5,203 research outputs found
Global Analysis of New Gravitational Singularities in String and Particle Theories
We present a global analysis of the geometries that arise in non-compact
current algebra (or gauged WZW) coset models of strings and particles
propagating in curved space-time. The simplest case is the 2d black hole. In
higher dimensions these geometries describe new and much more complex
singularities. For string and particle theories (defined in the text) we
introduce general methods for identifying global coordinates and give the
general exact solution for the geodesics for any gauged WZW model for any
number of dimensions. We then specialize to the 3d geometries associated with
(and also ) and discuss in detail the global
space, geodesics, curvature singularities and duality properties of this space.
The large-small (or mirror) type duality property is reformulated as an
inversion in group parameter space. The 3d global space has two topologically
distinct sectors, with patches of different sectors related by duality. The
first sector has a singularity surface with the topology of ``pinched double
trousers". It can be pictured as the world sheet of two closed strings that
join into a single closed string and then split into two closed strings, but
with a pinch in each leg of the trousers. The second sector has a singularity
surface with the topology of ``double saddle", pictured as the world sheets of
two infinite open strings that come close but do not touch. We discuss the
geodesicaly complete spaces on each side of these surfaces and interpret the
motion of particles in physical terms. A cosmological interpretation is
suggested and comments are mode on possible physical applications.Comment: 31 pages, plus 4 figure
Bondi-Sachs Energy-Momentum for the CMC Initial Value Problem
The constraints on the asymptotic behavior of the conformal factor and
conformal extrinsic curvature imposed by the initial value equations of general
relativity on constant mean extrinsic curvature (CMC) hypersurfaces are
analyzed in detail. We derive explicit formulas for the Bondi-Sachs energy and
momentum in terms of coefficients of asymptotic expansions on CMC hypersurfaces
near future null infinity. Precise numerical results for the Bondi-Sachs
energy, momentum, and angular momentum are used to interpret physically
Bowen-York solutions of the initial value equations on conformally flat CMC
hypersurfaces of the type obtained earlier by Buchman et al. [Phys. Rev. D
80:084024 (2009)].Comment: version to be published in Phys. Rev.
Semiotic modeling: relevance to trumpet performance and musical interpretation using Paul Hindemith\u27s Sonata for Trumpet and Piano
This paper is about the use of semiotics for the purpose of improving technical efficiency and musical interpretation in brass performance. Semiotics is the study of signs. The field is rooted in linguistics and logic, but has widened its influences to musicology and music theory in the last several decades. This paper constructs a model which simplifies music performance. The model has two components that address physical demands and musical analysis. The first component is a mathematically-based visual representation of the air stream used in brass performance. The second component of the model uses a reductive analysis. This analysis is the âroadmapâ for performance for the purpose of improving musical interpretation. The dual model of conceptualizing a work for performance will be applied to the first movement of Paul Hindemithâs Sonata for Trumpet and Piano
Sub-Surface Meridional flow, Vorticity and the life time of Solar Active Regions
Solar sub-surface fluid topology provides an indirect approach to examine the
internal characteristics of active regions (ARs). Earlier studies have revealed
the prevalence of strong flows in the interior of ARs having complex magnetic
fields. Using the Doppler data obtained by the Global Oscillation Network Group
(GONG) project for a sample of 74 ARs, we have discovered the presence of steep
gradients in meridional velocity at depths ranging from 1.5 to 5 Mm in flare
productive ARs. The sample of these ARs is taken from the Carrington rotations
1980--2052 covering the period August 2001-January 2007. The gradients showed
an interesting hemispheric trend of negative (positive) signs in the northern
(southern) hemisphere, i.e., directed toward the equator. We have discovered
three sheared layers in the depth range of 0 - 10 Mm, providing an evidence of
complex flow structures in several ARs. An important inference derived from our
analysis is that the location of the deepest zero vertical vorticity is
correlated with the remaining life time of ARs. This new finding may be
employed as a tool for predicting the life expectancy of an AR.Comment: 20 pages, 4 figures, To be appear in the Astrophysical Journal
Letter
A model for evaluation of selected compositions for unaccompanied solo trumpet according to criteria of serious artistic merit
This document presents a pilot study for evaluating the serious artistic merit of unaccompanied solo trumpet literature. The model for use in the study was derived from the efforts of two wind band literature researchers, Acton E. Ostling, Jr. and Jay W. Gilbert. Ostling wrote his dissertation in 1978 and Gilbert replicated and updated the research in 1993. The primary element of the Ostling and Gilbert studies was a carefully defined collection of ten criteria used to evaluate the quality of each work. A 5-point Likert scale was the unit of measurement. The outcome of this adaptation was a rank ordered list of unaccompanied solo trumpet works, which were judged to be works of serious artistic merit. 197 works were evaluated by sixteen evaluators and twenty-six works were judged to qualify as possessing serious artistic merit. One other element made this study unique. All the research occurred via the Internet. The panel, data presentation and data collection were completed through net resources. Analysis of the results suggested additional research that would function as a verification of evaluators\u27 results. It was determined that an analysis of several works, earning the label serious artistic merit, should be analyzed for structure and content to determine what characteristics were present that warranted the high rating they received. Three works were evaluated by a single person and received scores of 100%. After eliminating those three works, twenty-one works remained. A cursory survey of the scores revealed three works as having scores above 90%. I will provide further statistical analysis that demonstrates a significant difference between a score of 90% and scores above 90%. Based on the assumption that my statistical analysis is correct, the three works receiving additional analysis are Etude #2 - Du Style by Theo Charlier, Parable XIV by Vincent Persichetti and Solus by Stanley Friedman
Two Bipolar Outflows and Magnetic Fields in a Multiple Protostar System, L1448 IRS 3
We performed spectral line observations of CO J=2-1, 13CO J=1-0, and C18O
J=1-0 and polarimetric observations in the 1.3 mm continuum and CO J=2-1 toward
a multiple protostar system, L1448 IRS 3, in the Perseus molecular complex at a
distance of ~250 pc, using the BIMA array. In the 1.3 mm continuum, two sources
(IRS 3A and 3B) were clearly detected with estimated envelope masses of 0.21
and 1.15 solar masses, and one source (IRS 3C) was marginally detected with an
upper mass limit of 0.03 solar masses. In CO J=2-1, we revealed two outflows
originating from IRS 3A and 3B. The masses, mean number densities, momentums,
and kinetic energies of outflow lobes were estimated. Based on those estimates
and outflow features, we concluded that the two outflows are interacting and
that the IRS 3A outflow is nearly perpendicular to the line of sight. In
addition, we estimated the velocity, inclination, and opening of the IRS 3B
outflow using Bayesian statistics. When the opening angle is ~20 arcdeg, we
constrain the velocity to ~45 km/s and the inclination angle to ~57 arcdeg.
Linear polarization was detected in both the 1.3 mm continuum and CO J=2-1. The
linear polarization in the continuum shows a magnetic field at the central
source (IRS 3B) perpendicular to the outflow direction, and the linear
polarization in the CO J=2-1 was detected in the outflow regions, parallel or
perpendicular to the outflow direction. Moreover, we comprehensively discuss
whether the binary system of IRS 3A and 3B is gravitationally bound, based on
the velocity differences detected in 13CO J=1-0 and C18O J=1-0 observations and
on the outflow features. The specific angular momentum of the system was
estimated as ~3e20 cm^2/s, comparable to the values obtained from previous
studies on binaries and molecular clouds in Taurus.Comment: ApJ accepted, 20 pages, 2 tables, 10 figure
Measuring the dark matter equation of state
The nature of the dominant component of galaxies and clusters remains
unknown. While the astrophysics community supports the cold dark matter (CDM)
paradigm as a clue factor in the current cosmological model, no direct CDM
detections have been performed. Faber and Visser 2006 have suggested a simple
method for measuring the dark matter equation of state that combines kinematic
and gravitational lensing data to test the widely adopted assumption of
pressureless dark matter. Following this formalism, we have measured the dark
matter equation of state for first time using improved techniques. We have
found that the value of the equation of state parameter is consistent with
pressureless dark matter within the errors. Nevertheless, the measured value is
lower than expected because typically the masses determined with lensing are
larger than those obtained through kinematic methods. We have tested our
techniques using simulations and we have also analyzed possible sources of
error that could invalidate or mimic our results. In the light of this result,
we can now suggest that the understanding of the nature of dark matter requires
a complete general relativistic analysis.Comment: 4 pages, 2 figures, accepted for publication in Monthly Notices of
the Royal Astronomical Society Letters. Minor revision as suggested by
refere
Influence of wall vibrations on the sound of brass wind instruments
The results of an experimental and theoretical investigation of the influence of wall vibrations on the sound of brass wind instruments are presented. Measurements of the transmission function and input impedance of a trumpet, with the bell both heavily damped and freely vibrating, are shown to be consistent with a theory that assumes that the internal pressure causes an oscillation of the diameter of the pipe enclosing the air column. These effects are shown to be most significant in sections where there are flaring walls, which explains why damping these vibrations in cylindrical pipes normally produces no measurable effects
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