5,183 research outputs found
The R_h=ct Universe Without Inflation
The horizon problem in the standard model of cosmology (LDCM) arises from the
observed uniformity of the cosmic microwave background radiation, which has the
same temperature everywhere (except for tiny, stochastic fluctuations), even in
regions on opposite sides of the sky, which appear to lie outside of each
other's causal horizon. Since no physical process propagating at or below
lightspeed could have brought them into thermal equilibrium, it appears that
the universe in its infancy required highly improbable initial conditions. In
this paper, we examine this well-known problem by considering photon
propagation through a Friedmann-Robertson-Walker (FRW) spacetime at a more
fundamental level than has been attempted before, demonstrating that the
horizon problem only emerges for a subset of FRW cosmologies, such as LCDM,
that include an early phase of rapid deceleration. We show that the horizon
problem is nonexistent for the recently introduced R_h=ct universe, obviating
the principal motivation for the inclusion of inflation. We demonstrate through
direct calculation that, in the R_h=ct universe, even opposite sides of the
cosmos have remained causally connected to us - and to each other - from the
very first moments in the universe's expansion. Therefore, within the context
of the R_h=ct universe, the hypothesized inflationary epoch from t=10^{-35}
seconds to 10^{-32} seconds was not needed to fix this particular "problem",
though it may still provide benefits to cosmology for other reasons.Comment: 17 pages, 5 figures. arXiv Slight revisions in refereed version.
Accepted for publication in Astronomy & Astrophysic
Model Selection based on the Angular-Diameter Distance to the Compact Structure in Radio Quasars
Of all the distance and temporal measures in cosmology, the angular-diameter
distance, d_A(z), uniquely reaches a maximum value at some finite redshift
z_max and then decreases to zero towards the big bang. This effect has been
difficult to observe due to a lack of reliable, standard rulers, though
refinements to the identification of the compact structure in radio quasars may
have overcome this deficiency. In this Letter, we assemble a catalog of 140
such sources with 0 < z < 3 for model selection and the measurement of z_max.
In flat LCDM, we find that Omega_m= 0.24^{+0.1}_{-0.09}, fully consistent with
Planck, with z_max=1.69. Both of these values are associated with a d_A(z)
indistinguishable from that predicted by the zero active mass condition,
rho+3p=0, in terms of the total pressure p and total energy density rho of the
cosmic fluid. An expansion driven by this constraint, known as the R_h=ct
universe, has z_max=1.718, which differs from the measured value by less than
~1.6%. Indeed, the Bayes Information Criterion favours R_h=ct over flat LCDM
with a likelihood of ~81% versus 19%, suggesting that the optimized parameters
in Planck LCDM mimic the constraint p=-rho/3.Comment: 6 pages, 3 figures, 1 table. Accepted for publication in EP
A Cosmological basis for E=mc^2
The Universe has a gravitational horizon with a radius R_h=c/H coincident
with that of the Hubble sphere. This surface separates null geodesics
approaching us from those receding, and as free-falling observers within the
Friedmann-Lemaitre-Robertson-Walker spacetime, we see it retreating at proper
speed c, giving rise to the eponymously named cosmological model R_h=ct. As of
today, this cosmology has passed over 25 observational tests, often better than
LCDM. The gravitational/Hubble radius R_h therefore appears to be highly
relevant to cosmological theory, and in this paper we begin to explore its
impact on fundamental physics. We calculate the binding energy of a mass m
within the horizon and demonstrate that it is equal to mc^2. This energy is
stored when the particle is at rest near the observer, transitioning to a
purely kinetic form equal to the particle's escape energy when it approaches
R_h. In other words, a particle's gravitational coupling to that portion of the
Universe with which it is causally connected appears to be the origin of
rest-mass energy.Comment: 5 pages. Accepted for publication in IJMP-
Proper Size of the Visible Universe in FRW Metrics with Constant Spacetime Curvature
In this paper, we continue to examine the fundamental basis for the
Friedmann-Robertson-Walker (FRW) metric and its application to cosmology,
specifically addressing the question: What is the proper size of the visible
universe? There are several ways of answering the question of size, though
often with an incomplete understanding of how far light has actually traveled
in reaching us today from the most remote sources. The difficulty usually
arises from an inconsistent use of the coordinates, or an over-interpretation
of the physical meaning of quantities such as the so-called proper distance
R(t)=a(t)r, written in terms of the (unchanging) co-moving radius r and the
universal expansion factor a(t). In this paper, we use the five non-trivial FRW
metrics with constant spacetime curvature (i.e., the static FRW metrics, but
excluding Minkowski) to prove that in static FRW spacetimes in which expansion
began from an initial signularity, the visible universe today has a proper size
equal to R_h(t_0/2), i.e., the gravitational horizon at half its current age.
The exceptions are de Sitter and Lanczos, whose contents had pre-existing
positions away from the origin. In so doing, we confirm earlier results showing
the same phenomenon in a broad range of cosmologies, including LCDM, based on
the numerical integration of null geodesic equations through an FRW metric.Comment: Accepted for publication in Classical and Quantum Gravit
Angular Correlation of the CMB in the R_h=ct Universe
The emergence of several unexpected large-scale features in the cosmic
microwave background (CMB) has pointed to possible new physics driving the
origin of density fluctuations in the early Universe and their evolution into
the large-scale structure we see today. In this paper, we focus our attention
on the possible absence of angular correlation in the CMB anisotropies at
angles larger than ~60 degrees, and consider whether this feature may be the
signature of fluctuations expected in the R_h=ct Universe. We calculate the CMB
angular correlation function for a fluctuation spectrum expected from growth in
a Universe whose dynamics is constrained by the equation-of-state p=-rho/3,
where p and rho are the total pressure and density, respectively. We find that,
though the disparity between the predictions of LCDM and the WMAP sky may be
due to cosmic variance, it may also be due to an absence of inflation. The
classic horizon problem does not exist in the R_h=ct Universe, so a period of
exponential growth was not necessary in this cosmology in order to account for
the general uniformity of the CMB (save for the aforementioned tiny
fluctuations of 1 part in 100,000 in the WMAP relic signal. We show that the
R_h=ct Universe without inflation can account for the apparent absence in CMB
angular correlation at angles > 60 degrees without invoking cosmic variance,
providing additional motivation for pursuing this cosmology as a viable
description of nature.Comment: Accepted for publication in Astronomy & Astrophysic
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