31 research outputs found

    Transplanckian axions !?

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    We discuss quantum gravitational effects in Einstein theory coupled to periodic axion scalars to analyze the viability of several proposals to achieve superplanckian axion periods (aka decay constants) and their possible application to large field inflation models. The effects we study correspond to the nucleation of euclidean gravitational instantons charged under the axion, and our results are essentially compatible with (but independent of) the Weak Gravity Conjecture, as follows: Single axion theories with superplanckian periods contain gravitational instantons inducing sizable higher harmonics in the axion potential, which spoil superplanckian inflaton field range. A similar result holds for multi-axion models with lattice alignment (like the Kim-Nilles-Peloso model). Finally, theories with NN axions can still achieve a moderately superplanckian periodicity (by a N\sqrt{N} factor) with no higher harmonics in the axion potential. The Weak Gravity Conjecture fails to hold in this case due to the absence of some instantons, which are forbidden by a discrete ZN\mathbf{Z}_N gauge symmetry. Finally we discuss the realization of these instantons as euclidean D-branes in string compactifications.Comment: 46 pages, 6 figures. Added references, clarifications, and missing factor of 1/2 to instanton action. Conclusions unchange

    The Relative Role of Perceived Partner Risks in Promoting Condom Use in a Three-City Sample of High-Risk, Low-Income Women

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    We examined the effect of women’s perceptions of sexual partner risks on condom use. Women from three US cities (n = 1,967) were recruited to provide data on HIV risks. In univariate models, increased odds of condom use were associated with perceiving that partners had concurrent partners and being unaware of partners': (a) HIV status, (b) bisexuality, (c) concurrency; and/or (d) injection drug use. In multivariate models, neither being unaware of the four partner risk factors nor perceiving a partner as being high risk was associated with condom use. Contextual factors associated with decreased odds of condom use were having sex with a main partner, homelessness in the past year, alcohol use during sex, and crack use in the past 30 days. Awareness of a partner’s risks may not be sufficient for increasing condom use. Contextual factors, sex with a main partner in particular, decrease condom use despite awareness of partner risk factors

    Measurement of the rate of nu(e) + d --> p + p + e(-) interactions produced by (8)B solar neutrinos at the Sudbury Neutrino Observatory.

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    Solar neutrinos from (8)B decay have been detected at the Sudbury Neutrino Observatory via the charged current (CC) reaction on deuterium and the elastic scattering (ES) of electrons. The flux of nu(e)'s is measured by the CC reaction rate to be straight phi(CC)(nu(e)) = 1.75 +/- 0.07(stat)(+0.12)(-0.11)(syst) +/- 0.05(theor) x 10(6) cm(-2) s(-1). Comparison of straight phi(CC)(nu(e)) to the Super-Kamiokande Collaboration's precision value of the flux inferred from the ES reaction yields a 3.3 sigma difference, assuming the systematic uncertainties are normally distributed, providing evidence of an active non- nu(e) component in the solar flux. The total flux of active 8B neutrinos is determined to be 5.44+/-0.99 x 10(6) cm(-2) s(-1)

    Beyond implicit prices: recovering theoretically consistent and transferable values for noise avoidance from a hedonic property price model

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    Using a two-stage hedonic pricing methodology we estimate a system of structural demand equations for different sources of transport-related noise. In the first stage, we identify market segments using model-based clustering techniques and estimate separate hedonic price functions (HPFs) for each segment. In so doing, we show how a semiparametric spatial smoothing estimator outperforms other standard specifications of the HPF. In the second stage, we control for non-linearity of the budget constraint and identify demand relationships using techniques that account for problems of endogeneity and censoring of the dependent variable. Our estimated demand functions provide welfare estimates for peace and quiet that we believe to be the first derived from property market data in a theoretically consistent manner
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