In 1828, George Green (1793-1841) discovered Green's Functions, which describe the basic Harmonic Mathematics of Physics. Green was a self-taught mathematician who worked in his family mill. Green's functions can be used with respect to any Division Algebra. At the time Green discovered them, the only Division Algebras known were the Real and Complex Numbers. Green used his Green's Functions to describe the Potential Theory of Electromagnetism.
In 1831, James Clerk Maxwell (1831-1879) was born.
In 1843, the Quaternion Division Algebra was discovered by William Rowan Hamilton (1805-1865).
In 1844, N-dimensional Exterior and Interior Geometric Products were discovered by Hermann Grassmann (1809-1877).
In 1845, the Octonion Division Algebra was discovered by John Graves and Arthur Cayley (1821-1895). Cayley,who practiced law to make money so that he could pursue mathematics, also invented Matrix Algebra.
Also in 1845, William Kingdon Clifford (1845-1879) was born.
In 1858, according to Collective Electrodynamics by Carver Mead (MIT 2000), "... Bernhard Riemann deduces the phenomena of the induction of electric currents from a modified form of Poisson's equation
where V is the electrostatic potential, and a a velocity. ... The four-vector generalization of Riemann's equation was formualted by Sommerfeld shortly after Einstein's 1905 paper introduced the special theory of relativity. ...".
In 1864, Maxwell discovered the equations of Electromagnetism, which he wrote in the form of Complex Numbers and Vectors in his paper "A dynamical theory of the electromagnetic field".In the abstract to that 1864 paper (dated 27 October 1864, and reprinted in The Scientific Letters and Papers of James Clerk Maxwell, Volume II 1862-1873, edited by P. M. Harman (Cambridge Un. Press 1995) at pages 189-196), Maxwell says:
"The proposed Theory seeks for the origin of electromagnetic effects in the medium surrounding the electric or magnetic bodies ... The properties attributed to the medium in order to explain the propagation of light are -1st. That the motion of one part communicates motion to the parts in its neighborhood.
2nd. That this communication is ot instantaneous but progressive, and depends on the elasticity of the medium as compared with its density.
The kind of motion attributed to the medium when transmitting light is that called transverse vibration. An elastic medium capable of such motions must be also capable of a vast variety of other motions, and its elasticity may be called into play in other ways, some of which may be discoverable by their effects. ...
... if we look for the explanation of the force of gravitation in the action of a surrounding medium, the constitution of the medium must be such that, when far from the presence of gross matter, it has immense intrinsic energy, part of which is removed from it wherever we find the signs of gravitating force. ...
... The equations of this paper ... show that transverse disturbances, and transverse disturbances only, will be propagated through the field, and that the number which expresses the velocity of propagation must be the same as that which expresses the number of electrostatic units units of electricity in one electromagnetic unit, the standards of space and time being the same. ... ...the ... theory ... restores the medium [luminiferous ether] ... and certifies that the vibrations are transverse, and that the velocity is that of light. With regard to normal [longitudinal] vibrations, the electromagnetic theory does not allow of their transmission. ...".
In 1867, Peter Guthrie Tait wrote his book on Quaternions, and Maxwell and Tait discussed Quaternions in their correspondence.
On 7 Nov 1870, Maxwell wrote to Tait a letter discussing Quaternion terminology for things like
saying: "... I want phrases of this kind to make statements in electromagnetism ...".
Also in November 1870, Maxwell wrote a Manuscript on the Application of Quaternions to Electromagnetism, which is reprinted in Volume II of Maxwell's Scientific Papers at pages 570-576. In it Maxwell uses the term curl instead of twirl, and he also says:
"... The invention of the Calculus of Quaternions by Hamilton is a step towards the knowledge of quantities related to space which can only be compared for its importance with the invention of triple coordinates by Descartes. The limited use which has up to the present time been made of Quaternions must be attributed partly to the repugnance of most mature minds to new methods involving the expenditure of thought ...".
At this time, Maxwell had a clear idea that waves should have Scalar and Vector parts, and used the following terms in his Quaternionic formulation of the equations of Electromagnetism:
__ Slope = what we call Grad (represented by Nabla \/ ) Convergence = what we call Div Curl = what we call Curl Concentration = what we call Laplacian
Since Maxwell then had both the concept of waves in an elastic medium and the concepts of Grad, Div, Curl, and Laplacian, he had everything you need to write the equations for Longitudinal Waves in an elastic medium as described, for example (as Jack Sarfatti pointed out) on pages 142-144 of Methods of Theoretical Physics by Morse and Feshbach (McGraw-Hill 1953).Since (as shown in Morse and Feshbach) the Longitudinal Waves are faster than the Transverse Waves, and the Transverse Waves travel at the Speed of Light, the Longitudinal Waves are Superluminal if the Aether is a general elastic medium (Tohu VaVohu).
The question of the existence or non-existence of Longitudinal/Scalar Waves is then the question of whether or not the Aether, regarded as an elastic medium, is compressible:
- If not, there are no Longitudinal/Scalar Waves.
- If so, then there are Superluminal Longitudinal/Scalar Waves.
My personal opinion is that the Aether is compressible, but only at energies around the Vacuum Expectation Value of the Higgs field, around 250 GeV, which is corrresponds to the Superposition Separation of an entire single Tubulin in the Brain.
The Dilation of the 15-dim Conformal Group sets the scale of the Higgs VeV at 250 GeV so that general deformations of SpaceTime can take place only above that energy level, while GraviPhoton Special Conformal (Hopf flow) transformations are useful in Conformal deformations of SpaceTime.Incompressibility of the Aether below 250 GeV is only with respect to the 6-dim vector space of the Conformal Group Spin(2,4), so that below 250 GeV you can see Conformal phenomena that appear to show compressibility from the point of view of 3-dim space or 4-dim Minkowski spacetime. Such conformal phenomena include the Fock superluminal solutions of Maxwell's equations that are described by R. M. Kiehn.
The 4 GraviPhoton Special Conformal transformations of the 15-dim Conformal group are like the Moebius linear fractional transformations, that do deform Minkowski spacetime but take hyperboloids into hyperboloids and are the symmetries of superluminal solutions of the Maxwell equations. They are incompressible/linear from the point of view of a 6-dimensional SpaceTime, with 4 spatial dimensions and 2 time dimensions, because the conformal group over Minkowski spacetime is just SU(2,2) = Spin(2,4), the covering group of SO(2,4), and therefore the Lie algebra generators look like those of rotations in a 6-dim vector space of signature (2,4). This is the 4-dim space with 2-dim time suggested by Robert Neil Boyd, in which things look linear (even though from our conventional 3-dim spatial or 4-dim Minkowski point of view they might appear, due to our limited conventional perspective, to be nonlinear). If you regard Physical SpaceTime as the 6-dimensional vector space of Spin(2,4), and Internal Symmetry Space as 4-dimensional CP2, then the total space is 6+4=10-dimensional. With respect to tthe D4-D5-E6-E7 model, that 10-dim space corresponds:
to the 10-dim vector space of the D5 Lie Algebra Spin(2,8); andto the 10-dim element of the decomposition of the 27-dim representation of the E6 Lie Algebra into 10 + 16 + 1 under its D5 subalgebra (see, for example, Lie Algebras in Particle Physics, 2nd edition, by Howard Georgi, Perseus Books (1999), page 308).
Since the unit Quaternions form the Lie Group Sp(1) = SU(2) = Spin(3) = S3, Maxwell's use of Quaternions in Electromagnetism anticipated the SU(2) Weak Force and the SU(2)xU(1) ElectroWeak unification, and Maxwell's consideration of a compressible general elastic Aether medium anticipated the Higgs mechanism and Torsion Physics.
Also in 1870, Clifford showed that energy and matter are simply different types of curvature of space, thus anticipating Einstein's theory of Gravitation as Curved Spacetime. According to the Encyclopaedia Britannica, Clifford also coined the phrase "... "mind-stuff" (the simple elements of which consciousness is composed) ...".
In terms of the smallest charged Elementary Particle, the First-Generation Fermion Electron Compton Radius Vortex Particle, the Higgs VEV (about 250 GeV = 5 x 10^5 Me (Electron Masses)) gives the linear compressibility of the Aether, Therefore, the Gravitational VEV should be given by the 4-volume compressibility of the Aether, so that the Gravitational VEV is about ( 5 x 10^5 )^4 Me = 6 x 10^22 Me = 3 x 10^22 MeV = 3 x 10^19 GeV. Since the Gravitational VEV should correspond to a pair of Planck Mass Black Holes, the Planck Mass could be derived to be about 1.5 x 10^19 GeV.
In 1871, Maxwell wrote a letter of reference for Clifford, saying:
"... The peculiarities of Mr. Clifford's researches ... is that they tend not to the elaboration of abstruse theorems by ingeneous calculations, but to the elucidation of scientific ideas by the concentration upon them of clear and steady thought. ...".
In 1873, Maxwell published his treatise on Electricity and Magnetism. In the same year, in his Lecture on Faraday's Lines of Force (reprinted in Volume II of Maxwell's Scientific Papers), Maxwell said:
"... If we propose to account for [the attraction of gravitation] in the same way as we have done for magnetism we must admit that there is pressure instead of tension along the lines of force and tension instead of pressure at right angles to them and that here where we sit the ether is supporting a vertical pressure of more than 37000 tons on the square inch. The strength of steel is nothing to this. ...".
Also in 1873, Sophus Lie (1842-1899) (who had studied with Felix Klein (1849-1925)) began his study of transformation groups which over the succeeding years produced Lie Algebras, which were independently introduced and classified by Wilhelm Killing (1847-1923) and Elie Cartan (1869-1951). The classification of Lie Algebras corresponds to the classification of the Alternative Real Division Algebras: Real numbers, Complex numbers, Quaternions, and Octonions.
In 1876, Clifford, who had been describing the topology of Riemann (1826-1866) surfaces, discovered Clifford Algebras., thus anticipating Dirac's rediscovery of Clifford Algebras when he formulated the Dirac Equation of Quantum ElectroDynamics.
Dirac not only rediscovered Clifford algebras, he also:
(in 1938) anticipated the Compton Radius Vortex Model of the electron, as shown in this quote from pages 194-195 of Dirac: A Scientific Biography, by Helge Kragh (Cambridge 1990): "... "... It would appear here that we have a contradiction with elementary ideas of causality. The electron seems to know about he pulse before it arrives and to get up an acceleration (as the equations of motion allow it to do), just sufficient to balance the effect of the pulse when it does arrive." Dirac seemed to accept this pre-acceleration as a matter of fact, necessitated by the equations, and did not discuss it further. However, Dirac explained that the strange behavior of electrons in this theory could be understood if the electron was thought of as an extended particle with a nonlocal interior. He suggested that the point electron, embedded in its own radiation field, be interpreted as a sphere of radius a, where a is the distance within which an incoming pulse must arrive before the electron accelerates appreciably. With this interpretation he showed that it was possible for a signal to be propagated faster than light through the interior of the electron. He wrote: "The finite size of the electron now reappears in a new sense, the interior of the electron being a region of failure, not of the field equations of electromagnetic theory, but of some of the elementary properties of space-time." In spite of the appearance of superluminal velocities, Dirac's theory was Lorentz-invariant. ..." ; and(in 1951-1954) advocated the reality and utility of the aether, as shown in this quote from pages 202-203 of Dirac: A Scientific Biography, by Helge Kragh (Cambridge 1990): "... "Let us imagine the aether to be in a state for which all values of the velocity of any bit of aether, less than the velocity of light, are equally probable. ... In this way the existence of an aether can be brought into complete harmony with the principle of relativity." Dirac identified the ether velocity with the stream velocity of his classical electron theory ... it was the velocity with which small charges would flow if they were introduced. ... in the spring of 1953, Dirac proposed that absolute time be reconsidered. ... The ether, absolute simultaneity, and absolute time "... can be incorporated into a Lorentz invariant theory with the help of quantum mechanics ..." ... he was unable to work out a satisfactory quantum theory with absolute time and had to rest content with the conclusion that "one can try to build up a more elaborate theory with absolute time involving electron spins ...". Recall that Nelson's non-local stochastic quantum mechanics (which I think can be formulated consistently with Bohm theory) involves (see the paper by Smolin in the book Quantum Concepts in Space and Time (Penrose and Isham, eds), at page 156) a diffusion constant that "... is inversely proportional to the inertial mass of the particle, with the constant of proportionality being a universal constant hbar: v = hbar / m ...". Compare this with Dirac's 1951 suggestion that the electromagnetism U(1) gauge-fixing condition should be A A = k^2 where (see page 199 in Kragh's book I am omitting some sub and superscript mus and nus): "... In order to get agreement with the Lorentz equation, the constant k was indentified with m/e The four-velocity v of a stream of electrons ws found to be related to A by v = (1/k) A ..." which gives for Dirac's theory v = e / m.
In 1879, both Maxwell and Clifford died, and Einstein was born.
and
Clifford Algebras could have been combined with Maxwell's Quaternionic Electromagnetism to produce the Dirac Equation;
and
Maxwell's Quaternionic Electromagnetism and Compressible Elastic Aether could have been extended to describe not only U(1) Electromagnetism but also photons with mass and longitudinal polarization, thus anticipating the massive neutral weak boson with gauge group SU(2), the ElectroWeak U(1)xSU(2) = U(2) model, and the Higgs Mechanism, and Torsion Physics.
Further, you could condsider
Maxwell's geometric imagination (he visualized Vortices in the Aether, and made stereoscopes to view images in 3-dimensions and zoetropes to view images in motion), as well as
his mathematical/mystical worldview (he said: "... [the aether] is fitted ... to constitute the material organism of beings excercising functions of life and mind as high or higher than ours ..."; and "... cubic surfaces! By threes and nines Draw round his camp your seven-and-twenty lines The seal of Solomon in three dimensions. ... we the form may trace Of him whose soul, too large for vulgar space, In n dimensions flourished unrestricted. ..."), and
you could consider that Maxwell's 27-dimensional structure is simiilar to the 27-dimensional geometry based on the exceptional Jordan algebra of 3x3 Hermitian Octonion matrices and
that the 27-complex-dimensional symmetric space E7 / (E6xU(1)) describes, at the Nearest Neighbor lowest level of Interconnectedness, the Super Implicate Order, or MacroSpace, whose Geometry produces Jack Sarfatti's nonlinear Back-Reaction Quantum Theory of Matter and Mind.
With that in mind, you might conjecture that:
Since Octonions (the next, and final, Alternative Real Division Algebra beyond the Quaternions) had already been discovered; and
Since 8-dimensional Octonions can be a representation space for the 8-dimensional Lie Group SU(3):
the late 1800s might have seen an Extension from Quaternions to Octonions,
resulting in an extension of Gravity and SU(2)xU(1)
to a Unified Theory of
Gravity plus the SU(3)xSU(2)xU(1) Standard Model
such as the D4-D5-E6-E7 Model.
However, what might have been was not what was:
In 1887, according to Collective Electrodynamics by Carver Mead (MIT 2000), "... W. Voigt published a little-known paper in which he showed that ... Maxwell's equations, in space free of charges and currents, are not altered by a ... Lorentz transformation. ... This transformation was reinvented in 1892 by H. A. Lorentz ...[who]... derived his result independently ...".
Maxwell's Quaternions were thrown away from Electromagnetism by Josiah Willard Gibbs at Yale and Oliver Heaviside in England. As Saul-Paul Sirag quotes from the biography, Sir William Rowan Hamilton, by Thomas L. Hankins, Johns Hopkins Press, 1980, pp. 316 - 319:
"... in 1888, Gibbs explained how reading Maxwell's [1873] Treatise on Electricity and Magnetism led him to devise his system of vector analysis: "My first acquaintance with quaternions was in reading Maxwell's E.&M. where Quaternion notations are considerably used. ... I saw, that although the methods were called quaternionic the idea of the quaternion was quite foreign to the subject. ...I therefore began to work out ab initio, the algebra of the two kinds of multiplication, the three differential operations [del] applied to a scalar, & the two operations to a vector, & those fuctions or rather integrating operators which (under certain limitations) are the inverse of the said differential operators, & which play the leading roles in many departments of Math. Phys. To these subjects was added that of lin. vec. functions which is also prominent in Maxwell's E. & M."
In 1903, according to Collective Electrodynamics by Carver Mead (MIT 2000), "... Sommerfeld introduces the Lorentz-invariant quantity S = J . A which he calls the Schwarzchild invariant .... K . Schwarzchild, Gottinger Nachr. 1903 ... Note the publication 1903! Thus Schwarzchild arrived intuitively at the correct postulate of the theory of invariants six years ahead of Minkowski. ... two years before Einstein's paper on special relativity ... The Schwarzchild invariant ... When integrated over all four coordinates of space-time ... has the units of energy x time; it is called the action of the system. When divided by hbar, this integral is dimensionless. ... From our point of view, the action is flux x charge, rather than energy x time. ...".
Lie Groups remained only a narrow field of Mathematics until around 1920.
Clifford's Curved Space Physics and Clifford Algebras were ignored until Dirac discovered the Dirac Equation in 1932.
Quaternions did not return to fundamental Physics models until 1962, when Finkelstein, Jauch, Schiminovich, and Speiser wrote a paper titled Some Physical Consequences of General Q-Covariance, Helvetica Physica Acta, Volume XXXV (1962) 328-329, in which they showed that the quaternion imaginary degrees of freedom corresponded to the Higgs field that gives mass to the SU(2) gauge bosons. They extended the result of Stueckelberg that a vector gauge boson could, by interacting with a scalar field transforming additively under the gauge group, become massive. Their extension was to use a quaternionic gauge structure that naturally produced a scalar field with nonzero vacuum expectation value that transformed multiplicatively under the gauge group (effectively being the exponential of Stueckelberg's scalar field).
Theirs was the first paper (as far as I know) that used Quaternionic SU(2) symmetry to describe the mechanism whereby two charged SU(2) bosons get mass, and the electromagnetic field is unified with the SU(2) bosons. Their paper effectively did the "Higgs Mechanism" before Higgs, and did ElectroWeak Unification before Glashow,Salam, and Weinberg (who, for their ElectroWeak work, shared the 1979 Nobel Prize).
The eta(x) that they call a "fundamental field" corresponds to the Higgs field. Their paper describes three vector fields: two with mass and charge (the W+ and W-); and one massless and neutral (the photon). They do not in their paper construct the neutral massive Z0.
They gave more details of their model in their paper titled Principle of General Q Covariance, J. Math. Phys. 4 (1963) 788-796, (received 10 December 1962).
Finkelstein, Jauch, Schiminovich, and Speiser did not prove renormalizability, but neither did Glashow, Salam, and Weinberg. Renormalizability was proven by 't Hooft, who did not win a Nobel Prize until 1999, when he shared it with his former adviser Veltman.
Later in the 20th Century, Torsion Physics was studied by R. M. Kiehn.
Since the circle U(1) = S1, and the 1-sphere S1 is the unit Complex Numbers, the Complex Numbers have a natural local U(1) gauge group, which is the gauge group of Electromagnetism. Therefore, the Complex Numbers naturally produce QED.
Since the (6 - 3 = 3)-dimensional symmetric space Spin(4) / SU(2) = S3, and the 3-sphere S3 is the unit Quaternions, the Quaternions have a natural local SU(2) gauge group, which is the Weak Force gauge group. Since the Complex Numbers are a subalgebra of the Quaternions, the Quaternions naturally unify Electromagnetism and the Weak Force, producing the ElectroWeak SU(2)xU(1) sector of the Standard Model.
Further, since the Spin(4) Lie algebra is the Euclidean version of the Lie algebra of the Lorentz Group, the Quaternions naturally unify the ElectroWeak SU(2)xU(1) sector of the Standard Model with Special Relativity in 4-dimensional SpaceTime.
Since the (15 - 8 = 7)-dimensional symmetric space Spin(6) / SU(3) = S7, and the 7-sphere S7 is the unit Octonions, the Octonions have a natural local SU(3) gauge group, which is the Color Force gauge group. Since the Quaternions are a subalgebra of the Octonions, the Octonions naturally unify Electromagnetism, the Weak Force, and the Color Force, producing the SU(3)xSU(2)xU(1) Standard Model.
Further, since the Spin(6) Lie algebra is the Euclidean version of the Lie algebra of the Conformal Group, and since the Conformal Group can produce Gravity by the MacDowell-Mansouri Mechanism,
Just as the Quaternions have the 3-sphere S3 that is SU(2) and can make an SU(2) gauge group, the Octonions have the 7-sphere S7. S7 is not a Lie group, but
S7 is parallelizable and can have Torsion Structure.
If you extend S7 in a natural way
...
...