2,146 research outputs found
A dynamical symmetry breaking model in Weyl space
The dynamical process following the breaking of Weyl geometry to Riemannian
geometry is considered by studying the motion of de Sitter bubbles in a Weyl
vacuum. The bubbles are given in terms of an exact, spherically symmetric thin
shell solution to the Einstein equations in a Weyl-Dirac theory with a
time-dependent scalar field of the form beta = f(t)/r. The dynamical solutions
obtained lead to a number of possible applications. An important feature of the
thin shell model is the manner in which beta provides a connection between the
interior and exterior geometries since information about the exterior geometry
is contained in the boundary conditions for beta.Comment: 18 pages, RevTex, to be published in J. Math. Phy
Neutrino optics and oscillations in gravitational fields
We study the propagation of neutrinos in gravitational fields using wave
functions that are exact to first order in the metric deviation. For
illustrative purposes, the geometrical background is represented by the
Lense-Thirring metric. We derive explicit expressions for neutrino deflection,
helicity transitions, flavor oscillations and oscillation Hamiltonian.Comment: 16 page
Can Gravity Distinguish Between Dirac and Majorana Neutrinos?
We show that spin-gravity interaction can distinguish between Dirac and
Majorana neutrino wave packets propagating in a Lense-Thirring background.
Using time-independent perturbation theory and gravitational phase to generate
a perturbation Hamiltonian with spin-gravity coupling, we show that the
associated matrix element for the Majorana neutrino differs significantly from
its Dirac counterpart. This difference can be demonstrated through significant
gravitational corrections to the neutrino oscillation length for a two-flavour
system, as shown explicitly for SN1987A.Comment: 4 pages, 2 figures; minor changes of text; typo corrected; accepted
in Physical Review Letter
Reply to Comment on ``Can gravity distinguish between Dirac and Majorana neutrinos?''
This is a reply to a comment (gr-qc/0610098) written by Nieves and Pal about
our paper (gr-qc/0605153) published in Phys. Rev. Lett. 97, 041101 (2006).Comment: 1 page, no figures, REVTe
Measurement of Adhesion of Sternal Wires to a Novel Bioactive Glass-Based Adhesive
Stainless steel wires are the standard method for sternal closure because of their strength and rigidity, the simplicity of the process, and the short healing time that results from their application. Despite this, problems still exist with sternal stability due to micromotion between the two halves of the dissected and wired sternum. Recently, a novel glass-based adhesive was developed which, in cadaveric trials and in conjunction with wiring, was shown to restrict this micromotion. However, in order to avoid complications during resternotomy, the adhesive should adhere only to the bone and not the sternal wire. In this study, sternal wires were embedded in 8 mm discs manufactured from the novel glass-based adhesive and the constructs were then incubated at 37 â—¦C for one, seven, and 30 days. The discs were manufactured in two different thicknesses: 2 and 3 mm. Wire pull-out tests were then performed on the constructs at three different strain rates (1, 0.1, and 0.01 mm/min). No statistically significant difference in pull-out force was found regardless of incubation time, loading rate, or construct thickness. The pull-out forces recorded were consistent with static friction between the wire and adhesive, rather than the adhesion between them. Scanning electron micrographs provided further proof of this. These results indicate that the novel adhesive may be suitable for sternal fixation without complicating a potential resternotomy
2-Increasing binary aggregation operators
In this work we investigate the class of binary aggregation operators (=agops) satisfying the 2-increasing property,
obtaining some characterizations for agops having other special properties (e.g., quasi-arithmetic mean, Choquet-integral
based, modularity) and presenting some construction methods. In particular, the notion of P-increasing function is used in
order to characterize the composition of 2-increasing agops. The lattice structure (with respect to the pointwise order) of
some subclasses of 2-increasing agops is presented. Finally, a method is given for constructing copulas beginning from 2-
increasing and 1-Lipschitz agops
Agent architecture for adaptive behaviours in autonomous driving
Evolution has endowed animals with outstanding adaptive behaviours which are grounded in the organization of their sensorimotor system. This paper uses inspiration from these principles of organization in the design of an artificial agent for autonomous driving. After distilling the relevant principles from biology, their functional role in the implementation of an artificial system are explained. The resulting Agent, developed in an EU H2020 Research and Innovation Action, is used to concretely demonstrate the emergence of adaptive behaviour with a significant level of autonomy. Guidelines to adapt the same principled organization of the sensorimotor system to other agents for driving are also obtained. The demonstration of the system abilities is given with example scenarios and open access simulation tools. Prospective developments concerning learning via mental imagery are finally discussed
Hardware in the loop simulation of a dielectric elastomer generator for oscillating water column wave energy converters
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