Aspherical gravitational monopoles

We show how to construct non-spherically-symmetric extended bodies of uniform density behaving exactly as pointlike masses. These ``gravitational monopoles'' have the following equivalent properties: (i) they generate, outside them, a spherically-symmetric gravitational potential $M/|x - x_O|$; (ii) their interaction energy with an external gravitational potential $U(x)$ is $- M U(x_O)$; and (iii) all their multipole moments (of order $l \geq 1$) with respect to their center of mass $O$ vanish identically. The method applies for any number of space dimensions. The free parameters entering the construction are: (1) an arbitrary surface $\Sigma$ bounding a connected open subset $\Omega$ of $R^3$; (2) the arbitrary choice of the center of mass $O$ within $\Omega$; and (3) the total volume of the body. An extension of the method allows one to construct homogeneous bodies which are gravitationally equivalent (in the sense of having exactly the same multipole moments) to any given body.Comment: 55 pages, Latex , submitted to Nucl.Phys.

Nonlocality in kinetic roughening

We propose a phenomenological equation to describe kinetic roughening of a growing surface in presence of long range interactions. The roughness of the evolving surface depends on the long range feature, and several distinct scenarios of phase transitions are possible. Experimental implications are discussed.Comment: Replaced with the published version (Phys. Rev. Lett 79, 2502 (1997)). Eq. 1 written in a symmetrical form, references update

Web dynamics

The global usage and continuing exponential growth of the World Wide Web poses a host of challenges to the research community. In particular, there is an urgent need to understand and manage the dynamics of the Web, in order to develop new techniques that will make the Web tractable. MARK LEVENE and ALEXANDRA POULOVASSILIS provide an overview of recent statistics relating to the size of the Web graph and its growth. They then briefly review some of the key areas relating to Web dynamics with reference to the recent literature. Finally, they summarise the talks given in a recent workshop devoted to Web dynamics, which was held in the beginning of January 2001 at the University of London

Web dynamics

The global usage and continuing exponential growth of the World Wide Web poses a host of challenges to the research community. In particular, there is an urgent need to understand and manage the dynamics of the Web, in order to develop new techniques that will make the Web tractable. MARK LEVENE and ALEXANDRA POULOVASSILIS provide an overview of recent statistics relating to the size of the Web graph and its growth. They then briefly review some of the key areas relating to Web dynamics with reference to the recent literature. Finally, they summarise the talks given in a recent workshop devoted to Web dynamics, which was held in the beginning of January 2001 at the University of London