8 v 1 2 M ar 1 99 8 Ω B and Ω 0 From MACHOs and Local Group Dynamics

ar X iv : a st ro - p h / 98 03 00 8 v 2 5 F eb 1 99 9 Ω B and Ω 0 From MACHOs and Local Group Dynamics

We obtain restrictions on the universal baryon fraction, f B ≡ Ω B /Ω 0 , by assuming that the observed microlensing events towards the Large Magellanic Cloud are due to baryonic MACHOs in the halo of the Galaxy and by extracting a bound to the total mass of the Milky Way from the motion of tracer galaxies in the Local Group. We find a lower bound f B > 0.29 +0.18 −0.15. Consistency with the pr...

ar X iv : a st ro - p h / 97 11 03 5 v 1 4 N ov 1 99 7 CLUSTERS IN VARIOUS COSMOLOGICAL MODELS : ABUNDANCE AND EVOLUTION

The combination of measurements of the local abundance of rich clusters of galaxies and its evolution to higher redshift offers the possibility of a direct measurement of Ω 0 with little contribution from other cosmological parameters. We investigate the significance of recent claims that this evolution indicates that Ω 0 must be small. The most recent cluster velocity dispersion function 1 fro...

ar X iv : a st ro - p h / 99 02 29 8 v 2 1 3 A pr 1 99 9 New limits on Ω Λ and Ω M from old galaxies at high redshift

ar X iv : m at h / 99 05 16 6 v 1 [ m at h . A G ] 2 6 M ay 1 99 9 The Period Lattice for Enriques Surfaces

It is well-known that the isomorphism classes of complex Enriques surfaces are in 1-1 correspondence with a Zariski-open subset (D − H)/Γ of the quotient of the Hermitian symmetric space D for O(2, 10). Here H is a totally geodesic divisor in D and Γ is a certain arithmetic group. In the usual formulation of this result [5], Γ is described as the isometry group of a certain integral lattice N o...

ar X iv : m at h - ph / 0 30 40 12 v 1 9 A pr 2 00 3 Some multidimensional integrable cases of nonholonomic rigid body dynamics ∗

In this paper we study the dynamics of the constrained n–dimensional rigid body (the Suslov problem). We give a review of known integrable cases in three dimensions and present their higher dimensional generalizations. 1 The Suslov problem The equations of nonholonomic systems are not Hamiltonian. They are Hamiltonian with respect to the almost-Poisson brackets [5]. This is the reason that the ...