Recent email to Dr Chris Oakley, with an update added in red. The string theory approach to QFT (quantum gravity, superforce unification, SUSY) is extremely illucid and disconnected from reality.

I've quoted a section from an old (1961) book on 'Relativistic Electron Theory' at http://electrogravity.blogspot.com/2006/02/standard-model-says-mass-higgs-field.html:

''The solution to the difficulty of negative energy states [in relativistic quantum mechanics] is due to Dirac [P. A. M. Dirac, Proc. Roy. Soc. (London), A126, p360, 1930]. One defines the vacuum to consist of no occupied positive energy states and all negative energy states completely filled. This means that each negative energy state contains two electrons. An electron therefore is a particle in a positive energy state with all negative energy states occupied. No transitions to these states can occur because of the Pauli principle. The interpretation of a single unoccupied negative energy state is then a particle with positive energy ... It will be apparent that a hole in the negative energy states is equivalent to a particle with the same mass as the electron ... The theory therefore predicts the existence of a particle, the positron, with the same mass and opposite charge as compared to an electron. It is well known that this particle was discovered in 1932 by Anderson [C. D. Anderson, Phys. Rev., 43, p491, 1933].

'Although the prediction of the positron is certainly a brilliant success of the Dirac theory, some rather formidable questions still arise. With a completely filled 'negative energy sea' the complete theory (hole theory) can no longer be a single-particle theory.

'The treatment of the problems of electrodynamics is seriously complicated by the requisite elaborate structure of the vacuum. The filled negative energy states need produce no observable electric field. However, if an external field is present the shift in the negative energy states produces a polarisation of the vacuum and, according to the theory, this polarisation is infinite.

'In a similar way, it can be shown that an electron acquires infinite inertia (self-energy) by the coupling with the electromagnetic field which permits emission and absorption of virtual quanta. More recent developments show that these infinities, while undesirable, are removable in the sense that they do not contribute to observed results [J. Schwinger, Phys. Rev., 74, p1439, 1948, and 75, p651, 1949; S. Tomonaga, Prog. Theoret. Phys. (Kyoto), 1, p27, 1949].

'For example, it can be shown that starting with the parameters e and m for a bare Dirac particle, the effect of the 'crowded' vacuum is to change these to new constants e' and m', which must be identified with the observed charge and mass. ... If these contributions were cut off in any reasonable manner, m' - m and e' - e would be of order alpha ~ 1/137. No rigorous justification for such a cut-off has yet been proposed.

'All this means that the present theory of electrons and fields is not complete. ... The particles ... are treated as 'bare' particles. For problems involving electromagnetic field coupling this approximation will result in an error of order alpha. As an example ... the Dirac theory predicts a magnetic moment of mu = mu[zero] for the electron, whereas a more complete treatment [including Schwinger's coupling correction, i.e., the first Feynman diagram] of radiative effects gives mu = mu[zero].(1 + alpha/{twice Pi}), which agrees very well with the very accurate measured value of mu/mu[zero] = 1.001...'

This kind of clear-cut physics is more appealing to me than string theory about extra dimensions and such like. There is some evidence that masses for the known particles, can be described by a a two-step mechanism. First, virtual particles in the vacuum (most likely trapped neutral Z particles, 91 GeV mass) interact with one another by radiation by give rise to mass (a kind of Higgs field). Secondly, real charges can associate with a trapped Z particle either inside or outside the polarised veil of virtual charges around the real charge core: http://electrogravity.blogspot.com/2006/02/standard-model-says-mass-higgs-field.html

The polarised charge around either a trapped Z particle (OK it is neutral over all, but so is the photon, and the photon's EM cycle is half positive electric field and half negative, in Maxwell's model of light, so a neutral particle still has electric fields when considering the close-in picture) gives a shielding factor of 137, with an additional factor of twice Pi for some sort of geometric reason, possibly connected to spin/magnetic polarisation. If you spin a loop as seen edge-on, the exposure it receives per unit area falls by a factor of Pi, compared to a non-spinning cylinder, and we are dealing with exchange of gauge bosons like radiation to create forces between spinning particles. The electron loop has spin 1/2, so it rotates 720 degrees to cover a complete revolution like a Mobius strip loop. Thus, it has a reduction factor of twice Pi as seen edge on, and the magnetic alignment which increases the magnetic moment of the electron means that the core electron and the virtual charge in the vacuum are aligned side-on.

Z-boson mass: 91 GeVMuon mass (electron with a Higg's boson/trapped Z-boson inside its veil): 91 / (2.Pi.137) = 105.7 MeV.Electron mass (electron with a Higg's boson/trapped Z-boson outside its veil): 91 / [(1.5).(137).(2.Pi.137)] = 0.51 MeV.
Most hadron masses are describable by (0.511 Mev).(137/2)n(N + 1) = 35n(N + 1) Mev where n and N are integers, with a similar sort of heuristic explanation (as yet incomplete in details): http://feynman137.tripod.com/

Supersymmetry can be completely replaced by physical mechanism and energy conservation of the field bosons:

Supersymmetry is not needed at all because the physical mechanism by which nuclear and electroweak forces unify at high energy automatically leads to perfect unification, due to conservation of energy: as you smash particles together harder, they break through the polarised veil around the cores, exposing a higher core charge so the electromagnetic force increases. My calculation at http://electrogravity.blogspot.com/2006/02/heisenbergs-uncertainty-sayspd-h2.html suggests that the core charge is 137 times the observed (long range) charge of the electron. However, simple conservation of potential energy for the continuously-exchanged field of gauge bosons shows that this increase in electromagnetic field energy must be conpensated for by a reduction in other fields as collision energy increases. This will reduce the core charge (and associated strong nuclear force) from 137 times the low-energy electric charge, compensating for the rising amount of energy carried by the electromagnetic field of the charge at long distances.

Hence, in sufficiently high energy collisions, the unified force will be some way intermediate in strength between the low-energy electromagnetic force and the low-energy strong nuclear force. The unified force will be attained where the energy is sufficient to completely break through the polarised shield around the charge cores, possibly at around 10^16 GeV as commonly suggested. A proper model of the physical mechanism would get rid of the Standard Model problems of unification (due to incomplete approximations used to extrapolate to extremely high energy): http://electrogravity.blogspot.com/2006/02/heuristic-explanation-of-short-ranged_27.html

So I don't think there is any scientific problem with sorting out force unification without SUSY in the Standard Model, or of including gravity (http://feynman137.tripod.com/). The problem lies entirely with the mainstream preoccupation with string theory. Once the mainstream realises it was wrong, instead of admitting it was wrong, it will just use its preoccupation with string theory as the excuse for having censored alternative ideas.

The problem is whether Dr Peter Woit can define crackpottery to both include the mainstream string theory, and exclude some alternatives which look far-fetched or crazy but have a more realistic change of being tied to facts, and making predictions which can be tested. With string theory, Dr Woit finds scientific problems. I think the same should be true of alternatives, which should be judged on scientific criteria. The problem is that the mainstream stringers don't use scientific grounds to judge either their own work or alternatives. They say they are right because they are a majority, and alternatives are wrong because they are in a minority.