260 research outputs found

### 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-

### A Solution to the electroweak horizon problem in the R_h=ct universe

Particle physics suggests that the Universe may have undergone several phase
transitions, including the well-known inflationary event associated with the
separation of the strong and electroweak forces in grand unified theories. The
accelerated cosmic expansion during this transition, at cosmic time
t~10^{-36}-10^{-33} seconds, is often viewed as an explanation for the
uniformity of the CMB temperature, T, which would otherwise have required
inexplicable initial conditions. With the discovery of the Higgs particle, it
is now quite likely that the Universe underwent another (electroweak) phase
transition, at T=159.5 +/- 1.5 GeV---roughly ~10^{-11} seconds after the big
bang. During this event, the fermions gained mass and the electric force
separated from the weak force. There is currently no established explanation,
however, for the apparent uniformity of the vacuum expectation value of the
Higgs field which, like the uniformity in T, gives rise to its own horizon
problem in standard LCDM cosmology. We show in this paper that a solution to
the electroweak horizon problem may be found in the choice of cosmological
model, and demonstrate that this issue does not exist in the alternative
Friedmann-Robertson-Walker cosmology known as the R_h=ct universe.Comment: 6 pages, 2 figures. Accepted for publication in the European Physical
Journal

### 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

### Physical Basis for the Symmetries in the Friedmann-Robertson-Walker Metric

Modern cosmological theory is based on the Friedmann--Robertson--Walker (FRW)
metric. Often written in terms of co-moving coordinates, this well-known
solution to Einstein's equations owes its elegant and highly practical
formulation to the cosmological principle and Weyl's postulate, upon which it
is founded. However, there is physics behind such symmetries, and not all of it
has yet been recognized. In this paper, we derive the FRW metric coefficients
from the general form of the spherically symmetric line element and demonstrate
that, because the co-moving frame also happens to be in free fall, the
symmetries in FRW are valid only for a medium with zero active mass. In other
words, the spacetime of a perfect fluid in cosmology may be correctly written
as FRW only when its equation of state is rho+3p=0, in terms of the total
pressure p and total energy density rho. There is now compelling observational
support for this conclusion, including the Alcock--Paczynski test, which shows
that only an FRW cosmology with zero active mass is consistent with the latest
model-independent baryon acoustic oscillation data.Comment: 7 Pages. Final published versio

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