39970498
Difficulty of detecting minihalos via gamma rays from dark matter annihilation.
Analytical calculations and recent numerical experiments have shown that a sizable amount of the mass of our Galaxy is in a form of clumpy, virialized substructures that, according to Diemand et al., can be as light as 10(-6)M(.). In this work we estimate the gamma-ray flux expected from dark matter annihilation occurring within these minihalos, under the hypothesis that the bulk of dark matter is composed by neutralinos. We generate mock sky maps showing the angular distribution of the expected gamma-ray signal. We compare them with the sensitivities of satellite-borne experiments such as GLAST and find that a possible detection of minihalos is indeed very challenging.
118464550
Self-protection of massive cosmological gravitons
Relevant deformations of gravity present an exciting window of opportunity to probe the rigidity of gravity on cosmological scales. For a single-graviton theory, the leading relevant deformation constitutes a graviton mass term. In this paper, we investigate the classical and quantum stability of massive cosmological gravitons on generic Friedman backgrounds. For a Universe expanding towards a de Sitter epoch, we find that massive cosmological gravitons are self-protected against unitarity violations by a strong coupling phenomenon.
1452681
FORMATION OF SMALL-SCALE STRUCTURE IN SUSY CDM
The lightest supersymmetric particle, most likely the lightest neutralino, is one of the most prominent particle candidates for cold dark matter (CDM). We show that the primordial spectrum of density fluctuations in neutralino CDM has a sharp cut-off, induced by two different damping mechanisms. During the kinetic decoupling of neutralinos, non-equilibrium processes constitute viscosity effects, which damp or even absorb density perturbations in CDM. After the last scattering of neutralinos, free streaming induces neutralino flows from overdense to underdense regions of space. Both damping mechanisms together define a minimal mass scale for perturbations in neutralino CDM, before the inhomogeneities enter the nonlinear epoch of structure formation. We find that the very first gravitationally bound neutralino clouds ought to have masses above 10 −6 M⊙, which is six orders of magnitude above the mass of possible axion miniclusters.
119225428
Cascading gravity and degravitation
We construct a cascading brane model of gravity in which the behavior of the gravitational force law interpolates from (n+4)-dimensional to (n+3)-dimensional all the way down to 4-dimensional from longer to shorter length scales. We show that, at the linearized level, this model exhibits the features necessary for degravitation of the cosmological constant. The model is shown to be ghost free with the addition of suitable brane kinetic operators, and we demonstrate this using a number of independent procedures. Consequently this is a consistent infrared (IR) modification of gravity, providing a promising framework for a dynamical, degravitating solution of the cosmological constant problem.
29630378
Cosmological classicalization: maintaining unitarity under relevant deformations of the Einstein-Hilbert action.
Generic relevant deformations of Einstein's gravity theory contain additional degrees of freedom that have a multifaceted stabilization dynamics on curved spacetimes. We show that these relevant degrees of freedom are self-protected against unitarity violations by the formation of classical field lumps that eventually merge to a new background geometry. The transition is heralded by the massive decay of the original vacuum and evolves through a strong coupling regime. This process fits in the recently proposed classicalization mechanism and extends it further to free field dynamics on curved backgrounds.
209999169
Black Hole Production in Large Extra Dimensions at the Tevatron: New Limit on the Fundamental Scale of Gravity
120335892
Study of SHE at the GSI-SHIP
Abstract An overview of present experimental investigation of superheavy elements is given. Using cold fusion reactions which are based on lead and bismuth targets, relatively neutron deficient isotopes of the elements from 107 to 113 were synthesized at GSI in Darmstadt, Germany, and/or at RIKEN in Wako, Japan. In hot fusion reactions of 48 Ca projectiles with actinide targets more neutron rich isotopes of the elements from 112 to 116 and even 118 were produced at FLNR in Dubna, Russia. Recently, part of these data, which represent the first identification of nuclei located on the predicted island of SHEs, were confirmed in two independent experiments. The data are compared with theoretical descriptions.
43354809
Kaon effective mass and energy from a novel chiral SU(3)-symmetric Lagrangian
A new chiral SU(3) Lagrangian is proposed to describe the properties of kaons and antikaons in the nuclear medium, the ground state of dense matter, and the kaon-nuclear interactions consistently. The saturation properties of nuclear matter are reproduced as well as the results of Dirac-Br\"uckner theory. Our numerical results show that the kaon effective mass might be changed only moderately in the nuclear medium due to highly nonlinear density effects. After taking into account the coupling between the omega meson and the kaon, we obtain similar results for the effective kaon and antikaon energies as calculated in the one-boson-exchange model while in our model the parameters of the kaon-nuclear interactions are constrained by the SU(3) chiral symmetry.
124901090
Evidence for hindrance in fusion between sulfur and lead nuclei
The influence of the structure of projectile and target nuclei on the capture cross sections was investigated for the reactions ${}^{34}\mathrm{S}\phantom{\rule{0.16em}{0ex}}+{\phantom{\rule{0.16em}{0ex}}}^{204,206,208}$Pb and ${}^{36}\mathrm{S}\phantom{\rule{0.16em}{0ex}}+{\phantom{\rule{0.16em}{0ex}}}^{204,206,208}$Pb. Capture cross sections were deduced by measuring the fission fragments using multiwire proportional counters. An enhancement of the capture cross sections relative to a one-dimensional barrier penetration model was observed for all reactions at energies below the interaction barriers. The enhancement is larger in the case of reactions with ${}^{34}$S than with ${}^{36}$S. This observation is explained by a stronger coupling to the vibrational states in the reactions with ${}^{34}$S. Comparing the capture cross sections and the evaporation-residue cross sections for the reactions ${}^{36}\mathrm{S}\phantom{\rule{0.16em}{0ex}}+{\phantom{\rule{0.16em}{0ex}}}^{206}$Pb and ${}^{34}\mathrm{S}\phantom{\rule{0.16em}{0ex}}+{\phantom{\rule{0.16em}{0ex}}}^{208}$Pb, both yielding the same compound nucleus ${}^{242}$Cf, it is shown that the latter reaction has a lower fusion probability.
123438213
Large size foil-microchannel plate timing detectors
Abstract A large area foil-microchannel plate time-of-flight (TOF) system is presented. The parameters of the system are as follows: 55 cm 2 active area, 99.8% detection efficiency, 100% transparency and 700 ps time resolution. The TOF system, unique in size and conditions of exploitation, consists of two (or three) detectors used also as anticoincidence units for the analysing multistrip Si-detector array.
120695709
Strong influence of the entrance channel on the formation of compound nuclei Th216,222* and their evaporation residues
The dynamical effects of the entrance channel on the formation of the evaporation residues are studied by analyzing the $^{40}\mathrm{Ar}+^{176}\mathrm{Hf}$, $^{86}\mathrm{Kr}+^{130,136}\mathrm{Xe}$, $^{124}\mathrm{Sn}+^{92}\mathrm{Zr}$, and $^{48}\mathrm{Ca}+^{174}\mathrm{Yb}$ reactions leading to the $^{216}\mathrm{Th}{}^{*}$ and $^{222}\mathrm{Th}{}^{*}$ compound nuclei. We find that the difference between the evaporation residue cross sections for the reactions leading to the same compound nucleus is caused by the different angular momentum distributions of the partial fusion cross sections ${\ensuremath{\sigma}}_{\mathrm{fus}}^{\ensuremath{\ell}}({E}_{c.m.})$. The strong dependence of the fusion angular momentum distribution on the mass (charge) asymmetry and shell structure of reactants is demonstrated. The effect of the $A/Z$ ratio for the $^{86}\mathrm{Kr}+^{130,136}\mathrm{Xe}$ reactions is discussed. The dynamical conditions of capture affect the competition between complete fusion and quasifission and, consequently, the shape of the angular momentum distribution of the compound nucleus. By this way the peculiarities of the entrance channel also affect the fission-evaporation competition of the excited intermediate nuclei along the deexcitation cascade of the compound nucleus and, consequently, the evaporation residue formation.