146 research outputs found
Scratches from the Past: Inflationary Archaeology through Features in the Power Spectrum of Primordial Fluctuations
Inflation may provide unique insight into the physics at the highest
available energy scales that cannot be replicated in any realistic terrestrial
experiment. Features in the primordial power spectrum are generically predicted
in a wide class of models of inflation and its alternatives, and are
observationally one of the most overlooked channels for finding evidence for
non-minimal inflationary models. Constraints from observations of the cosmic
microwave background cover the widest range of feature frequencies, but the
most sensitive constraints will come from future large-scale structure surveys
that can measure the largest number of linear and quasi-linear modes.Comment: 5 pages + references, 1 figure; science white paper submitted to the
Astro2020 decadal surve
Optimal Carbon Taxes for Emissions Targets in the Electricity Sector
The most dangerous effects of anthropogenic climate change can be mitigated
by using emissions taxes or other regulatory interventions to reduce greenhouse
gas (GHG) emissions. This paper takes a regulatory viewpoint and describes the
Weighted Sum Bisection method to determine the lowest emission tax rate that
can reduce the anticipated emissions of the power sector below a prescribed,
regulatorily-defined target. This bi-level method accounts for a variety of
operating conditions via stochastic programming and remains computationally
tractable for realistically large planning test systems, even when binary
commitment decisions and multi-period constraints on conventional generators
are considered.
Case studies on a modified ISO New England test system demonstrate that this
method reliably finds the minimum tax rate that meets emissions targets. In
addition, it investigates the relationship between system investments and the
tax-setting process. Introducing GHG emissions taxes increases the value
proposition for investment in new cleaner generation, transmission, and energy
efficiency; conversely, investing in these technologies reduces the tax rate
required to reach a given emissions target
Incentivizing Investment and Reliability: A Study on Electricity Capacity Markets
The capacity market, a marketplace to exchange available generation capacity
for electricity production, provides a major revenue stream for generators and
is adopted in several U.S. regions. A subject of ongoing debate, the capacity
market is viewed by its proponents as a crucial mechanism to ensure system
reliability, while critics highlight its drawbacks such as market distortion.
Under a novel analytical framework, we rigorously evaluate the impact of the
capacity market on generators' revenue and system reliability. More
specifically, based on market designs at New York Independent System Operator
(NYISO), we propose market equilibrium-based models to capture salient aspects
of the capacity market and its interaction with the energy market. We also
develop a leader-follower model to study market power. We show that the
capacity market incentivizes the investment of generators with lower net cost
of new entry. It also facilitates reliability by preventing significant
physical withholding when the demand is relatively high. Nevertheless, the
capacity market may not provide enough revenue for peaking plants. Moreover, it
is susceptible to market power, which necessitates tailored market power
mitigation measures depending on market dynamics. We provide further insights
via large-scale experiments on data from NYISO markets
Genome-wide analysis of single-locus and epistasis single-nucleotide polymorphism effects on anti-cyclic citrullinated peptide as a measure of rheumatoid arthritis
The goal of this study was to identify single-locus and epistasis effects of SNP markers on anti-cyclic citrullinated peptide (anti-CCP) that is associated with rheumatoid arthritis, using the North American Rheumatoid Arthritis Consortium data. A square root transformation of the phenotypic values of anti-CCP with sex, smoking status, and a selected subset of 20 single-nucleotide polymorphism (SNP) markers in the model achieved residual normality (p > 0.05). Three single-locus effects of two SNPs were significant (p < 10-4). The epistasis analysis tested five effects of each pair of SNPs, the two-locus interaction, additive Ă— additive, additive Ă— dominance, dominance Ă— additive, and dominance Ă— dominance effects. A total of ten epistasis effects of eight pairs of SNPs on 11 autosomes and the X chromosome had significant epistasis effects (p < 10-7). Three of these epistasis effects reached significance levels of p < 10-8, p < 10-9, and p < 10-10, respectively. Two potential SNP epistasis networks were identified. The results indicate that the genetic factors underlying anti-CCP may include single-gene action and gene interactions and that the gene-interaction mechanism underlying anti-CCP could be a complex mechanism involving pairwise epistasis effects and multiple SNPs
Parallel and serial computing tools for testing single-locus and epistatic SNP effects of quantitative traits in genome-wide association studies
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Probing patchy reionization through tau-21cm correlation statistics
We consider the cross-correlation between free electrons and neutral hydrogen during the epoch of reionization (EoR). The free electrons are traced by the optical depth to reionization Ď„, while the neutral hydrogen can be observed through 21 cm photon emission. As expected, this correlation is sensitive to the detailed physics of reionization. Foremost, if reionization occurs through the merger of relatively large halos hosting an ionizing source, the free electrons and neutral hydrogen are anticorrelated for most of the reionization history. A positive contribution to the correlation can occur when the halos that can form an ionizing source are small. A measurement of this sign change in the cross-correlation could help disentangle the bias and the ionization history. We estimate the signal-to-noise ratio of the cross-correlation using the estimator for inhomogeneous reionization proposed by Dvorkin and Smith. We find that with upcoming radio interferometers and cosmic microwave background (CMB) experiments, the cross-correlation is measurable going up to multipoles â„“ ~ 1000. We also derive parameter constraints and conclude that, despite the foregrounds, the cross-correlation provides a complementary measurement of the EoR parameters to the 21 cm and CMB polarization autocorrelations expected to be observed in the coming decade.Physic
CMBPol Mission Concept Study: Probing Inflation with CMB Polarization
We summarize the utility of precise cosmic microwave background (CMB)
polarization measurements as probes of the physics of inflation. We focus on
the prospects for using CMB measurements to differentiate various inflationary
mechanisms. In particular, a detection of primordial B-mode polarization would
demonstrate that inflation occurred at a very high energy scale, and that the
inflaton traversed a super-Planckian distance in field space. We explain how
such a detection or constraint would illuminate aspects of physics at the
Planck scale. Moreover, CMB measurements can constrain the scale-dependence and
non-Gaussianity of the primordial fluctuations and limit the possibility of a
significant isocurvature contribution. Each such limit provides crucial
information on the underlying inflationary dynamics. Finally, we quantify these
considerations by presenting forecasts for the sensitivities of a future
satellite experiment to the inflationary parameters.Comment: 107 pages, 14 figures, 17 tables; Inflation Working Group
contribution to the CMBPol Mission Concept Study; v2: typos fixed and
references adde
Mapping Cosmic Dawn and Reionization: Challenges and Synergies
Cosmic dawn and the Epoch of Reionization (EoR) are among the least explored
observational eras in cosmology: a time at which the first galaxies and
supermassive black holes formed and reionized the cold, neutral Universe of the
post-recombination era. With current instruments, only a handful of the
brightest galaxies and quasars from that time are detectable as individual
objects, due to their extreme distances. Fortunately, a multitude of
multi-wavelength intensity mapping measurements, ranging from the redshifted 21
cm background in the radio to the unresolved X-ray background, contain a
plethora of synergistic information about this elusive era. The coming decade
will likely see direct detections of inhomogenous reionization with CMB and 21
cm observations, and a slew of other probes covering overlapping areas and
complementary physical processes will provide crucial additional information
and cross-validation. To maximize scientific discovery and return on
investment, coordinated survey planning and joint data analysis should be a
high priority, closely coupled to computational models and theoretical
predictions.Comment: 5 pages, 1 figure, submitted to the Astro2020 Decadal Survey Science
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