Interventions that train parents to share picture books with children are seen as a strategy for supporting child language development. We conducted meta‐analyses using robust variance estimation ...modeling on results from 19 RCTs (Ntotal = 2,594; Mchildage = 1–6 years). Overall, book‐sharing interventions had a small sized effect on both expressive language (d = 0.41) and receptive language (d = 0.26). They had a large effect on caregiver book‐sharing competence (d = 1.01). The impact of the intervention on child language was moderated by intervention dosage, with lower dosage associated with a minimal impact. Child age and caregiver education level were unrelated to child outcome. This review and meta‐analysis confirms the promise of book‐sharing interventions for enhancing and accelerating child language development.
For the past several decades, we have been able to directly probe the motion of atoms that is associated with chemical transformations and which occurs on the femtosecond (10−15-s) timescale. ...However, studying the inner workings of atoms and molecules on the electronic timescale has become possible only with the recent development of isolated attosecond (10−18-s) laser pulses. Such pulses have been used to investigate atomic photoexcitation and photoionization and electron dynamics in solids, and in molecules could help explore the prompt charge redistribution and localization that accompany photoexcitation processes. In recent work, the dissociative ionization of H2 and D2 was monitored on femtosecond timescales and controlled using few-cycle near-infrared laser pulses. Here we report a molecular attosecond pump-probe experiment based on that work: H2 and D2 are dissociatively ionized by a sequence comprising an isolated attosecond ultraviolet pulse and an intense few-cycle infrared pulse, and a localization of the electronic charge distribution within the molecule is measured that depends-with attosecond time resolution-on the delay between the pump and probe pulses. The localization occurs by means of two mechanisms, where the infrared laser influences the photoionization or the dissociation of the molecular ion. In the first case, charge localization arises from quantum mechanical interference involving autoionizing states and the laser-altered wavefunction of the departing electron. In the second case, charge localization arises owing to laser-driven population transfer between different electronic states of the molecular ion. These results establish attosecond pump-probe strategies as a powerful tool for investigating the complex molecular dynamics that result from the coupling between electronic and nuclear motions beyond the usual Born-Oppenheimer approximation.
A
bstract
The causal representation of multi-loop scattering amplitudes, obtained from the application of the loop-tree duality formalism, comprehensively elucidates, at integrand level, the ...behaviour of only physical singularities. This representation is found to manifest compact expressions for multi-loop topologies that have the same number of
vertices
. Interestingly, integrands considered in former studies, with up-to six vertices and
L
internal lines, display the same structure of up-to four-loop ones. The former is an insight that there should be a correspondence between vertices and the collection of internal lines,
edges
, that characterise a multi-loop topology. By virtue of this relation, in this paper, we embrace an approach to properly classify multi-loop topologies according to vertices and edges. Differently from former studies, we consider the most general topologies, by connecting vertices and edges in all possible ways. Likewise, we provide a procedure to generate causal representation of multi-loop topologies by considering the structure of causal propagators. Explicit causal representations of loop topologies with up-to nine vertices are provided.
We determine the gravitational interaction between two compact bodies up to the sixth power in Newton's constant, G_{N}, in the static limit. This result is achieved within the effective field theory ...approach to general relativity, and exploits a manifest factorization property of static diagrams which allows us to derive static post Newtonian (PN) contributions of (2n+1) order in terms of lower order ones. We recompute in this fashion the 1PN and 3PN static potential, and present the novel 5PN contribution.
Lotty – The loop-tree duality automation Torres Bobadilla, William J
The European physical journal. C, Particles and fields,
06/2021, Letnik:
81, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Elaborating on the novel formulation of the loop-tree duality, we introduce the
Mathematica
package
Lotty
that automates the latter at multi-loop level. By studying the features of
Lotty
and ...recalling former studies, we discuss that the representation of any multi-loop amplitude can be brought in a form, at integrand level, that only displays physical information, which we refer to as the causal representation of multi-loop Feynman integrands. In order to elucidate the role of
Lotty
in this automation, we recall results obtained for the calculation of the dual representation of integrands up-to four loops. Likewise, within
Lotty
framework, we provide support to the all-loop causal representation recently conjectured by the same author. The numerical stability of the integrands generated by
Lotty
is studied in two-loop planar and non-planar topologies, where a numerical integration is performed and compared with known results.
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