14,691 research outputs found
Studies of Stellar Collapse and Black Hole Formation with the Open-Source Code GR1D
We discuss results from simulations of black hole formation in failing core-collapse supernovae performed with the code GR1D, a new open-source Eulerian spherically-symmetric general-relativistic hydrodynamics code. GR1D includes rotation in an approximate way (1.5D) comes with multiple finite-temperature nuclear equations of state (EOS), and treats neutrinos in the post-core-bounce phase via a 3-flavor leakage scheme and a heating prescription. We chose the favored K_0 = 220 MeV-variant of the Lattimer & Swesty (1990) EOS and present collapse calculations using the progenitor models of Limongi & Chieffi (2006). We show that there is no direct (or “prompt”) black hole formation in the collapse of ordinary massive stars (8M_☉ ≲ M_(ZAMS) ≲ 100 M_☉) present first results from black hole formation simulations that include rotation
Seasonal adjustment of the money supply
Seasonal variations (Economics) ; Business cycles
Statistically Locked-in Transport Through Periodic Potential Landscapes
Classical particles driven through periodically modulated potential energy
landscapes are predicted to follow a Devil's staircase hierarchy of
commensurate trajectories depending on the orientation of the driving force.
Recent experiments on colloidal spheres flowing through arrays of optical traps
do indeed reveal such a hierarchy,but not with the predicted structure. The
microscopic trajectories, moreover,appear to be random, with commensurability
emerging only in a statistical sense. We introduce an idealized model for
periodically modulated transport in the presence of randomness that captures
both the structure and statistics of such statistically locked-in states.Comment: REVTeX with EPS figures, 4 pages, 4 figure
Taking the lead: post-2012 climate targets for the North: towards adequate and equitable future climate commitments for industrialised countries
Any definition of adequacy consistent with the objective of the Climate Convention will require increased mitigation efforts in industrialized countries far beyond those levels agreed in Kyoto. This paper, therefore, focuses on future reduction targets for industrialised (Annex I) countries. It starts with an assessment of mid- and long-term targets already adopted in industrialised countries against the backdrop of required emission cuts to keep climate change within tolerable limits. Taking into account their heterogeneous national circumstances, the main part of the paper presents a method for differentiating Annex I countries with a view to assigning future mitigation and financial transfer commitments. This differentiation exercise is based on an analytical approach that was developed in the project “South-North Dialogue – Equity in the Greenhouse". Slightly modifying the original approach the level of reduction targets is determined by the two criteria of “responsibility" and “potential" to mitigate. Obligations to provide financial and technological resources to developing countries, on the other hand, are to be assigned according to the “capability" criteria. --
The emergence of coherence in complex networks of heterogeneous dynamical systems
We present a general theory for the onset of coherence in collections of
heterogeneous maps interacting via a complex connection network. Our method
allows the dynamics of the individual uncoupled systems to be either chaotic or
periodic, and applies generally to networks for which the number of connections
per node is large. We find that the critical coupling strength at which a
transition to synchrony takes place depends separately on the dynamics of the
individual uncoupled systems and on the largest eigenvalue of the adjacency
matrix of the coupling network. Our theory directly generalizes the Kuramoto
model of equal strength, all-to-all coupled phase oscillators to the case of
oscillators with more realistic dynamics coupled via a large heterogeneous
network.Comment: 4 pages, 1 figure. Published versio
Synchronization in networks of networks: the onset of coherent collective behavior in systems of interacting populations of heterogeneous oscillators
The onset of synchronization in networks of networks is investigated.
Specifically, we consider networks of interacting phase oscillators in which
the set of oscillators is composed of several distinct populations. The
oscillators in a given population are heterogeneous in that their natural
frequencies are drawn from a given distribution, and each population has its
own such distribution. The coupling among the oscillators is global, however,
we permit the coupling strengths between the members of different populations
to be separately specified. We determine the critical condition for the onset
of coherent collective behavior, and develop the illustrative case in which the
oscillator frequencies are drawn from a set of (possibly different)
Cauchy-Lorentz distributions. One motivation is drawn from neurobiology, in
which the collective dynamics of several interacting populations of oscillators
(such as excitatory and inhibitory neurons and glia) are of interest.Comment: The original was replaced with a version that has been accepted to
Phys. Rev. E. The new version has the same content, but the title, abstract,
and the introductory text have been revise
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