Bounds on the Compactness of Neutron Stars from Brightness Oscillations

The discovery of high-amplitude brightness oscillations at the spin frequency or its first overtone in six neutron stars in low-mass X-ray binaries during type~1 X-ray bursts provides a powerful new way to constrain the compactness of these stars, and hence to constrain the equation of state of the dense matter in all neutron stars. Here we present the results of general relativistic calculations of the maximum fractional rms amplitudes that can be observed during bursts. In particular, we determine the dependence of the amplitude on the compactness of the star, the angular dependence of the emission from the surface, the rotational velocity at the stellar surface, and whether there are one or two emitting poles. We show that if two poles are emitting, as is strongly indicated by independent evidence in 4U 1636-536 and KS 1731-26, the resulting limits on the compactness of the star can be extremely restrictive. We also discuss the expected amplitudes of X-ray color oscillations and the observational signatures necessary to derive convincing constraints on neutron star compactness from the amplitudes of burst oscillations.Comment: 8 pages plus one figure, AASTeX v. 4.0, submitted to The Astrophysical Journal Letter

Information of Structures in Galaxy Distribution

We introduce an information-theoretic measure, the Renyi information, to describe the galaxy distribution in space. We discuss properties of the information measure, and demonstrate its relationship with the probability distribution function and multifractal descriptions. Using the First Look Survey galaxy samples observed by the Infrared Array Camera onboard Spitzer Space Telescope, we present measurements of the Renyi information, as well as the counts-in-cells distribution and multifractal properties of galaxies in mid-infrared wavelengths. Guided by multiplicative cascade simulation based on a binomial model, we verify our measurements, and discuss the spatial selection effects on measuring information of the spatial structures. We derive structure scan functions at scales where selection effects are small for the Spitzer samples. We discuss the results, and the potential of applying the Renyi information to measuring other spatial structures.Comment: 25 pages, 8 figures, submitted to ApJ; To appear in The Astrophysical Journal 2006, 644, 678 (June 20th

The Mass Operator in the Light-Cone Representation

I argue that for the case of fermions with nonzero bare mass there is a term in the matter density operator in the light-cone representation which has been omitted from previous calculations. The new term provides agreement with previous results in the equal-time representation for mass perturbation theory in the massive Schwinger model. For the DLCQ case the physics of the new term can be represented by an effective operator which acts in the DLCQ subspace, but the form of the term might be hard to guess and I do not know how to determine its coefficient from symmetry considerations.Comment: Revtex, 8 page

Globular Clusters and Dwarf Spheroidal Galaxies

Traditionally globular clusters and dwarf spheroidal galaxies have been distinguished by using one or more of the following criteria: (1) mass, (2) luminosity, (3) size, (4) mass-to-light ratio and (5) spread in metallicity. However, a few recently discovered objects show some overlap between the domains in parameter space that are occupied by galaxies and clusters. In the present note it is shown that ellipticity can, in some cases, be used to help distinguish between globular clusters and dwarf spheroidal galaxies.Comment: MNRAS (Letters), in pres

Nitrogen Trichloride with Benzalacetophenone

Nitrogen trichloride and benzalacetophenone in carbon tetrachloride solution between 20° and -15 ° react to form free nitrogen, ammonium chloride, benzalacetophenone dichloride, and a C-chloro-N -dichloroamino ketone. This compound can be reduced to the C-chloroamino ketone by means of concentrated hydrochloric acid. The hydrochloride and the benzoyl derivative of this compound were isolated and analyzed

No supercritical supercurvature mode conjecture in one-bubble open inflation

In the path integral approach to false vacuum decay with the effect of gravity, there is an unsolved problem, called the negative mode problem. We show that the appearance of a supercritical supercurvature mode in the one-bubble open inflation scenario is equivalent to the existence of a negative mode around the Euclidean bounce solution. Supercritical supercurvature modes are those whose mode functions diverge exponentially for large spatial radius on the time constant hypersurface of the open universe. Then we propose a conjecture that there should be ``no supercritical supercurvature mode''. For a class of models that contains a wide variety of tunneling potentials, this conjecture is shown to be correct.Comment: 11 pages, 3 postscript figures, tarred, gzipped. submitted to Phys. Rev. D1

Thermal continua of AGN accretion disks

We have computed the thermal continuum energy distribution of thermal radiation from the atmospheres of supermassive accretion disks around supermassive black holes. Non-LTE radiative transfer is combined with a model of the vertical structure at each radius appropriate to the low effective gravities of these disks. Locally, the Lyman edge of H can be in emission or absorption. When the emission is summed over the disk with Doppler and gravitational redshifts taken into account, the observed continuum typically shows little sign of a discontinuity near the Lyman edge. For relatively cool disks, the Lyman edge is in absorption, but it appears as a slope change extending over several hundred angstroms, rather than an abrupt discontinuity. Disks around Kerr black holes can explain the observed range of soft X-ray luminosities of AGN, but disks around Schwarzschild holes are much too faint in soft X-rays

Azoyl Derivatives of Sugars and Separation by Chromatographic Adsorption (Abstract)

Azobenzene-p-benzoyl derivatives of cl-cl-glucose and B-d-glucose, fructose, galactose, lactose, maltose, sucrose, trehalose, gentiobiose and cellobiose have been prepared. They have been analized for per cent of azoyl and their specific rotations in chloroform determined. The chromatographic separation of d-d-glucose and fructose azoates as described by Reich has been repeated using silicic acid as an adsorbent. Using a mixture of magnesol and dicalite as an adsorbent the following separations have also been made: lactose and galactose, sucrose and d-d-glucose, trehalose and B-d-glucose

Diphenylketene with Nitrogen Trichloride

Diphenylketene reacts with nitrogen trichloride in carbon tetrachloride solution. When this solution is warmed to 50° C with sodium hydroxide the addition product undergoes a rearrangement with the formation of imidobenzophenone. This rearrangement is similar to the rearrangement in Hofmann\u27s method for the preparation of primary amines from amides. On passing dry HCl into the carbon tetrachloride solution, the hydrochloride of this compound is precipitated

Some Reactions of Diphenyletyleneimine and Attempts to Prepare Aminoethenes

Ozone had no effect on diphenylethyleneimine. The benzoyl derivative was prepared in pyridine by the action of benzoyl chloride. In dilute sodium hydroxide the same reagent formed α-β-diphenyl-β-chloroethylamine. This compound was changed to benzoyl diphenylethyleneimine by heating with alcoholic sodium ethylate. On being heated to 225° diphenylethyleneimine rearranged to benzalbenzylamine. A number of experiments were tried in an attempt to prepare aminoethenes but the results were not conclusive