5,457 research outputs found
Educating physicians in the era of genomic medicine
Michael F Murray, MD, of Geisinger Health System in Pennsylvania discusses how to meet the need for better training for physicians in genomics as it moves further into the clinic
The general caloron correspondence
We outline in detail the general caloron correspondence for the group of
automorphisms of an arbitrary principal -bundle over a manifold ,
including the case of the gauge group of . These results are used to define
characteristic classes of gauge group bundles. Explicit but complicated
differential form representatives are computed in terms of a connection and
Higgs field.Comment: 25 pages. New section added containing example
A Geometric Model for Odd Differential K-theory
Odd -theory has the interesting property that it admits an infinite number
of inequivalent differential refinements. In this paper we provide a bundle
theoretic model for odd differential -theory using the caloron
correspondence and prove that this refinement is unique up to a unique natural
isomorphism. We characterise the odd Chern character and its transgression form
in terms of a connection and Higgs field and discuss some applications. Our
model can be seen as the odd counterpart to the Simons-Sullivan construction of
even differential -theory. We use this model to prove a conjecture of
Tradler-Wilson-Zeinalian regarding a related differential extension of odd
-theoryComment: 36 page
From the Top Down and Back Up Again: Star Cluster Structure from Hierarchical Star Formation
Young massive star clusters spanning in mass have
been observed to have similar surface brightness profiles. Recent
hydrodynamical simulations of star cluster formation have also produced star
clusters with this structure. We argue analytically that this type of mass
distribution arises naturally in the relaxation from a hierarchically-clustered
distribution of stars into a monolithic star cluster through hierarchical
merging. We show that arbitrary initial profiles will tend to converge to a
universal profile under hierarchical merging, owing to phase-space mixing
obeying certain conservation constraints. We perform -body simulations of a
pairwise merger of model star clusters and find that mergers readily produce
the shallow surface brightness profiles observed in young massive clusters.
Finally, we simulate the relaxation of a hierarchically-clustered mass
distribution constructed from an idealized fragmentation model. Assuming only
power-law spatial and kinematic scaling relations, these numerical experiments
are able to reproduce the surface density profiles of observed young massive
star clusters. Thus we provide physical motivation for the structure of young
massive clusters within the paradigm of hierarchical star formation. This has
important implications for the structure of nascent globular clusters.Comment: 16 pages, 10 figure
Planning for disaster management and vulnerability reduction in the fisheries sector of Caribbean Island States
Circle actions, central extensions and string structures
The caloron correspondence can be understood as an equivalence of categories
between -bundles over circle bundles and -bundles where
is the group of smooth loops in . We use it, and lifting bundle gerbes,
to derive an explicit differential form based formula for the (real) string
class of an -bundle.Comment: 25 page
When Feedback Fails: The Scaling and Saturation of Star Formation Efficiency
We present a suite of 3D multi-physics MHD simulations following star
formation in isolated turbulent molecular gas disks ranging from 5 to 500
parsecs in radius. These simulations are designed to survey the range of
surface densities between those typical of Milky Way GMCs (\sim 10^2
M_\odot\,pc^{-2}}) and extreme ULIRG environments (\sim 10^2
M_\odot\,pc^{-2}}) so as to map out the scaling of the cloud-scale star
formation efficiency (SFE) between these two regimes. The simulations include
prescriptions for supernova, stellar wind, and radiative feedback, which we
find to be essential in determining both the instantaneous per-freefall
() and integrated () star formation
efficiencies. In all simulations, the gas disks form stars until a critical
stellar surface density has been reached and the remaining gas is blown out by
stellar feedback. We find that surface density is a good predictor of
, as suggested by analytic force balance arguments from
previous works. SFE eventually saturates to at high surface density.
We also find a proportional relationship between and
, implying that star formation is feedback-moderated even over
very short time-scales in isolated clouds. These results have implications for
star formation in galactic disks, the nature and fate of nuclear starbursts,
and the formation of bound star clusters. The scaling of with
surface density is not consistent with the notion that is
always on the scale of GMCs, but our predictions recover the value for GMC parameters similar to those found in sprial galaxies,
including our own.Comment: 21 pages, 7 figures. Accepted to MNRA
The caloron correspondence and higher string classes for loop groups
We review the caloron correspondence between -bundles on
and -bundles on , where is the space of smooth loops in
the compact Lie group . We use the caloron correspondence to define
characteristic classes for -bundles, called string classes, by
transgression of characteristic classes of -bundles. These generalise the
string class of Killingback to higher dimensional cohomology.Comment: 21 pages. Author addresses adde
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