62,013 research outputs found
An Open Mapping Theorem
It is proved that any surjective morphism onto a
locally compact group is open for every cardinal . This answers a
question posed by Karl Heinrich Hofmann and the second author
Infrared photometry of interacting galaxies
Imperial Users onl
High-Temperature Processing of Solids Through Solar Nebular Bow Shocks: 3D Radiation Hydrodynamics Simulations with Particles
A fundamental, unsolved problem in Solar System formation is explaining the
melting and crystallization of chondrules found in chondritic meteorites.
Theoretical models of chondrule melting in nebular shocks has been shown to be
consistent with many aspects of thermal histories inferred for chondrules from
laboratory experiments; but, the mechanism driving these shocks is unknown.
Planetesimals and planetary embryos on eccentric orbits can produce bow shocks
as they move supersonically through the disk gas, and are one possible source
of chondrule-melting shocks. We investigate chondrule formation in bow shocks
around planetoids through 3D radiation hydrodynamics simulations. A new
radiation transport algorithm that combines elements of flux-limited diffusion
and Monte Carlo methods is used to capture the complexity of radiative
transport around bow shocks. An equation of state that includes the rotational,
vibrational, and dissociation modes of H is also used. Solids are followed
directly in the simulations and their thermal histories are recorded. Adiabatic
expansion creates rapid cooling of the gas, and tail shocks behind the embryo
can cause secondary heating events. Radiative transport is efficient, and bow
shocks around planetoids can have luminosities few
L. While barred and radial chondrule textures could be produced in
the radiative shocks explored here, porphyritic chondrules may only be possible
in the adiabatic limit. We present a series of predicted cooling curves that
merit investigation in laboratory experiments to determine whether the solids
produced by bow shocks are represented in the meteoritic record by chondrules
or other solids.Comment: Accepted for publication in ApJ. Images have been resized to conform
to arXiv limits, but are all readable upon adjusting the zoom. Changes from
v1: Corrected typos discovered in proofs. Most changes are in the appendi
An Architectural Approach to Managing Knowledge Stocks and Flows: Implications for Reinventing the HR Function
Sustainable competitive advantage is increasingly dependent upon a firm’s ability to manage both its knowledge stocks and flows. We examine how different employees’ knowledge stocks are managed within a firm and how—through their recombination and renewal—those stocks can create sustainable competitive advantage. To do this, we first establish an architectural framework for managing human resources and review how the framework provides a foundation for studying alternative employment arrangements used by firms in allocating knowledge stocks. Next, we extend the architecture by examining how knowledge stocks (human capital) can be both recombined and renewed through cooperative and entrepreneurial archetypes. We then position two HR configurations to focus on facilitating these two archetypes. By identifying and managing different forms of social capital across employee groups within the architecture, HR practices can facilitate the flow of knowledge within the firm, which ultimately leads to sustainable competitive advantage
Conformal anomaly from gauge fields without gauge fixing
We show how the Weyl anomaly generated by gauge fields, can be computed from
manifestly gauge invariant and diffeomorphism invariant exact renormalization
group equations, without having to fix the gauge at any stage. Regularisation
is provided by covariant higher derivatives and by embedding the Maxwell field
into a spontaneously broken supergauge theory. We first provide a
realisation that leaves behind two versions of the original gauge field,
and then construct a manifestly supergauge invariant flow equation
which leaves behind only the original Maxwell field in the spontaneously broken
regime.Comment: 24 page
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