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Understanding of "quantization" achieved much progress recent years, especially after Kontsevich breakthrough on deformation quantization, where he proved one-to-one correspondence between Poisson brackets and associative algebras which deform in non-commutative direction algebra of functions on a smooth manifold. However most of these achievements have a algebraic flavor, my question concerns "adding analysis" to algebraic achievements.

Main belief: It is natural to believe that for a compact symplectic manifold $(M,\omega)$ one can construct a $C^*$-algebra which is "quantization" of the algebra of functions on $M$.

Focused question: Can one characterize such $C^*$-algebras ? (In "classical limit" we have a simple description "compact symplectic manifold " one may hope that there can be some simple description in "quantum" case).

Further questions: what is known in the direction of such belief ? What about existence and examples ? What about special properties of such algebras ?

"Smooth functions" in such algebra should be isomorphic to deformation quantization of smooth functions on $M$ for $h=1$ (respectively $h=1/k, k \in Z$ corresponds to $(M, k\omega)$).

The example of such situation is torus $T^2$ with standard symplectic form which "corresponds" to noncommutative torus $C^*$-algebra.

It is also natural to expect that for the case $[\omega] \in H^2(M,Z) $ (i.e. integrality condition) such $C^*$-algebra has a UNIQUE finite-dimensional irreducible representation which dimension is given by $ \int_{M} e^\omega Td(M)$ - index formula. (Which in the case of flat $M$ is just $ 1/n! $*(symplectic volume) the fact which was somehow known from early days of quantum theory (probably goes back to Zommerfeld or Heisenberg, at least it is mentioned in Landau-Lifshitz textbook as "number of quantum states corresponds to classical $dpdq / h$ bits of volume" ). In the case of quantum torus $AB= q BA$ it has n-dimensional irrep iff $q^n=1$, that indeed corresponds to the case quantization of torus with symplectic volume equal to $n$, i.e. $[\omega] \in H^2(M,Z) $. (See another example in MO231072, especially remark 3.

In the case $M$ is Kaehler one my expect that such irrep can be constructed by Berezin-Toeplitz quantization (see e.g. Schlichenmaier ).

The algebra should probably has a trace functional (i.e. $Tr:A\to C, Tr(AB)=Tr(BA)$) which should correspond to integration over $M$ (here we appeal to a kind of deformation quantization picture - that the algebra as a linear space is the same as algebra of functions on $M$, but the product is deformed to non-commutative).

One may push further the classical-to-quantum dictionary: "states" in quantum and classical cases might be related, Lagrangian submanifolds should correspond to certain one-sided ideals in the algebra, so on...

There are lots of compact symplectic manifolds for example complex projective spaces and their submanifolds - can one describe corresponding $C^*$-algebras ?

The simplest example of $S^2$ is discussed in MO231072. One can also discuss flag manifolds in the same vein, and also complex projective spaces and more generally toric manifolds in different, but explicit manner.

  • I think this can be done using geometric quantization. – Qiaochu Yuan Feb 09 '16 at 20:25
  • Are you interested in what kinds of quantization? It looks like you're looking for strict deformation quantization. If this is the case, geometric quantization of symplectic groupoids gives the answer since you're just dealing with symplectic manifolds (which are, then, integrable). – user40276 Feb 09 '16 at 23:39
  • About the C^* algebras you would have to classify all groupoid convolution algebras that arises from the fundamental groupoid or the pair groupoid. This should not be very difficult. – user40276 Feb 09 '16 at 23:45
  • @QiaochuYuan I am not sure ... also there can be different viewpoints on geometric quantization. – Alexander Chervov Feb 13 '16 at 19:36
  • @user40276 quantization is unique up to certain things. Deformation quantization is very good, but it gives series in h... the hope is that it is convergent in ceratain sense and we can put $h=1$ and get the honest C^*-algebra. – Alexander Chervov Feb 13 '16 at 19:40
  • My comment concerned strict deformation quantization, where there's indeed a convergenc and a C^*-algebra for "every" h. – user40276 Feb 13 '16 at 20:36
  • @user40276 I am not sure "strict" is good, there are certain "No-Go" in Rieffel https://math.berkeley.edu/~rieffel/papers/deformation.pdf and Hawkins http://arxiv.org/abs/0706.2946 – Alexander Chervov Feb 14 '16 at 09:41
  • Sorry, but I did not understand your previous comment. In what kind of quantization are you interested? Every symplectic manifold can be quantized using symplectic groupoids (because the associated Lie algebroid of the symplectic manifold is integrable). Furthermore, strict deformation quantization is the most general non-perturbative quantization process that I know. By the way, I could not find the no-go theorem that you're referring to in Rieffel's paper (where's it?). – user40276 Feb 15 '16 at 09:00
  • @user40276 Rieffel - Example 9 end of page 222 the very end of paper - before ref. list – Alexander Chervov Feb 15 '16 at 10:33
  • @user40276 "Every symplectic manifold can be quantized using symplectic groupoids " in what sense in can be quantize ? As far as I heard this quantization is not even deformation quantization , but some approximation to it: http://arxiv.org/abs/math/0312380 . Although I am not expert - can you clarify in what sense it "quantizes" ? – Alexander Chervov Feb 15 '16 at 10:37
  • @user40276 "In what kind of quantization are you interested? " you will be surpised, but I think that nobody knows how to marriage analysis and quantization in the right way - or may be someone knows like Nick Landsman but it is not widely accepted. There are several properties which I would expect from the "correct quantization" and several examples where we think we know the answer - like NC tori - without knowledge what is correct non-pertrubative quantization in general ... – Alexander Chervov Feb 15 '16 at 10:42
  • @user40276 See http://mathoverflow.net/questions/231072/quantization-of-s2-as-c-algebra - I do not know what is correct "non-pertrubative" quantization in general, but in that particular example it must give that answer - that is I am sure. – Alexander Chervov Feb 15 '16 at 10:44
  • As I understand, there are several ways of quantizing a Poisson manifold $(X, \pi)$ using symplectic groupies. The process is usually done by associating to $X$ the Lie algebroid $T^X$ wit anchor $\pi^{#}$ and bracket $[df, dg] = d {f, g }$. This Lie algebroid is always locally integrable to a symplectic groupoid (that is, even if the Weinstein groupoid is not smooth, locally there's an integration which have a symplectic form). For the case of symplectic manifolds, $T^X$ is isomorphic to $TX$ as a Lie algebroid and, hence, the pair groupoid $X \times X$ – user40276 Feb 15 '16 at 12:13
  • @user40276 I guess that not a quantization we would expect as "correct quantization" as that paper by Cattaneo analyzes ... – Alexander Chervov Feb 15 '16 at 12:21
  • … or the fundamental groupoid $\Pi_1 (X)$ (which is source simply connected) integrates it. Now, the quantization is usually done by picking compact supported complex valued functions on the groupoid together with convolution as the $C^*$ algebra structure. There are further refinements of this procedure by picking instead sections of a suitable polarized line bundle over the groupoid. This last step is essentially a reformulation of geometric quantization in the groupoid context (taking the groupoid multiplication into account). See, for instance, http://arxiv.org/abs/math/0612363 and – user40276 Feb 15 '16 at 12:22
  • … http://arxiv.org/pdf/math-ph/0001005v2.pdf . Note that the latter defines strict deformation quantization in a slightly different way. – user40276 Feb 15 '16 at 12:23
  • @user40276 deformation quantization is very good , but it does not give analysis , "correct" analytical quantizatin should agree with deformation quantization but add some more - C^* or whatever analytical structure ... – Alexander Chervov Feb 15 '16 at 12:23
  • About, Cattaneo's paper, I don't have time to check it carefully now, however it's was clear that he uses a formal integration instead of the real one. They make it clear that they're quantizing even non-integrable Lie algebroids, therefore it's expected that the quantization will be strictly perturbative (over the formal power series). – user40276 Feb 15 '16 at 12:30
  • I still cannot understand what you mean by "correct" analytical quantization in general. And, yes, I have seen your particular example of the sphere together with the volume form and the consequences of the no-go theorem you mentioned. I cannot see how your question is answerable if you don't have a process of quantization in mind for general symplectic manifolds. – user40276 Feb 15 '16 at 12:44
  • @user40276 I just beleive "correct" quantization is unique ! that is why the answer would be unique, even if I do know the correct procedure... So it is reasonable to ask about the properties of that "unknown" procedure if we believe that it exists and unique... – Alexander Chervov Feb 15 '16 at 12:48
  • So , let me try to understand. I truly want to understand what do you mean by correct quantization. Even not knowing the correct procedure, do you know what properties it should have? In other words, how can you classify if a quantization is the correct one or not? If so, could list these properties explicitly? – user40276 Feb 15 '16 at 20:28
  • @user40276 you are welcome for questions. Yes there are some properties which are expected to hold true. Probably the main property: "agreemet with deformation quantization" - I mean any quantization should give rise to family of algebras depending on "h", as a linear space these algebras should be of the same size as original algebra, so using some identification of vector spaces we "can" get star product depending on "h" - this star product should be equivalent to Kontsevich's ones. Power of Kontsevich theorem is that he establish bijection: Poisson-StarProduct. – Alexander Chervov Feb 15 '16 at 21:20
  • @user40276 there are other properties, but may be they follow from the previous one. Properties: 1) in well-known examples like R^2n, g^*, NC-torus we should get the same as we know 2) Hilbert space representation if \omega is INTEGRAL cohomology class and dimention of that Hilbert space shoudl be equal to Fedosov's index formula – Alexander Chervov Feb 15 '16 at 21:24
  • @user40276 there are other properties like that existence of Trace (mentioned in main body of question), quantization of Lagrangian submanifolds, probably symplectomorphisms should be quantized somehow, some functoriality ... – Alexander Chervov Feb 15 '16 at 21:27
  • Just a comment. In the case you linked about the quantization of the sphere, I think you can achieve this by quantizing (in the way I mentioned above) the cotangent groupoid $T^G \xrightarrow{\rightarrow} \mathfrak{g}^$ and, then, taking the orbits. Well, this is essentially what you have suggest, but formulated in the quantization procedure I've suggested. – user40276 Feb 18 '16 at 19:08
  • @user40276 thank you ! At the moment I am afraid that even in the case of S^2 desired quantization does not exists :( because it seems generators x_i which form su(2), but su(2) seems does not have appropriate infinite-dime irep - I am not sure - probably I will write separate MO question on it... – Alexander Chervov Feb 19 '16 at 07:11
  • @user40276 I know this is an old thread, but for clarity the geometric quantization of a Poisson manifold is not given by the convolution algebra of the integration of the Lie algebroid, it is given by the convolution algebra of a polarized groupoid, which is different. Still, this procedure cannot always be done and it doesn't come with a quantization map. In particular, in general there is no known way of obtaining a deformation quantization from a geometric quantization, and as far as I know the answer to this question is unknown. – Josh Lackman Mar 14 '23 at 20:38

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