 1950s [4]. From these initial articles referring to this subject, that we enu- merate below, many new ideas and problems emerged, that would constitute one of the main activity areas of Miloslav for the rest of his scientific life: • M. Havĺıček, J. Votruba. On the physical rep- resentations of an infinite-dimensional lie algebra. Czechoslovak Journal of Physics B 16(8):631–642, 1966. https://doi.org/10.1007/BF01689564 • M. Havĺıček, J. Votruba. The tensor product of one- particle representations of an infinite-dimensional Lie algebra. Czechoslovak Journal of Physics B 17(10):809–821, 1967. https://doi.org/10.1007/ BF01691631 • J. Votruba, M. Havĺıček. On the representation of infinite-dimensional Lie algebra A(P, S). In High Energy Physics and Theory of Elementary Particles, pp. 330–335. International School of Theoretical Physics, Naukova Dumka, Kyiv, 1966 • J. Votruba, M. Havĺıček. Mass formulas for me- son nonets. Czechoslovak Journal of Physics B 19(6):721–729, 1969. https://doi.org/10.1007/ BF01697128 • M. Havĺıček. Representations of an algebra of the Gell-Mann-Dashen type. Communications in Mathematical Physics 13(1):73–80, 1969. https: //doi.org/10.1007/BF01645272 • M. Havĺıček. About one class of representations of the Lie algebra. Communications in Mathematical Physics 20(2):130–142, 1971. https://doi.org/ 10.1007/BF01646532 These papers extended earlier work by Formánek on the nontrivial coupling A(P, S) of internal and space- 501 https://doi.org/10.1007/BF01689564 https://doi.org/10.1007/BF01691631 https://doi.org/10.1007/BF01691631 https://doi.org/10.1007/BF01697128 https://doi.org/10.1007/BF01697128 https://doi.org/10.1007/BF01645272 https://doi.org/10.1007/BF01645272 https://doi.org/10.1007/BF01646532 https://doi.org/10.1007/BF01646532 Rutwig Campoamor-Stursberg Acta Polytechnica time symmetries [11, 12], combining the Poincaré algebra with SU(2) in new representations. Specif- ically, the Lie algebra A(P, SU(2)) proposed in this extension has the basis: [Lµν , Lρλ] = i (gµρLνλ − gνρLµλ +gµλLρν − gνλLρµ), [Pµ, Lρλ] = i (gρµPν − gνµPρ), [Pµ, Pν ] = 0,[ Pµ, T (1) ρ1···ρm ] = − αiT (2) µρ1···ρm ,[ Pµ, T (2) ρ1···ρm ] = αiT (1) µρ1···ρm ,[ Pµ, T (3) ρ1···ρm ] = 0,[ Lµν , T (i) ρ1···ρm ] = i m∑ j=1 ( gνρj T (i) ρ1···ρj−1µ···ρm −gµρj T (i) ρ1···ρj−1ν···ρm ) ,[ T (i) ρ1···ρm , T (k) ρ1···ρm ] = iϵikℓT (ℓ) µ1···µnρ1···ρm , where Pµ, Lνρ, µ, ν, ρ = 0 . . . 3; i, k, ℓ = 1, 2, 3. It should be noted that structures of this type were later obtained and considered independently in the context of Kac–Moody algebras, their generalizations and extensions, as well as other infinite-dimensional algebraic structures. The representations of this algebra, specifically the irreducible Hermitean representations (IHR in short), also considering the special case of one isomultiplet, were constructed and studied in detail. In addition, the mass formulae (depending on the third compo- nent of the isotopic spin) and the spin-spectrum were analysed, hence extending considerably an earlier sym- metry scheme for particles proposed by Votruba and Havĺıček [13]. In connection with the classification of one-particle states into S-multiplets (i.e. one-particle representations), the tensor product of two such rep- resentations and the corresponding reduction problem were considered. Here, an interesting phenomenon emerged: while in the case of irreducible Hermitean representations with a single value of TiTi, the anal- ogy of SU(2) and A(P2, SU(2)) was almost complete (from the perspective of the pure SU(2) classification), for the tensor products the behaviour showed impor- tant differences, and a new series of IHR appeared, that determined an action on Hilbert spaces decom- posable as direct sums of a (finite) discrete number of irreducible spaces associated to the Poincaré algebra, leading to non-linear mass formulae. In the context of infinite dimensional algebras, and motivated by a problem of Dashen and Gell-Mann arising in the application of current algebras to ele- mentary particle physics, Havĺıček proposed an alter- native construction, starting from centreless Lie alge- bras of finite dimension, and studying a certain class (called F -representations) of this infinite-dimensional object in a Hilbert space, considering those operators represented linearly and possessing a common dense domain in the Hilbert space, subjected to certain lin- ear constraints. In a more general frame, operator representations of pairs (g′, g) in Hilbert spaces were studied in connection with the integrability property with respect to a distinguished subalgebra, under cer- tain conditions. A notion of irreducibility for such representations was introduced, for which a version of the Schur lemma was obtained; specifically, that a symmetric operator that commutes with the repre- sentation and leaves a dense space D in the domain invariant is necessarily a scalar. 3. Realisations of Lie algebras During his stay at the JINR in Dubna (1974–1977), Miloslav met Wolfgang Lassner, a physicist from the Karl Marx Universität Leipzig (GDR), who had writ- ten his CSc. thesis on the connected subgroups of the Poincaré group [14], being simultaneously an expert in symbolic computation and algorithm programming2. Sharing common interests, jointly with Pavel Exner, with whom Miloslav had already studied some aspects of canonical matrix realisations3, they combined their expertise for an ambitious problem, still offering new challenges even today: the realisations of Lie algebras by creation and annihilation operators. The problem of realisations of Lie algebras arises naturally in many physical applications, such as solu- tions of nuclear models, collective motions, many-body problems, and dynamical algebras in the context of particle physics, where the generators are identified with differential operators with respect to quantum- mechanical variables qi and pi. Though several results were available in the mid 1970s, no systematic and profound analysis of the problem had been yet consid- ered. The subject of Havĺıček’s DrSc. dissertation was exactly this problem: a methodic approach to classify and construct realisations of the classical Lie algebras in the Weyl algebra and some of its extensions. These works, carried out between 1974 and 1977 [1], also considered the problem of computing the eigenvalues of the corresponding (generalised) Casimir operators on these realisations, expanding on work by other authors on the eigenvalue spectra of Casimir opera- tors on irreducible representations (see e.g. [16] and references therein)4. This work significantly extended the known knowledge about the properties of canoni- cal realisations of important families of classical Lie algebras, and served as a natural basis for generali- sations to other types of Lie algebras that have been widely considered in the literature. The dissertation 2Actually, Lassner presented his Dissertation B on a topic also deeply related to realisations of Lie algebras [15]. 3One of the first publications on the subject was the o(m, n) case, presented at an international symposium on high energy physics and elementary particles held in Varna (Bulgaria) in 1974. 4The length of the thesis is 112 pages, with 111 references that comprised most of the work on realisations published until 1979. 502 vol. 65 no. 5/2025 The scientific legacy of Miloslav Havĺıček comprises the material of the main articles concerning the Lie algebra case and appeared in these years5: • M. Havĺıček, P. Exner. On the minimal canonical realizations of the Lie algebra Oc(n). Annales de l’Institut Henri Poincaré Section A 23(4):313–333, 1975 • M. Havĺıček, P. Exner. Matrix canonical realizations of the Lie algebra o(m, n). I. Basic formulae and classification. Annales de l’Institut Henri Poincaré Section A 23(4):335–347, 1975 • M. Havliček, W. Lassner. Canonical realizations of the Lie algebras gl(n,R) and sl(n,R). I. Formu- lae and classification. Reports on Mathematical Physics 8(3):391–399, 1975. https://doi.org/10. 1016/0034-4877(75)90081-6 • M. Havliĉek, W. Lassner. Canonical realiza- tions of the Lie algebras gl(n,R) and sl(n,R). II. Casimir operators. Reports on Mathematical Physics 9(2):177–185, 1976. https://doi.org/10. 1016/0034-4877(76)90053-7 • P. Exner, M. Havĺıček, W. Lassner. Canonical realizations of classical Lie algebras. Czechoslo- vak Journal of Physics B 26(11):1213–1228, 1976. https://doi.org/10.1007/BF01589833 • M. Havĺıček, W. Lassner. Canonical realizations of the Lie algebra sp(2n,R). International Journal of Theoretical Physics 15(11):867–876, 1976. https: //doi.org/10.1007/BF01807449 • M. Havĺıček, W. Lassner. On the “near to minimal” canonical realizations of the Lie alge- bra Cn. International Journal of Theoretical Physics 15(11):877–884, 1976. https://doi.org/10.1007/ BF01807450 • M. Havĺıček, W. Lassner. Matrix canonical re- alizations of the Lie algebra u(p, q). Reports on Mathematical Physics 12(1):1–8, 1977. https:// doi.org/10.1016/0034-4877(77)90040-4 • M. Havĺıček, P. Exner. Matrix canonical realizations of the Lie algebra o(m, n). II. Casimir operators. Czechoslovak Journal of Physics B 28(9):949–962, 1978. https://doi.org/10.1007/BF01596007 • P. Exner, M. Havlicek, W. Lassner. Boson repre- sentations of classical Lie algebras. In International Conference on Operator Algebras, Ideals and their Applications in Theoretical Physics, pp. 277–278. 1977 • Č. Burd́ık, M. Havĺıček. Boson realizations of semi- simple Lie algebras. In P. Winternitz, J. Harnad, C. S. Lam, J. Patera (eds.), Symmetry in Physics, vol. 34 of CRM Proceedings & Lecture Notes, pp. 87–98. American Mathematical Society, 2004 5The corresponding preprints at JINR, as far as they could be found, are: E2-8089, E2-8533, E2-8700, E2-8646, E2-8842, E2-9160, E2-9617, E2-9161. The three main aspects of the generalised approach and classification of realisations can be summarised as follows: (a) New recursion formulae determining realisations with special properties for all types of classical com- plex Lie algebras and their consecuenques. (b) Analogous recursion formulae for the following types of (noncompact) real forms: sl(nR), su(p, q), o(p, q), sp(2n,R). (c) Comparison with minimal realisations and reali- sations of Gel’fand–Kirillov type [28, 29]. The embeddings of the classical series An, Bn, Cn, and Dn in the Weyl algebra W2N(d) were revisited and expanded, taking into account the Schurean property, and the number of realisation parameters determined for each class of realisations. Of special interest are the minimal and maximal number values such that the resulting realisations are nontrivial, with special emphasis on the Gel’fand–Kirillov conjecture. Within the range N(d) = 1, · · · , n, the following numbers of pairs were found for the classical series: An Bn Cn Dn N(d) (2n+1−d)d 2 d(2n − d) d(2n − d) d(2n − d − 1) The problem of realisations in the quotient division ring of the Weyl algebras was also satisfactorily com- pleted, and by denoting n0 the minimal number of canonical pairs leading to nontrivial realisations, and nk the maximal integer such that all realisations in W2(n0+nk) are Schurean, the following values were computed: An Bn(n > 1) Cn Dn(n > 2) n0 n 2n − 2 n 2n − 3 nk 0 1 n − 1 1 The nucleus of the work, however, concerns studying the set of skew-Hermitean and Schurean6 realisations for the real Lie algebras in (b). To this extent, the usual approach is enriched by considering further suit- able embeddings of the Weyl algebra into more general algebraic structures, that allow for a greater gener- ality of the operators realizing the Lie algebras, and avoiding the degeneracy concerning the number of re- sulting independent Casimir operators. However, the removal of degeneracy does not necessarily imply the preservation of the Schurean property, and obtaining the criteria and explicit construction procedures for non-degenerate Schurean realisations was posed. In the first papers with Pavel Exner on this topic, the ex- istence problem was positively answered for the class o(n, m) of pseudo-orthogonal Lie algebras by means of canonical matrix realisations, i.e. by realisations in the matrix Weyl algebra W2n,M = W2n ⊗ Mat(M,C), also considering the case of minimal canonical realisa- tions for the complexification o(n,C). The analogous 6In other words, such that the Casimir operators are realised by scalar multiples of the identity. 503 https://doi.org/10.1016/0034-4877(75)90081-6 https://doi.org/10.1016/0034-4877(75)90081-6 https://doi.org/10.1016/0034-4877(76)90053-7 https://doi.org/10.1016/0034-4877(76)90053-7 https://doi.org/10.1007/BF01589833 https://doi.org/10.1007/BF01807449 https://doi.org/10.1007/BF01807449 https://doi.org/10.1007/BF01807450 https://doi.org/10.1007/BF01807450 https://doi.org/10.1016/0034-4877(77)90040-4 https://doi.org/10.1016/0034-4877(77)90040-4 https://doi.org/10.1007/BF01596007 Rutwig Campoamor-Stursberg Acta Polytechnica construction for the pseudo-unitary group u(r, s) was written in collaboration with Wolfgang Lassner. Also in collaboration with Lassner, Miloslav con- sidered the problem for the canonical embedding gl(n,R) ⊃ sl(n,R), but focusing on embeddings into a Weyl algebra with an adequate number of canon- ical pairs. A family of (d + 1)-parametric classes with d ≤ n − 1 in the Weyl algebra in dependence of N(d) = (2n−d−1)d 2 pairs was obtained, having the following salient properties: (1.) The realisations are skew-Hermitean. (2.) Casimir operators are realised as scalars (Schurean). (3.) Non-equivalence of realisations is determined up to endomorphisms in the Weyl algebra. (4.) The obtained realisations in the (d + 1)-class admit Casimir operators whose eigenvalues can be expressed polynomially in terms of (d+1) symmetric functions of the parameters. The corresponding realisations for the special Lie al- gebra sl(n,R) were recovered obtained by restriction, still preserving the above-mentioned structural prop- erties. In this context, it is worthy to recall how canonical realisations Fµν of gl(n − 1,R) in W2m with commutation relations: [Fµν , Fρσ] = δνρFρσ − δµσFρν were expanded to an α-parameterised family of re- alisations of gl(n,R) in W2n−2+2m, defining the new operators as: Eµν = qµpν + Fµν + 1 2δµν1, Enµ = − pµ, Eµn = qµ (∑ ν qνpν + n 2 − iα ) + ∑ ν qνFµν , Enn = − ∑ ν qνpν − ( n − 1 2 − iα ) 1, α ∈ C. (1) The real importance of these formulae, which have implications far beyond of what was explicitly stated in these papers, was only recognised much later in the context of quasi-exactly solvable models (see e.g. [30, 31]). The symplectic algebra, appearing naturally in the context of canonical transformations as a subgroup of the corresponding inhomogeneous group, as well as in other physical contexts such as dynamical alge- bras in n-dimensional harmonic oscillators, prior to their application in nuclear collective motions [32, 33], was the last class to be considered to complete the discussion on the classical series. Here, it was ob- served that certain one-parameter sets of realisations of sp(2n,R) could be obtained by means of the pre- viously studied one-parameter set of minimal realisa- tions for gl(2n,R), leading to an extremely relevant formula for constructing canonical realisations of arbi- trary finite-dimensional Lie algebras. Several of these realisations were later used for studying the metaplec- tic group; specifically, the quantisation schemes invari- ant under metaplectic transformations, of relevance in the context of wave optics with aberration [34]. Other applications of these results were found in the algo- rithmic construction of invariants of inhomogeneous Lie algebras obtained by contraction of symplectic groups [35]. Some of the generic results concerning the realisa- tions of the mentioned classes of Lie algebras can be summarised in table form as follows: gl(n,R) u(p, q) o(m, n) sp(2n,R) Alg. W2N(d) W N(d) 2N(d),M(d) W2N(d),M(d) W2N(d) d 1, · · · , n − 1 1, · · · , 2q − δpq 1, · · · , n 1, · · · , n N(d) (2n−d−1)d 2 (2p+2q−d−1)d 2 d(m + n − d − 1) d(2n − d) M(d) − ξ0 ξ0 − where W N(d) 2N(d),M(d) denotes a certain localisation of the Weyl algebra (i.e. rational functions of canonical pairs) and the precise value of ξ0 depends on the value of d as well as those of (p, q) and (m, n). As commented before, the Equation (1) contains much more information than suspected, although this fact is not easily recognisable. Actually, to a certain extent, it seems natural to extrapolate the given re- alisations to the combined case of differential and matrix representations, hence leading naturally to the notion of mixed realisations or matrix differential op- erators. This was actually the ansatz considered by Yuri F. Smirnov and Alexander V. Turbiner in [30], where, starting from the usual vector field realisation ʵν = xµ ∂ ∂xν and a representation Mρσ by (unspec- ified) operators that commute with the realisation, mixed realisations of gl(n + 1,R) were obtained with a striking similarity to Equation (1)7: Eµν = ʵν + Mµν , Enµ = ∂ ∂xµ , Eµn = xµ ( k − ∑ ν xν ∂ ∂xν ) − ∑ ν xνFµν , Enn = k − ∑ ν xν ∂ ∂xν , k ∈ R. (2) To this day, it remains unknown to which extent Miloslav had already considered the possibility of mixed realisations, as no explicit hint could be found in either the Dubna preprints or the published versions. However, it was clear to many people, among them to Israel Moiseevich Gel’fand, that Miloslav knew more than he had shared; a suspicion that has been later confirmed through personal conversations with him8. Humble as he was, Miloslav never claimed any 7Up to an inessential change of the sign in the Eµn genera- tors. 8See the introduction of [30] for a first-hand account. 504 vol. 65 no. 5/2025 The scientific legacy of Miloslav Havĺıček credit for the obtainment of the algebra gl(n+1,R) of matrix differential operators, though strong hints in that direction that can be extracted after a detailed and quite laborious analysis of the papers lead us to suspect that this construction was to a certain extent familiar to him. 4. Realisations of Lie superalgebras As a natural extension of the work already achieved for Lie algebras, relevant physical applications led Miloslav and collaborators to consider the analogous problem for the case of Lie superalgebras [36], also combined with aspects of the general representation theory, where several important structural results could be obtained. Among these works, from which some of the most relevant are listed below, the first were written in collaboration with Lassner and Exner, where they extended the techniques that they had de- veloped for the case of Lie algebras, leading to a series of papers with Jǐŕı Blank (1939–1990) as the main collaborator: • J. Blank, M. Havĺıček, M. Bednář, W. Lass- ner. Canonical representations of the Lie su- peralgebra osp(1, 4). Czechoslovak Journal of Physics B 31(11):1286–1301, 1981. https://doi. org/10.1007/BF01603588 • J. Blank, M. Havĺıček, P. Exner, W. Lassner. Boson- fermion representations of Lie superalgebras: The example of osp(1, 2). Journal of Mathematical Physics 23(3):350–353, 1982. https://doi.org/ 10.1063/1.525373 • J. Blank, M. Havĺıček. Irreducible *-representations of Lie superalgebras B(0, n) with finite-degenerated vacuum. General considerations. Tech. Rep. E2-85- 112, JINR Dubna, 1985 • J. Blank, M. Havĺıček. Irreducible *-representations of Lie superalgebras B(0, n) with finite-degenerated vacuum. Results for B(0, 1). Tech. Rep. E2-85-160, JINR Dubna, 1985 • Y. F. Smirnov, V. N. Tolstoi, A. A. Sakharuk, et al. The Dyson type boson realizations for representa- tions of the semisimple Lie algebras and superal- gebras. In Group Theoretical Methods in Physics, vol. 1–3, pp. 67–76. Harwood Academic Publishers, 1982 • J. Blank, M. Havĺıček. Irreducible *-representations of Lie superalgebras B(0, n) with finite-degenerated vacuum. Journal of Mathematical Physics 27(12):2823–2831, 1986. https://doi.org/10. 1063/1.527257 • J. Blank, M. Havĺıček. Irreducible *-representations of the Lie superalgebras B(0, n) with finite- degenerated vacuum. II. Journal of Mathematical Physics 29(3):546–559, 1988. https://doi.org/ 10.1063/1.528048 • J. Blank, M. Havĺıček. On the tensor product of supersingleton representations of osp(1, 2n). Czechoslovak Journal of Physics B 39(11):1192–1207, 1989. https://doi.org/10. 1007/BF01605320 • J. Blank, M. Havĺıček. On the tensor product of supersingleton representations of Lie superal- gebras osp(1, 2n). In Selected Topics in Quantum Field Theory and Mathematical Physics, pp. 190– 196. World Scientific, 1989 Among the important structural results obtained for B(0; n)-type superalgebras, we emphasise a new method for constructing infinite-dimensional represen- tations of superalgebras, as well as their description in terms of creation-annihilation operators of para-Bose systems with n degrees of freedom. A lot of attention was also devoted to the *-representations of Lie super- algebras of type B(0; n) and real form osp(1; 2n)9, and the tensor product decomposition of metaplectic repre- sentation σn. In particular, a precise decomposition of the *-representation σ̂n of the orthosymplectic super- algebra osp(1; 2n) related to the Kronecker product of two supersingleton representations was obtained. These results allowed a considerable simplification in the description of generators and relations in the odd sector. Concerning the *-representations of osp(1; 2n), it was observed that the commutation relations of the odd generators of the algebra coincide with those derived by Y. Ohnuki and S. Kamefuchi in 1982, considering parastatistics of order 2, for construct- ing the reduction of the tensor product of generic star representations of osp(1; 2n). Calling P (n) M the representation of sp(n,R) obtained by restriction to the even sector of the orthosymplectic superal- gebra, several intriguing properties were deduced. In particular, it was shown that each representa- tion P (n) M generically admits two non-equivalent *- extensions to the pseudounitary group SU(n, n). For the special value n = 2, the procedure provided ex- plicit forms for infinite-dimensional representations of osp(1; 4), previously considered and classified by Heidenreich [46]. 5. Quantum groups With the emergence of quantum groups in the late 1980s and the beginning of 1990s, Havĺıček’s attention was focused on this important topic, where he collab- orated with several colleagues in Prague and abroad, mainly with Anatoly U. Klimyk in Kiev, a great spe- cialist in structure and representation theory of Lie (super)algebras, as well as Edita Pelantová and Sev- erin Pošta. These works were primarily devoted to a concise, systematic and deep structural study of 9Ω(z∗) = Ω(z)∗ adjoint operation adjoint of linear differen- tial operator. 505 https://doi.org/10.1007/BF01603588 https://doi.org/10.1007/BF01603588 https://doi.org/10.1063/1.525373 https://doi.org/10.1063/1.525373 https://doi.org/10.1063/1.527257 https://doi.org/10.1063/1.527257 https://doi.org/10.1063/1.528048 https://doi.org/10.1063/1.528048 https://doi.org/10.1007/BF01605320 https://doi.org/10.1007/BF01605320 Rutwig Campoamor-Stursberg Acta Polytechnica Uq(gl(n,C)) and Uq(som), although other topics con- cerning the general structure of quantum groups were considered as well: • Č. Burd́ık, M. Havĺıček, A. Vančura. Irre- ducible highest weight representations of quantum groups Uq(gl(n,C)). Communications in Mathe- matical Physics 148(2):417–423, 1992. https:// doi.org/10.1007/BF02100869 • M. Havĺıček, E. Pelantová, A. Klimyk. Nonstandard Uq(so3) and Uq(so4): Tensor products of represen- tations, oscillator realizations and roots of unity. Czechoslovak Journal of Physics 47(1):13–16, 1997. https://doi.org/10.1023/A:1021431709238 • M. Havĺıček, E. Pelantová. Santilli-Fairlie algebra Uq(so3): Tensor products of representations, oscilla- tor realizations and roots of unity. Hadronic Journal 20(6):603–614, 1997 • M. Havĺıček, S. Pošta, A. U. Klimyk. Repre- sentations of the cyclically symmetric q-deformed algebra Uq(so3). Czechoslovak Journal of Physics 48(11):1347–1353, 1998. https://doi. org/10.1023/A:1021692803323 • M. Havĺıček, A. U. Klimyk, E. Pelantová. Repre- sentations of the q-deformed algebra Uq(so4) for q a root of unity. Methods in Functional Analysis and Topology 4(3):39–44, 1998 • M. Havĺıček, A. U. Klimyk, S. Pošta. Rep- resentations of the cyclically symmetric q- deformed algebra soq(3). Journal of Mathematical Physics 40(4):2135–2161, 1999. https://doi.org/ 10.1063/1.532856 • M. Havĺıček, A. U. Klimyk, S. Pošta. Representa- tions of the q-deformed algebra Uq(iso2). Journal of Physics A: Mathematical and General 32(25):4681, 1999. https://doi.org/10.1088/0305-4470/32/ 25/310 • M. Havĺıček, S. Pošta, A. U. Klimyk. Representa- tions of the q-deformed algebra soq(2, 1). In Sym- metry in Nonlinear Mathematical Physics, vol. 30 of Proceedings of Institute of Mathematics of NAS of Ukraine, pp. 280–287. 2000 • M. Havĺıček, A. U. Klimyk, S. Pošta. Central elements of the algebras U ′ q(som) and Uq(isom). Czechoslovak Journal of Physics 50(1):79–84, 2000. https://doi.org/10.1023/A:1022825031633 • M. Havĺıček, A. U. Klimyk, S. Pošta. Clas- sification of representations of the alge- bra Uq′(so3) through examples. Czechoslovak Journal of Physics 50(11):1235–1238, 2000. https://doi.org/10.1023/A:1022804806462 • M. Havĺıček, S. Pošta, A. U. Klimyk. Some basic properties of nonstandard deformations U ′ q(so3), U ′ q(so4). In S. T. Ali, H.-D. Doebner, M. Keyl, R. Werner (eds.), Trends in Quantum Mechanics: Proceedings of the International Sympo- sium Goslar, Germany, pp. 10–17. 1999 • M. Havĺıček, S. Pošta. On the classification of irreducible finite-dimensional representations of U ′ q(so3) algebra. Journal of Mathematical Physics 42(1):472–500, 2001. https://doi.org/10.1063/ 1.1328078 • M. Havĺıček, A. U. Klimyk, S. Pošta. Representa- tions of the q-deformed algebra U ′ q(so4). Journal of Mathematical Physics 42(11):5389–5416, 2001. https://doi.org/10.1063/1.1402631 • M. Havĺıček, S. Pošta, A. U. Klimyk. Classifi- cation of representations of the algebra Uq′(so3) through examples II. Physics of Atomic Nu- clei 64(12):2151–2155, 2001. https://doi.org/10. 1134/1.1432917 • Č. Burd́ık, M. Havĺıček, O. Navrátil, S. Pošta. Ideals of the enveloping algebra U(osp(1, 2)). Journal of Generalized Lie Theory and Applications 2(3):132– 136, 2008 • R. M. Asherova, Č. Burd́ık, M. Havĺıček, et al. q-analog of Gel’fand-Graev basis for the noncom- pact quantum algebra Uq(u(n, 1)). Symmetry, Integrability and Geometry: Methods and Appli- cations 6:10, 2010. https://doi.org/10.3842/ SIGMA.2010.010 • M. Havĺıček, S. Pošta. Central elements of quantum deformations. AIP Conference Proceed- ings 1307(1):125–130, 2010. https://doi.org/10. 1063/1.3527408 • M. Havĺıček, S. Pošta. Center of quantum al- gebra U ′ q(so3). Journal of Mathematical Physics 52(4):043521, 2011. https://doi.org/10.1063/1. 3579992 These articles, of great technical complexity, ex- panded upon and generalised various results, and clarified many questions that have, until then, been only partially studied or understood. An exhaustive study of the standard Uq(so(n)) and nonstandard U ′ q(so(n)) quantum algebras for n = 2, 3, 4 and their representations began. Being rather difficult to con- dense the depth of these works to a few lines, we merely enumerate some of the salient structural re- sults. One remarkable achievement was the construc- tion of tensor products in the Santilli-Fairlie algebra Uq(so(3)), which does not possess a Hopf algebra struc- ture, a property that is central for the description of tensor products in the context of quantum groups. Nevertheless, a procedure for constructing a tensor product was given, together with an explicit method for the product of two irreducible representations of Uq(so(3)) for positive q. Moreover, for the case, when q is a root of unity, irreducible representations were constructed. In order to cover the remaining cases, an algebra homomorphism Ψ from the nonstandard algebra Uq(so(3)) to the extension Ûq(sl(2)) of the Hopf algebra Uq(sl(2)) was introduced. The composi- tion of Ψ with irreducible representations of Ûq(sl(2)) led to (not necessarily irreducible) representations of 506 https://doi.org/10.1007/BF02100869 https://doi.org/10.1007/BF02100869 https://doi.org/10.1023/A:1021431709238 https://doi.org/10.1023/A:1021692803323 https://doi.org/10.1023/A:1021692803323 https://doi.org/10.1063/1.532856 https://doi.org/10.1063/1.532856 https://doi.org/10.1088/0305-4470/32/25/310 https://doi.org/10.1088/0305-4470/32/25/310 https://doi.org/10.1023/A:1022825031633 https://doi.org/10.1023/A:1022804806462 https://doi.org/10.1063/1.1328078 https://doi.org/10.1063/1.1328078 https://doi.org/10.1063/1.1402631 https://doi.org/10.1134/1.1432917 https://doi.org/10.1134/1.1432917 https://doi.org/10.3842/SIGMA.2010.010 https://doi.org/10.3842/SIGMA.2010.010 https://doi.org/10.1063/1.3527408 https://doi.org/10.1063/1.3527408 https://doi.org/10.1063/1.3579992 https://doi.org/10.1063/1.3579992 vol. 65 no. 5/2025 The scientific legacy of Miloslav Havĺıček Uq(so(3)). Analysing in detail the decomposition into irreducible components, all IR of Uq(so(3)) when q is not a root of unity could be determined. Another difficult problem addressed in these arti- cles was the analysis of the centre of the nonstan- dard quantum algebra U ′ q(so(3)) (earlier proposed by Gavrilik and Klimyk in [65] in order to construct representations by operators acting according to the Gel’fand-Tsetlin pattern). For the case of roots of unity, it was shown that there are four generators of the center, which depend on the order of q and whose polynomial dependence was explicitly indicated, while in the non-root of unity case, the centre was shown to be a polynomial algebra in one variable. These results were relevant for the general case of the central elements of U ′ q(som) and U ′ q(isom), allowing also to find relations with the case of U ′ q(so3). In this context, Miloslav and S. Pošta showed how the so-called Dia- mond lemma, a quite unknown result in ring theory, could be successfully applied to the Poincaré–Birkhoff– Witt property in quantum algebras, allowing to derive, in simple and elegant way, certain facts concerning their centre. Besides these exhaustive results, a quantum ana- logue of Gel’fand–Graev bases for the noncompact quantum algebra Uq(u(n, 1)) was also obtained, and the Hermitean irreducible representations correspond- ing to a discrete series were computed. These re- sults were shown to be crucial for the computation of pairings on Mickelsson algebras, and hence for the computation of inverse Shapovalov forms [66]. 6. Lie gradings The notion of gradation in Lie algebras is an old one, and besides the well known Cartan decomposition, other gradings have already been used in the liter- ature (e.g. in the superalgebra context), although the problem had not been considered generically. In 1989, Hans Zassenhaus and Jǐŕı Patera began such a systematic classification of gradings [67], introduc- ing the notion of fine grading and giving a criterion for this property. The classification problem, however, remained mainly untouched for some years due to the death of Zassenhaus in 1991, and it was not until the mid 1990s, when Edita Pelantová and Miloslav joined Patera to complete the task, with Jǐŕı Tolar joining the group later. These works not only finished the program established by Patera and Zassenhaus, but also led to new techniques that have found wide appli- cations, both in the Lie theory and physical problems. We enumerate Miloslav’s principal articles concerning this subject: • M. Havĺıček, J. Patera, E. Pelantová. On the max- imal Abelian subgroups of the diagonalizable au- tomorphisms of simple classical Lie algebras. In H. D. Doebner, P. Nattermann, W. Scherer (eds.), Group Theoretical Methods in Physics, Proceedings of XXI International Colloquium on Group The- oretical Methods in Physics, pp. 116–120. World Scientific, Singapore, 1997 • M. Havĺıček, J. Patera, E. Pelantová. On the fine gradings of simple classical Lie alge- bras. International Journal of Modern Physics A 12(1):189–194, 1997. https://doi.org/10.1142/ S0217751X97000268 • M. Havĺıcek, J. Patera, E. Pelantova. On Lie gradings II. Linear Algebra and its Applica- tions 277(1–3):97–125, 1998. https://doi.org/10. 1016/S0024-3795(97)10039-8 • M. Havĺıček, J. Patera, E. Pelantová. On Lie grad- ings III. Gradings of the real forms of classical Lie algebras. Linear Algebra and its Applications 314(1– 3):1–47, 2000. https://doi.org/10.1016/S0024- 3795(00)00099-9 • J. Patera, M. Havĺıček, E. Pelantová, J. Tolar. On fine gradings and their symmetries. Czechoslovak Journal of Physics 51(4):383–391, 2001. https:// doi.org/10.1023/A:1017501925328 • M. Havĺıček, J. Patera, E. Pelantová, J. Tolar. Au- tomorphisms of the fine grading of sl(n,C) asso- ciated with the generalized Pauli matrices. Jour- nal of Mathematical Physics 43(2):1083–1094, 2002. https://doi.org/10.1063/1.1430046 • M. Havĺıček, E. Pelantová, J. Patera, J. Tolar. Distinguished bases of sl(n,C) and their symme- tries. In Quantum Theory and Symmetries, pp. 366– 370. World Scientific, 2002. https://doi.org/10. 1142/9789812777850_0043 • M. Havĺıček, J. Patera, E. Pelantová, J. Tolar. On Pauli graded contractions of sl(3,C). Journal of Nonlinear Mathematical Physics 11(1):37–42, 2004. https://doi.org/10.2991/jnmp.2004.11.s1.4 • M. Havĺıček, E. Pelantová, J. Tolar. On represen- tations of sl(n,C) compatible with a Z2-grading. Acta Polytechnica 50(5):30–39, 2010. https://doi. org/10.14311/1261 These works in particular use the classification of the (maximal) commutative subgroups in the auto- morphism group of gl(n,C), with special emphasis on the inner and outer automorphisms, as fine gradings can be classified, up to equivalence, by the maximal Abelian groups of diagonalisable automorphisms of the Lie algebra (called MAD-groups)10. As a first decisive advance towards the classification, a detailed procedure to determine fine gradings for the class of classical Lie algebras was given, and an equivalence criterion for fine gradings based on labeled graphs was proposed. It was soon recognised that fine gradings constitute a powerful tool for the structural study of solvable (respectively nilpotent) Lie algebras [78], and that the contraction and deformation theories of 10From a different point of view, the problem of Abelian sub- groups had also been considered by Suprunenko and Tyshkevich in 1966 [77]. 507 https://doi.org/10.1142/S0217751X97000268 https://doi.org/10.1142/S0217751X97000268 https://doi.org/10.1016/S0024-3795(97)10039-8 https://doi.org/10.1016/S0024-3795(97)10039-8 https://doi.org/10.1016/S0024-3795(00)00099-9 https://doi.org/10.1016/S0024-3795(00)00099-9 https://doi.org/10.1023/A:1017501925328 https://doi.org/10.1023/A:1017501925328 https://doi.org/10.1063/1.1430046 https://doi.org/10.1142/9789812777850_0043 https://doi.org/10.1142/9789812777850_0043 https://doi.org/10.2991/jnmp.2004.11.s1.4 https://doi.org/10.14311/1261 https://doi.org/10.14311/1261 Rutwig Campoamor-Stursberg Acta Polytechnica Lie algebras could be approached alternatively with these techniques, leading to new and interesting ap- plications [79, 80]. In this context, the gl(n,C)-fine gradings were analysed in detail in connection with sl(n,C)-contractions. In particular, for the fine grad- ings of the latter algebra, it was observed that the group SL(2,Zn) plays an analogue rôle to the Weyl group for the canonical Cartan grading. Once the classical case systematised, the next diffi- cult step consisted in extending these results to the real forms of the classical Lie algebras. To this extent, the maximal abelian diagonalisable groups of auto- morphisms for the real forms were studied, and four types of matrix subgroups of GL(n,R) defined. This allowed them to transfer the classification problem of non-conjugate maximal abelian diagonalisable groups for real forms to the description of equivalence classes within the four types of matrix subgroups, hence en- abling them to establish a precise classification. Several other questions related to fine gradings were considered, such as the symmetries associated with the gradings and the class of fine gradings related to the n-dimensional Pauli matrices, which had found several intriguing applications. In this context, par- ticular attention was given to the Pauli grading of sl(3,C), where it was observed that the symmetry transformations of a given grading are in a one-to-one correspondence with a certain quotient group related to automorphisms that permute the grading blocks. For the case of sl(3,C), the Jacobi identity associated with a graded contraction therefore led to a system of quadratic equations for the contraction parameters, the symmetries of which were related to Z2×SL(2,Z3). These nonlinear equations were also analysed for their solutions. It should be mentioned that the compati- bility of representations with Z2-gradings, which have many potential applications to the case of Lie super- algebras, was also studied in detail for several Lie algebras. 7. Differential equations Miloslav’s work on differential equations can be di- vided into two separate subjects: on the one hand, the computation of spectra and criteria for determining the eigenvalues of the Schrödinger equation, and, on the other hand, the problem of existence and obtain- ing nonlinear superposition principles for (systems) of differential equations. The works on spectra were done in collaboration with Ivan Úlehla and Jǐŕı Hořeǰśı, reputed specialists in quantum theory, while those on superposition rules were written with Severin Pošta and Pavel Winternitz, expanding previous work on the topic [81, 82]: • I. Úlehla, M. Havĺıček. New method for computation of discrete spectrum of radical Schrödinger operator. Aplikace matematiky 25(5):358–372, 1980 • I. Úlehla, M. Havĺıček, J. Hořeǰsi. Eigenvalues of the Schrödinger operator via the Prüfer transformation. Physics Letters A 82(2):64–66, 1981. https://doi. org/10.1016/0375-9601(81)90938-5 • M. Havĺıček, S. Pošta, P. Winternitz. Nonlinear superposition formulas based on imprimitive group action. Journal of Mathematical Physics 40(6):3104– 3122, 1999. https://doi.org/10.1063/1.532749 • M. Havĺıček, S. Pošta, P. Winternitz. Superposition formulas based on nonprimitive group action. In A. Coley, D. Levi, R. Milson, et al. (eds.), Bäcklund and Darboux Transformations. The Geometry of Solitons, vol. 29 of CRM Proceedings & Lecture Notes, pp. 225–231. American Mathematical Society, 2001 In the first of the articles with Úlehla, a new method for computing the discrete spectrum of a one-particle Schrödinger operator under spherical symmetry and appropriate potentials such that the spectrum is finite was proposed, by means of a transformation of the radial Schrödinger equation into a first-order ODE for the function z(x, χ): dz dx = (ℓ + 1) cos2 z − 1 ℓ + 1(v(x, χ) + χ2) sin2 z, with the number of eigenvalues being determined by the condition z(∞, 0) = (2k + 1) π 2 , such that the dis- continuity points coincide with the eigenvalues (hence constituting a kind of analogue of the Levinson theo- rem for this function). The procedure contemplated the replacement of the usual Ritz variational method by direct integration techniques. These discontinuities were obtained by successive integration, with accuracy increased for truncations at suitable values depending on the potential. In a following paper, jointly with Jǐŕı Hořeǰśı, the eigenvalue problem for central potential was consid- ered from the perspective of a modified Prüfer trans- formation, giving two theorems that established a the- oretical framework for numerical eigenvalue computa- tion for the case of rapidly decreasing and confining central potential, considered unified for the first time. This approach was later extended in [87] to long-range potentials, including the Coulomb case. The papers on superposition, which is very deeply connected with the classification of realisations of Lie algebras by vector fields, continue the extensive work of Pavel Winternitz on the subject, focusing on im- primitive group actions on manifolds, specifically for the special linear groups SL(n,C), making use of the realisations obtained before by Havĺıček and Lassner. It was shown that such decomposable systems can be studied with indecomposable systems serving as building blocks. The cases for n = 3, 4 were computed explicitly, including the superposition rules for the corresponding ODE systems, providing also a descrip- tion for the general case of SL(n,C), including some relations to soliton equations and Bäcklund transfor- mations. More specifically, when compared to the well-known situation with SL(2,R) and SL(2,C), it 508 https://doi.org/10.1016/0375-9601(81)90938-5 https://doi.org/10.1016/0375-9601(81)90938-5 https://doi.org/10.1063/1.532749 vol. 65 no. 5/2025 The scientific legacy of Miloslav Havĺıček was concluded that the equations derived from the imprimitive action of SL(n,C) should appear as Bäck- lund transformations for integrable systems defined on flag manifolds. 8. Representation theory Havĺıček’s extensive work on the realisation problem of Lie algebras and superalgebras also had many im- portant implications for their representation theory, which led to a first series of papers on highest weight representations, written in collaboration with Pavel Exner and Čestmı́r Burd́ık, and published at the be- ginning 1980s, as well as some applications to the Poincaré group, in collaboration with Jan Kotrbatý, Severin Pošta and Patrick Moylan: • Č. Burd́ık, M. Havĺıček, P. Exner. Highest-weight representations of the sl(n + 1, C) algebras: Maxi- mal representations. Journal of Physics A: Math- ematical and General 14(5):1039, 1981. https: //doi.org/10.1088/0305-4470/14/5/023 • Č. Burd́ık, P. Exner, M. Havĺıček. Highest-weight representations of sl(2, C) and sl(3, C) via canonical realizations. Czechoslovak Journal of Physics B 31(5):459–469, 1981. https://doi.org/10.1007/ BF01596411 • Č. Burd́ık, P. Exner, M. Havĺıček. A com- plete set of irreducible highest-weight represen- tations for sl(3, C). Czechoslovak Journal of Physics B 31(11):1201–1206, 1981. https://doi. org/10.1007/BF01603579 • M. Havĺıček, P. Moylan. An embedding of the Poincaré Lie algebra into an extension of the Lie field of SO0(1, 4). Journal of Mathemati- cal Physics 34(11):5320–5332, 1993. https://doi. org/10.1063/1.530307 • S. Pošta, M. Havĺıček. Note on Verma bases for representations of simple Lie algebras. Acta Poly- technica 53(5):450–456, 2013. https://doi.org/ 10.14311/AP.2013.53.0450 • M. Havĺıček, J. Kotrbatý, P. Moylan, S. Pošta. Con- struction of representations of Poincaré group us- ing Lie fields. Journal of Mathematical Physics 59(2):021702, 2018. https://doi.org/10.1063/1. 4993153 • M. Havĺıček, J. Kotrbatý, P. Moylan, S. Pošta. (Heisenberg-)Weyl algebras, Segal-Bargmann trans- form and representations of Poincaré groups. Jour- nal of Physics: Conference Series 1194(1):012043, 2019. https://doi.org/10.1088/1742- 6596/1194/1/012043 Using previous results concerning the canonical bo- son representations of sl(n + 1,C), for every given weight m, so-called maximal representations Dm were constructed, which contained an irreducible represen- tation with m as the highest weight. Conditions for the irreducibility of the maximal representations were analysed, and a comparison with the standard con- struction of representations performed. An advantage of the new procedure was the explicitness of the con- struction, which proved valuable for applications. In this context, the cases of sl(2,C) and sl(3,C) were analysed in further detail, and irreducibility crite- ria for some types of infinite-dimensional representa- tions were obtained by means of the canonical boson realisations. This allowed to derive a complete de- scription of the irreducible highest-weight representa- tions of sl(3,C), which were shown to be partitioned into five disjoint classes, one corresponding to finite- dimensional representations, and the four remaining to infinite-dimensional representations: ΩF = {Λ : Λi ∈ N, i = 1, 2}, Ω1 = {Λ : Λ1 ∈ N, Λ2 /∈ N}, Ω2 = {Λ : Λ1 /∈ N, Λ2 ∈ N}, Ω12 = {Λ : Λi /∈ N, i = 1, 2; 1 + Λ1 + Λ2 ∈ N}, Ωmax = {Λ : Λi /∈ N, i = 1, 2; 1 + Λ1 + Λ2 /∈ N}, where ΩF is well known from the work of I. M. Gel’fand and M. L. Tsetlin, and Ω1, Ω2, and Ωmax have already been obtained in previous work. The remaining class Ω12 was obtained, completing the classification of infinite-dimensional highest weight representations. Beyond the explicit results, these pa- pers contain precise indications for higher ranks, also indicating the great complexity in deriving explicit expressions for the corresponding classes. Another remarkable contribution to representation theory was made in collaboration with Severin Pošta. This work provided an alternative construction of the Verma basis of the enveloping algebra and finite- dimensional representations of the An Lie algebras, as well as providing a more compact proof of the so-called Verma inequalities [95]. In the context of specific applications of the Poincaré group, Miloslav wrote three papers with Patrick Moylan that extended previous (and appar- ently unpublished [96]) work. The first one, from 1993, showed that the principal series of unitary ray representations of SO0(1, 4) is related, via the *-isomorphism between algebraic extensions of the Lie fields of SO0(1, 4) and the Poincaré group, to real mass, and positive and negative energy representa- tions of the Poincaré Lie algebra with an arbitrary spin. This approach is deeply related to the embedding problem of Lie algebras into their universal enveloping algebra, leading to representations by higher order differential operators, with important implications concerning quasi-exactly solvable systems in quantum mechanics [97]. In the second one (jointly with Jan Kotrbatý and Severin Pošta), which is one of the last papers of Havĺıček, the representations of the Poincaré group in n = 2, 3, 4 dimensions were realised on Hilbert spaces associated with the space of the Schrödinger represen- tation of Weyl algebras. The localisation of universal 509 https://doi.org/10.1088/0305-4470/14/5/023 https://doi.org/10.1088/0305-4470/14/5/023 https://doi.org/10.1007/BF01596411 https://doi.org/10.1007/BF01596411 https://doi.org/10.1007/BF01603579 https://doi.org/10.1007/BF01603579 https://doi.org/10.1063/1.530307 https://doi.org/10.1063/1.530307 https://doi.org/10.14311/AP.2013.53.0450 https://doi.org/10.14311/AP.2013.53.0450 https://doi.org/10.1063/1.4993153 https://doi.org/10.1063/1.4993153 https://doi.org/10.1088/1742-6596/1194/1/012043 https://doi.org/10.1088/1742-6596/1194/1/012043 Rutwig Campoamor-Stursberg Acta Polytechnica enveloping algebras is used as the main technique, de- termining first the algebraic relations between genera- tors of the Poincaré algebra and Heisenberg pairs, in analogy with the Gel’fand–Kirillov conjecture. From these, the realisation of the representations is deduced. It is shown that the action of the basis elements can be integrated to strongly continuous unitary one- parameter subgroups on the Hilbert space, from which a further integration procedure leads to a representa- tion of the corresponding Poincaré group. The equiva- lence of these unitary irreducible representations with those arising from the standard approach using the Wigner-Mackey theory was also proved. 9. A fundamental reference for quantum mechanics In 1993, the textbook “Linear Operators in Quantum Physics” by J. Blank, P. Exner and Miloslav finally appeared, after an adventurous and long genesis [98]. The idea of preparing a book on the fundamental aspects of Quantum Mechanics can be traced back to 1973, when the authors, based on their lectures on the topic at the Charles University and the Czech Technical University, prepared a series of lecture notes, that where revised, compiled and given a textbook form in the late 1980s. The publication, initially scheduled for 1989, was delayed by several years, due to the political and economic changes that shook the country. Unfortunately, prior to its publication, Jǐŕı Blank died in 1990, and could not see the great success that the text would have, still being one of the central references in courses on Quantum Mechanics even today. The book explained in detail the theory of linear operators on Hilbert spaces and their application in quantum theory. With an initial survey on fundamen- tals of linear algebra, topology and functional analysis, as well as measure theory, the main facts on Hilbert spaces and (bounded and unbounded) operators were presented. Physical applications of quantum theory with special emphasis on non-relativistic quantum me- chanics, the second quantisation, and the scattering theory were developed in detail, enriched with many supplementary material and numerous exercises. The relevance of this text was, however, not appre- ciated abroad until its first English edition appeared in 1994 at the American Institute of Physics [99]. Al- though extensive modifications were required due to technical and editorial reasons, the spirit of the first edition remained untouched, and both versions, al- beit their differences, can be seen as uniform. The reception was very favourable, as can be seen in the different reviews of the book at Zentralblatt der Math- ematik and Mathematical Reviews, among others11, and the authors were awarded the Rector’s Prize in 1995 for their important contribution. Some years 11See e.g. M. Gorzelańczyk Zbl 0873.46038 or H. Baumgärtel MR1275370. later, a second edition with the addition of new topics was published in 2008, also being welcomed by the physical community, receiving hundreds of citations in other textbooks and research articles. 10. Conclusion These brief summaries of extensive subjects do not exhaust Havĺıček’s activity, as he also wrote other papers on quite a number of specific questions, such as the integrability properties of representations of semisimple Lie algebras in Hilbert spaces [100], the de- scription of unstable systems [101], or about the notion of quantum-mechanical pseudo-Hamiltonians [102], to which a large number of contributions to national and international conferences must be added. To sum it up, Miloslav’s work has covered almost any of the physical problems that uses group the- ory and algebraic formalism as a fundamental tool, providing new insights and motivating new notions and techniques that have since been proved to be very fruitful. Certainly, there are still a lot of new problems that arise from his work, as the completion of the clas- sification of canonical realisations for the exceptional complex and compact Lie algebras of rank d > 2 (with the case of G2 having been partially classified in [103]), which is certainly a difficult question, specially for the case of E8, due to the intricate structural particu- larities of these algebras. Another relevant problem concerns the mixed realisations, that so far have only been obtained for the (special) general linear algebra sl(n + 1,R) and gl(n + 1,R), but that are likely to be extended to other algebras of the classical series by subtle adaptation of Miloslav’s methods, and even considered for the class of inhomogeneous and other distinguished subalgebras by means of the contraction formalism, with many conceivable applications [104]. There still remains a lot of material to be properly understood in the series of papers on realisations of Lie algebras, that could potentially be also generalised to the superalgebra case and even beyond. There is no doubt that Havĺıček’s work has deeply influenced the younger generations of physicists in the Czech Republic and abroad, as well as many specialists working on group theory from the physical perspective, such as the writer of these lines, inspiring further investigations in several of the problems where he proposed an elegant and effective ansatz. We would like to finish this short reminiscence with a sentence that, to the author’s understanding, per- fectly summarises the influence of Havĺıček’s work and personality in Prague and abroad: “Miloslav̊uv odkaz žije dál”. Acknowledgements Miloslav Znojil, Pavel Exner, Edita Pelantová and Libor Šnobl are gratefully acknowledged for valuable comments that have improved the article. The author is specially indebted to Jindra Niederlová and Alexander V. Turbiner for providing some personal information about Miloslav 510 vol. 65 no. 5/2025 The scientific legacy of Miloslav Havĺıček that has helped to clarify some points in the exposition, as well as for motivating a written version of the talk. The author also acknowledges the Dean’s Office of the Faculty of Mathematics and Physics, Charles University, the Institute of Informatics of the Academy of Sciences of the Czech Republic and the Archives of the Czech Technical University for providing updated information on Havĺıčeks professional trajectory. During the preparation of this work, the author received partial support from the Agencia Estatal de Investigación (Spain) under the grant PID2023-148373NB-I00 funded by MCIN/AEI/10.13039/501100011033/FEDER, UE. References [1] M. Havĺıček. Kanonicheskie realizacii klassicheskikh algebr Li [In Russian; Canonical realizations of classical Lie algebras]. 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World Scientific, 2020. https://doi.org/10.1142/11537 514 https://doi.org/10.1063/1.532749 https://doi.org/10.1007/bf01603581 https://doi.org/10.1088/0305-4470/14/5/023 https://doi.org/10.1007/BF01596411 https://doi.org/10.1007/BF01603579 https://doi.org/10.1063/1.530307 https://doi.org/10.14311/AP.2013.53.0450 https://doi.org/10.1063/1.4993153 https://doi.org/10.1088/1742-6596/1194/1/012043 https://doi.org/10.1016/S0022-4049(97)00022-4 https://doi.org/10.1016/0034-4877(75)90007-5 https://doi.org/10.1007/bf01593909 https://doi.org/10.1007/bf01590200 https://doi.org/10.1007/bf01607580 https://doi.org/10.1142/11537 Acta Polytechnica 65(5):500–514, 2025 1 Introduction. academic and professional trajectory 2 The infinite dimensional Lie algebra A(P,S) 3 Realisations of Lie algebras 4 Realisations of Lie superalgebras 5 Quantum groups 6 Lie gradings 7 Differential equations 8 Representation theory 9 A fundamental reference for quantum mechanics 10 Conclusion Acknowledgements References