Something Lawfully OccursEpilogue
Forcing, Not Sacred Geometry
When does a beautiful structure count as physics?
This volume ends in the exceptional corner of mathematics: the octonions, the Fano plane, the Klein quartic with its 168 symmetries, twenty-eight lines in seven dimensions. A reader may reasonably be uneasy. Programs that reached this corner before have mostly been remembered for how they failed, and the corner is so richly interconnected that a determined author can find almost any number in it.
The epilogue says why standing there is nonetheless the expected place for a theory of physics to stand, and what distinguishes arriving there from decorating a theory with it.
Standing in the exceptional corner is a signal only when a principle put the theory there. A result counts when it is forced, meaning that a principle stated in advance, applied to every observer at once, admits it and nothing else, or when it is predictive in the sense of Chapter XXIV: computed without fitting, free of unselected weights, read in nature before the comparison, and refutable by it. A result that merely matches, a count of twenty-eight here equal to a count of twenty-eight there, is a question and not an answer.
Status
The volume’s ledger, in five parts, sets two columns side by side: on the left what is exact under the premise its chapter names, on the right what is named but not yet derived. Several entries on the left meet the rule of forcing: the four reports follow from the founding sentence and a minimal observer, the dimensions three and seven from collective completeness, the curvature of comparison from the simplicity of the observers’ relativity group, and the Fano plane from the requirement that a letter be a pair of reports. The others are exact computations on constructions whose added ingredients their chapters name, and one entry, the gauge-link clause, is itself an addition. None was kept merely because it matched a known result.
Most of these results are kinematic: on the stage they fix, the observers, their relativity and the interior they carry, symmetry has been forced and dynamics has not. The lift has fixed a record’s weight, a phase, and the first couplings in form, but no strength. No number yet has the property the magnet’s number had, a value the law fixes without a chosen weight that a measurement could contradict.
The corner is physics’ own
The exceptional structures carry physics’ symmetries. The proper orthochronous Lorentz group is , acting on the sky as Möbius maps, and half-integer spin exists because its double cover does. Colour is , the stabilizer of one imaginary unit in the automorphism group of the octonions, as Günaydin and Gürsey used in 1973. Triality permutes the vector and the two spinor representations of ; is the hidden symmetry of maximal supergravity; and the exceptional Jordan algebra has lately been proposed as the finite quantum geometry of the internal space of particle physics.
The program arrived there from the observer’s side. A candidate principle, that blind observers must jointly see everything, be treated democratically and have directions that compose, narrows the interior to imaginary dimension three or seven once a single observer is set aside, and an observer’s six letters and one time choose seven. The twenty-eight anchored observers are the seven-dimensional solution, their time directions a maximal set of equiangular lines in permuted by the Weyl group of , and they correspond equivariantly to the bitangents of the Klein quartic; colour is what one observer’s time direction cannot see; and the relativity is on , the reduction of the integral Lorentz group of the report counts, with a chiral hyperbolic lift whose cells are the observers and the clocks, and a spin double cover generated natively on the fiber’s Clifford module. That the octonions are thereby an output rather than an input is a reading of the theorem, not a further theorem.
What went wrong before
The history of the corner is a history of matching. Kepler’s Mysterium Cosmographicum of 1596 nested the five Platonic solids between the spheres of the six known planets; it was beautiful and fitted the known distances roughly, but nothing forced it, Kepler’s own later laws put the planets on ellipses, and in 1781 Herschel found a seventh planet. Lisi’s proposal of 2007 placed gravity and the Standard Model inside one connection valued in , and Distler and Garibaldi proved that no such embedding yields the chiral spectrum of the Standard Model’s fermions. The octonionic line, from Günaydin and Gürsey through Dixon to Furey, has been more careful and more lasting, and it has been hardest pressed where representations end: why the weak force acts on one hand only, what dynamics the algebra implies, and whether the algebra requires three families or only makes room for them.
The counterexample is a magnet. The golden ratio that Coldea and collaborators measured in in 2010 was not matched to anything: Zamolodchikov had derived the spectrum from a principle, the integrability of the critical Ising field theory in a magnetic field, and the principle fixed the ratio before anyone looked. The same exceptional structure that failed as a matched unification succeeded as a forced consequence.
The rule, applied
The Wolfram programme is this program’s nearest neighbour, and the difference between them is the one the rule is about. There every rule is admitted, the ruliad contains them all, and physics is what a computationally bounded observer perceives of it; nothing is selected. Here the founding sentence selects four reports, the kernel graph, the prime seven and one arithmetic lift. The two agree that the laws come from what observers are; they differ on whether the laws are forced. Forcing has a recognizable form here: the results that survived are statements about every observer at once, like the curvature theorem, whose proof uses only that the relativity group is simple, while constructions in a single chart came back needing an addition.
The program has applied the rule to itself, not always in time. A dictionary in which observers were the places of a number field and the step of time a Frobenius element was retired when its Frobenius test failed. The coincidence with the twenty-eight bitangents was kept because it was made equivariant, a statement about structure rather than about a number. The ladder of matter classes was compared with nature and refuted; the lift’s three-dimensional interior representations are not read as generations, since three is there the dimension of a representation, not a number of copies; a near coincidence of two computed constants, 0.0213470 and 0.0213870, was recorded and refused; and , which appears both as a ratio of critical rates and as the modulus of certain theta constants, is recorded without a claim, because no map joins the two.
What each description forgets
One idea recurs through the volume, and it is how the parts connect. A description is a map that forgets something, and its kernel is what it forgets, the differences it cannot register. In each part of the volume a structure that physics needs sits in such a kernel. The permanent record forgets which of the histories it cannot tell apart occurred; interference lives there, and one amplitude for each such class is the quantum form of an observer’s reasoning (Chapters II and III). The tally forgets the order of a history, and the loops it forgets carry the curvature of velocity space (Chapter IX). A clock forgets the directions its time cannot see, and the symmetries of the octonions that fix it are colour (Chapter XIV).
The observers’ relativity group forgets the sign of its double cover, and spin is carried by that sign, natively on the fiber (Chapter XV). The finite sky forgets the part of the lift’s group that reduces to the identity on it; that part alone already keeps the light cone, and the common speed is fixed there (Chapter XXII). One step further out, the spacetime parent’s tree forgets a space of vectors and the interior’s a space of spinors, the first the symmetric square of the second (Chapter XVIII). The sky’s two parents show the same pattern from the other side (Chapter XVIII): they agree on the sky, and what tells them apart, the real place at which one is spacetime and the other carries the interior, is exactly what the sky forgets.
The structures physics needs sit in the kernels of descriptions: interference in what the record forgets, curvature in what the tally forgets, colour in what a clock cannot see, spin in the sign the relativity group forgets, the light cone in what the finite sky forgets, and, one step further out, vectors and spinors in what the two parents’ trees forget. This is a reading, not a theorem. It organizes what has been found, and it says where to look for the next structure: in what the next description forgets.
What the volume has established
Exact, under the premise its chapter names. For the observer, the graph and the sky: four reports and a Lorentzian range of report forms whose null member fixes in the alphabet’s units; the tally cover of , a three-dimensional crystal read as space, whose periods generate rotations and whose metric read modulo 2, 3 and 7 gives the seven clocks, one clock’s four reports and the sky, with positions and periods one lattice; the finite sky and its group as a reduction of the integral Lorentz group of the report counts, which cannot reverse the spacelike separations that the prime above three marks, with Thurston’s chiral manifold as its lift, whose transport is the rulial connection; the world’s records as boosts between rest frames, and a bound composite under the adopted contact read; one law in seven charts and the curvature of every covariant comparison; and an adopted, reversible addition, the gauge-link clause, with the Standard Model’s group. For the interior’s algebra, spin and fiber: dimension three or seven from collective completeness, and the clocks as the octavian orders; spin from the double cover on the fiber’s Clifford module, its forced transport, spin on its own factor, the report qubit, with an honest spin bundle over all observers, and records as Wigner’s particle states and reports as massless ones, with the hand as helicity; the fiber as the Pati–Salam quartet with the lepton as the zero displacement, a meeting that keeps the product and is flat within a scale and between scales, an observer’s own law keeping one charge, fermion number reversed at every record, and, since every native process keeps the number of registers, mass for one-handed matter as a pair term that conserves baryon and lepton number. For the interior’s point: the weak doublet’s left half from one point of the Cayley plane, which over the complex numbers carries the whole family, with the breaking carried by a pair of right-handed neutrinos and three generations added as a bare multiplicity.
For the two parents and the tower of scales: the plane of order two forced, with Mumford’s form, the fiber on every site of his building and the two lives of the group of order 168 at one vertex; the parents sharing the sky and nothing beyond it and meeting at Klein’s lattice, vectors on the spacetime side and spinors on the interior’s one step out; matter’s labels following the spacetime completion given that the product is physical, the interior attached to spacetime at one scale, and matter carried around every loop of the tower observer by observer, changed only by colour; colour coupling the scales through shared observers without running along the tower or on the crystal inside each meeting; one native hand, spacetime’s, carried by matter’s spinor, the lift’s own, with the exchange of matter’s quartets an exact symmetry; and the product held fixed across scales. For the limits and the numbers: a controlled temporal limit; shared light directions and an isotropic cone for each sector from the finite symmetries, the light cone kept alone by the part of the lift’s group that the sky cannot see, and a colour-neutral contact adopted as a clause and reaching across the lift; one recorder equilibrium for all observers, given a rate; light, a hand and gravity’s couplings, in form, in the lift; the class constant as a quartic algebraic number, which is also the matter gap when matter’s labels are carried by product-keeping transports in the flat colour background; and the lift’s first field beyond the sky, on all the evidence an elliptic curve. Some of these were found before they were recognized: the eight points of the finite sky were first met as the eight symmetries of order seven that carry one clock through all seven, the tours of the clocks, and the projective line they form was read as a celestial sphere more than three weeks later.
What the volume still owes
The right column is the program’s debt, and it is specific: a measure for an observer’s descriptive moves; space from the kernel rather than from a retention clause; the dynamics in the lift and the law by which registers combine, which would give gravity a strength; a clock-changing dynamics and permission to meet across clocks; a native realization of the gauge links; the placement of the octonion product; a law of motion for the spinor, the degree of the lift that carries matter and the form of the spin bundle; how the spin module and matter’s labelled fiber are related; how the coupling of registers conserves baryon and lepton number, which one register’s law does not; a world of registers, with a vacuum, and a field on matter’s particle states; the sign of exchanging two registers, assumed Fermi, which a pair term the same for every observer would fix at the cost of the split between lepton and quark masses; the force that makes the right-handed-neutrino pair condense, with the generations’ masses and mixings left as data; the weak force’s hand, which needs a vacuum breaking the quartet symmetry, added, and one naming, which quartet the vacuum keeps as weak; a colour frame at every position of the arena, whose loops do subdivide, on which colour would run with the sign of asymptotic freedom, and weights giving that field the speed of light; the homogeneous world; one speed at the cutoff, as a law on the lifted orbits that keeps one cone; the infinite-site vacuum; every coupling’s strength; and memory’s transport from the lift and a physical unit of time. The observer language cannot express a rate at all, so a measure clause must be added and declared, and the program has adopted one, premise P4, one weight per occurrence.
The lift’s arithmetic is where a number of the magnet’s kind could come from. The numbers it fixes so far, such as light’s equal share among the light directions, are built from the prime seven alone and carry nothing beyond the sky. The first that carry more are attached prime by prime to the lift’s first interior modes, which appear only with structure at the prime two; for the first of these modes they agree at every prime computed with the point counts of one elliptic curve over the field of the Eisenstein integers, whose classifying number is times the sky’s prime. Seven primes are strong evidence, not a proof, and what these numbers mean physically is not yet known.
The volume’s through-line gives the order of work. The kernel graph’s covers have supplied branching, space and the loops that space forgets, which carry velocity space’s curvature. The celestial sphere over has supplied a relativity group with its spin cover, and the continuum Lorentz group has been reached from it by a lift, not by inclusion; the same sky is the shadow of a second arithmetic group, compact where the lift’s is Lorentzian, on whose building the interior lives, and the two share the sky and nothing beyond it. In the lift light and a hand exist as kinematics, their first couplings exist in form, and what they and every other sector still need is dynamics.
The unselected rates are, on the program’s own reading, coordinates on the space of rules, and physics is what does not move when they move. “The first number that passes that test and can be compared with an experiment will be the first number of the program that nature could refute. It has not been found. The octonions, the Klein quartic and the finite sphere are where the program’s observers stand, and principles about observers narrowed the way there; what remains is to learn what happens there.”
Seams makes the same distinction a rule of its own: a bridge between two theories is built, type or name, and type recurrence is not identification.
- In the Esquisse
- 15La tour assembléeÉp.L’horizon : dessins d’enfants