M. May

Challenges to the DGP model from horizon-scale growth and geometry

We conduct a Markov Chain Monte Carlo study of the Dvali-Gabadadze-Porrati (DGP) selfaccelerating braneworld scenario given the cosmic microwave background (CMB) anisotropy, supernovae and Hubble constant data by implementing an effective dark energy prescription for modified gravity into a standard Einstein-Boltzmann code. We find no way to alleviate the tension between distance measures and horizon scale growth in this model. Growth alterations due to perturbations propagating into the bulk appear as excess CMB anisotropy at the lowest multipoles. In a flat

Experimental observation of the Σ hypernuclei, Σ6H and Σ16C

Abstract The hypernuclei Σ 6 H and Σ 16 C were observed by the (K − , π + ) reaction on targets of 6 Li and liquid O, respectively, at 713 MeV/ c incident K − momentum. Structure is seen in Σ 6 H which may be interpreted in terms of particle-hole excitations similar to the previously observed states in Λ 6 Li. The inablitity to resolve individual Σ hypernuclear levels in Σ 16 C, due in part to the excitation of non-coherent states as a result of the large momentum transfer of about 130 MeV/ c , precludes the extraction of the Σ-nucleus spin-orbit potential strength. The Σ-nucleus well depth appears to be 7 to 10 MeV less than that for the Λ.

Weighing neutrinos with galaxy cluster surveys

Large future galaxy cluster surveys, combined with cosmic microwave background observations, can achieve a high sensitivity to the masses of cosmologically important neutrinos. We show that a weak lensing selected sample of > or approximately 100,000 clusters could tighten the current upper bound on the sum of masses of neutrino species by an order of magnitude, to a level of 0.03 eV. Since this statistical sensitivity is below the best existing lower limit on the mass of at least one neutrino species, a future detection is likely, provided that systematic errors can be controlled to a similar level.

States of 12ΛC formed in the reaction 12C(K−, π−)☆

Abstract States of 12 Λ C formed in the (K − , π − ) reaction have been studied for momentum transfers up to 260 MeV/ c , using an incident K − beam of 800 MeV/ c momentum. The angular distributions for the g.s. and for a peak at 11 meV have been measured between 0° and 19° in the laboratory. Limits on the splitting of the 11 MeV peak and on the formation of low-lying excited states are given.

Probing cosmology with weak lensing peak counts

We propose counting peaks in weak lensing (WL) maps, as a function of their height, to probe models of dark energy and to constrain cosmological parameters. Because peaks can be identified in two-dimensional WL maps directly, they can provide constraints that are free from potential selection effects and biases involved in identifying and determining the masses of galaxy clusters. As a pilot study, we have run cosmological N-body simulations to produce WL convergence maps in three models with different constant values of the dark energy equation-of-state parameter,

States of

w=\ensuremath{-}0.8

^{12}

,

C (

\ensuremath{-}1

\Lambda

, and

) Formed in the Reaction

\ensuremath{-}1.2