1,795 research outputs found
In search of an observational quantum signature of the primordial perturbations in slow-roll and ultra slow-roll inflation
In the standard inflationary paradigm, cosmological density perturbations are
generated as quantum fluctuations in the early Universe, but then undergo a
quantum-to-classical transition. A key role in this transition is played by
squeezing of the quantum state, which is a result of the strong suppression of
the decaying mode component of the perturbations. Motivated by ever improving
measurements of the cosmological perturbations, we ask whether there are
scenarios where this decaying mode is nevertheless still observable in the late
Universe, ideally leading to a ``smoking gun'' signature of the quantum nature
of the perturbations. We address this question by evolving the quantum state of
the perturbations from inflation into the post-inflationary Universe. After
recovering the standard result that in slow-roll (SR) inflation the decaying
mode is indeed hopelessly suppressed by the time the perturbations are observed
(by orders of magnitude), we turn to ultra slow-roll (USR)
inflation, a scenario in which the usual decaying mode actually grows on
super-horizon scales. Despite this drastic difference in the behavior of the
mode functions, we find also in USR that the late-Universe decaying mode
amplitude is dramatically suppressed, in fact by the same orders of
magnitude. We finally explain that this large suppression is a general result
that holds beyond the SR and USR scenarios considered and follows from a
modified version of Heisenberg's uncertainty principle and the observed
amplitude of the primordial power spectrum. The classical behavior of the
perturbations is thus closely related to the classical behavior of macroscopic
objects drawing an analogy with the position of a massive particle, the
curvature perturbations today have an enormous effective mass of order , making them highly classical.Comment: 27 pages, 7 figures. Comments welcom
Opportunities and constraints for improved vegetable production technology in tropical Asia
A description of the characteristics of vegetable production in tropical Asia is presented. The description is followed by a discussion of the opportunities and constraints of improved non-seed vegetable production technologies. Sowing of seeds and seedling emergence, transplant production, irrigation, mulching, fertiliser use, crop protection and weed control methods, protected cultivation and harvest date planning are discussed in relation to their use and impact. Conditions for successful introduction of new technologies and the role of outside actors are discussed. It is argued that in order to increase the success of adoption of improved technologies, farmers and public and private institutions should work together. With increasing prosperity, the demand for vegetables, especially in the expanding urban areas, will increase, leading to the intensification of production and higher profitability. With better profitability, the application of mulch, drip irrigation, fertigation and protected cultivation will become more common. With increasing production, harvest date planning as related to year-round city market demand, will become essential to improve profitability. It is recommended that, next to the development and introduction of improved production technologies, research and extension on vegetables in tropical Asia, should also focus on methods to improve harvest date planning and year-round suppl
To Bin or Not To Bin: Decorrelating the Cosmic Equation of State
The physics behind the acceleration of the cosmic expansion can be elucidated
through comparison of the predictions of dark energy equations of state to
observational data. In seeking to optimize this, we investigate the advantages
and disadvantages of using principal component analysis, uncorrelated
bandpowers, and the equation of state within redshift bins. We demonstrate that
no one technique is a panacea, with tension between clear physical
interpretation from localization and from decorrelated errors, as well as model
dependence and form dependence. Specific lessons include the critical role of
proper treatment of the high redshift expansion history and the lack of a
unique, well defined signal-to-noise or figure of merit.Comment: 26 pages, 28 figure
Calibrating Dark Energy
Exploring the diversity of dark energy dynamics, we discover a calibration
relation, a uniform stretching of the amplitude of the equation of state time
variation with scale factor. This defines homogeneous families of dark energy
physics. The calibration factor has a close relation to the standard time
variation parameter w_a, and we show that the new, calibrated w_a describes
observables, i.e. distance and Hubble parameter as a function of redshift,
typically to an accuracy level of 10^{-3}. We discuss implications for figures
of merit for dark energy science programs.Comment: 9 pages, 10 figure
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