77,208 research outputs found
Clustered Massive Star Formation in Molecular Clouds
I review some important questions in the field of massive star formation:
What are the initial conditions for proto star clusters and how do they arise?
What are the initial conditions for individual massive star formation within
star clusters? How do massive protostars accumulate their mass? I compare the
Turbulent Core Model (McKee & Tan 2003) to several nearby regions, including
Orion KL. Here I also discuss the origin of BN's high proper motion.Comment: 10 pages, 2 figures, invited review, to appear in "Massive Star Birth
- A Crossroads of Astrophysics" (CUP), eds. R. Cesaroni, E. Churchwell, M.
Felli, and C. M. Walmsle
Fire from Ice - Massive Star Birth from Infrared Dark Clouds
I review massive star formation in our Galaxy, focusing on initial conditions
in Infrared Dark Clouds (IRDCs), including the search for massive pre-stellar
cores (PSCs), and modeling of later stages of massive protostars, i.e., hot
molecular cores (HMCs). I highlight how developments in astrochemistry, coupled
with rapidly improving theoretical/computational and observational capabilities
are helping to improve our understanding of the complex process of massive star
formation.Comment: To appear in proceedings of IAU Symp. 322, Astrochemistry VII Through
the Cosmos from Galaxies to Planet
A heterotic sigma model with novel target geometry
We construct a (1,2) heterotic sigma model whose target space geometry
consists of a transitive Lie algebroid with complex structure on a Kaehler
manifold. We show that, under certain geometrical and topological conditions,
there are two distinguished topological half--twists of the heterotic sigma
model leading to A and B type half--topological models. Each of these models is
characterized by the usual topological BRST operator, stemming from the
heterotic (0,2) supersymmetry, and a second BRST operator anticommuting with
the former, originating from the (1,0) supersymmetry. These BRST operators
combined in a certain way provide each half--topological model with two
inequivalent BRST structures and, correspondingly, two distinct perturbative
chiral algebras and chiral rings. The latter are studied in detail and
characterized geometrically in terms of Lie algebroid cohomology in the
quasiclassical limit.Comment: 83 pages, no figures, 2 references adde
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