1,035 research outputs found
Dominance of gauge artifact in the consistency relation for the primordial bispectrum
The conventional cosmological perturbation theory has been performed under
the assumption that we know the whole spatial region of the universe with
infinite volume. This is, however, not the case in the actual observations
because observable portion of the universe is limited. To give a theoretical
prediction to the observable fluctuations, gauge-invariant observables should
be composed of the information in our local observable universe with finite
volume. From this point of view, we reexamine the primordial non-Gaussianity in
single field models, focusing on the bispectrum in the squeezed limit. A
conventional prediction states that the bispectrum in this limit is related to
the power spectrum through the so-called consistency relation. However, it
turns out that, if we adopt a genuine gauge invariant variable which is
naturally composed purely of the information in our local universe, the leading
term for the bispectrum in the squeezed limit predicted by the consistency
relation vanishes.Comment: 12 pages; v2: accepted version in JCA
Yang-Mills fields on CR manifolds
We study pseudo Yang-Mills fields on a compact strictly pseudoconvex CR
manifold.Comment: 52 page
Evidence for a rapid decrease in Pluto's atmospheric pressure revealed by a stellar occultation in 2019
We report observations of a stellar occultation by Pluto on 2019 July 17. A
single-chord high-speed (time resolution s) photometry dataset was
obtained with a CMOS camera mounted on the Tohoku University 60 cm telescope
(Haleakala, Hawaii). The occultation light curve is satisfactorily fitted to an
existing Pluto's atmospheric model. We find the lowest pressure value at a
reference radius of among those reported after 2012,
indicating a possible rapid (approximately of the previous
value) pressure drop between 2016 (the latest reported estimate) and 2019.
However, this drop is detected at a level only and still requires
confirmation from future observations. If real, this trend is opposite to the
monotonic increase of Pluto's atmospheric pressure reported by previous
studies. The observed decrease trend is possibly caused by ongoing
condensation processes in the Sputnik Planitia glacier associated with an
orbitally driven decline of solar insolation, as predicted by previous
theoretical models. However, the observed amplitude of the pressure decrease is
larger than the model predictions.Comment: 7 pages, 3 figures, accepted for publication in Astronomy and
Astrophysic
Feedback-free optical cavity with self-resonating mechanism
We demonstrated the operation of a high finesse optical cavity without
utilizing an active feedback system to stabilize the resonance. The effective
finesse, which is a finesse including the overall system performance, of the
cavity was measured to be , and the laser power stored in
the cavity was kW, which is approximately 187,000 times greater
than the incident power to the cavity. The stored power was stabilized with a
fluctuation of , and we confirmed continuous cavity operation for more
than two hours. This result has the potential to trigger an innovative
evolution for applications that use optical resonant cavities such as compact
photon sources with laser-Compton scattering or cavity enhanced absorption
spectroscopy.Comment: 5 pages, 7 figure
On invariants of almost symplectic connections
We study the irreducible decomposition under Sp(2n, R) of the space of
torsion tensors of almost symplectic connections. Then a description of all
symplectic quadratic invariants of torsion-like tensors is given. When applied
to a manifold M with an almost symplectic structure, these instruments give
preliminary insight for finding a preferred linear almost symplectic connection
on M . We rediscover Ph. Tondeur's Theorem on almost symplectic connections.
Properties of torsion of the vectorial kind are deduced
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