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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Effect of the J–J Interaction of Excited States of the Rare-Earth Ion Pr{sup 3+} on Magnetically Polarized Luminescence of Praseodymium-Yttrium Aluminum Garnet

The spectra of luminescence and magnetic circular polarization of luminescence of praseodymium–yttrium aluminum garnet Pr{sup 3+} : Y{sub 3}Al{sub 5}O{sub 12} (PrYAG) are studied in the visible spectral region at temperature T = 300 K. An analysis of spectral dependences of magnetooptical and optical spectra makes it possible to identify optical 4 f–4 f-transitions between Stark sublevels of multiplets {sup 3}P{sub 0}, {sup 3}P{sub 1}, {sup 3}Н{sub 5}, and {sup 3}Н{sub 6} in PrYAG. It was shown that an important role in the spectrum of the degree of magnetic circular polarization of luminescence of this paramagnetic garnet is played by the effect of quantum-mechanical J–J mixing of states of Stark singlets {sup 3}Н{sub 5} and {sup 3}Н{sub 6} of non-Kramer rare-earth ion Pr{sup 3+} in the “green” luminescence band related to forbidden 4 f → 4 f transition {sup 3}P{sub 0} → {sup 3}Н{sub 5} in the visible spectral region. To interpret the spectra of magnetic circular polarization of luminescence, the energy of experimentally determined Stark sublevels of multiplets under study, their irreducible representations and wave functions determined by numerical simulation of the energy spectrum of the rare-earth ion Pr{sup 3+} in the garnet structure are used.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Ultraviolet emission lines of Si ii in quasars—investigating the “Si ii disaster”

The observed line intensity ratios of the Si ii λ1263 and λ1307 multiplets to that of Si ii λ1814 in the broad-line region (BLR) of quasars are both an order of magnitude larger than the theoretical values. This was first pointed out by Baldwin et al., who termed it the “Si ii disaster,” and it has remained unresolved. We investigate the problem in the light of newly published atomic data for Si ii. Specifically, we perform BLR calculations using several different atomic data sets within the CLOUDY modeling code under optically thick quasar cloud conditions. In addition, we test for selective pumping by the source photons or intrinsic galactic reddening as possible causes for the discrepancy, and we also consider blending with other species. However, we find that none of the options investigated resolve the Si ii disaster, with the potential exception of microturbulent velocity broadening and line blending. We find that a larger microturbulent velocity (∼500 km s{sup −1}) may solve the Si ii disaster through continuum pumping and other effects. The CLOUDY models indicate strong blending of the Si ii λ1307 multiplet with emission lines of O i, although the predicted degree of blending is incompatible with the observed λ1263/λ1307 intensity ratios. Clearly, more work is required on the quasar modeling of not just the Si ii lines but also nearby transitions (in particular those of O i) to fully investigate whether blending may be responsible for the Si ii disaster.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Rotational Splitting and Asteroseismic Modeling of the δ Scuti Star EE Camelopardalis

According to the rotational splitting law of g modes, the frequency spectra of EE Cam can be disentangled only with oscillation modes of ℓ = 0, 1, and 2. Fifteen sets of rotational splits were found, and they contain five sets of ℓ = 1 multiplets and 10 sets of ℓ = 2 multiplets. The rotational period of EE Cam is deduced to be P{sub rot}=1.84{sub −0.05}{sup +0.07} days. When we do model fittings, we use two nonradial oscillation modes (f {sub 11} and f {sub 32}), and the fundamental radial mode f {sub 1}. The fitting results show that χ{sup 2} of the best-fitting model is much smaller than those of other theoretical models. The physical parameters of the best-fitting model are M = 2.04 M {sub ⊙}, Z = 0.028, T {sub eff} = 6433 K, logL/L{sub ⊙}=1.416, R = 4.12 R {sub ⊙}, logg=3.518, and χ{sup 2}=0.00035. Furthermore, we find that f {sub 11} and f {sub 32} are mixed modes, which mainly characterize the features of the helium core. The fundamental radial mode f {sub 1} mainly restricts the features of the stellar envelope. Finally, the acoustic radius τ{sub 0} and the period separation Π{sub 0} are determined to be 5.80 hr and 463.7 s, respectively, and the size of the helium core of EE Cam is estimated to be M {sub He} = 0.181 M {sub ⊙} and R {sub He} = 0.0796 R {sub ⊙}.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Generic Construction of the Standard Model Gauge Group and Matter Representations in F-theory

In this work, we describe general classes of 6D and 4D F-theory models with gauge group (SU(3)×SU(2)×U(1))/Z 6 . For 6D F-theory models with no tensor multiplets, we prove that this set of constructions gives all possible consistent supergravity theories with this gauge group and the corresponding generic matter representations, which include those of the MSSM. We expect, though do not prove, that these models are similarly generic for 6D theories with tensor multiplets and for 4D N=1 supergravity theories. Finally, the models in the largest class of these constructions come from deforming an underlying geometry with SU(4)×SU(3)×SU(2), corresponding to Higgsing on three bifundamental fields.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

One-loop holographic Weyl anomaly in six dimensions

We compute O(1) corrections to the holographic Weyl anomaly for six-dimensional N = (1, 0) and (2, 0) theories using the functional Schrödinger method that is conjectured to work for supersymmetric theories on Ricci-flat backgrounds. We show that these corrections vanish for long representations of the N = (1, 0) theory, and we obtain an expression for δ(c – a) for short representations with maximum spin two. We also confirm that the one-loop corrections to the N = (2, 0) M5-brane theory are equal and opposite to the anomaly for the free tensor multiplet. Finally, we discuss the possibility of extending the results to encompass multiplets with spins greater than two.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

$ \mathcal{N}=1 $ deformations and RG flows of $ \mathcal{N}=2 $ SCFTs

Here, we study certain $ \mathcal{N}=1 $ preserving deformations of four-dimensional $ \mathcal{N}=2 $ superconformal field theories (SCFTs) with non-abelian flavor symmetry. The deformation is described by adding an $ \mathcal{N}=1 $ chiral multiplet transforming in the adjoint representation of the flavor symmetry with a superpotential coupling, and giving a nilpotent vacuum expectation value to the chiral multiplet which breaks the flavor symmetry. This triggers a renormalization group flow to an infrared SCFT. Remarkably, we find classes of theories flow to enhanced $ \mathcal{N}=2 $ supersymmetric fixed points in the infrared under the deformation. They include generalized Argyres-Douglas theories and rank-one SCFTs with non-abelian flavor symmetries. Most notably, we find renormalization group flows from the deformed conformal SQCDs to the ( A 1 ,A n ) Argyres-Douglas theories. From these "Lagrangian descriptions," we compute the full superconformal indices of the ( A 1 ,A n ) theories and find agreements with the previous results. Furthermore, we study the cases, including the T N and R 0,N theories of class S and some of rank-one SCFTs, where the deformation gives genuine $ \mathcal{N}=1 $ fixed points.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Rounding out the story of higher derivative consistent truncations

At the two-derivative order, the group manifold reduction of heterotic supergravity on S 3 results in a half-maximal 7D gauged supergravity coupled to three vector multiplets, and a further truncation can be taken to remove the vector multiplets. We demonstrate that this truncation remains consistent at the four-derivative level; we do so both by analysis of the equations of motion and the supersymmetry variations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Superparticle phenomenology from the natural mini-landscape

The methodology of the heterotic mini-landscape attempts to zero in on phenomenologically viable corners of the string landscape where the effective low energy theory is the Minimal Supersymmetric Standard Model with localized grand unification. The gaugino mass pattern is that of mirage-mediation. The magnitudes of various SM Yukawa couplings point to a picture where scalar soft SUSY breaking terms are related to the geography of fields in the compactified dimensions. Higgs fields and third generation scalars extend to the bulk and occur in split multiplets with TeV scale soft masses. First and second generation scalars, localized at orbifold fixed points or tori with enhanced symmetry, occur in complete GUT multiplets and have much larger masses. This picture can be matched onto the parameter space of generalized mirage mediation. Naturalness considerations, the requirement of the observed electroweak symmetry breaking pattern, and LHC bounds on m(gluino) together limit the gravitino mass to the $m_{3/2}~ 5-60$ TeV range. The mirage unification scale is bounded from below with the limit depending on the ratio of squark to gravitino masses. We show that while natural SUSY in this realization may escape detection even at the high luminosity LHC, the high energy LHC with $\sqrt{s}=33$ TeV could unequivocally confirm or exclude this scenario. It should be possible to detect the expected light higgsinos at the ILC if these are kinematically accessible, and possibly also discriminate the expected compression of gaugino masses in the natural mini-landscape picture from the mass pattern expected in models with gaugino mass unification. The thermal WIMP signal should be accessible via direct detection searches at the multi-ton noble liquid detectors such as Xenon-nT or LZ.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

One-loop free energy of tensionless type IIB string in AdS 5 ×S 5

Considering the zero ’t Hooft coupling limit of $\mathcal{N}$=4 super-Yang-Mills theory, the exact spectrum of all single-trace operators can be accessed in terms of the underlying so (2, 4) character. This makes it possible in turn to compute the one-loop free energy of the tensionless type IIB string theory in AdS 5 ×S 5 background, with help of the recently developed method of character integral representation of zeta function (CIRZ) . We calcu-late first the one-loop free energy of the string states in the ( p - 1)-th Regge trajectory and find the result to be p times the free energy of a single $\mathcal{N}$=4 Maxwell multiplet. The full one-loop free energy is hence proportional to the divergent series $\sum^{∞}_{p=2}p$. The divergence arises as a result of interrupting the regularization procedure in an intermediate stage. With a reorganization of states, we extract the finite part of free energy after summing over the Regge trajectories. This way gives us a finite result which is minus of the free energy of the $\mathcal{N}$=4 multiplet. Hence, this bulk one-loop result matches the -1 term in the N 2 - 1 factor of the boundary result.

1/N expansion↗
DOE OSTI2018

An infinite swampland of U(1) charge spectra in 6D supergravity theories

We analyze the anomaly constraints on 6D supergravity theories with a single abelian U(1) gauge factor. For theories with charges restricted to q = ±1, ±2 and no tensor multiplets, anomaly-free models match those models that can be realized from F-theory compactifications almost perfectly. For theories with tensor multiplets or with larger charges, the F-theory constraints are less well understood. We show, however, that there is an infinite class of distinct massless charge spectra in the “swampland” of theories that satisfy all known quantum consistency conditions but do not admit a realization through F-theory or any other known approach to string compactification. We also compare the spectra of charged matter in abelian theories with those that can be realized from breaking nonabelian SU(2) and higher rank gauge symmetries.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

High-temperature expansion of supersymmetric partition functions

Di Pietro and Komargodski have recently demonstrated a four-dimensional counterpart of Cardy’s formula, which gives the leading high-temperature (β → 0) behavior of supersymmetric partition functions Z SUSY (β). By focusing on superconformal theories, we elaborate on the subleading contributions to their formula when applied to free chiral and U(1) vector multiplets. In particular, we see that the high-temperature expansion of ln Z SUSY (β) terminates at order β 0 . We also demonstrate how their formula must be modified when applied to SU(N) toric quiver gauge theories in the planar (N → ∞) limit. Our method for regularizing the one-loop determinants of chiral and vector multiplets helps to clarify the relation between the 4d N=1 superconformal index and its corresponding supersymmetric partition function obtained by path-integration.

1/N Expansion↗
DOE OSTI2016

750 GeV diphotons: implications for supersymmetric unification II

Perturbative supersymmetric gauge coupling unification is possible in six theories where complete SU (5) TeV-scale multiplets of vector matter account for the size of the reported 750 GeV diphoton resonance, interpreted as a singlet multiplet S=(s+ia)/√2. One of these has a full generation of vector matter and a unified gauge coupling αG ~ 1. The diphoton signal rate is enhanced by loops of vector squarks and sleptons, especially when the trilinear A couplings are large. If the SH u H d coupling is absent, both s and a can contribute to the resonance, which may then have a large apparent width if the mass splitting from s and a arises from loops of vector matter. The width depends sensitively on A parameters and phases of the vector squark and slepton masses. Vector quarks and/or squarks are expected to be in reach of the LHC. If the SH u H d coupling is present, a leads to a narrow diphoton resonance, while a second resonance with decays s → hh, W + W – , ZZ is likely to be discovered at future LHC runs. In some of the theories a non-standard origin or running of the soft parameters is required, for example involving conformal hidden sector interactions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Carving out the end of the world or (superconformal bootstrap in six dimensions)

We bootstrap N=(1,0) superconformal field theories in six dimensions, by analyzing the four-point function of flavor current multiplets. By assuming E 8 flavor group, we present universal bounds on the central charge C T and the flavor central charge C J . Based on the numerical data, we conjecture that the rank-one E-string theory saturates the universal lower bound on C J , and numerically determine the spectrum of long multiplets in the rank-one E-string theory. We comment on the possibility of solving the higher-rank E-string theories by bootstrap and thereby probing M-theory on AdS 7 ×S 4 /Z 2 .

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Hamiltonian truncation study of supersymmetric quantum mechanics: S-matrix and metastable states

We implement the Rayleigh-Ritz method in supersymmetric quantum mechanics with flat directions, and extract the S-matrix and metastable resonances. The effectiveness of the method is demonstrated in two strongly coupled systems: an N = 1 toy supermembrane model, and an N = 4 model with a U(1) gauge multiplet and a charged chiral multiplet.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

T$ \overline{T} $ deformation in SCFTs and integrable supersymmetric theories

We calculate the \( \mathcal{S} \) -multiplets for two-dimensional Euclidean \( \mathcal{N} \) = (0 , 2) and \( \mathcal{N} \) = (2 , 2) superconformal field theories under the T \( \overline{T} \) deformation at leading order of perturbation theory in the deformation coupling. Then, from these \( \mathcal{N} \) = (0 , 2) deformed multiplets, we calculate two- and three-point correlators. We show the \( \mathcal{N} \) = (0 , 2) chiral ring’s elements do not flow under the T \( \overline{T} \) deformation. Specializing to integrable supersymmetric seed theories, such as \( \mathcal{N} \) = (2 , 2) Landau-Ginzburg models, we use the thermodynamic Bethe ansatz to study the S-matrices and ground state energies. From both an S-matrix perspective and Melzer’s folding prescription, we show that the deformed ground state energy obeys the inviscid Burgers’ equation. Finally, we show that several indices independent of D -term perturbations including the Witten index, Cecotti-Fendley-Intriligator-Vafa index and elliptic genus do not flow under the T \( \overline{T} \) deformation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Consistent truncations in higher derivative supergravity

We consider the torus reduction of heterotic supergravity in the presence of four-derivative corrections. In particular, the reduction on T n generically leads to a half-maximal supergravity coupled to n vector multiplets, and we show that it is consistent to truncate out said vector multiplets. This is done by the analysis of both the bosonic equations of motion and the Killing spinor equations. As an application of the consistent truncation, we examine the four-derivative corrected BPS black string that reduces to a black hole in minimal nine-dimensional supergravity.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Differential Many-Body Effects for Initial and Core Ionic States: Impact on XPS Spectra

In this paper, the contribution of many-body effects to the X-ray photoelectron spectroscopy, XPS, of an NO molecule is studied using wavefunction theory where the specific consequences of different many-body terms are examined and contrasted. It is shown that there is a differential importance of the many-body effects for the different configurations involved in the XPS. These are the ground, initial state configuration and final, N(1s) and O(1s) core hole ionic configurations. The consequences of the many-body effects are examined for the binding energies, BEs, to the two final state multiplets, triplet, and singlet, for each of the core ions and for the relative intensities of the XPS transitions to these multiplets. The many-body effects examined are those described as static effects that arise for individual terms that are important. The objective is to understand the chemical and physical origins that determine the importance of the correlation effects for the XPS, rather than to obtain very accurate predictions of the BEs. An important theoretical construct that is tested and justified is the equivalent core approximation where the core-ionized atom is replaced by the next higher element in the periodic table. This construct allows us to establish a correlation for the relative importance of the many-body effects in terms of effective charges of the different atoms. This is a correlation that has not been considered before and that we expect may have general relevance. The potential of the effects that we have identified for the XPS of NO to be relevant for the XPS of more complex, condensed phase systems is considered.

XPS, Static Correlation, Equivalent core model↗
DOE OSTI2023

Differentiating the bonding states in calcium carbonate polymorphs by low-loss electron-energy-loss spectroscopy

Calcium carbonate is one of the important building components in organisms, especially the two most common polymorphs, calcite and aragonite. Here, to understand the difference in bonding state, the two polymorphs are characterized by valence (low-loss) electron energy loss spectroscopy. It is found that the difference in Ca M 23 edge originating from 3p to 3d states is consistent with the change of Ca-O bonds in the two studied polymorphs. Surprisingly, the measured Ca M 23 edge is in qualitative agreement with the calculated partial density of states (PDOS) of Ca-d states in contrast to their L edges (from 2p to 3d states) which are strongly influenced by atomic multiplet effect (spin-orbit coupling). This is because the atomic multiplet effect is much reduced for the Ca 3p orbital, which permits the corresponding Ca M 23 edge to be compared with the PDOS results. Our findings show insights that PDOS can potentially be used to interpret the M 23 edge of lighter 3d transition metals such as scandium, titanium, vanadium and chromium when such interpretation may not be achieved for their L edges.

36 MATERIALS SCIENCE↗