相关论文: Aspect Ratio Dependence of the Free-Fall Time for …

Molecular clouds often exhibit filamentary or sheet-like shapes. We compute the free-fall time ($\tff$) for finite, uniform, self-gravitating circular sheets and filamentary clouds of small but finite thickness, so that their volume density…

The onset of star formation is set by the collapse of filaments in the interstellar medium. From a theoretical point of view, an isolated cylindrical filament forms cores via the edge effect. Due to the self-gravity of a filament, the…

Using numerical simulations, we investigate the gravitational evolution of filamentary molecular cloud structures and their condensation into dense protostellar cores. One possible process is the so called 'edge effect', the pile-up of…

When a self-gravitating spherical gas cloud collapses or accretes onto a central mass, the inner region of the cloud develops a density profile $\rho\propto r^{-3/2}$ and the velocity approaches free-fall. We show that in this region,…

We analytically investigate the modes of gravity-induced star formation possible in idealized finite molecular clouds where global collapse competes against both local Jeans instabilities and discontinuous edge instabilities. We examine…

A comparison of accretion and (turbulent) magnetic diffusion timescales for sheets and filaments demonstrates that dense star-forming clouds generally will -- under realistic conditions -- become supercritical due to mass accretion on…

Theoretically, stars have been formed from the collapse of cores in the molecular clouds. Historically, the core had been assumed as an singular isothermal sphere (SIS), and the collapse had been investigated by a self-similar manner. This…

We present the first detailed classification of the structures of Class 0 cores in a high resolution simulation of a giant molecular cloud. The simulated cloud contains 10^4 solar masses and produces over 350 cores which allows for…

With a view to understand the galaxy/star formation scenario, we investigate the dissipative collapse of a spherical cluster of gas clouds with an isotropic velocity distribution. The time scale for collapse to one tenth radius is studied…

We study analytically the process of a topological texture collapse in the approximation of a scaling ansatz in the nonlinear sigma-model. In this approximation we show that in flat space-time topological texture eventually collapses while…

We find the collapse of columns of granular rods to show range of behaviors that depends on particle aspect ratio (length $L$ to diameter $d$) and initial pile geometry (height/radius). For all aspect ratios $L/d$ below 24 there exists a…

Properties of candidate stars, forming out of molecular clouds, depend on the ambient conditions of the parent cloud. We present a series of 2D and 3D simulations of fragmentation of molecular clouds in starburst regions as well as clouds…

We examine the role of space-time geometry in the non-adiabatic collapse of a star dissipating energy in the form of radial heat flow, studying its evolution under different initial conditions. The collapse of a star with interior…

We present two-dimensional simulations of finite, self-gravitating gaseous sheets. Unlike the case of infinite sheets, such configurations do not constitute equilibrium states but instead are subject to global collapse unless countered by…

The effect of halo substructures on galaxy rotation curves is investigated in this paper using a simple model of dark matter clustering. A dark matter halo density profile is developed based only on the scale free nature of clustering that…

The flow rate of a granulate out of a cylindrical container is studied as a function of particle shape for flat and elongated ellipsoids experimentally and numerically. We find a nonmonotonic dependence of the flow rate on the grain aspect…

Dynamically significant magnetic fields are routinely observed in molecular clouds, with mass-to-flux ratio lambda = (2 pi sqrt{G}) (Sigma/B) ~ 1 (here Sigma is the total column density and B is the field strength). It is widely believed…

Gravity plays important roles in the evolution of molecular clouds. We present an acceleration mapping method to estimate the acceleration induced by gravitational interactions in molecular clouds based on observational data. We find that…

The classical picture of a star-forming filament is a near-equilibrium structure, with collapse dependent on its gravitational criticality. Recent observations have complicated this picture, revealing filaments as a mess of apparently…

We investigate the evolution of non-adiabatic collapse of a shear-free spherically symmetric stellar configuration with anisotropic stresses accompanied with radial heat flux. The collapse begins from a curvature singularity with infinite…