774 research outputs found
Power Priors for Replication Studies
The ongoing replication crisis in science has increased interest in the
methodology of replication studies. We propose a novel Bayesian analysis
approach using power priors: The likelihood of the original study's data is
raised to the power of , and then used as the prior distribution in the
analysis of the replication data. Posterior distribution and Bayes factor
hypothesis tests related to the power parameter quantify the degree of
compatibility between the original and replication study. Inferences for other
parameters, such as effect sizes, dynamically borrow information from the
original study. The degree of borrowing depends on the conflict between the two
studies. The practical value of the approach is illustrated on data from three
replication studies, and the connection to hierarchical modeling approaches
explored. We generalize the known connection between normal power priors and
normal hierarchical models for fixed parameters and show that normal power
prior inferences with a beta prior on the power parameter align with
normal hierarchical model inferences using a generalized beta prior on the
relative heterogeneity variance . The connection illustrates that power
prior modeling is unnatural from the perspective of hierarchical modeling since
it corresponds to specifying priors on a relative rather than an absolute
heterogeneity scale
Unconventional superconductivity without doping: infinite-layer nickelates under pressure
High-temperature unconventional superconductivity quite generically emerges
from doping a strongly correlated parent compound, often (close to) an
antiferromagnetic insulator. The recently developed dynamical vertex
approximation is a state-of-the-art technique that has quantitatively predicted
the superconducting dome of nickelates. Here, we apply it to study the effect
of pressure in the infinite-layer nickelate SrPrNiO. We
reproduce the increase of the critical temperature () under pressure found
in experiment up to 12 GPa. According to our results, can be further
increased with higher pressures. Even without Sr-doping the parent compound,
PrNiO, will become a high-temperature superconductor thanks to a strongly
enhanced self-doping of the \nidxsqysq{} orbital under pressure. With a maximal
\Tc{} of 100\,K around 100\,GPa, nickelate superconductors can reach that of
the best cuprates.Comment: Main text: 6 pages, 4 figures. Supplementary information: 18 pages,
16 figure
No superconductivity in PbCu(PO)O found in orbital and spin fluctuation exchange calculations
Finding a material that turns superconducting under ambient conditions has
been the goal of over a century of research, and recently
PbCu(PO)O aka LK-99 has been put forward as a possible
contestant. In this work, we study the possibility of electronically driven
superconductivity in LK-99 also allowing for electron or hole doping. We use an
derived two-band model of the Cu orbitals for which
we determine interaction values from the constrained random phase approximation
(cRPA). For this two-band model we perform calculations in the fluctuation
exchange (FLEX) approach to assess the strength of orbital and spin
fluctuations. We scan over a broad range of parameters and enforce no magnetic
or orbital symmetry breaking. Even under optimized conditions for
superconductivity, spin and orbital fluctuations turn out to be too weak for
superconductivity anywhere near to room-temperature. We contrast this finding
to non-self-consistent RPA, where it is possible to induce spin-singlet
-wave superconductivity at K if the system is put
close enough to a magnetic instability.Comment: 6 pages, 3 figure
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