The angular momentum of galaxies is routinely ascribed to a process of tidal torques acting during the early stages of gravitational collapse, and is predicted from the initial mass distribution using second-order perturbation theory and the Zel’dovich approximation. We have tested this theory for a flat hierarchical cosmogony using a large N -body simulation with sufficient dynamic range to in...

I compare theoretical models of massive star formation with observations of the Orion Hot Core, which harbors one of the closest massive protostars. Although this region is complicated, many of its features (size, luminosity, accretion disk, H II region, outflow) may be understood by starting with a simple model in which the star forms from a massive gas core that is a coherent entity in approx...

A first-principles statistical theory is constructed for the evolution of two dimensional interfaces in Laplacian fields. The aim is to predict the pattern that the growth evolves into, whether it becomes fractal and if so the characteristics of the fractal pattern. Using a time dependent map the growing region is conformally mapped onto the unit disk and the problem is converted to the dynamic...

In the course of trying to further understand the world around him, man repeatedly attempts to find explanations for observed physical phenomena . This scenario applies to both scientists working in the laboratory and non-scientists assimilating everyday experiences . People don't carry around a full theory of the world in their heads; they make conjectures as a result of everyday experiences ....

Members of an assembly that chooses policies on a series of multidimensional ideological issues have incentives to coalesce and coordinate their votes, forming political parties. If an agent has an advantage to organize a party at a lower cost, a unique party forms and the policy outcome moves away from the Condorcet winning policy, to the benefit of party members. If all agents have the same o...

The ”bag”-like spherically symmetrical solutions of the Chiral Born-Infeld theory are studied. The properties of these solutions are obtained, and a possible physical interpretation is also discussed. PACS number(s): 12.39.Dc, 12.39.Fe, 05.45.Yv, 11.27.+d, 11.30.Qc

Concept learning is challenging in part because the meanings of many concepts depend on their relationships to other concepts. Learning these concepts in isolation can be difficult, but we present a model that discovers entire systems of related concepts. These systems can be viewed as simple theories that specify the concepts that exist in a domain, and the laws or principles that relate these...

These lecture notes discuss several topics in the physics of cosmic structure formation starting from the evolution of small-amplitude fluctuations in the radiation-dominated era. The topics include relativistic cosmological perturbation theory with the scalar-vector-tensor decomposition, the evolution of adiabatic and isocurvature initial fluctuations, microwave background anisotropy, spatial ...

Existing . ma~!ti n~ le~!1g. tec~que~ .have only limited capabi1ities of handling computadonally intractable domaim-This research extends explanation-based learning techniques in order ωovercom~ such limitatio~. It is _ based ona strategy of sacrificing 阳。可 accura句 in 时'~er to gain f:Tactabi!ity.. In~ctab~e theories are a-pproxima时 by m∞,rporati~~ simplify~ng_ assumptions. Explanations of teach...