10,033 research outputs found

    Inequalities for electron-field correlation functions

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    I show that there exists a class of inequalities between correlation functions of different orders of a chaotic electron field. These inequalities lead to the antibunching effect and are a consequence of the fact that electrons are fermions -- indistinguishable particles with antisymmetric states. The derivation of the inequalities is based on the known form of the correlation functions for the chaotic state and on the properties of matrices and determinants.Comment: 8 pages Latex2e, 2 eps figure

    A Highly Consistent Framework for the Evolution of the Star-Forming "Main Sequence" from z~0-6

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    Using a compilation of 25 studies from the literature, we investigate the evolution of the star-forming galaxy (SFG) Main Sequence (MS) in stellar mass and star formation rate (SFR) out to z6z \sim 6. After converting all observations to a common set of calibrations, we find a remarkable consensus among MS observations (0.1\sim 0.1 dex 1σ\sigma interpublication scatter). By fitting for time evolution of the MS in bins of constant mass, we deconvolve the observed scatter about the MS within each observed redshift bins. After accounting for observed scatter between different SFR indicators, we find the width of the MS distribution is 0.2\sim 0.2 dex and remains constant over cosmic time. Our best fits indicate the slope of the MS is likely time-dependent, with our best fit logSFR(M,t)=(0.84±0.020.026±0.003×t)logM(6.51±0.240.11±0.03×t)\log\textrm{SFR}(M_*,t) = \left(0.84 \pm 0.02 - 0.026 \pm 0.003 \times t\right) \log M_* - \left(6.51 \pm 0.24 - 0.11 \pm 0.03 \times t\right), with tt the age of the Universe in Gyr. We use our fits to create empirical evolutionary tracks in order to constrain MS galaxy star formation histories (SFHs), finding that (1) the most accurate representations of MS SFHs are given by delayed-τ\tau models, (2) the decline in fractional stellar mass growth for a "typical" MS galaxy today is approximately linear for most of its lifetime, and (3) scatter about the MS can be generated by galaxies evolving along identical evolutionary tracks assuming an initial 1σ1\sigma spread in formation times of 1.4\sim 1.4 Gyr.Comment: 59 pages, 10 tables, 12 figures, accepted to ApJS; v2, slight changes to text, added new figure and fit

    A new proton fluence model for E greater than 10 MeV

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    Researchers describe a new engineering model for the fluence of protons with energies greater than 10 MeV. The data set used is a combination of observations made primarily from the Earth's surface between 1956 and 1963 and observations made from spacecraft in the vicinity of Earth between 1963 and 1985. With this data set we find that the distinction between ordinary proton events and anomalously large proton events made in earlier work disappears. The greater than 10 MeV fluences at 1 AU calculated with the new model are about twice those expected on the basis of models now in use. In contrast to earlier models, results do not depend critically on the fluence from any one event

    The Full Range of Predictions for B Physics From Iso-singlet Down Quark Mixing

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    We extend the range of predictions of the isosinglet (or vector) down quark model to the fully allowed physical ranges, and also update this with the effect of new physics constraints. We constrain the present allowed ranges of sin(2*beta) and sin(2*alpha), gamma, x_s, and A_{B_s}. In models allowing mixing to a new isosinglet down quark (as in E_6) flavor changing neutral currents are induced that allow a Z^0 mediated contribution to B-Bbar mixing and which bring in new phases. In (rho, eta), (x_s, sin(gamma)), and (x_s, A_{B_s}) plots for the extra isosinglet down quark model which are herein extended to the full physical range, we find new allowed regions that will require experiments on sin(gamma) and/or x_s to verify or to rule out an extra down quark contribution.Comment: 13 pages in RevTeX, 7 postscript figure

    Iso-singlet Down Quark Mixing And CP Violation Experiments

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    We confront the new physics models with extra iso-singlet down quarks in the new CP violation experimental era with sin(2β)\sin{(2\beta)} and ϵ/ϵ\epsilon'/\epsilon measurements, K+π+ννˉK^+ \to \pi^+ \nu \bar{\nu} events, and xsx_s limits. The closeness of the new experimental results to the standard model theory requires us to include full SM amplitudes in the analysis. In models allowing mixing to a new isosinglet down quark, as in E6_6, flavor changing neutral currents are induced that allow a Z0Z^0 mediated contribution to BBˉB-\bar B mixing and which bring in new phases. In (ρ,η)(\rho,\eta), (xs,sin(γ))(x_s,\sin{(\gamma)}), and (xs,sin(2ϕs))(x_s, \sin{(2\phi_s)}) plots we still find much larger regions in the four down quark model than in the SM, reaching down to η0\eta \approx 0, 0sin(γ)10 \leq \sin{(\gamma)} \leq 1, .75sin(2α)0.15-.75 \leq \sin{(2\alpha)} \leq 0.15, and sin(2ϕs)\sin{(2\phi_s)} down to zero, all at 1σ\sigma. We elucidate the nature of the cancellation in an order λ5\lambda^5 four down quark mixing matrix element which satisfies the experiments and reduces the number of independent angles and phases. We also evaluate tests of unitarity for the 3×33\times3 CKM submatrix.Comment: 14 pages, 16 figures, REVTeX

    Family support and cardiac rehabilitation: A comparative study of the experiences of South Asian and White-European patients and their carer's living in the United Kingdom

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    Background: Effective lifestyle modification facilitated by cardiac rehabilitation is known to reduce the occurrence of adverse coronary events and mortality. South Asians have poorer outcomes after a myocardial infarction than the general UK population, but little is known about their experiences of family support, cardiac rehabilitation and lifestyle change. Aims: To explore the nature of family support available to a sample of South Asian and White-European cardiac patients and to highlight similarities and differences between these groups with regard to cardiac rehabilitation and lifestyle modification. Methods: Using a qualitative approach, semi-structured interviews (in 1 of 6 languages) were conducted by researchers with; 45 South Asian patients and 37 carers and 20 White-European patients and 17 carers. Interviews were conducted in a home setting, up to eighteen months after discharge from hospital following myocardial infarction, coronary artery bypass surgery or unstable angina. Results: The main themes that emerged related to the provision of advice and information, family support and burden, dietary change and exercise regimes. Conclusions: Several cultural and ethnic differences were identified between patients and their families alongside similarities, irrespective of ethnicity. These may represent generic characteristics of recovery after a cardiac event. Health professionals should develop a cultural repertoire to engage with diversity and difference. Not every difficulty a person encounters as they try to access appropriate service delivery can be attributed to ethnic background. By improving services generally, support for South Asian populations can be improved. The challenge is to know when ethnicity makes a difference and mediates a person's relationship with service support and when it does not. (C) 2007 European Society of Cardiology. Published by Elsevier B.V. All rights reserved

    Constraining the Progenitor Companion of the Nearby Type Ia SN 2011fe with a Nebular Spectrum at +981 Days

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    We present an optical nebular spectrum of the nearby Type Ia supernova 2011fe, obtained 981 days after explosion. SN 2011fe exhibits little evolution since the +593 day optical spectrum, but there are several curious aspects in this new extremely late-time regime. We suggest that the persistence of the 5800\sim5800~\AA\ feature is due to Na I D, and that a new emission feature at 7300\sim7300~\AA\ may be [Ca II]. Also, we discuss whether the new emission feature at 6400\sim6400~\AA\ might be [Fe I] or the high-velocity hydrogen predicted by Mazzali et al. The nebular feature at 5200~\AA\ exhibits a linear velocity evolution of 350\sim350 km s1\rm km\ s^{-1} per 100 days from at least +220 to +980 days, but the line's shape also changes in this time, suggesting that line blending contributes to the evolution. At 1000\sim 1000 days after explosion, flux from the SN has declined to a point where contribution from a luminous secondary could be detected. In this work we make the first observational tests for a post-impact remnant star and constrain its temperature and luminosity to T104T \gtrsim 10^4 K\rm K and L104L \lesssim 10^4 L\rm L_{\odot}. Additionally, we do not see any evidence for narrow Hα\alpha emission in our spectrum. We conclude that observations continue to strongly exclude many single-degenerate scenarios for SN 2011fe.Comment: 11 pages, 10 figures, published by MNRA

    High-speed, high-frequency ultrasound, \u3ci\u3ein utero\u3c/i\u3e vector-flow imaging of mouse embryos

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    Real-time imaging of the embryonic murine cardiovascular system is challenging due to the small size of the mouse embryo and rapid heart rate. High-frequency, linear-array ultrasound systems designed for small-animal imaging provide high-frame-rate and Doppler modes but are limited in regards to the field of view that can be imaged at fine-temporal and -spatial resolution. Here, a plane-wave imaging method was used to obtain high-speed image data from in utero mouse embryos and multi-angle, vector-flow algorithms were applied to the data to provide information on blood flow patterns in major organs. An 18-MHz linear array was used to acquire plane-wave data at absolute frame rates ≥10 kHz using a set of fixed transmission angles. After beamforming, vector-flow processing and image compounding, effective frame rates were on the order of 2 kHz. Data were acquired from the embryonic liver, heart and umbilical cord. Vector-flow results clearly revealed the complex nature of blood-flow patterns in the embryo with fine-temporal and -spatial resolution

    Bundle Theory of Improper Spin Transformations

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    {\it We first give a geometrical description of the action of the parity operator (P^\hat{P}) on non relativistic spin 12{{1}\over{2}} Pauli spinors in terms of bundle theory. The relevant bundle, SU(2)Z2O(3)SU(2)\odot \Z_2\to O(3), is a non trivial extension of the universal covering group SU(2)SO(3)SU(2)\to SO(3). P^\hat{P} is the non relativistic limit of the corresponding Dirac matrix operator P=iγ0{\cal P}=i\gamma_0 and obeys P^2=1\hat{P}^2=-1. Then, from the direct product of O(3) by Z2\Z_2, naturally induced by the structure of the galilean group, we identify, in its double cover, the time reversal operator (T^\hat{T}) acting on spinors, and its product with P^\hat{P}. Both, P^\hat{P} and T^\hat{T}, generate the group Z4×Z2\Z_4 \times \Z_2. As in the case of parity, T^\hat{T} is the non relativistic limit of the corresponding Dirac matrix operator T=γ3γ1{\cal T}=\gamma^3 \gamma^1, and obeys T^2=1\hat{T}^2=-1.}Comment: 8 pages, Plaintex; titled changed, minor text modifications, one reference complete
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