Re: The Standard Model and Superstring Theory

Posted by yanniru on February 21, 2004 at 21:07:15:

In Reply to: The Standard Model and Superstring Theory posted by sol on February 21, 2004 at 12:02:27:

The link gave me a 'The page cannot be displayed'.
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However, I can still comment. Lately I have been intriqued by Loop Quantum Gravity which with relatively few workers compared to string theory has been making great strides in explaining the foundation of space time, quantum mechanics and the big bang. It may even predict string theory. Here is a recent review article by one of the leading workers:

http://arxiv.org/abs/gr-qc/0402053
Loop Quantum Cosmology: Recent Progress
Authors: Martin Bojowald
Comments: 17 pages, 2 figures, Plenary talk at ICGC 04, Cochin, India
Report-no: AEI-2004-017
Aspects of the full theory of loop quantum gravity can be studied in a simpler context by reducing to symmetric models like cosmological ones. This leads to several applications where loop effects play a significant role when one is sensitive to the quantum regime. As a consequence, the structure of and the approach to classical singularities are very different from general relativity: The quantum theory is free of singularities, and there are new phenomenological scenarios for the evolution of the very early universe including inflation. We give an overview of the main effects, focussing on recent results obtained by several different groups.

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Here is another that suggests that string theory may be derived from LQG:

http://arxiv.org/abs/hep-th/0401172
The LQG -- String: Loop Quantum Gravity Quantization of String Theory I. Flat Target Space
Authors: Thomas Thiemann
Comments: 46 p., LaTex2e, no figures
Report-no: PI-2004-001
Subj-class: High Energy Physics - Theory; Mathematical Physics

We combine I. background independent Loop Quantum Gravity (LQG) quantization techniques, II. the mathematically rigorous framework of Algebraic Quantum Field Theory (AQFT) and III. the theory of integrable systems resulting in the invariant Pohlmeyer Charges in order to set up the general representation theory (superselection theory) for the closed bosonic quantum string on flat target space. While we do not solve the, expectedly, rich representation theory completely, we present a, to the best of our knowledge new, non -- trivial solution to the representation problem. This solution exists 1. for any target space dimension, 2. for Minkowski signature of the target space, 3. without tachyons, 4. manifestly ghost -- free (no negative norm states), 5. without fixing a worldsheet or target space gauge, 6. without (Virasoro) anomalies (zero central charge), 7. while preserving manifest target space Poincar\'e invariance and 8. without picking up UV divergences. The existence of this stable solution is exciting because it raises the hope that among all the solutions to the representation problem (including fermionic degrees of freedom) we find stable, phenomenologically acceptable ones in lower dimensional target spaces, possibly without supersymmetry, that are much simpler than the solutions that arise via compactification of the standard Fock representation of the string. Moreover, these new representations could solve some of the major puzzles of string theory such as the cosmological constant problem. The solution presented in this paper exploits the flatness of the target space in several important ways. In a companion paper we treat the more complicated case of curved target spaces.

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But if you have read this far let me tell you about Cahill. If LQG is leading edge physics, then Cahill is beyond that edge. It seems to me that his Process Physics may be the phenomenology of LQG. As far as I can tell he is not yet taken seriously by the physics community, as his work is a modification of Newton's theory of gravity, which accounts for the dark matter effects without any extra mass. But it seems very consistent with LQG.

Here is his most recent paper:

http://arxiv.org/abs/physics/0401047
Gravitation, the 'Dark Matter' Effect and the Fine Structure Constant
Authors: Reginald T. Cahill (Flinders University)
Comments: 11 pages, 3 eps figures. Globular cluster M15 and G1 `black hole' masses correctly predicted. Spiral galaxy analysis fixed
Subj-class: General Physics

Gravitational anomalies such as the mine/borehole g anomaly, the near-flatness of the spiral galaxy rotation-velocity curves, currently interpreted as a `dark matter' effect, the absence of that effect in ordinary elliptical galaxies, and the ongoing problems in accurately determining Newton's gravitational constant G_N are explained by a generalisation of the Newtonian theory of gravity to a fluid-flow formalism with one new dimensionless constant. By analysing the borehole data this constant is shown to be the fine structure constant alpha=1/137. The spiral galaxy `dark matter' effect and the globular cluster `black hole' masses are then correctly predicted. This formalism also explains the cause of the long-standing uncertainties in G_N and leads to the introduction of a fundamental gravitational constant G not = G_N with value G=(6.6526 +/- 0.013)x 10^-11 m^3s^{-2}kg^{-1}. The occurrence of alpha implies that space has a quantum structure, and we have the first evidence of quantum gravity effects.

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