It has become clear that M^{8}H duality generalizes and there is a connection with the twistorialization at the level of H.
Spacetime surfaces as images of associative surfaces in M^{8}
M^{8}H duality would provide an explicit construction of spacetime surfaces as algebraic surfaces with an associative normal space (see this, this, and this). M^{8} picture codes spacetime surface by a real polynomial with rational coefficients. One cannot exclude coefficients in an extension of rationals and also analytic functions with rational or algebraic coefficients can be considered as well as polynomials of infinite degree obtained by repeated iteration giving rise algebraic numbers as extension and continuum or roots as limits of roots.
M^{8}H duality maps these solutions to H and one can consider several forms of this map. The weak form of the duality relies on holography mapping only 3D or even 2D data to H and the strongest form maps entire spacetime surfaces to H. The twistor lift of TGD allows to identify the spacetime surfaces in H as base spaces of 6D surfaces representing the twistor space of spacetime surface as an S^{2} bundle in the product of twistor spaces of M^{4} and CP_{2}. These twistor spaces must have Kähler structure and only the twistor spaces of M^{4} and CP_{2} have it so that TGD is unique also mathematically.
An interesting question relates to the possibility that also 6D commutative spacetime surfaces could be allowed. The normal space of the spacetime surface would be a commutative subspace of M^{8}_{c} and therefore 2D. Commutative spacetime would be a 6D surface X^{6} in M^{8}.
This raises the following question: Could the inverse image of the 6D twistorspace of 4D spacetime surface X^{4} so that X^{6} would be M^{8} analog of twistor lift? This requires that X^{6}⊂ M^{8}_{c} has the structure of an S^{2} bundle and there exists a bundle projection X^{6}→ X^{4}.
The normal space of an associative spacetime surface actually contains this kind of commutative normal space! Its existence guarantees that the normal space of X^{4} corresponds to a point of CP_{2}. Could one obtain the M^{8}_{c} analog of the twistor space and the bundle bundle projection X^{6}→ X^{4} just by dropping the condition of associativity. Spacetime surface would be a 4surface obtained by adding the associativity condition.
One can go even further and consider 7D surfaces of M^{8} with real
and therefore wellordered normal space. This would suggest
dimensional hierarchy: 7→ 6→ 4.
This leads to a possible interpretation of twistor lift of TGD at the level of M^{8} and also about generalization of M^{8}H correspondence to the level of twistor lift. Also the generalization of twistor space to a 7D space is suggestive. The following arguments representa vision about "how it must be" that emerged during the writing of this article and there are a lot of details to be checked.
Commutative 6surfaces and twistorial generalization of M^{8}H correspondence
Consider first the twistorial generalization of M^{8}H correspondence.
 The complex 6D surface X^{6}_{c}⊂ M^{8}_{c} has commutative normal space and thus corresponds to complexified octonionic complex numbers (z_{1}+z_{2}I). X^{6}_{c} has real dimension 12 just as the product T(M^{4})× T(CP_{2}) of 6D twistor spaces of M^{4} and CP_{2}. It has a bundle structure with a complex 4D base space which is mapped M^{4}× CP_{2} by M^{8}H duality. The fiber has complex dimension 2 and corresponds to the dimension for the product of twistor spheres of the twistor spaces of M^{4} and CP_{2}.
 This suggests that M^{8}H duality generalizes so that it maps X^{6}_{c} ⊂ M^{8}_{c} to T(M^{4})× T(CP_{2}) . It would map the point of X^{6}_{c} to its real projection identified as a point of T(M^{4}). "Real" means here that the complex continuation of the number theoretical norm squared for octonions is real so that the components of M^{8} point are either real or imaginary with respect to the commuting imaginary unit i. The complex 6D tangent space of X^{6}_{c} would be mapped to a point of T(CP_{2}).
The beauty of this picture would be that the entire complex 6D surface would carry physical information mapped directly to the twistor space.
One can try to guess the form of the map of X^{6}_{c} to the product T(M^{4})× T(CP_{2}).
The surfaces X^{6} have local normal space basis 1⊕ e_{7} . The problem is that this space is invariant under SU(3) for M^{8}H for CP_{2}. Could one choose the 2D normal space to be something else without losing the duality. If e_{7} and e_{1} are permuted, the tangent space basis vector transforms by a phase phase factor under U(1)× U(1). The 4D subbasis of normal space would be now (1,e_{1},e_{7},e_{2}). This does not affect the M^{8}Hduality map to CP_{2}. The 6D space of normal spaces would be the flag manifold SU(2)/U(1)times U(1), which is nothing but the twistor space T(CP_{2}).
What about the twistorial counterpart for the map of M^{4}⊂ M^{8}→ M^{4}⊂ M^{8}? One can consider several options.
 At the level of M^{8}, M^{4} is replaced by M^{6} at least locally in the sense that one can use M^{6} coordinates for the point of X^{6}. Can one identify the M^{6} image of this space as the projective space C^{4}/C_{×} obtained from C^{4} by dividing with complex scalings? This would give the twistor space CP_{3}= SU(4)/U(3) of M^{4}. This is not obvious since one has (complexified) octonions rather than C^{4} or its hypercomplex analog. This would be analogous to using several (4) coordinate charts glued together as in the case of sphere CP_{1}.
 If M^{8}H duality generalizes as such, the points of M^{6} could be mapped to the 6D analog of cd_{4} such that the image point is defined as the intersection of a geodesic line with direction given by the 6D momentum with the 5D lightlike boundary of 6D counterpart cd_{6} of cd? Does the slicing of M^{6} by 5D lightboundaries of cd_{6} for various values of 6D mass squared have interpretation as CP_{3}? Note that the boundary of cd_{6} does not contain origin and the same applies to CP_{3}= C^{4}/C_{×}.
 Or could one identify the octonionic analog of the projective space CP_{3}=C^{4}/C_{×}? Could the octonionic M^{8} momenta be scaled down by dividing with the momentum projection in the commutative normal space so that one obtains an analog of projective space? Could one use these as coordinates for M^{6}?
The scaled 8momenta would correspond to the points of the octonionic analog of CP_{3}. The scaled down 8D mass squared would have a constant value.
A possible problem is that one must divide either from left or right and results are different in the general case. Could one require that the physical states are invariant under the automorphisms generated o→ gog^{1}, where g is an element of the commutative subalgebra in question?
What about the physical interpretation at the level of M^{8}_{c}.
 The first thing to notice is that in the twistor Grassmann approach twistor space provides an elegant description of spin. Partial waves in the fiber S^{2} of twistor space representation of spin as a partial wave. All spin values allow a unified treatment.
The problem is that this requires massless particles. In the TGD framework 4D masslessness is replaced with its 8D variant so that this difficulty is circumvented. This kind of description in terms of partial waves is expected to have a counterpart at the level of the twistor space T(M(^{4})× T(CP_{2}). At level of M^{8} the description is expected to be in terms of discrete points of M^{8}_{c}.
 Consider first the real part of X^{6}_{c}⊂ M^{8}_{c}. At the level of M^{8} the points of X^{4} correspond to points. The same must be true also at the level of X^{6}. Single point in the fiber space S^{2} would be selected. The interpretation could be in terms of the selection of the spin quantization axis.
Spin quantization axis corresponds to 2 diametrically opposite points of S^{2}. Could the choice of the point also fix the spin direction? There would be two spin directions and in the general case of a massive particle they must correspond to the values S_{z}= +/ 1/2 of fermion spin. For massless particles in the 4D sense two helicities are possible and higher spins cannot be excluded. The allowance of only spin 1/2 particles conforms with the idea that all elementary particles are constructed from quarks and antiquarks. Fermionic statistics would mean that for fixed momentum one or both of the diametrically opposite points of S^{2} defining the same and therefore unique spin quantization axis can be populated by quarks having opposite spins.
 For the 6D tangent space of X^{6}_{c} or rather, its real projection, an analogous argument applies. The tangent space would be parametrized by a point of T(CP_{2}) and mapped to this point. The selection of a point in the fiber S^{2} of T(CP_{2}) would correspond to the choice of the quantization axis of electroweak spin and diametrically opposite points would correspond to opposite values of electroweak spin 1/2 and unique quantization axis allows only single point or pair of diametrically opposite points to be populated.
Spin 1/2 property would hold true for both ordinary and electroweak spins and this conforms with the properties of M^{4}× CP_{2} spinors.
 The points of X^{6}_{c}⊂ M^{8}_{c} would represent geometrically the modes of Hspinor fields with fixed momentum. What about the orbital degrees of freedom associated with CP_{2}?
M^{4} momenta represent orbital degrees of M^{4} spinors so that E^{4} parts of E^{8} momenta should represent the CP_{2} momenta. The eigenvalue of CP_{2} Laplacian defining mass squared eigenvalue in H should correspond to the mass squared value in E^{4} and to the square of the radius of sphere S^{3} ⊂ E^{4}.
This would be a concrete realization for the SO(4)=SU(2)_{L}× SU(2)_{R}↔ SU(3) duality between hadronic and quark descriptions of strong interaction physics. Proton as skyrmion would correspond to a map S^{3} with radius identified as proton mass. The skyrmion picture would generalize to the level of quarks and also to the level of bound states of quarks allowed by the number theoretical hierarchy with Galois confinement. This also includes bosons as Galois confined many quark states.
 The bound states with higher spin formed by Galois confinement should have the same quantization axis in order that one can say that the spin in the direction of the quantization axis is welldefined. This freezes the S^{2} degrees of freedom for the quarks of the composite.
7surfaces with real normal space and generalization of the notion of twistor space
It would seem that twistorialization could correspond to the introduction
of 6surfaces of M^{8}, which have commutative normal space. The next step is to ask whether it makes sense to consider 7surfaces with a real norma space allowing wellordering? This would give a hierarchy of surfaces of M^{8} with dimensions 7, 6, and 4. The 7D space would have bundle projection to 6D space having bundle projection to 4D space.
What could be the physical interpretation of 7D surfaces of M^{8} with real normal space in the octonionic sense and of their H images?
 The first guess is that the images in H correspond to 7D surfaces as generalizations of 6D twistor space in the product of similar 7D generalization of twistor spaces of M^{4} and CP_{2}. One would have a bundle projection to the twistor space and to the 4D spacetime.
 SU(3)/U(1)× U(1) is the twistor space of CP_{2}. SU(3)/SU(2)× U(1) is the twistor space of M^{4}? Could 7D SU(3)/U(1) resp. SU(4)/SU(3) correspond to a generalization of the twistor spaces of M^{4} resp. CP_{2}? What could be the interpretation of the fiber added to the twistor spaces of M^{4}, CP_{2} and X^{4}? S^{3} isomorphic to SU(2) and having SO(4) as isometries is the obvious candidate.
 The analog of M^{8}H duality in Minkowskian sector in this case could be to use coordinates for M^{7} obtained by dividing M^{8} coordinates by the real part of the octonion. Is it possible to identify RP_{7}= M^{8}/R_{×} with SU(4)/SU(3) or at least relate these spaces in a natural manner. It should be easy to answer these questions with some knowhow in practical topology.
A possible source of problems or of understanding is the presence of a commuting imaginary unit implying that complexification is involved in Minkowskian degrees of freedom whereas in CP_{2} degrees of freedom it has no effect. RP_{7} is complexified to CP_{7} and the octonionic analog of CP_{3} is replaced with its complexification.
What could be the physical interpretation of the extended twistor space?
 Twistorialization takes care of spin and electroweak spin. The remaining standard model quantum numbers are Kähler magnetic charges for M^{4} and CP_{2} and quark number. Could the additional dimension allow their geometrization as partial waves in the 3D fiber?
The first thing to notice is that it is not possible to speak about the choice of quantization axis for U(1) charge. It is however
possible to generalize the momentum space picture also to the 7D branes X^{7} of M^{8} with real normal space and select only discrete points of cognitive representation carrying quarks. The coordinate of 7D generalized momentum in the 1D fiber would correspond to some charge interpreted as a U(1) momentum in the fiber of 7D generalization of the twistor space.
 One can start from the level of the 7D surface with a real normal space. For both M^{4} and CP_{2}, a plausible guess for the identification of 3D fiber space is as 3sphere S^{3} having Hopf fibration S^{3}→ S^{2} with U(1) as a fiber.
At H side one would have a wave exp(iQ φ/2π) in U(1) with charge Q and at M^{8} side a point of X^{7} representing Q as 7:th component of 7D momentum.
Note that for X^{6} as a counterpart of twistor space the 5:th and 6:th components of the generalized momentum would represent spin quantization axis and sign of quark spin as a point of S^{2}. Even the length of angular momentum might allow this kind representation.
 Since both M^{4} and CP_{2} allow induced Kähler field, a possible identification of Q would be as a Kähler magnetic charge. These charges are not conserved but in ZEO the nonconservation allows a description in terms of different values of the magnetic charge at opposite halfs of the lightcone of M^{8} or CD.
Instanton number representing a change of magnetic charge would not be a charge in strict sense and drops from consideration.
One expects that the action in the 7D situation is analogous to ChernSimons action associated with 8D Kahler action, perhaps identifiable as a complexified 4D Kähler action.
 At M^{4} side, the 7D bundle would be SU(4)/SU(3)→ SU(4)/SU(3)× U(1). At CP_{2} side the bundle would be SU(3)/U(1)→ SU(3)/U(1)× U(1).
 For the induced bundle as 7D surface in the SU(4)/SU(3)× SU(3)/U(1), the two U(1):s are identified. This would correspond to an identification φ(M^{4})= φ(CP_{2}) but also a more general correspondence φ(M^{4})= (n/m)φ(CP_{2}) can be considered. m/n can be seen as a fractional U(1) winding number or as a pair of winding numbers characterizing a closed curve on torus.
 At M^{8} level, one would have Kähler magnetic charges Q_{K}(M^{4}), Q_{K}(CP_{2}) represented associated with U(1) waves at twistor space level and as points of X^{7} at M^{8} level involving quark. The same wave would represent both M^{4} and CP_{2} waves that would correlate the values of Kähler magnetic charges by Q_{K,m}(M^{4})/Q_{K,m}(CP_{2})= m/n if both are nonvanishing. The value of the ratio m/n affects the dynamics of the 4surfaces in M^{8} and via twistor lift the spacetime surfaces in H.
How could the Grassmannians of standard twistor approach emerge number theoretically?
One can identify the TGD counterparts for various Grassmann manifolds appearing in the standard twistor approach.
Consider first, the various Grassmannians involved with the standard twistor approach (this) can be regarded as flagmanifolds of 4complex dimensional space T.
 Projective space is FP_{n1} the Grasmannian F_{1}(F^{n}) formed by the kD planes of V^{n} where F corresponds to the field of real, complex or quaternionic numbers, are the simplest spaces of this kind. The Fdimension is d_{F}=n1. In the complex case, this space can be identified as U(n)/U(n1)× U(1)= CP_{n1}.
 More general flag manifolds carry at each point a flag, which carries a flag which carries ... so that one has a hierarchy of flag dimensions d_{0}=0<d_{1}<d_{2}...d_{k}=n. Defining integers n_{i}= d_{i}d_{i1}, this space can in the complex case be expressed as U(n)/U(n_{1})×.....U(n_{k}). The real dimension of this space is d_{R}=n^{2}∑_{i}n_{i}^{2}.
 For n=4 and F=C, one has the following important Grassmannians.
 The twistor space CP_{3} is projective is of complex planes in T=C^{4} and given by CP_{3}=U(4)/U(3)× U(1) and has real dimension d_{R}=6.
 M=F_{2} as the space of complex 2flags corresponds to U(4)/U(2)× U(2) and has d_{R}=168= 8. This space is identified as a complexified Minkowski space with D_{C}= 4.
 The space F_{1,2} consisting of 2D complex flags carrying 1D complex flags has representation U(4)/U(2)× U(1)× U(1) and has dimension D_{R}=10.
F_{1,2} has natural projection ν to the twistor space CP_{3} resulting from the symmetry breaking U(3)→ U(2)× U(1) when one assigns to 2flag a 1flag defining a preferred direction. F_{1,2} also has a natural projection μ to the complexified and compactified Minkowski space M=F_{2} resulting in the similar manner and is assignable to the symmetry breaking U(2)× U(2)→ U(1)× U(1) caused by the selection of 1flag.
These projections give rise to two correspondences known as Penrose transform. The correspondence μ ∘ ν_{1} assigns to a point of twistor space CP_{3} a point of complexified Minkowski space. The correspondence ν ∘ μ_{1} assigns to the point of complexified Minkowski space a point of twistor space CP_{3}. These maps are obviously not unique without further conditions.
This picture generalizes to TGD and actually generalizes so that also the real Minkowski space is obtained naturally. Also the complexified Minkowski space has a natural interpretation in terms of extensions of rationals forcing complex algebraic integers as momenta. Galois confinement would guarantee that physical states as bound states have real momenta.
 The basic space is Q_{c}=Q^{2} identifiable as a complexified Minkowski space. The idea is that number theoretically preferred flags correspond to fields R,C,Q with real dimensions 1,2,4. One can interpret Q_{c} as Q^{2} and Q as C^{2} corresponding to the decomposition of quaternion to 2 complex numbers. C in turn decomposes to R× R.
 The interpretation C^{2}= C^{4} gives the above described standard spaces. Note that the complexified and compactified Minkowski space is not same as Q_{c}=Q^{2} and it seems that in TGD framework Q_{c} is more natural and the quark momenta in M^{4}_{c} indeed are complex numbers as algebraic integers of the extension.
Number theoretic hierarchy R→ C→ Q brings in some new elements.
 It is natural to define also the quaternionic projective space Q_{c}/Q=Q^{2}/Q (see this), which corresponds to real Minkowski space. By noncommutativity this space has two variants corresponding to left and right division by quaternionic scales factor. A natural condition is that the physical states are invariant under automorphisms q→ hqh^{1} and depend only on the class of the group element. For the rotation group this space is characterized by the direction of the rotation axis and by the rotation angle around it and is therefore 2D.
This space is projective space QP_{1}, quaternionic analog of Riemann sphere CP_{1} and also the quaternionic analog of twistor space CP_{3} as projective space. Therefore the analog of real Minkowski space emerges naturally in this framework. More generally, quaternionic projective spaces Q^{n} have dimension d=4n and are representable as coset spaces of symplectic groups defining the analogs of unitary/orthogonal groups for quaternions as Sp(n+1)/Sp(n)× Sp(1) as one can guess on basis of complex and real cases. M^{4}_{R} would therefore correspond to Sp(2)/Sp(1)× SP(1).
QP_{1} is homeomorphic to 4sphere S^{4} appearing in the construction of instanton solutions in E^{4} effectively compactified to S^{4} by the boundary conditions at infinity. An interesting question is whether the selfdual Kähler forms in E^{4} could give rise to M^{4} Kähler structure and could correspond to this kind of selfdual instantons and therefore what I have called HamiltonJacobi structures.
 The complex flags can also contain real flags. For the counterparts of twistor spaces this means the replacement of U(1) with a trivial group in the decompositions.
The twistor space CP_{3} would be replaced U(4)/U(3) and has real dimension d_{R}=7. It has a natural projection to CP_{3}. The space F_{1,2} is replaced with representation U(4)/U(2) and has dimension D_{R}=12.
To sum up, the Grassmannians associated with M^{4} as 6D twistor space and its 7D extension correspond to a complexification by a commutative imaginary unit i  that is "vertical direction". The Grassmannians associated with CP_{2} correspond to "horizontal ", octonionic directions and to associative, commutative and wellordered normal spaces of the spacetime surface and its 6D and 7D extensions. Geometrization of the basic quantum states/numbers  not only momentum  representing them as points of these spaces is in question.
See the the chapter Summary of TGD as it is towards end of 2021 or the article
with the same title.
