14,841 research outputs found
The Effect of Zonally Asymmetric Ozone Heating on the Northern Hemisphere Winter Polar Stratosphere
[1] Previous modeling studies have found significant differences in winter extratropical stratospheric temperatures depending on the presence or absence of zonally asymmetric ozone heating (ZAOH), yet the physical mechanism causing these differences has not been fully explained. The present study describes the effect of ZAOH on the dynamics of the Northern Hemisphere extratropical stratosphere using an ensemble of free-running atmospheric general circulation model simulations over the 1 December - 31 March period. We find that the simulations including ZAOH produce a significantly warmer and weaker stratospheric polar vortex in mid-February due to more frequent major stratospheric sudden warmings compared to the simulations using only zonal mean ozone heating. This is due to regions of enhanced Eliassen-Palm flux convergence found in the region between 40°N–70°N latitude and 10–0.05 hPa. These results are consistent with changes in the propagation of planetary waves in the presence of ZAOH predicted by an ozone-modified refractive index
Janus configurations with SL(2,Z)-duality twists, Strings on Mapping Tori, and a Tridiagonal Determinant Formula
We develop an equivalence between two Hilbert spaces: (i) the space of states
of Chern-Simons theory with a certain class of tridiagonal matrices of
coupling constants (with corners) on ; and (ii) the space of ground states
of strings on an associated mapping torus with fiber. The equivalence is
deduced by studying the space of ground states of -twisted circle
compactifications of gauge theory, connected with a Janus configuration,
and further compactified on . The equality of dimensions of the two
Hilbert spaces (i) and (ii) is equivalent to a known identity on determinants
of tridiagonal matrices with corners. The equivalence of operator algebras
acting on the two Hilbert spaces follows from a relation between the Smith
normal form of the Chern-Simons coupling constant matrix and the isometry group
of the mapping torus, as well as the torsion part of its first homology group.Comment: 21 pages, typos correcte
Cleaning up Eta Carinae: Detection of Ammonia in the Homunculus
We report the first detection of ammonia in the Homunculus nebula around eta
Carinae, which is also the first detection of emission from a polyatomic
molecule in this or any other luminous blue variable (LBV) nebula. Observations
of the NH3 (J,K)=(3,3) inversion transition made with the Australia Telescope
Compact Array reveal emission at locations where infrared H2 emission had been
detected previously, near the strongest dust emission in the core of the
Homunculus. We also detect ammonia emission from the so-called ``strontium
filament'' in the equatorial disk. The presence of NH3 around eta Car hints
that molecular shells around some Wolf-Rayet stars could have originated in
prior LBV eruptions, rather than in cool red supergiant winds or the ambient
interstellar medium. Combined with the lack of any CO detection, NH3 seems to
suggest that the Homunculus is nitrogen rich like the ionized ejecta around eta
Car. It also indicates that the Homunculus is a unique laboratory in which to
study unusual molecule and dust chemistry, as well as their rapid formation in
a nitrogen-rich environment around a hot star. We encourage future observations
of other transitions like NH3 (1,1) and (2,2), related molecules like N2H+, and
renewed attempts to detect CO.Comment: 4 pages, accepted to ApJ letter
Continuous phase amplification with a Sagnac interferometer
We describe a weak value inspired phase amplification technique in a Sagnac
interferometer. We monitor the relative phase between two paths of a slightly
misaligned interferometer by measuring the average position of a split-Gaussian
mode in the dark port. Although we monitor only the dark port, we show that the
signal varies linearly with phase and that we can obtain similar sensitivity to
balanced homodyne detection. We derive the source of the amplification both
with classical wave optics and as an inverse weak value.Comment: 5 pages, 4 figures, previously submitted for publicatio
Deep dielectric charging of regolith within the Moon\u27s permanently shadowed regions
Abstract Energetic charged particles, such as galactic cosmic rays (GCRs) and solar energetic particles (SEPs), can penetrate deep within the lunar surface, resulting in deep dielectric charging. This charging process depends on the GCR and SEP currents, as well as on the regolith\u27s electrical conductivity and permittivity. In permanently shadowed regions (PSRs) near the lunar poles, the discharging timescales are on the order of a lunation (∼20 days). We present the first predictions for deep dielectric charging of lunar regolith. To estimate the resulting subsurface electric fields, we develop a data-driven, one-dimensional, time-dependent model. For model inputs, we use GCR data from the Cosmic Ray Telescope for the Effects of Radiation on board the Lunar Reconnaissance Orbiter and SEP data from the Electron, Proton, and Alpha Monitor on the Advanced Composition Explorer. We find that during the recent solar minimum, GCRs create persistent electric fields up to ∼700 V/m. We also find that large SEP events create transient but strong electric fields (≥106 V/m) that may induce dielectric breakdown. Such breakdown would likely result in significant modifications to the physical and chemical properties of the lunar regolith within PSRs. Key Points Energetic charged particles deep dielectrically charge the lunar regolithWe model the resulting subsurface electric fieldsThe electric fields may be great enough to induce dielectric breakdown
Boosting Higgs pair production in the final state with multivariate techniques
The measurement of Higgs pair production will be a cornerstone of the LHC
program in the coming years. Double Higgs production provides a crucial window
upon the mechanism of electroweak symmetry breaking and has a unique
sensitivity to the Higgs trilinear coupling. We study the feasibility of a
measurement of Higgs pair production in the final state at
the LHC. Our analysis is based on a combination of traditional cut-based
methods with state-of-the-art multivariate techniques. We account for all
relevant backgrounds, including the contributions from light and charm jet
mis-identification, which are ultimately comparable in size to the irreducible
QCD background. We demonstrate the robustness of our analysis strategy in
a high pileup environment. For an integrated luminosity of
ab, a signal significance of is obtained,
indicating that the final state alone could allow for the
observation of double Higgs production at the High-Luminosity LHC.Comment: 47 pages, 22 figures. v2: updated references, added comparison of
post-MVA kinematic distributions. v3: matches published version in EPJ
Additionality from Payments for Environmental Services with Technology Diffusion
Because payments for environmental services (PES) often subsidize practices that offer latent private benefits, there are concerns that PES programs may provide little additional environmental benefits. Previous literature has framed the problem of non-additionality as an adverse selection problem. We develop a model where moral hazard can also arise because some agents delay adoption due to the incentive of potentially receiving a payment in the future. Moral hazard arises when agents have expectations of potential future subsidies, the technology naturally diffuses without a policy, and a subsidy is only available if the agent has not previously adopted the technology. We develop a conceptual model to illustrate the moral hazard incentive and conduct numerical simulations to understand the impact of policy parameters on aggregate outcomes. Numerical simulations illustrate that moral hazard creates a non-monotonic relationship between policy parameters—such as the subsidy and budget levels—and the net change in adoption induced by the program because some agents delay adoption. We also find that the cost-effectiveness of the policy is smaller when the policy is introduced during periods of rapid technology adoption
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