118269320
The Role of Mass Asymmetry and Shell Structure in the Evaporation Residues Production
The effects of the entrance channel and shell structure of reacting nuclei on the experimental evaporation residues have been studied by analysing the 40Ar+176Hf, 86Kr+130,136Xe, 124Sn+92Zr and 48Ca+174Yb reactions leading to the 216Th* and 222Th* compound nuclei. The measured excitation function of evaporation residues for the 124Sn+92Zr reaction was larger than that for the 86Kr+130Xe reaction. The experimental values of evaporation residues in the 86Kr+136Xe reaction were about 500 times larger than that in the 86Kr+130Xe reaction. These results are explained by the initial angular momentum dependence of the fusion excitation functions calculated in framework of the dinuclear system concept and by the differences in survival probabilities calculated in framework of advanced statistical model. The dependencies of the fission barrier and the \Gamma_n / \Gamma_f ratio on the angular momentum of the excited compound nucleus are taken into account.
13153867
Mass measurements of very neutron-deficient Mo and Tc isotopes and their impact on rp process nucleosynthesis.
The masses of ten proton-rich nuclides, including the N=Z+1 nuclides ⁸⁵Mo and ⁸⁷Tc, were measured with the Penning trap mass spectrometer SHIPTRAP. Compared to the Atomic Mass Evaluation 2003 a systematic shift of the mass surface by up to 1.6 MeV is observed causing significant abundance changes of the ashes of astrophysical x-ray bursts. Surprisingly low α separation energies for neutron-deficient Mo and Tc are found, making the formation of a ZrNb cycle in the rp process possible. Such a cycle would impose an upper temperature limit for the synthesis of elements beyond Nb in the rp process.
201093324
Proton Radioactivity
121183473
Observation of rotating nuclear molecules and determination of their lifetimes
Long-living rotating nuclear molecules (or “dinuclear systems”) have been observed at the velocity filter SHIP at GSI in reactions of 64Ni + 207Pb at Coulomb barrier energies. The rotation was directly revealed by the velocity spectra of deep inelastic target-like transfer products which are formed during the lifetime of the nuclear molecule and emitted after its breakup. The corresponding rotation angles were about 180 degree pointing to long nuclear interaction times or lifetimes of the system, respectively. We deduced the lifetimes from the lines in the velocity spectra originating from two different rotation angles. Further, the unambiguous correlation of a certain transfer product with its individual velocity spectrum allowed us to study the lifetimes as a function of the number of transferred protons.
119438146
The discovery of the heaviest elements
16408480
Effective Kaon energy from a novel chiral SU(3) model
Abstract A new chiral SU(3) Lagrangian is proposed to describe the properties of kaons and anti-kaons in the nuclear medium, The saturation properties of nuclear matter are reproduced as well as the results of the Dirac-Briickner theory, After introducing the coupling between the omega meson and the kaon, our results for effective kaon and anti-kaon energy are quite similar as calculated in the one-boson-exchange model.
33743720
Small-scale structure of cold dark matter
Abstract We investigate the clumping of cold dark matter (CDM) at small scales. If the CDM particle is the neutralino, we find that collisional damping during its kinetic decoupling from the radiation fluid and free streaming introduce a small-scale cut-off in the primordial power spectrum of CDM. This cut-off sets the scale for the very first CDM objects in the Universe, which we expect to have a mass of ∼10 −12 M ⊙ . For non-thermal CDM candidates, such as axions, wimpzillas, or primordial black holes, the cosmological QCD transition might induce features in the primordial spectrum at similar mass scales.
119090594
Lorentz-invariant ensembles of vector backgrounds
We consider gauge field theories in the presence of ensembles of vector backgrounds. While Lorentz invariance is explicitly broken in the presence of any single background, here, the Lorentz invariance of the theory is restored by averaging over a Lorentz-invariant ensemble of backgrounds, i.e., a set of background vectors that is mapped onto itself under Lorentz transformations. This framework is used to study the effects of a non-trivial but Lorentz-invariant vacuum structure or mass dimension two vector condensates by identifying the background with a shift of the gauge field. Up to now, the ensembles used in the literature comprise configurations corresponding to non-zero field tensors together with such with vanishing field strength. We find that even when constraining the ensembles to pure gauge configurations, the usual high-energy degrees of freedom are removed from the spectrum of asymptotic states in the presence of said backgrounds in Euclidean and in Minkowski space. We establish this result not only for the propagators to all orders in the background and otherwise at tree level but for the full propagator.
119280123
Brane Induced Gravity: From a No-Go to a No-Ghost Theorem
Numerous claims in the literature suggest that gravity induced on a higher co-dimensional surface violates unitarity in the weak coupling regime. However, it remained unclear, why a conserved source localized on this surface and giving rise to an induced gravity term at low energies would absorb and emit the associated ghost, given a consistent source-free theory. In this article it is shown that the appearance of the induced Einstein Hilbert term does not threaten the unitarity of the theory. The physics arguments behind this statement are presented in a semi-covariant language, but the detailed proof is given using Dirac's constraint analysis. It is shown that the would-be ghost highlighted in previous works is non-dynamical and therefore not associated with a state in the Hilbert space. As a result of these investigations, brane induced gravity goes without a ghost, opening an exciting window of opportunity for consistent deformations of gravity at the largest observable distances.
37247936
Degravitation of the cosmological constant and graviton width
We study the possibility of decoupling gravity from the vacuum energy. This is effectively equivalent to promoting Newton's constant to a high-pass filter that degravitates sources of characteristic wavelength larger than a certain macroscopic (super) horizon scale L. We study the underlying physics and the consistency of this phenomenon. In particular, the absence of ghosts, already at the linear level, implies that in any such theory the graviton should either have a mass 1/L, or be a resonance of similar width. This has profound physical implications for the degravitation idea.
17693958
Discrete energy spectrum of Hawking radiation from Schwarzschild surfaces
We analyze the allowed energy levels of Hawking radiation from Schwarzschild surfaces in space-times with large extra dimensions. From the requirement that the wave functions associated with these particles be single-valued and obey radial boundary conditions, we derive an upper bound of their discrete energy spectrum as a function of the number of large extra dimensions and the mass of the black hole. Furthermore, we investigate the spacing of the energy levels.