Learn More
This paper studies the dynamical evolution of young groups/clusters, with N = 100 − 1000 members, from their embedded stage out to ages of ∼ 10 Myr. We use N-body simulations to explore how their evolution depends on the system size N and the initial conditions. Motivated by recent observations suggesting that stellar groups begin their evolution with(More)
A pseudo-Nambu-Goldstone boson, with a potential of the form V (φ) = Λ 4 [1 ± cos(φ/f)], can naturally give rise to an epoch of inflation in the early universe, if f ∼ M P l and Λ ∼ M GU T. Such mass scales arise in particle physics models with a gauge group that becomes strongly interacting at the GUT scale. We explore the particle physics basis for these(More)
This paper outlines astrophysical issues related to the long term fate of the universe. We consider the evolution of planets, stars, stellar populations, galaxies, and the universe itself over time scales which greatly exceed the current age of the universe. Our discussion starts with new stellar evolution calculations which follow the future evolution of(More)
This paper explores orbits in extended mass distributions and develops an analytic approximation scheme based on epicycloids (spirograph patterns). We focus on the Hernquist potential ¼ 1/(1 þ), which provides a good model for many astrophysical systems, including elliptical galaxies (with an R 1/4 law), dark matter halos (where N-body simulations indicate(More)
When stars form within small groups (with N ⋆ ≈ 100 − 500 members), their cir-cumstellar disks are exposed to relatively little EUV (hν > 13.6 eV) radiation but a great deal of FUV (6 eV < hν < 13.6 eV) radiation (∼ 10 3 times the local interstellar FUV field) from the most massive stars in the group. This paper calculates the mass loss rates and(More)
The favored theoretical explanation for giant planet formation – in both our solar system and others – is the core accretion model (although it still has some serious difficulties). In this scenario, planetesimals accumulate to build up planetary cores, which then accrete nebular gas. With current opacity estimates for protoplanetary envelopes, this model(More)