An Interpretation of Flat Density Cores of Clusters of Galaxies by Degeneracy Pressure of Fermionic Dark Matter: A Case Study of Abell 1689

Flat density cores have been obtained for a limited number of clusters of galaxies by strong gravitational lensing. This paper explores the possibility that the degeneracy pressure of fermionic dark matter accounts for the flat top density profiles. This is a case study of A1689 for which the density profile has been obtained from the inner region out to 1Mpc by the combination of strong and weak lensing. In the case that the dark matter consists of the mixture of degenerate relic neutrinos and collisionless cold dark matter particles, the acceptable mass range for relic neutrinos is between 1 and 2 eV, if the ratio of the two kinds of dark matter particles is fixed to its cosmic value.Comment: Accepted for Publication in ApJ. Companion paper to astro-ph/060709

Numerical investigation of friction in inflaton equations of motion

The equation of motion for the expectation value of a scalar quantum field does not have the local form that is commonly assumed in studies of inflationary cosmology. We have recently argued that the true, temporally non-local equation of motion does not possess a time-derivative expansion and that the conversion of inflaton energy into particles is not, in principle, described by the friction term estimated from linear response theory. Here, we use numerical methods to investigate whether this obstacle to deriving a local equation of motion is purely formal, or of some quantitative importance. Using a simple scalar-field model, we find that, although the non-equilibrium evolution can exhibit significant damping, this damping is not well described by the local equation of motion obtained from linear response theory. It is possible that linear response theory does not apply to the situation we study only because thermalization turns out to be slow, but we argue that that the large discrepancies we observe indicate a failure of the local approximation at a more fundamental level.Comment: 13 pages, 7 figure

Friction in inflaton equations of motion

The possibility of a friction term in the equation of motion for a scalar field is investigated in non-equilibrium field theory. The results obtained differ greatly from existing estimates based on linear response theory, and suggest that dissipation is not well represented by a term of the form $\eta\dot{\phi}$.Comment: 4 pages, 2 figures, RevTex4. An obscurity in the original version has been clarifie

Cosmological Constraints on a Dynamical Electron Mass

Motivated by recent astrophysical observations of quasar absorption systems, we formulate a simple theory where the electron to proton mass ratio $\mu =m_{e}/m_{p}$ is allowed to vary in space-time. In such a minimal theory only the electron mass varies, with $\alpha$ and $m_{p}$ kept constant. We find that changes in $\mu$ will be driven by the electronic energy density after the electron mass threshold is crossed. Particle production in this scenario is negligible. The cosmological constraints imposed by recent astronomical observations are very weak, due to the low mass density in electrons. Unlike in similar theories for spacetime variation of the fine structure constant, the observational constraints on variations in $\mu$ imposed by the weak equivalence principle are much more stringent constraints than those from quasar spectra. Any time-variation in the electron-proton mass ratio must be less than one part in $10^{9}$since redshifts $z\approx 1.$This is more than one thousand times smaller than current spectroscopic sensitivities can achieve. Astronomically observable variations in the electron-proton must therefore arise directly from effects induced by varying fine structure 'constant' or by processes associated with internal proton structure. We also place a new upper bound of $2\times 10^{-8}$ on any large-scale spatial variation of $\mu$ that is compatible with the isotropy of the microwave background radiation.Comment: New bounds from weak equivalence principle experiments added, conclusions modifie

Dissipation in equations of motion of scalar fields

The methods of non-equilibrium quantum field theory are used to investigate the possibility of representing dissipation in the equation of motion for the expectation value of a scalar field by a friction term, such as is commonly included in phenomenological inflaton equations of motion. A sequence of approximations is exhibited which reduces the non-equilibrium theory to a set of local evolution equations. However, the adiabatic solution to these evolution equations which is needed to obtain a local equation of motion for the expectation value is not well defined; nor, therefore, is the friction coefficient. Thus, a non-equilibrium treatment is essential, even for a system that remains close to thermal equilibrium, and the formalism developed here provides one means of achieving this numerically.Comment: 17 pages, 5 figure

The asymptotic quasi-stationary states of the two-dimensional magnetically confined plasma and of the planetary atmosphere

We derive the differential equation governing the asymptotic quasi-stationary states of the two dimensional plasma immersed in a strong confining magnetic field and of the planetary atmosphere. These two systems are related by the property that there is an intrinsic constant length: the Larmor radius and respectively the Rossby radius and a condensate of the vorticity field in the unperturbed state related to the cyclotronic gyration and respectively to the Coriolis frequency. Although the closest physical model is the Charney-Hasegawa-Mima (CHM) equation, our model is more general and is related to the system consisting of a discrete set of point-like vortices interacting in plane by a short range potential. A field-theoretical formalism is developed for describing the continuous version of this system. The action functional can be written in the Bogomolnyi form (emphasizing the role of Self-Duality of the asymptotic states) but the minimum energy is no more topological and the asymptotic structures appear to be non-stationary, which is a major difference with respect to traditional topological vortex solutions. Versions of this field theory are discussed and we find arguments in favor of a particular form of the equation. We comment upon the significant difference between the CHM fluid/plasma and the Euler fluid and respectively the Abelian-Higgs vortex models.Comment: Latex 126 pages, 7 eps figures included. Discussion on various forms of the equatio