3,437 research outputs found
Analysis of a method for precisely relating a seafloor point to a distant point on land
A study of the environmental constraints and engineering aspects of the acoustic portion of a system for making geodetic ties between undersea reference points and others on land is described. Important areas in which to make such observations initially would be from the California mainland out to oceanic points seaward of the San Andreas fault, and across the Aleutian Trench. The overall approach would be to operate a GPS receiver in a relative positioning (interferometric) mode to provide the long range element of the baseline determination (10 to 1,000 km) and an array of precision sea floor acoustic transponders to link the locally moving sea surface GPS antenna location to a fixed sea floor point. Analyses of various environmental constrants (tides, waves, currents, sound velocity variations) lead to the conclusion that, if one uses a properly designed transponder having a remotely controllable precise retransmission time delay, and is careful with regard to methods for installing these on the sea floor, one should, in many ocean locations, be able to achieve sub-decimeter overall system accuracy. Achievements of cm accuracy or better will require additional understanding of time and space scales of variation of sound velocity structure in the ocean at relevant locations
Axial Anomaly from the BPHZ regularized BV master equation
A BPHZ renormalized form for the master equation of the field antifiled (or
BV) quantization has recently been proposed by De Jonghe, Paris and Troost.
This framework was shown to be very powerful in calculating gauge anomalies. We
show here that this equation can also be applied in order to calculate a global
anomaly (anomalous divergence of a classically conserved Noether current),
considering the case of QED. This way, the fundamental result about the
anomalous contribution to the Axial Ward identity in standard QED (where there
is no gauge anomaly) is reproduced in this BPHZ regularized BV framework.Comment: 10 pages, Latex, minor changes in the reference
Gauge dependence of effective action and renormalization group functions in effective gauge theories
The Caswell-Wilczek analysis on the gauge dependence of the effective action
and the renormalization group functions in Yang-Mills theories is generalized
to generic, possibly power counting non renormalizable gauge theories. It is
shown that the physical coupling constants of the classical theory can be
redefined by gauge parameter dependent contributions of higher orders in
in such a way that the effective action depends trivially on the gauge
parameters, while suitably defined physical beta functions do not depend on
those parameters.Comment: 13 pages Latex file, additional comments in section
Geometric representation of interval exchange maps over algebraic number fields
We consider the restriction of interval exchange transformations to algebraic
number fields, which leads to maps on lattices. We characterize
renormalizability arithmetically, and study its relationships with a
geometrical quantity that we call the drift vector. We exhibit some examples of
renormalizable interval exchange maps with zero and non-zero drift vector, and
carry out some investigations of their properties. In particular, we look for
evidence of the finite decomposition property: each lattice is the union of
finitely many orbits.Comment: 34 pages, 8 postscript figure
Higher-order non-symmetric counterterms in pure Yang-Mills theory
We analyze the restoration of the Slavnov-Taylor (ST) identities for pure
massless Yang-Mills theory in the Landau gauge within the BPHZL renormalization
scheme with IR regulator. We obtain the most general form of the action-like
part of the symmetric regularized action, obeying the relevant ST identities
and all other relevant symmetries of the model, to all orders in the loop
expansion. We also give a cohomological characterization of the fulfillment of
BPHZL IR power-counting criterion, guaranteeing the existence of the limit
where the IR regulator goes to zero. The technique analyzed in this paper is
needed in the study of the restoration of the ST identities for those models,
like the MSSM, where massless particles are present and no invariant
regularization scheme is known to preserve the full set of ST identities of the
theory.Comment: Final version published in the journa
Stickiness in Hamiltonian systems: from sharply divided to hierarchical phase space
We investigate the dynamics of chaotic trajectories in simple yet physically
important Hamiltonian systems with non-hierarchical borders between regular and
chaotic regions with positive measures. We show that the stickiness to the
border of the regular regions in systems with such a sharply divided phase
space occurs through one-parameter families of marginally unstable periodic
orbits and is characterized by an exponent \gamma= 2 for the asymptotic
power-law decay of the distribution of recurrence times. Generic perturbations
lead to systems with hierarchical phase space, where the stickiness is
apparently enhanced due to the presence of infinitely many regular islands and
Cantori. In this case, we show that the distribution of recurrence times can be
composed of a sum of exponentials or a sum of power-laws, depending on the
relative contribution of the primary and secondary structures of the hierarchy.
Numerical verification of our main results are provided for area-preserving
maps, mushroom billiards, and the newly defined magnetic mushroom billiards.Comment: To appear in Phys. Rev. E. A PDF version with higher resolution
figures is available at http://www.pks.mpg.de/~edugal
Gauge Consistent Wilson Renormalization Group I: Abelian Case
A version of the Wilson Renormalization Group Equation consistent with gauge
symmetry is presented. A perturbative renormalizability proof is established. A
wilsonian derivation of the Callan-Symanzik equation is given.Comment: Latex2e, 39 pages, 3 eps figures. Revised version to appear in Int.
J. Mod. Phy
Assessing Barriers among Primary Care Providers to Counseling Families about Obesity
Childhood obesity continues to be a major public health issue, and pediatric primary care providers could help address this epidemic. However, multiple factors may impact a provider's ability to address obesity, including practice level procedures and resources, individual attitudes and beliefs, and physician-patient communication skills. The purpose of this research project was to explore barriers and facilitators to childhood obesity counseling by primary care providers. In the first aim, a practice level environmental assessment tool was compared to chart reviews at eight practices and observations at four practices to assess the tool's ability to characterize and rank practice level support for body mass index (BMI) documentation, BMI communication, and practice level resources for healthy eating and physical activity. The assessment tool had good within-practice reliability (kappa=0.63) and good agreement with chart and observation data (percent agreement = 87-100; 50-100), respectively. The second aim used baseline survey data of providers' (N=123) attitudes, beliefs, and counseling frequency to determine the association between self-efficacy, outcome expectations, practice level support, and counseling frequency. Providers were confident/very confident (88.6%) in their ability to counsel about healthy eating, physical activity, and weight and agreed/strongly agreed (73.3%) that their counseling would result in actual changes. Providers with higher self-efficacy and outcome expectations were more likely (odds ratio=2.4; 2.2) to report providing obesity counseling. Practice level support was not associated with reported counseling frequency. For aim 3, focus groups were held with male caregivers to explore concerns and preferences when communicating with primary care providers about childhood obesity. The qualitative findings revealed that these fathers were involved in their children's healthcare and found doctors to be a helpful partner to keep their children healthy, yet they generally felt "left out" during appointments. The quality of the relationship with their children's doctor influenced how receptive fathers were to discussing their children's weight, diet, and physical activity behaviors. Fathers made suggestions to help improve communication between doctors and fathers, such as conveying a sense of respect, giving concrete examples on "how" to eat more healthfully and increase physical activity
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