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1. • CommentRowNumber1.
   • CommentAuthorUrs
   • CommentTimeMay 13th 2021
   • (edited Oct 30th 2022)
   • PermaLink
   Author: Urs
   Format: MarkdownItexAt *[[computational trilogy]]* I made explicit the quantum version -- [here](https://ncatlab.org/nlab/show/computational+trilogy#QuantumParametrized). As with the classical trilogy, it's evident once you think about it.

   At computational trilogy I made explicit the quantum version – here.

   As with the classical trilogy, it’s evident once you think about it.

2. • CommentRowNumber2.
   • CommentAuthorDavid_Corfield
   • CommentTimeMay 13th 2021
   • PermaLink
   Author: David_Corfield
   Format: MarkdownItexCan we think of anything as neat as: > 1. A [[proof]] of a [[proposition]]. (In [[logic]].) > 2. A [[program]] with output some [[type]]. (In [[type theory]] and [[computer science]].) > 3. A [[generalized element]] of an [[object]]. (In [[category theory]].) Something to do with your [[propositions as projections]] idea?

   Can we think of anything as neat as:

   1. A proof of a proposition. (In logic.)

   2. A program with output some type. (In type theory and computer science.)

   3. A generalized element of an object. (In category theory.)

   Something to do with your propositions as projections idea?

3. • CommentRowNumber3.
   • CommentAuthorUrs
   • CommentTimeMay 13th 2021
   • PermaLink
   Author: Urs
   Format: MarkdownItexYes, it's exactly the same dictionary. Just that the types/objects/spaces in the fibers are now linear. (And we notice that for "generalized element" we may equivalently say "cocycle" in all cases: classical, parameterized, quantum.)

   Yes, it’s exactly the same dictionary. Just that the types/objects/spaces in the fibers are now linear.

   (And we notice that for “generalized element” we may equivalently say “cocycle” in all cases: classical, parameterized, quantum.)

4. • CommentRowNumber4.
   • CommentAuthorUrs
   • CommentTimeMay 14th 2021
   • (edited May 14th 2021)
   • PermaLink
   Author: Urs
   Format: MarkdownItexIn fact, without the parametrization/control-aspect, the quantum trilogy is already Melliès's main point, on his [p. 4](https://hal.archives-ouvertes.fr/hal-00154243/document#page=5) -- I have tried to bring that out more clearly in the entry now, [here](https://ncatlab.org/nlab/show/computational+trilogy#QuantumPlain)

   In fact, without the parametrization/control-aspect, the quantum trilogy is already Melliès’s main point, on his p. 4 – I have tried to bring that out more clearly in the entry now, here

5. • CommentRowNumber5.
   • CommentAuthorDavid_Corfield
   • CommentTimeMay 14th 2021
   • PermaLink
   Author: David_Corfield
   Format: MarkdownItexPerhaps a little speculative for this time in the morning, but if we follow Susskind in * _Copenhagen vs Everett, Teleportation, and ER=EPR Leonard Susskind_, ([arXiv:1604.02589](https://arxiv.org/abs/1604.02589)) > The universe is filled with subsystems, any one of which can play the role of observer. There is no place in the laws of quantum mechanics for wave function collapse; the only thing that happens is that the overall wave function evolves unitarily and becomes more and more entangled. The universe is an immensely complicated network of entangled subsystems, and only in some approximation can we single out a particular subsystem as THE OBSERVER. is there are quantum trilogy which is not classically controlled? Or is it that just 'quantum plain'?

   Perhaps a little speculative for this time in the morning, but if we follow Susskind in

   • Copenhagen vs Everett, Teleportation, and ER=EPR Leonard Susskind, (arXiv:1604.02589)

   The universe is filled with subsystems, any one of which can play the role of observer. There is no place in the laws of quantum mechanics for wave function collapse; the only thing that happens is that the overall wave function evolves unitarily and becomes more and more entangled. The universe is an immensely complicated network of entangled subsystems, and only in some approximation can we single out a particular subsystem as THE OBSERVER.

   is there are quantum trilogy which is not classically controlled? Or is it that just ’quantum plain’?

6. • CommentRowNumber6.
   • CommentAuthorUrs
   • CommentTimeMay 14th 2021
   • PermaLink
   Author: Urs
   Format: MarkdownItexLet me lay out the picture that I have at the moment, also so that you see where [[schreiber:Fundamental weight systems are quantum states|you fit in]]: *** **Hypothesis H, full quantum version**: For * a $G$-orbi $\mathbb{R}^{10,1\vert \mathbf{32}}$-fold $\mathcal{X}$ (spacetime) * with geometric torsion-free $\mathrm{Spin}(10,1)$-structure ([i.e.](https://www.physicsforums.com/insights/11d-gravity-just-torsion-constraint/) field of super-gravity) * further lifted to tangential $\mathrm{Sp}(2)$-structure $\tau$ (anomaly cancellation), * consider the [[cocycle space]] $\mathbf{\pi}_G^\tau(\mathcal{X})$ of $\tau$-twisted equivariant differential 4-Cohomotopy ([[schreiber:Hypothesis H|i.e.]] the C-field configuration [[G-space]]) * and then the $G$-equivariant $E$-cohomology cocycle space of its loop space $\mathbf{E}^\bullet_G\big( \Omega \mathbf{\pi}_G^\tau(\mathcal{X}) \big)$ (quantum states) * regarded as a $G$-equivariant spectrum (e.g. with $E = H\mathbb{C}$ and $\mathcal{X}$ a $D6 \perp D8$ spacetime as in [[schreiber:Differential Cohomotopy implies intersecting brane observables|SS19]] this has homotopy groups the [[schreiber:Fundamental weight systems are quantum states|weight systems on horizontal chord diagrams]]) * hence as a [[spectral Mackey functor]] * hence as a parameterized spectrum (over $G$-sets) equipped with consistent orientation for pull/push transformations * hence as a cohomological QFT-via-secondary-integral-transforms in the sense of Sec. 7 of [[schreiber:Quantization via Linear homotopy types|Quantization via Linear homotopy types]]. Unwinding the definitions, this QFT encodes * quantum operations between quantum states of C-field configurations * associated with $H$-fixed loci of the original spacetime orbifold $\mathcal{X}$. * But since these loci are conical black brane loci (as in [[schreiber:Equivariant homotopy and super M-branes|HSS 18]]) in the spacetime, * we see that we have a "classically controlled quantum system" where the classical control parameter says where in a holographic system we are: * in the bulk ($1$-fixed locus) * or on a brane ($H$-fixed locus) * and if so on which of possibly several intersecting ones (choice of subgroup $H \subset G$). *** Now take this mathematical picture and compare to the current folklore in string theory. Within the large hand-waving error bars of the latter, this could match well, I think.

   Let me lay out the picture that I have at the moment, also so that you see where you fit in:

   ---

   Hypothesis H, full quantum version:

   For

   • a $G$-orbi $\mathbb{R}^{10,1\vert \mathbf{32}}$-fold $\mathcal{X}$ (spacetime)

   • with geometric torsion-free $\mathrm{Spin}(10,1)$-structure (i.e. field of super-gravity)

   • further lifted to tangential $\mathrm{Sp}(2)$-structure $\tau$ (anomaly cancellation),

   • consider the cocycle space $\mathbf{\pi}_G^\tau(\mathcal{X})$ of $\tau$-twisted equivariant differential 4-Cohomotopy (i.e. the C-field configuration G-space)

   • and then the $G$-equivariant $E$-cohomology cocycle space of its loop space $\mathbf{E}^\bullet_G\big( \Omega \mathbf{\pi}_G^\tau(\mathcal{X}) \big)$ (quantum states)

   • regarded as a $G$-equivariant spectrum (e.g. with $E = H\mathbb{C}$ and $\mathcal{X}$ a $D6 \perp D8$ spacetime as in SS19 this has homotopy groups the weight systems on horizontal chord diagrams)

     • hence as a spectral Mackey functor

     • hence as a parameterized spectrum (over $G$-sets) equipped with consistent orientation for pull/push transformations

     • hence as a cohomological QFT-via-secondary-integral-transforms in the sense of Sec. 7 of Quantization via Linear homotopy types.

   Unwinding the definitions, this QFT encodes

   • quantum operations between quantum states of C-field configurations

   • associated with $H$-fixed loci of the original spacetime orbifold $\mathcal{X}$.

   • But since these loci are conical black brane loci (as in HSS 18) in the spacetime,

   • we see that we have a “classically controlled quantum system” where the classical control parameter says where in a holographic system we are:

     • in the bulk ($1$-fixed locus)

     • or on a brane ($H$-fixed locus)

     • and if so on which of possibly several intersecting ones (choice of subgroup $H \subset G$).

   ---

   Now take this mathematical picture and compare to the current folklore in string theory. Within the large hand-waving error bars of the latter, this could match well, I think.

7. • CommentRowNumber7.
   • CommentAuthorDavid_Corfield
   • CommentTimeMay 16th 2021
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   Author: David_Corfield
   Format: MarkdownItexQuite a vision! > we see that we have a “classically controlled quantum system” where the classical control parameter says where in a holographic system we are I think this is the part I've heard least about before. I remember you giving an abstract general nPOV on holography, way back. Yes, here at [[holographic principle of higher category theory]]. Untouched for nearly a decade.

   Quite a vision!

   we see that we have a “classically controlled quantum system” where the classical control parameter says where in a holographic system we are

   I think this is the part I’ve heard least about before.

   I remember you giving an abstract general nPOV on holography, way back. Yes, here at holographic principle of higher category theory. Untouched for nearly a decade.

8. • CommentRowNumber8.
   • CommentAuthorDavid_Corfield
   • CommentTimeOct 30th 2022
   • PermaLink
   Author: David_Corfield
   Format: MarkdownItexCould one say then that [[quantum computation]] as well as any experimental observation in quantum physics, such as what occurs at the LHC, is all covered by this concept of “classically controlled quantum system” as in #6? Perhaps this is the direction [[Schreiber:Physics of the Observer]] would have tended in, had it been funded.

   Could one say then that quantum computation as well as any experimental observation in quantum physics, such as what occurs at the LHC, is all covered by this concept of “classically controlled quantum system” as in #6?

   Perhaps this is the direction Physics of the Observer (schreiber) would have tended in, had it been funded.

9. • CommentRowNumber9.
   • CommentAuthorUrs
   • CommentTimeOct 30th 2022
   • (edited Oct 30th 2022)
   • PermaLink
   Author: Urs
   Format: MarkdownItex> Could one say then that [[quantum computation]] as well as any experimental observation in quantum physics, such as what occurs at the LHC, is all covered by this concept of "classically controlled quantum system" Certainly quantum computation and all "quantum protocols". I have a new page with a list of claims, here: *[[schreiber:QS]]* > as in #6? The comment in #6 above was about a different aspect, namely the aspect of holography. We hope to come back to this when some more practical details have been laid out. > Perhaps this is the direction [[Schreiber:Physics of the Observer]] would have tended in, had it been funded. I had had the feeling that we "just" need to see linear projections onto eigenstates arise as categorical semantics of an evident logical construct on linear types in order for all quantum mystery to dissolve. It was after a discussion with David J. M. and Mitchell R. over lunch some weeks back that I suddently saw ([here](https://nforum.ncatlab.org/discussion/6352/necessity-and-possibility/?Focus=103236#Comment_103236)) that the collapse projections are right there in the necessity counit on dependent linear types. In hindsight it seems so obvious now! (Yoneda-lemma style)

   Could one say then that quantum computation as well as any experimental observation in quantum physics, such as what occurs at the LHC, is all covered by this concept of “classically controlled quantum system”

   Certainly quantum computation and all “quantum protocols”. I have a new page with a list of claims, here: QS (schreiber)

   as in #6?

   The comment in #6 above was about a different aspect, namely the aspect of holography. We hope to come back to this when some more practical details have been laid out.

   Perhaps this is the direction Physics of the Observer (schreiber) would have tended in, had it been funded.

   I had had the feeling that we “just” need to see linear projections onto eigenstates arise as categorical semantics of an evident logical construct on linear types in order for all quantum mystery to dissolve. It was after a discussion with David J. M. and Mitchell R. over lunch some weeks back that I suddently saw (here) that the collapse projections are right there in the necessity counit on dependent linear types. In hindsight it seems so obvious now! (Yoneda-lemma style)

10. • CommentRowNumber10.
    • CommentAuthorDavid_Corfield
    • CommentTimeOct 31st 2022
    • PermaLink
    Author: David_Corfield
    Format: MarkdownItexThis looks very interesting. Just the kind of thing Friedman would expect if quantum physics is to be properly integrated philosophically. He himself point to quantum logic as the kind of advance needed. It seems we had to wait several decades for linear HoTT. I was just thinking from #6, where you wrote > we see that we have a “classically controlled quantum system” where the classical control parameter says where in a holographic system we are, that when we talked once a while ago about how a theory of quantum gravity by itself has no notion of an observer, that any account of observation of the world must be framed with some kind of classical interface.

    This looks very interesting. Just the kind of thing Friedman would expect if quantum physics is to be properly integrated philosophically. He himself point to quantum logic as the kind of advance needed. It seems we had to wait several decades for linear HoTT.

    I was just thinking from #6, where you wrote

    we see that we have a “classically controlled quantum system” where the classical control parameter says where in a holographic system we are,

    that when we talked once a while ago about how a theory of quantum gravity by itself has no notion of an observer, that any account of observation of the world must be framed with some kind of classical interface.