Talk:Symplectic manifold

Expansion

The following is an excerpt from the last version of this page which I thought would be better moved to the talk page. -- Fropuff 06:27, 2004 Feb 24 (UTC)

The relation between symplectic geometry and Hamiltonian mechanics should explained in more detail.

Symplectic capcities should be mentioned.

Examples would be nice. Why are these things studied? I suspect because of physics?

Moved this here from the article, and wikified it, for more convenient discussion:

Note that Emil Artin (founder of a german school of mathematicians in the Bourbaki style) already very early contributed to symplectic structures, which should be given in a more modern version than that at the top of this article. A symplectic vector space is a real vectorspace with a nondegenerate bilinear form, which is skew. This implies even-dimensionality. There are implications for multilinear algebra, (Weyl algebras, as opposed to Clifford algebras, where the bilinear form is symmetric), differential geometry (symplectic manifolds) and Physics (Poisson brackets in classical mechanics, canonical commutation relations in quantum mechanics). Look at http://www.EarningCharts.NET/ipm/ipmSympl.htm for more information. Hannes Tilgner

So, Artin was actually Austrian ... he wrote on geometric algebra in a quite broad sense. How much of this belongs here? User:Fropuff and I have already chewed the fat about linear symplectic space = symplectic vector space. Symplectic manifold could contain allusions to many of the mentioned things. Perhaps a bigger Related Articles section?

Charles Matthews 08:46, 5 May 2004 (UTC)[reply]

Hamiltonian Mechanics

We are told (in the section on Hamiltonian Mechanics IIRC) that it is possible to reach Hamiltonian mechanics from symplectic spaces directly, without going through Lagrangian methods.

This article (and several others in related areas of symplectic topology) does not indicate (to me!) how this is possible - at some stage a physicist needs to see some correspondence with forces and particles however abstract, since at the last Newton's Laws or their generalisation are experimental.

Bob aka Linuxlad 14:01, 9 Nov 2004 (UTC)

Basically with the background 2-form in place, the Hamiltonian H gives rise to a vector field and so the dynamics. Not really done with mirrors - the geometry is relatively simple. There is a sense in which the Lagrangian and Hamiltonian approaches are dual (not that I'd want to be pinned down, but the words Legendre transformation come to mind). So there ought to be an alternate way of looking at it. I suppose, roughly speaking, it's whether conservation of energy is expressed by a family of contours, or a family of orthogonal contours which expresses how your toboggan goes downhill. Charles Matthews 16:00, 9 Nov 2004 (UTC)

nondegenerate

For non-experts it might not be clear that a 2-form is nondegenerate iff it is seen as a bilinear form $\omega _{x}:T_{x}M\times T_{x}M\to \mathbb {R}$ pointwise. The reference explains only nondegeneracy in the linear setting. Hottiger 22:29, 14 April 2006 (UTC)[reply]

Is this why it is antisymmetric? The definition employs skew symmetry without transparently requiring skew symmetry, it would be great if that could be fixed. 150.203.48.23 (talk) 05:19, 10 September 2008 (UTC)[reply]

The requirement appears in the fact that a symplectic structure is a differential 2-form, and these are always antisymmetric. Orthografer (talk) 12:53, 10 September 2008 (UTC)[reply]

Why is that part of the definition not simply omitted? --pred (talk) 23:09, 3 December 2009 (UTC)[reply]

Kahler manifold

The sentence "A symplectic manifold endowed with a metric that is compatible with the symplectic form is a Kähler manifold" in the "Special cases and generalizations" section is not exactly correct; a Kahler manifold requires that the almost complex structure obtained from the metric and symplectic form be integrable. This should be stated somewhere, somehow, or Kahler should be changed to almost-Kahler. What sounds like the best course of action? 136.152.180.51 23:16, 19 April 2007 (UTC)[reply]

Hope this satisfies. Orthografer 06:30, 20 April 2007 (UTC)[reply]

WikiProject class rating

This article was automatically assessed because at least one WikiProject had rated the article as start, and the rating on other projects was brought up to start class. BetacommandBot 10:04, 10 November 2007 (UTC)[reply]

Recent additive descriptions

I appreciate the recent descriptions, in particular, about motivation. Thanks!--Enyokoyama (talk) 11:31, 24 March 2013 (UTC)[reply]

A symbol needs to be defined

In the article section titled Motivation, I see the following sentence:

"So we require a linear map TM → T*M, or equivalently, an element of T*M ⊗ T*M."

The (operator?) T is not defined or described. Is that the symplectic 2-form alluded to above? I'm hoping someone can prepend something like, "Given a real manifold M and a symplectic form T..." (or whatever T actually is!)

Thank you. Dratman (talk) 05:31, 14 March 2017 (UTC)[reply]

Done. Its the tangent manifold. 172.58.187.254 (talk) 01:07, 15 August 2021 (UTC)[reply]

Another definition of isotropic

I have seen elsewhere a riemannian manifold being called isotropic if there is an isometry that rotates an arbitrary angle around each point. If anyone finds a source, it would be nice to add a disambiguation to distinguish the two meanings. Madhing (talk) 17:01, 15 September 2024 (UTC)[reply]