Limits on Sizes of Fundamental Particles and on Gravitational Mass of a Scalar

We review the experimental limits on mass of excited fundamental particles and contact interaction energy scale parameters $\Lambda$ for QCD, QED and electroweak reactions. In particular we have focused on the QED reaction \EEGG at the energies from 91GeV{} to 202GeV{} using the differential cross-sections measured by the L3 Collaboration from 1991 to 1999. A global fit leads to lower limits at $95$ CL on $\Lambda > 1687$ GeV, which restricts the characteristic QED size of the interaction region to $R_{e} < 1.17 \times 10^{-17}$ cm. All the interaction regions are found to be smaller than the Compton wavelength of the fundamental particles. This constraint is used to estimate a lower limit on the size of a fundamental particle related to gravitational interaction, applying the model of self-gravitating particle-like structure with the de Sitter vacuum core. It gives $r_{\tau} \geq 2.3 \times {10^{-17}}$ cm and $r_{e} \geq 1.5 \times 10^{-18}$ cm, if leptons get masses at the electroweak scale, and $r_{\tau} \geq 3.3 \times {10^{-27}}$ cm, $r_{e} \geq 4.9 \times 10^{-26}$ cm, as the most stringent limits required by causality arguments. This sets also an upper limit on the gravitational mass of a scalar $m_{scalar} \leq{154}$ GeV{} at the electroweak scale and (m_{scalar} \leq \sqrt{3/8} m_{Pl}) as the most stringent limit.Comment: 8 pages, 2 pictures; Minor changes have been mad

Minimal Length Scale in Annihilation

Experimental data suggest the existence of a minimal length scale in annihilation process for the reaction e+e- --> gamma gamma (gamma). Nonlinear electrodynamics coupled to gravity and satisfying the weak energy condition predicts, for an arbitrary gauge invariant lagrangian, the existence of a spinning charged electromagnetic soliton asymptotically Kerr-Newman for a distant observer with a gyromagnetic ratio g=2. Its internal structure includes an equatorial disk of de Sitter vacuum which has properties of a perfect conductor and ideal diamagnetic, and displays superconducting behavior within a single spinning soliton. De Sitter vacuum supplies a particle with the finite positive electromagnetic mass related to breaking of space-time symmetry. We apply this approach to interpret the existence of a minimal characteristic length scale in annihilation.Comment: 16 pages, 3 figure

Multi-horizon spherically symmetric spacetimes with several scales of vacuum energy

We present a family of spherically symmetric multi-horizon spacetimes with a vacuum dark fluid, associated with a time-dependent and spatially inhomogeneous cosmological term. The vacuum dark fluid is defined in a model-independent way by the symmetry of its stress-energy tensor, i.e., its invariance under Lorentz boosts in a distinguished spatial direction ($p_r=-\rho$ for spherical symmetry), which makes the dark fluid essentially anisotropic and allows its density to evolve. The related cosmological models belong to the Lemaitre class of models with anisotropic fluids and describe a universe with several scales of vacuum energy related to phase transitions during its evolution. The typical behavior of solutions and the number of spacetime horizons are determined by the number of vacuum scales. We study in detail a model with three vacuum scales: GUT, QCD and that responsible for the present accelerated expansion. The model parameters are fixed by the observational data and by analyticity and causality conditions. We find that our Universe has three horizons. During the first inflation the Universe enters a T-region which makes the expansion irreversible. After the second phase transition at the QCD scale the Universe enters an R-region, where for a long time its geometry remains almost pseudo-Euclidean. After crossing the third horizon related to the present vacuum density, the Universe should enter the next T-region with inevitable expansion.Comment: 23 pages, 7 figures, accepted for publication in Class. Quantum Gra