6,903 research outputs found
Energy and angular momentum of general 4-dimensional stationary axi-symmetric spacetime in teleparallel geometry
We derive an exact general axi-symmetric solution of the coupled
gravitational and electromagnetic fields in the tetrad theory of gravitation.
The solution is characterized by four parameters (mass), (charge),
(rotation) and (NUT). We then, calculate the total exterior energy using
the energy-momentum complex given by M{\o}ller in the framework of
Weitzenbck geometry. We show that the energy contained in a sphere is
shared by its interior as well as exterior. We also calculate the components of
the spatial momentum to evaluate the angular momentum distribution. We show
that the only non-vanishing components of the angular momentum is in the Z
direction.Comment: Latex. Will appear in IJMP
Relativity accommodates superluminal mean velocities
Contrary to a widespread belief, measures of velocity can yield a value
larger than , the instantaneous light speed in vacuum, without contradicting
Einstein's relativity. Nevertheless, the effect turns out to be too small to
explain the recently claimed superluminal velocity by the OPERA collaboration.
Several other general relativistic effects acting on the OPERA neutrinos are
also analyzed. All of them are unable to explain the OPERA result.Comment: 5 pages; Latex source, 2 eps figures (expanded discussion, a few
typos corrected, some refs. added
Isometric Immersions and the Waving of Flags
In this article we propose a novel geometric model to study the motion of a
physical flag. In our approach a flag is viewed as an isometric immersion from
the square with values into satisfying certain boundary
conditions at the flag pole. Under additional regularity constraints we show
that the space of all such flags carries the structure of an infinite
dimensional manifold and can be viewed as a submanifold of the space of all
immersions. The submanifold result is then used to derive the equations of
motion, after equipping the space of isometric immersions with its natural
kinetic energy. This approach can be viewed in a similar spirit as Arnold's
geometric picture for the motion of an incompressible fluid.Comment: 25 pages, 1 figur
Kerr-Newman Solution and Energy in Teleparallel Equivalent of Einstein Theory
An exact charged axially symmetric solution of the coupled gravitational and
electromagnetic fields in the teleparallel equivalent of Einstein theory is
derived. It is characterized by three parameters ``the gravitational mass
, the charge parameter and the rotation parameter " and its
associated metric gives Kerr-Newman spacetime. The parallel vector field and
the electromagnetic vector potential are axially symmetric. We then, calculate
the total energy using the gravitational energy-momentum. The energy is found
to be shared by its interior as well as exterior. Switching off the charge
parameter we find that no energy is shared by the exterior of the Kerr-Newman
black hole.Comment: 11 pages, Latex. Will appear in Mod. Phys. Lett.
On the Definition of the Centre of Gravity of an Arbitrary Closed System in the Theory of Relativity
Including changes in security of supply in cost benefit analysis â an application to oil prices in the transport sector
This paper contains a tentative suggestion of how to take into account changes in security of supply in real world cost-benefit analysis. Assuming that consumers are risk avers, security of supply can be viewed as a matter of avoiding oscillations in consumption originating from volatile prices of for in- stance oil. When the government makes transport related choices on behalf of the consumers, the effect on oscillations in general consumption should be included in the policy assessment taking into account the most significant correlations between prices on alternative fuels and between fuel prices and consumption in general. In the paper, a method of valuing changes in security of supply based on portfolio theory is applied to some very simple transport related examples. They indicate that includ- ing the value of changes in security of supply often makes very little difference to the results of cost benefit analysis, but more work has to be done on quantifying, among other things, consumersâ risk aversion and the background standard deviation in total consumption before firm conclusions can be drawn
Calcareous nannofossil and foraminifer biostratigraphy of the CampanianâMaastrichtian chalk of the Femern BĂŚlt (DenmarkâGermany).
A new study based on calcareous nannofossil and benthic
and planktonic foraminifer biostratigraphy is presented for
the upper Campanian â Maastrichtian chalk of the Femern
BĂŚlt (Denmark and Germany; Fig.1). The results are consistent
with recent studies of the Danish chalk for this interval,
allowing correlation across the Danish Basin and forming the
basis for correlation further afield within the Boreal Realm.
Numerous studies have been carried out recently on the upper
Campanian â Maastrichtian chalk of the Danish Basin,
covering aspects such as sedimentology, depositional environment,
macrofossil biostratigraphy, carbon isotope stratigraphy
as well as nannofossil and dinoflagellate biostratigraphy.
However, very few published studies on foraminifers
exist across this interval in this area. The 09.A.006, 09.A.007
and 09.A.008 boreholes (Fig. 2) were drilled in 2009 in preparation
for construction of a fixed link across the Femern
BÌlt, which will connect Denmark to Germany (Rambøll
Arup JV 2011). The boreholes penetrated glacial till, Paleoceneâ
Eocene clay and chalk (Sheldon et al. 2012). Here, for
the first time, the Boreal foraminifer biostratigraphy of the
late Campanian â Maastrichtian interval is investigated and
presented alongside nannofossil biostratigraphy
On the Clock Paradox in the case of circular motion of the moving clock
In this paper we deal analytically with a version of the so called clock
paradox in which the moving clock performs a circular motion of constant
radius. The rest clock is denoted as (1), the rotating clock is (2), the
inertial frame in which (1) is at rest and (2) moves is I and, finally, the
accelerated frame in which (2) is at rest and (1) rotates is A. By using the
General Theory of Relativity in order to describe the motion of (1) as seen in
A we will show the following features. I) A differential aging between (1) and
(2) occurs at their reunion and it has an absolute character, i.e. the proper
time interval measured by a given clock is the same both in I and in A. II)
From a quantitative point of view, the magnitude of the differential aging
between (1) and (2) does depend on the kind of rotational motion performed by
A. Indeed, if it is uniform there is no any tangential force in the direction
of motion of (2) but only normal to it. In this case, the proper time interval
reckoned by (2) does depend only on its constant velocity v=romega. On the
contrary, if the rotational motion is uniformly accelerated, i.e. a constant
force acts tangentially along the direction of motion, the proper time
intervals on the angular acceleration alpha. III) Finally, in
regard to the sign of the aging, the moving clock (2) measures always a
interval of proper time with respect to (1).Comment: LaTex2e, 9 pages, no figures, no tables. It is the follow-on of the
paper physics/040503
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