10 research outputs found
Eigenvector Continuation and Projection-Based Emulators
Eigenvector continuation is a computational method for parametric eigenvalue
problems that uses subspace projection with a basis derived from eigenvector
snapshots from different parameter sets. It is part of a broader class of
subspace-projection techniques called reduced-basis methods. In this colloquium
article, we present the development, theory, and applications of eigenvector
continuation and projection-based emulators. We introduce the basic concepts,
discuss the underlying theory and convergence properties, and present recent
applications for quantum systems and future prospects.Comment: 20 pages, 17 figure
Effective Field Theory and Finite Density Systems
This review gives an overview of effective field theory (EFT) as applied at
finite density, with a focus on nuclear many-body systems. Uniform systems with
short-range interactions illustrate the ingredients and virtues of many-body
EFT and then the varied frontiers of EFT for finite nuclei and nuclear matter
are surveyed.Comment: 27 pages, 5 figure
Pion-nucleus elastic scattering on 12C, 40Ca, 90Zr, and 208Pb at 400 and 500 MeV
Pion-nucleus elastic scattering at energies above the Delta(1232) resonance
is studied using both pi+ and pi- beams on 12C, 40Ca, 90Zr, and 208Pb. The
present data provide an opportunity to study the interaction of pions with
nuclei at energies where second-order corrections to impulse approximation
calculations should be small. The results are compared with other data sets at
similar energies, and with four different first-order impulse approximation
calculations. Significant disagreement exists between the calculations and the
data from this experiment
Model Mixing Using Bayesian Additive Regression Trees
In modern computer experiment applications, one often encounters the
situation where various models of a physical system are considered, each
implemented as a simulator on a computer. An important question in such a
setting is determining the best simulator, or the best combination of
simulators, to use for prediction and inference. Bayesian model averaging (BMA)
and stacking are two statistical approaches used to account for model
uncertainty by aggregating a set of predictions through a simple linear
combination or weighted average. Bayesian model mixing (BMM) extends these
ideas to capture the localized behavior of each simulator by defining
input-dependent weights. One possibility is to define the relationship between
inputs and the weight functions using a flexible non-parametric model that
learns the local strengths and weaknesses of each simulator. This paper
proposes a BMM model based on Bayesian Additive Regression Trees (BART). The
proposed methodology is applied to combine predictions from Effective Field
Theories (EFTs) associated with a motivating nuclear physics application.Comment: 33 pages, 6 figures, additional supplementary material can be found
at https://github.com/jcyannotty/OpenB
Eigenvector Continuation and Projection-Based Emulators
International audienceEigenvector continuation is a computational method for parametric eigenvalue problems that uses subspace projection with a basis derived from eigenvector snapshots from different parameter sets. It is part of a broader class of subspace-projection techniques called reduced-basis methods. In this colloquium article, we present the development, theory, and applications of eigenvector continuation and projection-based emulators. We introduce the basic concepts, discuss the underlying theory and convergence properties, and present recent applications for quantum systems and future prospects
Dense Nuclear Matter Equation of State from Heavy-Ion Collisions
The nuclear equation of state (EOS) is at the center of numerous theoretical
and experimental efforts in nuclear physics. With advances in microscopic
theories for nuclear interactions, the availability of experiments probing
nuclear matter under conditions not reached before, endeavors to develop
sophisticated and reliable transport simulations to interpret these
experiments, and the advent of multi-messenger astronomy, the next decade will
bring new opportunities for determining the nuclear matter EOS, elucidating its
dependence on density, temperature, and isospin asymmetry. Among controlled
terrestrial experiments, collisions of heavy nuclei at intermediate beam
energies (from a few tens of MeV/nucleon to about 25 GeV/nucleon in the
fixed-target frame) probe the widest ranges of baryon density and temperature,
enabling studies of nuclear matter from a few tenths to about 5 times the
nuclear saturation density and for temperatures from a few to well above a
hundred MeV, respectively. Collisions of neutron-rich isotopes further bring
the opportunity to probe effects due to the isospin asymmetry. However,
capitalizing on the enormous scientific effort aimed at uncovering the dense
nuclear matter EOS, both at RHIC and at FRIB as well as at other international
facilities, depends on the continued development of state-of-the-art hadronic
transport simulations. This white paper highlights the role that heavy-ion
collision experiments and hadronic transport simulations play in understanding
strong interactions in dense nuclear matter, with an emphasis on how these
efforts can be used together with microscopic approaches and neutron star
studies to uncover the nuclear EOS
Dense nuclear matter equation of state from heavy-ion collisions
International audienceThe nuclear equation of state (EOS) is at the center of numerous theoretical and experimental efforts in nuclear physics. With advances in microscopic theories for nuclear interactions, the availability of experiments probing nuclear matter under conditions not reached before, endeavors to develop sophisticated and reliable transport simulations to interpret these experiments, and the advent of multi-messenger astronomy, the next decade will bring new opportunities for determining the nuclear matter EOS, elucidating its dependence on density, temperature, and isospin asymmetry. Among controlled terrestrial experiments, collisions of heavy nuclei at intermediate beam energies (from a few tens of MeV/nucleon to about 25 GeV/nucleon in the fixed-target frame) probe the widest ranges of baryon density and temperature, enabling studies of nuclear matter from a few tenths to about 5 times the nuclear saturation density and for temperatures from a few to well above a hundred MeV, respectively. Collisions of neutron-rich isotopes further bring the opportunity to probe effects due to the isospin asymmetry. However, capitalizing on the enormous scientific effort aimed at uncovering the dense nuclear matter EOS, both at RHIC and at FRIB as well as at other international facilities, depends on the continued development of state-of-the-art hadronic transport simulations. This white paper highlights the essential role that heavy-ion collision experiments and hadronic transport simulations play in understanding strong interactions in dense nuclear matter, with an emphasis on how these efforts can be used together with microscopic approaches and neutron star studies to uncover the nuclear EOS