6 research outputs found
Discriminating quantum gravity models by gravitational decoherence
Several phenomenological approaches to quantum gravity assume the existence
of a minimal measurable length and/or a maximum measurable momentum near the
Planck scale. When embedded into the framework of quantum mechanics, such
constraints induce a modification of the canonical commutation relations and
thus a generalization of the Heisenberg uncertainty relations, commonly
referred to as generalized uncertainty principle (GUP). Different models of
quantum gravity imply different forms of the GUP. For instance, in the
framework of string theory the GUP is quadratic in the momentum operator, while
in the context of doubly special relativity it includes an additional linear
dependence. Among the possible physical consequences, it was recently shown
that the quadratic GUP induces a universal decoherence mechanism, provided one
assumes a foamy structure of quantum spacetime close to the Planck length.
Along this line, in the present work we investigate the gravitational
decoherence associated to the linear-quadratic GUP and we compare it with the
one associated to the quadratic GUP. We find that, despite their similarities,
the two generalizations of the Heisenberg uncertainty principle yield
decoherence times that are completely uncorrelated and significantly distinct.
Motivated by this result, we introduce a theoretical and experimental scheme
based on cavity optomechanics to measure the different time evolution of
nonlocal quantum correlations corresponding to the two aforementioned
decoherence mechanisms. We find that the deviation between the two predictions
occurs on time scales that are macroscopic and thus potentially amenable to
experimental verification. This scenario provides a possible setting to
discriminate between different forms of the GUP and therefore different models
of quantum gravity.Comment: v1: 11 pages, 2 figures; v2: 11 pages, 2 figures, title, abstract and
references slightly edited and updated for better clarity; no change in the
physics; v3: 14 pages, 3 figures, title changed, new section and
clarifications adde
Chemical Vapour Deposition of Graphene—Synthesis, Characterisation, and Applications: A Review
Graphene as the 2D material with extraordinary properties has attracted the interest of research communities to master the synthesis of this remarkable material at a large scale without sacrificing the quality. Although Top-Down and Bottom-Up approaches produce graphene of different quality, chemical vapour deposition (CVD) stands as the most promising technique. This review details the leading CVD methods for graphene growth, including hot-wall, cold-wall and plasma-enhanced CVD. The role of process conditions and growth substrates on the nucleation and growth of graphene film are thoroughly discussed. The essential characterisation techniques in the study of CVD-grown graphene are reported, highlighting the characteristics of a sample which can be extracted from those techniques. This review also offers a brief overview of the applications to which CVD-grown graphene is well-suited, drawing particular attention to its potential in the sectors of energy and electronic devices
Effect of LaNi3 Amorphous Alloy Nanopowders on the Performance and Hydrogen Storage Properties of MgH2
Due to its affordable price, abundance, high storage capacity, low recycling coast, and easy processing, Mg metal is considered as a promising hydrogen storage material. However, the poor de/rehydrogenation kinetics and strong stability of MgH2 must be improved before proposing this material for applications. Doping MgH2 powders with one or more catalytic agents is one common approach leading to obvious improving on the behavior of MgH2. The present study was undertaken to investigate the effect of doping MgH2 with 7 wt% of amorphous(a)-LaNi3 nanopowders on hydrogenation/dehydrogenation behavior of the metal hydride powders. The results have shown that rod milling MgH2 with a-LaNi3 abrasive nanopowders led to disintegrate microscale-MgH2 powders to nanolevel. The final nanocomposite product obtained after 50 h–100 h of rod milling revealed superior hydrogenation kinetics, indexed by short time (8 min) required to absorb 6 wt% of H2 at 200 °C/10 bar. At 225 °C/200 mbar, nanocomposite powders revealed outstanding dehydrogenation kinetics, characterized by very short time (2 min) needed to release 6 wt% of H2. This new tailored solid-hydrogen storage system experienced long cycle-life-time (2000 h) at 225 °C without obeying to sever degradation on its kinetics and/or storage capacity