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Publications
Publications (116)
This paper seeks to check the validity of the "apparent fractal conjecture" (Ribeiro 2001ab: gr-qc/9909093, astro-ph/0104181), which states that the observed power-law behaviour for the average density of large-scale distribution of galaxies arises when some observational quantities, selected by their relevance in average density profile determinat...
We derive the time evolution of the density contrast to all orders of perturbation theory, by solving the Einstein equation for scale-invariant fluctuations. These fluctuations are represented by an infinite series in inverse powers of the radial parameter. In addition to the standard growing modes, we find infinitely many more new growing modes fo...
The evolution of inhomogeneities in a spherical collapse model is studied by expanding the Einstein equation in powers of inverse radial parameter. In the linear regime, the density contrast is obtained for flat, closed and open universes. In addition to the usual modes, an infinite number of new growing modes are contained in the solutions for pre...
We write a non-relativistic Lagrangian for a hierarchical universe. The
equations of motion are solved numerically and the evolution of the fractal
dimension is obtained for different initial conditions. We show that our model
is homogeneous at the time of the last scattering, but evolves into a
self-similar universe with a remarkably constant frac...
Decay amplitudes for mesons in two-dimensional QCD are discussed. We show that in spite of an infinite number of conserved charges, particle production is not entirely suppressed. This phenomenon is explained in terms of quantum corrections to the combined algebra of higher-conserved and spectrum-generating currents. We predict the qualitative form...
It is shown that density fluctuations obey a scaling law in an open Friedmann universe. In a flat universe, the fluctuations are not scale-invariant. We compute the growth rate of adiabatic scale-invariant density fluctuations in flat, open and inflationary universes. We find that, given a sufficiently long time, the density perturbations decay awa...
We use de Vaucouleurs' power-law density-distance relation, to study a hierarchical perturbation of the Friedmann universe. We solve the Einstein equation and obtain the density contrast and the amplification factor for the perturbation. It is shown that, scale-invariant inhomogeneities decay in Einstein-de-Sitter universe. On the contrary, in an o...
The semi-classical phase structure of two-dimensional QED and QCD are briefly reviewed. The non-abelian theory is reformulated to closely resemble the Schwinger model. It is shown that, contrary to the abelian theory, the phase structure of two-dimensional QCD is unaffected by the structure of the theta vacuum. We make parallel calculations in the...
Decay amplitudes for mesons in two-dimensional QCD are discussed. We show that in spite of an infinite number of conserved charges, particle production is not entirely suppressed. This phenomenon is explained in terms of quantum corrections to the combined algebra of higher-conserved and spectrum-generating currents. We predict the qualitative form...
We discuss the issue of screening and confinement of external colour charges in bosonised two-dimensional quantum chromodynamics. Our computation relies on the static solutions of the semi-classical equations of motion. The significance of the different representations of the matter field is explicitly studied. We arrive at the conclusion that the...
The one-loop anomalies for chiral $W_{3}$ gravity are derived using the Fujikawa regularisation method. The expected two-loop anomalies are then obtained by imposing the Wess-Zumino consistency conditions on the one-loop results. The anomalies found in this way agree with those already known from explicit Feynman diagram calculations. We then direc...
We consider the anomalies of W∞ gravity in the context
of path-integral quantization. We derive the ghost-loop anomalies to all
orders in h directly from the path-integral measure by the Fujikawa
method. We also show that in the matter sector the higher-loop anomalies
can be obtained by implementation of the Wess-Zumino consistency
condition using...
We reformulate the BRST quantisation of chiral Virasoro and $W_3$ worldsheet gravities. Our approach follows directly the classic BRST formulation of Yang-Mills theory in employing a derivative gauge condition instead of the conventional conformal gauge condition, supplemented by an introduction of momenta in order to put the ghost action back into...