2,113 research outputs found
Oscillatory approach to the singularity in vacuum symmetric spacetimes
A combination of qualitative analysis and numerical study indicates that
vacuum symmetric spacetimes are, generically, oscillatory.Comment: 2 pages submitted to the Ninth Marcel Grossmann Proceedings; v2, "all
known cases" changed to "various known cases" in the first paragrap
Near-Constant Mean Curvature Solutions of the Einstein Constraint Equations with Non-Negative Yamabe Metrics
We show that sets of conformal data on closed manifolds with the metric in
the positive or zero Yamabe class, and with the gradient of the mean curvature
function sufficiently small, are mapped to solutions of the Einstein constraint
equations. This result extends previous work which required the conformal
metric to be in the negative Yamabe class, and required the mean curvature
function to be nonzero.Comment: 15 page
General Relativity and Gravitation: A Centennial Perspective
To commemorate the 100th anniversary of general relativity, the International
Society on General Relativity and Gravitation (ISGRG) commissioned a Centennial
Volume, edited by the authors of this article. We jointly wrote introductions
to the four Parts of the Volume which are collected here. Our goal is to
provide a bird's eye view of the advances that have been made especially during
the last 35 years, i.e., since the publication of volumes commemorating
Einstein's 100th birthday. The article also serves as a brief preview of the 12
invited chapters that contain in-depth reviews of these advances. The volume
will be published by Cambridge University Press and released in June 2015 at a
Centennial conference sponsored by ISGRG and the Topical Group of Gravitation
of the American Physical Society.Comment: 37 page
Waveless Approximation Theories of Gravity
The analysis of a general multibody physical system governed by Einstein's
equations in quite difficult, even if numerical methods (on a computer) are
used. Some of the difficulties -- many coupled degrees of freedom, dynamic
instability -- are associated with the presence of gravitational waves. We have
developed a number of ``waveless approximation theories'' (WAT) which repress
the gravitational radiation and thereby simplify the analysis. The matter,
according to these theories, evolves dynamically. The gravitational field,
however, is determined at each time step by a set of elliptic equations with
matter sources. There is reason to believe that for many physical systems, the
WAT-generated system evolution is a very accurate approximation to that
generated by the full Einstein theory
A Conceptual Learner-Centered e-Learning Framework
e-Learning has increased rapidly in higher education. Most online education attempts to mirror the traditional face-to-face (FtF) classroom with less than favourable results. This paper proposes a conceptual e-learning framework based on andragogy theory, transformative learning theory, and media synchronicity theory. The conceptual e-learning framework supports the self-directed learning. e-learning based on this framework has the potential to out-perform not only current learning management systems such as Blackboard, but also traditional FtF learning for adult education and with different and better outcomes. Results of early testing of the concept showed increased learner’s online activity, innovation, and creativity
Andragogically Building a Doctor of Andragogy Program
Developing and implementing a Doctor of Andragogy Program andragogically provides an opportunity to ‘think outside the box’. It requires congruency between talking and action. Is this possible to accomplish? Stay tuned
Canonical Quantization Inside the Schwarzschild Black Hole
We propose a scheme for quantizing a scalar field over the Schwarzschild
manifold including the interior of the horizon. On the exterior, the timelike
Killing vector and on the horizon the isometry corresponding to restricted
Lorentz boosts can be used to enforce the spectral condition. For the interior
we appeal to the need for CPT invariance to construct an explicitly positive
definite operator which allows identification of positive and negative
frequencies. This operator is the translation operator corresponding to the
inexorable propagation to smaller radii as expected from the classical metric.
We also propose an expression for the propagator in the interior and express it
as a mode sum.Comment: 8 pages, LaTex. Title altered. One reference added. A few typos esp.
eq.(7),(38) corrected. To appear in Class.Q.Gra
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