Analytical approach to the transition to thermal hopping in the thin- and thick-wall approximations

The nature of the transition from the quantum tunneling regime at low temperatures to the thermal hopping regime at high temperatures is investigated analytically in scalar field theory. An analytical bounce solution is presented, which reproduces the action in the thin-wall as well as thick-wall limits. The transition is first order for the case of a thin wall while for the thick wall case it is second order.Comment: Latex file, 22 pages, 4 Postscript figure

Bounce solutions and the transition to thermal hopping in phi^4 theory with a phi^3 term

The nature of the transition from quantum tunneling at low temperatures to thermal hopping at high temperatures is investigated in a scalar field theory with cubic symmetry breaking. The bounce solution which interpolates between the zero-temperature and high-temperature solutions is obtained numerically, using a multigrid method. It is found that, for a small value of the symmetry-breaking coupling f, the transition is first-order. For higher values of f, the transition continues to be first-order, though weakly so.Comment: Latex file with 18 figures, 29 page

Cosmological models consistent with supersymmetric compactification of superstring theories

The compactification of 10-dimensional supergravity, coupled to super Yang-Mills theory, to curved 4-dimensional spacetimes is investigated. The requirement of unbroken supersymmetry leads to a set of consistency conditions. These are fairly restrictive, but nevertheless permit some nontrivial solutions, including the Milne universe. More general time-dependent metrics are also not ruled out

Neutral current effects in parity violating nuclear force

The measurements of the ΔI= 1 part of the parity violating nuclear force when combined with information on neutral current couplings from neutriro scattering and pion production experiments allow an estimate of the isoscalar admixture in the neutral current if it nas a vector axial-vector structure has been shown

Development and Applications of Fluorogen/Light-Up RNA Aptamer Pairs for RNA Detection and More.

The central role of RNA in living systems made it highly desirable to have noninvasive and sensitive technologies allowing for imaging the synthesis and the location of these molecules in living cells. This need motivated the development of small pro-fluorescent molecules called "fluorogens" that become fluorescent upon binding to genetically encodable RNAs called "light-up aptamers." Yet, the development of these fluorogen/light-up RNA pairs is a long and thorough process starting with the careful design of the fluorogen and pursued by the selection of a specific and efficient synthetic aptamer. This chapter summarizes the main design and the selection strategies used up to now prior to introducing the main pairs. Then, the vast application potential of these molecules for live-cell RNA imaging and other applications is presented and discussed.journal article2020importe

Effect of density distribution and ray bending on resonant pion-nucleus scattering

The dependence of the pion-nucleus total scattering cross section on the realistic density distribution is studied for the nuclei <SUP>12</SUP>C, <SUP>32</SUP>S,<SUP> 120</SUP>Sn and <SUP>208</SUP>Pb. The model used is based on the use of a pion propagator to calculate the potential and includes many-body effects. The potential is used in the Glauber formalism to calculate the cross sections. Realistic density distributions based on electron scattering data improve the fit to the experimental data and are insensitive to details of the parametrisation. The corrections due to ray bending are calculated and seem in general to be negligible. The resonance position as indicated by the vanishing of the real part of the amplitude is found not to shift down with mass number, though the maxima of the cross section curves are well fitted

Many body effects in resonant pion nucleus scattering

The many-body approach of Barshay et al. for resonant pion-nucleus scattering is extended to non-uniform density distribution s and compared with recent total cross section data for 12C, 32S, 120Sn and 208Pb. For light nuclei the shapes and magnitudes are very well reproduced and represents an improvement over fits not using many-body corrections. A recent modification suggested by linearing the Low equation is seen to be not very significant for these calculations