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Q. When did the notion of homeomorphism reach its modern formulation as a bicontinuous bijection, i.e., a continuous bijection between topological spaces whose inverse is also continuous?

Was this present in Riemann's work (1826-1866)? Or in the work of Möbius (1790-1868); or Jordan (1838-1922)? Was it clearly formulated by 1900? Or only later, perhaps by Heegaard (1871-1948), or Dehn (1878-1952), or Whitney (1907-1989)?

I am trying to understand the history behind the classification theorem for compact surfaces, and it seems developing a precise notion of "homeomorphism" was a key step.

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    $\begingroup$ Isn't Hausdorff the one who actually axiomatized topological spaces? $\endgroup$ Commented Mar 20, 2015 at 23:28
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    $\begingroup$ Hausdorff's axioms included what we now recognize as the $T_2$ axiom that now bears his name. There's a good math.stackexchange answer on some of the history here: math.stackexchange.com/questions/70445/… $\endgroup$ Commented Mar 21, 2015 at 0:06
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    $\begingroup$ I like the answer on that Hausdorff's axioms StackExchange link: "A rather detailed and interesting discussion of the extremely convoluted history can be found in the paper by Gregory H. Moore"... Well, same is true here! $\endgroup$ Commented Mar 21, 2015 at 1:21
  • $\begingroup$ Joseph, I'm having a discussion with a mod at History of Science and Mathematics, who expressed interest in this thread. I half-wondered myself whether it would have fitted well over there, and whether you would have been open to a migration, or whether you're generally open to/interested in using that site. (Of course I'm not suggesting migration of this post now.) They would like more professionals from here to chime in over there if there is interest. Just thinking aloud... $\endgroup$ Commented Mar 21, 2015 at 17:09
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    $\begingroup$ Appendix D of the 2011 Gallier/Xu book maths.ed.ac.uk/~s1142600/images/surfclass gives a short history of the classification theorem for compact surfaces, but I don't think it is as nuanced as Moore's analysis (eg, no difference is made between homotopy/homeomorphism is made vis-a-vis Möbius/Jordan, "umkehrbar eindeutiger stetiger" in von Dyck is seen as the same as bicontinuous [which may be true, though Moore disputes it, based on how later authors interpreted it]). In retrospect, I don't think "homeomorphic" per se is the key idea, but what "topologically equivalent" means. $\endgroup$ Commented Mar 21, 2015 at 20:34

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Well, all I did was a search on "homeomorphism history", but... I tried to extract some points that are made in conjunction to your question (Riemann, Möbius, Jordan), though feel free to edit it down if it is too long (and apologies to those who think this should be remapped to a History of Math Q/A).

The evolution of the concept of homeomorphism, by Gregory H. Moore
Historia Mathematica, Volume 34, Issue 3, August 2007, Pages 333–343
http://www.sciencedirect.com/science/article/pii/S0315086006000863

tl,dr: By 1930, the modern concept had been reached. From 1910-30 the definition (or common understanding of "topological invariance") moved definitively to bicontinuous (Fréchet, Hausdorff, and encyclopedists Zoretti and Rosenthal aiding this), whereas previously merely "continuous" was more popular (starting from von Dyck in 1888). Prior to that, the less-restrictive "deformations" (homotopies) were more prevalent in the thinking of Möbius, Jordan, and Klein (1860/70s), and while Poincaré (1895) coined the term homeomorphism, his meaning was that of diffeomorphism. Incidentally, Riemann had no notion of a topological mapping in his work.

Specifically regarding the question (unless otherwise indicated, all the below is from Moore's article):

Section 2. The evolution of the concept of “homeomorphism” was essentially complete by 1935 when Pavel Aleksandrov (Paul Alexandroff) at the University of Moscow and Heinz Hopf at the Eidgenossische Technische Hochschule in Zurich published their justly famous book Topologie, aiming to unify the two major branches of topology, the algebraic and the set-theoretic. They took as their fundamental undefined concept “topological space,” based on the closure axioms of Kazimierz Kuratowski [1922]. And they defined a homeomorphism between topological spaces in the way that is now standard: “A one–one continuous mapping $f$ of a space $X$ into a space Y is called a topological mapping or a homeomorphism (between $X$ and $f (X) = Y ⊆ Y$ ) if the inverse of $f$ is a continuous mapping of $Y$ to $X$. Two spaces... are called homeomorphic if they can each be mapped topologically onto each other” [Aleksandrov and Hopf, 1935, 52].

Concerning the origins of topology, Aleksandrov and Hopf wrote: “We must regard Poincaré and Cantor as the immediate founders of topology” [1935, 5]. So the reader might think that he should read the works of Poincaré and Cantor if he wished to find the origin of the concept of homeomorphism. However, the reader would then find that Cantor’s published works contain nothing at all about homeomorphisms, and very little about continuous functions, ...

[Quoting Johnson [1979, 127] about Riemann: What we find conspicuously lacking in Riemann’s work is the notion of a topological mapping. For modern mathematicians topology is inseparable from homeomorphisms. Riemann never contemplated these in his programme of analysis situs [i.e. topology].]

As for Poincaré, there is a particularly interesting discovery to be made. Although Poincaré coined the word “homeomorphism” in [1895], he meant by it something quite different from and more restricted than what is meant nowadays. ... his “homeomorphism” had strong requirements of differentiability and smoothness that have nothing directly to do with topology ... for Poincaré a “homeomorphism” is not a homeomorphism in the modern sense, but rather a diffeomorphism. ... [Also noted is his 1892 article which spoke of deformations (homotopy), while an 1900 article of his might have used the word "homeomorphism" in the modern sense.]

Section 3. Since Poincaré’s 1895 article is the origin of the word “homeomorphism” but not of the concept of homeomorphism, how did that concept originate? At the time that Poincaré wrote, there was a second and broader concept of homeomorphism in use. This second concept was clearly stated by Walther von Dyck in an 1888 article on analysis situs: “Absolute properties [in analysis situs] can also be characterized as those, for whose agreement on two manifolds, it is necessary and sufficient that there exists a one–one continuous function [umkehrbar eindeutiger stetiger Beziehung] between all elements of the two manifolds” [1888, 457]. [Footnote 4 notes that the German phrase could conceivably be interpreted either as "(umkehrbar eindeutiger) und stetiger" or "umkehrbar (eindeutiger und stetiger)", loosely "reversible mapping and continuous" and the question is whether "umkehrbar" (reversible) modifies "stetiger" (continuous); Moore notes that later mathematicians preferred the first construal.]

For the rest of the present note, a one–one continuous function from one subset of Euclidean space onto another will be called a “$D$-homeomorphism,” after von Dyck, since a $D$-homeomorphism is a broader concept (both for Euclidean spaces and more generally) than a homeomorphism. But more than three decades were to pass before $D$-homeomorphisms were clearly distinguished from homeomorphisms. ...

It is a plausible conjecture that many of those who used $D$-homeomorphisms (something which continued to occur at least until 1924) implicitly assumed that every $D$-homeomorphism is a homeomorphism, i.e., that the inverse function is continuous. Such a result was necessary, in particular, if the inverse of a $D$-homeomorphism was to be a $D$-homeomorphism. And such a result would have been true if they had only considered, in $n$-dimensional Euclidean space, sets which are both closed and bounded. But prior to Camille Jordan’s work [1893], discussed in Section 4 below, this condition was never made explicit. As we shall see when discussing Hurwitz [1898], there was a good deal of murkiness around $D$-homeomorphisms. ...

In his article of 1863, Möbius wrote:

Two geometric figures are said to be elementarily related to each other if each infinitesimal element (in all dimensions) of the one figure corresponds to a similar element of the other in such a way that if any two bounding elements of the one figure are contiguous, then the same is true of the corresponding elements in the other; or, what expresses the same thing, if a point of the one figure corresponds to a point of the other, then any two infinitely close points of the one figure correspond to infinitely close points of the other. In this regard, a curve can only be elementarily related to a curve, a surface only to a surface, and a solid body only to a solid body. [1863, 435]

Nothing in Möbius’s article settles the question of whether he was thinking of his “elementary relationships” as homeomorphisms or as diffeomorphisms or as something different from both, such as deformations. All of his diagrams dealt with smooth two-dimensional manifolds. His use of infinitesimals suggests that he regarded his relations as differentiable. (In any case, at the time he wrote, examples of continuous nowhere differentiable functions were known only to a few mathematicians.)

The theorems stated in Möbius’s article would all remain true whether he was thinking of his elementary relationships as homeomorphisms, diffeomorphisms, or deformations. A typical such theorem was that a curve could be elementarily related only to a curve, a surface to a surface, and a solid body to a solid body. Another theorem was that two surfaces in a plane are elementarily related if and only if they have the same finite number of boundary curves [1863, 439]. ...

[Later in the section, it is noted Möbius introduced the "rubber sheet" geometry (deformations) in this article/manuscript, similarly Jordan had deformations in his 1866 paper, and 10 years later Klein appeared to think in terms of deformations (which are homotopies, so less restrictive than homeomorphisms). Some comments are made about Schonflies (1906-8), Zoretti (1912), and Rosenthal (1924) the latter who finally distinguished between $D$-homeomorphism and homeomorphism: "For F. Klein [1872] and A. Hurwitz [1898] analysis situs [topology] is the study of those properties of figures (or point-sets) which are preserved by all one–one continuous mappings. It is altogether preferable to require here invariance with respect to one–one continuous mappings whose inverses are also continuous. However, this distinction is only relevant for those figures which are not closed and bounded." Moreover, the article states "[t]here is evidence that even Felix Hausdorff, a decade before he introduced his version of topological spaces, shared the erroneous view of Hurwitz [1898] and Schoenflies that topology is about the invariants of $D$-homeomorphisms."]

As late as 1924 some eminent algebraic topologists continued to use the older and inadequate definition of homeomorphism, i.e., of $D$-homeomorphism. Among those who did so was Solomon Lefschetz. ... However, six years later Lefschetz adopted the modern definition of homeomorphism [1930, 3], and he retained this definition in later works [1942, 7]. In their 1934 textbook of algebraic topology, Herbert Seifert and William Threlfall (Dresden) wrote that “topology has to do with those properties of geometric figures that are unaltered by topological mappings, i.e., one–one functions such that they and their inverses are continuous” [1934, 1]. Thus Seifert and Threlfall accepted the modern definition of homeomorphism. From about 1930, the modern definition has been dominant both in general topology and in algebraic topology.

Section 4. (Homeomorphisms in abstract spaces)
Already by 1906, spaces more abstract than $n$-dimensional Euclidean space had been proposed. In his doctoral dissertation, Maurice Fréchet had been the first to introduce metric spaces (though under another name) as well as his still more general L-spaces, which were based on an abstract notion of the limit of an infinite sequence of points [1906]. In this context, Fréchet carried over from analysis the concept of a continuous function defined in terms of sequences. ...

Although in 1906 Fréchet did not discuss homeomorphisms between two of his L-spaces, he did so four years later in an article in Mathematische Annalen on the concept of topological dimension. Given two sets $E_1$ and $E_2$, each part of an L-space, he wrote “that they are the image of each other, or that they are homeomorphic, if there exists between them a one–one correspondence which is bicontinuous [une correspondance biunivoque qui est bicontinue]” [1910, 146]. And he was quite explicit that such a function was bicontinuous if and only if it and its inverse were continuous. This was the first time that the concept of homeomorphism was formulated in a more general context than $n$-dimensional Euclidean space. [Footnote 6: Fréchet adopted the term “homeomorphism” from his teacher Hadamard, rather than directly from Poincaré.]

When Hausdorff formulated the concept of a Hausdorff topological space in his 1914 book, he generalized the concept of a continuous function to such spaces. His definition was explicitly motivated by the epsilon–delta definition of continuity of a real function due to Weierstrass. Since Hausdorff’s axioms for a topological space were in terms of neighborhoods, his new generalized definition of continuous function was also formulated in terms of neighborhoods: ...

He then isolated the essential relationship between homeomorphisms and one–one continuous functions by giving the condition under which a one–one continuous function is actually a homeomorphism, although he did so without ever using the term homeomorphism: “If $B$ is the one–one continuous image of a set $A$ that is compact-in-itself [every infinite subset $A$ of $B$ has a limit point that belongs to $B$] then $A$ is also the continuous image of $B$." ...

It is surprising, under these circumstances, that nowhere in his 1914 book does Hausdorff define the concept of homeomorphism, and nowhere in it does he use the word “homeomorphism” or an equivalent term. Only in the second edition of the book in 1927 did he define the concept of homeomorphism. There he gave the definition in a way that suggests that he may have gotten it from Fréchet’s article of 1910. Hausdorff was thinking of a set $A$ and a set $B$, together with a function $φ : A → B$ and its inverse function $ψ : B → A$ (he explicitly allowed both $φ$ and $ψ$ to be many-valued). Then he wrote:

If, however, both functions $y = φ(x)$ and $x = ψ(y)$ are single-valued and continuous, then each of them will be called reversibly continuous or continuous from both sides or doubly continuous (fonction bicontinue). $B$ is also called a homeomorphic image of $A$.., and the one–one mapping between both sets is called a homeomorphism. ... [1927, 195–196]

The context in which Hausdorff gave this definition was that of metric spaces, since topological spaces were only discussed, very briefly, later in the book [1927, 226–232]. The French phrase “fonction bicontinue” that Hausdorff included in his original German text shows that he had in mind some French author as the source of the underlying idea that a function and its inverse are both continuous. Apparently this use of “bicontinue” originated with Fréchet [1910]. ...

Intriguingly, by 1921 the Polish school of topologists had ... surpassed French and German authors in understanding the difference between homeomorphisms and $D$-homeomorphisms, even in Euclidean spaces. [Kuratowski's 1921 solution of a 1920 problem posed by Sierpinski is noted: if $P$ is a 1-1 continuous image of $Q$ and vice-versa, must they be homeomorphic?] ... Both Sierpinski and Kuratowski wrote important topology textbooks, Sierpinski in Polish [1928], which was then translated into English [1934], and Kuratowski in French [1933]. In both of these books, homeomorphisms were given the modern meaning. Thus by the early 1930s, homeomorphisms in the modern sense were the standard within English, French, German, and Polish textbooks of topology.

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    $\begingroup$ Although the article was found by a simple google search, your summary of it is very nice; I wouldn't change it (i.e., I don't think it should be trimmed down). $\endgroup$ Commented Mar 21, 2015 at 0:18
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    $\begingroup$ Wow! What a complex story! Thanks so much for finding this. $\endgroup$ Commented Mar 21, 2015 at 0:36
  • $\begingroup$ I think that it may be a good idea to post this question in HSM Stack Exchange. $\endgroup$
    – user57432
    Commented Mar 22, 2015 at 6:36
  • $\begingroup$ @user170039: Now posted at HSM with pointers back to here. $\endgroup$ Commented Mar 22, 2015 at 14:47
  • $\begingroup$ @user170039: A moderator at HSM told me not to crosspost, so I deleted it. $\endgroup$ Commented Mar 22, 2015 at 16:43

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