SN1A data and the CMB of Modified Curvature at short and long distances

The SN1a data, although inconclusive, when combined with other observations makes a strong case that our universe is presently dominated by dark energy. We investigate the possibility that large distance modifications of the curvature of the universe would perhaps offer an alternative explanation of the observation. Our calculations indicate that a universe made up of no dark energy but instead, with a modified curvature at large scales, is not scale-invariant, therefore quite likely it is ruled out by the CMB observations. The sensitivity of the CMB spectrum is checked for the whole range of mode modifications of large or short distance physics. The spectrum is robust against modifications of short-distance physics and the UV cutoff when: the initial state is the adiabatic vacuum, and the inflationary background space is de Sitter.Comment: 13 pages, 2 eps figures, typos corrected, references added; to appear in Phys. Rev.

On the Background Field Method Beyond One Loop: A manifestly covariant derivative expansion in super Yang-Mills theories

There are currently many string inspired conjectures about the structure of the low-energy effective action for super Yang-Mills theories which require explicit multi-loop calculations. In this paper, we develop a manifestly covariant derivative expansion of superspace heat kernels and present a scheme to evaluate multi-loop contributions to the effective action in the framework of the background field method. The crucial ingredient of the construction is a detailed analysis of the properties of the parallel displacement propagators associated with Yang-Mills supermultiples in N-extended superspace.Comment: 32 pages, latex, 7 EPS figures. v2: references, comments added, typos corrected, incorrect `skeleton' conjecture in sect. 3 replaced by a more careful treatment. v3: typos corrected, final version published in JHE

Pion condensation of quark matter in the static Einstein universe

In the framework of an extended Nambu--Jona-Lasinio model we are studying pion condensation in quark matter with an asymmetric isospin composition in a gravitational field of the static Einstein universe at finite temperature and chemical potential. This particular choice of the gravitational field configuration enables us to investigate phase transitions of the system with exact consideration of the role of this field in the formation of quark and pion condensates and to point out its influence on the phase portraits. We demonstrate the effect of oscillations of the thermodynamic quantities as functions of the curvature and also refer to a certain similarity between the behavior of these quantities as functions of curvature and finite temperature. Finally, the role of quantum fluctuations for spontaneous symmetry breaking in the case of a finite volume of the universe is shortly discussed.Comment: RevTex4; 15 pages, 10 figure

A microcalorimetric comparison of the anti-Streptococcus mutans efficacy of plant extracts and antimicrobial agents in oral hygiene formulations

AIMS: This study aimed to evaluate the efficacy of 'natural' putative antimicrobial agents against Streptococcus mutans and to compare these with synthetic agents using the flow microcalorimeter. Streptococcus mutans is one of the oral pathogens responsible for dental caries. METHODS AND RESULTS: Traditional microbiological techniques are invasive and destructive unlike flow microcalorimetry. This rapid technique was used to continuously monitor the power output (bioactivity) of Strep. mutans with reproducibility, precision and accuracy. The antibacterial agents found in oral hygiene products and all the natural agents tested showed anti-Strep. mutans ability. CONCLUSION: In this study microcalorimetry identified agents that had a biological effect and quantified the rate of kill achieved enabling four broad categories of antimicrobial agent to be defined. SIGNIFICANCE AND IMPACT OF THE STUDY: Microcalorimetric data are a better indication of antimicrobial efficacy than merely determining concentrations at which an antimicrobial agent is bacteriostatic or bactericidal