121 research outputs found
The distance modulus determined from Carmeli's cosmology fits the accelerating universe data of the high-redshift type Ia supernovae without dark matter
The velocity of the Hubble expansion has been added to General Relativity by
Moshe Carmeli and this resulted in new equations of motion for the expanding
universe. For the first time the observational magnitude-redshift data derived
from the high- supernova teams has been analysed in the framework of the
Carmeli theory and the fit to that theory is achieved without the inclusion of
any dark matter. Best fits to the data yield an averaged matter density for the
universe at the present epoch , which falls well
within the measured values of the baryonic matter density. And the best
estimate of at the present epoch.
The analysis also clearly distinguishes that the Hubble expansion of the
universe is speed-limited.Comment: 10 pages, includes 7 figures, revised version, paper accepted in
Found. Phys. Letters 200
Ultra-low vibration pulse-tube cryocooler stabilized cryogenic sapphire oscillator with 10^-16 fractional frequency stability
A low maintenance long-term operational cryogenic sapphire oscillator has
been implemented at 11.2 GHz using an ultra-low-vibration cryostat and
pulse-tube cryocooler. It is currently the world's most stable microwave
oscillator employing a cryocooler. Its performance is explained in terms of
temperature and frequency stability. The phase noise and the Allan deviation of
frequency fluctuations have been evaluated by comparing it to an ultra-stable
liquid-helium cooled cryogenic sapphire oscillator in the same laboratory.
Assuming both contribute equally, the Allan deviation evaluated for the
cryocooled oscillator is sigma_y = 1 x 10^-15 tau^-1/2 for integration times 1
< tau < 10 s with a minimum sigma_y = 3.9 x 10^-16 at tau = 20 s. The long term
frequency drift is less than 5 x 10^-14/day. From the measured power spectral
density of phase fluctuations the single side band phase noise can be
represented by L_phi(f) = 10^-14.0/f^4+10^-11.6/f^3+10^-10.0/f^2+10^-10.2/f+
10^-11.0 for Fourier frequencies 10^-3<f<10^3 Hz in the single oscillator. As a
result L_phi approx -97.5 dBc/Hz at 1 Hz offset from the carrier.Comment: 8 pages, 10 figures, presented at European Frequency and Time Forum,
ESTEC, Noordwijk, Netherland, April 11-16th 2010 accepted in IEEE Trans. on
Micro. Theory & Technique
Microwave cavity light shining through a wall optimization and experiment
It has been proposed that microwave cavities can be used in a photon
regeneration experiment to search for hidden sector photons. Using two isolated
cavities, the presence of hidden sector photons could be inferred from a 'light
shining through a wall' phenomenon. The sensitivity of the experiment has
strong a dependence on the geometric construction and electromagnetic mode
properties of the two cavities. In this paper we perform an in depth
investigation to determine the optimal setup for such an experiment. We also
describe the results of our first microwave cavity experiment to search for
hidden sector photons. The experiment consisted of two cylindrical copper
cavities stacked axially inside a single vacuum chamber. At a hidden sector
photon mass of 37.78 micro eV we place an upper limit on the kinetic mixing
parameter chi = 2.9 * 10^(-5). Whilst this result lies within already
established limits our experiment validates the microwave cavity `light shining
through a wall' concept. We also show that the experiment has great scope for
improvement, potentially able to reduce the current upper limit on the mixing
parameter chi by several orders of magnitude.Comment: To be published in PR
The Cosmic Time in Terms of the Redshift
In cosmology one labels the time t since the Big Bang in terms of the
redshift of light emitted at t, as we see it now. In this Note we derive a
formula that relates t to z which is valid for all redshifts. One can go back
in time as far as one wishes, but not to the Big Bang at which the redshift
tends to infinity.Comment: 3 pages, 3 figure
On the anomalous acceleration of Pioneer spacecraft
The anomalous acceleration of Pioneer 10 and 11 spacecraft of (8.74 \pm 1.33)
\times 10^{-8} cm. s^{-2} fits with a theoretical prediction of a minimal
acceleration in nature of about 7.61 \times 10^{-8} cm. s^{-2}Comment: 3 pages, accepted in Int. J. Theor. Phy
Ultra-low-phase-noise cryocooled microwave dielectric-sapphire-resonator oscillators with 1 x 10^-16 frequency instability
Two nominally identical ultra-stable cryogenic microwave oscillators are
compared. Each incorporates a dielectric-sapphire resonator cooled to near 6 K
in an ultra-low vibration cryostat using a low-vibration pulse-tube cryocooler.
The phase noise for a single oscillator is measured at -105 dBc/Hz at 1 Hz
offset on the 11.2 GHz carrier. The oscillator fractional frequency stability
is characterized in terms of Allan deviation by 5.3 x 10^-16 tau^-1/2 + 9 x
10^-17 for integration times 0.1 s < tau < 1000 s and is limited by a flicker
frequency noise floor below 1 x 10^-16. This result is better than any other
microwave source even those generated from an optical comb phase-locked to a
room temperature ultra-stable optical cavity.Comment: 4 pages, 5 figure
Cryogenic Sapphire Oscillator using a low-vibration design pulse-tube cryocooler: First results
A Cryogenic Sapphire Oscillator has been implemented at 11.2 GHz using a
low-vibration design pulse-tube cryocooler. Compared with a state-of-the-art
liquid helium cooled CSO in the same laboratory, the square root Allan variance
of their combined fractional frequency instability is for integration times s, dominated by
white frequency noise. The minimum for the two
oscillators was reached at s. Assuming equal contributions from
both CSOs, the single oscillator phase noise at 1 Hz offset from the carrier.Comment: 5 pages, 5 figures, accepted in IEEE Trans on Ultrasonics,
Ferroelectrics and Frequency Contro
The vector algebra war: a historical perspective
There are a wide variety of different vector formalisms currently utilized in
engineering and physics. For example, Gibbs' three-vectors, Minkowski
four-vectors, complex spinors in quantum mechanics, quaternions used to
describe rigid body rotations and vectors defined in Clifford geometric
algebra. With such a range of vector formalisms in use, it thus appears that
there is as yet no general agreement on a vector formalism suitable for science
as a whole. This is surprising, in that, one of the primary goals of nineteenth
century science was to suitably describe vectors in three-dimensional space.
This situation has also had the unfortunate consequence of fragmenting
knowledge across many disciplines, and requiring a significant amount of time
and effort in learning the various formalisms. We thus historically review the
development of our various vector systems and conclude that Clifford's
multivectors best fulfills the goal of describing vectorial quantities in three
dimensions and providing a unified vector system for science.Comment: 8 pages, 1 figure, 1 tabl
Finite bounded expanding white hole universe without dark matter
The solution of Einstein's field equations in Cosmological General Relativity
(CGR), where the Galaxy is at the center of a finite yet bounded spherically
symmetrical isotropic gravitational field, is identical with the unbounded
solution. This leads to the conclusion that the Universe may be viewed as a
finite expanding white hole. The fact that CGR has been successful in
describing the distance modulus verses redshift data of the high-redshift type
Ia supernovae means that the data cannot distinguish between unbounded models
and those with finite bounded radii of at least . Also it is shown that
the Universe is spatially flat at the current epoch and has been at all past
epochs where it was matter dominated.Comment: 11 pages, revised versio
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