4,798 research outputs found
Complete structure of Z_n Yukawa couplings
We give the complete twisted Yukawa couplings for all the Z_n orbifold
constructions in the most general case, i.e. when orbifold deformations are
considered. This includes a certain number of tasks. Namely, determination of
the allowed couplings, calculation of the explicit dependence of the Yukawa
couplings values on the moduli expectation values (i.e. the parameters
determining the size and shape of the compactified space), etc. The final
expressions are completely explicit, which allows a counting of the DIFFERENT
Yukawa couplings for each orbifold (with and without deformations). This
knowledge is crucial to determine the phenomenological viability of the
different schemes, since it is directly related to the fermion mass hierarchy.
Other facts concerning the phenomenological profile of Z_n orbifolds are also
discussed, e.g. the existence of non--diagonal entries in the fermion mass
matrices, which is related to a non--trivial structure of the
Kobayashi--Maskawa matrix. Finally some theoretical results are given, e.g. the
no--participation of (1,2) moduli in twisted Yukawa couplings. Likewise, (1,1)
moduli associated with fixed tori which are involved in the Yukawa coupling, do
not affect the value of the coupling.Comment: 60 page
Higgs Inflation as a Mirage
We discuss a simple unitarization of Higgs inflation that is genuinely weakly
coupled up to Planckian energies. A large non-minimal coupling between the
Higgs and the Ricci curvature is induced dynamically at intermediate energies,
as a simple ratio of mass scales. Despite not being dominated by the Higgs
field, inflationary dynamics simulates the `Higgs inflation' one would get by
blind extrapolation of the low-energy effective Lagrangian, at least
qualitatively. Hence, Higgs inflation arises as an approximate `mirage' picture
of the true dynamics. We further speculate on the generality of this phenomenon
and show that, if Higgs-inflation arises as an effective description, the
details of the UV completion are necessary to extract robust quantitative
predictions.Comment: 21 pages, 2 figure
Examining the Impact of Parental Involvement in a Dual Language Program: Implications for Children and Schools - OLLAS Report No. 2
This study focuses on a dual language (Spanish-English) program in the Omaha Public Schools. Dual language programs are programs in which children develop proficiency in two languages simultaneously. These programs are currently seen as the gold standard second language education because of the large amount of empirical support they have received with respect to children’s academic gains. All of the dual language classrooms are comprised of half native English speakers and half Spanish speakers.
Parental involvement has received much empirical attention with respect to traditional school programs; however, little is known about the role of parental involvement in dual language programs (Lindholm-Leary, 2001). Systematically studying dual language programs is an especially important area of investigation because of the latest census trends and because barriers to parental involvement for language minority children are likely to differ from those of language majority children.
For a list of additional publications produced from this project, please visit the Faculty Publications page on the OLLAS website
QLC relation and neutrino mass hierarchy
Latest measurements have revealed that the deviation from a maximal solar
mixing angle is approximately the Cabibbo angle, i.e. QLC relation. We argue
that it is not plausible that this deviation from maximality, be it a
coincidence or not, comes from the charged lepton mixing. Consequently we have
calculated the required corrections to the exactly bimaximal neutrino mass
matrix ansatz necessary to account for the solar mass difference and the solar
mixing angle. We point out that the relative size of these two corrections
depends strongly on the hierarchy case under consideration. We find that the
inverted hierarchy case with opposite CP parities, which is known to guarantee
the RGE stability of the solar mixing angle, offers the most plausible scenario
for a high energy origin of a QLC-corrected bimaximal neutrino mass matrix.
This possibility may allow us to explain the QLC relation in connection with
the origin of the charged fermion mass matrices.Comment: 7 pages, 0 figure
Bayesian approach and Naturalness in MSSM analyses for the LHC
The start of LHC has motivated an effort to determine the relative
probability of the different regions of the MSSM parameter space, taking into
account the present, theoretical and experimental, wisdom about the model.
Since the present experimental data are not powerful enough to select a small
region of the MSSM parameter space, the choice of a judicious prior probability
for the parameters becomes most relevant. Previous studies have proposed
theoretical priors that incorporate some (conventional) measure of the
fine-tuning, to penalize unnatural possibilities. However, we show that such
penalization arises from the Bayesian analysis itself (with no ad hoc
assumptions), upon the marginalization of the mu-parameter. Furthermore the
resulting effective prior contains precisely the Barbieri-Giudice measure,
which is very satisfactory. On the other hand we carry on a rigorous treatment
of the Yukawa couplings, showing in particular that the usual practice of
taking the Yukawas "as required", approximately corresponds to taking
logarithmically flat priors in the Yukawa couplings. Finally, we use an
efficient set of variables to scan the MSSM parameter space, trading in
particular B by tan beta, giving the effective prior in the new parameters.
Beside the numerical results, we give accurate analytic expressions for the
effective priors in all cases. Whatever experimental information one may use in
the future, it is to be weighted by the Bayesian factors worked out here.Comment: LaTeX, 19 pages, 3 figure
Reducing the Learning Domain by Using Image Processing to Diagnose COVID-19 from X-Ray Image
Over the last months, dozens of artificial intelligence (AI) solutions for COVID-19 diagnosis based on chest X-ray image analysis have been proposed. All of them with very impressive sensitivity and specificity results. However, its generalization and translation to the clinical practice are rather challenging due to the discrepancies between domain distributions when training and test data come from different sources. Consequently, applying a trained model on a new data set may have a problem with domain adaptation leading to performance degradation. This research aims to study the impact of image pre-processing on pre-trained deep learning models to reduce the learning domain. The dataset used in this research consists of 5,000 X-ray images obtained from different sources under two categories: negative and positive COVID-19 detection. We implemented transfer learning in 3 popular convolutional neural networks (CNNs), including VGG16, VGG19, and DenseNet169. We repeated the study following the same structure for original and pre-processed images. The pre-processing method is based on the Contrast Limited Adaptive Histogram Equalization (CLAHE) filter application and image registration. After evaluating the models, the CNNs that have been trained with pre-processed images obtained an accuracy score up to 1.2% better than the unprocessed ones. Furthermore, we can observe that in the 3 CNN models, the repeated misclassified images represent 40.9% (207/506) of the original image dataset with the erroneous result. In pre-processed ones, this percentage is 48.9% (249/509). In conclusion, image processing techniques can help to reduce the learning domain for deep learning applications
Neutron Irradiation Tests of Calibrated Cryogenic Sensors at Low Temperatures
This paper presents the advancement of a program being carried out in view of selecting the cryogenic temperature sensors to be used in the LHC accelerator. About 10,000 sensors will be installed around the 26.6 km LHC ring, and most of them will be exposed to high radiation doses during the accelerator lifetime. The following thermometric sensors : carbon resistors, thin films, and platinum resistors, have been exposed to high neutron fluences (>10 n/cm) at the ISN (Grenoble, France) Cryogenic Irradiation Test Facility. A cryostat is placed in a shielded irradiation vault where a 20 MeV deuteron beam hits a Be target, resulting in a well collimated and intense neutron beam. The cryostat, the on-line acquisition system, the temperature references and the main characteristics of the irradiation facility are described. The main interest of this set-up is its ability to monitor online the evolution of the sensors by comparing its readout with temperature references that are in principle insensitive to the neutron radiation (i.e. Argon gas bulbs when working at about 84 K, and below 4.5 K, either helium gas bulbs or the saturation pressure of the superfluid helium bath). The resistance shifts of the different sensors at liquid helium temperatures are presented
Neutron Irradiation Tests in Superfluid Helium of LHC Cryogenic Thermometers
For control and monitoring purposes, about 10,000 individually calibrated cryogenic temperature sensors will be installed along the 26.7 km LHC. In order to reduce maintenance constraints these sensor s should be as immune as possible to the high neutron fluence environment. For selecting the sensor to be used, a radiation hardness evaluation program at cryogenic conditions is being performed in an irradiation vault of the ISN SARA Cyclotron (Grenoble, France). The set-up is capable of simulating the whole life of a LHC thermometer: same total neutron dose (1015 n.cm-2), irradiation at low tempe rature (1.8 K) and thermal cycles. Bath temperature and sensor resistance are monitored on-line. This paper presents the latest results of this program
Stability of Neutrino Mass Degeneracy
Two neutrinos of Majorana masses with mixing angle are
unstable against radiative corrections in the limit , but are stable
for (i.e. opposite CP eigenstates) with which
corresponds to an additional symmetry.Comment: 7 pages, no figure, one reference adde
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