The turbulent stresses that lead to angular momentum transport in accretion discs have often been treated as resulting from an isotropic effective viscosity, related to the pressure through the alpha parametrization of Shakura & Sunyaev. This simple approach may be adequate for the simplest aspects of accretion disc theory, and was necessitated historically by an incomplete understanding of the...

Context. Circumstellar discs are expected to be the nursery of planets. Grain growth within such discs is the first step in the planet formation process. The Bok globule CB 26 harbours such a young disc. Aims. We present a detailed model of the edge-on circumstellar disc and its envelope in the Bok globule CB 26. Methods. The model is based on HST near-infrared maps in the I, J, H, and K bands,...

Context. Circumstellar discs are expected to be the nursery of planets. Grain growth within such discs is the first step in the planet formation process. The Bok globule CB 26 harbours such a young disc. Aims. We present a detailed model of the edge-on circumstellar disc and its envelope in the Bok globule CB 26. Methods. The model is based on HST near-infrared maps in the I, J, H, and K bands,...

In a recent important paper, Papaloizou & Pringle (1984) have investigated the dynamical stability of a thick, differentially rotating disc of uniform entropy and uniform specific angular momentum. They find a strong global non-axisymmetric instability which grows on a dynamical time-scale. Here we show that a similar instability exists even in thin discs of arbitrary specific angular momentum....

We present stationary solutions of geometrically thick discs (or tori) endowed with a self-consistent toroidal magnetic field distribution surrounding non-rotating black hole in an analytical, static, spherically-symmetric $f(R)$-gravity background. These models introduce Yukawa-like modification to the Newtonian potential, encoded single parameter $\delta$ which controls strength modified pote...

Stellar-mass binary black holes (BBHs) embedded in active galactic nucleus (AGN) discs are possible progenitors of black-hole mergers detected gravitational waves by LIGO/VIRGO. To better understand the hydrodynamical evolution BBHs interacting with disc gas, we perform a suite high-resolution 2D simulations binaries local (shearing-box) models, considering various mass ratios, eccentricities a...

The objective of the present work is to evaluate the suitability of using 3D digital image correlation (DIC) for measuring strains on high-speed flywheels. A two-camera DIC setup was used to characterize the effect of image blur on de-correlation and to measure strains on the surface of three 32-cm diameter plastic disks rotating in air at low speeds (2,000 rpm). In one set of experiments, imag...

We present numerical simulations of axisymmetric magnetised massive tori around rotating black holes taking into account the energy losses due to emission of neutrinos. A realistic equation of state is used which takes into account the energy losses due to dissociation of nuclei. The heating due to neutrino-antineutrino annihilation is not included. We study the cases of optically thick, semitr...

The initial stages of planet formation in circumstellar gas discs proceed via dust grains that collide and build up larger and larger bodies1. How this process continues from metre-sized boulders to kilometre-scale planetesimals is a major unsolved problem2: boulders stick together poorly3, and spiral into the protostar in a few hundred orbits due to a head wind from the slower rotating gas4. G...