Hamilton et al. have suggested an invaluable scaling formula which describes how the power spectra of density fluctuations evolve into the nonlinear regime of hierarchical clustering. This paper presents an extension of their method to low-density universes and universes with nonzero cosmological constant. We pay particular attention to models with large negative spectral indices, and give a sp...

Turbulence is generally associated with universal power-law spectra in scale ranges without significant drive or damping. Although many examples of turbulent systems do not exhibit such an inertial range, power-law spectra may still be observed. As a simple model for such situations, a modified version of the Kuramoto-Sivashinsky equation is studied. By means of semianalytical and numerical stu...

The spectra of blazars form a sequence which can be parametrized in term of their observed bolometric luminosity. At the most powerful extreme of the sequence we find objects whose jet power can rival the power extracted by accretion, while at the low power end of the sequence we find TeV and TeV candidate blazars, whose spectral properties can give information on the particle acceleration mech...

Art images and natural scenes have in common that their radially averaged (1D) Fourier spectral power falls according to a power-law with increasing spatial frequency (1/f(2) characteristics), which implies that the power spectra have scale-invariant properties. In the present study, we show that other categories of man-made images, cartoons and graphic novels (comics and mangas), have similar ...

We develop a method for estimating the shear power spectra from weak lensing observations and test it on simulated data. Our method describes the shear field in terms of angular power spectra and cross correlation of the two shear modes which differ under parity transformations. Two of the three power spectra can be used to monitor unknown sources of noise in the data. The power spectra are dec...

We present an expression for the nonlinear evolution of the cosmological power spectrum based on following Lagrangian trajectories. This is simpliied using the Zel'dovich approximation to trace particle displacements, assuming Gaussian initial conditions. The model is found to exhibit the transfer of power from large to small scales expected in self-gravitating elds. Some exact solutions are fo...

Taking advantage of the smoothness of CMB Cl power spectra, we derive a simple and model-independent parameterization of their measurement. It allows to describe completely the spectrum, i.e. provide an estimate of the value and the error for any real l point at the percent level, down to low l multipole. We provide this parameterization for WMAP first year data and show that the spectrum is co...

With the recent publication of the measurements of the radiation angular power spectrum from the BOOMERanG Antarctic flight (de Bernardis et al. 2000), it has become apparent that the currently favoured spatially–flat cold dark matter model (matter density parameter Ωm = 0.3, flatness being restored by a cosmological constant ΩΛ = 0.7, Hubble parameter h = 0.65, baryon density parameter Ωbh 2 =...

We provide a simple toy model to elucidate the effects of baryonic cooling on predictions of the convergence power spectrum in weak gravitational lensing. Our model suggests that the effects of baryonic cooling on dark matter halo profiles can alter the dark matter power spectrum at k ∼ 10hMpc and lead to percent level changes in the convergence angular power spectrum at wavenumbers of several ...

The power of blazar jets rivals the power that gravity can extract from accreting matter. The mechanism launching and accelerating jets can be considered as the most efficient engine operating in radio–loud sources. It is still a matter of debate if the jet carries this power to the radio lobes, hundreds of kpc away, in the form of Poynting flux or bulk kinetic energy, or both, and if these two...