I briefly highlight the salient properties of modified-inertiaformulations of MOND, contrasting them with those ofmodified-gravity formulations, which describe practically alltheories propounded to date. Future data (e.g. the establishmentof the Pioneer anomaly as a new physics phenomenon) may prefer oneof these broad classes of theories over the other. I also outlinesome possible starting ideas for modified inertia.


We first review the nonrelativistic Lagrangian theory as a framework for the MOND equation. Obstructions to a relativistic version of it are discussed leading up to TeVeS, a relativistic tensor-vector-scalar field theory which displays both MOND and Newtonian limits. The whys for its particular structure are discussed and its achievements so far are summarized.

I review various ideas on MOND cosmology and structureformationbeginning with non-relativistic models in analogy with Newtonian cosmology. I discuss relativistic MOND cosmology in the context ofBekenstein's theory and propose an alternative biscalar effective theoryof MOND in which the acceleration parameter, a0 is identifiedwith the cosmic time derivative of a matter coupling scalar fieldand cosmic CDM appears as scalar field oscillations of theauxiliary “coupling strength” field.

We present results derived from a high-resolution cosmological N-body simulation in which the equations of motion have been changed to account for MOdified Newtonian Dynamics (MOND). It is shown that a low-Ω0 MONDian model with an appropriate choice for the normalisation σ8 of the primordial density fluctuations can lead to similar clustering properties at redshift z = 0 as the commonly accepted (standard) ΛCDM model. However, such a model shows no significant structures at high redshift with only very few objects present beyond z > 3. For the current implementation of MOND density profiles of gravitationally bound objects at z = 0 can though still be fitted by the universal NFW profile.

The Pioneer 10/11 spacecraft yielded the most precise navigation in deepspace to date. However, their radio-metric tracking data has consistentlyindicated the presence of a small, anomalous, Doppler frequency drift. Thedrift is a blue-shift, uniformly changing with a rate of ~6 × 10-9 Hz/s and can be interpreted as a constant sunward acceleration ofeach particular spacecraft of aP = (8.74 ± 1.33) × 10-10 m/s2. The nature of this anomaly remains unexplained. Here wesummarize our current knowledge of the discovered effect and review some ofthe mechanisms proposed for its explanation. Currently we are preparing forthe analysis of the entire set of the available Pioneer 10/11 Doppler datawhich may shed a new light on the origin of the anomaly. We present apreliminary assessment of such an intriguing possibility.


The nonperturbative renormalization group flow of Quantum Einstein Gravity (QEG) is reviewed. It is argued that there could be strong renormalization effects at large distances, in particular a scale dependent Newton constant, which mimic the presence of dark matter at galactic and cosmological scales.

The standard model of cosmology considers the existence of two components of unknown nature, “dark matter” and “dark energy”, which determine the cosmological evolution. Their nature remains unknown, and other models can also be considered. In particular, it may be possible to reinterpret the recent cosmological observations so that the Universe does not contain two fluids of unknown natures, but only one fluid with particular properties. After a brief review of constraints on this unifying “dark fluid”, we will discuss a specific model of dark fluid based on a complex scalar fluid.

The bulge contribution to the inner density profile of a galaxy is well traced by the bulge's NIR surface brightness profile. We map the surface brightness profiles of bulges using HST/NICMOS imaging. Most bulges show nuclear components of 20–200 pc scales, and frequently also unresolved nuclear star clusters (<20 pc). These nuclear components are the densest parts of bulges, and gave bulges the “reputation” of having high stellar concentration. Actually, the Sérsic r1/n bulges typically have low concentrations, 1 < n < 2.5. We cannot confirm the bi-modal distribution of bulge profile slopes reported by others, and suggest that the alleged bi-modality is related to selectively excluding/including nuclear components in low/high-n bulges.

We propose to determine the stellar velocity dispersions of globular clustersin the outer halo of the Milky Way in order to decide whetherthe dynamics of the universe on large scales is governed by dark matteror modified Newtonian dynamics (MOND). We show that for a number ofGalactic globular clusters, both the internal and the external accelerationsare significantly below the critical acceleration parameter a0 of MOND.This leads to velocity dispersions in case of MOND which exceed their Newtonian counterpartsby up to a factor of 3, providing a stringent test for MOND.

Using a wavelet algorithm, we have mapped the temperature structure ofthe three relaxed clusters of galaxies Abell 478, Abell 1795 and Abell2029. The findings of significant non-radial thermal structuresoutside the core region of two of these clusters question the validitylimits of the elliptical symmetry hypothesis required for derivingcluster mass profiles from gas brightness and temperature profilesmeasurements.

We use the weak gravitational lensing effect to study the mass distribution of asample of 50 southern Abell clusters (0.05 < z < 0.3) having LX > 5 × 1044 erg s-1 observed with ESO-VLTunder uniform sky conditions and subarsecond (0.6'') image quality. Their dynamicalequibrium is assesed through comparison of the clusters mass estimates made by weak-lensing,velocity-dispersions and X-ray techniques. So far, for 24 clusters (Cyprianoet al. 2004),we find: a) the center of their mass and light distributions are coincident for77% of the sample; b) the elongations of the fitted mass profiles and of the lightof the cD galaxies generally match with each other; c) although mostof the clusters are found to be in dynamical equilibrium, those with TX ≥ 8 keV(or σv ≥ 1120 km s-1) are the discordant ones. The preliminary bright arc statistics for our whole sample (LZLS) suggests the presence of acut-off at z ~ 0.07 which is qualitatively consistent with predictions donein a ΛCDM cosmology (Meneghetti et al. 2003).

New 21-cm observations of Messier 31 are used to measure its rotation curve up to a radius of ~40 kpc. The observations were obtained at the Effelsberg 100-m telescope and extend by ~15 kpc the radius of the last measured point of the rotation curve. A preliminary model of the mass distributionshows that at the last observed velocity point, the dark–to–luminousmass ratio is ~1 for a total mass of ~4.5 × 1011 M๏, whichvalue is comparable with that of the Milky Way. This exploratory project is ongoing and other Hi observations using other radio-telescopes are planned to confirm this result, as well as a mosaic of the Hα emissionline.

We have analyzed the intra-group light component of 3 Hickson CompactGroups (HCG 79, HCG 88 and HCG 95) with detections in two of them:HCG 79, with 46±11% of the total B band luminosity and HCG 95with 11±26%. HCG 88 had no component detected. This componentis presumably due to tidally stripped stellar material trapped inthe group potential and represents an efficient tool to determine thestage of dynamical evolution and to map its gravitational potential.To detect this low surface brightness structure we have applied thewavelet technique OV_WAV, which separates the different components ofthe image according to their spatial characteristic sizes.

We have studied the structural and dynamical parameters of two samples of elliptical-like-objects (ELOs)formed in a set of self-consistent hydrodynamical simulations.ELO stellar masses,projected half- stellar mass radii, and stellar centrall.o.s. velocity dispersions have been found to define a dynamical Fundamental Plane (FP), whose physical origin we report on.

The inner Galaxy is completely dominated by baryons, contrary to thepredictions of CDM cosmology, whilst the observations arecompatible with MOND if the local circular speed is smaller than 220 km s-1and the asymptotic circular velocity close to 170 km s-1.

We present HI data of the dwarf galaxy DDO 47, aimed at testingthe hypothesis that dark halo triaxiality might induce non-circular motions resultingin rotation curves best fitted by cored halos, even if the dark matter halo is intrinsicallycuspy. We performed a harmonic decomposition of the velocity field in order to search for alleged non-circular motions needed to “hide” a cusp: in DDO 47non-circular motions are globally at a level of 2–3 km s-1, far from being sufficient to reconcile the observed rotation curvewith the ΛCDM predictions.We conclude that the dark matter halo around DDO 47 is truly cored and that a cusp cannot be hidden by non-circular motions.More details are shown in Gentile et al. (2005).

We present the preliminary results from a combined X-ray/ lensing investigation of the galaxy cluster RBS 864 (z = 0.29). Morphological and spectral studies of X-ray data show a relaxed appearance of this cluster, thus allowing us to derive a good mass estimate.From optical data we found the presence of a very high number of arc candidates and performed a strong lensing mass analysis. We found a large discrepancy in the comparison of the X-ray and lensing masses.

Most of the orbits of the Milky Way (MW) satellite galaxies and some of the orbitsof the MW globular cluster system lie near Great Circles in the Sky.The existence of satellites in the same orbital plane could be understood if theywere part of the same accretion event. However,this argument cannot explain, for example, the different star formationhistories of dwarfs belonging to the same Great Circle. In this paperwe will show, using hydrodynamical cosmological simulations, that the origin of GreatCircles can be found in the filaments of cosmological structures, since satellitesaccreted along the same, or close, filaments will orbit the hostroughly on the same plane.

We present high resolution two dimensional velocity fieldsfrom integral field spectroscopy along with derived rotation curves for nine low surface brightness galaxies. This is a positive step forward in terms of both data quality and number of objects studied. We fit NFW and pseudo-isothermal halo models to the observations. We find that the pseudo-isothermal halo better represents the data in most cases than the NFW halo, as the resulting concentrations are lower than would be expected for ΛCDM.

Gravitational lenses on arcseconds scales provide a tool to probe the massdistribution in the lensing galaxies at redshift z ≈ 0.5–1.0. Image positionscan be fitted using simple smooth galaxy mass models, but observed fluxes aremore difficult to match. We analyze the effects of substructures in galaxyhalos to explain such anomalies in the cusp and fold lensing configurationswith different approaches. In the first case we use detailed numerical simulations combined with a Monte Carlo approach to compare predictions from the ΛCDM small scale mass function with observed flux ratios. We extended our analysis down to a mass of ≈105 M๏ for the subhalos. Moreover, we considered extra-halos, like other galaxiessurrounding the primary lens: also if we include these effects we are not ableto reproduce the observed fluxes.This seems to indicate that there is no direct evidence for dark dwarfsatellites from multiple imaged QSOs.In the second case we try to constrain, with a semianalytical approach, the massand the position of a substructure by considering its effects on the flux ofthe images: we add to a smooth lens model, which reproduces well the positionsof the images but not the anomalous fluxes, one or two substructures described as singular isothermal spheres. With substructures in the mass range ~ 106–108 M๏ we are able to fit quite accurately the anomalous fluxes for fold configurations.