Alternatives to Quintessence Model Building

We discuss the issue of toy model building for the dark energy component of the universe. Specifically, we consider two generic toy models recently proposed as alternatives to quintessence models, known as Cardassian expansion and the Chaplygin gas. We show that the former is enteriely equivalent to a class of quintessence models. We determine the observational constraints on the latter, coming from recent supernovae results and from the shape of the matter power spectrum. As expected, these restrict the model to a behaviour that closely matches that of a standard cosmological constant $\Lambda$.Comment: RevTex4; 7 pages, 4 figures. v2: Improved discussion of constraints on Chaplygin gas models. Other clarifications added. Phys Rev. D (in press

Use of homeopathic products in pigs feed improves the percentage, quality and marbling of meat

Abstract Studies and innovations on alternative feed additives, especially on homeopathic remedies have been highlighted in order to replace or reduce the use of antibiotics in pig production. This paper aimed to assess the addition of homeopathic products in pig diet and their effects on the growth performance, serum metabolites, nutrient and energy digestibility, carcass traits and meat quality. A total of 60 immunocastrated male pigs, weighing on average 30.91 ± 0.95 kg, were distributed in two treatments, 10 replicates and three animals/experimental unit. There was no effect (P≥0.05) of treatment on the growth performance and serum metabolites. The percentage of acid-insoluble ash recovered in the diet was greater (P≤0.01) in diets containing homeopathic products. The apparent digestible energy of diets containing homeopathic products was reduced (P≤0.01) in the growing phase and reduced (P≤0.01) the apparent digestibility coefficients of dry matter, crude protein, soluble neutral and acid detergent fibers, and gross energy in the growing and finishing phases. Pig that received diets with homeopathic products had higher (P≤0.05) amount of meat, percentage of meat and marbling. The use of homeopathic products in diets improves the percentage and quality of meat, as well as the marbling of the pig carcass, maintaining the performance

The onset of the non-linear regime in unified dark matter models

We discuss the onset of the non-linear regime in the context of unified dark matter models involving a generalised Chaplygin gas. We show that the transition from dark matter-like to dark energy-like behaviour will never be smooth. In some regions of space the transition will never take place while in others it may happen sooner or later than naively expected. As a result the linear theory used in previous studies may break down late in the matter dominated era even on large cosmological scales. We study the importance of this effect showing that its magnitude depends on the exact form of the equation of state in the low density regime. We expect that our results will be relevant for other unified dark matter scenarios particularly those where the quartessence candidate is a perfect fluid.Comment: 5 pages, 4 figure

Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe