19,910 research outputs found
Weak Magnetism in Two Neutrino Double Beta Decay
We have extended the formalism for the two-neutrino double beta decay by
including the weak-magnetism term, as well as other second-forbidden
corrections. The weak magnetism diminishes the calculated half-lives in , independently of the nuclear structure. Numerical computations were
performed within the pn-QRPA, for , , ,
and nuclei. No one of the second-forbidden corrections modifies
significantly the spectrum shapes. The total reduction in the calculated half
lives varies from 6% up to 32%, and strongly depend on the nuclear interaction
in the particle-particle channel. We conclude that the higher order
effects in the weak Hamiltonian would hardly be observed in the two-neutrino
double beta experiments.Comment: 8 pages, latex, 1ps figure, to appear in Phys. Lett.
Solving the Constraints of General Relativity
I show in this letter that it is possible to solve some of the constraints of
the -ADM formalism for general relativity by using an approach similar
to the one introduced by Capovilla, Dell and Jacobson to solve the vector and
scalar constraints in the Ashtekar variables framework. I discuss the
advantages of using the ADM formalism and compare the result with similar
proposals for different Hamiltonian formulations of general relativity.Comment: 8 pages, LATEX, no figures, Preprint CGPG-94/11-
Systemic Design in Energy sector: theory and case studies
In the light of the growing concern about climate change, an important part of resource exploitation from industrial society is connected to energy use. Integration of companies through material and energy exchanges lead to a more efficient use of resources as well as financial, social and environmental benefits for the local entities involved, as Systemic Design approach proves. This research analyzes seven best-practices in Sweden, which since the Eighties realizes green energy plants, to understand key-drivers and barriers. Research coordinators can facilitate the creation of self-sustaining network of companie
On existential declarations of independence in IF Logic
We analyze the behaviour of declarations of independence between existential
quantifiers in quantifier prefixes of IF sentences; we give a syntactical
criterion for deciding whether a sentence beginning with such prefix exists
such that its truth values may be affected by removal of the declaration of
independence. We extend the result also to equilibrium semantics values for
undetermined IF sentences.
The main theorem allows us to describe the behaviour of various particular
classes of quantifier prefixes, and to prove as a remarkable corollary that all
existential IF sentences are equivalent to first-order sentences.
As a further consequence, we prove that the fragment of IF sentences with
knowledge memory has only first-order expressive power (up to truth
equivalence)
Theoretical interpretation of Warburg's impedance in electrolytic cells
We discuss the origin of Warburg's impedance in electrolytic cells containing
only one group of positive and one group of negative ions. Our analysis is
based on the Poisson-Nernst-Planck model, where the generation-recombination
phenomenon is neglected. We show that to observe Warburg's like impedance the
diffusion coefficient of the positive ions has to differen from that of the
negative one, and furthermore that the electrodes have to be not blocking. We
assume that the non-blocking properties of the electrodes can be described by
means of an Ohmic model, where the charge exchange between the cell and the
external circuit is described by means of an electrode conductivity. For
simplicity we consider a symmetric cell. However, our analysis can be easily
generalized to more complicated situations, where the cell is not symmetric and
the charge exchange is described by Chang-Jaffe model, or by a linearized
version of Butler-Volmer equation. Our analysis allows to justify the
expression for Warburg's impedance proposed previously by several groups, based
on wrong assumptions
Competition between standard and exotic double beta decays
We discuss the contributions of higher order terms in weak Hamiltonian to the
standard two-neutrino double beta decay. The formalism for the unique first
forbidden transitions has been developed, and it is shown that they can alter
the two-electron energy spectrum. Yet, their effect is too small to screen the
detection of exotic neutrinoless double beta decays, which are candidates for
testing the physics beyond the standard model.Comment: 9 pages, latex, 1ps figures, minor changes, to appear in Phys. Lett.
General Relativity as a Theory of Two Connections
We show in this paper that it is possible to formulate General Relativity in
a phase space coordinatized by two connections. We analyze first the
Husain-Kucha\v{r} model and find a two connection description for it.
Introducing a suitable scalar constraint in this phase space we get a
Hamiltonian formulation of gravity that is close to the Ashtekar one, from
which it is derived, but has some interesting features of its own. Among them a
possible mechanism for dealing with the degenerate metrics and a neat way of
writing the constraints of General Relativity.Comment: 18 pages, LATEX, Preprint CGPG-93/09-
Quadratic s-Form Field Actions with Semi-bounded Energy
We give in this paper a partial classification of the consistent quadratic
gauge actions that can be written in terms of s-form fields. This provides a
starting point to study the uniqueness of the Yang-Mills action as a
deformation of Maxwell-like theories. We also show that it is impossible to
write kinetic 1-form terms that can be consistently added to other 1-form
actions such as tetrad gravity in four space-time dimensions even in the
presence of a Minkowskian metric background.Comment: 1+35 papes in (DIN A4 format
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