Particle theory

Abstract:

Attempts at building an unified description of the strong, weak and electromagnetic interactions usually involve several stages of spontaneous symmetry breaking. We consider the effects of such symmetry breaking during an era of primordial inflation in supergravity models. In cases that these occur along flat directions at intermediate scales there will be a succession of short bursts of inflation which leave a distinctive signature in the spectrum of the generated scalar density perturbation. Thus measurements of the spectral index can directly probe the structure of unified theories at very high energy scales. An observed feature in the power spectrum of galaxy clustering from the APM survey may well be associated with such structure. If so, this implies a characteristic suppression of the secondary Doppler peaks in the angular power spectrum of temperature fluctuations in the cosmic microwave background.

Abstract:

We compare the mass spectra and string tensions of SU(2), SU(3) and SU(4) gauge theories in 2+1 dimensions. We find that the ratios of masses are, to a first approximation, independent of Nc and that the remaining dependence can be accurately reproduced by a simple O(1/N2c) correction. This provides us with a prediction of these mass ratios for all SU(Nc) theories in 2+1 dimensions and demonstrates that these theories are 'close' to Nc = ∞ for Nc ≥ 2. We also find that, when expressed in units of the dynamical length scale of the theory, the dimensionful coupling g2 is proportional to 1/Nc at large Nc. We confirm that these theories are indeed confining in the limit Nc → ∞. We describe preliminary calculations in 3+1 dimensions which indicate that the same will be true there. © 1997 Elsevier Science B.V.

Abstract:

We consider new objects in bosonic open string theory -- ND tadpoles, which have N(euman) boundary conditions at one end of the world-sheet and D(irichlet) at the other, must exist due to s-t duality in a string theory with both NN strings and D-branes. We demonstrate how to interpolate between N and D boundary conditions. In the case of mixed boundary conditions the action for a quantum particle is induced on the boundary. Quantum-mechanical particle-wave duality, a dual description of a quantum particle in either the coordinate or the momentum representation, is induced by world-sheet T-duality. The famous relation between compactification radii is equivalent to the quantization of the phase space area of a Planck cell. We also introduce a boundary operator - a ``Zipper'' which changes the boundary condition from N into D and vice versa.