175 research outputs found

    New Optimization Methods for Converging Perturbative Series with a Field Cutoff

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    We take advantage of the fact that in lambda phi ^4 problems a large field cutoff phi_max makes perturbative series converge toward values exponentially close to the exact values, to make optimal choices of phi_max. For perturbative series terminated at even order, it is in principle possible to adjust phi_max in order to obtain the exact result. For perturbative series terminated at odd order, the error can only be minimized. It is however possible to introduce a mass shift in order to obtain the exact result. We discuss weak and strong coupling methods to determine the unknown parameters. The numerical calculations in this article have been performed with a simple integral with one variable. We give arguments indicating that the qualitative features observed should extend to quantum mechanics and quantum field theory. We found that optimization at even order is more efficient that at odd order. We compare our methods with the linear delta-expansion (LDE) (combined with the principle of minimal sensitivity) which provides an upper envelope of for the accuracy curves of various Pade and Pade-Borel approximants. Our optimization method performs better than the LDE at strong and intermediate coupling, but not at weak coupling where it appears less robust and subject to further improvements. We also show that it is possible to fix the arbitrary parameter appearing in the LDE using the strong coupling expansion, in order to get accuracies comparable to ours.Comment: 10 pages, 16 figures, uses revtex; minor typos corrected, refs. adde

    Identifying barriers to accessing information and treatment for obstetric fistula in Niamey, Niger

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    Objective: To identify barriers to accessing information and treatment regarding obstetric fistula (OF) unique to Niger encountered by women referred to the National Referral Fistula Center. Method: A questionnaire was administered at the National Referral Fistula Center to 29 women with OF. Qualitative and quantitative statistics were computed. Results: The average individual was 30.4 years old, illiterate and from a rural area. 76.0% had antenatal care, the average labor time was 3.04 days, and 88.0% had a physician-assisted delivery. Barriers to information included rural dwelling, lack of education, lack of understanding of cause despite contact with health care workers, lack of knowledgeable resources to seek advice from or lack of ability/interest, not given specific information about availability of treatment, and not utilizing available resources to disseminate information. Barriers to treatment included lack of information regarding condition and treatment, traditional healer utilization, inability to access adequate care for condition, delay for childbirth recovery, permission needed to seek treatment, cost, timely treatment unavailable, and lack of social support. Conclusion: Improving efficiency of getting women to the hospital at time of delivery, prompt referrals for OF, and using cell phones for disseminating information or accessing transport may benefit women with OF in Niger

    Vaccine hesitancy and healthcare providers.

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    While most people vaccinate according to the recommended schedule, this success is challenged by individuals and groups who delay or refuse vaccines. The aim of this article is to review studies on vaccine hesitancy among healthcare providers (HCPs), and the influences of their own vaccine confidence and vaccination behaviour on their vaccination recommendations to others. The search strategy was developed in Medline and then adapted across several multidisciplinary mainstream databases including Embase Classic & Embase, and PschInfo. All foreign language articles were included if the abstract was available in English. A total of 185 articles were included in the literature review. 66% studied the vaccine hesitancy among HCPs, 17% analysed concerns, attitudes and/or behaviour of HCPs towards vaccinating others, and 9% were about evaluating intervention(s). Overall, knowledge about particular vaccines, their efficacy and safety, helped to build HCPs own confidence in vaccines and their willingness to recommend vaccines to others. The importance of societal endorsement and support from colleagues was also reported. In the face of emerging vaccine hesitancy, HCPs still remain the most trusted advisor and influencer of vaccination decisions. The capacity and confidence of HCPs, though, are stretched as they are faced with time constraints, increased workload and limited resources, and often have inadequate information or training support to address parents' questions. Overall, HCPs need more support to manage the quickly evolving vaccine environment as well as changing public, especially those who are reluctant or refuse vaccination. Some recommended strategies included strengthening trust between HCPs, health authorities and policymakers, through more shared involvement in the establishment of vaccine recommendations

    Phases of Chiral Gauge Theories

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    We discuss the behavior of two non-supersymmetric chiral SU(N) gauge theories, involving fermions in the symmetric and antisymmetric two-index tensor representations respectively. In addition to global anomaly matching, we employ a recently proposed inequality constraint on the number of effective low energy (massless) degrees of freedom of a theory, based on the thermodynamic free energy. Several possible zero temperature phases are consistent with the constraints. A simple picture for the phase structure emerges if these theories choose the phase, consistent with global anomaly matching, that minimizes the massless degree of freedom count defined through the free energy. This idea suggests that confinement with the preservation of the global symmetries through the formation of massless composite fermions is in general not preferred. While our discussion is restricted mainly to bilinear condensate formation, higher dimensional condensates are considered for one case. We conclude by commenting briefly on two related supersymmetric chiral theories.Comment: 23 pages, 2 figures, ReVTeX, improved forma

    D-type supersymmetry breaking and brane-to-brane gravity mediation

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    We revisit the issue of gravitational contributions to soft masses in five-dimensional sequestered models. We point out that, unlike for the case of F-type supersymmetry breaking, for D-type breaking these effects generically give positive soft masses squared for the sfermions. This drastically improves model building. We discuss the phenomenological implications of our result.Comment: 16 pages. Typos corrected, minor clarifications. To be published in Phys. Lett.

    Holomorphic Quantization on the Torus and Finite Quantum Mechanics

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    We construct explicitly the quantization of classical linear maps of SL(2,R)SL(2, R) on toroidal phase space, of arbitrary modulus, using the holomorphic (chiral) version of the metaplectic representation. We show that Finite Quantum Mechanics (FQM) on tori of arbitrary integer discretization, is a consistent restriction of the holomorphic quantization of SL(2,Z)SL(2, Z) to the subgroup SL(2,Z)/ΓlSL(2, Z)/\Gamma_l, Γl\Gamma_l being the principal congruent subgroup mod l, on a finite dimensional Hilbert space. The generators of the ``rotation group'' mod l, Ol(2)⊂SL(2,l)O_{l}(2)\subset SL(2,l), for arbitrary values of l are determined as well as their quantum mechanical eigenvalues and eigenstates.Comment: 12 pages LaTeX (needs amssymb.sty). Version as will appear in J. Phys.

    Bs→KℓνB_s \to K \ell\nu form factors with 2+1 flavors

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    Using the MILC 2+1 flavor asqtad quark action ensembles, we are calculating the form factors f0f_0 and f+f_+ for the semileptonic Bs→KℓνB_s \rightarrow K \ell\nu decay. A total of six ensembles with lattice spacing from ≈0.12\approx0.12 to 0.06 fm are being used. At the coarsest and finest lattice spacings, the light quark mass ml′m'_l is one-tenth the strange quark mass ms′m'_s. At the intermediate lattice spacing, the ratio ml′/ms′m'_l/m'_s ranges from 0.05 to 0.2. The valence bb quark is treated using the Sheikholeslami-Wohlert Wilson-clover action with the Fermilab interpretation. The other valence quarks use the asqtad action. When combined with (future) measurements from the LHCb and Belle II experiments, these calculations will provide an alternate determination of the CKM matrix element ∣Vub∣|V_{ub}|.Comment: 8 pages, 6 figures, to appear in the Proceedings of Lattice 2017, June 18-24, Granada, Spai

    Constructing Gauge Theory Geometries from Matrix Models

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    We use the matrix model -- gauge theory correspondence of Dijkgraaf and Vafa in order to construct the geometry encoding the exact gaugino condensate superpotential for the N=1 U(N) gauge theory with adjoint and symmetric or anti-symmetric matter, broken by a tree level superpotential to a product subgroup involving U(N_i) and SO(N_i) or Sp(N_i/2) factors. The relevant geometry is encoded by a non-hyperelliptic Riemann surface, which we extract from the exact loop equations. We also show that O(1/N) corrections can be extracted from a logarithmic deformation of this surface. The loop equations contain explicitly subleading terms of order 1/N, which encode information of string theory on an orientifolded local quiver geometry.Comment: 52 page

    B→Kl+l−B\to Kl^+l^- decay form factors from three-flavor lattice QCD

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    We compute the form factors for the B→Kl+l−B \to Kl^+l^- semileptonic decay process in lattice QCD using gauge-field ensembles with 2+1 flavors of sea quark, generated by the MILC Collaboration. The ensembles span lattice spacings from 0.12 to 0.045 fm and have multiple sea-quark masses to help control the chiral extrapolation. The asqtad improved staggered action is used for the light valence and sea quarks, and the clover action with the Fermilab interpretation is used for the heavy bb quark. We present results for the form factors f+(q2)f_+(q^2), f0(q2)f_0(q^2), and fT(q2)f_T(q^2), where q2q^2 is the momentum transfer, together with a comprehensive examination of systematic errors. Lattice QCD determines the form factors for a limited range of q2q^2, and we use the model-independent zz expansion to cover the whole kinematically allowed range. We present our final form-factor results as coefficients of the zz expansion and the correlations between them, where the errors on the coefficients include statistical and all systematic uncertainties. We use this complete description of the form factors to test QCD predictions of the form factors at high and low q2q^2. We also compare a Standard-Model calculation of the branching ratio for B→Kl+l−B \to Kl^+l^- with experimental data.Comment: V2: Fig.7 added. Typos text corrected. Reference added. Version published in Phys. Rev.
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