7,957 research outputs found
Fedosov supermanifolds: II. Normal coordinates
The study of recently introduced Fedosov supermanifolds is continued. Using
normal coordinates, properties of even and odd symplectic supermanifolds
endowed with a symmetric connection respecting given sympletic structure are
studied.Comment: 12 pages, Late
An automatic electrical distribution system
Computer controlled electric power distribution system for aerospace system
Boson-fermion mappings for odd systems from supercoherent states
We extend the formalism whereby boson mappings can be derived from
generalized coherent states to boson-fermion mappings for systems with an odd
number of fermions. This is accomplished by constructing supercoherent states
in terms of both complex and Grassmann variables. In addition to a known
mapping for the full so(2+1) algebra, we also uncover some other formal
mappings, together with mappings relevant to collective subspaces.Comment: 40 pages, REVTE
New Ambitwistor String Theories
We describe new ambitwistor string theories that give rise to the recent
amplitude formulae for Einstein-Yang-Mills, (Dirac)-Born-Infeld, Galileons and
others introduced by Cachazo, He and Yuan. In the case of the
Einstein-Yang-Mills amplitudes, an important role is played by a novel
worldsheet conformal field theory that provides the appropriate colour factors
precisely without the spurious multitrace terms of earlier models that had to
be ignored by hand. This is needed to obtain the correct multitrace terms that
arise when Yang-Mills is coupled to gravity.Comment: 34 pages, 2 figures, 5 tables. v2: minor changes, published versio
The occurance of pronounced salinity variations in Lousiana coastal waters
The chloride-ion contents of more than 700 sea water samples from the coastal waters of western Louisiana were converted to salinity values and were used in a study of the salinity characteristics. These data were gathered from seven drilling platforms during a period of 14 months in a zone paralleling the coast for about 60 miles, approximately 6 to 8 miles offshore and in depths varying between 40 and 50 feet. The chloride-ion content was determined by the standard chemical titration method in connection with quality control of salt water drilling mud used in the drilling of offshore oil wells...
Strengths and Weaknesses of Parallel Tempering
Parallel tempering, also known as replica exchange Monte Carlo, is studied in
the context of two simple free energy landscapes. The first is a double well
potential defined by two macrostates separated by a barrier. The second is a
`golf course' potential defined by microstates having two possible energies
with exponentially more high energy states than low energy states. The
equilibration time for replica exchange is analyzed for both systems. For the
double well system, parallel tempering with a number of replicas that scales as
the square root of the barrier height yields exponential speedup of the
equilibration time. On the other hand, replica exchange yields only marginal
speed-up for the golf course system. For the double well system, the free
energy difference between the two wells has a large effect on the equilibration
time. Nearly degenerate wells equilibrate much more slowly than strongly
asymmetric wells. It is proposed that this difference in equilibration time may
lead to a bias in measuring overlaps in spin glasses. These examples illustrate
the strengths and weaknesses of replica exchange and may serve as a guide for
understanding and improving the method in various applications.Comment: 18 pages, 4 figures. v2: typos fixed and wording changes to improve
clarit
What pops out in positional priming of pop-out: insights from event-related EEG lateralizations
It is well established that, in visual pop-out search, reaction time (RT) performance is influenced by cross-trial repetitions versus changes of target-defining attributes. One instance of this is referred to as “positional priming of pop-out” (pPoP; Maljkovic and Nakayama, 1996). In positional PoP paradigms, the processing of the current target is examined depending on whether it occurs at the previous target or a previous distractor location, relative to a previously empty location (“neutral” baseline), permitting target facilitation and distractor inhibition to be dissociated. The present study combined RT measures with specific sensory- and motor-driven event-related lateralizations to track the time course of four distinct processing levels as a function of the target’s position across consecutive trials. The results showed that, relative to targets at previous target and “neutral” locations, the appearance of a target at a previous distractor location was associated with a delayed build-up of the posterior contralateral negativity wave, indicating that distractor positions are suppressed at early stages of visual processing. By contrast, presentation of a target at a previous target, relative to “neutral” and distractor locations, modulated the elicitation of the subsequent stimulus-locked lateralized readiness potential wave, indicating that post-selective response selection is facilitated if the target occurred at the same position as on the previous trial. Overall, the results of present study provide electrophysiological evidence for the idea that target location priming (RT benefits) does not originate from an enhanced coding of target saliency at repeated (target) locations; instead, they arise (near-) exclusively from processing levels subsequent to focal-attentional target selection
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