Geometrical optics for scalar, electromagnetic and gravitational waves in curved spacetime

The geometrical-optics expansion reduces the problem of solving wave equations to one of solving transport equations along rays. Here we consider scalar, electromagnetic and gravitational waves propagating on a curved spacetime in general relativity. We show that each is governed by a wave equation with the same principal part. It follows that: each wave propagates at the speed of light along rays (null generators of hypersurfaces of constant phase); the square of the wave amplitude varies in inverse proportion to the cross section of the beam; and the polarization is parallel-propagated along the ray (the Skrotskii/Rytov effect). We show that the optical scalars for a beam, and various Newman-Penrose scalars describing a parallel-propagated null tetrad, can be found by solving transport equations in a second-order formulation. Unlike the Sachs equations, this formulation makes it straightforward to find such scalars beyond the first conjugate point of a congruence, where neighbouring rays cross, and the scalars diverge. We discuss differential precession across the beam which leads to a modified phase in the geometrical-optics expansion.Comment: 17 pages, 1 figure. Proceedings for IV Amazonian Symposium on Physics, Belem, Brazil at UFPA on 18-22 Sep 201

Chemical accuracy from quantum Monte Carlo for the Benzene Dimer

We report an accurate study of interactions between Benzene molecules using variational quantum Monte Carlo (VMC) and diffusion quantum Monte Carlo (DMC) methods. We compare these results with density functional theory (DFT) using different van der Waals (vdW) functionals. In our QMC calculations, we use accurate correlated trial wave functions including three-body Jastrow factors, and backflow transformations. We consider two benzene molecules in the parallel displaced (PD) geometry, and find that by highly optimizing the wave function and introducing more dynamical correlation into the wave function, we compute the weak chemical binding energy between aromatic rings accurately. We find optimal VMC and DMC binding energies of -2.3(4) and -2.7(3) kcal/mol, respectively. The best estimate of the CCSD(T)/CBS limit is -2.65(2) kcal/mol [E. Miliordos et al, J. Phys. Chem. A 118, 7568 (2014)]. Our results indicate that QMC methods give chemical accuracy for weakly bound van der Waals molecular interactions, comparable to results from the best quantum chemistry methods.Comment: Accepted for publication in the Journal of Chemical Physics, Vol. 143, Issue 11, 201

Autonomous and Financial Mortgage Prepayment

Using individual data from Freddie Mac's portfolio of conventional mortgages, this paper estimates prepayment probabilities as a function of characteristics pertaining to the borrower, the loan, regional, and economic variables. Distinction is made between induced and autonomous prepayments. Based on the curvature of the underlying termination pattern, nonparametric methods are derived to estimate the prepayment probabilities and to predict a mortgage life under various scenarios. The findings point to a response asymmetry with respect to the level and trend of interest rates. Non-interest effects reveal the significance of the borrower's characteristics, property age, and regional mobility rates on mortgage termination.

Cross-modal associations in synaesthesia: vowel colours in the ear of the beholder

Human speech conveys many forms of information, but for some exceptional individuals (synaesthetes), listening to speech sounds can automatically induce visual percepts such as colours. In this experiment, grapheme–colour synaesthetes and controls were asked to assign colours, or shades of grey, to different vowel sounds. We then investigated whether the acoustic content of these vowel sounds influenced participants’ colour and grey-shade choices. We found that both colour and grey-shade associations varied systematically with vowel changes. The colour effect was significant for both participant groups, but significantly stronger and more consistent for synaesthetes. Because not all vowel sounds that we used are “translatable” into graphemes, we conclude that acoustic–phonetic influences co-exist with established graphemic influences in the cross-modal correspondences of both synaesthetes and non-synaesthetes

Tantilla oolitica

Number of Pages: 1Integrative BiologyGeological Science

Country of Origin Advertising and U.S. Wine Imports

The objective of this paper is to investigate the impact of media advertising on the US consumption of imported wine. A panel data of seven countries and twelve years from 1994-2005 is used to estimate the demand function for US wine imports. Our empirical analysis reveals evidence of strong price and advertising effects of domestic and imported wines on imported quantities; the advertising of imported wines significantly increases the quantity of imports while the advertising of domestic wines has a strong depressing effect on imported wine volumes. Our short-run import demand price and advertising elasticity estimates are -0.406 and 0.109 for imports and 0.654 and -0.370 for domestic wines, respectively. Other determinants such as population, real income and country specific fixed effects are also found significant. Based on our model estimates, we compute the marginal return to advertising to be $2.68 on average for the six importing countries and$3.40 for the U.S.International Relations/Trade, Marketing,

Neoseps and N. reynoldsi

Number of Pages: 2Integrative BiologyGeological Science