This article addresses some issues related to statistical description of gravitating systems in an expanding backgrounds. In particular, I describe (a) how the non linear mode-mode coupling transfers power from one scale to another in the Fourier space if the initial power spectrum is sharply peaked at a given scale and (b) what are the asymptotic characteristics of gravitational clustering tha...

We show that the distribution of the sizes and temperatures of clusters can be used to constrain cosmological models. The size-temperature (ST) distribution predicted in a flat Gaussian cluster-abundance-normalized Ω0 = 0.3 model agrees well with the fairly tight ST relation observed. A larger power-spectrum amplitude σ8 would give rise to a larger scatter about the ST relation as would a large...

We discuss the determination of the linear power spectrum of dark matter fluctuations from measurements of the transmitted flux Ly-α Forest power spectrum. We show that at most scales probed by current measurements, the flux power spectrum is significantly affected by non-linear corrections to the linear dark matter power spectrum due to gravitational clustering. Inferring the linear dark matte...

Instabilities for a coasting proton beam interacting with electron cloud are discussed. The electron sources are roughly classified into two categories reflecting their initial conditions: that is, the electrons produced at the chamber surface and/or at the beam position. If the beam is stable, it forms a Coulomb static potential around itself. Electrons produced near the beam position are trap...

We use a representative sample of 65 galaxy clusters observed with the Einstein IPC to constrain the range of cluster X{ray morphologies. We develop and apply quantitative and reproducible measures to constrain the intrinsic distributions of (i) emission weighted centroid variation w ~x , (ii) emission weighted axial ratio , (iii) emission weighted orientation o , and (iv) measures of the radia...

For homogeneous initial conditions, Hartree (gaussian) dynamical approximations are known to have problems with thermalization, because of insufficient scattering. We attempt to improve on this by writing an arbitrary density matrix as a superposition of gaussian pure states and applying the Hartree approximation to each member of such an ensemble. Particles can then scatter via their back-reac...

Causal seed models, such as cosmological defects, generically predict a distinctly different structure to the CMB power spectrum than inflation, due to the behavior of the perturbations outside the horizon. We provide a general analysis of their causal generation from isocurvature initial conditions by analyzing the role of stress perturbations and conservation laws in the causal evolution. As ...

In this work we study the inflammatory process resulting in the development of atherosclerosis. We develop a oneand two-dimensional models based on reaction-diffusion systems to describe the set up of a chronic inflammatory response in the intima of an artery vessel wall. The concentration of the oxidized low density lipoproteins (ox-LDL) in the intima is the critical parameter of the model. Lo...

The correlation function (r) of matter in the non-linear regime is assumed to be determined by the density prooles (r) and the mass distribution n(M) of virialized halos. The Press{Schechter approach is used to compute n(M), and the stable clustering hypothesis is used to determine the density prooles of these Press{Schechter halos. Thus, the shape and amplitude of (r) on small scales is relate...

The possibility of unifying dark-matter and dark-energy has recently attracted considerable interest. In this so called quartessence scenario, a single component is responsible for both the clustering of matter and the accelerated expansion of the universe. A model archetype for such scenario is provided by the Chaplygin gas. Although this model is in agreement with the data on the expansion hi...