4,648 research outputs found
Ghosts of the Revolution: Abraham Lincoln, Jefferson Davis, and the Legacy of the Founding Generation
For the wartime generation, the Civil War in many ways represented a recapitulation of the American Revolution. Both the Union and Confederate civilian populations viewed themselves as the true successors of the Founding Generation. Throughout the Antebellum years and the Civil War, Abraham Lincoln and Jefferson Davis frequently invoked the Founders and their legacy. The two future executives did so in order to both justify their own political ideologies as well as inspire their respective civilian populations. Their sense of ownership over the legacy of the Founders reflected one of the uniquely American conflicts of the Civil War Era
And what if gravity is intrinsically quantic ?
Since the early days of search for a quantum theory of gravity the attempts
have been mostly concentrated on the quantization of an otherwise classical
system. The two most contentious candidate theories of gravity, sting theory
and quantum loop gravity are based on a quantum field theory - the latter is a
quantum field theory of connections on a SU(2) group manifold and former a
quantum field theory in two dimensional spaces. Here we argue that there is a
very close relation between quantum mechanics and gravity. Without gravity
quantum mechanics becomes ambiguous. We consider this observation as the
evidence for an intrinsic relation between these fundamental laws of nature. We
suggest a quantum role and definition for gravity in the context of a quantum
universe, and present a preliminary formulation for gravity in a system with a
finite number of particles.Comment: 8 pages, 1 figure. To appear in the proceedings of the DICE2008
conference, Castiglioncello, Tuscany, Italy, 22-26 Sep. 2008. V2: some typos
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Conservation of the stress tensor in perturbative interacting quantum field theory in curved spacetimes
We propose additional conditions (beyond those considered in our previous
papers) that should be imposed on Wick products and time-ordered products of a
free quantum scalar field in curved spacetime. These conditions arise from a
simple ``Principle of Perturbative Agreement'': For interaction Lagrangians
that are such that the interacting field theory can be constructed
exactly--as occurs when is a ``pure divergence'' or when is at most
quadratic in the field and contains no more than two derivatives--then
time-ordered products must be defined so that the perturbative solution for
interacting fields obtained from the Bogoliubov formula agrees with the exact
solution. The conditions derived from this principle include a version of the
Leibniz rule (or ``action Ward identity'') and a condition on time-ordered
products that contain a factor of the free field or the free
stress-energy tensor . The main results of our paper are (1) a proof
that in spacetime dimensions greater than 2, our new conditions can be
consistently imposed in addition to our previously considered conditions and
(2) a proof that, if they are imposed, then for {\em any} polynomial
interaction Lagrangian (with no restriction on the number of derivatives
appearing in ), the stress-energy tensor of the interacting
theory will be conserved. Our work thereby establishes (in the context of
perturbation theory) the conservation of stress-energy for an arbitrary
interacting scalar field in curved spacetimes of dimension greater than 2. Our
approach requires us to view time-ordered products as maps taking classical
field expressions into the quantum field algebra rather than as maps taking
Wick polynomials of the quantum field into the quantum field algebra.Comment: 88 pages, latex, no figures, v2: changes in the proof of proposition
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Lead telluride bonding and segmentation study Semiannual phase report, Aug. 1, 1967 - Jan. 31, 1968
Constitutional studies of SnTe and Si-Ge metal systems, segmented Si-Ge-PdTe thermocouple efficiencies, and pore migration in PbSnTe thermoelement
Lead telluride bonding and segmentation study Semiannual phase report, 1 Aug. 1969 - 31 Jan. 1970
Metallurgical studies of eutectic alloys suitable for brazing MoSi2 to Si-Ge thermoelectric materia
Lead telluride bonding and segmentation study Interim report, 1 Nov. 1966 - 31 Jul. 1967
Lead telluride bonding and segmentation studies including couple design, test devices, and life testin
Cosmological particle creation in states of low energy
The recently proposed states of low energy provide a well-motivated class of
reference states for the quantized linear scalar field on cosmological
Friedmann-Robertson-Walker spacetimes. The low energy property of a state is
localized close to some value of the cosmological time coordinate. We present
calculations of the relative cosmological particle production between a state
of low energy at early time and another such state at later time. In an
exponentially expanding Universe, we find that the particle production shows
oscillations in the spatial frequency modes. The basis of the method for
calculating the relative particle production is completely rigorous.
Approximations are only used at the level of numerical calculation.Comment: 24 pages, 7 figure
Development of single crystal beta-alumina membrane
Feasibility of crystal growth technique for beta alumina membrane from molybdenum, tungsten, and iridiu
Thick film silicon growth techniques
Silicon ribbon growth experiments were conducted using orifices (dies) fabricated from SiC-SiO2 mixtures, fused quartz, SiC, and fine-grained, high density graphite. The best results were obtained from graphite dies. A number of different approaches was tried in modifying the thermal gradient in the dies and in holding the dies. The best results here were obtained from a 0.25-in. thick Mo disc holding a graphite die directly and fitting the die quite closely. Ribbon growths as wide as 9 mm were obtained, while the longest ribbon was 450 x 3.5 x 0.5 mm. Resistivities of ribbons grown from graphite dies have been measured over the range of 0.03 to 1.6 ohm-cm. Some thoughts and literature findings are presented regarding refractory oxide materials as potential orifices
Incompressible fluid inside an astrophysical black hole?
It is argued that under natural hypothesis the Fermions inside a black hole
formed after the collapse of a neutron star could form a non compressible fluid
(well before reaching the Planck scale) leading to some features of integer
Quantum Hall Effect. The relations with black hole entropy are analyzed.
Insights coming from Quantum Hall Effect are used to analyze the coupling with
Einstein equations. Connections with some cosmological scenarios and with
higher dimensional Quantum Hall Effect are shortly pointed out.Comment: 30 pages, 2 figures. Accepted for publication on Physical Review D:
references added, typos corrected, test polishe
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