19,078 research outputs found
Update on the Pyramid Scheme
We summarize recent work in which we attempt to make a consistent model of
LHC physics, from the Pyramid Scheme. The models share much with the NMSSM, in
particular, enhanced tree level contributions to the Higgs mass and a
preference for small tan {\beta}. There are 3 different singlet fields, and a
new strongly coupled gauge theory, so the constraints of perturbative
unification are quite different. We outline our general approach to the model,
which contains a Kahler potential for three of the low energy fields, which is
hard to calculate. Detailed calculations, based on approximations to the Kahler
potential, will be presented in a future publication.Comment: LaTeX 2e/ 9 page
UK household portfolios
This paper presents a detailed analysis of the composition of household portfolios, usingboth aggregate and micro-data. Among the key findings are that:• Most household wealth is held in the form of housing and pensions. Over time, there hasbeen a shift away from housing towards financial assets, driven largely by the growth inlife and pension funds.• Liquid financial wealth (excluding life and pension funds) is not predominantly held inrisky form. By far the most commonly held asset is an interest-bearing account at a bankor building society account. Of people with positive (liquid) financial wealth, more thanhalf is held in savings accounts.• The importance of risky assets in an individual’s portfolio varies according to theircharacteristics. The unconditional portfolio share held in risky assets (i.e. averagedacross those with and without any risky assets) rises with both age and total financialwealth. However, most of the variation in unconditional portfolio shares is due todifferences in ownership rates as opposed to the proportion of the portfolio held in riskyassets. Looking only at the people within each wealth decile who have risky assets, theconditional portfolio share is relatively constant across wealth, suggesting a possible rolefor entry costs or other fixed costs in explaining portfolio holdings. Multivariate analysisshows that the conditional portfolio share in risky assets actually falls with age asclassical portfolio theory would predict.• Finally, the tax treatment of savings products has an effect on portfolio choice. Separateprobit regressions for the ownership of tax-favoured assets and similar assets without thetax exemption, show that, controlling for other factors, marginal tax rates are important in determining asset ownership. These results are in accordance with those found by Poterba in the US
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Binocular Eye Movements Are Adapted to the Natural Environment.
Humans and many animals make frequent saccades requiring coordinated movements of the eyes. When landing on the new fixation point, the eyes must converge accurately or double images will be perceived. We asked whether the visual system uses statistical regularities in the natural environment to aid eye alignment at the end of saccades. We measured the distribution of naturally occurring disparities in different parts of the visual field. The central tendency of the distributions was crossed (nearer than fixation) in the lower field and uncrossed (farther) in the upper field in male and female participants. It was uncrossed in the left and right fields. We also measured horizontal vergence after completion of vertical, horizontal, and oblique saccades. When the eyes first landed near the eccentric target, vergence was quite consistent with the natural-disparity distribution. For example, when making an upward saccade, the eyes diverged to be aligned with the most probable uncrossed disparity in that part of the visual field. Likewise, when making a downward saccade, the eyes converged to enable alignment with crossed disparity in that part of the field. Our results show that rapid binocular eye movements are adapted to the statistics of the 3D environment, minimizing the need for large corrective vergence movements at the end of saccades. The results are relevant to the debate about whether eye movements are derived from separate saccadic and vergence neural commands that control both eyes or from separate monocular commands that control the eyes independently.SIGNIFICANCE STATEMENT We show that the human visual system incorporates statistical regularities in the visual environment to enable efficient binocular eye movements. We define the oculomotor horopter: the surface of 3D positions to which the eyes initially move when stimulated by eccentric targets. The observed movements maximize the probability of accurate fixation as the eyes move from one position to another. This is the first study to show quantitatively that binocular eye movements conform to 3D scene statistics, thereby enabling efficient processing. The results provide greater insight into the neural mechanisms underlying the planning and execution of saccadic eye movements
A dynamic model of democratic elections in multidimensional policy spaces
We propose a general model of repeated elections. In each period, a challenger is chosen from the electorate to run against an incumbent politician in a majority-rule election, and the winner then selects a policy from a multidimensional policy space. Individual policy preferences are private information, whereas policy choices are publicly observable. We prove existence and continuity of equilibria in "simple" voting and policy strategies; we provide examples to show the variety of possible equilibrium patterns in multiple dimensions; we analyze the effects of patience and office-holding benefits on the persistence of policies over time; and we identify relationships between equilibrium policies and the core of the underlying voting game. As a byproduct of our analysis, we show how equilibrium incentives maylead elected representatives to make policy compromises, even when binding commitments are unavailable. We provide an informational story for incumbency advantage. Finally, we give an asymptotic version of the median voter theorem for the one-dimensional model as voters become-arbitrarily patient
A Stringy Correspondence Principle in Cosmology
We study a d-dimensional FRW universe, containing a perfect fluid with p = w
\rho and \frac{1} {d - 1} \le w \le 1, and find a correspondence principle
similar to that of Horowitz and Polchinski in the black hole case. This
principle follows quite generally from thermodynamics and the conservation of
energy momentum tensor, and can be stated along similar lines as in the black
hole case: ``When the temperature T of the universe becomes of order string
scale the universe state becomes a highly excited string state. At the
transition, the entropies and energies of the universe and strings differ by
factors of {\cal O}(1).'' Such a matching is absent for w \ne 1 if the
transition is assumed to be when the curvature or the horizon length is of
order string scale.Comment: 14 pages. V2: More references added and some minor textual
modifications mad
A General Bargaining Model of Legislative Policy-making
We present a general model of legislative bargaining in which the status quo is an arbitrary point in a multidimensional policy space. In contrast to other bargaining models, the status quo is not assumed to be bad for all legislators, and delay may be Pareto efficient. We prove existence of stationary equilibria. We show that if all legislators are risk averse or if even limited transfers are possible, then delay is only possible if the status quo lies in the core. Thus, we expect immediate agreement in multidimensional models, where the core is typically empty. In one dimension, delay is possible if and only if the status quo lies in the core of the voting rule, and then it is the only possible outcome. Our comparative statics analysis yield two noteworthy insights: moderate status quos imply moderate policy outcomes, and legislative patience implies policy moderation
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The Perceptual Consequences of Curved Screens
Flat panels are by far the most common type of television screen. There are reasons, however, to believe that curved screens create a greater sense of immersion, reduce distracting reflections, and minimize some perceptual distortions that are commonplace with large televisions. To examine these possibilities, we calculated how curving the screen affects the field of view and the probability of seeing reflections of ambient lights. We find that screen curvature has a small beneficial effect on field of view and a large beneficial effect on the probability of seeing reflections. We also collected behavioral data to characterize perceptual distortions in various viewing configurations. We find that curved screens can in fact reduce problematic perceptual distortions on large screens, but that the benefit depends on the geometry of the projection on such screens
Ion thruster accelerator system Patent
Development and characteristics of ion thruster accelerator with single glass coated grid to provide increased ion extraction capability and larger diameter accelerator syste
Making Sense Of The New Cosmology
Over the past three years we have determined the basic features of the
Universe -- spatially flat; accelerating; comprised of 1/3 a new form of
matter, 2/3 a new form of energy, with some ordinary matter and a dash of
massive neutrinos; and apparently born from a burst of rapid expansion during
which quantum noise was stretched to astrophysical size seeding cosmic
structure. The New Cosmology greatly extends the highly successful hot big-bang
model. Now we have to make sense of all this: What is the dark matter particle?
What is the nature of the dark energy? Why this mixture? How did the matter --
antimatter asymmetry arise? What is the underlying cause of inflation (if it
indeed occurred)?Comment: 17 pages Latex (sprocl.sty). To appear in the Proceedings of 2001: A
Spacetime Odyssey (U. Michigan, May 2001, World Scientific
A Pyramid Scheme for Particle Physics
We introduce a new model, the Pyramid Scheme, of direct mediation of SUSY
breaking, which is compatible with the idea of Cosmological SUSY Breaking
(CSB). It uses the trinification scheme of grand unification and avoids
problems with Landau poles in standard model gauge couplings. It also avoids
problems, which have recently come to light, associated with rapid stellar
cooling due to emission of the pseudo Nambu-Goldstone Boson (PNGB) of
spontaneously broken hidden sector baryon number. With a certain pattern of
R-symmetry breaking masses, a pattern more or less required by CSB, the Pyramid
Scheme leads to a dark matter candidate that decays predominantly into leptons,
with cross sections compatible with a variety of recent observations. The dark
matter particle is not a thermal WIMP but a particle with new strong
interactions, produced in the late decay of some other scalar, perhaps the
superpartner of the QCD axion, with a reheat temperature in the TeV range. This
is compatible with a variety of scenarios for baryogenesis, including some
novel ones which exploit specific features of the Pyramid Scheme.Comment: JHEP Latex, 32 pages, 1 figur
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