This week I have used Preon Model #7 to make a model for gravitation based on the exchange of graviton bosons. See http://vixra.org/abs/1510.0338 for Models for Quantum Gravity, Dark Matter and Dark Energy Using the Hexark and Preon Model #7 and http://vixra.org/abs/1505.0076 for Hexark and Preon Model #6: etc. A full report on Preon Model #7 is in draft.
First, how does the graviton fit into a table of elementary particles? It does not easily fit into such a table without modifying the table structure. The first change is that the photon, Z and gluon are three members of the same family. Note that they all have zero electric charge, spin +1 or – 1 and zero weak isospin. In my model that makes them one family. The photon deals mainly with uncoloured particles. The Z is designed to interact, albeit neutrally, with coloured quarks, while the gluon can alter quark colour in interactions. That means that the photon is first generation, the Z is second generation and more complex in structure while the gluon is third generation and even more complex in colour, containing enough preons to exhibit colour and anticolour properties simultaneously.
The table of elementary particles in my model has a very simple structure of row by column, where the columns are for the generations and the rows are different families. The graviton is a single family of bosons with zero electric charge, spin + or – 2 and weak isospin + or – 0.5. There are at least three generations of graviton the third generation is as complex as the gluon and has colour-anticolour properties. Just as the electron has two forms: left handed and right handed, so the graviton has two forms, one where the spin and weak isospin have the same sign or handedness as each other and another form where the signs are different.
The higgs family also has at least three generations and the third generation higgs is complex enough to have colour-anticolour. The higgs has no electric charge, no spin and weak isospin of +0.5 or -0.5.
The dark boson family has at least a third generation member with zero properties except colour-anticolour, and that colour-anticolour property is just like that for the gluon, graviton, higgs and dark boson. It also may be possible that the top and bottom quarks share this colour-anticolour property. They could have colour plus colour-anticolour. A fourth generation gluon could have colour-anticolour plus colour-anticolour.
So why is gravity always attractive? In my model, it is not always attractive! It is no more so than are the photon, Z and gluon taken in combination, and the types of gravitons combined are as numerous as types of QED photons, weak and strong QCD gauge bosons. So why does gravity appear to be always attractive? The answer lies in its weakness. In my model, an electron repels an electron using the first generation graviton, just as an electron repels an electron via QED. But that repulsion is too weak to be presently detectable. The third generation colour-anticolor graviton is the most important as it attracts quarks (and gluons and higgs and dark) together gravitationally. But why do we never see quarks repelling quarks gravitationally? There is a parallel question: why do quarks attract quarks, as a net effect, within the atomic nucleus? The answer to that answers the question about gravitational attraction. the strong force is very approximately 10 to the power 40 greater than gravity. That means that where the sphere of influence of the strong force is on the order of the diameter of the nucleus, the sphere of net attractive gravitational influence of the third generation graviton is of the order 10 to the power 40 times as big as the nucleus. That is a sphere of attractive-only influence on a universal scale, or at least intergalactic scale. But far enough away, the first generation gravitational influence between quarks, which is repulsive, can assume dominance. And that repulsion at a remote distance is seen as dark energy.
The dark boson of the third generation can interact gravitationally only with the third generation gravitons. The first and second generation dark bosons (if they exist … as they have no properties we know of) cannot interact repulsively through the first generation graviton and so cannot take part in dark energy. In my guestimation, the higgs is also a candidate for dark matter and it could take part in both attractive gravitation via the third generation graviton and also in dark energy.
I am possibly more pleased at finding a neat structure for the table of elementary particles than at finding the graviton structure. I have always been disconcerted by three things about the Standard Model table: (1) the higgs stuck out on its own, (2) the non-recognition that the photon, Z and gluon are three generations of one family and (3) the W lumped with the Z because tof their weak force connection. The W in my table is a second generation boson in a separate family row.
A further modification in my model is for the way interactions are represented. I have made it a rule in interactions that weak isospin is conserved. This means that an electron cannot simply radiate a photon because it is accelerating. This is basically as issue of field interaction effects versus particle interaction effects. In my model, there is an incoming catalyst boson (the 1/4 higgs+ ) which interacts with the left-handed electron and, as a result, the electron changes handedness and emits a photon- (Figure S in http://vixra.org/abs/1510.0338). For a left-handed red down quark, say the incoming calalyst boson is a Z- (see Figure C), the quark changes handedness and a 1/2 graviton- is emitted. (Where a 1/2 graviton is a second generation graviton.) The QED-like repulsion in this second generation gravitational interaction will be swamped by the third generation attractive QCD colour forces taking place in in other interactions.