THE HIGGS-YUKAWA MODEL IN CURVED SPACETIME

The Higgs-Yukawa model in curved spacetime (renormalizable in the usual sense) is considered near the critical point, employing the $1/N$--expansion and renormalization group techniques. By making use of the equivalence of this model with the standard NJL model, the effective potential in the linear curvature approach is calculated and the dynamically generated fermionic mass is found. A numerical study of chiral symmetry breaking by curvature effects is presented.Comment: LaTeX, 9 pages, 1 uu-figur

Pre - Inflationary Clues from String Theory ?

"Brane supersymmetry breaking" occurs in String Theory when the only available combinations of D-branes and orientifolds are not mutually BPS and yet do not introduce tree-level tachyon instabilities. It is characterized by the emergence of a steep exponential potential, and thus by the absence of maximally symmetric vacua. The corresponding low-energy supergravity admits intriguing spatially-flat cosmological solutions where a scalar field is forced to climb up toward the steep potential after an initial singularity, and additional milder terms can inject an inflationary phase during the ensuing descent. We show that, in the resulting power spectra of scalar perturbations, an infrared suppression is typically followed by a pre-inflationary peak that reflects the end of the climbing phase and can lie well apart from the approximately scale invariant profile. A first look at WMAP9 raw data shows that, while the chi^2 fits for the low-l CMB angular power spectrum are clearly compatible with an almost scale invariant behavior, they display nonetheless an eye-catching preference for this type of setting within a perturbative string regime.Comment: 34 pages, LaTeX, 16 eps figures. Relative displacement in fig. 14 and some typos corrected, references and acknowledgments updated. To appear in JCA

An Improved Substrate for Superior Imaging of Individual Biomacromolecules with Atomic Force Microscopy

© 2020 Elsevier B.V. High-resolution atomic force microscopy (AFM) of biomacromolecules is a valuable method for structural studies in biology. Traditionally, the surfaces used for AFM imaging of individual molecules are limited to mica, graphite, and glass. Because these substrates have certain shortcomings, new or modified surfaces that improve the quality of AFM imaging are highly desirable. Here, we describe an improved substrate for imaging of individual biomacromolecules with high-resolution AFM based on graphite surfaces coated by physical adsorption. We provide a detailed methodology, including the chemical structure, synthesis, characterization and the use of a substance that modifies the surface of freshly cleaved graphite, making it suitable for adsorption and AFM visualization of various biomacromolecules while minimizing spatial distortions. We illustrate the advantages of the modified graphite over regular surfaces with examples of high-resolution single-molecule imaging of proteins, polysaccharides, DNA and DNA-protein complexes. The proposed methodology is easy to use and helps to improve substantially AFM imaging of biomacromolecules of various natures, including flexible and/or unstructured sub-molecular regions that are not seen on other AFM substrates. The proposed technique has the potential to improve the use of AFM in structural biology for visualization and morphometric characterization of macromolecular objects