55 research outputs found
Electron-, Mu-, and Tau-Number Conservation in a Supernova Core
We study if the neutrino mixing parameters suggested by the atmospheric
neutrino anomaly imply chemical equilibrium between mu- and tau-flavored
leptons in a supernova (SN) core. The initial flavor-conversion rate would
indeed be fast if the nu_mu-nu_tau-mixing angle were not suppressed by
second-order refractive effects. The neutrino diffusion coefficients are
different for nu_mu, anti-nu_mu, nu_tau and anti-nu_tau so that neutrino
transport will create a net mu and tau lepton number density. This will
typically lead to a situation where the usual first-order refractive effects
dominate, further suppressing the rate of flavor conversion. Altogether,
neutrino refraction has the nontrivial consequence of guaranteeing the separate
conservation of e, mu, and tau lepton number in a SN core on the infall and
cooling time scales, even when neutrino mixing angles are large.Comment: Slightly expanded version with improved presentation, no changes of
substanc
O(4) texture with a cosmological constant
We investigate O(4) textures in a background with a positive cosmological
constant. We find static solutions which co-move with the expanding background.
There exists a solution in which the scalar field is regular at the horizon.
This solution has a noninteger winding number smaller than one. There also
exist solutions in which scalar-field derivatives are singular at the horizon.
Such solutions can complete one winding within the horizon. If the winding
number is larger than some critical value, static solutions including the
regular one are unstable under perturbations.Comment: 25 pages, revtex, 6 eps figure
Spin-Flavour Oscillations and Neutrinos from SN1987A
The neutrino signal from SN1987A is analysed with respect to spin-flavour
oscillations between electron antineutrinos, , and muon
neutrinos, , by means of a maximum likelihood analysis.
Following Jegerlehner et al. best fit values for the total energy released in
neutrinos, , and the temperature of the electron antineutrino,
, for a range of mixing parameters and progenitor models are
calculated. In particular the dependence of the inferred quantities on the
metallicity of the supernova is investigated and the uncertainties involved in
using the neutrino signal to determine the neutrino magnetic moment are pointed
out.Comment: 14 pages, RevTeX, 4 figures, to appear in Physical Review
Brane world in a texture
We study five dimensional brane physics induced by an O(2) texture formed in
one extra dimension. The model contains two 3-branes of nonzero tension, and
the extra dimension is compact. The symmetry-breaking scale of the texture
controls the particle hierarchy between the two branes. The TeV-scale particles
are confined to the negative-tension brane where the observer sees gravity as
essentially four dimensional. The effect of massive Kaluza-Klein gravitons is
suppressed.Comment: 25 pages, revtex, 5 eps figures, Significant changes have been made
for the tachyonic mode, One figure has been replaced, To appear in Physical
Review
Neutrino Oscillations and the Supernova 1987A Signal
We study the impact of neutrino oscillations on the interpretation of the
supernova (SN) 1987A neutrino signal by means of a maximum-likelihood analysis.
We focus on oscillations between with or
with those mixing parameters that would solve the solar
neutrino problem. For the small-angle MSW solution (, ), there are no
significant oscillation effects on the Kelvin-Helmholtz cooling signal; we
confirm previous best-fit values for the neutron-star binding energy and
average spectral temperature. There is only marginal overlap
between the upper end of the 95.4\% CL inferred range of and the lower end of the range of theoretical
predictions. Any admixture of the stiffer spectrum by
oscillations aggravates the conflict between experimentally inferred and
theoretically predicted spectral properties. For mixing parameters in the
neighborhood of the large-angle MSW solution (, ) the oscillations in the SN are adiabatic,
but one needs to include the regeneration effect in the Earth which causes the
Kamiokande and IMB detectors to observe different spectra. For
the solar vacuum solution (,
) the oscillations in the SN are nonadiabatic; vacuum
oscillations take place between the SN and the detector. If either of the
large-angle solutions were borne out by the upcoming round of solar neutrino
experiments, one would have to conclude that the SN~1987A
and/or spectra had been much softer than predicted by currentComment: Final version with very minor wording changes, to be published in
Phys. Rev.
STUDI KROMOSOM TANAMAN MATA KUCING (Dimocarpus malesianus Leenh.) DALAM UPAYA PENINGKATAN KUALITAS BUAH
Tanaman mata kucing (Dimocarpus malesianus) merupakan tanaman
yang dimanfaatkan buahnya. Buah tersebut memiliki rasa yang manis, biasanya
dimakan dalam keadaan segar. Ketika musim berbuah, buah mata kucing
diperdagangkan di wilayah Pulau Kalimantan. Nama mata kucing digunakan
karena isi buah dan bijinya mirip dengan mata kucing yang bersinar.
Pustaka yang ada, belum ada penelitian yang melaporkan jumlah
kromosom dan susunan genetik tentang tanaman mata kucing secara akurat.
Pengetahuan tentang informasi genetik tanaman mata kucing sebagai usaha
perbaikan kualitas tanaman tersebut melalui kegiatan pemuliaan. Studi kromosom
tanaman mata kucing merupakan aspek penting yang dapat berkontribusi sebagai
dasar pemuliaan tanaman tersebut.
Penelitian ini dilaksanakan di Laboratorium Fisiologi dan Bioteknologi
Tanaman Fakultas Pertanian Universitas Sebelas Maret Surakarta mulai Mei 2010
sampai dengan Maret 2011. Penelitian ini menggunakan metode squashing,
dengan pra-perlakuan aquades selama ± 24 jam dalam referigator 50
C, fiksasi
dengan larutan asam asetat 45 % dalam suhu ruang selama ± 1 jam, dan hidrolisis
menggunakan HCl 1N dalam suhu ruang selama ± 5 menit, serta pewarnaan
dalam larutan aceto orcein 2% selama 24 jam dalam suhu referigator 50
C.
Pengamatan dilakukan dengan mikroskop cahaya terhadap sejumlah sel-sel yang
menunjukkan penyebaran kromosom secara baik, difoto serta dibua
Stability of inflating branes in a texture
We investigate the stability of inflating branes embedded in an O(2) texture
formed in one extra dimension. The model contains two 3-branes of nonzero
tension, and the extra dimension is compact. When the gravitational
perturbation is applied, the vacuum energy which is responsible for inflation
on the branes stabilizes the branes if the symmetry-breaking scale of the
texture is smaller than some critical value. This critical value is determined
by the particle-hierarchy scale between the two branes, and is smaller than the
5D Planck-mass scale. The scale of the vacuum energy can be considerably low in
providing the stability. This stability story is very different from the
flat-brane case which always suffers from the instability due to the
gravitational perturbation.Comment: 16 pages, 5 eps figures, revte
Chaotic Amplification of Neutrino Chemical Potentials by Neutrino Oscillations in Big Bang Nucleosynthesis
We investigate in detail the parameter space of active-sterile neutrino
oscillations that amplifies neutrino chemical potentials at the epoch of Big
Bang Nucleosynthesis. We calculate the magnitude of the amplification and show
evidences of chaos in the amplification process. We also discuss the
implications of the neutrino chemical potential amplification in the Big Bang
Nucleosynthesis. It is shown that with a eV \nue, the amplification
of its chemical potential by active-sterile neutrino oscillations can lower the
effective number of neutrino species at Big Bang Nucleosynthesis to
significantly below 3.Comment: Revtex 20 pages, 7 postscript figures. Also by
ftp://astro.queensu.ca/pub/shi/ . Submitted to PR
Neutrino propagation in a random magnetic field
The active-sterile neutrino conversion probability is calculated for neutrino
propagating in a medium in the presence of random magnetic field fluctuations.
Necessary condition for the probability to be positive definite is obtained.
Using this necessary condition we put constraint on the neutrino magnetic
moment from active-sterile electron neutrino conversion in the early universe
hot plasma and in supernova.Comment: 11 page
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