2,043 research outputs found
Stable self similar blow up dynamics for slightly L^2 supercritical NLS equations
We consider the focusing nonlinear Schr\"odinger equations in dimension and for slightly
supercritical nonlinearities p_c
with and 0<\e\ll 1. We prove the existence and stability in the energy space of a self similar finite time blow up dynamics and provide a qualitative description of the singularity formation near the blow up tim
General Conditions for Lepton Flavour Violation at Tree- and 1-Loop Level
In this work, we compile the necessary and sufficient conditions a theory has
to fulfill in order to ensure general lepton flavour conservation, in the
spirit of the Glashow-Weinberg criteria for the absence of flavour-changing
neutral currents. At tree-level, interactions involving electrically neutral
and doubly charged bosons are investigated. We also investigate flavour changes
at 1-loop level. In all cases we find that the essential theoretical
requirements can be reduced to a few basic conditions on the particle content
and the coupling matrices. For 1-loop diagrams, we also investigate how exactly
a GIM-suppression can occur that will strongly reduce the rates of lepton
flavour violating effects even if they are in principle present in a certain
theory. In all chapters, we apply our criteria to several models which can in
general induce lepton flavour violation, e.g. LR-symmetric models or the MSSM.
In the end we give a summarizing table of the obtained results, thereby
demonstrating the applicability of our criteria to a large class of models
beyond the Standard Model.Comment: 31 pages, 2 figure
Spectroscopic binaries among AGB stars from HERMES/Mercator: the case of V Hya
We report on our search for spectroscopic binaries among a sample of AGB
stars. Observations were carried out in the framework of the monitoring of
radial velocities of (candidate) binary stars performed at the Mercator 1.2m
telescope, using the HERMES spectrograph. We found evidence for duplicity in UV
Cam, TU Tau, BL Ori, VZ Per, T Dra, and V Hya. This short communication focus
on V Hya, found to behave like RV Tau of the b subtype, which are binaries
surrounded by a disc.Comment: Poster presented at IAU Symp. 343 "Why Galaxies Care About AGB
Stars", Vienna, august 201
Potassium: a new actor on the globular cluster chemical evolution stage. The case of NGC 2808
We derive [K/Fe] abundance ratios for 119 stars in the globular cluster NGC
2808, all of them having O, Na, Mg and Al abundances homogeneously measured in
previous works. We detect an intrinsic star-to-star spread in the Potassium
abundance. Moreover [K/Fe] abundance ratios display statistically significant
correlations with [Na/Fe] and [Al/Fe], and anti-correlations with [O/Fe] and
[Mg/Fe]. All the four Mg deficient stars ([Mg/Fe]<0.0) discovered so far in NGC
2808 are enriched in K by ~0.3 dex with respect to those with normal [Mg/Fe].
NGC 2808 is the second globular cluster, after NGC 2419, where a clear Mg-K
anti-correlation is detected, albeit of weaker amplitude. The simultaneous
correlation/anti-correlation of [K/Fe] with all the light elements usually
involved in the chemical anomalies observed in globular cluster stars, strongly
support the idea that these abundance patterns are due to the same
self-enrichment mechanism that produces Na-O and Mg-Al anti-correlations. This
finding suggests that detectable spreads in K abundances may be typical in the
massive globular clusters where the self-enrichment processes are observed to
produce their most extreme manifestations.Comment: Accepted for publication by ApJ, 5 pages, 3 figure
Renormalization and blow up for charge one equivariant critical wave maps
We prove the existence of equivariant finite time blow up solutions for the
wave map problem from 2+1 dimensions into the 2-sphere. These solutions are the
sum of a dynamically rescaled ground-state harmonic map plus a radiation term.
The local energy of the latter tends to zero as time approaches blow up time.
This is accomplished by first "renormalizing" the rescaled ground state
harmonic map profile by solving an elliptic equation, followed by a
perturbative analysis
Improved Limit on theta_{13} and Implications for Neutrino Masses in Neutrino-less Double Beta Decay and Cosmology
We analyze the impact of a measurement, or of an improved bound, on
theta_{13} for the determination of the effective neutrino mass in
neutrino-less double beta decay and cosmology. In particular, we discuss how an
improved limit on (or a specific value of) theta_{13} can influence the
determination of the neutrino mass spectrum via neutrino-less double beta
decay. We also discuss the interplay with improved cosmological neutrino mass
searches.Comment: 22 pages, 5 figures. Minor corrections, matches version in PR
Stable self-similar blow-up dynamics for slightly -supercritical generalized KdV equations
In this paper we consider the slightly -supercritical gKdV equations
, with the nonlinearity
and . We will prove the existence and
stability of a blow-up dynamic with self-similar blow-up rate in the energy
space and give a specific description of the formation of the singularity
near the blow-up time.Comment: 38 page
Soft L_e-L_mu-L_tau flavour symmetry breaking and sterile neutrino keV Dark Matter
We discuss how a flavour symmetry that is softly broken
leads to keV sterile neutrinos, which are a prime candidate for Warm Dark
Matter. This is to our knowledge the first model where flavour symmetries are
applied simultaneously to active and sterile neutrinos explaining at the same
time active neutrino properties and this peculiar Dark Matter scenario. The
essential point is that different scales of the symmetry breaking and the
symmetry preserving entries in the mass matrix lead to one right-handed
neutrino which is nearly massless compared to the other two. Furthermore, we
naturally predict vanishing and maximal , while the
correct value of must come from the mixing of the charged
leptons. We can furthermore predict an exact mass spectrum for the light
neutrinos, which will be testable in the very near future.Comment: 14 page
A Study of a Fused Course in Physics and Chemistry for Watertown High School
The writers had in mind the modification of the present science curriculum in the Watertown High School. In doing this, they sought the answers to the following questions: Can physics and chemistry be fused into a one-year course for pupils who do not enroll in the conventional physics and chemistry classes? Will such a course be feasible and workable? What content will be included? How will it be taught? How will the laboratory work be handled? Can it be adapted to the interests and ability levels of the pupils? Will the achievement of the pupils in this fused course be comparable to the achievement of the pupils in the other physical science courses? In attempting to find the answers to· these questions, a review of the work which had already been done along the line of fusing physics and chemistry was made. Objectives for science teaching in high school were sought. An outline of content for the fused physics and chemistry course was developed and revised. The course was taught by the writers, each having a section, for a period of one year, and the achievement of the pupils in the fused course compared to those in the conventional physics and chemistry classes. The detailed procedure for these are to be found in the following sections of this study
- …