Dark energy density predicted and explained

It has recently been shown that the observed Hubble function for cosmological expansion can be fitted accurately back to redshift unity (7.33 Gyr ago) with only one free constant, while neglecting cosmic curvature and mass, using the modified Friedmann equation implied by subjecting the Higgs scalar field model to conformal Weyl scaling symmetry. Time-dependent solutions of the relativistic conformal Higgs scalar field equation coupled with the conformal Friedmann equation are shown here to imply dark energy of the observed magnitude. Predicted persistent cosmic acceleration is consistent with the nonclassical parameter inferred by conformal theory from observed excessive galactic rotation velocities and galactic dark halos, all without dark matter.Comment: 6 pages MS revised abstract, text, and references. Accepted for Europhysics Letter

Conformal theory of gravitation and cosmology

The postulate of universal local Weyl scaling (conformal) symmetry modifies both general relativity and the Higgs scalar field model. Conformal gravity (CG) has recently been fitted to rotation data for 138 galaxies. The conformal Higgs model (CHM) acquires a gravitational effect that fits observed Hubble expansion for redshifts $z\leq 1$ (7.33 Gyr) accurately with only one free constant parameter. The astrophysical data fitted by these two conformal models is shown here to account for both arbitrary parameters $w^2$ and $\lambda$ of postulated Higgs potential $V=-(w^2-\lambda\Phi^\dagger\Phi)\Phi^\dagger\Phi$, responsible for symmetry-breaking finite $\Phi^\dagger\Phi$ in electroweak particle theory. The present analysis resolves recent criticism of CG. CG and CHM are shown here to be interdependent but compatible. Nonclassical CG acceleration $\gamma$ is shown to be determined by the CHM. Conformal theory explains dark energy and does not require dark matter, a viable alternative to the $\Lambda$CDM standard model. A recently established empirical relationship between classical and nonclassical galactic radial acceleration requires parameter $\gamma$ to be independent of galactic mass. Conformal theory is shown here to be consistent with this and with the $v^4$ baryonic Tully-Fisher relation for galactic rotation velocities. Vanishing of centripetal acceleration outside a halo boundary is a unique implication of the theory.Comment: 7 pages accepted for publication by EuroPhysLet

Dark galactic halos without dark matter

Using standard Einstein theory, baryonic mass cannot account for observed galactic rotation velocities and gravitational lensing, attributed to galactic dark matter halos. In contrast, theory constrained by Weyl conformal scaling symmetry explains observed galactic rotation in the halo region without invoking dark matter. An explanation of dark halos, gravitational lensing, and structural stabilization, without dark matter and consistent with conformal theory, is proposed here. Condensation of uniform primordial matter into a material cloud or galaxy vacates a large surrounding spherical halo. Within such an extended vacancy in the original cosmic background mass-energy density, conformal theory predicts centripetal acceleration of the observed magnitude.Comment: 5 pages, updated text, recent references added, accepted for Europhysics Letter

Conformal Gravity: Dark Matter and Dark Energy

This short review examines recent progress in understanding dark matter, dark energy, and galactic halos using theory that departs minimally from standard particle physics and cosmology. Strict conformal symmetry (local Weyl scaling covariance), postulated for all elementary massless fields, retains standard fermion and gauge boson theory but modifies Einstein-Hilbert general relativity and the Higgs scalar field model, with no new physical fields. Subgalactic phenomenology is retained. Without invoking dark matter, conformal gravity and a conformal Higgs model fit empirical data on galactic rotational velocities, galactic halos, and Hubble expansion including dark energy.Comment: 9 pp in revtex format. References added with minor text revision