Uranium triamidoamine chemistry

Uranium triamidoamine chemistry is reviewed.</p

Black holes and gravitational waves in string cosmology

Pre--big bang models of inflation based on string cosmology produce a stochastic gravitational wave background whose spectrum grows with decreasing wavelength, and which may be detectable using interferometers such as LIGO. We point out that the gravitational wave spectrum is closely tied to the density perturbation spectrum, and that the condition for producing observable gravitational waves is very similar to that for producing an observable density of primordial black holes. Detection of both would provide strong support to the string cosmology scenario.Comment: 6 pages RevTeX fil

CMB Power Spectrum from Noncommutative Spacetime

Very recent CMB data of WMAP offers an opportunity to test inflation models, in particular, the running of spectral index is quite new and can be used to rule out some models. We show that an noncommutative spacetime inflation model gives a good explanation of these new results. In fitting the data, we also obtain a relationship between the noncommutative parameter (string scale) and the ending time of inflation.Comment: 8 pages, 2 figures; v2: refs. added and minor corrections; v3: further minor correctio

Power Spectrum in Krein Space Quantization

The power spectrum of scalar field and space-time metric perturbations produced in the process of inflation of universe, have been presented in this paper by an alternative approach to field quantization namely, Krein space quantization [1,2]. Auxiliary negative norm states, the modes of which do not interact with the physical world, have been utilized in this method. Presence of negative norm states play the role of an automatic renormalization device for the theory.Comment: 8 pages, appear in Int. J. Theor. Phy

Running spectral index from shooting-star moduli

We construct an inflationary model that is consistent with both large non-Gaussianity and a running spectral index. The scenario of modulated inflation suggests that modulated perturbation can induce the curvature perturbation with a large non-Gaussianity, even if the inflaton perturbation is negligible. Using this idea, we consider a multi-field extension of the modulated inflation scenario and examine the specific situation where different moduli are responsible for the perturbation at different scales. We suppose that the additional moduli (shooting-star moduli) is responsible for the curvature perturbation at the earlier inflationary epoch and it generates the fluctuation with n>1 spectral index at this scale. After a while, another moduli (or inflaton) takes the place and generates the perturbation with n<1. At the transition point the two fluctuations are comparable with each other. We show how the spectral index is affected by the transition induced by the shooting-star moduli.Comment: 14 pages, latex, accepted for publication in JHE

Possible Constraints on the Duration of Inflationary Expansion from Quantum Stress Tensor Fluctuations

We discuss the effect of quantum stress tensor fluctuations in deSitter spacetime upon the expansion of a congruence of timelike geodesics. We treat a model in which the expansion fluctuations begin on a given hypersurface in deSitter spacetime, and find that this effect tends to grow, in contrast to the situation in flat spacetime. This growth potentially leads to observable consequences in inflationary cosmology in the form of density perturbations which depend upon the duration of the inflationary period. In the context of our model, the effect may be used to place upper bounds on this duration.Comment: 21 pages, no figures; Sect. IV rewritten and expanded, several comments and references adde

Electrical activation and electron spin coherence of ultra low dose antimony implants in silicon

We implanted ultra low doses (2x10^11 cm-2) of 121Sb ions into isotopically enriched 28Si and find high degrees of electrical activation and low levels of dopant diffusion after rapid thermal annealing. Pulsed Electron Spin Resonance shows that spin echo decay is sensitive to the dopant depths, and the interface quality. At 5.2 K, a spin decoherence time, T2, of 0.3 ms is found for profiles peaking 50 nm below a Si/SiO2 interface, increasing to 0.75 ms when the surface is passivated with hydrogen. These measurements provide benchmark data for the development of devices in which quantum information is encoded in donor electron spins

Dark Matter and Dark Energy via Non-Perturbative (Flavour) Vacua

A non-perturbative field theoretical approach to flavour physics (Blasone-Vitiello formalism) has been shown to imply a highly non-trivial vacuum state. In a previous work, we implemented the approach on a simple supersymmetric model (free Wess-Zumino), with flavour mixing, which was regarded as a model for free neutrinos and sneutrinos. The resulting effective vacuum (called "flavour vacuum") was found to be characterized by a strong SUSY breaking. In this paper we explore the phenomenology of the model and we argue that the flavour vacuum is a consistent source for both Dark Energy (thanks to the bosonic sector of the model) and Dark Matter (via the fermionic one). Quite remarkably, besides the parameters connected with neutrino physics, in this model no other parameters have been introduced, possibly leading to a predictive theory of Dark Energy/Matter. Despite its oversimplification, such a toy model already seems capable to shed some light on the observed energy hierarchy between neutrino physics, Dark Energy and Dark Matter. Furthermore, we move a step forth in the construction of a more realistic theory, by presenting a novel approach for calculating relevant quantities and hence extending some results to interactive theories, in a completely non-perturbative way.Comment: 14 pages, 2 figure

Health Technology Scenarios and Implications for Spectrum

Supporting Informatio

Efficient Simulations of Early Structure Formation and Reionization

We present a method to construct semi-numerical ``simulations'', which can efficiently generate realizations of halo distributions and ionization maps at high redshifts. Our procedure combines an excursion-set approach with first-order Lagrangian perturbation theory and operates directly on the linear density and velocity fields. As such, the achievable dynamic range with our algorithm surpasses the current practical limit of N-body codes by orders of magnitude. This is particularly significant in studies of reionization, where the dynamic range is the principal limiting factor. We test our halo-finding and HII bubble-finding algorithms independently against N-body simulations with radiative transfer and obtain excellent agreement. We compute the size distributions of ionized and neutral regions in our maps. We find even larger ionized bubbles than do purely analytic models at the same volume-weighted mean hydrogen neutral fraction. We also generate maps and power spectra of 21-cm brightness temperature fluctuations, which for the first time include corrections due to gas bulk velocities. We find that velocities widen the tails of the temperature distributions and increase small-scale power, though these effects quickly diminish as reionization progresses. We also include some preliminary results from a simulation run with the largest dynamic range to date: a 250 Mpc box that resolves halos with masses M >~ 2.2 x10^8 M_sun. We show that accurately modeling the late stages of reionization requires such large scales. The speed and dynamic range provided by our semi-numerical approach will be extremely useful in the modeling of early structure formation and reionization.Comment: 13 pages, 10 figures; ApJ submitte