On some geometric features of the Kramer interior solution for a rotating perfect fluid

Geometric features (including convexity properties) of an exact interior gravitational field due to a self-gravitating axisymmetric body of perfect fluid in stationary, rigid rotation are studied. In spite of the seemingly non-Newtonian features of the bounding surface for some rotation rates, we show, by means of a detailed analysis of the three-dimensional spatial geodesics, that the standard Newtonian convexity properties do hold. A central role is played by a family of geodesics that are introduced here, and provide a generalization of the Newtonian straight lines parallel to the axis of rotation.Comment: LaTeX, 15 pages with 4 Poscript figures. To be published in Classical and Quantum Gravit

Current-voltage characteristics of quasi-one-dimensional superconductors: An S-curve in the constant voltage regime

Applying a constant voltage to superconducting nanowires we find that its IV-characteristic exhibits an unusual S-behavior. This behavior is the direct consequence of the dynamics of the superconducting condensate and of the existence of two different critical currents: j_{c2} at which the pure superconducting state becomes unstable and j_{c1}<j_{c2} at which the phase slip state is realized in the system.Comment: 4 pages, 5 figures, replaced with minor change

Information Content in B→VVB \to VV Decays and the Angular Moments Method

The time-dependent angular distributions of decays of neutral $B$ mesons into two vector mesons contain information about the lifetimes, mass differences, strong and weak phases, form factors, and CP violating quantities. A statistical analysis of the information content is performed by giving the ``information'' a quantitative meaning. It is shown that for some parameters of interest, the information content in time and angular measurements combined may be orders of magnitude more than the information from time measurements alone and hence the angular measurements are highly recommended. The method of angular moments is compared with the (maximum) likelihood method to find that it works almost as well in the region of interest for the one-angle distribution. For the complete three-angle distribution, an estimate of possible statistical errors expected on the observables of interest is obtained. It indicates that the three-angle distribution, unraveled by the method of angular moments, would be able to nail down many quantities of interest and will help in pointing unambiguously to new physics.Comment: LaTeX, 34 pages with 9 figure

A unified approach to linking experimental, statistical and computational analysis of spike train data

A fundamental issue in neuroscience is how to identify the multiple biophysical mechanisms through which neurons generate observed patterns of spiking activity. In previous work, we proposed a method for linking observed patterns of spiking activity to specific biophysical mechanisms based on a state space modeling framework and a sequential Monte Carlo, or particle filter, estimation algorithm. We have shown, in simulation, that this approach is able to identify a space of simple biophysical models that were consistent with observed spiking data (and included the model that generated the data), but have yet to demonstrate the application of the method to identify realistic currents from real spike train data. Here, we apply the particle filter to spiking data recorded from rat layer V cortical neurons, and correctly identify the dynamics of an slow, intrinsic current. The underlying intrinsic current is successfully identified in four distinct neurons, even though the cells exhibit two distinct classes of spiking activity: regular spiking and bursting. This approach – linking statistical, computational, and experimental neuroscience – provides an effective technique to constrain detailed biophysical models to specific mechanisms consistent with observed spike train data.Published versio

Why (and how) Superman hides behind glasses: the difficulties of face matching

As a mild-mannered reporter, Clark Kent is able to blend into human society without drawing much attention to himself. Although he utilises several methods of disguise (clothing, posture, hair style), perhaps his most famous is a simple pair of glasses (see Figure 1). We know that wearing glasses can make you look more educated and intelligent (e.g., Hellström & Tekle, 1994), but for Superman, the goal is primarily to hide his true identity. Of course, one of the cornerstones of enjoying superhero fiction is that we suspend our disbelief and try to ignore the obvious questions (for example, how useful or plausible is it that Squirrel Girl can communicate with and understand squirrels?!). However, the scientist inside us sometimes breaks through and we are given the opportunity to investigate. Here, we tackle the question that comic book fans have been asking for decades – could Superman really hide his identity using a pair of glasses

Sequential effects in facial attractiveness judgments using cross-classified models: Investigating perceptual and response biases.

When evaluating items in a sequence, the current judgment is influenced by the previous item and decision. These sequential biases take the form of assimilation (shifting toward the previous item/decision) or contrast (shifting away). Previous research investigating facial attractiveness evaluations provides mixed results while using analytical techniques that fail to address the dependencies in the data or acknowledge that the images represent only a subset of the population. Here, we utilized cross-classified linear mixed-effects modeling across 5 experiments. We found compelling evidence of multicollinearity in our models, which may explain apparent contradictions in the literature. Our results demonstrated that the previous image’s rating positively influenced current ratings, and this was also the case for the previous image’s baseline value, although only when that image remained onscreen during the current trial. Further, we found no influence of the next face on current judgments when this was visible. In our final experiment, the response bias due to the previous trial remained present even when accounts involving motor effort were addressed. Taken together, these findings provide a clear framework in which to incorporate current and past results regarding the biases apparent in sequential judgments, along with an appropriate method for investigating these biases

Wanting or having children predicts age preferences in online dating

When dating, women seek men slightly older than themselves while men typically prefer younger women. Such patterns reflect differences in parental investment and age-related fertility, which are both concerned with maximizing reproductive outcomes. Using large samples of online daters, we considered whether having or wanting children was associated with the perceived importance of age as a matching criterion when dating (Study 1; N = 119,361), as well as how these two factors related to the preferred age of a match (Study 2; N = 486,382). Men without children (or those who wanted children) rated age as more important than those with children (or those who did not want children), and also selected a preferred age range that incorporated younger women. In contrast, women’s preferences showed little association with having or wanting children. Taken together, these findings demonstrate that age preferences may depend on factors in addition to those previously investigated, and that the relationships with the number of current children and the desire to have children are consistent with evolutionary predictions