arXiv subjects
Publications and source records attributed to J. W. Moffat.
The weak lensing of cosmic web filaments is investigated in modified gravity (MOG) and it is demonstrated that the detected galaxies and baryonic gas of order $5-15 \%$ in filaments can with the enhanced value of the strength of gravity agree with the lensing data for filaments without dark matter.
The galaxy cluster system Abell 1689 has been well studied and yields good lensing and X-ray gas data. Modified gravity (MOG) is applied to the cluster Abell 1689 and the acceleration data is well fitted without assuming dark matter. Newtonian dynamics and Modified Newtonian dynamics (MOND) are shown not to fit the acceleration data, while a dark matter model based on the Navarro-Frenk-White (NFW) mass profile is shown to fit the acceleration data for the radial range $r > 200$ kpc.
A composite model of quarks and bosons is proposed in which a spin $1/2$ isospin doublet $ψ$ is the basic building block of quarks, $W^\pm$, $Z^0$ and Higgs boson $H^0$ in the standard model. The $ψ$ has two components $α$ and $β$ with charges $Q_α=\frac{2}{3}e$ and $Q_β=-\frac{1}{3}e$, respectively. The two constituent flavors $α$ and $β$ combine to form the three generations of colored standard model quark flavors. A triplet of massless hypergluons binds the constituents called geminis. The strong confining non-Abelian $SU(2)_C$ constituent color dynamics has a confining energy scale $Λ_{CD}$. The leptons, the massless photon, gluons and triplet of hypergluons are treated as point particles. The non-Abelian $SU(2)_C$ color dynamics satisfies asymptotic freedom, and, together with the compositeness of the Higgs boson $H^0$, resolve the Higgs mass and gauge hierarchy fine-tuning problems.
The nature of gravitational waves in a generalized gravitation theory is investigated. The linearized field equations and the metric tensor quadrupole moment power and the decrease in radius of an inspiralling binary system of two compact objects are derived. The generalized Kerr metric describing a spinning black hole is determined by its mass $M$ and the spin parameter $a=cS/GM^2$. The LIGO-Virgo collaboration data is fitted with smaller binary black hole masses in agreement with the current electromagnetic, observed X-ray binary upper bound for a black hole mass, $M\lesssim 10M_\odot$.
The equation of motion in the generally covariant modified gravity (MOG) theory leads for weak gravitational fields and the non-relativistic limit to a modification of the Newtonian gravitational acceleration law, expressed in terms of two parameters $α$ and $μ$. The parameter $α$ determines the strength of the gravitational field and $μ$ is the effective mass of the vector field $ϕ_μ$, coupled with gravitational strength to baryonic matter. The MOG acceleration law for weak field gravitation and non-relativistic particles has been demonstrated to fit a wide range of galaxies, galaxy clusters and the Bullet Cluster and Train Wreck Cluster mergers. We demonstrate that the MOG acceleration law for a point mass source is in agreement with the McGaugh et al., correlation between the radial acceleration traced by galaxy rotation curves and the distribution of baryonic matter for the SPARC sample of 153 rotationally supported spiral and irregular galaxies.
An alternative to the postulate of dark energy required to explain the accelerated expansion of the universe is to adopt an inhomogeneous cosmological model to explain the supernovae data without dark energy. We adopt a void cosmology model, based on the inhomogeneous Lemaître-Tolman-Bondi solution of Einstein's field equations. The model can resolve observational anomalies in the $ΛCDM$ model, such as the discrepancy between the locally measured value of the Hubble constant, $H_0=73.24\pm 1.74\,{\rm km}\,{\rm s}^{-1}\,{\rm Mpc}^{-1}$, and the $H_0=66.93\pm 0.62\,{\rm km}\,{\rm s}^{-1}\,{\rm Mpc}^{-1}$ determined by the Planck satellite data and the $ΛCDM$ model, and the lithium $^{7}{\rm Li}$ problem, which is a $5σ$ mismatch between the theoretical prediction for the $^{7}{\rm Li}$ from big bang nucleosynthesis and the value that we observe locally today at $z=0$. The void model can also resolve the tension between the number of massive clusters derived from the Sunyaev-Zel'dovich effect by the Planck satellite and the number expected from the CMB anisotropies, and the CMB weak lensing anomaly observed in the Planck data. The cosmological Copernican principle and the time and position today coincidence conundrums in the $ΛCDM$ and void cosmological models are discussed.
A variable speed of light (VSL) cosmology is described in which the causal mechanism of generating primordial perturbations is achieved by varying the speed of light in a primordial epoch. This yields an alternative to inflation for explaining the formation of the cosmic microwave background (CMB) and the large scale structure (LSS) of the universe. The initial value horizon and flatness problems in cosmology are solved. The model predicts primordial scalar and tensor fluctuation spectral indices $n_s=0.96$ and $n_t=- 0.04$, respectively. We make use of the $δ{\cal N}$ formalism to identify signatures of primordial nonlinear fluctuations, and this allows the VSL model to be distinguished from inflationary models. In particular, we find that the parameter $f_{\rm NL}=5$ in the variable speed of light cosmology. The value of the parameter $g_{\rm NL}$ evolves during the primordial era and shows a running behavior.
Deviations from the standard $Λ$CDM model motivate an interpretation of early universe cosmology using the Scalar-Tensor-Vector-Gravity (STVG) theory. A constraint analysis carried out by Valentino, Melchiorri and Silk, revealed deviations from the growth of structure predicted by General Relativity, and a lensing anomaly in the angular CMB power spectrum data. The modified gravity (MOG) theory resolves the lensing deviation from the standard model and provides an explanation of the CMB and structure growth data.
A variable speed of light (VSL) cosmology is described in which the causal mechanism of generating primordial perturbations is achieved by varying the speed of light in a primordial epoch. This yields an alternative to inflation for explaining the formation of the cosmic microwave background (CMB) and the large scale structure (LSS) of the universe. We make use of the $δ{\cal N}$ formalism to identify signatures of primordial nonlinear fluctuations, and this allows the VSL model to be distinguished from inflationary models. In particular, we find that the parameter $f_{\rm NL}=5$ in the variable speed of light cosmology. The value of the parameter $g_{\rm NL}$ evolves during the primordial era and shows a running behavior.
A modified gravitational theory is developed in which the gravitational coupling constants $G$ and $Q$ and the effective mass $m_ϕ$ of a repulsive vector field run with momentum scale $k$ or length scale $\ell =1/k$, according to a renormalization group flow. The theory can explain cosmological early universe data with a dark hidden photon and late time galaxy and cluster dynamics without dark matter. The theory agrees with solar system and binary pulsar observations.
The field equations for Scalar-Tensor-Vector-Gravity (STVG) or modified gravity (MOG) have a static, spherically symmetric black hole solution determined by the mass $M$ with two horizons. The strength of the gravitational constant is $G=G_N(1+α)$ where $α$ is a parameter. A regular singularity-free MOG solution is derived using a nonlinear field dynamics for the repulsive gravitational field component and a reasonable physical energy-momentum tensor. The Kruskal-Szekeres completion of the MOG black hole solution is obtained. The Kerr-MOG black hole solution is determined by the mass $M$, the parameter $α$ and the spin angular momentum $J=Ma$. The equations of motion and the stability condition of a test particle orbiting the MOG black hole are derived, and the radius of the black hole photosphere and the shadows cast by the Schwarzschild-MOG and Kerr-MOG black holes are calculated. A traversable wormhole solution is constructed with a throat stabilized by the repulsive component of the gravitational field.
We present a direct and fairly simple proof of the following incidence bound: Let $P$ be a set of $m$ points and $L$ a set of $n$ lines in ${\mathbb R}^d$, for $d\ge 3$, which lie in a common algebraic two-dimensional surface of degree $D$ that does not contain any 2-flat, so that no 2-flat contains more than $s \le D$ lines of $L$. Then the number of incidences between $P$ and $L$ is $$ I(P,L)=O\left(m^{1/2}n^{1/2}D^{1/2} + m^{2/3}\min\{n,D^{2}\}^{1/3}s^{1/3} + m + n\right). $$ When $d=3$, this improves the bound of Guth and Katz~\cite{GK2} for this special case, when $D$ is not too large. A supplementary feature of this work is a review, with detailed proofs, of several basic (and folklore) properties of ruled surfaces in three dimensions.
Galaxy rotation curves determined observationally out to a radius well beyond the galaxy cores can provide a critical test of modified gravity models without dark matter. The predicted rotational velocity curve obtained from Scalar-Vector-Tensor Gravity (STVG or MOG) is in excellent agreement with data for the Milky Way without a dark matter halo, with a mass of $5\times 10^{10}\,M_{\odot}$. The velocity rotation curve predicted by modified Newtonian Dynamics (MOND) does not agree with the data.
A conformal coupling of the metric in the Jordan frame to the energy-momentum tensor, screens the scalar field gravitational coupling strength $G$ in modified gravity (MOG). The scalar field acquires a mass which depends on the local matter density: the scalar field particle is massive for the Sun and earth, where the density is high compared to low density environments in cosmology and astrophysics. Together with the screening of the vector field $ϕ_μ$, this guarantees that solar system tests of gravity are satisfied. The conformal metric is coupled to the electromagnetic matter field and energy-momentum tensor, screening $G$ for the Sun and the deflection of light by the Sun and the Shapiro time delay in MOG are in agreement with general relativity. For galaxies and galactic clusters the enhanced gravitational coupling constant $G$ leads to agreement with gravitational lensing without dark matter. For compact binary pulsars the screening of $G$ removes the monopole and dipole gravitational radiation modes in agreement with the binary pulsar timing data.
An important piece of evidence for dark matter is the need to explain the growth of structure from the time of horizon entry and radiation-matter equality to the formation of stars and galaxies. This cannot be explained by using general relativity without dark matter. So far, dark matter particles have not been detected in laboratory measurements or at the LHC. We demonstrate that enhanced structure growth can happen in a modified gravity theory (MOG). The vector field and particle introduced in the theory to explain galaxy and cluster dynamics plays an important role in generating the required structure growth. The particle called the phion (a light hidden photon) is neutral and is a dominant, pressureless component in the MOG Friedmann equations, before the time of decoupling. The dominant energy density of the phion particle in the early universe, generates an explanation for the growth of density perturbations. The angular acoustical power spectrum due to baryon-photon pressure waves is in agreement with the Planck 2013 data. As the universe expands and large scale structures are formed, the density of baryons dominates and the rotation curves of galaxies and the dynamics of clusters are explained in MOG, when the phion particle in the present universe is ultra-light. The matter power spectrum determined by the theory is in agreement with current galaxy redshift surveys.
A finite and unitary nonlocal formulation of quantum gravity is applied to the cosmological constant problem. The entire functions in momentum space at the graviton-standard model particle loop vertices generate an exponential suppression of the vacuum density and the cosmological constant to produce agreement with their observational bounds.
The spontaneous violation of Lorentz and diffeomorphism invariance in a phase near the big bang lowers the entropy, allowing for an arrow of time and the second law of thermodynamics. The spontaneous symmetry breaking leads to $O(3,1)\rightarrow O(3)\times R$, where $O(3)$ is the rotational symmetry of the Friedmann-Lemaître-Robertson-Walker spacetime. The Weyl curvature tensor $C_{μνρσ}$ vanishes in the FLRW spacetime satisfying the Penrose zero Weyl curvature conjecture. The requirement of a measure of gravitational entropy is discussed. The vacuum expectation value $\langle 0\vertψ_μ\vert 0\rangle\neq 0$ for a vector field $ψ_μ$ acts as an order parameter and at the critical temperature $T_c$ a phase transition occurs breaking the Lorentz symmetry spontaneously. During the ordered $O(3)$ symmetry phase the entropy is vanishingly small and for $T < T_c$ as the universe expands the anti-restored $O(3,1)$ Lorentz symmetry leads to a disordered phase and a large increase in entropy creating the arrow of time.
The quantum gravity effects of vacuum polarization of gravitons propagating in a curved spacetime cause the quantum vacuum to act as a dispersive medium with a refractive index. Due to this dispersive medium gravitons acquire superluminal velocities. The dispersive medium is produced by higher derivative curvature contributions to the effective gravitational action. It is shown that in a Friedmann-Lemaître-Robertson-Walker spacetime in the early universe near the Planck time $t_{\rm PL}\gtrsim 10^{-43}\,{\rm sec}$, the speed of gravitational waves $c_g\gg c_{g0}=c_0$, where $c_{g0}$ and $c_0$ are the speeds of gravitational waves and light today. The large speed of gravitational waves stretches their wavelengths to super-horizon sizes, allowing them to be observed in B-polarization experiments.