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51.
A nonlinear integral operator T of the form (Tf)(s)=∫G K(t, f (σ(s, t))) dμ(t), for sG, is defined and investigated in the measure space (G, Σ, μ), where f and K are vector-valued functions with values in normed linear spaces E and F, respectively. The results are applied to the case of integro-differential operators in generalized Orlicz–Sobolev spaces. There are studied problems of existence, embeddings, and approximation by means of T. 相似文献
52.
Solar System tests give nowadays constraints on the estimated value of the cosmological constant, which can be accurately
derived from different experiments regarding gravitational redshift, light deflection, gravitational time-delay and geodesic
precession. Assuming that each reasonable theory of gravitation should satisfy Solar System tests, we use these limits on
the estimated value of the cosmological constant to constrain extended theories of Gravity, which are nowadays studied as
possible theories for cosmological models and provide viable solutions to the cosmological constant problem and the explanation
of the present acceleration of the Universe. We obtain that the estimated values, from Solar System tests, for the parameters
appearing in the extended theories of Gravity are orders of magnitude bigger than the values obtained in the framework of
cosmologically relevant theories. 相似文献
53.
54.
Fluorous quaternary ammonium and phosphonium salts, as well as fluorous macrocyclic ligands, such as crown and aza-crown ethers, have been gradually emerging as viable alternatives to classical phase transfer catalysts. The major results thus far obtained in this burgeoning field will be the focus of this review. 相似文献
55.
Local four-dimensional tensor decomposition formulae for generic vectors and 2-tensors in spacetime, in terms of scalar and antisymmetric covariant tensor potentials, are studied within the framework of tensor distributions. Earlier first-order decompositions are extended to include the case of four-dimensional symmetric 2-tensors and new second-order decompositions are introduced. 相似文献
56.
57.
Gianluca DAddese Laura Sani Luca La Rocca Roberto Serra Marco Villani 《Entropy (Basel, Switzerland)》2021,23(4)
The identification of emergent structures in complex dynamical systems is a formidable challenge. We propose a computationally efficient methodology to address such a challenge, based on modeling the state of the system as a set of random variables. Specifically, we present a sieving algorithm to navigate the huge space of all subsets of variables and compare them in terms of a simple index that can be computed without resorting to simulations. We obtain such a simple index by studying the asymptotic distribution of an information-theoretic measure of coordination among variables, when there is no coordination at all, which allows us to fairly compare subsets of variables having different cardinalities. We show that increasing the number of observations allows the identification of larger and larger subsets. As an example of relevant application, we make use of a paradigmatic case regarding the identification of groups in autocatalytic sets of reactions, a chemical situation related to the origin of life problem. 相似文献
58.
In the inflationary scenario of loop quantum cosmology in the presence of inverse-volume corrections, we give analytic formulas for the power spectra of scalar and tensor perturbations convenient to compare with observations. Since inverse-volume corrections can provide strong contributions to the running spectral indices, inclusion of terms higher than the second-order runnings in the power spectra is crucially important. Using the recent data of cosmic microwave background and other cosmological experiments, we place bounds on the quantum corrections. 相似文献
59.
60.
The physical behavior of a fluid in contact with solid layers is still not fully understood. The present work focuses on the
study and understanding of thermodynamic and structural properties of gold–water nanolayer mixtures using molecular dynamics
simulations. Two different systems are considered, where approximately 1,700 water molecules are confined between gold nanolayers
with separations of 7.4 and 6.2 nm, respectively. Novelties of the present work are in the use of accurate force fields for
modeling the inter- and intra-molecular interactions of the components, and providing comprehensive thermodynamic properties
of the mixtures. The results are validated by examination of the pure fluid and pure solid properties. Results indicate that
the thermodynamics of the system does not behave as an ideal mixture. The structure of the pure fluid is also analyzed and
compared against the structure of the confined fluid in the mixture. Anisotropicity is observed in the fluid structure close
to the surface of the nanolayer. Higher ordering and higher flux are detected in the fluid molecules close to the fluid–solid
interface. Unusual thermodynamic behavior, anisotropicity, liquid layering, and higher interfacial fluid flux could be just
some of the factors leading to the enhanced energy transport observed in mixtures involving at least one nanoscale component,
such as nanofluids. 相似文献