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At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Calculation of energy levels, lifetimes and radiative data for La XXIX to Sm XXXIV

Highlights: • Lowest 27 levels for La XXIX to Sm XXXIV are calculated. • Radiative data for E1, E2, M1 and M2 transitions within lowest 27 levels are presented. • Effect of nuclear charge on the transition wavelength of allowed EUV transitions is studied graphically. • Effect of nuclear charge on transition probability of allowed EUV transitions is studied graphically. • Lifetimes for lowest 27 fine structure levels are provided. We present the most comprehensive atomic data for La XXIX to Sm XXXIV with single electron excitation from M-shell to N-shell and N-shell to higher shells. We have presented energy levels, lifetimes and radiative data using Multi-configuration Dirac–Fock (MCDF) method for the lowest 27 states belonging to the configuration 3d{sup 10}4l (l=0,1,2,3), 3d{sup 10}5l (l=0,1,2,3,4), 3d{sup 10}6l (l=0,1,2,3,4) and 3d{sup 9}4s{sup 2}. We have also considered relativistic effects by incorporating quantum electrodynamics (QED) and Breit corrections. We have made comparisons of our presented results with available theoretical as well as experimental results and a good agreement is achieved. Further, we have also reported energy levels by performing distorted wave calculations with fully relativistic flexible atomic code (FAC). The calculations match well with MCDF results. Additionally, we have investigated the effect of nuclear charge on transition wavelength and radiative rates for strong Extreme Ultraviolet (EUV) transitions from n=4→4. We believe that our reported data in this work may be useful in various applications of lanthanide ions related to broad area of research such as applied physics, laser physics and astrophysics etc.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2016

Energy levels, lifetimes and radiative data of Ba XXVI

Highlights: • Lowest 110 levels for Ba XXVI are calculated. • Radiative data for E1, E2, M1 and M2 transitions within lowest 110 levels are presented. • Lifetimes for lowest 110 fine structure levels are provided. We report an extensive and an elaborate theoretical study of atomic data for Ba XXVI by considering Singlet, Doublet and Triplet (SDT) electron excitations within N-shell and single excitations from N-shell to O-shell. We have calculated energy levels and lifetimes for lowest 110 fine structure levels by using Multi-configuration Dirac–Fock method (MCDF). We have also considered Quantum Electrodynamics (QED) and Breit corrections in our calculations. We have presented the radiative data for electric and magnetic dipole (E1, M1) and quadrupole (E2, M2) transitions among lowest 110 levels. We have made comparisons of our calculated excitation energies and EUV (Extreme Ultraviolet) transition wavelengths with experimentally observed energy levels and wavelengths and achieved good agreement. We have also computed energy levels by performing similar relativistic distorted wave calculations using Flexible Atomic Code (FAC). Additionally, we have provided new atomic data for Ba XXVI which are not published elsewhere in the literature. We believe that our results may be beneficial in fusion plasma research and astrophysical investigations and applications.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Energy levels, lifetimes and radiative data of W LV

Calculations of energy levels, radiative data and lifetimes are reported for tungsten Ca-like ion (W LV) by using multi-configuration Dirac–Fock (MCDF) method. The GRASP2K package is adopted to carry out a large-scale systematic computation with a restricted active space treatment; the Breit interaction and QED effects are included in subsequent relativistic configuration interaction calculations. The energies and lifetimes of the lowest 119 levels are listed; the main leading configuration of the levels is of the ground state configuration [Ne]3s{sup 2}3p{sup 6}3d{sup 2} and the first excited configuration [Ne]3s{sup 2}3p{sup 5}3d{sup 3}. The wavelengths, radiative rates and oscillator strengths for relatively strong E1, E2, M1, and M2 transitions are listed. Comparisons with earlier experimental and theoretical values are made. The average relative deviations of energy levels from the NIST results and E1 transition wavelengths from the EBIT experimental results have turned to be only 0.20% and 0.13%, respectively. The other present results are in reasonable agreement with available data. These agreements confirm the reliability and accuracy of the current results. The present datasets may help us with the investigation of the electron–electron correlation effects in complex multi-electron highly charged heavy ions and of the diagnosis of tungsten impurity plasmas in fusion science.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Relativistic large scale CI calculations of energies, transition rates and lifetimes in Ca-like ions between Co VIII and Zn XI

Energies, E1, E2 and M1 transition rates and lifetimes are reported for the lowest 134 fine-structure levels of the 3p{sup 6}3d{sup 2}, 3p{sup 6}3d4s, 3p{sup 5}3d{sup 3} and 3p{sup 6}3d4p configurations in all Ca-like ions between Co VIII and Zn XI. The calculations have been performed using the multiconfiguration Dirac–Hartree–Fock (MCDHF) and relativistic configuration interaction (RCI) methods. Important core–valance and core–core electron correlation effects are systematically accounted with large scale configuration interaction expansion. The Breit interaction and leading quantum-electrodynamical (QED) contributions such as the vacuum polarization and self-energy corrections are also included in the RCI calculations. The results are compared with the compiled data from the NIST ASD and other calculations to evaluate the accuracy of the present calculations. Our results have good agreement with previous relativistic many-body perturbation theory (RMBPT) calculations and the data from the NIST ASD, except for Zn XI. Present calculations provide some missing data, especially for Cu X and Zn XI, in the NIST ASD.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Energy levels, weighted oscillator strengths, transition rates, lifetimes, hyperfine structures and isotope shifts of He-like-Sn deduced from the relativistic multiconfiguration Dirac–Hartree–Fock and second-order many-body perturbation theory calculations

We disclose relativistic multiconfiguration Dirac–Hartree–Fock (MCDHF) spectrum calculations for SnXLIX. Energy levels, weighted oscillator strengths, isotope shifts, hyperfine structure and Landé g{sub J} factors are calculated for 127 odd- and even-parity states as well as lifetimes and transition rates between these states. To scrutinize the accuracy of our results, we have implemented parallel calculations using a Flexible Atomic Code (FAC) by introducing the Second-Order Many-Body Perturbation Theory (MBPT) method. Additionally, the Breit interaction and leading quantum electrodynamic effects (QED) are included as perturbations in extensive relativistic configuration interaction (RCI) calculations. We signal that, our calculations for SnXLIX are made for the first time and they provide to date the most accurate and complete atomic data related to this ion.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

Causal signal transmission by quantum fields. V: Generalised Keldysh rotations and electromagnetic response of the Dirac sea

The connection between real-time quantum field theory (RTQFT) [see, e.g., A. Kamenev and A. Levchenko, Adv. Phys. 58 (2009) 197] and phase-space techniques [E. Wolf and L. Mandel, Optical Coherence and Quantum Optics (Cambridge, 1995)] is investigated. The Keldysh rotation that forms the basis of RTQFT is shown to be a phase-space mapping of the quantum system based on the symmetric (Weyl) ordering. Following this observation, we define generalised Keldysh rotations based on the class of operator orderings introduced by Cahill and Glauber [K.E. Cahill, R.J. Glauber, Phys. Rev. 177 (1969) 1882]. Each rotation is a phase-space mapping, generalising the corresponding ordering from free to interacting fields. In particular, response transformation [L.I. Plimak, S. Stenholm, Ann. Phys. (N.Y.) 323 (2008) 1989] extends the normal ordering of free-field operators to the time-normal ordering of Heisenberg operators. Structural properties of the response transformation, such as its association with the nonlinear quantum response problem and the related causality properties, hold for all generalised Keldysh rotations. Furthermore, we argue that response transformation is especially suited for RTQFT formulation of spatial, in particular, relativistic, problems, because it extends cancellation of zero-point fluctuations, characteristic of the normal ordering, to interacting fields. As an example, we consider quantised electromagnetic field in the Dirac sea. In the time-normally-ordered representation, dynamics of the field looks essentially classical (fields radiated by currents), without any contribution from zero-point fluctuations. For comparison, we calculate zero-point fluctuations of the interacting electromagnetic field under orderings other than time-normal. The resulting expression is physically inconsistent: it does not obey the Lorentz condition, nor Maxwell's equations. - Highlights: Black-Right-Pointing-Pointer The Keldysh rotation is a phase-space mapping based on Weyl's operator ordering. Black-Right-Pointing-Pointer Generalised Keldysh rotations (GKRs) based on other orderings are introduced. Black-Right-Pointing-Pointer Special properties of the GKR based on the normal ordering are elucidated. Black-Right-Pointing-Pointer In relativistic QED, other rotations are shown to be physically inconsistent.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Effective dynamics of a classical point charge

The effective Lagrangian of a point charge is derived by eliminating the electromagnetic field within the framework of the classical closed time path formalism. The short distance singularity of the electromagnetic field is regulated by an UV cutoff. The Abraham–Lorentz force is recovered and its similarity to quantum anomalies is underlined. The full cutoff-dependent linearized equation of motion is obtained, no runaway trajectories are found but the effective dynamics shows acausality if the cutoff is beyond the classical charge radius. The strength of the radiation reaction force displays a pole in its cutoff-dependence in a manner reminiscent of the Landau-pole of perturbative QED. Similarity between the dynamical breakdown of the time reversal invariance and dynamical symmetry breaking is pointed out. -- Highlights: •Extension of the classical action principle for dissipative systems. •New derivation of the Abraham–Lorentz force for a point charge. •Absence of a runaway solution of the Abraham–Lorentz force. •Acausality in classical electrodynamics. •Renormalization of classical electrodynamics of point charges.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

A duality web in 2 + 1 dimensions and condensed matter physics

Building on earlier work in the high energy and condensed matter communities, we present a web of dualities in 2 + 1 dimensions that generalize the known particle/vortex duality. Some of the dualities relate theories of fermions to theories of bosons. Others relate different theories of fermions. For example, the long distance behavior of the 2+1-dimensional analog of QED with a single Dirac fermion (a theory known as U(1) 1/2 ) is identified with the O(2) Wilson-Fisher fixed point. The gauged version of that fixed point with a Chern-Simons coupling at level one is identified as a free Dirac fermion. The latter theory also has a dual version as a fermion interacting with some gauge fields. Assuming some of these dualities, other dualities can be derived. Our analysis resolves a number of confusing issues in the literature including how time reversal is realized in these theories. It also has many applications in condensed matter physics like the theory of topological insulators (and their gapped boundary states) and the problem of electrons in the lowest Landau level at half filling. (Our techniques also clarify some points in the fractional Hall effect and its description using flux attachment.) In addition to presenting several consistency checks, we also present plausible (but not rigorous) derivations of the dualities and relate them to 3 + 1-dimensional S-duality.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Exact quantisation of the relativistic Hopfield model

We investigate the quantisation in the Heisenberg representation of a relativistically covariant version of the Hopfield model for dielectric media, which entails the interaction of the quantum electromagnetic field with the matter dipole fields, represented by a mesoscopic polarisation field. A full quantisation of the model is provided in a covariant gauge, with the aim of maintaining explicit relativistic covariance. Breaking of the Lorentz invariance due to the intrinsic presence in the model of a preferred reference frame is also taken into account. Relativistic covariance forces us to deal with the unphysical (scalar and longitudinal) components of the fields, furthermore it introduces, in a more tricky form, the well-known dipole ghost of standard QED in a covariant gauge. In order to correctly dispose of this contribution, we implement a generalised Lautrup trick. Furthermore, causality and the relation of the model with the Wightman axioms are also discussed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Probability of radiation of twisted photons in the infrared domain

Highlights: •Infrared asymptotics of twisted photon radiation in QED is studied. •General selection rules for the twisted photon radiation are proved. •Exact formulas for the twisted photon edge radiation are obtained. •Edge radiation is a superradiant source of twisted photons in the infrared domain. -- Abstract: The infrared asymptotics of the probability of radiation of twisted photons in an arbitrary scattering process of quantum electrodynamics in vacuum is investigated. This asymptotics is universal and corresponds to the radiation produced by a classical current. Such radiation is known as edge radiation. We represent it in terms of twisted photons, and exact analytical formulas for the average number of radiated twisted photons are derived. We find the average projection of the total angular momentum of the edge radiation and the angular momentum per photon. It is shown that edge radiation can be used as a source of twisted photons with a large angular momentum. Moreover, this radiation can be employed as a superradiant coherent source of twisted photons in the infrared domain, in particular, the THz part of the electromagnetic spectrum. Several general selection rules for the radiation and absorption of twisted photons are proved. In particular, these selection rules allow one to modulate the one-particle radiation probability by means of scattering of charged particles on symmetrically arranged crystals.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Nonequilibrium steady state and heat transport in nonlinear open quantum systems: Stochastic influence action and functional perturbative analysis

In this paper, we show that a nonequilibrium steady state (NESS) exists at late times in open quantum systems with weak nonlinearity by following its nonequilibrium dynamics with a perturbative analysis. We consider an oscillator chain containing three-types of anharmonicity: cubic α- and quartic β-type Fermi–Pasta–Ulam–Tsingou (FPUT) nearest-oscillator interactions and the on-site (pinned) Klein–Gordon (KG) quartic self-interaction. Assuming weak nonlinearity, we introduce a stochastic influence action approach to the problem and obtain the energy flows in different junctures across the chain. The formal results obtained here can be used for quantum transport problems in weakly nonlinear quantum systems. For α-type anharmonicity, we observe that the first-order corrections do not play any role in the thermal transport in the NESS of the configuration we considered. For KG and β-types anharmonicity, we work out explicitly the case of two weakly nonlinearly coupled oscillators, with results scalable to any number of oscillators. We examine the late-time energy flows from one thermal bath to the other via the coupled oscillators, and show that both the zeroth- and the first-order contributions of the energy flows become constant in time at late times, signaling the existence of a late-time NESS to first order in nonlinearity. Our perturbative calculations provide a measure of the strength of nonlinearity for nonlinear open quantum systems, which may help control the mesoscopic heat transport distinct from or close to linear transport. Furthermore, our results also give a benchmark for the numerical challenge of simulating heat transport. Our setup and predictions can be implemented and verified by investigating heat flow in an array of Josephson junctions in the limit of large Josephson energy with the platform of circuit QED.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Quantum field theory with the generalized uncertainty principle II: Quantum Electrodynamics

Highlights: • Relativistic Generalized Uncertainty Principle gives Frame independent minimum length. • Quantum Gravity modified Dirac equation from Modified Klein–Gordon Equations. • There exists a Quantum Gravity modified Lagrangian for a spinor field theory. • Feynman vertices contain 2 fermions & up to 5 gauge bosons are allowed. • Minimum length modifies the amplitude of Electrodynamic electron–muon scattering. Continuing our earlier work on the application of the Relativistic Generalized Uncertainty Principle (RGUP) to quantum field theories, in this paper we study Quantum Electrodynamics (QED) with minimum length. We obtain expressions for the Lagrangian, Feynman rules and scattering amplitudes of the theory, and discuss their consequences for current and future high energy physics experiments. We hope this will provide an improved window for testing Quantum Gravity effects in the laboratory.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Relativistic levels of mesic atoms

We revisit the derivation of the covariant two-body scalar-fermion equation with a Coulomb interaction, presented in a previous paper. We show that it can be given the formal aspect of a Dirac equation, but for the fact that the eigenvalue is also contained in one of the coefficients and thus it is not linearly included. The discussion of the boundary value problem is therefore different, although some properties of the Dirac equation can be recovered in an approximation bringing back to the concept of reduced mass. We discuss a mixed analytic-numerical method of solution which allows to obtain very accurate results and we calculate the lowest levels, states and QED corrections for pionic and kaonic atoms.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Unveiling micro-chemo-mechanical properties of C–(A)–S–H and other phases in blended-cement pastes

Current demand for novel highly sustainable concrete urges improving the links between chemical and mechanical effects of supplementary cementitious materials (SCMs) on the microstructure of blended-cement pastes. In this work, coupled NanoIndentation and Quantitative Energy Dispersion Spectroscopy (NI-QEDS) was applied to disclose chemo-mechanical properties of microstructure phases in systems incorporating typical dosages of fly ash, slag, metakaolin, or glass powder. For a fixed water-to-binder ratio of 0.4, the C–(A)–S–H chemistry was significantly affected by the SCMs, while its average mechanical properties varied within the limited ranges M ≈ 25–27 GPa, H ≈ 0.7–0.8 GPa and C ≈ 180–230 GPa. The SCMs further changed the arrangement of anhydrous phases and minor hydrates embedded in the C–(A)–S–H matrix, which were also characterized (e.g., Portlandite, AFm such as carboaluminates, or an hydrotalcite-like phase). Finally, engineering properties of blended-cement matrices requires tailoring both the intermix of hydrates and the rigid anhydrous SCM inclusions.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Reconstructing the kinematics of deep inelastic scattering with deep learning

We introduce a method to reconstruct the kinematics of neutral-current deep inelastic scattering (DIS) using a deep neural network (DNN). Unlike traditional methods, it exploits the full kinematic information of both the scattered electron and the hadronic-final state, and it accounts for QED radiation by identifying events with radiated photons and event-level momentum imbalance. The method is studied with simulated events at HERA and the future Electron–Ion Collider (EIC). We show that the DNN method outperforms all the traditional methods over the full phase space, improving resolution and reducing bias. Our method has the potential to extend the kinematic reach of future experiments at the EIC, and thus their discovery potential in polarized and nuclear DIS.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Chirality transfer and chiral turbulence in gauge theories

Chirality transfer between fermions and gauge fields plays a crucial role for understanding the dynamics of anomalous transport phenomena such as the Chiral Magnetic Effect. In this proceeding we present a first principles study of these processes based on classical-statistical real-time lattice simulations of strongly coupled QED (e 2 N f = 64). Furthermore, our simulations demonstrate that a chirality imbalance in the fermion sector triggers chiral plasma instabilities in the gaugefield sector, which ultimately lead to the generation of long range helical magnetic fields via an self-similar turbulent cascade of the magnetic helicity.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Detailed comparison of renormalization scale-setting procedures based on the principle of maximum conformality

The Principle of Maximum Conformality (PMC), which generalizes the conventional Gell-Mann-Low method for scale-setting in perturbative QED to non-Abelian QCD, provides a rigorous method for achieving unambiguous scheme-independent, fixed-order predictions for physical observables consistent with the principles of the renormalization group. In addition to the original multi-scale-setting approach (PMCm), two variations of the PMC have been proposed to deal with ambiguities associated with the uncalculated higher order terms in the pQCD series, i.e. the single-scale-setting approach (PMCs) and the procedures based on ``intrinsic conformality" (PMC ∞ ). In this paper, we will give a detailed comparison of these PMC approaches by comparing their predictions for three important quantities R e+e– , R τ , and $Γ(H→b\bar{b}$) up to four-loop pQCD corrections. The PMCs approach determines an overall effective running coupling α s (Q) by the recursive use of the renormalization group equation, whose argument Q represents the actual momentum flow of the process. Our numerical results show that the PMCs method, which involves a somewhat simpler analysis, can serve as a reliable substitute for the full multi-scale PMCm method, and that it leads to more precise pQCD predictions with small residual scale dependence.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

High precision measurement of Compton scattering in the 5 GeV region

The cross section of atomic electron Compton scattering $\gamma + e \rightarrow \gamma^\prime + e^\prime $ was measured in the 4.40--5.475 GeV photon beam energy region by the {\em PrimEx} collaboration at Jefferson Lab with an accuracy of 2\% and less. The results are consistent with theoretical predictions that include next-to-leading order radiative corrections. The measurements provide the first high precision test of this elementary QED process at beam energies greater than 0.1 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗