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.
37255447
A Quantum Bound-State Description of Black Holes
A relativistic framework for the description of bound states consisting of a large number of quantum constituents is presented, and applied to black-hole interiors. At the parton level, the constituent distribution, number and energy density inside black holes are calculated, and gauge corrections are discussed. A simple scaling relation between the black hole mass and constituent number is established.
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.
209999169
Black Hole Production in Large Extra Dimensions at the Tevatron: New Limit on the Fundamental Scale of Gravity
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.
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.
122536153
Formation of superheavy elements in cold fusion reactions
The process of the synthesis of superheavy elements ~SHEs! is not yet understood completely. In the presented work we make an attempt to describe the cold fusion reactions of the type X1(Pb,Bi)→SHE 11n at subbarrier energies. The process of the formation of SHEs is subdivided into three steps. ~1! The capture of two spherical nuclei and the formation of a common shape of the two touching nuclei. Low-energy surface vibrations and transfer of few nucleons are taken into account in the first step of the reaction. ~2! The formation of a spherical or near spherical compound nucleus. ~3! The survival of the excited compound nucleus due to evaporation of neutrons and g-ray emission in competition with fission. A lowering of the fission barrier was taken into account, which arises from a reduction of shell effects at increasing excitation energy of the compound nucleus. The following reactions were analyzed in detail: (Fe, Ni, Zn, Ge)1Pb, (Ti, Cr, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se)1Pb, (Fe, Ni, Zn, Ge) 1Pb, and (Ti, Cr, Fe, Ni, Zn, Ge)1Bi. The presented model describes well the available experimental cross-section data and allows for predicting cross-section values for the synthesis of so-far unknown heavier 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.
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.
122540307
Cross section systematics for the lightest Bi and Po nuclei produced in complete fusion reactions with heavy ions
The production of the very neutron-deficient nuclides $^{184\ensuremath{-}192}\mathrm{Bi}$ and $^{186\ensuremath{-}192}\mathrm{Po}$ in the vicinity of the neutron midshell at N = 104 has been studied by using heavy-ion-induced complete fusion reactions in a series of experiments at the velocity filter SHIP. The cross sections for the xn and pxn evaporation channels of the $^{46}\mathrm{Ti}$+$^{144}\mathrm{Sm}$$\ensuremath{\rightarrow}^{190}\mathrm{Po}{}^{*},$$^{98}\mathrm{Mo}$+$^{92}\mathrm{Mo}$$\ensuremath{\rightarrow}^{190}\mathrm{Po}{}^{*},$$^{50,52}\mathrm{Cr}$+$^{142}\mathrm{Nd}$$\ensuremath{\rightarrow}^{192,194}\mathrm{Po}{}^{*}$, and $^{94,95}\mathrm{Mo}$+$^{93}\mathrm{Nb}$$\ensuremath{\rightarrow}^{187,188}\mathrm{Bi}{}^{*}$ reactions were measured. The results obtained, together with the previously known cross section data for the heavier Bi and Po nuclides, are compared with the results of statistical model calculations carried out with the HIVAP code. It is shown that a satisfactory description of the experimental data requires a significant (up to 35%) reduction of the theoretical fission barriers. The optimal reactions for production of the lightest Bi and Po isotopes are discussed.
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.