16 research outputs found
Inflation and Preheating in NO models
We study inflationary models in which the effective potential of the inflaton
field does not have a minimum, but rather gradually decreases at large .
In such models the inflaton field does not oscillate after inflation, and its
effective mass becomes vanishingly small, so the standard theory of reheating
based on the decay of the oscillating inflaton field does not apply. For a long
time the only mechanism of reheating in such non-oscillatory (NO) models was
based on gravitational particle production in an expanding universe. This
mechanism is very inefficient. We will show that it may lead to cosmological
problems associated with large isocurvature fluctuations and overproduction of
dangerous relics such as gravitinos and moduli fields. We also note that the
setting of initial conditions for the stage of reheating in these models should
be reconsidered. All of these problems can be resolved in the context of the
recently proposed scenario of instant preheating if there exists an interaction
of the inflaton field with another scalar field
. We show that the mechanism of instant preheating in NO models is much
more efficient than the usual mechanism of gravitational particle production
even if the coupling constant is extremely small, .Comment: 10 pages, revte
Top-down and bottom-up control of infauna varies across the saltmarsh landscape
Author Posting. © The Author(s), 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Journal of Experimental Marine Biology and Ecology 357 (2008): 20-34, doi:10.1016/j.jembe.2007.12.003.Responses of infaunal saltmarsh benthic invertebrates to whole-ecosystem fertilization and
predator removal were quantified in Plum Island Estuary, Massachusetts, USA. Throughout a
growing season, we enriched an experimental creek on each flooding tide to 70 mM NO3
- and 4
mM PO4
-3 (a 10 x increase in loading above background), and we reduced Fundulus heteroclitus
density by 60% in a branch of the fertilized and a reference creek. Macroinfauna and meiofauna
were sampled in creek (mudflat and creek wall), marsh edge (tall form Spartina alterniflora) and
marsh platform (Spartina patens and stunted S. alterniflora) habitats before and after treatments
were begun; responses were tested with BACI-design statistics. Treatment effects were most
common in the mid-range of the inundation gradient. Most fertilization effects were on creek
wall where ostracod abundance increased, indices of copepod reproduction increased and
copepod and annelid communities were altered. These taxa may use epiphytes (that respond
rapidly to fertilization) of filamentous algae as a food source. Killifish reduction effects on
meiobenthic copepod abundance were detected at the marsh edge and suggest predator
limitation. Fish reduction effects on annelids did not suggest top-down regulation in any habitat;
however, fish reduction may have stimulated an increased predation rate on annelids by grass
shrimp. Interactions between fertilization and fish reduction occurred under S. patens canopy
where indirect predator reduction effects on annelids were indicated. No effects were observed
in mudflat or stunted S. alterniflora habitats. Although the responses of infauna to fertilization
and predator removal were largely independent and of similar mild intensity, our data suggests
that the effects of ecological stressors vary across the marsh landscape.This research was supported by the National Science
Foundation under Grants No. 0213767 and 9726921