3,472 research outputs found

### Interpretations of the Accelerating Universe

It is generally argued that the present cosmological observations support the
accelerating models of the universe, as driven by the cosmological constant or
`dark energy'. We argue here that an alternative model of the universe is
possible which explains the current observations of the universe. We
demonstrate this with a reinterpretation of the magnitude-redshift relation for
Type Ia supernovae, since this was the test that gave a spurt to the current
trend in favour of the cosmological constant.Comment: 12 pages including 2 figures, minor revision, references added, a
paragraph on the interpretation of the CMB anisotropy in the QSSC added in
conclusion, general results unchanged. To appear in the October 2002 issue of
the "Publications of the Astronmical Society of the Pacific

### A Classical Treatment of Island Cosmology

Computing the perturbation spectrum in the recently proposed Island Cosmology
remains an open problem. In this paper we present a classical computation of
the perturbations generated in this scenario by assuming that the NEC-violating
field behaves as a classical phantom field. Using an exactly-solvable
potential, we show that the model generates a scale-invariant spectrum of
scalar perturbations, as well as a scale-invariant spectrum of gravitational
waves. The scalar perturbations can have sufficient amplitude to seed
cosmological structure, while the gravitational waves have a vastly diminished
amplitude.Comment: 8 pages, 1 figur

### Is the present expansion of the universe really accelerating?

The current observations are usually explained by an accelerating expansion
of the present universe. However, with the present quality of the supernovae Ia
data, the allowed parameter space is wide enough to accommodate the
decelerating models as well. This is shown by considering a particular example
of the dark energy equation-of-state $w_\phi\equiv p_\phi/\rho_\phi=-1/3$,
which is equivalent to modifying the \emph{geometrical curvature} index $k$ of
the standard cosmology by shifting it to $(k-\alpha)$ where $\alpha$ is a
constant. The resulting decelerating model is consistent with the recent CMB
observations made by WMAP, as well as, with the high redshift supernovae Ia
data including SN 1997ff at $z= 1.755$. It is also consistent with the newly
discovered supernovae SN 2002dc at $z=0.475$ and SN 2002dd at $z=0.95$ which
have a general tendency to improve the fit.Comment: Replaced with the accepted version to appear in MNRA

### On the nature of the quasi-stellar objects

Quasi-stellar objects at cosmological distances or local objects - optical properties of quasi- stellar objects and radio emission from star

### A Radical Departure from the ''steady State'' Concept in Cosmology

Radical departure from steady state theory in cosmolog

### Distances to Cepheid Open Clusters Via Optical and K-Band Imaging

We investigate the reddening and Main Sequence fitted distances to eleven
young, Galactic open clusters that contain Cepheids. Each cluster contains or
is associated with at least one Cepheid variable star. Reddening to the
clusters is estimated using the U-B:B-V colours of the OB stars and the
distance modulus to the cluster is estimated via B-V:V and V-K:V
colour-magnitude diagrams. By main-sequence fitting we proceed to calibrate the
Cepheid P-L relation and find M_V=-2.81xlogP-1.33 +/-0.32 and
M_K=-3.44xlogP-2.20 +/-0.29 and a distance modulus to the LMC of 18.55+/-0.32
in the V-band and 18.47+/-0.29 in the K-band giving an overall distance modulus
to the LMC of 18.51+/-0.3.
In the case of two important clusters we find that the U-B:B-V diagram in
these clusters is not well fitted by the standard Main Sequence line. In one
case, NGC7790, we find that the F stars show a UV excess which if caused by
metallicity would imply Fe/H ~ -1.5; this is anomalously low compared to what
is expected for young open clusters. In a second case, NGC6664, the U-B:B-V
diagram shows too red U-B colours for the F stars which in this case would
imply a higher than solar metallicity. If these effects are due to metallicity
then it would imply that the Cepheid PL(V) and PL(K) zeropoints depend on
metallicity according to delta(M)/delta(Fe/H) ~0.66 in the sense that lower
metallicity Cepheids are intrinsically fainter. Medium-high resolution
spectroscopy for the main-sequence F stars in these two clusters is needed to
determine if metallicity really is the cause or whether some other explanation
applies.Comment: Submitted to MNRAS. Due to large size of paper, please see
http://star-www.dur.ac.uk:80/~fhoyle/papers.html for a version with the
figures correctly inserte

### Inhomogeneities in the Microwave Background Radiation interpreted within the framework of the Quasi-Steady State Cosmology

We calculate the expected angular power spectrum of the temperature
fluctuations in the microwave background radiation (MBR) generated in the
quasi-steady state cosmology (QSSC). The paper begins with a brief description
of how the background is produced and thermalized in the QSSC. We then discuss
within the framework of a simple model, the likely sources of fluctuations in
the background due to astrophysical and cosmological causes. Power spectrum
peaks at $l \approx 6-10$, 180-220 and 600-900 are shown to be related in this
cosmology respectively to curvature effects at the last minimum of the scale
factor, clusters and groups of galaxies. The effect of clusters is shown to be
related to their distribution in space as indicated by a toy model of structure
formation in the QSSC. We derive and parameterize the angular power spectrum
using six parameters related to the sources of temperature fluctuations at
three characteristic scales. We are able to obtain a satisfactory fit to the
observational band power estimates of MBR temperature fluctuation spectrum.
Moreover, the values of `best fit' parameters are consistent with the range of
expected values.Comment: 27 pages, including 5 figures; to appear in Astrophys.

### The cosmological BCS mechanism and the Big Bang Singularity

We provide a novel mechanism that resolves the Big Bang Singularity present
in FRW space-times without the need for ghost fields. Building on the fact that
a four-fermion interaction arises in General Relativity when fermions are
covariantly coupled, we show that at early times the decrease in scale factor
enhances the correlation between pairs of fermions. This enhancement leads to a
BCS-like condensation of the fermions and opens a gap dynamically driving the
Hubble parameter $H$ to zero and results in a non-singular bounce, at least in
some special cases.Comment: replaced to match the journal versio

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