7,080 research outputs found
Evidence Against an Association Between Gamma-Ray Bursts and Type I Supernovae
We present a rigorous method, based on Bayesian inference, for calculating
the odds favoring the hypothesis that any particular class of astronomical
transients produce gamma-ray bursts over the hypothesis that they do not. We
then apply this method to a sample of 83 Type Ia supernovae and a sample of 20
Type Ib-Ic supernovae. We find overwhelming odds against the hypothesis that
all Type Ia supernovae produce gamma-ray bursts, whether at low redshift
() or high-redshift (), and very large odds ()
against the hypothesis that all Type Ib, Ib/c, and Ic supernovae produce
observable gamma-ray bursts. We find large odds () against the hypothesis
that a fraction of Type Ia supernovae produce observable gamma-ray bursts, and
moderate odds () against the hypothesis that a fraction of Type Ib-Ic
supernovae produce observable bursts. We have also re-analyzed both a corrected
version of the Wang & Wheeler sample of Type Ib-Ic SNe and our larger sample of
20 Type Ib-Ic SNe, using a generalization of their frequentist method. We find
no significant evidence in either case of a correlation between Type Ib-Ic SNe
and GRBs, consistent with the very strong evidence against such a correlation
that we find from our Bayesian analysis.Comment: 45 pages, 2 PostScript figures. Uses AASTEX macros. Submitted to The
Astrophysical Journa
Magnetic-Moment Fragmentation and Monopole Crystallization
The Coulomb phase, with its dipolar correlations and pinch-point-scattering
patterns, is central to discussions of geometrically frustrated systems, from
water ice to binary and mixed-valence alloys, as well as numerous examples of
frustrated magnets. The emergent Coulomb phase of lattice-based systems has
been associated with divergence-free fields and the absence of long-range
order. Here, we go beyond this paradigm, demonstrating that a Coulomb phase can
emerge naturally as a persistent fluctuating background in an otherwise ordered
system. To explain this behavior, we introduce the concept of the fragmentation
of the field of magnetic moments into two parts, one giving rise to a magnetic
monopole crystal, the other a magnetic fluid with all the characteristics of an
emergent Coulomb phase. Our theory is backed up by numerical simulations, and
we discuss its importance with regard to the interpretation of a number of
experimental results
The Influences of Buddhism and Development on the Well-Being of Bhutan\u27s Street Dogs
Bhutan is the only country that has implemented a nationwide capture-neuter- vaccinate-release (CNVR) program to manage its street dog population. To explore motivations for the implementation of the program and the extent to which it is successful, face-to-face interviews were conducted with representatives of all three animal sanctuaries in Bhutan that focus on the well-being of street dogs. Results suggest that Bhutan’s transition to democracy, coinciding with increases in socioeconomic development and tourism from the West, and incorporation of Buddhist teachings in its consideration of street dog management strategies guided the implementation of a nationwide CNVR program. A lack of both resources and a plan to acquire them, along with inexperience with democratic practices, however, may interfere with successful management of the program, resulting in a growing street dog population. Development in Bhutan also poses risks to the well-being of street dogs
"Quantum Interference with Slits" Revisited
Marcella [arXiv:quant-ph/0703126] has presented a straightforward technique
employing the Dirac formalism to calculate single- and double-slit interference
patterns. He claims that no reference is made to classical optics or scattering
theory and that his method therefore provides a purely quantum mechanical
description of these experiments. He also presents his calculation as if no
approximations are employed. We show that he implicitly makes the same
approximations found in classical treatments of interference and that no new
physics has been introduced. At the same time, some of the quantum mechanical
arguments Marcella gives are, at best, misleading.Comment: 11 pages, 3 figure
Visualizing the logistic map with a microcontroller
The logistic map is one of the simplest nonlinear dynamical systems that
clearly exhibit the route to chaos. In this paper, we explored the evolution of
the logistic map using an open-source microcontroller connected to an array of
light emitting diodes (LEDs). We divided the one-dimensional interval
into ten equal parts, and associated and LED to each segment. Every time an
iteration took place a corresponding LED turned on indicating the value
returned by the logistic map. By changing some initial conditions of the
system, we observed the transition from order to chaos exhibited by the map.Comment: LaTeX, 6 pages, 3 figures, 1 listin
Partner choice, relationship satisfaction, and oral contraception: the congruency hypothesis
Hormonal fluctuation across the menstrual cycle explains temporal variation in women’s judgment of the attractiveness of members of the opposite sex. Use of hormonal contraceptives could therefore influence both initial partner choice and, if contraceptive use subsequently changes, intrapair dynamics. Associations between hormonal contraceptive use and relationship satisfaction may thus be best understood by considering whether current use is congruent with use when relationships formed, rather than by considering current use alone. In the study reported here, we tested this congruency hypothesis in a survey of 365 couples. Controlling for potential confounds (including relationship duration, age, parenthood, and income), we found that congruency in current and previous hormonal contraceptive use, but not current use alone, predicted women’s sexual satisfaction with their partners. Congruency was not associated with women’s nonsexual satisfaction or with the satisfaction of their male partners. Our results provide empirical support for the congruency hypothesis and suggest that women’s sexual satisfaction is influenced by changes in partner preference associated with change in hormonal contraceptive use
Simple Pendulum Revisited
We describe a 8085 microprocessor interface developed to make reliable time
period measurements. The time period of each oscillation of a simple pendulum
was measured using this interface. The variation of the time period with
increasing oscillation was studied for the simple harmonic motion (SHM) and for
large angle initial displacements (non-SHM). The results underlines the
importance of the precautions which the students are asked to take while
performing the pendulum experiment.Comment: 17 pages with 10 figure
The motion of two masses coupled to a massive spring
We discuss the classical motion of a spring of arbitrary mass coupled to two
arbitrary massive blocks attached at its ends. A general approach to the
problem is presented and some general results are obtained. Examples for which
a simple elastic function can be inferred are discussed and the normal modes
and normal frequencies obtained. An approximation procedure to the evaluation
of the normel frequencies in the case of uniform elastic function and mass
density is also discussed.Comment: Standard Latex file plus three eps figure
Poynting's theorem for planes waves at an interface: a scattering matrix approach
We apply the Poynting theorem to the scattering of monochromatic
electromagnetic planes waves with normal incidence to the interface of two
different media. We write this energy conservation theorem to introduce a
natural definition of the scattering matrix S. For the dielectric-dielectric
interface the balance equation lead us to the energy flux conservation which
express one of the properties of S: it is a unitary matrix. For the
dielectric-conductor interface the scattering matrix is no longer unitary due
to the presence of losses at the conductor. However, the dissipative term
appearing in the Poynting theorem can be interpreted as a single absorbing mode
at the conductor such that a whole S, satisfying flux conservation and
containing this absorbing mode, can be defined. This is a simplest version of a
model introduced in the current literature to describe losses in more complex
systems.Comment: 5 pages, 3 figures, submitted to Am. J. Phy
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