Understanding de Sitter space in supergravity-and string theory-has led to an intense amount of work for more than two decades, largely motivated by the discovery of the accelerated expansion of the Universe in 1998. In this paper, we consider a non-trivial generalization of unimodular gravity to minimal supergravity, which allows for de Sitter solutions without the need of introducing any matter. We formulate a superspace version of the Stückelberg procedure, which restores diffeomorphism and local supersymmetry invariance.
View Article and Find Full Text PDFWe revisit the status of scalar-tensor theories with applications to dark energy in the aftermath of the gravitational wave signal GW170817 and its optical counterpart GRB170817A. At the level of the cosmological background, we identify a class of theories, previously declared unviable in this context, whose anomalous gravitational wave speed is proportional to the scalar equation of motion. As long as the scalar field is assumed not to couple directly to matter, this raises the possibility of compatibility with the gravitational wave data, for any cosmological sources, thanks to the scalar dynamics.
View Article and Find Full Text PDFThis paper presents a systematic review of the perception systems and simulators for autonomous vehicles (AV). This work has been divided into three parts. In the first part, perception systems are categorized as environment perception systems and positioning estimation systems.
View Article and Find Full Text PDFGravitational models of self-tuning are those in which vacuum energy has no observable effect on spacetime curvature, even though it is a priori unsuppressed below the cutoff. We complement Weinberg's no-go theorem by studying field-theoretic completions of self-adjustment allowing for broken translations as well as other generalizations, and identify new obstructions. Our analysis uses a very general Källén-Lehmann spectral representation of the exchange amplitude for conserved sources of energy-momentum and exploits unitarity and Lorentz invariance to show that a transition from self-tuning of long wavelength sources to near general relativity (GR) on shorter scales is generically not possible.
View Article and Find Full Text PDFWe recently formulated a local mechanism of vacuum energy sequester. This mechanism automatically removes all matter loop contributions to vacuum energy from the stress energy tensor which sources the curvature. Here we adapt the local vacuum energy sequestering mechanism to also cancel all the vacuum energy loops involving virtual gravitons, in addition to the vacuum energy generated by matter fields alone.
View Article and Find Full Text PDFWe present a manifestly local, diffeomorphism invariant, and locally Poincaré invariant formulation of vacuum energy sequestering. In this theory, quantum vacuum energy generated by matter loops is canceled by auxiliary fields. The auxiliary fields decouple from gravity almost completely.
View Article and Find Full Text PDFRecently, we proposed a mechanism for sequestering the standard model vacuum energy that predicts that the Universe will collapse. Here we present a simple mechanism for bringing about this collapse, employing a scalar field whose potential is linear and becomes negative, providing the negative energy density required to end the expansion. The slope of the potential is chosen to allow for the expansion to last until the current Hubble time, about 10^{10} years, to accommodate our Universe.
View Article and Find Full Text PDFWe propose a very simple reformulation of general relativity, which completely sequesters from gravity all of the vacuum energy from a matter sector, including all loop corrections and renders all contributions from phase transitions automatically small. The idea is to make the dimensional parameters in the matter sector functionals of the 4-volume element of the Universe. For them to be nonzero, the Universe should be finite in spacetime.
View Article and Find Full Text PDFThis work deals with the effect of the addition of inulin and bovine plasma proteins as fat replacers, on the quality of minced meat. The proteins are obtained by ultrafiltration and freeze-drying. The following determinations were carried out: chemical composition, sensorial analysis (color, flavor, taste and consistency), emulsion stability and instrumental texture analysis of samples.
View Article and Find Full Text PDFBy using a non-Markovian spectral theory based in the Kubo cumulant expansion technique, we have qualitatively studied the infrared Q branch observed in the fundamental absorption band of HCl diluted in liquid Ar. The statistical parameters of the anisotropic interaction present in this spectral theory were calculated by means of molecular dynamics techniques, and found that the values of the anisotropic correlation times are significantly greater (by a factor of two) than those previously obtained by fitting procedures or microscopic cell models. This fact is decisive for the observation in the theoretical spectral band of a central Q resonance which is absent in the abundant previous researches carried out with the usual theories based in Kubo cumulant expansion techniques.
View Article and Find Full Text PDFThe de Rham-Gabadadze-Tolley theory of a single massive spin-2 field has a cutoff much below its Planck scale because the extra modes from the massive spin-2 multiplet involve higher derivative self-interactions, controlled by a scale convoluted from its mass. Generically, these correct the propagator by environmental effects. The resulting effective cutoff depends on the environmental parameters and the spin-2 "graviton" mass.
View Article and Find Full Text PDFGlyphosate formulations toxicity depends on all its components but commercial products only specify the active principle in their label. To treat contaminated waters and to verify if the unknown components which add toxicity have been removed represent a challenge. Nanofiltration and permeate analysis by toxicity tests with fish are an interesting alternative to evaluate the process.
View Article and Find Full Text PDFStarting from the most general scalar-tensor theory with second-order field equations in four dimensions, we establish the unique action that will allow for the existence of a consistent self-tuning mechanism on Friedmann-Lemaître-Robertson-Walker backgrounds, and show how it can be understood as a combination of just four base Lagrangians with an intriguing geometric structure dependent on the Ricci scalar, the Einstein tensor, the double dual of the Riemann tensor, and the Gauss-Bonnet combination. Spacetime curvature can be screened from the net cosmological constant at any given moment because we allow the scalar field to break Poincaré invariance on the self-tuning vacua, thereby evading the Weinberg no-go theorem. We show how the four arbitrary functions of the scalar field combine in an elegant way opening up the possibility of obtaining nontrivial cosmological solutions.
View Article and Find Full Text PDFIntrinsic viscosity of bovine serum albumin (BSA) at different pH values (2.7, 4.3, 7.
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