- The Bohr orbits out to be 4-D minimal surfaces irrespective of the action principle as long as it is general coordinate invariant and constructible in terms of the induced geometry. 2-D minimal surfaces are non-deterministic in the sense that same frames span several minimal surfaces. One can expect that also in the 4-D case, non-determinism is unavoidable in the sense that the Bohr orbit-like 4-surfaces are spanned by 3-D "frames" as loci of non-determinism.
- At these 3-surfaces minimal surface property fails, the derivatives of the embedding space coordinates are discontinuous and the second fundamental form diverges. Also the generalized holomorphy fails. The failure of smooth structure caused by the edge in 4-D case can give rise to an exotic smooth structure.
- One can also say the singularities act as sources for the analog of massless field equations defined by the vanishing of the trace of the second fundamental form and this justifies the identification of the singularities as vertices in the construction of the scattering amplitudes.
- In the TGD inspired theory of consciousness, classical non-determinism gives rise to geometric correlates of cognition and intentionality and the loci of non-determinism serve as memory seats. Free will is not in conflict with classical determinism and the basic problem of quantum measurement theory finds a solution in zero energy ontology.
- The proposal is that the classical non-determinism corresponds to the non-determinism of p-adic differential equations. In fact, TGD leads to a generalization of p-adic number fields to their functional counterparts and they can be mapped to p-adic number fields by category-theoretical morphism. This generalization allows us to understand the p-adic length scale hypothesis which is central in TGD.
1. The classical non-determinism of 2-D minimal surfaces
The 2-D minimal surface spanned by a given frame (a closed, non-intersecting, simple wire loop or collection of them in 3D space) is generally non-unique. While the existence of at least one minimal surface (a surface of zero mean curvature with vanishing trace of the second fundamental form) is guaranteed, a single frame can bound multiple, and sometimes even a continuum of, distinct minimal surfaces. Here is a breakdown of the uniqueness of minimal surfaces.
- Many frames, particularly non-convex ones, can span several distinct minimal surfaces. A classic example is two coaxially aligned circles, which can bound two different catenoid surfaces (a wider and a narrower one) or two separate disks.
- In certain cases, a given curve can bound a continuous family of minimal surfaces, a phenomenon often observed in physical soap film experiments.
- Uniqueness is achieved only under specific conditions.
- Convex projection: If a closed Jordan curve Γ has a one-to-one orthogonal projection onto a convex planar curve, then Γ bounds a unique minimal disk, which is a graph over that plane.
- Small total curvature: A smooth Jordan curve with a total curvature less than or equal to 4π bounds a unique minimal disk.
- Sufficiently close to a plane: A C2-Jordan curve that is sufficiently close to a plane curve in the C2-topology bounds a unique minimal disk.
- Stability vs. sbsolute uniqueness: A minimal surface is "stable" if small perturbations increase its area. Often, a frame may bound multiple minimal surfaces, but only one is the absolute, global minimum, while others are unstable or local minima.Plateau's Problem: The classical problem asks for the surface of minimum area, which exists, but is not always unique.
2. What could one conclude about the space-time surfaces as minimal surfaces?
The above Google summary helps to make guesses about the naive generalization of these findings in the 4-D situation.
2.1 How unique is the minimal surface spanning a given frame?
One can go to Google and pose the question "How unique is the minimal surface spanning a given frame?". One obtains a nice summary and can ask additional questions. The following considerations are inspired by this question.
- In the case of ordinary minimal surfaces, it is enough that there exists a plane for which the minimal surface is representable as a graph of a map and the projection of the frame to the plane is convex, i.e. any of its points can be connected by a line inside the curve defined by the projection.
An essential assumption is that the 2-D surface is representable locally as a graph over a plane. Curves whose plane projection has an interior, which is non-convex (not all interior points can be connected by a curve in the interior) can also lead to a failure of determinism. Cusp catastrophe, defined in terms of roots of a polynomial of degree 3, is a 2-D example of non-convexity. Note that the cusp is 3-sheeted.
- Consider the general meaning of convexity for objects of dimension d in linear spaces with dimension d+1. One considers a projection of the object with dimension d (say frame to a higher-dimensional space. For minimal surfaces, the object is the frame of dimension d=1 and the space has dimension d=3. For Riemannian manifolds straight lines can be identified as geodesic lines. Planes could be generalized to geodesic manifolds.
- The projection of the 3-D frame, defining the holographic data or a locus of non-determinism defining secondary holographic data, to some 4-D submanifold analogous to the plane should be convex. The surface should be also representable as a graph of a map from the 4-D manifold to H. One could consider projections of the frame X3 to all geodesic submanifolds G4 of dimension D=4. G4∈{M4, E3× S1, E2× S2}, where S1 and S2 are geodesic manifolds of CP2 appear as candidates.
For physically most interesting cases CP2 projection has at least dimension 2 so that E2× S2 is of special interest. Could one choose G4 to be holomorphic sub-manifolds? If hypercomplex holomorphy does not matter, this would leave only 2-D M4 projection. Is it enough to consider G4= E2× S2? Situation would resemble that for ordinary minimal surfaces. Could one consider the convexity of the E2 and S2 projections?
- Convexity: the points of X3 can be connected by geodesic lines. Should they be space-like or could also light-like partonic orbits serve as loci of non-determinism. What about 3-surfaces inside CP2 representing a wormhole contact at which two parallel Minkowskian space-time sheets meet?
- The convexity criterion should be satisfied for all frames defined by 3-D singularities assumed to be given.
- If the 3-D frame corresponding to the roots of f1=0,f2=0 is manysheeted over G4, the projection contains several overlapping regions corresponding to the roots. One does not have a single convex region. This is one source of non-determinism.
- Note: If the projection to M4 is bounded by genus g>0 surface, the M4 projection is not convex. Now however CP2 comes to rescue. Consider as an example a cosmic string X1× S2, where X1 is convex and space-like. If the CP2 projection is g>0 surface, the situation is the same. Could this relate to the instability of higher genera. Would it be induced by classical non-determinism?
2.2 What could be the role of generalized holomorphy?
The failure of holomorphy implies singularities identified as loci of auxiliar holomorphic data and seats of non-determinism.
- Often the absolute minimum is unique. The degeneracy of the absolute minimum would mean additional symmetry. This kind of additional symmetry in the case of Bohr orbits of electrons in an atom corresponds to rotational symmetry implying that the orbit can be in any plane going through the origin.
- How does this relate to f=(f1,f2)=0 conditions has as roots the space-time surface as a generalized complex submanifold of H? Each solution corresponds to a collection of the roots for these conditions and each root corresponds to a space-time region. Two or more roots are identical at the 3-D interfaces of the roots. Each root defines a region of some geodesic submanifold of H defining local generalized complex coordinates of X4 as a subset of corresponding H coordinates in this region. Separate solutions would be independent collections of the roots. Two roots co-incide at at the 3-D interfaces between roots. Cusp catastrophe gives a good 2-D illustration.
- 3-D singularities as analogs of frames correspond to the frames of 4-D "soap films". Since derivatives are discontinuous, the singularities correspond to edges of the space-time and would define defects of the standard smooth structure. This would give rise to an exotic smooth structures.
- The non-determinism should correspond to the branching of the space-time surfaces at the singularities X3 giving rise to alternative Bohr orbits. There is analogy with bifurcations, in particular with shock waves and bifurcations could correspond to the underlying 2-adicity and relate to the p-adic length scale hypothesis.
There would be several kinds of edges of X4 associated with the same X3. The non-representability of the singularity X3 as a graph P(X3)→ X3, where P(X3) is the projection of the singularity to G4 should be essential. Also the non-convexity of the region bounded by P(X3) in G4 matters.
- The volumes of the minimal surfaces spanning a given frame need not be the same and the absolute minimum for the volume, or more generally classical action, could be in the special role. The original proposal indeed was that absolute minima are physically special.
If dynamical symmetries are involved, the extrema can be degenerate. The minimal surfaces are analogs of Bohr orbits and in atomic physics Bohr orbits have degeneracy due to the fact they can be in arbitrary plane: this corresponds to the choice of the quantization axis of angular momentum.
Could the symmetries for the 3-D "frames" induce this kind of degeneracy? Could Galois groups act as symmetries? This would give connection between the view of cognition as an outcome of classical non-determinism and the number theoretic view of cognition relying on Galois groups.
For a summary of earlier postings see Latest progress in TGD.
For the lists of articles (most of them published in journals founded by Huping Hu) and books about TGD see this.