18,124 research outputs found
On the frequency of N2H+ and N2D+
Context : Dynamical studies of prestellar cores search for small velocity
differences between different tracers. The highest radiation frequency
precision is therefore required for each of these species. Aims : We want to
adjust the frequency of the first three rotational transitions of N2H+ and N2D+
and extrapolate to the next three transitions. Methods : N2H+ and N2D+ are
compared to NH3 the frequency of which is more accurately known and which has
the advantage to be spatially coexistent with N2H+ and N2D+ in dark cloud
cores. With lines among the narrowests, and N2H+ and NH3 emitting region among
the largests, L183 is a good candidate to compare these species. Results : A
correction of ~10 kHz for the N2H+ (J:1-0) transition has been found (~0.03
km/s) and similar corrections, from a few m/s up to ~0.05 km/s are reported for
the other transitions (N2H+ J:3-2 and N2D+ J:1-0, J:2-1, and J:3-2) compared to
previous astronomical determinations. Einstein spontaneous decay coefficients
(Aul) are included
The orbifold cohomology of moduli of hyperelliptic curves
We study the inertia stack of [M_{0,n}/S_n], the quotient stack of the moduli
space of smooth genus 0 curves with n marked points via the action of the
symmetric group S_n. Then we see how from this analysis we can obtain a
description of the inertia stack of H_g, the moduli stack of hyperelliptic
curves of genus g. From this, we can compute additively the Chen-Ruan (or
orbifold) cohomology of H_g.Comment: 15 pages. We correct an error in Proposition 3.3 of the published
paper, and its consequence
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