Constraints on dark energy and cosmic topology

A non-trivial spatial topology of the Universe is a potentially observable attribute, which can be probed through the circles-in-the-sky for all locally homogeneous and isotropic universes with no assumptions on the cosmological parameters. We show how one can use a possible circles-in-the-sky detection of the spatial topology of globally homogeneous universes to set constraints on the dark energy equation of state parameters.Comment: 6 pages, 1 figure. To appear in Int. J. Mod. Phys. A (2009). From a talk presented at the Seventh Alexander Friedmann International Seminar on Gravitation and Cosmolog

Traveler to Arcadia: Margaret Bourke-White in Italy, 1943-1944

DURING the nineteenth century, American artists, writers, and intellectuals flocked to Italy, seeking an escape from the exigencies of the modern world. To them, Italy was a dream realm, a golden Arcadia. Some, however, like the painter Thomas Cole, saw through the dream and brought back to America a stark message about the displacement of nations and the fall of empires. In the 183os, on the eve of America\u27s westward expansion, Cole painted his Course of Empire series, tracing the progress of Rome from an Arcadian State, to the Consummation of Empire, to Destruction, finally ending in Desolation. Cole was warning his countrymen not to follow in Rome\u27s disastrous path. 1 Again, in the mid-twentieth century, Americans who went to Italy (though not as tourists), would bring back messages of warning even more urgent because they were responses to the rise of the fascist Roman Empire of Benito Mussolini. At first, in the I930S, Americans were impressed with the new Italy, its sense of order and cleanliness, and its success in industrialization and the utilization of technology. Increasingly, however, the dark side of Mussolini\u27s innovations became apparent, and with the outbreak of World War II, the fascist dream became the world\u27s nightmare

Arkansas Soybean Performance Tests 2008

Soybean cultivar performance tests are conducted each year in Arkansas by the University of Arkansas Division of Agriculture. The tests provide information to companies developing cultivars and/or marketing seed within the state, and aid the Arkansas Cooperative Extension Service in formulating cultivar recommendations for soybean producer

Arkansas Soybean Performance Tests 2007

Soybean cultivar performance tests are conducted each year in Arkansas by the University of Arkansas Division of Agriculture. The tests provide information to companies developing cultivars and/or marketing seed within the State, and aid the Arkansas Cooperative Extension Service in formulating cultivar recommendations for soybean producers

Arkansas Corn and Grain Sorghum Performance Tests 2003

Corn and grain sorghum performance tests are conducted each year in Arkansas by the University of Arkansas Division of Agriculture. The tests provide information to companies marketing seed within the state, and aid the Arkansas Cooperative Extension Service in formulating recommendations for producers

Generalizing the running vacuum energy model and comparing with the entropic-force models

We generalize the previously proposed running vacuum energy model by including a term proportional to \dot{H}, in addition to the existing H^2 term. We show that the added degree of freedom is very constrained if both low redshift and high redshift data are taken into account. Best-fit models are undistinguishable from LCDM at the present time, but could be distinguished in the future with very accurate data at both low and high redshifts. We stress the formal analogy at the phenomenological level of the running vacuum models with recently proposed dark energy models based on the holographic or entropic point of view, where a combination of \dot{H} and H^2 term is also present. However those particular entropic formulations which do not have a constant term in the Friedmann equations are not viable. The presence of this term is necessary in order to allow for a transition from a decelerated to an accelerated expansion. In contrast, the running vacuum models, both the original and the generalized one introduced here contain this constant term in a more natural way. Finally, important conceptual issues common to all these models are emphasized.Comment: Version accepted in Phys. Rev. D. LaTeX, 24 pages and one figure. Slightly extended discussio