1,977 research outputs found
A unified approach to suboptimum control
Suboptimal control based on linear changes in vicinity of optimum trajector
Design of a three-axis attitude control system for a spacecraft acted upon by random perturbations Final report
Three axis attitude control system for spacecraft under random perturbation
Stability of attitude control systems acted upon by random perturbations
Mathematical models on stability of attitude control systems acted upon by random perturbation processe
Stimulated Neutrino Transformation with Sinusoidal Density Profiles
Large amplitude oscillations between the states of a quantum system can be
stimulated by sinusoidal external potentials with frequencies that are similar
to the energy level splitting of the states or a fraction thereof. Situations
when the applied frequency is equal to an integer fraction of the energy level
splittings are known as parametric resonances. We investigate this effect for
neutrinos both analytically and numerically for the case of arbitrary numbers
of neutrino flavors. We look for environments where the effect may be observed
and find that supernova are the one realistic possibility due to the necessity
of both large densities and large amplitude fluctuations. The comparison of
numerical and analytic results of neutrino propagation through a model
supernova reveals it is possible to predict the locations and strengths of the
stimulated transitions that occur.Comment: 14 pages, 6 figure
Comprehensive track-structure based evaluation of DNA damage by light ions from radiotherapy- relevant energies down to stopping
Track structures and resulting DNA damage in human cells have been simulated for hydrogen, helium,
carbon, nitrogen, oxygen and neon ions with 0.25–256 MeV/u energy. The needed ion interaction cross sections have been scaled from those of hydrogen; Barkas scaling formula has been refined, extending its applicability down to about 10 keV/u, and validated against established stopping power data. Linear energy transfer (LET) has been scored from energy deposits in a cell nucleus; for very low-energy ions, it has been defined locally within thin slabs. The simulations show that protons and helium ions induce more DNA damage than heavier ions do at the same LET. With increasing LET, less DNA strand breaks are formed per unit dose, but due to their clustering the yields of double-strand breaks (DSB) increase, up to saturation around 300 keV/μm. Also individual DSB tend to cluster; DSB clusters peak around
500 keV/μm, while DSB multiplicities per cluster steadily increase with LET. Remarkably similar to patterns known from cell survival studies, LET-dependencies with pronounced maxima around 100– 200 keV/μm occur on nanometre scale for sites that contain one or more DSB, and on micrometre scale for megabasepair-sized DNA fragments
Testing matter effects in propagation of atmospheric and long-baseline neutrinos
We quantify our current knowledge of the size and flavor structure of the
matter effects in the evolution of atmospheric and long-baseline neutrinos
based solely on the analysis of the corresponding neutrino data. To this aim we
generalize the matter potential of the Standard Model by rescaling its
strength, rotating it away from the e-e sector, and rephasing it with respect
to the vacuum term. This phenomenological parametrization can be easily
translated in terms of non-standard neutrino interactions in matter. We show
that in the most general case, the strength of the potential cannot be
determined solely by atmospheric and long-baseline data. However its flavor
composition is very much constrained and the present determination of the
neutrino masses and mixing is robust under its presence. We also present an
update of the constraints arising from this analysis in the particular case in
which no potential is present in the e-mu and e-tau sectors. Finally we
quantify to what degree in this scenario it is possible to alleviate the
tension between the oscillation results for neutrinos and antineutrinos in the
MINOS experiment and show the relevance of the high energy part of the spectrum
measured at MINOS.Comment: PDFLaTeX file using JHEP3 class, 25 pages, 7 figures included.
Accepted for publication in JHE
Lower Bounds for Heights in Relative Galois Extensions
The goal of this paper is to obtain lower bounds on the height of an
algebraic number in a relative setting, extending previous work of Amoroso and
Masser. Specifically, in our first theorem we obtain an effective bound for the
height of an algebraic number when the base field is a
number field and is Galois. Our second result
establishes an explicit height bound for any non-zero element which is
not a root of unity in a Galois extension , depending on
the degree of and the number of conjugates of
which are multiplicatively independent over . As a consequence, we
obtain a height bound for such that is independent of the
multiplicative independence condition
Cosmological and Astrophysical Neutrino Mass Measurements
Cosmological and astrophysical measurements provide powerful constraints on
neutrino masses complementary to those from accelerators and reactors. Here we
provide a guide to these different probes, for each explaining its physical
basis, underlying assumptions, current and future reach.Comment: 11 page
Recommended from our members
Heritable genome editing in C. elegans via a CRISPR-Cas9 system
CRISPR-Cas systems have been used with single-guide RNAs for accurate gene disruption and conversion in multiple biological systems. Here we report the use of the endonuclease Cas9 to target genomic sequences in the C. elegans germline, utilizing single-guide RNAs that are expressed from a U6 small nuclear RNA promoter. Our results demonstrate that targeted, heritable genetic alterations can be achieved in C. elegans, providing a convenient and effective approach for generating loss-of-function mutants
Small bound for birational automorphism groups of algebraic varieties (with an Appendix by Yujiro Kawamata)
We give an effective upper bound of |Bir(X)| for the birational automorphism
group of an irregular n-fold (with n = 3) of general type in terms of the
volume V = V(X) under an ''albanese smoothness and simplicity'' condition. To
be precise, |Bir(X)| < d_3 V^{10}. An optimum linear bound |Bir(X)|-1 <
(1/3)(42)^3 V is obtained for those 3-folds with non-maximal albanese
dimension. For all n > 2, a bound |Bir(X)| < d_n V^{10} is obtained when alb_X
is generically finite, alb(X) is smooth and Alb(X) is simple.Comment: Mathematische Annalen, to appea
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