30,647 research outputs found
The New SI and the Fundamental Constants of Nature
The launch in 2019 of the new international system of units is an opportunity
to highlight the key role that the fundamental laws of physics and chemistry
play in our lives and in all the processes of basic research, industry and
commerce. The main objective of these notes is to present the new SI in an
accessible way for a wide audience. After reviewing the fundamental constants
of nature and its universal laws, the new definitions of SI units are presented
using, as a unifying principle, the discrete nature of energy, matter and
information in these universal laws. The new SI system is here to stay:
although the experimental realizations may change due to technological
improvements, the definitions will remain unaffected. Quantum metrology is
expected to be one of the driving forces to achieve new quantum technologies of
the second generation.
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La puesta en marcha en 2019 del nuevo sistema internacional de unidades es
una oportunidad para resaltar el papel fundamental que las leyes fundamentales
de la F\'{\i}sica y la Qu\'{\i}mica juegan en nuestra vida y en todos los
procesos de la investigaci\'on fundamental, la industria y el comercio. El
principal objetivo de estas notas es presentar el nuevo SI de forma accesible
para una audiencia amplia. Tras repasar las constantes fundamentales de la
naturaleza y sus leyes universales, se presentan las nuevas definiciones de las
unidades SI utilizando como principio unificador la naturaleza discreta de la
energ\'{\i}a, la materia y la informaci\'on en esas leyes universales. El nuevo
sistema SI tiene vocaci\'on de futuro: aunque las realizaciones experimentales
cambien por mejoras tecnol\'gicas, las definiciones permanecer\'an inalteradas.
La Metrolog\'{\i}a cu\'antica est\'a llamada a ser uno de las fuerzas motrices
para conseguir nuevas tecnolog\'{\i}as cu\'anticas de segunda generaci\'on.Comment: Revtex file, color figures. English version y en espa\~no
Electroweak and Flavor Physics in Extensions of the Standard Model with Large Extra Dimensions
We study the implications of extra dimensions of size on
electroweak and flavor physics due to the presence of Kaluza-Klein excitations
of the SM gauge-bosons. We consider several scenarios with the SM fermions
either living in the bulk or being localized at different points of an extra
dimension. Global fits to electroweak observables provide lower bounds on 1/R,
which are generically in the 2-5 TeV range. We find, however, certain models
where the fit to electroweak observables is better than in the SM, because of
an improvement in the prediction to the weak charge Q_W. We also consider the
case of softly-broken supersymmetric theories and we find new non-decoupling
effects that put new constraints on 1/R. If quarks of different families live
in different points of the extra dimension, we find that the Kaluza-Klein modes
of the SM gluons generate (at tree level) dangerous flavor and CP-violating
interactions. The lower bounds on 1/R can increase in this case up to 5000 TeV,
disfavoring these scenarios in the context of TeV-strings.Comment: 21 pages, 3 figures, Late
A consistent test of significance
This paper presents a test of significance consistent under nonparametric alternatives. Under the null hypothesis, a regressor has no effect on the regression model. Our statistic does not require to estimate the model on the alternative hypothesis, which is left unspecified. Hence, no smoothing techniques are required. The statistic is a weighted empirical process which resembles the Cram~r-von Mises. The asymptotic test is consistent under Pitman's alternatives converging to the null at arate n-1/2. A Monte-Cario experiment illustrates the performance ofthe test in small samples. We also inelude two applications involving biomedical and acid rain data
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