Spherically symmetric ADM gravity with variable G and Lambda(c)

This paper investigates the Arnowitt--Deser--Misner (hereafter ADM) form of spherically symmetric gravity with variable Newton parameter G and cosmological term Lambda(c). The Newton parameter is here treated as a dynamical variable, rather than being merely an external parameter as in previous work on closely related topics. The resulting Hamilton equations are obtained; interestingly, a static solution exists, that reduces to Schwarzschild geometry in the limit of constant G, describing a Newton parameter ruled by a nonlinear differential equation in the radial variable r. A remarkable limiting case is the one for which the Newton parameter obeys an almost linear growth law at large r. An exact solution for G as a function of r is also obtained in the case of vanishing cosmological constant. Some observational implications of these solutions are obtained and briefly discussed.Comment: 16 pages, 2 figures. The presentation has been improved in all section

Sensitivity and Insensitivity of Galaxy Cluster Surveys to New Physics

We study the implications and limitations of galaxy cluster surveys for constraining models of particle physics and gravity beyond the Standard Model. Flux limited cluster counts probe the history of large scale structure formation in the universe, and as such provide useful constraints on cosmological parameters. As a result of uncertainties in some aspects of cluster dynamics, cluster surveys are currently more useful for analyzing physics that would affect the formation of structure than physics that would modify the appearance of clusters. As an example we consider the Lambda-CDM cosmology and dimming mechanisms, such as photon-axion mixing.Comment: 24 pages, 8 eps figures. References added, discussion of scatter in relations between cluster observables lengthene

Dark Matter Candidates: A Ten-Point Test

An extraordinarily rich zoo of non-baryonic Dark Matter candidates has been proposed over the last three decades. Here we present a 10-point test that a new particle has to pass, in order to be considered a viable DM candidate: I.) Does it match the appropriate relic density? II.) Is it {\it cold}? III.) Is it neutral? IV.) Is it consistent with BBN? V.) Does it leave stellar evolution unchanged? VI.) Is it compatible with constraints on self-interactions? VII.) Is it consistent with {\it direct} DM searches? VIII.) Is it compatible with gamma-ray constraints? IX.) Is it compatible with other astrophysical bounds? X.) Can it be probed experimentally?Comment: 29 pages, 12 figure

Type II See-Saw at Collider, Lepton Asymmetry and Singlet Scalar Dark Matter.

We propose an extension of the standard model with a B–L global symmetry that is broken softly at the TeV scale. The neutrinos acquire masses through a type-II seesaw while the lepton (L) asymmetry arises in the singlet sector but without B–L-number violation. The model has the virtue that the scale of L-number violation (Λ) giving rise to neutrino masses is independent of the scale of leptogenesis (Λ'). As a result the model can explain neutrino masses, singlet scalar dark matter and leptogenesis at the TeV scale. The stability of the dark matter is ensured by a surviving Z2 symmetry, which could be lifted at the Planck scale, thereby allowing Planck scale suppressed decay of singlet scalar dark matter particles of mass 3 MeV to e+e- pairs in the Galactic halo. The model also predicts a few hundred GeV doubly charged scalar and a long-lived charged fermion, whose decay can be studied at the Large Hadron Collider (LHC) and International Linear Collider (ILC)