Anisotropy of the Microwave Sky at 90 GHz: Results from Python II

We report on additional observations of degree scale anisotropy at 90~GHz from the Amundsen-Scott South Pole Station in Antarctica. Observations during the first season with the Python instrument yielded a statistically significant sky signal; in this paper we report the confirmation of that signal with data taken in the second year, and on results from an interleaving set of fields.Comment: 10 pages, plus 2 figures. Postscript and uufiles versions available via anonymous ftp at ftp://astro.uchicago.edu/pub/astro/ruhl/pyI

Three-dimensional Gross-Pitaevskii solitary waves in optical lattices: stabilization using the artificial quartic kinetic energy induced by lattice shaking

In this Letter, we show that a three-dimensional Bose-Einstein solitary wave can become stable if the dispersion law is changed from quadratic to quartic. We suggest a way to realize the quartic dispersion, using shaken optical lattices. Estimates show that the resulting solitary waves can occupy as little as $\sim 1/20$-th of the Brillouin zone in each of the three directions and contain as many as $N = 10^{3}$ atoms, thus representing a \textit{fully mobile} macroscopic three-dimensional object.Comment: 8 pages, 1 figure, accepted in Phys. Lett.

The impact of Pinus halepensis mill. afforestation on mediterranean spontaneous vegetation: do soil treatment and canopy cover matter?

We investigated central Mediterranean Pinus halepensis plantations under semi-arid climate in order to evaluate the combined effect of soil treatment and afforestation practices on spontaneous plant species composition, richness and evenness, and on the trend and speed of vegetation dynamics. Phytosociological relevés of three different plot typologies, i.e. (1) soil-treatment and plantation, (2) only soil-treatment, (3) no soil-treatment and no plantation, were compared by (a) multivariate analysis and (b) with reference to species richness and evenness. Moreover, in order to compare vegetation dynamics within the plantations with those ones ongoing in semi-natural garrigue communities, we compared life form and syntaxonomic spectra between phytosociological relevés taken at 8 years of distance. DCA showed that floristic species composition and similarity are influenced by the canopy cover of Pine trees as well as by soil-treatment practices. Although species richness and evenness are not clearly related to neither soil treatment nor Pine afforestation, canopy cover clearly plays a major role: in fact, the highest Ph cover rates correspond to the lowest values of understory species richness. This is true also if only species of biogeographical/conservation interest are considered. Regarding vegetation dynamics, sites with dense Pine canopy cover evolve much slower than the adjacent garrigue communities. The same factors invoqued to explain the patterns of floristic composition and similarity (i.e. allelopathy and competition for light, water and nutrients) may also explain the lowering of diversity of therophytes and the strong decline of the cover perfomed by both therophytes and hemicryptophytes underneath the canopy of dense Ph plantations. Thus, in sites where Ph cover exceeds about 80%, thinning is recommended not only in order to accelerate succession, but also to give a natural ‘shape’ to afforestations

Conservation and concealment in SpeciesBanking.com, USA: an analysis of neoliberal performance in the species offsetting industry

Market-based strategies are promoted as neoliberal governance solutions to environmental problems, from local to global scales. Tradable mitigation schemes are proliferating. These include species banking, which enables payments for the purchase of species credits awarded to conserved areas to offset development impacts on protected species elsewhere. An analysis of species banks in the USA through a survey of data from the website www.SpeciesBanking.com (established as a ‘clearing house’ for species banking information) was complemented by questionnaire material from USA bank managers. The number of USA species banks has increased rapidly, bank area ownership and management is consolidated in a small number of organizations, and public information on species credit price is limited. In interrogating the case material, the roles of specific economic policies associated with neoliberalism are considered, focusing on the extension of privatization, de- and re-regulation and marketization into the arena of environmental conservation, and commodification processes as manifested in species banking. Problematic ecological and distributive ‘concealments’ in species banking include the ‘development-led’ nature of conservation banking, tendencies towards net biodiversity loss, and an emphasis on supporting conservation-related wealth accumulation by larger landowners and investors

Focusing of Intense Subpicosecond Laser Pulses in Wedge Targets

Two dimensional particle-in-cell simulations characterizing the interaction of ultraintense short pulse lasers in the range 10^{18} \leq I \leq 10^{20} W/cm^{2} with converging target geometries are presented. Seeking to examine intensity amplification in high-power laser systems, where focal spots are typically non-diffraction limited, we describe key dynamical features as the injected laser intensity and convergence angle of the target are systematically varied. We find that laser pulses are focused down to a wavelength with the peak intensity amplified by an order of magnitude beyond its vacuum value, and develop a simple model for how the peak location moves back towards the injection plane over time. This performance is sustained over hundreds of femtoseconds and scales to laser intensities beyond 10^{20} W/cm^{2} at 1 \mu m wavelength.Comment: 5 pages, 6 figures, accepted for publication in Physics of Plasma

Spinfoams in the holomorphic representation

We study a holomorphic representation for spinfoams. The representation is obtained via the Ashtekar-Lewandowski-Marolf-Mour\~ao-Thiemann coherent state transform. We derive the expression of the 4d spinfoam vertex for Euclidean and for Lorentzian gravity in the holomorphic representation. The advantage of this representation rests on the fact that the variables used have a clear interpretation in terms of a classical intrinsic and extrinsic geometry of space. We show how the peakedness on the extrinsic geometry selects a single exponential of the Regge action in the semiclassical large-scale asymptotics of the spinfoam vertex.Comment: 10 pages, 1 figure, published versio

Absorption of Ultrashort Laser Pulses in Strongly Overdense Targets

We report on the first absorption experiments of sub-10 fs high-contrast Ti:Sa laser pulses incident on solid targets. The very good contrast of the laser pulse assures the formation of a very small pre-plasma and the pulse interacts with the matter close to solid density. Experimental results indicate that p-polarized laser pulses are absorbed up to 80 percent at 80 degrees incidence angle. The simulation results of PSC PIC code clearly confirm the observations and show that the collisionless absorption works efficiently in steep density profiles

Brueckner-Goldstone perturbation theory for the half-filled Hubbard model in infinite dimensions

We use Brueckner-Goldstone perturbation theory to calculate the ground-state energy of the half-filled Hubbard model in infinite dimensions up to fourth order in the Hubbard interaction. We obtain the momentum distribution as a functional derivative of the ground-state energy with respect to the bare dispersion relation. The resulting expressions agree with those from Rayleigh-Schroedinger perturbation theory. Our results for the momentum distribution and the quasi-particle weight agree very well with those obtained earlier from Feynman-Dyson perturbation theory for the single-particle self-energy. We give the correct fourth-order coefficient in the ground-state energy which was not calculated accurately enough from Feynman-Dyson theory due to the insufficient accuracy of the data for the self-energy, and find a good agreement with recent estimates from Quantum Monte-Carlo calculations.Comment: 15 pages, 8 fugures, submitted to JSTA

COMPASS: a 2.6m telescope for CMBR polarization studies

COMPASS (COsmic Microwave Polarization at Small Scale) is an experiment devoted to measuring the polarization of the CMBR. Its design and characteristics are presented

New CMB Power Spectrum Constraints from MSAMI

We present new cosmic microwave background (CMB) anisotropy results from the combined analysis of the three flights of the first Medium Scale Anisotropy Measurement (MSAM1). This balloon-borne bolometric instrument measured about 10 square degrees of sky at half-degree resolution in 4 frequency bands from 5.2 icm to 20 icm with a high signal-to-noise ratio. Here we present an overview of our analysis methods, compare the results from the three flights, derive new constraints on the CMB power spectrum from the combined data and reduce the data to total-power Wiener-filtered maps of the CMB. A key feature of this new analysis is a determination of the amplitude of CMB fluctuations at $\ell \sim 400$. The analysis technique is described in a companion paper by Knox.Comment: 9 pages, 6 included figure