Links for September 2015

Here’s to several decades of grinding out a couple of decimal places to parameterize a charged Higgs:

Three years ago the BaBar collaboration at SLAC measured the branching ratios for B-meson decay to produce either a muon or a tau. For two slightly different decays, they found 2σ or greater deviations from the democratic standard-model expectation. Now the LHCb collaboration at CERN has confirmed the BaBar result for one of the decays. In a preprint, the Belle group at KEK in Japan has also announced results that show a similar though less strong deviation from the standard model. The figure below (from the Heavy Flavor Averaging Group) shows the branching ratios (R) measured by the groups for the two decays, denoted D and D*, along with the standard-model prediction. Taken together, the groups’ measurements have struck a 3.9-σ blow to the principle of lepton democracy. If they hold up, the standard model will have to be modified—perhaps by the addition of a new charged Higgs boson, whose interactions would depend on mass.

Importantly, this is a combination of several experiments rather than easily attributable to a systematic mistake in one.

New data on great filter from density of habitable planets.

these new results offer little support for the scenario where we have a good chance of growing out into the universe and meeting other aliens before a billion of years have passed. Either we are very likely to die and not grow, or we are the only ones who could grow…The simplest story seems right: if we have a chance to fill the universe, we are the only ones for a billion light years with that chance.

Scientists’ concerns about open-access (OA) publishing might be fading, according to the results of a large Nature Publishing Group survey released on 13 August (see go.nature.com/t2cxrq). The poll found that more than one-third of scientists have not published any OA papers in the past three years, a proportion that has shifted little since 2014. But last year, 40% of those researchers expressed concerns about perceptions of the quality of OA publications; this year, that proportion dropped to 27%.

(H/t Sabine.)

The Sun is roughly typical star and emits about photon per second in the visible range. It takes about 100 photon incident on the pupil, of which only about 10 are absorbed by a rod cell, to lead to visual perception of a flash by humans. If we require those photons to hit our square-centimeter pupil in a tenth of a second, that means the dimmest stars would be visible from away. And indeed, almost all of the stars we see are within a 1,000-lightyear sphere around the sun, with the very furthest individually visible stars (much brighter than the sun) being 16,000 lightyears away. In comparison, the Milky Way disk is about 1,000 lightyears thick and 100,000 lightyears across, which is why it appears as a dim smear across the night sky with no individually distinguishable stars.

MIT researchers unveil the first fundamentally new approach to cache coherence in more than three decades. Whereas with existing techniques, the directory’s memory allotment increases in direct proportion to the number of cores, with the new approach, it increases according to the logarithm of the number of cores.

Harold Lee sees this happening in lots of places, and (very speculatively) speculates that it has to do with most of the prestigious career paths involving no positions of command, in contrast to the many military careers of the past. I don’t know exactly what economic considerations prevent grad student for having more subordinate undergrads, or young lawyers ordering around more interns. However, I do think this story is consistent with the impressive ambition of folks coming out of the few industries where smart young people can quickly become commanders: technology start-ups.

Greater Intrasex Phenotype Variability in Males Than in Females is a Fundamental Aspect of the Gender Differences in Humans

Human studies of intrasex variability have shown that males are intellectually more variable. Here we have performed retrospective statistical analysis of human intrasex variability in several different properties and performances that are unrelated or indirectly related to intelligence: (a) birth weights of nearly 48,000 babies (Medical Birth Registry of Norway); (b) adult weight, height, body mass index and blood parameters of more than 2,700 adults aged 18–90 (NORIP); (c) physical performance in the 60 meter dash event of 575 junior high school students; and (d) psychological performance reflected by the results of more than 222,000 undergraduate university examination grades (LIST). For all characteristics, the data were analyzed using cumulative distribution functions and the resultant intrasex variability for males was compared with that for females. The principal finding is that human intrasex variability is significantly higher in males, and consequently constitutes a fundamental sex difference.

A related comment by David Friedman points out that fact that the mean score on IQ-loaded tests is the same for men and women is not really a gauge-invariant fact. Women do consistently better than men on some question, and vice versa, so the relative means can be shifted by choosing how many questions of each type to have.