The behaviour of a population of honeybees on an artificial and on a natural crop

One hundred and twelve Petri dishes filled with sugar syrup were arranged at 20 yd. intervals from each other in a meadow. Individual bees were observed to visit one chosen dish with great regularity for one or more days, provided that the supply did not become exhausted. Occasionally bees maŕked on one dish were observed to visit an adjacent dish. This occurred most frequently when the supply of syrup temporarily failed at the original site of feeding, but, even after a 3-day interruption in the syrup supply bees often returned to feed at the original site. Bees feeding at a dish full of syrup spent only a fraction of their time (about 1 min.) per visit drinking, but several times as long flying to and from the hive and delivering their load. When the supply of syrup in a dish became exhausted all the bees accustomed to visit that dishgradually accumulated there impatiently seeking for food; after some minutes they extended their radius of search, and many located another source near at hand. Thereafter they visited either the new source or the old, or both, when the syrup at the original site was replenished. The nearer such a new source was to the original one the more likely a bee was to find it; a dish 20 yd. away from the original site was quickly found despite the fact that such a second dish would seldom be visited if the syrup at the original site was constantly maintained. Bees were deterred from collecting syrup from dishes placed even partially in shade; they veryseldom worked beneath the shade of trees. There were even some indications that they prefered not to fly in the direction of shady trees. Over the range of distances covered (160-400 yd.) there were always more visitors to the nearer than to the more distant dishes. The extent of this difference, however, varied from day to day. Bees accustomed to collect syrup from the dishes farthest from the hive did not move to sites nearer home when the weather became unfavourable. There was some evidence, however, that bees working a long way away from the hive were more easily deterred, from foraging by unfavourable weather than those working close to the apiary. When two different concentrations of syrup were offered in different groups of dishes simultaneously the number of visitors to the dishes containing the syrup of high concentration rose considerably higher than that of the visitors to the dishes containing low-concentration syrup; even after all the dishes had been refilled with syrup of uniform concentration on the following day, this difference remained noticeable. Bees marked on a patch of willow-herb (Epilobium angustifolium) situated in the midst of a large crop of this plant, were usually recovered within 5 yd. of the point of marking. Such bees remained ‘fixed’ to this area for several days. Observations were made upon isolated patches of the cultivated thistle; Echinops sphaerocephalus, of bees which continued to visit the patches upon which they were marked for periods up to 16 days. The majority of the bees working the patches showed great constancy: and of such regular visitors the percentage per day observed to stray to other patches of Echinops 18 yd. away was comparatively small. The time spent by foraging bees upon the flowerheads of Echinops on any one visit greatly exceeded the time spent in collecting syrup from a dish (20-60 min. as against 1 min.); but the time spent in flying between the hive and the flowers, or dish, and unloading was approximately equal in each case. Only a small proportion of the population of bees working on a particular dish could be found feeding there at any one time, whereas on a patch of flowering plants, under good weather conditions, most of the population visiting that patch would be found there at any one time. This great difference in behaviour on dishes as compared with plants must be borne in mind in any attempt to draw conclusions from dish experiments as to the behaviour of bees

Cosmic microwave background snapshots: pre-WMAP and post-WMAP

Abbreviated: We highlight the remarkable evolution in the CMB power spectrum over the past few years, and in the cosmological parameters for minimal inflation models derived from it. Grand unified spectra (GUS) show pre-WMAP optimal bandpowers are in good agreement with each other and with the one-year WMAP results, which now dominate the L < 600 bands. GUS are used to determine calibrations, peak/dip locations and heights, and damping parameters. These CMB experiments significantly increased the case for accelerated expansion in the early universe (the inflationary paradigm) and at the current epoch (dark energy dominance) when they were combined with `prior' probabilities on the parameters. A minimal inflation parameter set is applied in the same way to the evolving data. Grid-based and and Monte Carlo Markov Chain methods are shown to give similar values, highly stable over time and for different prior choices, with the increasing precision best characterized by decreasing errors on uncorrelated parameter eigenmodes. After marginalizing over the other cosmic and experimental variables for a weak+LSS prior, the pre-WMAP data of Jan03 cf. the post-WMAP data of Mar03 give Omega_{tot} =1.03^{+0.05}_{-0.04} cf. 1.02^{+0.04}_{-0.03}. Adding the flat prior, n_s =0.95^{+0.07}_{-0.04} cf. 0.97^{+0.02}_{-0.02}, with < 2\sigma evidence for a log variation of n_s. The densities have concordance values. The dark energy pressure-to-density ratio is not well constrained by our weak+LSS prior, but adding SN1 gives w_Q < -0.7. We find \sigma_8 = 0.89^{+0.06}_{-0.07} cf. 0.86^{+0.04}_{-0.04}, implying a sizable SZ effect; the high L power suggest \sigma_8 \sim 0.94^{+0.08}_{-0.16} is needed to be SZ-compatible.Comment: 36 pages, 5 figures, 5 tables, Jan 2003 Roy Soc Discussion Meeting on `The search for dark matter and dark energy in the Universe', published PDF (Oct 15 2003) is http://www.cita.utoronto.ca/~bond/roysoc03/03TA2435.pd

Dark Matter: Introduction

This short review was prepared as an introduction to the Royal Society's 'Dark Matter' conference. It addresses the embarrassing fact that 95% of the universe is unaccounted for. Favoured dark matter candidates are axions or weakly-interacting particles that have survived from the very early universe, but more exotic options cannot be excluded. Experimental searches are being made for the 'dark' particles but we have indirect clues to their nature too. Comparisons of data (from, eg, gravitational lensing) with numerical simulations of galaxy formation can constrain (eg) the particle velocities and collision cross sections. The mean cosmic density of dark matter (plus baryons) is now pinned down to be only about 30% of the critical density However, other recent evidence -- microwave background anisotropies, complemented by data on distant supernovae -- reveals that our universe actually is 'flat', and that its dominant ingredient (about 70% of the total mass-energy) is something quite unexpected -- 'dark energy' pervading all space, with negative pressure. We now confront two mysteries: (i) Why does the universe have three quite distinct basic ingredients -- baryons, dark matter and dark energy -- in the proportions (roughly) 5%, 25% and 70%? (ii) What are the (almost certainly profound) implications of the 'dark energy' for fundamental physics?Comment: 10 pages, 1 figure. Late

Large-scale structure and matter in the universe

This paper summarizes the physical mechanisms that encode the type and quantity of cosmological matter in the properties of large-scale structure, and reviews the application of such tests to current datasets. The key lengths of the horizon size at matter-radiation equality and at last scattering determine the total matter density and its ratio to the relativistic density; acoustic oscillations can diagnose whether the matter is collisionless, and small-scale structure or its absence can limit the mass of any dark-matter relic particle. The most stringent constraints come from combining data on present-day galaxy clustering with data on CMB anisotropies. Such an analysis breaks the degeneracies inherent in either dataset alone, and proves that the universe is very close to flat. The matter content is accurately consistent with pure Cold Dark Matter, with about 25% of the critical density, and fluctuations that are scalar-only, adiabatic and scale-invariant. It is demonstrated that these conclusions cannot be evaded by adjusting either the equation of state of the vacuum, or the total relativistic density.Comment: 17 Pages. Review paper from the January 2003 Royal Society Discussion Meeting, "The search for dark matter and dark energy in the universe

Precise calibration of LIGO test mass actuators using photon radiation pressure

Precise calibration of kilometer-scale interferometric gravitational wave detectors is crucial for source localization and waveform reconstruction. A technique that uses the radiation pressure of a power-modulated auxiliary laser to induce calibrated displacements of one of the ~10 kg arm cavity mirrors, a so-called photon calibrator, has been demonstrated previously and has recently been implemented on the LIGO detectors. In this article, we discuss the inherent precision and accuracy of the LIGO photon calibrators and several improvements that have been developed to reduce the estimated voice coil actuator calibration uncertainties to less than 2 percent (1-sigma). These improvements include accounting for rotation-induced apparent length variations caused by interferometer and photon calibrator beam centering offsets, absolute laser power measurement using temperature-controlled InGaAs photodetectors mounted on integrating spheres and calibrated by NIST, minimizing errors induced by localized elastic deformation of the mirror surface by using a two-beam configuration with the photon calibrator beams symmetrically displaced about the center of the optic, and simultaneously actuating the test mass with voice coil actuators and the photon calibrator to minimize fluctuations caused by the changing interferometer response. The photon calibrator is able to operate in the most sensitive interferometer configuration, and is expected to become a primary calibration method for future gravitational wave searches.Comment: 13 pages, 6 figures, accepted by Classical and Quantum Gravit

Precise calibration of LIGO test mass actuators using photon radiation pressure

Precise calibration of kilometer-scale interferometric gravitational wave detectors is crucial for source localization and waveform reconstruction. A technique that uses the radiation pressure of a power-modulated auxiliary laser to induce calibrated displacements of one of the ~10 kg arm cavity mirrors, a so-called photon calibrator, has been demonstrated previously and has recently been implemented on the LIGO detectors. In this article, we discuss the inherent precision and accuracy of the LIGO photon calibrators and several improvements that have been developed to reduce the estimated voice coil actuator calibration uncertainties to less than 2 percent (1-sigma). These improvements include accounting for rotation-induced apparent length variations caused by interferometer and photon calibrator beam centering offsets, absolute laser power measurement using temperature-controlled InGaAs photodetectors mounted on integrating spheres and calibrated by NIST, minimizing errors induced by localized elastic deformation of the mirror surface by using a two-beam configuration with the photon calibrator beams symmetrically displaced about the center of the optic, and simultaneously actuating the test mass with voice coil actuators and the photon calibrator to minimize fluctuations caused by the changing interferometer response. The photon calibrator is able to operate in the most sensitive interferometer configuration, and is expected to become a primary calibration method for future gravitational wave searches.Comment: 13 pages, 6 figures, accepted by Classical and Quantum Gravit

Kaon physics with a high-intensity proton driver

We study opportunities for future high-precision experiments in kaon physics using a high-intensity proton driver, which could be part of the front-end of a muon storage ring complex. We discuss in particular the rare decays $K_L\to\pi^0\nu\bar\nu$, $K^+\to\pi^+\nu\bar\nu$, $K_L\to\pi^0e^+e^-$, and lepton-flavour violating modes such as $K_L\to\mu e$ and $K\to\pi\mu e$. The outstanding physics potential and long-term interest of these modes is emphasized. We review status and prospects of current and planned experiments for the processes under consideration, and indicate possible improvements and strategies towards achieving the necessary higher sensitivity. Finally, we outline the machine requirements needed to perform these high-precision kaon experiments in the context of a muon storage ring facility.Comment: 26 pages, 12 figures; report of the kaon physics working group for the ECFA studies on neutrino factory and muon storage rings at CERN, G. Buchalla (convener); references update