Asymptotically correct shell model for nuclear fission

A two-center shell model with oscillator potentials, l→·s→ forces, and l→2 terms is developed. The shell structures of the original spherical nucleus and those of the final fragments are reproduced. For small separation of the two centers the level structure resembles the Nilsson scheme. This two-center shell model might be of importance in problems of nuclear fission

Collective correlations in C12

The strong coupling of the giant resonance to the surface vibrations in C12 results in the splitting of the single one-particle, one-hole, 1- collective state into several components, thus improving the agreement between theory and experiment to a very large extent

Collective correlations in spherical nuclei and the structure of giant resonances

The theory of collective correlations in nuclei is formulated for giant resonances interacting with surface vibrations. The giant dipole states are treated in the particle-hole framework, while the surface vibrations are described by the collective model. Consequently, this treatment of nuclear structure goes beyond both the common particle-hole model (including its various improvements which take ground-state correlations into account) and the pure collective model. The interaction between giant resonances and surface degrees of freedom as known from the dynamic collective theory is formulated in the particle-hole language. Therefore, the theory contains the particle-hole structures and the most important "collective intermediate" structures of giant resonances. Detailed calculations are performed for 12C, 28Si, and 60Ni. A good detailed agreement between theory and experiment is obtained for all these nuclei, although only 60Ni is in the region where one would expect the theory to work well (50< A <110)

Variable masses in fission and heavy-ion collisions

With the use of the cranking formula, the coordinate-dependent mass parameters of the kinetic-energy operator in fission processes and heavy-ion collisions are calculated in the two-center oscillator model. It is shown that the reduced mass and also the classical moment of inertia are obtained for large separations of the fragments. For small separations, however, the mass parameter for the motion of the centers of mass of the fragments is larger than the reduced mass by an order of magnitude

Quantum Electrodynamics near a Dielectric Half-space

We determine the photon propagator in the presence of a non-dispersive dielectric half-space and use it to calculate the self-energy of an electron near a dielectric surface

New high-z BL Lacs using the photometric method with Swift and SARA

BL Lacertae (BL Lac) objects are the prominent members of the third {\it Fermi} Large Area Telescope catalog of $\gamma$-ray sources. Half of the BL Lac population ($\sim$ 300) lack redshift measurements, which is due to the absence of lines in their optical spectrum, thereby making it difficult to utilize spectroscopic methods. Our photometric drop-out technique can be used to establish the redshift for a fraction of these sources. This work employed 6 filters mounted on the $Swift$-UVOT and 4 optical filters on two telescopes, the 0.65 m SARA-CTIO in Chile and 1.0 m SARA-ORM in the Canary Islands, Spain. A sample of 15 sources was extracted from the $Swift$ archival data for which 6 filter UVOT observations were conducted. By complementing the {\it Swift} observations with the SARA ones, we were able to discover two high redshift sources: 3FGL J1155.4-3417 and 3FGL J1156.7-2250 at $z=1.83^{+0.10}_{-0.13}$ and $z=1.73^{+0.11}_{-0.19}$ , respectively, resulting from the dropouts in the powerlaw template fits to these data. The discoveries add to the important (26 total) sample of high-redshift BL Lacs. While the sample of high-z BL Lacs is still rather small, these objects do not seem to fit well within known schemes of the blazar population and represent the best probes of the extragalactic background light.Comment: 10 pages, 6 figures (accepted by ApJ

Search for GRB X-ray Afterglows in the ROSAT All-sky Survey

We report on the status of our search for X-ray afterglows of gamma-ray burts (GRBs) using ROSAT all-sky survey (RASS) date. The number of potential X-ray afterglow candidates with respect to the expected number of bearmed GRBs allows to constrain the relative beaming angles of GRB emission and afterglow emission at about 1-5 hrs after the GRB