Time Evolution and the Nature of the Near-Infrared Jets in GRS1915+105

We observed the galactic microquasar GRS1915+105 in the K ($2.2 \mu$m) band on October 16 and 17, 1995 UTC using the COB infrared (IR) imager on the Kitt Peak National Observatory 2.1-m telescope with a 0.2-arcsec/pixel plate scale and under good ($\sim 0.7$-arcsec) seeing conditions. Using a neighboring star in the image frames to determine the point spread function (PSF), we PSF-subtract the images of GRS1915+105. We find no evidence of extended emission such as the apparent near-IR jets seen by Sams et al. (1996) in July, 1995. Simple modelling of the star + jet structure allows us to place an upper limit on any similar emission at that position of $K>16.4$ at the 95% confidence level, as compared to $K=13.9$ as seen by Sams et al. (1996). This lack of extended IR flux during continued hard X-ray flaring activity confirms the hypothesis that the extended IR emission arises from the superluminal radio-emitting jets rather than reprocessing of the X-ray emission on other structures around the compact central object. Given the large apparent velocity of the radio-emitting jets, by the time of our observations the Sams et al. feature would have moved $>1$ arcsec from GRS1915+105, and we can place a limit of $K>17.7$ (95% confidence level) on any infrared emission in this region. We can thus place an upper limit on the radiative timescale of the feature of $\tau < 25$ days, which is consistent with synchrotron jet emission.Comment: 10 pages, 3 figures; submitted to ApJ Letter

Recalibrating valence weighting biases to promote changes in rejection sensitivity and risk-taking

Past research has found that modifying individuals' valence weighting tendencies by recalibrating them to weight positive and negative valence in a more balanced manner influenced a variety of judgments. The current research examines the utility of the recalibration procedure as a targeted intervention. In Experiment 1, we recruited participants high in rejection sensitivity (who are known to exhibit a negative weighting bias) and in Experiment 2, we recruited participants with high risk tendencies (who are known to exhibit a positive weighting bias). In both experiments, participants first played BeanFest, in which they were presented with beans varying in shape and speckles and learned which increased or decreased points. They later classified the game beans, as well as novel ones varying in their resemblance to the known positives or known negatives, as good or bad. In the recalibration condition, participants were told if they classified each bean correctly, thus receiving feedback regarding the appropriate weighting of resemblance to a known positive versus a negative. The controls, who received no feedback, were less accurate at classifying the novel the beans than the recalibration participants. Furthermore, in Experiment 1, the recalibration condition subsequently exhibited lower sensitivity to rejection than the control condition, with this reduction being stronger for individuals initially higher in rejection sensitivity. This effect was still present a week later. In Experiment 2, the recalibration condition reported diminished risk-tendencies, again with this effect being stronger for individuals with initially higher riskiness, and persisting for a week. Even more importantly, recalibration participants also engaged in less risky behavior on a laboratory task

Puzzles in charm spectroscopy

We briefly analyze aspects of open and hidden charm resonances, discussing in particular the mesons $D_{sJ}(2860)$ and X(3872).Comment: 8 pages, 4 figures. Invited talk given at the YKIS Seminar on New Frontiers in QCD: Exotic Hadrons and Hadronic Matter, Kyoto, Japan, 20 Nov. - 8 Dec. 200

Sensitive methods for estimating the anchoring strength of nematic liquid crystals on Langmuir-Blodgett monolayers of fatty acids

The anchoring of the nematic liquid crystal N-(p-methoxybenzylidene)-p-butylaniline (MBBA) on Langmuir-Blodgett monolayers of fatty acids (COOHC$_{n}$H$_{2n+1}$) was studied as a function of the length of the fatty acid alkyl chains, $n$ ($n = 15, 17, 19, 21$). The monolayers were deposited onto ITO-coated glass plates which were used to assemble sandwich cells of various thickness that were filled with MBBA in the nematic phase. The mechanism of relaxation from the flow-induced quasi-planar to the surface-induced homeotropic alignment was studied for the four decreases linearly with increasing the length of the alkyl chains $n$ which suggests that the Langmuir-Blodgett film plays a role in the phenomenon. This fact was confirmed by a sensitive estimation of the anchoring strength of MBBA on the fatty acid monolayers after anchoring breaking which takes place at the transition between two electric-field--induced turbulent states, denoted as DSM1 and DSM2. It was found that the threshold electric field for the anchoring breaking, which can be considered as a measure of the anchoring strength, also decreases linearly as $n$ increases. Both methods thus possess a high sensitivity in resolving small differences in anchoring strength. In cells coated with mixed Langmuir-Blodgett monolayers of two fatty acids ($n=15$ and $n=17$) a maximum of the relaxation speed was observed when the two acids were present in equal amount. This observation homeotropic cells by changing the ratio between the components of the surfactant film.Comment: LaTeX article, 20 pages, 15 figures, 17 EPS files. 1 figure added, references moved. Submitted to Phys. Rev.

The Diagonal Ghost Equation Ward Identity for Yang-Mills Theories in the Maximal Abelian Gauge

A BRST perturbative analysis of SU(N) Yang-Mills theory in a class of maximal Abelian gauges is presented. We point out the existence of a new nonintegrated renormalizable Ward identity which allows to control the dependence of the theory from the diagonal ghosts. This identity, called the diagonal ghost equation, plays a crucial role for the stability of the model under radiative corrections implying, in particular, the vanishing of the anomalous dimension of the diagonal ghosts. Moreover, the Ward identity corresponding to the Abelian Cartan subgroup is easily derived from the diagonal ghost equation. Finally, a simple proof of the fact that the beta function of the gauge coupling can be obtained from the vacuum polarization tensor with diagonal gauge fields as external legs is given. A possible mechanism for the decoupling of the diagonal ghosts at low energy is also suggested.Comment: 1+17 pages, LaTeX2