Cosmological implications of a Dark Matter self-interaction energy density

We investigate cosmological constraints on an energy density contribution of elastic dark matter self-interactions characterized by the mass of the exchange particle and coupling constant. Because of the expansion behaviour in a Robertson-Walker metric we investigate self-interacting dark matter that is warm in the case of thermal relics. The scaling behaviour of dark matter self-interaction energy density shows that it can be the dominant contribution (only) in the very early universe. Thus its impact on primordial nucleosynthesis is used to restrict the interaction strength, which we find to be at least as strong as the strong interaction. Furthermore we explore dark matter decoupling in a self-interaction dominated universe, which is done for the self-interacting warm dark matter as well as for collisionless cold dark matter in a two component scenario. We find that strong dark matter self-interactions do not contradict super-weak inelastic interactions between self-interacting dark matter and baryonic matter and that the natural scale of collisionless cold dark matter decoupling exceeds the weak scale and depends linearly on the particle mass. Finally structure formation analysis reveals a linear growing solution during self-interaction domination; however, only non-cosmological scales are enhanced.Comment: 14 pages, 14 figures; version published in Phys. Rev.

Centrality Scaling of the pTp_T Distribution of Pions

From the preliminary data of PHENIX on the centrality dependence of the $\pi^0$ spectrum in $p_T$ at midrapidity in heavy-ion collisions, we show that a scaling behavior exists that is independent of the centrality. It is then shown that $$ degrades with increasing $N_{\rm part}$ exponentially with a decay constant that can be quantified. A scaling distribution in terms of an intuitive scaling variable is derived that is analogous to the KNO scaling. No theoretical models are used in any part of this phenomenological analysis.Comment: 4 pages RevTex, 5 figures include

Is there Quark Matter in (Low-Mass) Pulsars?

The effect of the QCD phase transition is studied for the mass-radius relation of compact stars and for hot and dense matter at a given proton fraction used as input in core-collapse supernova simulations. The phase transitions to the 2SC and CFL color superconducting phases lead to stable hybrid star configurations with a pure quark matter core. In supernova explosions quark matter could be easily produced due to $\beta$-equilibrium, small proton fractions and nonvanishing temperatures. A low critical density for the phase transition to quark matter is compatible with present pulsar mass measurements.Comment: 4 pages, 3 figures, talk given at the QM2008 conference, Jaipur, India, February 4-10, 2008, JPG in pres

Ecology of the benthos of the lower Chesapeake Bay (Maryland)

The spatially complex lower Chesapeake Bay estuary is characterized by a variety of bottom types and hydrodynamic regimes. to account for this physically-induced variability a benthic habitat delineation scheme was developed based on existing knowledge of physical and geological characteristics. Within the context of this scheme a series of studies were conducted to identify biotic response to and interactions with the physical, chemical and geological gradients that characterize the lower Chesapeake Bay. These studies characterized organism distribution and abundance patterns within the lower bay and identified processes controlling those patterns. The biological community of the polyhaline basin habitat, an area characterized by moderate tidal, but little wave-induced bottom disturbance was defined and described for the first time. This community is characterized by large tube and burrow builders, epifaunal and commensal organisms, shallowly-distributed, short-lived species and deeply-dwelling predators. The basin is also the preferred habitat of overwintering blue crabs and an area where biotic sediment reworking generally exceeds physical reworking. The results of these studies suggest that within the lower Chesapeake Bay estuarine system, the relative importance of biological versus physical processes in maintaining the structure and dynamics of estuarine benthic communities will be greatest in the basin habitat

Baltimore Harbor and channels aquatic benthos investigations at the Wolf Trap alternate disposal site in lower Chesapeake Bay : final report

The disposal of dredged material from channel deepening projects is a major anthropogenic process influencing· benthic communities of coastal aquatic systems. Such activities are important because benthic subsystems and component organisms play major roles in the functioning of estuarine ecosystems. Benthic invertebrates are major prey items in the diets of fishes and crabs (Arntz and Brunswig 1975, Virnstein 1977, Arntz 1978, Blundon and Kennedy 1982, Lunz and Kendall 1982, Moeller et al. 1985, Pihl et al. 1992). As secondary producers capable of utilizing trophic resources from a variety of sources (e.g. detritus, algae, bacteria), they provide important links to higher trophic levels. From microbes to macrofauna, benthic organisms also have major impacts on the cycling of nutrients (Diaz and Schaffner 1990, Mayer et al. in review), contaminants (Lee and Swartz 1980, Diaz and Schaffner 1990, and Schaffner et al. 1992), and sediments (Rhoads and Boyer 1982, Diaz and Schaffner 1990). Macrobenthic organisms exhibit many properties that make them good indicators of environmental conditions (e.g. limited mobility, a variety of life histories, a range of physiological tolerances). Numerous studies have demonstrated that spatial and temporal comparisons of the kinds and abundances of benthic organisms are sensitive and important methods for assessing dredge material disposal effects on aquatic systems. This study documents changes in the structure of lower Chesapeake Bay macrobenthic communities affected by dredged material disposal. The Corps is completing an assessment of changes in benthic resource value at the Wolf Trap Alternate Disposal Site using the Benthic Resource Assessment Technique (BRAT)