17,593 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 âpromptâ) black hole formation in the collapse of ordinary massive stars (8M_â âČ M_(ZAMS) âČ 100 M_â) present first results from black hole formation simulations that include rotation
OGY Control of Haken Like Systems on Different Poincare Sections
The Chua system, the Lorenz system, the Chen system and The L\"u system are
chaotic systems that their state space equations is very similar to Haken
system which is a nonlinear model of a optical slow-fast system. These
Haken-Like Sys-tems have very similar properties. All have two slow but
unstable eigenvalues and one fastest but stable eigenvalue. This lets that an
approximation of slow manifold be equivalent with unstable manifold of the
system. In other hand, control of discreet model of the system on a defined
manifold (Poincare map) is main essence of some important control methods of
chaotic systems for example OGY method. Here, by using different methods of
defining slow manifold of the H-L systems the efficiency of the OGY control for
stabilizing problem investigated.Comment: 4 page
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
Ethical aspects of emissions trading: Contribution to the World Council of Churches Consultation on Equity and Emission Trading - Ethical and Theological Dimensions, Saskatoon, Canada, May 9-14, 2000
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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 âSouth-North Dialogue â Equity in the Greenhouse". Slightly modifying the original approach the level of reduction targets is determined by the two criteria of âresponsibility" and âpotential" to mitigate. Obligations to provide financial and technological resources to developing countries, on the other hand, are to be assigned according to the âcapability" criteria. --
Spectrum of the Andreev Billiard and Giant Fluctuations of the Ehrenfest Time
The density of states in the semiclassical Andreev billiard is theoretically
studied and shown to be determined by the fluctuations of the classical
Lyapunov exponent . The rare trajectories with a small value of
give rise to an anomalous increase of the Ehrenfest time
and, consequently, to the appearance of
Andreev levels with small excitation energy. The gap in spectrum is obtained
and fluctuations of the value of the gap due to different positions of
superconducting lead are considered.Comment: 4 pages, 3 figure
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