11,125 research outputs found
The Quantum McKay Correspondence for polyhedral singularities
Let G be a polyhedral group, namely a finite subgroup of SO(3). Nakamura's
G-Hilbert scheme provides a preferred Calabi-Yau resolution Y of the polyhedral
singularity C^3/G. The classical McKay correspondence describes the classical
geometry of Y in terms of the representation theory of G. In this paper we
describe the quantum geometry of Y in terms of R, an ADE root system associated
to G. Namely, we give an explicit formula for the Gromov-Witten partition
function of Y as a product over the positive roots of R. In terms of counts of
BPS states (Gopakumar-Vafa invariants), our result can be stated as a
correspondence: each positive root of R corresponds to one half of a genus zero
BPS state. As an application, we use the crepant resolution conjecture to
provide a full prediction for the orbifold Gromov-Witten invariants of [C^3/G].Comment: Introduction rewritten. Issue regarding non-uniqueness of conifold
resolution clarified. Version to appear in Inventione
ALMA Thermal Observations of Europa
We present four daytime thermal images of Europa taken with the Atacama Large
Millimeter Array. Together, these images comprise the first spatially resolved
thermal dataset with complete coverage of Europa's surface. The resulting
brightness temperatures correspond to a frequency of 233 GHz (1.3 mm) and a
typical linear resolution of roughly 200 km. At this resolution, the images
capture spatially localized thermal variations on the scale of geologic and
compositional units. We use a global thermal model of Europa to simulate the
ALMA observations in order to investigate the thermal structure visible in the
data. Comparisons between the data and model images suggest that the
large-scale daytime thermal structure on Europa largely results from bolometric
albedo variations across the surface. Using bolometric albedos extrapolated
from Voyager measurements, a homogenous model reproduces these patterns well,
but localized discrepancies exist. These discrepancies can be largely explained
by spatial inhomogeneity of the surface thermal properties. Thus, we use the
four ALMA images to create maps of the surface thermal inertia and emissivity
at our ALMA wavelength. From these maps, we identify a region of either
particularly high thermal inertia or low emissivity near 90 degrees West and 23
degrees North, which appears anomalously cold in two of our images.Comment: 9 pages, 3 figures, accepted for publication in the Astronomical
Journa
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