From quantum affine groups to the exact dynamical correlation function of the Heisenberg model

The exact form factors of the Heisenberg models $XXX$ and $XXZ$ have been recently computed through the quantum affine symmetry of $XXZ$ model in the thermodynamic limit. We use them to derive an exact formula for the contribution of two spinons to the dynamical correlation function of $XXX$ model at zero temperature.Comment: 5 pages, Latex, Presented at the Symposium ``Exactly soluble models in statistical mechanics: historical perspectives and current status" March 30-31, 1996, Northeastern University, Bosto

Extracting W Boson Couplings from the e+e−e^{+}e^{-} Production of Four Leptons

We consider the processes $e^{+}e^{-}\rightarrow \ell^{+} \ell^{\prime -}\nu \bar{\nu}^{\prime}$, including all possible charged lepton combinations, with regard to measuring parameters characterizing the $W$ boson. We calculate at what level these processes can be used to measure anamolous triple-boson vertice coupling parameters for the cases of $e^{+}e^{-}$ colliders at 500 $GeV$ and 1 $TeV$ center of mass energies.Comment: 13 pages,OCIP/C-93-

Spin-Correlation Coefficients and Phase-Shift Analysis for p+3^3He Elastic Scattering

Angular Distributions for the target spin-dependent observables A$_{0y}$, A$_{xx}$, and A$_{yy}$ have been measured using polarized proton beams at several energies between 2 and 6 MeV and a spin-exchange optical pumping polarized $^3$He target. These measurements have been included in a global phase-shift analysis following that of George and Knutson, who reported two best-fit phase-shift solutions to the previous global p+$^3$He elastic scattering database below 12 MeV. These new measurements, along with measurements of cross-section and beam-analyzing power made over a similar energy range by Fisher \textit{et al.}, allowed a single, unique solution to be obtained. The new measurements and phase-shifts are compared with theoretical calculations using realistic nucleon-nucleon potential models.Comment: Submitted to Phys. Rev.

Attenuation of photosynthetically active radiation and ultraviolet light in response to changing dissolved organic carbon in browning lakes : modelling and parametrization

We present and evaluate an update to the process-based lake model MyLake that includes a time-varying linkage between light attenuation of both photosynthetically active radiation (PAR) and ultraviolet (UV) radiation wavelengths to changes in dissolved organic carbon (DOC). In many parts of northeastern North America and Europe, DOC in lakes has rapidly increased, leading to reduced water transparency and increases in light attenuation. These changes alter the vertical light and heat distribution that affect vertical structuring of temperature and dissolved oxygen. We use this model update to test the responsiveness of PAR and UV attenuation to short-term fluctuations in DOC and with a test case of long-term browning at Lake Giles (Pennsylvania). Lake Giles has browned significantly since the late 1980s, and three decades of detailed empirical data have indicated more than a doubling of DOC concentrations, and consequent increases in PAR and UV attenuation, warming surface waters, cooling deep waters, and increasing deepwater oxygen depletion. We found that the model performance improved by 16% and 52% for long-term trends in PAR and UV attenuation, respectively, when these coefficients respond directly to in-lake DOC concentrations. Further, long-term trends in surface water warming, deepwater cooling, and deepwater oxygen depletion in Lake Giles were better captured by the model following this update, and were very rapid due to its high water transparency and low DOC. Hence, incorporating a responsive link between DOC and light attenuation in lake models is key to understanding long-term lake browning patterns, mechanisms, and ecological consequences

The Measurement of Tri-Linear Gauge Boson Couplings at e+e−e^+e^- Colliders

We describe a detailed study of the process $e^+e^- \to \ell\nu_\ell q \bar{q}$ and the measurement of tri-linear gauge boson couplings (TGV's) at LEP200 and at a 500~GeV and 1~TeV NLC. We included all tree level Feynman diagrams contributing to the four-fermion final states including gauge boson widths and non-resonance contributions. We employed a maximum likelihood analysis of a five dimensional differential cross section of angular distributions. This approach appears to offer an optimal strategy for measurement of TGV's. LEP200 will improve existing measurements of TGV's but not enough to see loop contributions of new physics. Measurements at the NLC will be roughly 2 orders of magnitude more precise which would probe the effects of new physics at the loop level.Comment: Latex file uses aipbook.sty with revtex and psfig.sty. 2 figures (uuencoded) will be added with figures command. Full postcript version with embedded figures is available at ftp://ftp.physics.carleton.ca/pub/theory/godfrey/ocipc9504.ps To appear in the Proceedings of the International Symposium on Vector Boson Self-Interactions, UCLA, Feb. 1-3, 199

Adjustment of speaker’s referential expressions to an addressee’s likely knowledge and link with theory of mind abilities

To communicate cooperatively, speakers must determine what constitutes the common ground with their addressee and adapt their referential choices accordingly. Assessing another person’s knowledge requires a social cognition ability termed theory of mind (ToM). This study relies on a novel referential communication task requiring probabilistic inferences of the knowledge already held by an addressee prior to the study. Forty participants were asked to present 10 movie characters and the addressee, who had the same characters in a random order, was asked to place them in order. ToM and other aspects of social cognition were also assessed. Participants used more information when presenting likely unknown than likely known movie characters. They particularly increased their use of physical descriptors, which most often accompanied movie-related information. Interestingly, a significant relationship emerged between our ToM test and the increased amount of information given for the likely unknown characters. These results suggest that speakers use ToM to infer their addressee’s likely knowledge and accordingly adapt their referential expressions

Globular Clusters in the dE,N galaxy NGC 3115 DW1: New Insights from Spectroscopy and HST Photometry

The properties of globular clusters in dwarf galaxies are key to understanding the formation of globular cluster systems, and in particular in verifying scenarios in which globular cluster systems of larger galaxies formed (at least partly) from the accretion of dwarf galaxies. Here, we revisit the globular cluster system of the dE,N galaxy NGC 3115 DW1 - a companion of the nearby S0 galaxy NGC 3115 - adding Keck/LRIS spectroscopy and HST/WFPC2 imaging to previous ground-based photometry. Spectra for seven globular clusters reveal normal abundance ratios with respect to the Milky Way and M31 clusters, as well as a relatively high mean metallicity ([Fe/H] = -1.0+/-0.1 dex). Crude kinematics indicate a high velocity dispersion within 10 kpc which could either be caused by dark matter dominated outer regions, or by the stripping of outer globular clusters by the nearby giant galaxy NGC 3115. The total galaxy mass out to 3 and 10 kpc lies between 10^10 and 10^11 solar masses and 2*10^10 and 4*10^11 solar masses, respectively, depending on the mass estimator used and the assumptions on cluster orbits and systemic velocity. The HST imaging allows measurement of sizes for two clusters, returning core radii around 2.0 pc, similar to the sizes observed in other galaxies. Spectroscopy allows an estimate of the degree of contamination by foreground stars or background galaxies for the previous ground-based photometry, but does not require a revision of previous results: NGC 3115 DW1 hosts around 60+/-20 clusters which corresponds to a specific frequency of 4.9+/-1.9, on the high end for massive dEs. Given its absolute magnitude (M_V=-17.7 mag) and the properties of its cluster system, NGC 3115 DW1 appears to be a transition between a luminous dE and low-luminosity E galaxy.Comment: 25 pages, 8 figures, accepted for publication in The Astronomical Journal, August 2000 issu