Primordial Non-Gaussian Signatures in the Sky

The presence of non-Gaussian features in the CMB radiation maps represents one of the most long-awaited clues in the search for the actual structure of the primordial radiation. These features could shed some light on the non trivial task of distinguishing the real source of the primeval perturbations leading to large scale structure. In the present paper we briefly review recent work towards finding analytical estimates of the three- and four-point correlation functions and of their zero-lag limits, namely, the skewness and kurtosis, respectively. - Contributed talk to appear in the proceedings of "Birth of the Universe & Fundamental Physics", May 18-21, 1994, Rome, Italy.Comment: 4pp; PostScript fil

Density Perturbations in Chain Inflation

We consider the model of ``Chain Inflation,'' in which the period of inflation in our universe took the form of a long sequence of quantum tunneling events. We find that in the simplest such scenario, in which the tunneling processes are uniform, approximately 10^4 vacua per e-folding of inflation are required in order that the density perturbations produced are of an acceptable size. We arrive at this conclusion through a combination of analytic and numerical techniques, which could also serve as starting points for calculations with more general sets of assumptions.Comment: 28 pages, 16 figures; v2: corrected typos, increased resolution on D=2+1 data point

First Report of Leptomantispa pulchella (Banks, 1912) (Neuroptera: Mantispidae) from Iowa

An adult specimen of Leptomantispa pulchella (Banks) (Neuroptera: Mantispidae) was collected in southeast Iowa. Published records indicate the species is present in southwestern Canada and much of Central America, but this is the first published report of this species from Iowa

Review of Observational Evidence for Dark Matter in the Universe and in upcoming searches for Dark Stars

Over the past decade, a consensus picture has emerged in which roughly a quarter of the universe consists of dark matter. The observational evidence for the existence of dark matter is reviewed: rotation curves of galaxies, weak lensing measurements, hot gas in clusters, primordial nucleosynthesis and microwave background experiments. In addition, a new line of research on Dark Stars is presented, which suggests that the first stars to exist in the universe were powered by dark matter heating rather than by fusion: the observational possibilities of discovering dark matter in this way are discussed.Comment: 14 pages, 7 figures, Conference Proceeding for "Dark Matter and Dark Energy" in Lyon, France, July 200

Fluid Interpretation of Cardassian Expansion

A fluid interpretation of Cardassian expansion is developed. Here, the Friedmann equation takes the form $H^2 = g(\rho_M)$ where $\rho_M$ contains only matter and radiation (no vacuum). The function g(\rhom) returns to the usual 8\pi\rhom/(3 m_{pl}^2) during the early history of the universe, but takes a different form that drives an accelerated expansion after a redshift $z \sim 1$. One possible interpretation of this function (and of the right hand side of Einstein's equations) is that it describes a fluid with total energy density \rho_{tot} = {3 m_{pl}^2 \over 8 \pi} g(\rhom) = \rhom + \rho_K containing not only matter density (mass times number density) but also interaction terms $\rho_K$. These interaction terms give rise to an effective negative pressure which drives cosmological acceleration. These interactions may be due to interacting dark matter, e.g. with a fifth force between particles $F \sim r^{\alpha -1}$. Such interactions may be intrinsically four dimensional or may result from higher dimensional physics. A fully relativistic fluid model is developed here, with conservation of energy, momentum, and particle number. A modified Poisson's equation is derived. A study of fluctuations in the early universe is presented, although a fully relativistic treatment of the perturbations including gauge choice is as yet incomplete.Comment: 25 pages, 1 figure. Replaced with published version. Title changed in journa

Chain Inflation in the Landscape: "Bubble Bubble Toil and Trouble"

In the model of Chain Inflation, a sequential chain of coupled scalar fields drives inflation. We consider a multidimensional potential with a large number of bowls, or local minima, separated by energy barriers: inflation takes place as the system tunnels from the highest energy bowl to another bowl of lower energy, and so on until it reaches the zero energy ground state. Such a scenario can be motivated by the many vacua in the stringy landscape, and our model can apply to other multidimensional potentials. The ''graceful exit'' problem of Old Inflation is resolved since reheating is easily achieved at each stage. Coupling between the fields is crucial to the scenario. The model is quite generic and succeeds for natural couplings and parameters. Chain inflation succeeds for a wide variety of energy scales -- for potentials ranging from 10MeV scale inflation to $10^{16}$ GeV scale inflation.Comment: 31 pages, 3 figures, one reference adde

Dark Stars: the first stars in the universe may be powered by dark matter healing

ManuscriptA new line of research on Dark Stars is reviewed, which suggests that the first stars to exist in the universe were powered by dark matter heating rather than by fusion. Weakly Interacting Massive Particles, which may be there own antipartmers, collect inside the first stars and annihilate to produce a heat source that can power the stars. A new stellar phase results, a Dark Star, powered by dark matter annihilation as long as there is dark matter fuel

Cascade events at IceCube + DeepCore as a definitive constraint on the dark matter interpretation of the PAMELA and Fermi anomalies

Dark matter decaying or annihilating into μ^+μ^- or τ^+τ^- has been proposed as an explanation for the e^± anomalies reported by PAMELA and Fermi. Recent analyses show that IceCube, supplemented by DeepCore, will be able to significantly constrain the parameter space of decays to μ^+μ^-, and rule out decays to τ^+τ^- and annihilations to μ^+μ^- in less than five years of running. These analyses rely on measuring tracklike events in IceCube + DeepCore from down-going ν_μ. In this paper we show that by instead measuring cascade events, which are induced by all neutrino flavors, IceCube + DeepCore can rule out decays to μ^+μ^- in only three years of running, and rule out decays to τ^+τ^- and annihilation to μ^+μ^- in only one year of running. These constraints are highly robust to the choice of dark matter halo profile and independent of dark matter-nucleon crosssection