4,071 research outputs found
Self-gravitating system made of axions
We show that the inclusion of an axion-like effective potential in the
construction of a self-gravitating system made of scalar fields leads to a
decrease on its compactness when the value of the self-interaction coupling
constant is increased. By including the current values for the axion mass m and
decay constant f_a, we have computed the mass and the radius for
self-gravitating systems made of axion particles. It is found that such objects
will have asteroid-size masses and radius of few meters, then, the
self-gravitating system made of axions could play the role of scalar
mini-machos that are mimicking a cold dark matter model for the galactic halo.Comment: 5 pages, 3 figures. References added. Accepted for publication in
Physical Review
Probing nonstandard interactions with reactor neutrinos
New limits on the weak mixing angle and on the electron neutrino effective
charge radius in the low energy regime, below 100 MeV, are obtained from a
combined fit of all electron-(anti)neutrino electron elastic scattering
measurements. We have included the recent TEXONO measurement with a CsI (Tl)
detector. Only statistical error of this measurement has been taken into
account. Weak mixing angle is found to be sin^2 theta_W = 0.255 +0.022 -0.023.
The electron neutrino effective charge radius squared is bounded to be r^2 =
(0.9 +0.9 -1.0) x 10^{-32} cm^2. The sensitivity of future low energy neutrino
experiments to nonstandard interactions of neutrinos with quarks is also
discussed.Comment: 3 pages, 2 figures, talk given at the Neutrino Oscillation Workshop
(NOW 2008), Otranto, Italy, September 6-13, 2008. Misprints correcte
Constraining scalar field properties with boson stars as black hole mimickers
Constraints to the mass of a scalar field and the strength of its
self-interacting coupling constant are obtained. This was done using
observations of stellar dynamics at the center of our galaxy and by assuming
that the dark compact object responsible of such dynamics is a boson star and
not a supermassive black hole. We show that if such scalar field represents a
spin-zero particle with cross section high enough to be considered collisional
dark matter, there is a region of parameters compatible with both conditions:
that the scalar field play the role of collisional dark matter and that it can
form objects with the mass and compactness compatible with stellar kinematics.Comment: To appear in the Procceedings of the VIII Workshop of the Gravitation
and Mathematical Physics Division of the Mexican Physical Societ
Universal Mass Texture, CP violation and Quark-Lepton Complementarity
The measurements of the neutrino and quark mixing angles satisfy the
empirical relations called Quark-Lepton Complementarity. These empirical
relations suggest the existence of a correlation between the mixing matrices of
leptons and quarks. In this work, we examine the possibility that this
correlation between the mixing angles of quarks and leptons originates in the
similar hierarchy of quarks and charged lepton masses and the seesaw mechanism
type~I, that gives mass to the Majorana neutrinos. We assume that the similar
mass hierarchies of charged lepton and quark masses allows us to represent all
the mass matrices of Dirac fermions in terms of a universal form with four
texture zeroes.Comment: 14 page
Transfer of coherence from atoms to mixed field states in a two-photon lossless micromaser
We propose a two-photon micromaser-based scheme for the generation of a
nonclassical state from a mixed state. We conclude that a faster, as well as a
higher degree of field purity is achieved in comparison to one-photon
processes. We investigate the statistical properties of the resulting field
states, for initial thermal and (phase-diffused) coherent states.
Quasiprobabilities are employed to characterize the state of the generated
fields.Comment: 20 pages, 8 figures, to appear in Journal of Modern Optic
Improved limit on electron neutrino charge radius through a new evaluation of the weak mixing angle
We have obtained a new limit on the electron neutrino effective charge radius
from a new evaluation of the weak mixing angle by a combined fit of all
electron-(anti)neutrino electron elastic scattering measurements. Weak mixing
angle is found to be sin^2 theta_W=0.259 \pm 0.025 in the low energy regime
below 100 MeV. The electron neutrino charge radius squared is bounded to be in
the range -0.13 10^-32 cm^2 < r^2 < 3.32 10^-32 cm^2 at 90 % C.L. Both results
improve previously published analyses. We also discuss perspectives of future
experiments to improve these constraints.Comment: 10 pages, 2 figures. Final published versio
Improved Contrast Sensitivity DVS and its Application to Event-Driven Stereo Vision
This paper presents a new DVS sensor with
one order of magnitude improved contrast sensitivity over
previous reported DVSs. This sensor has been applied to a
bio-inspired event-based binocular system that performs
3D event-driven reconstruction of a scene. Events from two
DVS sensors are matched by using precise timing
information of their ocurrence. To improve matching
reliability, satisfaction of epipolar geometry constraint is
required, and simultaneously available information on the
orientation is used as an additional matching constraint.Ministerio de Economía y Competitividad PRI-PIMCHI-2011-0768Ministerio de Economía y Competitividad TEC2009-10639-C04-01Junta de Andalucía TIC-609
- …