Search results for "weak [Gravitational lensing]"
showing 10 items of 636 documents
Steady-state radiation heat transfer problem
1996
In Section 8.2, we shall see that the steady-state radiative heat transfer problem can be transformed to minimization of a smooth nonquadratic functional J over a convex and closed subset of a Banach space V. To this end we firstly shortly recall some basic definitions concerning differentiability of J, because these sometimes differ in the literature.
Analysis of a parabolic cross-diffusion population model without self-diffusion
2006
Abstract The global existence of non-negative weak solutions to a strongly coupled parabolic system arising in population dynamics is shown. The cross-diffusion terms are allowed to be arbitrarily large, whereas the self-diffusion terms are assumed to disappear. The last assumption complicates the analysis since these terms usually provide H 1 estimates of the solutions. The existence proof is based on a positivity-preserving backward Euler–Galerkin approximation, discrete entropy estimates, and L 1 weak compactness arguments. Furthermore, employing the entropy–entropy production method, we show for special stationary solutions that the transient solution converges exponentially fast to its…
Double β Decay and the Axial Strength
2019
Quenching of the weak axial strength gA is discussed and relations of this quenching to the nuclear matrix elements of double beta decays are highlighted. An analysis of Gamow-Teller transitions in the mass range A = 62 − 142 is presented and its results are compared with those of many previous works. The enhancement of the axial charge is discussed for first-forbidden pseudoscalar β transitions. Higher-forbidden β transitions are introduced and their role in determining the effective value of gA is examined, in particular from the point of view of the β-decay half-lives and the shapes of electron spectra of forbidden non-unique β transitions. peerReviewed
First-Principles Calculation of Electroweak Box Diagrams from Lattice QCD.
2020
We present the first realistic lattice QCD calculation of the $\gamma W$-box diagrams relevant for beta decays. The nonperturbative low-momentum integral of the $\gamma W$ loop is calculated using a lattice QCD simulation, complemented by the perturbative QCD result at high momenta. Using the pion semileptonic decay as an example, we demonstrate the feasibility of the method. By using domain wall fermions at the physical pion mass with multiple lattice spacings and volumes, we obtain the axial $\gamma W$-box correction to the semileptonic pion decay, $\Box_{\gamma W}^{VA}\big|_{\pi}=2.830(11)_{\mathrm{stat}}(26)_{\mathrm{sys}}\times10^{-3}$, with the total uncertainty controlled at the leve…
Spin–isospin excitations probed by strong, weak and electro-magnetic interactions
2011
Abstract Gamow–Teller (GT) transitions are the most common weak interaction processes of spin–isospin ( σ τ ) type in atomic nuclei. They are of interest not only in nuclear physics but also in astrophysics; they play an important role in supernovae explosions and nucleosynthesis. The direct study of weak decay processes, however, gives relatively limited information about GT transitions and the states excited via GT transitions (GT states); β decay can only access states at excitation energies lower than the decay Q -value, and neutrino-induced reactions have very small cross-sections. However, one should note that β decay has a direct access to the absolute GT transition strengths B (GT) …
Bayesian Analysis of a Future Beta Decay Experiment's Sensitivity to Neutrino Mass Scale and Ordering
2021
Bayesian modeling techniques enable sensitivity analyses that incorporate detailed expectations regarding future experiments. A model-based approach also allows one to evaluate inferences and predicted outcomes, by calibrating (or measuring) the consequences incurred when certain results are reported. We present procedures for calibrating predictions of an experiment's sensitivity to both continuous and discrete parameters. Using these procedures and a new Bayesian model of the $\beta$-decay spectrum, we assess a high-precision $\beta$-decay experiment's sensitivity to the neutrino mass scale and ordering, for one assumed design scenario. We find that such an experiment could measure the el…
Are compliance constants ill-defined descriptors for weak interactions?
2013
Just as the potential energy can be written as a quadratic form in internal coordinates, so it can also be expanded in terms of generalized forces. The resulting coefficients are termed compliance constants. In this article, the suitability of compliance constants as non-covalent bond strength descriptors is studied (a) for a series of weakly bound hydrogen halide–rare gas complexes applying a configuration interaction theory, (b) for a double stranded DNA 4-mer using approximate density functional methods and finally (c) for a double stranded DNA 20-mer using empirical force fields. Our results challenge earlier studies, which concluded the inappropriateness of compliance constants as soft…
INFLUENZA DEL FABRIC E DEL BONDING SULLO STATO CRITICO E SULLO SNERVAMENTO DELLE CALCARENITI
2011
The research has been devoted to the theoretical interpretation and to the modeling of the mechanical behavior of Quaternary structured soils in the Western South-Western Sicily belonging to the complex calcarenitic-sandy-clayey. After a review about the state of knowledge on the influence of textural characteristics such as fabric and bonding on mechanical behavior, this note presents the results of an experimental analysis by mean of textural identification tests, oedometer tests, triaxial and isotropic tests. For each lithotype critical state conditions and yield strength are defined.
Grid-Forming Converters in Weak Grids – The Case of a Mediterranean Island
2019
The existing power network of a Mediterranean island is used as test bed for the study of grid-forming converter dynamics in weak grid conditions. The control scheme adopted for the converter falls in the category of the so called virtual synchronous machines (VSM). Particular attention is committed to the interaction between the converter controls and the synchronous machines dynamics. Time delays typically associated to measurements and filters are considered in the study, and included in the system model with a specific mathematical approach. Time-domain simulations show the occurrence of oscillatory instability in the system, with VSM and synchronous machines swinging against each other…
On Problems Driven by the (p(·) , q(·)) -Laplace Operator
2020
The aim of this paper is to prove the existence of at least one nontrivial weak solution for equations involving the (p(· ) , q(· ) ) -Laplace operator. The approach is variational and based on the critical point theory.