Nuclear Theory·nucl-th

Thursday·April 25, 2019

12 papers—7 primary·5 cross-listed

08
[Submitted on 9 Apr 2019] (cross-list from stat.ME)
Bayesian averaging of computer models with domain discrepancies: a nuclear physics perspective
Vojtech Kejzlar · Léo Neufcourt · Taps Maiti · Frederi Viens
This article studies Bayesian model averaging (BMA) in the context of competing expensive computer models in a typical nuclear physics setup. While it is well known that BMA accounts for the additional uncertainty of the model itself, we show that it also decreases the posterior variance of the prediction errors via an explicit decomposition. We extend BMA to the situation where the competing models are defined on non-identical study regions. Any model's local forecasting difficulty is offset by predictions obtained from the average model, thus extending individual models to the full domain. We illustrate our methodology via pedagogical simulations and applications to forecasting nuclear observables, which exhibit convincing improvements in both the BMA prediction error and empirical coverage probabilities.
Subjects:
stat.ME (stat.ME); Nuclear Theory (nucl-th); Data Analysis, Statistics and Probability (physics.data-an); stat.AP (stat.AP)
arXiv:
1904.04793 [pdf]
9 citations
09
[Submitted on 23 Apr 2019] (cross-list from hep-ex)
Measurement of the mass difference and the binding energy of the hypertriton and antihypertriton
STAR Collaboration: J. Adam · L. Adamczyk · J. R. Adams · J. K. Adkins · G. Agakishiev · M. M. Aggarwal · Z. Ahammed · I. Alekseev · D. M. Anderson · R. Aoyama · A. Aparin · D. Arkhipkin and 337 other authors
According to the CPT theorem, which states that the combined operation of charge conjugation, parity transformation and time reversal must be conserved, particles and their antiparticles should have the same mass and lifetime but opposite charge and magnetic moment. Here, we test CPT symmetry in a nucleus containing a strange quark, more specifically in the hypertriton. This hypernucleus is the lightest one yet discovered and consists of a proton, a neutron, and a $Λ$ hyperon. With data recorded by the STAR detector{\cite{TPC,HFT,TOF}} at the Relativistic Heavy Ion Collider, we measure the $Λ$ hyperon binding energy $B_{Λ}$ for the hypertriton, and find that it differs from the widely used value{\cite{B_1973}} and from predictions{\cite{2019_weak, 1995_weak, 2002_weak, 2014_weak}}, where the hypertriton is treated as a weakly bound system. Our results place stringent constraints on the hyperon-nucleon interaction{\cite{Hammer2002, STAR-antiH3L}}, and have implications for understanding neutron star interiors, where strange matter may be present{\cite{Chatterjee2016}}. A precise comparison of the masses of the hypertriton and the antihypertriton allows us to test CPT symmetry in a nucleus with strangeness for the first time, and we observe no deviation from the expected exact symmetry.
Subjects:
High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1904.10520 [pdf]
Nat.Phys.(2020)·155 citations
10
[Submitted on 24 Apr 2019] (cross-list from cond-mat.quant-gas)
Active Learning Algorithm for Computational Physics
Juan Yao · Yadong Wu · Jahyun Koo · Binghai Yan · Hui Zhai
In large-scale computation of physics problems, one often encounters the problem of determining a multi-dimensional function, which can be time-consuming when computing each point in this multi-dimensional space is already time-demanding. In the work, we propose that the active learning algorithm can speed up such calculations. The basic idea is to fit a multi-dimensional function by neural networks, and the key point is to make the query of labeled data economically by using a stratagem called "query by committee". We present the general protocol of this fitting scheme, as well as the procedure of how to further compute physical observables with the fitted functions. We show that this method can work well with two examples, which are quantum three-body problem in atomic physics and the anomalous Hall conductivity in condensed matter physics, respectively. In these examples, we show that one reaches an accuracy of few percent error for computing physical observables with less than $10%$ of total data points compared with uniform sampling. With these two examples, we also visualize that by using the active learning algorithm, the required data are added mostly in the regime where the function varies most rapidly, which explains the mechanism for the efficiency of the algorithm. We expect broad applications of our method on various kind of computational physics problems.
Comments:
7 pages, 8 figures
Subjects:
Quantum Gases (cond-mat.quant-gas); cond-mat.mtrl-sci (cond-mat.mtrl-sci); Nuclear Theory (nucl-th); Computational Physics (physics.comp-ph)
arXiv:
1904.10692 [pdf]
PRResearch(2020)·13 citations
11
[Submitted on 24 Apr 2019] (cross-list from hep-ph)
Saturation momentum scale extracted from semi-inclusive transverse spectra in high-energy pp collisions
Takeshi Osada🇯🇵 · Takuya Kumaoka🇯🇵
Geometric scaling is well confirmed for transverse momentum distributions observed in proton-proton collisions at LHC energies. We introduced multiplicity dependence on a saturation momentum of the geometrical scaling, assuming the scaling holds for semi-inclusive distributions as well as for inclusive distributions. The saturation momentum is usually given by Bjorken's $x$ variable, but redefinition of the scaling variable can make the saturation momentum a function of collision energy $W$ . We treat the energy as a free parameter (denoted $W^{*}$ to distinguish it from $W$ ) and associate the energy-dependent saturation momentum $Q_{sat} (W^{*})$ with particle number density. By using $Q_{sat} (W^{*})$ for a scaling variable $τ$ , we show semi-inclusive distributions can be geometrically scaled. i.e., all semi-inclusive spectra observed at $W$ =0.90, 2.76 and 7.00 TeV overlap one universal function. The particle density dependences of mean transverse momentum $⟨ p_{T} ⟩$ for LHC energies scales in terms of $Q_{sat} (W^{*})$ . Furthermore, our model explains a scaling property of event-by-event $p_{T}$ fluctuation measure $C_{m} / ⟨ p_{T} ⟩$ at LHC energies for pp collisions, where $C_{m}$ is two-particle transverse momentum correlator. Our analysis of the $p_{T}$ fluctuation makes possible to evaluate a non-perturbative coefficient of the gluon correlation function.
Comments:
2.nd version: 9 pages 8 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1904.10823 [pdf]
PRC(2019)·12 citations
12
[Submitted on 23 Apr 2019] (cross-list from astro-ph.HE)
R-mode instability in compact stars
Cui Zhu🇨🇳 · Yu-bin Wang🇨🇳 · Xia Zhou🇨🇳
R-mode oscillations have been identified as viable and promising targets for continuous gravitational wave searches, meanwhile, it would allow us to probe the interior of compact stars directly. As well as emitting gravitational wave, r-modes would strongly affect the thermal and spin evolution of compact stars. In this paper, we reviewed the theory behind the gravitational wave driven r-mode instability in a rapidly rotating compact star. In particular, we will focus on r-mode instability window, r-mode evolution and detectability of r-mode.
Comments:
contribution to the AIP Proceedings of the Xiamen-CUSTIPEN Workshop on the EOS of Dense Neutron-Rich Matter in the Era of Gravitational Wave Astronomy, Jan. 3-7, 2019, Xiamen, China. arXiv admin note: text overlap with arXiv:0806.1005, arXiv:1510.07051, arXiv:1209.5962 by other authors
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
1904.10957 [pdf]
AIP Conf.Proc.(2019)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE

Bayesian averaging of computer models with domain discrepancies: a nuclear physics perspective

Measurement of the mass difference and the binding energy of the hypertriton and antihypertriton

Active Learning Algorithm for Computational Physics

Saturation momentum scale extracted from semi-inclusive transverse spectra in high-energy pp collisions

R-mode instability in compact stars

Affiliations