275 research outputs found
Does special relativity theory tell us anything new about space and time?
It will be shown that, in comparison with the pre-relativistic
Galileo-invariant conceptions, special relativity tells us nothing new about
the geometry of spacetime. It simply calls something else "spacetime", and this
something else has different properties. All statements of special relativity
about those features of reality that correspond to the original meaning of the
terms "space" and "time" are identical with the corresponding traditional
pre-relativistic statements. It will be also argued that special relativity and
Lorentz theory are completely identical in both senses, as theories about
spacetime and as theories about the behavior of moving physical objects.Comment: 26 pages, LaTeX, new passages adde
The Hypothesis of Locality and its Limitations
The hypothesis of locality, its origin and consequences are discussed. This
supposition is necessary for establishing the local spacetime frame of
accelerated observers; in this connection, the measurement of length in a
rotating system is considered in detail. Various limitations of the hypothesis
of locality are examined.Comment: LaTeX file, no figures, 14 pages, to appear in: "Relativity in
Rotating Frames", edited by G. Rizzi and M.L. Ruggiero (Kluwer Academic
Publishers, Dordrecht, 2003
The origin of defects induced in ultra-pure germanium by Electron Beam Deposition
The creation of point defects in the crystal lattices of various
semiconductors by subthreshold events has been reported on by a number of
groups. These observations have been made in great detail using sensitive
electrical techniques but there is still much that needs to be clarified.
Experiments using Ge and Si were performed that demonstrate that energetic
particles, the products of collisions in the electron beam, were responsible
for the majority of electron-beam deposition (EBD) induced defects in a
two-step energy transfer process. Lowering the number of collisions of these
energetic particles with the semiconductor during metal deposition was
accomplished using a combination of static shields and superior vacuum
resulting in devices with defect concentrations lower than cm, the measurement limit of our deep level transient
spectroscopy (DLTS) system. High energy electrons and photons that samples are
typically exposed to were not influenced by the shields as most of these
particles originate at the metal target thus eliminating these particles as
possible damage causing agents. It remains unclear how packets of energy that
can sometimes be as small of 2eV travel up to a m into the material while
still retaining enough energy, that is, in the order of 1eV, to cause changes
in the crystal. The manipulation of this defect causing phenomenon may hold the
key to developing defect free material for future applications.Comment: 18 pages, 9 figure
Using the Wigner-Ibach Surmise to Analyze Terrace-Width Distributions: History, User's Guide, and Advances
A history is given of the applications of the simple expression generalized
from the surmise by Wigner and also by Ibach to extract the strength of the
interaction between steps on a vicinal surface, via the terrace width
distribution (TWD). A concise guide for use with experiments and a summary of
some recent extensions are provided.Comment: 11 pages, 4 figures, reformatted (with revtex) version of refereed
paper for special issue of Applied Physics A entitled "From Surface Science
to Device Physics", in honor of the retirements of Prof. H. Ibach and Prof.
H. L\"ut
Das Problem in ein Postulat verwandeln: Cassirer und Einsteins Unterscheidung von konstruktiven und Prinzipien-Theorien
Neutron Stars in Teleparallel Gravity
In this paper we deal with neutron stars, which are described by a perfect
fluid model, in the context of the teleparallel equivalent of general
relativity. We use numerical simulations to find the relationship between the
angular momentum of the field and the angular momentum of the source. Such a
relation was established for each stable star reached by the numerical
simulation once the code is fed with an equation of state, the central energy
density and the ratio between polar and equatorial radii. We also find a regime
where linear relation between gravitational angular momentum and moment of
inertia (as well as angular velocity of the fluid) is valid. We give the
spatial distribution of the gravitational energy and show that it has a linear
dependence with the squared angular velocity of the source.Comment: 19 pages, 14 figures. arXiv admin note: text overlap with
arXiv:1206.331
Microfluidic systems for the analysis of the viscoelastic fluid flow phenomena in porous media
In this study, two microfluidic devices are proposed as simplified 1-D microfluidic analogues of a porous medium. The objectives are twofold: firstly to assess the usefulness of the microchannels to mimic the porous medium in a controlled and simplified manner, and secondly to obtain a better insight about the flow characteristics of viscoelastic fluids flowing through a packed bed. For these purposes, flow visualizations and pressure drop measurements are conducted with Newtonian and viscoelastic fluids. The 1-D microfluidic analogues of porous medium consisted of microchannels with a sequence of contractions/ expansions disposed in symmetric and asymmetric arrangements. The real porous medium is in reality, a complex combination of the two arrangements of particles simulated with the microchannels, which can be considered as limiting ideal configurations. The results show that both configurations are able to mimic well the pressure drop variation with flow rate for Newtonian fluids. However, due to the intrinsic differences in the deformation rate profiles associated with each microgeometry, the symmetric configuration is more suitable for studying the flow of viscoelastic fluids at low De values, while the asymmetric configuration provides better results at high De values. In this way, both microgeometries seem to be complementary and could be interesting tools to obtain a better insight about the flow of viscoelastic fluids through a porous medium. Such model systems could be very interesting to use in polymer-flood processes for enhanced oil recovery, for instance, as a tool for selecting the most suitable viscoelastic fluid to be used in a specific formation. The selection of the fluid properties of a detergent for cleaning oil contaminated soil, sand, and in general, any porous material, is another possible application
Mach's Principle and the Origin of Inertia
The current status of Mach's principle is discussed within the context of
general relativity. The inertial properties of a particle are determined by its
mass and spin, since these characterize the irreducible unitary representations
of the inhomogeneous Lorentz group. The origin of the inertia of mass and
intrinsic spin are discussed and the inertia of intrinsic spin is studied via
the coupling of intrinsic spin with rotation. The implications of spin-rotation
coupling and the possibility of history dependence and nonlocality in
relativistic physics are briefly mentioned.Comment: 14 pages. Dedicated to Carl Brans in honor of his 80th birthday. To
appear in the Brans Festschrift; v2: typo corrected, published in: At the
Frontier of Spacetime, edited by T. Asselmeyer-Maluga (Springer, 2016),
Chapter 10, pp. 177-18
Modelling the decadal dynamics of reach-scale river channel evolution and floodplain turnover in CAESAR-Lisflood
Gravitational Radiation from Post-Newtonian Sources and Inspiralling Compact Binaries
The article reviews the current status of a theoretical approach to the
problem of the emission of gravitational waves by isolated systems in the
context of general relativity. Part A of the article deals with general
post-Newtonian sources. The exterior field of the source is investigated by
means of a combination of analytic post-Minkowskian and multipolar
approximations. The physical observables in the far-zone of the source are
described by a specific set of radiative multipole moments. By matching the
exterior solution to the metric of the post-Newtonian source in the near-zone
we obtain the explicit expressions of the source multipole moments. The
relationships between the radiative and source moments involve many non-linear
multipole interactions, among them those associated with the tails (and
tails-of-tails) of gravitational waves. Part B of the article is devoted to the
application to compact binary systems. We present the equations of binary
motion, and the associated Lagrangian and Hamiltonian, at the third
post-Newtonian (3PN) order beyond the Newtonian acceleration. The
gravitational-wave energy flux, taking consistently into account the
relativistic corrections in the binary moments as well as the various tail
effects, is derived through 3.5PN order with respect to the quadrupole
formalism. The binary's orbital phase, whose prior knowledge is crucial for
searching and analyzing the signals from inspiralling compact binaries, is
deduced from an energy balance argument.Comment: 109 pages, 1 figure; this version is an update of the Living Review
article originally published in 2002; available on-line at
http://www.livingreviews.org
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