801 research outputs found
Directly Interacting Massless Particles - a Twistor Approach
Twistor phase spaces are used to provide a general description of the
dynamics of a finite number of directly interacting massless spinning particles
forming a closed relativistic massive and spinning system with an internal
structure. A Poincare invariant canonical quantization of the so obtained
twistor phase space dynamics is performed.Comment: LaTeX, approx. 16 pages; to appear in Journal of Mathematical
Physics, March or April 1996 issu
On a class of consistent linear higher spin equations on curved manifolds
We analyze a class of linear wave equations for odd half spin that have a well posed initial value problem. We demonstrate consistency of the equations in curved space-times. They generalize the Weyl neutrino equation. We show that there exists an associated invariant exact set of spinor fields indicating that the characteristic initial value problem on a null cone is formally solvable, even for the system coupled to general relativity. We derive the general analytic solution in flat space by means of Fourier transforms. Finally, we present a twistor contour integral description for the general analytic solution and assemble a representation of the group on the solution space
Cognitive Load of Rating Scales
Why does Netflix.com use star ratings, Digg.com use up/down votes and Face- book use a “like” but not a “dislike” button? In this paper, we extend existing research on rating scales with findings from an experiment we ran to measure the cognitive load users experience while rating. In this paper, we analyze the cognitive load and time required by different rating scales. Our analysis draws upon 14,000 movie and product ratings we collected from 348 users through an online survey. In the survey, we measured the speed and cognitive load users ex- perience under four scales: unary (‘like it’), binary (thumbs up / thumbs down), five-star, and a 100-point slider. We compare a variety of measures of cognitive load and rating speed, and draw conclusions for user interface designers based on our results. Our advice to designers is grounded in the responses from users regarding their opinions of scales, the existing research, and in the models we build of the data collected from the experiment
Negative forms and path space forms
We present an account of negative differential forms within a natural
algebraic framework of differential graded algebras, and explain their
relationship with forms on path spaces.Comment: 12 pp.; the Introduction has been rewritten and mention of cohomology
dropped in Proposition 3.2; material slightly reorganize
Aircraft NO(x) had no Unique Fingerprint on Sonex; Lightning Dominated Fresh NO(x) Sources
Key questions to which SONEX was directed were the following: Can aircraft corridors be detected? Is there a unique tracer for aircraft NO(x)? Can a "background" NO(x) (or NO(y) be defined? What fraction of NO(x) measured during SONEX was from aircraft? How representative was SONEX of the North Atlantic in 1997 and how typical of other years? We attempt to answer these questions through species-species correlations, probability distribution functions (PDFs), and meteorological history. There is not a unique aircraft tracer, largely due to the high variability of air mass origins and tracer ratios, which render "average" quantities meaningless. The greatest NO and NO(y) signals were associated with lightning and convective NO sources. Well-defined background CO, NO(y) and NO(y)/ozone ratio appear in subsets of two cross-track flights with subtropical origins and five flights with predominantly mid-latitude air. Forty percent of the observations on these 7 flights showed NO(y)/ozone to be above background, evidently due to unreacted NO(x). This NO(x) is a combination of aircraft, lightning and surface pollution injected by convection. The strongly subtropical signatures in SONEX observations, confirmed by pv (potential vorticity) values along flight tracks, argues for most of the unreacted NO(x) originating from lightning. Potential vorticity statistics along SONEX flight tracks in 1992-1998, and for the North Atlantic as a whole, show the SONEX meteorological environment to be representative of the North Atlantic flight corridor in the October-November period
Twistors, special relativity, conformal symmetry and minimal coupling - a review
An approach to special relativistic dynamics using the language of spinors
and twistors is presented. Exploiting the natural conformally invariant
symplectic structure of the twistor space, a model is constructed which
describes a relativistic massive, spinning and charged particle, minimally
coupled to an external electro-magnetic field. On the two-twistor phase space
the relativistic Hamiltonian dynamics is generated by a Poincare scalar
function obtained from the classical limit (appropriately defined by us) of the
second order, to an external electro-magnetic field minimally coupled, Dirac
operator. In the so defined relativistic classical limit there are no Grassman
variables. Besides, the arising equation that describes dynamics of the
relativistic spin differs significantly from the so called Thomas Bergman
Michel Telegdi equation.Comment: 39 pages, no figures, few erronous statements (not affecting anything
else in the papper) on page 23 delete
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