Rotating dust solutions of Einstein's equations with 3-dimensional symmetry groups, Part 3: All Killing fields linearly independent of u^{\alpha} and w^{\alpha}

This is the third and last part of a series of 3 papers. Using the same method and the same coordinates as in parts 1 and 2, rotating dust solutions of Einstein's equations are investigated that possess 3-dimensional symmetry groups, under the assumption that each of the Killing vectors is linearly independent of velocity $u^{\alpha}$ and rotation $w^{\alpha}$ at every point of the spacetime region under consideration. The Killing fields are found and the Killing equations are solved for the components of the metric tensor in every case that arises. No progress was made with the Einstein equations in any of the cases, and no previously known solutions were identified. A brief overview of literature on solutions with rotating sources is given.Comment: One missing piece, signaled after eq. (10.7), is added after (10.21). List of corrections: In (3.7) wrong subscript in vorticity; In (3.10) wrong subscript in last term of g_{23}; In (4.23) wrong formulae for g_{12} and g_{22}; In (7.17) missing factor in velocity; In (7.18) one wrong factor in g_{22}; In (10.9) factor in vorticity; In (10.15) - (10.20) y_0 = 0; In (10.20) wrong second term in y. The rewriting typos did not influence result

Evolution of polarization orientations in a flat universe with vector perturbations: CMB and quasistellar objects

Various effects produced by vector perturbations (vortical peculiar velocity fields) of a flat Friedmann-Robertson-Walker background are considered. In the presence of this type of perturbations, the polarization vector rotates. A formula giving the rotation angle is obtained and, then, it is used to prove that this angle depends on both the observation direction and the emission redshift. Hence, rotations are different for distinct quasars and also for the cosmic microwave background (CMB) radiation coming along different directions (from distinct points of the last scattering surface). As a result of these rotations, some correlations could appear in an initially random field of quasar polarization orientations. Furthermore, the polarization correlations of the CMB could undergo alterations. Quasars and CMB maps are both considered in this paper. In the case of linear vector modes with very large spatial scales, the maximum rotation angles appear to be of a few degrees for quasars (located at redshifts z<2.6) and a few tenths of degree for the CMB. These last rotations produce contributions to the B mode of the CMB polarization which are too small to be observed with PLANCK (in the near future); however, these contributions are large enough to be observed with the next generation of satellites, which are being designed to detect the small B mode produced by primordial gravitational waves

On the Anisotropy of E0 >= 5.5×\times1019 eV Cosmic Rays according to Data of the Pierre Auger Collaboration

The Pierre Auger Collaboration discovered, in a solid angle of radius about 18\degree, a local group of cosmic rays having energies in the region E0 \geq 5.5\times1019 eV and coming from the region of the Gen A radio galaxy, whose galactic coordinates are lG = 309.5\degree and bG = 19.4\degree. Near it, there is the Centaur supercluster of galaxies, its galactic coordinates being lG = 302.4\degree and bG = 21.6\degree. It is noteworthy that the Great Attractor, which may have a direct bearing on the observed picture, is also there

Energy and Angular Momentum Densities in a Godel-Type Universe in the Teleparallel Geometry

The main scope of this research consists in evaluating the energy-momentum (gravitational field plus matter) and gravitational angular momentum densities in the universe with global rotation, considering the Godel-Obukhov metric. For this, we use the Hamiltonian formalism of the Teleparallel Equivalent of General Relativity (TEGR), which is justified for presenting covariant expressions for the considered quantities. We found that the total energy density calculated by the TEGR method is in agreement with the results reported by other authors in the literature using pseudotensors. The result found for the angular momentum density depends on the rotational parameter as expected. We also show explicitly the equivalence among the field equations of the TEGR and Einstein equations (RG), considering a perfect fluid and Godel-Obukhov metric.Comment: 20 pages, no figures. Revised in view of Referee's comments. Version to appear in the Gravitation and Cosmolog

Energy analysis and process simulation for the energy efficiency improvement of existing chemical plants

In recent years, energy efficiency has been one of the topics of major concern from a worldwide perspective as clearly stated by the International Energy Agency (IEA,2021). The energy waste reduction not only improves the process performances from an economic perspective but reduces as well the equivalent CO2 emissions. This research work is the product of a collaboration between the SIBUR petrochemical company and the Tomsk and Milan Polytechnic Universities during the Process Operations Management program aiming at the training of the personnel and at the troubleshooting practical problems of the petrochemical industry. SIBUR is a petrochemical company with a unique business model focused on the integrated operation of two main segments, namely fuel and raw materials and petrochemistry. Inefficient use and big losses of steam/condensate, obsolete equipment are the main reasons for the development of energy efficient strategies. Different sites need identification of real technical problems and process drawbacks by application of novel approaches and local methods. This work deals then with the analysis of light hydrocarbon unit with the purpose of reducing energy consumption and solving operational problems. Structuring and analysis of information on the consumption and distribution of steam and condensate at the operated unit were performed. Main drawbacks were detected and technical measures for a more efficient redistribution/involvement of steam in production processes were proposed. Process simulation of light hydrocarbon unit with the related utility streams and equipment was performed via Aspen HYSYS. Revamping of existing heat exchanger network and application of extra units for better heat recovery and most efficient utility use were proposed according to established energy optimization methodologies. The results were then validated by a detailed design of the additional heat exchangers and consequent simulation of the optimized process scheme. As a result, the formation of secondary boiling steam in tanks and associated losses into the environment was reduced by 100 %; the electricity consumption for chillers was decreased by 20%; steam consumption was cut by 64% on the heater; debottlenecking allows to increase the yield of current units and improve plant efficiency; reduction of inefficient use of steam at steam header by 71%. The equipment design and the updated economic assessment were performed as well and resulted in substantial savings for the company. Moreover, according with established indicators, an additional environmental analysis was carried out and showed relevant CO2 emissions reduction corresponding to the methane not used for combustion thanks to the energy recovery.In conclusion, the detailed energy analysis and process simulation of the existing plants allowed not only for a considerably higher profitability of the process in general but also for a higher sustainability in agreement with the world guidelines concerning the environmental impact of the industry