Noether symmetry approach in phantom quintessence cosmology

In the framework of phantom quintessence cosmology, we use the Noether Symmetry Approach to obtain general exact solutions for the cosmological equations. This result is achieved by the quintessential (phantom) potential determined by the existence of the symmetry itself. A comparison between the theoretical model and observations is worked out. In particular, we use type Ia supernovae and large scale structure parameters determined from the 2-degree Field Galaxy Redshift Survey (2dFGRS)and from the Wide part of the VIMOS-VLT Deep Survey (VVDS). It turns out that the model is compatible with the presently available observational data. Moreover we extend the approach to include radiation. We show that it is compatible with data derived from recombination and it seems that quintessence do not affect nucleosynthesis results.Comment: 26 pages, 13 figure

(Non)Invariance of dynamical quantities for orbit equivalent flows

We study how dynamical quantities such as Lyapunov exponents, metric entropy, topological pressure, recurrence rates, and dimension-like characteristics change under a time reparameterization of a dynamical system. These quantities are shown to either remain invariant, transform according to a multiplicative factor or transform through a convoluted dependence that may take the form of an integral over the initial local values. We discuss the significance of these results for the apparent non-invariance of chaos in general relativity and explore applications to the synchronization of equilibrium states and the elimination of expansions

Constraints on alternative models to dark energy

The recent observations of type Ia supernovae strongly support that the universe is accelerating now and decelerated in the recent past. This may be the evidence of the breakdown of the standard Friemann equation. We consider a general modified Friedmann equation. Three different models are analyzed in detail. The current supernovae data and the Wilkinson microwave anisotropy probe data are used to constrain these models. A detailed analysis of the transition from the deceleration phase to the acceleration phase is also performed.Comment: 10 pages, 1 figure, revtex

No maintenance -- no energy efficiency

Field investigations illustrate that it is not realistic to expect new high-tech equipment to function for a full life expectancy at high efficiency without significant operations and maintenance (O&M). A simple walk through inspection of most buildings reveals extensive equipment that is being operated on manual override, is incorrectly adjusted and operating inefficiently, or is simply inoperative. This point is illustrated with two examples at Robins Air Force Base, Georgia. The first describes development of a comprehensive, base-wide, steam trap maintenance program. The second describes a measured evaluation from a typical office building. The objective of both examples was to assess the importance of proper O&M. The proposed ``O&M First`` philosophy will result in more efficient building HVAC operation, provide improved services to the building occupants, and reduce energy consumption and unscheduled equipment repair/replacement. Implementation of a comprehensive O&M program will result in a 15--25% energy savings. The O&M foundation that is established will allow other energy conservation activities such is demand side management or energy management and control systems, to achieve and maintain their expected energy savings

Equation of state for Universe from similarity symmetries

In this paper we proposed to use the group of analysis of symmetries of the dynamical system to describe the evolution of the Universe. This methods is used in searching for the unknown equation of state. It is shown that group of symmetries enforce the form of the equation of state for noninteracting scaling multifluids. We showed that symmetries give rise the equation of state in the form $p=-\Lambda+w_{1}\rho(a)+w_{2}a^{\beta}+0$ and energy density $\rho=\Lambda+\rho_{01}a^{-3(1+w)}+\rho_{02}a^{\beta}+\rho_{03}a^{-3}$, which is commonly used in cosmology. The FRW model filled with scaling fluid (called homological) is confronted with the observations of distant type Ia supernovae. We found the class of model parameters admissible by the statistical analysis of SNIa data. We showed that the model with scaling fluid fits well to supernovae data. We found that $\Omega_{\text{m},0} \simeq 0.4$ and $n \simeq -1$ ($\beta = -3n$), which can correspond to (hyper) phantom fluid, and to a high density universe. However if we assume prior that $\Omega_{\text{m},0}=0.3$ then the favoured model is close to concordance $\Lambda$CDM model. Our results predict that in the considered model with scaling fluids distant type Ia supernovae should be brighter than in $\Lambda$CDM model, while intermediate distant SNIa should be fainter than in $\Lambda$CDM model. We also investigate whether the model with scaling fluid is actually preferred by data over $\Lambda$CDM model. As a result we find from the Akaike model selection criterion prefers the model with noninteracting scaling fluid.Comment: accepted for publication versio

Anisotropy and inflation in Bianchi I brane worlds

After a more general assumption on the influence of the bulk on the brane, we extend some conclusions by Maartens et al. and Santos et al. on the asymptotic behavior of Bianchi I brane worlds. As a consequence of the nonlocal anisotropic stresses induced by the bulk, in most of our models, the brane does not isotropize and the nonlocal energy does not vanish in the limit in which the mean radius goes to infinity. We have also found the intriguing possibility that the inflation due to the cosmological constant might be prevented by the interaction with the bulk. We show that the problem for the mean radius can be completely solved in our models, which include as particular cases those in the references above.Comment: 10 pages, improved discussion on the likeliness of non-isotropization, completed list of references, matches version to appear in Class. Quantum Gra

Advanced metering techniques in the federal sector

The lack of utility metering in the federal sector has hampered introduction of direct billing of individual activities at most military installations. Direct billing will produce accountability for the amount of energy used and is a positive step toward self-directed energy conservation. For many installations, automatic meter reading (AMR) is a cost-effective way to increase the number of meters while reducing labor requirements and providing energy conservation analysis capabilities. The communications technology used by some of the AMR systems provides other demand-side management (DSM) capabilities. This paper summarizes the characteristics and relative merits of several AMR/DSM technologies that may be appropriate for the federal sector. A case study of an AMR system being installed at Fort Irwin, California, describes a cost-effective two-way radio communication system used for meter reading and load control

Classification of the FRW universe with a cosmological constant and a perfect fluid of the equation of state p=wρp = w\rho

We systematically study the evolution of the Friedmann-Robertson-Walker (FRW) universe coupled with a cosmological constant $\Lambda$ and a perfect fluid that has the equation of state $p=w\rho$, where $p$ and $\rho$ denote, respectively, the pressure and energy density of the fluid, and $w$ is an arbitrary real constant. Depending on the specific values of $w,\; \Lambda$, and the curvature $k$ of 3-dimensional space, we separate all of the solutions into various cases. In each case the main properties of the evolution are given in detail, including the periods of deceleration and/or acceleration, and the existence of big bang, big crunch, and big rip singularities. In some cases, errors in classification and interpretation appearing in standard textbooks have been corrected.Comment: revtex4, 24 figure