- As Witten shows, the twistor transform is problematic in signature (1,3) for Minkowski space since the the bi-spinor μ playing the role of momentum is complex. Instead of defining the twistor transform as ordinary Fourier integral, one must define it as a residue integral. In signature (2,2) for space-time the problem disappears since the spinors μ can be taken to be real.

- The twistor Grassmannian approach works also nicely for (2,2) signature, and one ends up with the notion of positive Grassmannians, which are real Grassmannian manifolds. Could it be that something is wrong with the ordinary view about twistorialization rather than only my understanding of it?

- For M
^{4}the twistor space should be non-compact SU(2,2)/SU(2,1)× U(1) rather than CP_{3}= SU(4)/SU(3)× U(1), which is taken to be. I do not know whether this is only about short-hand notation or a signal about a deeper problem.

- Twistorilizations does not force SUSY but strongly suggests it. The super-space formalism allows to treat all helicities at the same time and this is very elegant. This however forces Majorana spinors in M
^{4}and breaks fermion number conservation in D=4. LHC does not support*N*=1 SUSY. Could the interpretation of SUSY be somehow wrong? TGD seems to allow broken SUSY but with separate conservation of baryon and lepton numbers.

^{8}.

- One can always find a decomposition M
^{8}=M^{2}_{0}× E^{6}so that the complex light-like quaternionic 8-momentum restricts to M^{2}_{0}. The preferred octonionic imaginary unit represent the direction of imaginary part of quaternionic 8-momentum. The action of G_{2}to this momentum is trivial. Number theoretic color disappears with this choice. For instance, this could take place for hadron but not for partons which have transversal momenta.

- One can consider also the situation in which one has localized the 8-momenta only to M
^{4}=M^{2}_{0}× E^{2}. The distribution for the choices of E^{2}⊂ M^{2}_{0}× E^{2}=M^{4}is a wave function in CP_{2}. Octonionic SU(3) partial waves in the space CP_{2}for the choices for M^{2}_{0}× E^{2}would correspond ot color partial waves in H. The same interpretation is also behind M^{8}-H correspondence.

- The transversal quaternionic light-like momenta in E
^{2}⊂ M^{2}_{0}× E^{2}give rise to a wave function in transversal momenta. Intriguingly, the partons in the quark model of hadrons have only precisely defined longitudinal momenta and only the size scale of transversal momenta can be specified.

The introduction of twistor sphere of T(CP

_{2}) allows to describe electroweak charges and brings in CP_{2}helicity identifiable as em charge giving to the mass squared a contribution proportional to Q_{em}^{2}so that one could understand electromagnetic mass splitting geometrically.

The physically motivated assumption is that string world sheets at which the data determining the modes of induced spinor fields carry vanishing W fields and also vanishing generalized Kähler form J(M

^{4}) +J(CP_{2}). Em charge is the only remaining electroweak degree of freedom. The identification as the helicity assignable to T(CP_{2}) twistor sphere is natural.

- In general case the M
^{2}component of momentum would be massive and mass would be equal to the mass assignable to the E^{6}degrees of freedom. One can however always find M^{2}_{0}× E^{6}decomposition in which M^{2}momentum is light-like. The naive expectation is that the twistorialization in terms of M^{2}works only if M^{2}momentum is light-like, possibly in complex sense. This however allows only forward scattering: this is true for complex M^{2}momenta and even in M^{4}case.

The twistorial 4-fermion scattering amplitude is however

*holomorphic*in the helicity spinors λ_{i}and has no dependence on λtilde;_{i}. Therefore carries no information about M^{2}mass! Could M^{2}momenta be allowed to be massive? If so, twistorialization might make sense for massive fermions!

^{2}

_{0}momentum deserves a separate discussion.

- A sharp localization of 8-momentum to M
^{2}_{0}means vanishing E^{2}momentum so that the action of U(2) would becomes trivial: electroweak degree of freedom would simply disappear, which is not the same thing as having vanishing em charge (wave function in T(CP_{2}) twistorial sphere S^{2}would be constant). Neither M^{2}_{0}localization nor localization to single M^{4}(localization in CP_{2}) looks plausible physically - consider only the size scale of CP_{2}. For the generic CP_{2}spinors this is impossible but covariantly constant right-handed neutrino spinor mode has no electro-weak quantum numbers: this would most naturally mean constant wave function in CP_{2}twistorial sphere.

For the preferred extremals of twistor lift of TGD either M

^{4}or CP_{2}twistor sphere can effectively collapse to a point. This would mean disappearence of the degrees of freedom associated with M^{4}helicity or electroweak quantum numbers.

- The localization to M
^{4}⊃ M^{2}_{0}is possible for the tangent space of quaternionic space-time surface in M^{8}. This could correlate with the fact that neither leptonic nor quark-like induced spinors carry color as a spin like quantum number. Color would emerge only at the level of H and M^{8}as color partial waves in WCW and would require de-localization in the CP_{2}cm coordinate for partonic 2-surface. Note that also the integrable local decompositions M^{4}= M^{2}(x)× E^{2}(x) suggested by the general solution ansätze for field equations are possible.

- Could it be possible to perform a measurement localization the state precisely in fixed M
^{2}_{0}always so that the complex momentum is light-like but color degrees of freedom disappear? This does not mean that the state corresponds to color singlet wave function! Can one say that the measurement eliminating color degrees of freedom corresponds to color confinement. Note that the subsystems of the system need not be color singlets since their momenta need not be complex massless momenta in M^{2}_{0}. Classically this makes sense in many-sheeted space-time. Colored states would be always partons in color singlet state.

- At the level of H also leptons carry color partial waves neutralized by Kac-Moody generators, and I have proposed that the pion like bound states of color octet excitations of leptons explain so called lepto-hadrons. Only right-handed covariantly constant neutrino is an exception as the only color singlet fermionic state carrying vanishing 4-momentum and living in all possible M
^{2}_{0}:s, and might have a special role as a generator of supersymmetry acting on states in all quaternionic subs-spaces M^{4}.

- Actually, already p-adic mass calculations performed for more than two decades ago forced to seriously consider the possibility that particle momenta correspond to their projections o M
^{2}_{0}⊂ M^{4}. This choice does not break Poincare invariance if one introduces moduli space for the choices of M^{2}_{0}⊂ M^{4}and the selection of M^{2}_{0}could define quantization axis of energy and spin. If the tips of CD are fixed, they define a preferred time direction assignable to preferred octonionic real unit and the moduli space is just S^{2}. The analog of twistor space at space-time level could be understood as T(M^{4})=M^{4}× S^{2}and this one must assume since otherwise the induction of metric does not make sense.

^{8}if one accepts that only M

^{2}

_{0}momentum is sharply defined?

- What happens to the conformal group SO(4,2) and its covering SU(2,2) when M
^{4}is replaced with M^{2}_{0}⊂ M^{8}? Translations and special conformational transformation span both 2 dimensions, boosts and scalings define 1-D groups SO(1,1) and R respectively. Clearly, the group is 6-D group SO(2,2) as one might have guessed. Is this the conformal group acting at the level of M^{8}so that conformal symmetry would be broken? One can of course ask whether the 2-D conformal symmetry extends to conformal symmetries characterized by hyper-complex Virasoro algebra.

- Sigma matrices are by 2-dimensionality real (σ
_{0}and σ_{3}- essentially representations of real and imaginary octonionic units) so that spinors can be chosen to be real. Reality is also crucial in signature (2,2), where standard twistor approach works nicely and leads to 3-D real twistor space.

Now the twistor space is replaced with the real variant of SU(2,2)/SU(2,1)× U(1) equal to SO(2,2)/SO(2,1), which is 3-D projective space RP

^{3}- the real variant of twistor space CP_{3}, which leads to the notion of positive Grassmannian: whether the complex Grassmannian really allows the analog of positivity is not clear to me. For complex momenta predicted by TGD one can consider the complexification of this space to CP_{3}rather than SU(2,2)/SU(2,1)× U(1). For some reason the possible problems associated with the signature of SU(2,2)/SU(2,1)× U(1) are not discussed in literature and people talk always about CP_{3}. Is there a real problem or is this indeed something totally trivial?

- SUSY is strongly suggested by the twistorial approach. The problem is that this requires Majorana spinors leading to a loss of fermion number conservation. If one has D=2 only effectively, the situation changes. Since spinors in M
^{2}can be chosen to be real, one can have SUSY in this sense without loss of fermion number conservation! As proposed earlier, covariantly constant right-handed neutrino modes could generate the SUSY but it could be also possible to have SUSY generated by all fermionic helicity states. This SUSY would be however broken.

- The selection of M
^{2}_{0}could correspond at space-time level to a localization of spinor modes to string world sheets. Could the condition that the modes of induced spinors at string world sheets are expressible using real spinor basis imply the localization? Whether this localization takes place at fundamental level or only for effective action being due to SH, is a question to be settled. The latter options looks more plausible.

For details see the new chapter Some Questions Related to the Twistor Lift of TGD of "Towards M-matrix" of "Towards M-matrix" or the article Some questions related to the twistor lift of TGD.

For a summary of earlier postings see Latest progress in TGD.

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