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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 1,369 records · Page 76
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DOE OSTI2015

The bispectrum of cosmic string temperature fluctuations including recombination effects

We calculate the cosmic microwave background temperature bispectrum from cosmic strings, including the contributions from the last scattering surface, using a well-established Gaussian model for the string energy-momentum correlation functions, and a simplified model for the cosmic fluid. We check our approximation for the integrated Sachs-Wolfe (ISW) contribution against the bispectrum obtained from the full sky map of the cosmic string ISW signal used by the Planck team, obtaining good agreement. We validate our model for the last scattering surface contribution by comparing the predicted temperature power spectrum with that obtained from a full Boltzmann code treatment applied to the Unconnected Segment Model of a string network. We find that including the last scattering contribution has only a small impact on the upper limit on the string tension resulting from the bispectrum at Planck resolutions, and argue that the bispectrum is unlikely to be competitive with the power spectrum at any resolution.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Suppression of the long-wavelength CMB spectrum from the Hartle–Hawking wave function in the Starobinsky-type inflation model

The lack of correlations on the large scale cosmic microwave background (CMB) anisotropy provides a potential window to probe beyond the standard inflationary scenario. Herein, we investigate the primordial power spectrum based on the Hartle–Hawking (HH) no-boundary proposal for a homogeneous, isotropic, and spatially-closed universe that leads to Starobinsky-type inflation after the classicalization. While we found that there is no suppression at large scales in the standard $R+R^2$ theory, we also found that it is possible to sufficiently suppress the large-scale power spectrum if a pre-inflationary stage is introduced to the Starobinsky-type model. In addition, such a pre-inflationary stage will be helpful to explain the preference of large e-foldings of the $HH$ proposal. We calculate the $C^{TT}_{ℓ}$ correlation function and show that our proposal gives a better fit to the Planck CMB data. This suggests that our universe might have begun with a compact $HH$ state with a small positive curvature.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

CO{sub 2} isolated line shapes by classical molecular dynamics simulations: Influence of the intermolecular potential and comparison with new measurements

Room temperature absorption spectra of various transitions of pure CO{sub 2} have been measured in a broad pressure range using a tunable diode-laser and a cavity ring-down spectrometer, respectively, in the 1.6 μm and 0.8 μm regions. Their spectral shapes have been calculated by requantized classical molecular dynamics simulations. From the time-dependent auto-correlation function of the molecular dipole, including Doppler and collisional effects, spectral shapes are directly computed without the use of any adjusted parameter. Analysis of the spectra calculated using three different anisotropic intermolecular potentials shows that the shapes of pure CO{sub 2} lines, in terms of both the Lorentz widths and non-Voigt effects, slightly depend on the used potential. Comparisons between these ab initio calculations and the measured spectra show satisfactory agreement for all considered transitions (from J = 6 to J = 46). They also show that non-Voigt effects on the shape of CO{sub 2} transitions are almost independent of the rotational quantum number of the considered lines.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

A modal approach to the numerical calculation of primordial non-Gaussianities

We propose a new method to numerically calculate higher-order correlation functions of primordial fluctuations generated from any early-universe scenario. Our key-starting point is the realization that the tree-level In-In formalism is intrinsically separable. This enables us to use modal techniques to efficiently calculate and represent non-Gaussian shapes in a separable form well suited to data analysis. We prove the feasibility and the accuracy of our method by applying it to simple single-field inflationary models in which analytical results are available, and we perform non-trivial consistency checks like the verification of the single field consistency relation. We also point out that the iε prescription is automatically taken into account in our method, preventing the need for ad-hoc tricks to implement it numerically.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

MINUTE-SCALE RAPID VARIABILITY OF THE OPTICAL POLARIZATION IN THE NARROW-LINE SEYFERT 1 GALAXY PMN J0948+0022

We report on optical photopolarimetric results of the radio-loud narrow-line Seyfert 1 (RL-NLSy1) galaxy PMN J0948+0022 on 2012 December to 2013 February triggered by flux enhancements in the near infrared and γ-ray bands. With the one-shot polarimetry of the Hiroshima One-shot Wide field Polarimeter installed on the Kanata Telescope, we detected very rapid variability in the polarized-flux (PF) light curve on MJD 56281 (2012 December 20). The rise and decay times were about 140 s and 180 s, respectively. The polarization degree (PD) reached 36% ± 3% at the peak of the short-duration pulse, while the polarization angle remained almost constant. In addition, temporal profiles of the total flux and PD showed highly variable but well correlated behavior and discrete correlation function analysis revealed that no significant time lag of more than 10 minutes was present. The high PD and minute-scale variability in PF provides clear evidence of synchrotron radiation from a very compact emission region of ∼10{sup 14} cm size with a highly ordered magnetic field. Such micro-variability of polarization is also observed in several blazar jets, but its complex relation between total flux and PD are explained by a multi-zone model in several blazars. The implied single emission region in PMN J0948+0022 might reflect a difference of jets between RL-NLSy1s and blazars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Laser-Induced Phase Transition in a Monolayer of Polymer Particles Levitating in a Low-Pressure Gas-Discharge Plasma

We report on the results of analysis of the mean kinetic energy and the pair correlation function of polymer particles in a plasma–dust structure under the action of laser radiation. We have observed experimentally the crystal–liquid phase transition in the monolayer of particles levitating in the near-electrode layer of a capacitive high-frequency discharge. The coupling parameter of the dust system has been estimated. The results of analysis of the modification of the polymer dust particle surface after holding in the plasma are considered. We propose an explanation of the phase transition taking into account the role of the photophoretic force in the motion of macroparticles. The effect of the photophoretic force is associated with the modification of the dust particle surface in the plasma, as a result of which the particles can effectively absorb laser radiation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

The Detection and Characterization of Be+sdO Binaries from HST/STIS FUV Spectroscopy

The B emission-line stars are rapid rotators that were probably spun up by mass and angular momentum accretion through mass transfer in an interacting binary. Mass transfer will strip the donor star of its envelope to create a small and hot subdwarf remnant. Here we report on Hubble Space Telescope/STIS far-ultraviolet spectroscopy of a sample of Be stars that reveals the presence of the hot sdO companion through the calculation of cross-correlation functions of the observed and model spectra. We clearly detect the spectral signature of the sdO star in 10 of the 13 stars in the sample, and the spectral signals indicate that the sdO stars are hot, relatively faint, and slowly rotating as predicted by models. A comparison of their temperatures and radii with evolutionary tracks indicates that the sdO stars occupy the relatively long-lived, He-core burning stage. Only 1 of the 10 detections was a known binary prior to this investigation, which emphasizes the difficulty of finding such Be+sdO binaries through optical spectroscopy. However, these results and others indicate that many Be stars probably host hot subdwarf companions.

47 OTHER INSTRUMENTATION↗
DOE OSTI2015

MEASURING THE LUMINOSITY AND VIRIAL BLACK HOLE MASS DEPENDENCE OF QUASAR–GALAXY CLUSTERING AT z ∼ 0.8

We study the dependence of quasar clustering on quasar luminosity and black hole mass by measuring the angular overdensity of photometrically selected galaxies imaged by the Wide-field Infrared Survey Explorer (WISE) about z ∼ 0.8 quasars from SDSS. By measuring the quasar–galaxy cross-correlation function and using photometrically selected galaxies, we achieve a higher density of tracer objects and a more sensitive detection of clustering than measurements of the quasar autocorrelation function. We test models of quasar formation and evolution by measuring the luminosity dependence of clustering amplitude. We find a significant overdensity of WISE galaxies about z ∼ 0.8 quasars at 0.2–6.4 h{sup −1} Mpc in projected comoving separation. We find no appreciable increase in clustering amplitude with quasar luminosity across a decade in luminosity, and a power-law fit between luminosity and clustering amplitude gives an exponent of −0.01 ± 0.06 (1 σ error). We also fail to find a significant relationship between clustering amplitude and black hole mass, although our dynamic range in true mass is suppressed due to the large uncertainties in virial black hole mass estimates. Our results indicate that a small range in host dark matter halo mass maps to a large range in quasar luminosity.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Fitting methods for baryon acoustic oscillations in the Lyman-α forest fluctuations in BOSS data release 9

We describe fitting methods developed to analyze fluctuations in the Lyman-α forest and measure the parameters of baryon acoustic oscillations (BAO). We apply our methods to BOSS Data Release 9. Our method is based on models of the three-dimensional correlation function in physical coordinate space, and includes the effects of redshift-space distortions, anisotropic non-linear broadening, and broadband distortions. We allow for independent scale factors along and perpendicular to the line of sight to minimize the dependence on our assumed fiducial cosmology and to obtain separate measurements of the BAO angular and relative velocity scales. Our fitting software and the input files needed to reproduce our main BOSS Data Release 9 results are publicly available.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Anisotropic inflation reexamined: upper bound on broken rotational invariance during inflation

The presence of a light vector field coupled to a scalar field during inflation makes a distinct prediction: the observed correlation functions of the cosmic microwave background (CMB) become statistically anisotropic. We study the implications of the current bound on statistical anisotropy derived from the Planck 2013 CMB temperature data for such a model. The previous calculations based on the attractor solution indicate that the magnitude of anisotropy in the power spectrum is proportional to N{sup 2}, where N is the number of e-folds of inflation counted from the end of inflation. In this paper, we show that the attractor solution is not necessarily compatible with the current bound, and derive new predictions using another branch of anisotropic inflation. In addition, we improve upon the calculation of the mode function of perturbations by including the leading-order slow-roll corrections. We find that the anisotropy is roughly proportional to [2(ε{sub H}+4η{sub H})/3−4(c−1)]{sup −2}, where ε{sub H} and η{sub H} are the usual slow-roll parameters and c is the parameter in the model, regardless of the form of potential of an inflaton field. The bound from Planck implies that breaking of rotational invariance during inflation (characterized by the background homogeneous shear divided by the Hubble rate) is limited to be less than O(10{sup −9}). This bound is many orders of magnitude smaller than the amplitude of breaking of time translation invariance, which is observed to be O(10{sup −2})

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Measuring mode indices of a partially coherent vortex beam with Hanbury Brown and Twiss type experiment

It is known that the cross-correlation function (CCF) of a partially coherent vortex (PCV) beam shows a robust link with the radial and azimuthal mode indices. However, the previous proposals are difficult to measure the CCF in practical systems, especially in the case of astronomical objects. In this letter, we demonstrate experimentally that the Hanbury Brown and Twiss effect can be used to measure the mode indices of the original vortex beam and investigate the relationship between the spatial coherent width and the characterization of CCF of the PCV beam. The technique we exploit is quite efficient and robust, and it may be useful in the field of free space communication and astronomy which are related to the photon's orbital angular momentum.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

More on the new large D limit of matrix models

In this paper, we extend the recent analysis of the new large D limit of matrix models to the cases where the action contains arbitrary multi-trace interaction terms as well as to arbitrary correlation functions. We discuss both the cases of complex and Hermitian matrices, with U(N){sup 2}×O(D) and U(N)×O(D) symmetries respectively. In the latter case, the new large D limit is consistent for planar diagrams; at higher genera, it crucially requires the tracelessness condition. For similar reasons, the large N limit of tensor models with reduced symmetries is typically inconsistent already at leading order without the tracelessness condition. We also further discuss some interesting properties of purely bosonic models pointed out recently and explain that the standard argument predicting a non-trivial IR behavior in fermionic models à la SYK does not work for bosonic models. Finally, we explain that the new large D scaling is consistent with linearly realized supersymmetry.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

SOAP 2.0: a tool to estimate the photometric and radial velocity variations induced by stellar spots and plages

This paper presents SOAP 2.0, a new version of the Spot Oscillation And Planet (SOAP) code that estimates in a simple way the photometric and radial velocity (RV) variations induced by active regions. The inhibition of the convective blueshift (CB) inside active regions is considered, as well as the limb brightening effect of plages, a quadratic limb darkening law, and a realistic spot and plage contrast ratio. SOAP 2.0 shows that the activity-induced variation of plages is dominated by the inhibition of the CB effect. For spots, this effect becomes significant only for slow rotators. In addition, in the case of a major active region dominating the activity-induced signal, the ratio between the FWHM and the RV peak-to-peak amplitudes of the cross correlation function can be used to infer the type of active region responsible for the signal for stars with v sin i ≤8 km s{sup –1}. A ratio smaller than three implies a spot, while a larger ratio implies a plage. Using the observation of HD 189733, we show that SOAP 2.0 manages to reproduce the activity variation as well as previous simulations when a spot is dominating the activity-induced variation. In addition, SOAP 2.0 also reproduces the activity variation induced by a plage on the slowly rotating star α Cen B, which is not possible using previous simulations. Following these results, SOAP 2.0 can be used to estimate the signal induced by spots and plages, but also to correct for it when a major active region is dominating the RV variation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Cutoff AdS 3 versus the $ T\overline{T} $ deformation

A recent proposal relates two dimensional holographic conformal field theories deformed by the integrable $ T\overline{T} $ flow to AdS 3 with a finite radial cutoff. We investigate this proposal by studying perturbative correlation functions on the two sides. For low point correlators of the stress tensor, we successfully match the deformed CFT results at large central charge to bulk results obtained in classical pure gravity. Furthermore the deformed CFT also provides definite predictions for loop corrections in the bulk. We then include matter fields in the bulk. To reproduce the classical bulk two-point function of a scalar operator we show that the deformed CFT needs to be augmented with double trace scalar operators, with the $ T\overline{T} $ operator yielding corrections corresponding to loops in the bulk.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

REVERBERATION MAPPING OF A LOW-MASS BLACK HOLE IN A NARROW-LINE SEYFERT 1 GALAXY

We present results of a reverberation mapping (RM) campaign on the low black hole mass narrow-line Seyfert 1 (NLS1) galaxy SDSS J113913.91+335551.1 (hereafter SL01). Using the H{beta} measurements, we find a time lag {tau}= 12.5{sup +0.5}{sub -11} days and a broad-line velocity width of 1450 km s{sup -1} which implies a black hole mass of 3.8{sup +0.6}{sub -2.8} Multiplication-Sign 10{sup 6} M{sub Sun }. To further bolster our time lag results, we employ a secondary method based on the multivariate correlation function as described in Chelouche and Zucker, in which case we obtain consistent lags for the Balmer lines, yet without the need to spectrally deconvolve line from continuum emission processes. Given SL01's luminosity (L{sub bol} Almost-Equal-To 7 Multiplication-Sign 10{sup 43} erg s{sup -1}), we estimate an Eddington ratio (L{sub bol}/L{sub Edd}) of {approx}0.18. This fairly low-mass determination and rather high L{sub bol}/L{sub Edd} is consistent with the current paradigm that the nuclei of NLS1 galaxies host small black holes (as low as 10{sup 6} M{sub Sun }) with high accretion rates. SL01 is one of only a few NLS1s to date with robust RM results.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Consistency relation and non-Gaussianity in a Galileon inflation

We study a particular Galileon inflation in the light of Planck2015 observational data in order to constraint the model parameter space. We study the spectrum of the primordial modes of the density perturbations by expanding the action up to the second order in perturbations. Then we pursue by expanding the action up to the third order and find the three point correlation functions to find the amplitude of the non-Gaussianity of the primordial perturbations in this setup. We study the amplitude of the non-Gaussianity both in equilateral and orthogonal configurations and test the model with recent observational data. Our analysis shows that for some ranges of the non-minimal coupling parameter, the model is consistent with observation and it is also possible to have large non-Gaussianity which would be observable by future improvements in experiments. Moreover, we obtain the tilt of the tensor power spectrum and test the standard inflationary consistency relation ( r = −8 n {sub T} ) against the latest bounds from the Planck2015 dataset. We find a slight deviation from the standard consistency relation in this setup. Nevertheless, such a deviation seems not to be sufficiently remarkable to be detected confidently.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Reverberation Mapping of PG 0934+013 with the Southern African Large Telescope

We present the variability and time-lag measurements of PG 0934+013 based on a photometric and spectroscopic monitoring campaign over a two year period. We obtained 46 epochs of data from the spectroscopic campaign, which was carried out using the Southern African Large Telescope with ∼1 week cadence over two sets of four month-long observing period, while we obtained 80 epochs of B-band imaging data using a few 1 m class telescopes. Due to the seven month gap between the two observing periods, we separately measured the time lags of broad emission lines, including Hβ, by comparing the emission line light curve with the B-band continuum light curve using the cross-correlation function techniques. We determined the Hβ lag, τ{sub cent}=8.46{sub −2.14}{sup +2.08} days in the observed frame based on Year 2 data, while the time lag from Year 1 data was not reliably determined. Using the rms spectrum of Year 2 data, we measured the Hβ line dispersion σ{sub line} = 668 ± 44 km s{sup −1} after correcting for the spectral resolution. Adopting a virial factor f = 4.47 from Woo et al. (2015), we determined the black hole mass M {sub BH} = 3.13{sub −0.93}{sup +0.91}×10{sup 6} M {sub ⊙,} based on the Hβ time lag and velocity.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

The phase delay and its complex time: From stationary states up to wave packets

Complex time is often invoked about tunneling effect where the classical phase delay is completed with a crucial filter effect. Usually the complex times are obtained by considering the flux-flux correlation function, but this can be obtained by a very simple approach using the search of the maximum of the generalized complex phase function, including the amplitude of the wave function. Various aspects of the phase delay are presented in the case of wave packets impinging on simple or resonant quantum barriers. Formal links with the classical mechanics give birth to quasi-trajectories of the quantum particle, totally compatible with the quantum mechanics. - Highlights: Black-Right-Pointing-Pointer The stationary phase method is extended in including the variations of the spectra. Black-Right-Pointing-Pointer The complex phase delay leads to a complex trajectory inside and out-side the barrier. Black-Right-Pointing-Pointer Examples of quasi-trajectories are given in case of different quantum barriers. Black-Right-Pointing-Pointer Phase delays are specified for resonant tunneling or above-barrier wave-packets. Black-Right-Pointing-Pointer The coherence between the quasi-trajectories and quantum mechanics is shown.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗