724 research outputs found
Generation and Life Cycle of Solar Spicules
Physical mechanism for the creation of solar spicules with three stages of
their life cycle is investigated. It is assumed that at stage-I, the density
hump is formed locally in the chromosphere in the presence of temperature
gradients of electrons and ions along the z-axis. The density structure is
accelerated in the vertical direction due to the thermal force . The magnitude of the
upward acceleration depends on the steepness of the temperature gradients
where . The exact time-dependent 2D analytical solution
of two fluid plasma equations is presented assuming that the exponentially
decaying density structure is created in the xy plane and evolves in time as a
step function . The upward acceleration produced in this density
structure is greater than the downward solar acceleration . The
vertical plasma velocity turns out to be the ramp function of time
whereas the source term for the density follows the delta function .
In the transition region (TR), the temperature gradients are steeper and
itupward acceleration increases in magnitude and density hump
spends lesser time here. This is stage-II of its life cycle. In stage-III, the
density structure enters the corona where the gradients of temperatures vanish
and structure moves upward with almost constant speed which is slowly reduced
to zero due to negative solar gravitational force because . The estimates of height and life time of the
spicule are in agreement with the observed values.Comment: 22 pages, 3 fig
Entanglement entropy of subtracted geometry black holes
We compute the entanglement entropy of minimally coupled scalar fields on
subtracted geometry black hole backgrounds, focusing on the logarithmic
corrections. We notice that matching between the entanglement entropy of
original black holes and their subtracted counterparts is only at the order of
the area term. The logarithmic correction term is not only different but also,
in general, changes sign in the subtracted case. We apply Harrison
transformations to the original black holes and find out the choice of the
Harrison parameters for which the logarithmic corrections vanish.Comment: 15 page
Optimal time for sensing in open quantum systems
We study the time-dependent quantum Fisher information (QFI) in an open
quantum system satisfying the Gorini-Kossakowski-Sudarshan-Lindblad master
equation. We also study the dynamics of the system from an effective
non-Hermitian dynamics standpoint and use it to understand the scaling of the
QFI when multiple probes are used. A focus of our work is how the QFI is
maximized at certain times suggesting that the best precision in parameter
estimation can be achieved by focusing on these times. The propagation of
errors analysis allows us to confirm and better understand this idea. We also
propose a parameter estimation procedure involving relatively low resource
consuming measurements followed by higher resource consuming measurements and
demonstrate it in simulation.Comment: 11 pages,8 Figure
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