Narrow Results

The properties of N = 41 isotones are investigated systemically by using the nonlinear relativistic mean field theory. It is found that all the calculating binding energies with four different interactions are comparable for the ground and low-lying excited states, and very close to the data available. The calculations show that there exists a neutron halo in the first excited state in ⁶⁹Ni, as well as in the second excited state in ⁶⁹Ni. It is also predicted that there exists a neutron halo in the first excited state in ⁶⁵Cr, ⁶⁶Mn, ⁶⁷Fe and ⁶⁸Co.

t+t clustering in He isotopes is investigated by using two theoretical approaches. A role of the t+t cluster component in the ground state is examined with AMD triple-S, allowing the wider configuration space containing simultaneously the "t+t+valence neutrons" structure and "⁴He+valence neutrons" structure. We understand the importance of the t+t component even for the ground state. Further, t+t resonances are investigated with RGM type approach. We obtained many t+t states as resonances near to t+t threshold.

We have studied the role of spatial extension (Halo structure) of ⁶He and that of breakup reaction channel in the fusion of ⁶He+²³⁸U system. The breakup channel effects are taken into account within the framework of the dynamic polarisation potential approach. It has been found that the fusion cross section enhances due to the static effects of spatial extension of the projectile in the entire energy region. The breakup effects, however, results in the above barrier suppression and below barrier small enhancement in the fusion cross section. The matching between the data and the predictions improves significantly by the inclusion of both static and breakup effects.

Crystals were used at Fermilab accelerators for slow extraction and halo collimation in the Tevatron collider, and for channeling radiation generation experiments at the FAST electron linac facility. Here we overview past experience and major outcomes of these studies and discuss opportunities for new crystal acceleration R&D program.

An $R$-module $V$ over a semiring $R$ lacks zero sums (LZS) if $x+y=0$ implies $x=y=0$. More generally, a submodule $W$ of $V$ is “summand absorbing” (SA), if, for all $x,y\in V$, $x+y\in W\Rightarrow x\in W,y\in W.$ These relate to tropical algebra and modules over (additively) idempotent semirings, as well as modules over semirings of sums of squares. In previous work, we have explored the lattice of SA submodules of a given LZS module, especially, those that are finitely generated, in terms of the lattice-theoretic Krull dimension. In this paper, we consider which submodules are SA and describe their explicit generation.

Crystals were used at Fermilab accelerators for slow extraction and halo collimation in the Tevatron collider, and for channeling radiation generation experiments at the FAST electron linac facility. Here we overview past experience and major outcomes of these studies and discuss opportunities for new crystal acceleration R&D program.

Since the pioneering work of Tremaine&Gunn in 1979 to the present, many attempts have been presented to constrain the dark matter particle mass from the phase-space density evolution until the approximate point of virialization of dark matter halos. In particular, recent numerical simulations of the evolution of the phase-space density of dwarf spheroidal dark matter halos revealed a strong tension between the obtained particle mass bound and the lower limit of few keV from other astrophysical constraints. We propose a novel approach to calculate the phase-space density distribution in dwarf galaxies, to show that such a discrepancy disappear if the dark matter distribution possesses a core in which quantum statistical effects are important, as in the case of the dark matter profiles of keV fermions recently introduced by Ruffini, Argüelles and Rueda (2015).

The dimensionless entropy , , of the visible universe, taken as a sphere of radius 50 billion light years with the Earth at its "center", is discussed. An upper limit (10¹¹²), and a lower limit (10¹⁰²), for are introduced. It is suggested that intermediate-mass black holes (IMBHs) constitute all dark matter, and that they dominate .

Motivated by detections of hypervelocity stars that may originate from the Galactic Center, we revist the problem of a binary disruption by a passage near a much more massive point mass. The six order of magnitude mass ratio between the Galactic Center black hole and the binary stars allows us to formulate the problem in the restricted parabolic three-body approximation. In this framework, results can be simply rescaled in terms of binary masses, its initial separation and binary-to-black hole mass ratio. Consequently, an advantage over the full three-body calculation is that a much smaller set of simulations is needed to explore the relevant parameter space. Contrary to previous claims, we show that, upon binary disruption, the lighter star does not remain preferentially bound to the black hole. In fact, it is ejected exactly in 50% of the cases. Nonetheless, lighter objects have higher ejection velocities, since the energy distribution is independent of mass. Focusing on the planar case, we provide the probability distributions for disruption of circular binaries and for the ejection energy. We show that even binaries that penetrate deeply into the tidal sphere of the black hole are not doomed to disruption, but survive in 20% of the cases. Nor do these deep encounters produce the highest ejection energies, which are instead obtained for binaries arriving to 0:1 – 0:5 of the tidal radius in a prograde orbit. Interestingly, such deep-reaching binaries separate widely after penetrating the tidal radius, but always approach each other again on their way out from the black hole. Finally, our analytic method allows us to account for a finite size of the stars and recast the ejection energy in terms of a minimal possible separation. We find that, for a given minimal separation, the ejection energy is relatively insensitive to the initial binary separation (see Sari, Kobayashi and Rossi 2010, ApJ 708, 605 for the full discussion).

We show that exoplanets in the M31 galaxy may be detected with the pixel-lensing method by using telescopes making high cadence observations of an ongoing microlensing event. Although the mean mass for detectable exoplanets is about 2 M_J, even small mass exoplanets (M_P < 20 M_⊕) can cause significant deviations, which are observable with large telescopes. We reanalysed the POINT-AGAPE microlensing event PA-99-N2. First, we test the robustness of the binary lens conclusion for this light curve. Second, we show that for such long duration and bright microlensing events, the efficiency for finding planetary-like deviations is strongly enhanced.

Within the density-dependent relativistic Hartree-Fock-Bogoliubov (DDRHFB) theory, the structure properties of Carbon isotopes are systematically studied, by taking the finite-range Gogny D1S with prefix factor 1.1 as the pairing force. The self-consistent DDRHFB calculations indicate the single neutron halo structures in both ¹⁷C and ¹⁹C. It is also found that close to the neutron drip line there exists distinct odd-even staggering on neutron radii, which is tightly related with the block effect.