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- Discussion Type
- discussion topicexpectation value
- Category Latest Changes
- Started by Urs
- Comments 2
- Last comment by Urs
- Last Active 25 minutes ago

I wanted to be able to point to

*expectation value*without the link being broken. So I added a sentence there, but nothing more for the moment.

- Discussion Type
- discussion topicquantum probability space
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active 47 minutes ago

I started a bare minimum at

*quantum probability*(redirecting*noncommutative probability space*etc.)Some entries have long been secretly referencing such an entry, and I have cross-linked accordingly, for instance from

*von Neumann algebra*and*quantum computing*.I had the feeling somewhere we already had a detailed account of probability theory dually in terms of von NNeumann algebras, but if we do I didn’t find it(?)

- Discussion Type
- discussion topicdiffiety
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active 4 hours ago

I gave

*diffiety*more of an Idea-section

- Discussion Type
- discussion topicmultiplicative disjunction
- Category Latest Changes
- Started by Mike Shulman
- Comments 5
- Last comment by David_Corfield
- Last Active 6 hours ago

Created multiplicative disjunction.

- Discussion Type
- discussion topicCatalan number
- Category Latest Changes
- Started by zskoda
- Comments 4
- Last comment by Urs
- Last Active 3 days ago

Few words added at Catalan number.

- Discussion Type
- discussion topicmicroformal morphism
- Category Latest Changes
- Started by zskoda
- Comments 1
- Last comment by zskoda
- Last Active 4 days ago

microformal morphism a la Theodore Voronov.

- Discussion Type
- discussion topicMorse potential
- Category Latest Changes
- Started by zskoda
- Comments 1
- Last comment by zskoda
- Last Active 4 days ago

Stub for Morse potential.

- Discussion Type
- discussion topicWeyl calculus and quantization
- Category Latest Changes
- Started by zskoda
- Comments 3
- Last comment by zskoda
- Last Active 4 days ago

New stub Weyl functional calculus redirecting also Weyl quantization. I would like to see ref.

- Lars Hörmander,
*The weyl calculus of pseudo-differential operators*, Comm. Pure Appl. Math.**32**, 3, 359–443, May 1979, doi,

but have no access to it (can anybody help?). I also added a sentence at Idea section of functional calculus reflecting that the previous definition there is not fitting functional calculi in the context of quantization, including Weyl’s case. One should do this generality discussion more carefully. the previous definition said that the functional calculus needs to be a homomorphism (from ordinary functions to operator functions). This is true for the functional calculus described in the entry, but not for the wider usage of the phrase like in Weyl functional calculus. Maybe we can resolve this in a better way.

- Lars Hörmander,

- Discussion Type
- discussion topicA First Idea of Quantum Fields
- Category Latest Changes
- Started by Urs
- Comments 49
- Last comment by Urs
- Last Active 5 days ago

At

*field (physics)*I am beginning to write an actual introduction to the topic, now in a new section titled “A first idea of quantum fields”.This means to introduce the concept with precise detail, but in a simple context (trivial and bosonic field bundles over Minkowski spacetime, perturbatively quantized) that allows to get a quick idea of the idea of the concept of (quantum) fields as such, without being distracted by other details.

So far I made it up to the derivation of the EOMs. Discussion of (deformation) quantization is to follow (maybe by tonight, depending on how much trouble I have with the trains) and I plan to sprinkle in the detailed example from

*scalar field*in parallel with the abstract discussion.

- Discussion Type
- discussion topiccommutative operad
- Category Latest Changes
- Started by Urs
- Comments 3
- Last comment by Urs
- Last Active 5 days ago

added a minimum of words at

*commutative operad*(the entry remains a stub)

- Discussion Type
- discussion topictheory of algebraically closed fields
- Category Latest Changes
- Started by Todd_Trimble
- Comments 2
- Last comment by Todd_Trimble
- Last Active 5 days ago

I’ve been entering corrections into the article theory of algebraically closed fields in response to a chat room discussion, but see that the \underbrace command doesn’t work as expected (see the Definition section). What’s the right way to write what is obviously wanted here?

- Discussion Type
- discussion topicdifferential graded-graded commutative algebra
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active 5 days ago

added the case of dgc superalgebras (here) and expanded the list of examples accordingly

- Discussion Type
- discussion topicduality in physics
- Category Latest Changes
- Started by Urs
- Comments 66
- Last comment by David_Corfield
- Last Active 6 days ago

needed to be able to point to

*duality in physics*, so I created an entry. For the moment just a glorified redirect.

- Discussion Type
- discussion topictransfor
- Category Latest Changes
- Started by Mike Shulman
- Comments 3
- Last comment by Mike Shulman
- Last Active 6 days ago

I moved (n,k)-transformation to transfor, as seemed to be agreed upon by those who spoke up in the discussion there.

- Discussion Type
- discussion topicstate on a star-algebra
- Category Latest Changes
- Started by Urs
- Comments 2
- Last comment by Urs
- Last Active 7 days ago

I have expanded the Idea section at

*state on a star-algebra*and added a bunch of references.The entry used to be called “state on an operator algebra”, but I renamed it (keeping the redirect) because part of the whole point of the definition is that it makes sense without necessarily having represented the “abstract” star-algebra as a C*-algebra of linear operators.

- Discussion Type
- discussion topicstring theory FAQ
- Category Latest Changes
- Started by Urs
- Comments 71
- Last comment by David_Corfield
- Last Active Dec 2nd 2017

added to

*string theory FAQ*two new paragraphs:Prompted by the MO discussion

- Discussion Type
- discussion topicevolutionary derivative
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Nov 30th 2017

created

*evolutionary derivative*(what Olver calls the “Fréchet derivative of tuples of differential functions”) with basic definitions and properties

- Discussion Type
- discussion topichydrogen atom
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Nov 30th 2017

I created a stub for

*hydrogen atom*, for the moment just so as to record a reference. In the course of this I ended up touching or creating a few related entries, such as*proton*,*neutron*,*nucleus (physics)*,*element*,*periodic table of the elements*. But all of these remain stubs at the moment.

- Discussion Type
- discussion topiccausal propagator
- Category Latest Changes
- Started by Urs
- Comments 3
- Last comment by Urs
- Last Active Nov 28th 2017

Gave some content to

*causal propagator*: an Idea-section and the main formulas for the causal propagator on Minkowski spacetime.

- Discussion Type
- discussion topicconvolution product of distributions
- Category Latest Changes
- Started by Urs
- Comments 2
- Last comment by Urs
- Last Active Nov 28th 2017

started some minimum at

*convolution product of distributions*

- Discussion Type
- discussion topicpositive and negative types
- Category Latest Changes
- Started by Mike Shulman
- Comments 1
- Last comment by Mike Shulman
- Last Active Nov 27th 2017

At positive type we have

In denotational semantics, positive types behave well with respect to “call-by-value” and other eager evaluation strategies.

and dually at negative type we have

In denotational semantics, negative types behave well with respect to “call-by-name” and other lazy evaluation strategies.

This doesn’t seem right to me; don’t evaluation strategies belong to

*operational*semantics?

- Discussion Type
- discussion topicCauchy principal value
- Category Latest Changes
- Started by Urs
- Comments 6
- Last comment by Urs
- Last Active Nov 27th 2017

I want to be adding some details to

*Cauchy principal value*. What’s a good reference? Say for the proof that up to addition of a delta-distribution, $f(x) = pv\left( \frac{1}{x}\right)$ is the unique distributional solution to $x f = 1$?

- Discussion Type
- discussion topicquantomorphism group
- Category Latest Changes
- Started by Urs
- Comments 5
- Last comment by Urs
- Last Active Nov 27th 2017

started

*quantomorphism group*

- Discussion Type
- discussion topicfield
- Category Latest Changes
- Started by Mike Shulman
- Comments 3
- Last comment by Mike Shulman
- Last Active Nov 26th 2017

I added to field a mention of some other constructive variants of the definition, with a couple more references.

- Discussion Type
- discussion topicpi
- Category Latest Changes
- Started by Todd_Trimble
- Comments 2
- Last comment by Urs
- Last Active Nov 26th 2017

I made a note of the fact that simple high-school algebra applied to the “Archimdean definition” of pi leads to the Vieta product formula.

- Discussion Type
- discussion topicapartness relation
- Category Latest Changes
- Started by Mike Shulman
- Comments 15
- Last comment by Mike Shulman
- Last Active Nov 26th 2017

apartness relation says

The negation of an apartness relation is an equivalence relation. (The converse of this is equivalent to excluded middle.)

But it seems to me that the converse (“the negation of an equivalence relation is an apartness relation”) only requires de Morgan’s law. If $\approx$ is an equivalence relation, then certainly $\neg\neg(x\approx x)$ and $\neg (x\approx y) \to \neg(y\approx x)$, so the only thing to worry about is comparison. If $\neg (x\approx z)$, then contraposing transitivity gives $\neg (x\approx y \wedge y\approx z)$, which by de Morgan gives $\neg (x\approx y) \vee \neg (y\approx z)$.

- Discussion Type
- discussion topiclocal ring
- Category Latest Changes
- Started by IngoBlechschmidt
- Comments 3
- Last comment by Mike Shulman
- Last Active Nov 26th 2017

Added to

*local ring*a short remark on that the spectrum of a ring is local if and only if the ring is local.

- Discussion Type
- discussion topicconservative functor
- Category Latest Changes
- Started by Urs
- Comments 22
- Last comment by Mike Shulman
- Last Active Nov 26th 2017

added to

*conservative functor*the proposition saying that pullback along strong epis is a conservative functor (if strong epis pull back).How about the $\infty$-version?

- Discussion Type
- discussion topicBessel function
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Nov 25th 2017

- Discussion Type
- discussion topicrapidity
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Nov 24th 2017

created

*rapidity*, just enough to serve as a link from the computation of the*singular support of the causal propagator*