Nonperturbative m_X cut effects in B -> Xs l+ l- observables

Recently, it was shown that in inclusive B -> Xs l+ l- decay, an angular decomposition provides three independent (q^2 dependent) observables. A strategy was formulated to extract all measurable Wilson coefficients in B -> Xs l+ l- from a few simple integrals of these observables in the low q^2 region. The experimental measurements in the low q^2 region require a cut on the hadronic invariant mass, which introduces a dependence on nonperturbative b quark distribution functions. The associated hadronic uncertainties could potentially limit the sensitivity of these decays to new physics. We compute the nonperturbative corrections to all three observables at leading and subleading order in the power expansion in \Lambda_QCD/m_b. We find that the subleading power corrections give sizeable corrections, of order -5% to -10% depending on the observable and the precise value of the hadronic mass cut. They cause a shift of order -0.05 GeV^2 to -0.1 GeV^2 in the zero of the forward-backward asymmetry.Comment: 11 pages, 4 figures, v2: corrected typos and Eq. (25), v3: journal versio

Treatment of Ligament Constructs with Exercise-conditioned Serum: A Translational Tissue Engineering Model.

In vitro experiments are essential to understand biological mechanisms; however, the gap between monolayer tissue culture and human physiology is large, and translation of findings is often poor. Thus, there is ample opportunity for alternative experimental approaches. Here we present an approach in which human cells are isolated from human anterior cruciate ligament tissue remnants, expanded in culture, and used to form engineered ligaments. Exercise alters the biochemical milieu in the blood such that the function of many tissues, organs and bodily processes are improved. In this experiment, ligament construct culture media was supplemented with experimental human serum that has been 'conditioned' by exercise. Thus the intervention is more biologically relevant since an experimental tissue is exposed to the full endogenous biochemical milieu, including binding proteins and adjunct compounds that may be altered in tandem with the activity of an unknown agent of interest. After treatment, engineered ligaments can be analyzed for mechanical function, collagen content, morphology, and cellular biochemistry. Overall, there are four major advantages versus traditional monolayer culture and animal models, of the physiological model of ligament tissue that is presented here. First, ligament constructs are three-dimensional, allowing for mechanical properties (i.e., function) such as ultimate tensile stress, maximal tensile load, and modulus, to be quantified. Second, the enthesis, the interface between boney and sinew elements, can be examined in detail and within functional context. Third, preparing media with post-exercise serum allows for the effects of the exercise-induced biochemical milieu, which is responsible for the wide range of health benefits of exercise, to be investigated in an unbiased manner. Finally, this experimental model advances scientific research in a humane and ethical manner by replacing the use of animals, a core mandate of the National Institutes of Health, the Center for Disease Control, and the Food and Drug Administration

Secret Spending in the States

Six years after Citizens United enabled unfettered spending in our elections, the use of so-called dark money has become disturbingly common. Contrary to the Supreme Court's assumption that this unlimited spending would be transparent to voters, at the federal level powerful groups have since 2010 poured hundreds of millions of dollars into influencing elections while obscuring the sources of their funding. But it is at the state and local levels that secret spending is arguably at its most damaging. For a clear understanding of the degree to which dark money is warping American democracy, state ballot referenda and local school board contests may be a better starting point than the presidential campaign or even congressional races. As Chris Herstam, a former Republican majority whip in the Arizona House of Representatives and now lobbyist, put it, "In my 33 years in Arizona politics and government, dark money is the most corrupting influence I have seen."This report documents how far outside spending -- election spending that is not coordinated with candidates -- at the state and local levels has veered from the vision of democratic transparency the Citizens United Court imagined, drawing on an extensive database of news accounts, interviews with a range of stakeholders, campaign finance and tax records, court cases, and social science research. For the first time, it also measures changes in dark money – and a thus far unrecognized rise in what we term "gray money" – at the state level, by analyzing spender and contributor reports in six of nine states where sufficient usable data were available. This set of six geographically and demographically diverse states, comprising Alaska, Arizona, California, Colorado, Maine, and Massachusetts, represents approximately 20 percent of the nation's population.

Quantum Algorithms for Fermionic Quantum Field Theories

Extending previous work on scalar field theories, we develop a quantum algorithm to compute relativistic scattering amplitudes in fermionic field theories, exemplified by the massive Gross-Neveu model, a theory in two spacetime dimensions with quartic interactions. The algorithm introduces new techniques to meet the additional challenges posed by the characteristics of fermionic fields, and its run time is polynomial in the desired precision and the energy. Thus, it constitutes further progress towards an efficient quantum algorithm for simulating the Standard Model of particle physics.Comment: 29 page

Quantum Algorithms for Quantum Field Theories

Quantum field theory reconciles quantum mechanics and special relativity, and plays a central role in many areas of physics. We develop a quantum algorithm to compute relativistic scattering probabilities in a massive quantum field theory with quartic self-interactions (phi-fourth theory) in spacetime of four and fewer dimensions. Its run time is polynomial in the number of particles, their energy, and the desired precision, and applies at both weak and strong coupling. In the strong-coupling and high-precision regimes, our quantum algorithm achieves exponential speedup over the fastest known classical algorithm.Comment: v2: appendix added (15 pages + 25-page appendix

Quantum Computation of Scattering in Scalar Quantum Field Theories

Quantum field theory provides the framework for the most fundamental physical theories to be confirmed experimentally, and has enabled predictions of unprecedented precision. However, calculations of physical observables often require great computational complexity and can generally be performed only when the interaction strength is weak. A full understanding of the foundations and rich consequences of quantum field theory remains an outstanding challenge. We develop a quantum algorithm to compute relativistic scattering amplitudes in massive phi-fourth theory in spacetime of four and fewer dimensions. The algorithm runs in a time that is polynomial in the number of particles, their energy, and the desired precision, and applies at both weak and strong coupling. Thus, it offers exponential speedup over existing classical methods at high precision or strong coupling

Gauge drivers for the generalized harmonic Einstein equations

The generalized harmonic representation of Einstein's equations is manifestly hyperbolic for a large class of gauge conditions. Unfortunately most of the useful gauges developed over the past several decades by the numerical relativity community are incompatible with the hyperbolicity of the equations in this form. This paper presents a new method of imposing gauge conditions that preserves hyperbolicity for a much wider class of conditions, including as special cases many of the standard ones used in numerical relativity: e.g., K freezing, Gamma freezing, Bona-Massó slicing, conformal Gamma drivers, etc. Analytical and numerical results are presented which test the stability and the effectiveness of this new gauge-driver evolution system

Social Networking Sites and Our Lives

Examines the characteristics of social networking site users, their online activities, and their friendships, sense of trust, social support, perspectives, and civic engagement by site and compared with those of non-users and users of other technologies

Why Most Facebook Users Get More Than They Give

Analyzes data on Facebook user activity, including patterns in sending friend requests, adding content, and "liking" their friends' content; the interconnectedness of friends; and links between the number of friends, Facebook activity, and social support