5,227 research outputs found
Constraints on a general 3-generation neutrino mass matrix from neutrino data: application to the MSSM with R-parity violation
We consider a general symmetric mass matrix for three
generations of neutrinos. Imposing the constraints, from the atmospheric
neutrino and solar neutrino anomalies as well as from the CHOOZ experiment, on
the mass squared differences and on the mixing angles, we identify the ranges
of allowed inputs for the 6 matrix elements. We apply our results to Majorana
left-handed neutrino masses generated at tree level and through
fermion--sfermion loop diagrams in the MSSM with R-parity violation. The
present experimental results on neutrinos from laboratories, cosmology and
astrophysics are implemented to either put bounds on trilinear () and bilinear
() R-parity-violating couplings or constrain combinations
of products of these couplings.Comment: 35 pages, 25 PS figures, REVTeX, revised version to appear in Nuclear
physics
Evolution of quantum observables: from non-commutativity to commutativity
A fundamental aspect of the quantum-to-classical limit is the transition from a non-
commutative algebra of observables to commutative one.However, this transition is not possible if we only consider unitary evolutions. One way to describe this transition is to consider the Gamow vectors, which introduce exponential decays in the evolution. In this paper, we give two mathematical models in which this transition happens in the infinite time limit. In the first one, we consider operators acting on the space of the Gamow vectors, which represent quantum resonances. In the second one, we use an algebraic formalism from scattering theory. We construct a non-commuting algebra which commutes in the infinite time limit.MINECO Grant MTM2014- 57129-C2-1-P. Junta de Castilla y Leon Grants BU229P18, VA137G18
Constraints on both bilinear and trilinear R-parity violating couplings from neutrino laboratories and astrophysics data
We consider neutrino masses generated at tree level and at one loop, through fermion--sfermion loop diagrams, in the MSSM with R-parity violation. Using the mass and mixing matrices for three generations of neutrinos and the present experimental results on neutrinos from laboratories and astrophysics simultaneously, we put bounds on both trilinear () and bilinear () R-parity-violating couplings
Management Roles in Political and Senior Civil Servant Positions: A Multiple-Study Approach
A recent trend in public administration studies has been to assess how public management is performed by politicians and top civil servants. Surprisingly, little is known about how these different posts develop their management roles. Following seminal management studies, we focus on core management roles to compare the ways in which politicians and top civil servants develop their management responsibilities within public organizations. Empirical evidence is provided by triangulating three separate studies developed in Spain. Results from the triangulation show that there is unmistakable evidence of differentiations between politicians and top civil servants when performing their managerial roles
Efficiency of Human Activity on Information Spreading on Twitter
Understanding the collective reaction to individual actions is key to
effectively spread information in social media. In this work we define
efficiency on Twitter, as the ratio between the emergent spreading process and
the activity employed by the user. We characterize this property by means of a
quantitative analysis of the structural and dynamical patterns emergent from
human interactions, and show it to be universal across several Twitter
conversations. We found that some influential users efficiently cause
remarkable collective reactions by each message sent, while the majority of
users must employ extremely larger efforts to reach similar effects. Next we
propose a model that reproduces the retweet cascades occurring on Twitter to
explain the emergent distribution of the user efficiency. The model shows that
the dynamical patterns of the conversations are strongly conditioned by the
topology of the underlying network. We conclude that the appearance of a small
fraction of extremely efficient users results from the heterogeneity of the
followers network and independently of the individual user behavior.Comment: 29 pages, 10 figure
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