Efficient Graph-based Genetic Programming Representation with Multiple Outputs

In this work, we explore and study the implication of having more than one output on a genetic programming （GP） graph-representation. This approach, called multiple interactive outputs in a single tree （MIOST）, is based on two ideas. First, we defined an approach, called interactivity within an individual （IWI）, which is based on a graph-GP representation. Second, we add to the individuals created with the IWI approach multiple outputs in their structures and as a result of this, we have MIOST. As a first step, we analyze the effects of IWI by using only mutations and analyze its implications （i.e., presence of neutrality）. Then, we continue testing the effectiveness of IWI by allowing mutations and the standard GP crossover in the evolutionary process. Finally, we tested the effectiveness of MIOST by using mutations and crossover and conducted extensive empirical results on different evolvable problems of different complexity taken from the literature. The results reported in this paper indicate that the proposed approach has a better overall performance in terms of consistency reaching feasible solutions.

Reduced spin-down rate of PSR J0738–4042 explained as due to an asteroid disruption event

Long term observations by Brook et al. reveal that the derivative of rotational frequency of PSR J0738-4042 changed abruptly in 2005. Originally, the spin-down rate was relatively stable, with the rotational frequency derivative being - 1.14 x 10-14 s-2. After September 2005, the derivative began to rise. About 1000 days later, it arrived at another relatively stable value of about -0.98 x 10-24 s-2, indicating that the pulsar is spinning-down relatively slowly. To explain the observed change in spin-down rate, we resort to an asteroid disrupted by PSR J0738-4042. In our model, the orbital angular momentum of the asteroid is assumed to be parallel to that of the rotating pulsar, so that the pronounced reduction in the spin-down rate can be naturally explained as due to the transfer of angular momentum from the disrupted material to the central pulsar. The derived magnetospheric radius is about 7.0 x 109 cm, which is smaller than the tidal disruption radius （8.7 x 10^10cm）. Our model is self-consistent. It is shown that the variability in the spin-down rate of PSR J0738-4042 can be quantitatively accounted for by accretion from the asteroid disrupted by the central pulsar.

Kinematic properties of the dual AGN system J0038+4128 based on long-slit spectroscopy

The study ofkiloparsec-scale dual active galactic nuclei （AGN） provides important clues for understanding the co-evolution between host galaxies and their central supermassive black holes undergoing a merging process. We present long-slit spectroscopy of J0038 ＋4128, a kiloparsec-scale dual AGN candidate, discovered recently by Huang et al., using the Yunnan Faint Object Spectrograph and Camera （YFOSC） mounted on the Lijiang 2.4-m telescope administered by Yunnan Observatories. From the long-slit spectra, we find that the average relative line-of-sight （LOS） velocity between the two nuclei （J0038＋4128N and J0038＋4128S） is about 150 km s-1. The LOS velocities of the emission lines from the gas ionized by the nuclei activities and of the absorption lines from stars governed by the host galaxies for different regions of J0038＋4128 exhibit the same trend. The same trend in velocities indicates that the gaseous disks are co-rotating with the stellar disks in this ongoing merging system. We also find several knots/giant H II regions scattered around the two nuclei with strong star formation revealed by the observed line ratios from the spectra. Those regions are also clearly detected in images from HST F336W/U-band and HST F555W/V-band.