Finite quantum gravity in dS and AdS spacetimes

We hereby study the properties of a large class of weakly nonlocal gravitational theories around the (anti-) de Sitter spacetime background. In particular, we explicitly prove that the kinetic operator for the graviton field has the same structure as the one in Einstein-Hilbert theory around any maximally symmetric spacetime. Therefore, the perturbative spectrum is the same of standard general relativity, while the propagator on any maximally symmetric spacetime is a mere generalization of the one from Einstein's gravity derived and extensively studied in several previous papers. At quantum level the range of theories here presented is superrenormalizable or finite when proper (non affecting the propagator) terms cubic or higher in curvatures are added. Finally, it is proven that for a large class of nonlocal theories, which in their actions do involve neither the Weyl nor the Riemann tensor, the theory is classically equivalent to the Einstein-Hilbert one with cosmological constant by means of a metric field redefinition at any perturbative order.Comment: 24 pages, final version with journal correction

Mass spectrum from stochastic Levy-Schroedinger relativistic equations: possible qualitative predictions in QCD

Starting from the relation between the kinetic energy of a free Levy-Schroedinger particle and the logarithmic characteristic of the underlying stochastic process, we show that it is possible to get a precise relation between renormalizable field theories and a specific Levy process. This subsequently leads to a particular cut-off in the perturbative diagrams and can produce a phenomenological mass spectrum that allows an interpretation of quarks and leptons distributed in the three families of the standard model.Comment: 8 pages, no figures. arXiv admin note: substantial text overlap with arXiv:1008.425

Einstein Equations and MOND Theory from Debye Entropic Gravity

Verlinde's proposal on the entropic origin of gravity is based strongly on the assumption that the equipartition law of energy holds on the holographic screen induced by the mass distribution of the system. However, from the theory of statistical mechanics we know that the equipartition law of energy does not hold in the limit of very low temperature. Inspired by the Debye model for the equipartition law of energy in statistical thermodynamics and adopting the viewpoint that gravitational systems can be regarded as a thermodynamical system, we modify Einstein field equations. We also perform the study for Poisson equation and modified Newtonian dynamics (MOND). Interestingly enough, we find that the origin of the MOND theory can be understood from Debye entropic gravity perspective. Thus our study may fill in the gap existing in the literature understanding the theoretical origin of MOND theory. In the limit of high temperature our results reduce to their respective standard gravitational equations.Comment: 8 pages, no figures. Accepted for publication in JCA

Efeitos da irrigação e de níveis de nitrogênio em aspectos qualitativos e nutricionais da figueira (Ficus carica L.)

In order to evaluate qualitative and nutritional aspects of fig-trees with respect to six irrigation and six nitrogen levels, at Ilha Solteira, SP, Brazil, an experiment was carried out in randomized blocks, with subdivided plots, and four replications. Results showed that in four dates during harvest, only the first analysis (January 2, 1991) showed influence of nitrogen fertilization on fruit soluble solids (brix). There was no significant effect of treatments on pulp/peel relation for the four harvestings. In relation to leaf macronutrient concentration at flowering, water supply influenced N, P and Ca concentrations, and nitrogen influenced only Ca concentration. For an average of 10 t.ha-1 of mature fruit and 1.3 t.ha-1 of immature fruit production, there was a nutrient export of about 65 kg.ha-1 of N; 10 kg.ha-1 of P2O5; 44 kg.ha-1 of K2O; 35 kg.ha-1 of Ca and 9 kg.ha-1 of Mg.Para avaliar aspectos qualitativos e nutricionais da figueira em relação a seis níveis de irrigação e de nitrogênio, desenvolveu-se um experimento em blocos ao acaso, com parcelas subdivididas e com quatro repetições, em Ilha Solteira,SP. Os resultados mostraram que em quatro datas de colheita, apenas a primeira análise (2 de janeiro de 91) mostrou influência da fertilização nitrogenada sobre os sólidos solúveis (brix) dos frutos. Não houve efeito significativo dos tratamentos sobre a relação polpa/casca, nas quatro colheitas. Com relação à concentração de macronutrientes nas folhas na época de florescimento, o suprimento de água influenciou as concentrações de N, P e Ca e a aplicação de nitrogênio influenciou apenas a concentração de Ca. Para uma produção média de 10 t.ha-1 de frutos maduros e de 1,3 t.ha-1 de frutos verdes, observou-se uma exportação de aproximadamente 65 kg.ha-1 de N; 10 kg.ha-1 de P2O5 ; 44 kg.ha-1 de K2O; 35 kg.ha-1 de Ca e 9 kg.ha-1 de Mg

Omicron Mutations Increase Interdomain Interactions and Reduce Epitope Exposure in the SARS-CoV-2 Spike

Omicron BA.1 is a highly infectious variant of SARS-CoV-2 that carries more than thirty mutations on the spike protein in comparison to the Wuhan wild type (WT). Some of the Omicron mutations, located on the receptor binding domain (RBD), are exposed to the surrounding solvent and are known to help evade immunity. However, the impact of buried mutations on the RBD conformations and on the mechanics of the spike opening is less evident. Here, we use all-atom molecular dynamics (MD) simulations with metadynamics to characterize the thermodynamic RBD-opening ensemble, identifying significant differences between WT and Omicron. Specifically, the Omicron mutations S371L, S373P, and S375F make more RBD interdomain contacts during the spike's opening. Moreover, Omicron takes longer to reach the transition state than WT. It stabilizes up-state conformations with fewer RBD epitopes exposed to the solvent, potentially favoring immune or antibody evasion.© 2023 The Author(s)

Spinning Loop Black Holes

In this paper we construct four Kerr-like spacetimes starting from the loop black hole Schwarzschild solutions (LBH) and applying the Newman-Janis transformation. In previous papers the Schwarzschild LBH was obtained replacing the Ashtekar connection with holonomies on a particular graph in a minisuperspace approximation which describes the black hole interior. Starting from this solution, we use a Newman-Janis transformation and we specialize to two different and natural complexifications inspired from the complexifications of the Schwarzschild and Reissner-Nordstrom metrics. We show explicitly that the space-times obtained in this way are singularity free and thus there are no naked singularities. We show that the transformation move, if any, the causality violating regions of the Kerr metric far from r=0. We study the space-time structure with particular attention to the horizons shape. We conclude the paper with a discussion on a regular Reissner-Nordstrom black hole derived from the Schwarzschild LBH and then applying again the Newmann-Janis transformation.Comment: 18 pages, 18 figure

Cursos como processo de transferência de tecnologia na Embrapa Amazônia Oriental.

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Entropic corrections to Newton's law

In this short letter we calculate separately the generalized uncertainty principle (GUP) and self gravitational corrections to the Newton's gravitational formula. We show that for a complete description of the GUP and self-gravity effects, both temperature and the entropy must be modified.Comment: 4 pages, Accepted for publication in "Physica Scripta",Title changed, Major revisio