128,448 research outputs found
Computational Processes and Incompleteness
We introduce a formal definition of Wolfram's notion of computational process
based on cellular automata, a physics-like model of computation. There is a
natural classification of these processes into decidable, intermediate and
complete. It is shown that in the context of standard finite injury priority
arguments one cannot establish the existence of an intermediate computational
process
How People Think About Distributing Aid
This paper examines how people think about aiding others in a way that can inform both theory and practice. It uses data gathered from Kiva, an online, non-profit organization that allows individuals to aid other individuals around the world, to isolate intuitions that people find broadly compelling. The central result of the paper is that people seem to give more priority to aiding those in greater need, at least below some threshold. That is, the data strongly suggest incorporating both a threshold and a prioritarian principle into the analysis of what principles for aid distribution people accept. This conclusion should be of broad interest to aid practitioners and policy makers. It may also provide important information for political philosophers interested in building, justifying, and criticizing theories about meeting needs using empirical evidence
Vevacious: A Tool For Finding The Global Minima Of One-Loop Effective Potentials With Many Scalars
Several extensions of the Standard Model of particle physics contain
additional scalars implying a more complex scalar potential compared to that of
the Standard Model. In general these potentials allow for charge and/or color
breaking minima besides the desired one with correctly broken SU(2)_L times
U(1)_Y . Even if one assumes that a metastable local minimum is realized, one
has to ensure that its lifetime exceeds that of our universe. We introduce a
new program called Vevacious which takes a generic expression for a one-loop
effective potential energy function and finds all the tree-level extrema, which
are then used as the starting points for gradient-based minimization of the
one-loop effective potential. The tunneling time from a given input vacuum to
the deepest minimum, if different from the input vacuum, can be calculated. The
parameter points are given as files in the SLHA format (though is not
restricted to supersymmetric models), and new model files can be easily
generated automatically by the Mathematica package SARAH. This code uses
HOM4PS2 to find all the minima of the tree-level potential, PyMinuit to follow
gradients to the minima of the one-loop potential, and CosmoTransitions to
calculate tunneling times.Comment: 44 pages, 1 figure, manual for publicly available software, v2
corresponds to version accepted for publication in EPJC [clearer explanation
of scale dependence and region of validity, explicit mention that SLHA files
should have blocks matching those expected by model files, updated
references
Detecting opportunities for parallel observations on the Hubble Space Telescope
The presence of multiple scientific instruments aboard the Hubble Space Telescope provides opportunities for parallel science, i.e., the simultaneous use of different instruments for different observations. Determining whether candidate observations are suitable for parallel execution depends on numerous criteria (some involving quantitative tradeoffs) that may change frequently. A knowledge based approach is presented for constructing a scoring function to rank candidate pairs of observations for parallel science. In the Parallel Observation Matching System (POMS), spacecraft knowledge and schedulers' preferences are represented using a uniform set of mappings, or knowledge functions. Assessment of parallel science opportunities is achieved via composition of the knowledge functions in a prescribed manner. The knowledge acquisition, and explanation facilities of the system are presented. The methodology is applicable to many other multiple criteria assessment problems
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