6,961 research outputs found
Identifying Earth matter effects on supernova neutrinos at a single detector
The neutrino oscillations in Earth matter introduce modulations in the
supernova neutrino spectra. These modulations can be exploited to identify the
presence of Earth effects on the spectra, which would enable us to put a limit
on the value of the neutrino mixing angle and to identify whether
the mass hierarchy is normal or inverted. We demonstrate how the Earth effects
can be identified at a single detector without prior assumptions about the
flavor-dependent source spectra, using the Fourier transform of the
``inverse-energy'' spectrum of the signal. We explore the factors affecting the
efficiency of this method, and find that the energy resolution of the detector
is the most crucial one. In particular, whereas water Cherenkov detectors may
need a few ten thousand events to identify the Earth effects, a few thousand
may be enough at scintillation detectors, which generically have a much better
energy resolution. A successful identification of the Earth effects through
this method can also provide to a good accuracy. The
relative strength of the detected Earth effects as a function of time provides
a test for supernova models.Comment: 18 pages, 10 figures, JCAP format. Final version to be published in
JCAP. References and some minor clarifications added to the original versio
Supernova neutrinos: Flavor-dependent fluxes and spectra
Transporting nu_mu and nu_tau in a supernova (SN) core involves several
processes that have been neglected in traditional simulations. Based on a Monte
Carlo study we find that the flavor-dependent spectral differences are much
smaller than is often stated in the literature. A full-scale SN simulation
using a Boltzmann solver and including all relevant neutrino reactions confirms
these results. The flavor-dependent flux differences are largest during the
initial accretion phase.Comment: Proceedings NOON 03, Kanazawa, 10-14 Feb 200
Supernova Neutrino Opacity from Nucleon-Nucleon Bremsstrahlung and Related Processes
Elastic scattering on nucleons, \nu N -> N \nu, is the dominant supernova
(SN) opacity source for \mu and \tau neutrinos. The dominant energy- and
number-changing processes were thought to be \nu e^- -> e^- \nu and \nu\bar \nu
e^+ e^- until Suzuki (1993) showed that the bremsstrahlung process \nu\bar
\nu NN NN was actually more important. We find that for energy exchange,
the related ``inelastic scattering process'' \nu NN NN \nu is even more
effective by about a factor of 10. A simple estimate implies that the \nu_\mu
and \nu_\tau spectra emitted during the Kelvin-Helmholtz cooling phase are much
closer to that of \nu\bar_e than had been thought previously. To facilitate a
numerical study of the spectra formation we derive a scattering kernel which
governs both bremsstrahlung and inelastic scattering and give an analytic
approximation formula. We consider only neutron-neutron interactions, we use a
one-pion exchange potential in Born approximation, nonrelativistic neutrons,
and the long-wavelength limit, simplifications which appear justified for the
surface layers of a SN core. We include the pion mass in the potential and we
allow for an arbitrary degree of neutron degeneracy. Our treatment does not
include the neutron-proton process and does not include nucleon-nucleon
correlations. Our perturbative approach applies only to the SN surface layers,
i.e. to densities below about 10^{14} g cm^{-3}.Comment: 36 pages, LaTeX, 6 postscript figs included, matches version accepted
for publication in Astrophysical Journa
Pinning control of fractional-order weighted complex networks
In this paper, we consider the pinning control problem of fractional-order weighted complex dynamical networks. The well-studied integer-order complex networks are the special cases of the fractional-order ones. The network model considered can represent both directed and undirected weighted networks. First, based on the eigenvalue analysis and fractional-order stability theory, some local stability properties of such pinned fractional-order networks are derived and the valid stability regions are estimated. A surprising finding is that the fractional-order complex networks can stabilize itself by reducing the fractional-order q without pinning any node. Second, numerical algorithms for fractional-order complex networks are introduced in detail. Finally, numerical simulations in scale-free complex networks are provided to show that the smaller fractional-order q, the larger control gain matrix D, the larger tunable weight parameter , the larger overall coupling strength c, the more capacity that the pinning scheme may possess to enhance the control performance of fractional-order complex networks
Deconfinement transition in protoneutron stars: analysis within the Nambu-Jona-Lasinio model
We study the effect of color superconductivity and neutrino trapping on the
deconfinement transition of hadronic matter into quark matter in a protoneutron
star. To describe the strongly interacting matter a two-phase picture is
adopted. For the hadronic phase we use different parameterizations of a
non-linear Walecka model which includes the whole baryon octet. For the quark
matter phase we use an Nambu-Jona-Lasinio effective model which
includes color superconductivity. We impose color and flavor conservation
during the transition in such a way that just deconfined quark matter is
transitorily out of equilibrium with respect to weak interactions. We find that
deconfinement is more difficult for small neutrino content and it is easier for
lower temperatures although these effects are not too large. In addition they
will tend to cancel each other as the protoneutron star cools and deleptonizes,
resulting a transition density that is roughly constant along the evolution of
the protoneutron star. According to these results the deconfinement transition
is favored after substantial cooling and contraction of the protoneutron star
Neutrino Signal of Electron-Capture Supernovae from Core Collapse to Cooling
An 8.8 solar mass electron-capture supernova (SN) was simulated in spherical
symmetry consistently from collapse through explosion to nearly complete
deleptonization of the forming neutron star. The evolution time of about 9 s is
short because of nucleon-nucleon correlations in the neutrino opacities. After
a brief phase of accretion-enhanced luminosities (~200 ms), luminosity
equipartition among all species becomes almost perfect and the spectra of
electron antineutrinos and muon/tau antineutrinos very similar. We discuss
consequences for the neutrino-driven wind as a nucleosynthesis site and for
flavor oscillations of SN neutrinos.Comment: 4 pages, 4 eps figures; published as Physical Review Letters, vol.
104, Issue 25, id. 25110
Effect of Muons on the Phase Transition in Magnetised Proto-Neutron Star Matter
We study the effect of inclusion of muons and the muon neutrinos on the phase
transition from nuclear to quark matter in a magnetised proto-neutron star and
compare our results with those obtained by us without the muons. We find that
the inclusion of muons changes slightly the nuclear density at which transition
occurs.However the dependence of this transition density on various chemical
potentials, temperature and the magnetic field remains quantitatively the same.Comment: LaTex2e file with four postscript figure
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