1,973 research outputs found
Determining the Neutrino Mass Hierarchy and CP Violation in NOvA with a Second Off-Axis Detector
We consider a Super-NOvA-like experimental configuration based on the use of
two detectors in a long-baseline experiment as NOvA. We take the far detector
as in the present NOvA proposal and add a second detector at a shorter
baseline. The location of the second off-axis detector is chosen such that the
ratio L/E is the same for both detectors, being L the baseline and E the
neutrino energy. We consider liquid argon and water-Cherenkov techniques for
the second off-axis detector and study, for different experimental setups, the
detector mass required for the determination of the neutrino mass hierarchy,
for different values of theta13. We also study the capabilities of such an
experimental setup for determining CP violation in the neutrino sector. Our
results show that by adding a second off-axis detector a remarkable enhancement
on the capabilities of the current NOvA experiment could be achieved.Comment: 20 p
Magnetic fields in circumstellar envelopes of evolved AGB stars
In this paper, a time-dependent magnetohydrodynamic model is presented which aimed at understanding the superwind production by an evolved AGB star and the consecutive formation of a dense circumstellar envelope around it. We know henceforth from various observations that a large scale magnetic field, probably toroidal in shape, is duly attested within these envelopes. Where does this large scale coherent field come from ? The apparent antinomy between the quasi-round dense circumstellar envelopes and their likely descendants, i.e. the elongated or bipolar Planetary Nebulae is also questioned. How is the spherical symmetry broken ? We suggest in the present model that the nebula must effectively appear round during the superwind phase from the point of view of a distant observer. By contrast anisotropic structures are already appearing at the same time, but these ones remain hidden in the innermost regions. We predict thus the existence of a large bipolar cavity above the AGB star during the slow superwind phase. We then conjecture that the PPNe phase begins when the fast wind emitted by the core engulfs this cavity and increases the anisotropy of the distribution of gas. Thus even though paradoxically enough a beautiful evolved PNe can eventually emerge from a quasi-round dense circumstellar envelope
How BAO measurements can fail to detect quintessence
We model the nonlinear growth of cosmic structure in different dark energy
models, using large volume N-body simulations. We consider a range of
quintessence models which feature both rapidly and slowly varying dark energy
equations of state, and compare the growth of structure to that in a universe
with a cosmological constant. The adoption of a quintessence model changes the
expansion history of the universe, the form of the linear theory power spectrum
and can alter key observables, such as the horizon scale and the distance to
last scattering. The difference in structure formation can be explained to
first order by the difference in growth factor at a given epoch; this scaling
also accounts for the nonlinear growth at the 15% level. We find that
quintessence models which feature late , rapid transitions towards
in the equation of state, can have identical baryonic acoustic
oscillation (BAO) peak positions to those in CDM, despite being very
different from CDM both today and at high redshifts .
We find that a second class of models which feature non-negligible amounts of
dark energy at early times cannot be distinguished from CDM using
measurements of the mass function or the BAO. These results highlight the need
to accurately model quintessence dark energy in N-body simulations when testing
cosmological probes of dynamical dark energy.Comment: 10 pages, 7 figures, to appear in the Invisible Univers International
Conference AIP proceedings serie
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