The Low Column Density Lyman-alpha Forest

We develop an analytical method based on the lognormal approximation to compute the column density distribution of the Lyman-alpha forest in the low column density limit. We compute the column density distributions for six different cosmological models and found that the standard, COBE-normalized CDM model cannot fit the observations of the Lyman-alpha forest at z=3. The amplitude of the fluctuations in that model has to be lowered by a factor of almost 3 to match observations. However, the currently viable cosmological models like the lightly tilted COBE-normalized CDM+Lambda model, the CHDM model with 20% neutrinos, and the low-amplitude Standard CDM model are all in agreement with observations, to within the accuracy of our approximation, for the value of the cosmological baryon density at or higher than the old Standard Bing Bang Nucleosynthesis value of 0.0125 for the currently favored value of the ionizing radiation intensity. With the low value for the baryon density inferred by Hogan & Rugers (1996), the models can only marginally match observations.Comment: three postscript figures included, submitted to ApJ

Split degenerate states and stable p+ip phases from holography

In this paper, we investigate the p+$i$p superfluid phases in the complex vector field holographic p-wave model. We find that in the probe limit, the p+$i$p phase and the p-wave phase are equally stable, hence the p and $i$p orders can be mixed with an arbitrary ratio to form more general p+$\lambda i$p phases, which are also equally stable with the p-wave and p+$i$p phases. As a result, the system possesses a degenerate thermal state in the superfluid region. We further study the case with considering the back reaction on the metric, and find that the degenerate ground states will be separated into p-wave and p+$i$p phases, and the p-wave phase is more stable. Finally, due to the different critical temperature of the zeroth order phase transitions from p-wave and p+$i$p phases to the normal phase, there is a temperature region where the p+$i$p phase exists but the p-wave phase doesn't. In this region we find the stable p+$i$p phase for the first time.Comment: 16 pages, 5 figures; typos correcte

Line versus Flux Statistics -- Considerations for the Low Redshift Lyman-alpha Forest

The flux/transmission power spectrum has become a popular statistical tool in studies of the high redshift ($z > 2$) Lyman-alpha forest. At low redshifts, where the forest has thinned out into a series of well-isolated absorption lines, the motivation for flux statistics is less obvious. Here, we study the relative merits of flux versus line correlations, and derive a simple condition under which one is favored over the other on purely statistical grounds. Systematic errors probably play an important role in this discussion, and they are outlined as well.Comment: 6 pages, to appear in "The IGM/Galaxy Connection: The Distribution of Baryons at z=0", eds. J. L. Rosenberg and M. E. Putma

Application of stratified emulsion splitting technology in highly hard nuclear cataract surgery

AIM:To explore safety and effectiveness of stratified emulsion splitting technology in highly hard nuclear cataract ultrasonic emulsification. METHODS: Totally 43 cases(47 eyes)of highly hard nuclear cataract was performed cataract extraction combined IOL implantation with stratified emulsion splitting cataract ultrasonic emulsification technology. RESULTS:Postoperative visual acuity 1 day, 1 week and 1 month best-corrected visual acuity ≥0.5 was accounted for 70.21%, 87.23% and 89.36%. Intraoperative capsule rupture was found in 2 eyes. Corneal mild edema was found in 7 eyes(14.89%)after the first l day post-operation. CONCLUSION:Stratified emulsion splitting technique has a practical application with little tissue damage, low capsular rupture rate and few complications for highly hard nuclear cataract patients and can bring a desirable outcome