Penobscot Waterways Canals and Waterway Improvements on the Penobscot River, 1816-1921

This article describes the development of the Penobscot River waterway in the period 1816-1921. It discusses the ways in which theses improvements facilitated the movement of logs through the eastern wilderness and allowed for steamboat travel from Old Town to Mattawamkeag prior to the beginning of rail service

Mean-field results on the Anderson impurity model out of equilibrium

We investigate the mean-field phase diagram of the Anderson impurity model out of equilibrium. Generalising the unrestricted Hartree-Fock approach to the non-equilibrium situation we derive and analyse the system of equations defining the critical surface separating the magnetic regime from the non-magnetic one. An exact analytic solution for the phase boundary as a function of the applied voltage is found in the symmetric case. Surprisingly, we find that as soon as there is an asymmetry, even small, between the contacts, no finite voltage is able to destroy the magnetic regime which persists at arbitrary high voltages.Comment: 4 pages, 2 figures (eps files); to appear in PRB Brief Report

Can the Pioneer anomaly be of gravitational origin? A phenomenological answer

In order to satisfy the equivalence principle, any non-conventional mechanism proposed to gravitationally explain the Pioneer anomaly, in the form in which it is presently known from the so-far analyzed Pioneer 10/11 data, cannot leave out of consideration its impact on the motion of the planets of the Solar System as well, especially those orbiting in the regions in which the anomalous behavior of the Pioneer probes manifested itself. In this paper we, first, discuss the residuals of the right ascension \alpha and declination \delta of Uranus, Neptune and Pluto obtained by processing various data sets with different, well established dynamical theories (JPL DE, IAA EPM, VSOP). Second, we use the latest determinations of the perihelion secular advances of some planets in order to put on the test two gravitational mechanisms recently proposed to accommodate the Pioneer anomaly based on two models of modified gravity. Finally, we adopt the ranging data to Voyager 2 when it encountered Uranus and Neptune to perform a further, independent test of the hypothesis that a Pioneer-like acceleration can also affect the motion of the outer planets of the Solar System. The obtained answers are negative.Comment: Latex2e, 26 pages, 6 tables, 2 figure, 47 references. It is the merging of gr-qc/0608127, gr-qc/0608068, gr-qc/0608101 and gr-qc/0611081. Final version to appear in Foundations of Physic

Many-body theory of pump-probe spectra for highly excited semiconductors

We present a unified theory for pump-probe spectra in highly excited semiconductors, which is applicable throughout the whole density regime including the high-density electron-hole BCS state and the low-density excitonic Bose-Einstein condensate (BEC). The analysis is based on the BCS-like pairing theory combined with the Bethe-Salpeter (BS) equation, which first enables us to incorporate the state-filling effect, the band-gap renormalization and the strong/weak electron-hole pair correlations in a unified manner. We show that the electron-hole BCS state is distinctly stabilized by the intense pump-light, and this result strongly suggests that the macroscopic quantum state can be observed under the strong photoexcitation. The calculated spectra considerably deviate from results given by the BCS-like mean field theory and the simple BS equation without electron-hole pair correlation especially in the intermediate density states between the electron-hole BCS state and the excitonic BEC state. In particular, we find the sharp stimulated emission and absorption lines which originate from the optical transition accompanied by the collective phase fluctuation mode in the electron-hole BCS state. From the pump-probe spectral viewpoint, we show that this fluctuation mode changes to the exciton mode with decreasing carrier densityComment: RevTeX 11 pages, 10 figures. To appear in Phys.Rev.B1

Temperature Variation of Ultra Slow Light in a Cold Gas

A model is developed to explain the temperature dependence of the group velocity as observed in the experiments of Hau et al (Nature {\bf397}, 594 (1999)). The group velocity is quite sensitive to the change in the spatial density. The inhomogeneity in the density and its temperature dependence are primarily responsible for the observed behavior.Comment: 12 pages, 4 figure

Optimal bispectrum constraints on single-field models of inflation

We use WMAP 9-year bispectrum data to constrain the free parameters of an 'effective field theory' describing fluctuations in single-field inflation. The Lagrangian of the theory contains a finite number of operators associated with unknown mass scales. Each operator produces a fixed bispectrum shape, which we decompose into partial waves in order to construct a likelihood function. Based on this likelihood we are able to constrain four linearly independent combinations of the mass scales. As an example of our framework we specialize our results to the case of 'Dirac-Born-Infeld' and 'ghost' inflation and obtain the posterior probability for each model, which in Bayesian schemes is a useful tool for model comparison. Our results suggest that DBI-like models with two or more free parameters are disfavoured by the data by comparison with single parameter models in the same class

Keldysh Green's function approach to coherence in a non-equilibrium steady state: connecting Bose-Einstein condensation and lasing

Solid state quantum condensates often differ from previous examples of condensates (such as Helium, ultra-cold atomic gases, and superconductors) in that the quasiparticles condensing have relatively short lifetimes, and so as for lasers, external pumping is required to maintain a steady state. On the other hand, compared to lasers, the quasiparticles are generally more strongly interacting, and therefore better able to thermalise. This leads to questions of how to describe such non-equilibrium condensates, and their relation to equilibrium condensates and lasers. This chapter discusses in detail how the non-equilibrium Green's function approach can be applied to the description of such a non-equilibrium condensate, in particular, a system of microcavity polaritons, driven out of equilibrium by coupling to multiple baths. By considering the steady states, and fluctuations about them, it is possible to provide a description that relates both to equilibrium condensation and to lasing, while at the same time, making clear the differences from simple lasers

Coulomb correlations effects on localized charge relaxation in the coupled quantum dots

We analyzed localized charge time evolution in the system of two interacting quantum dots (QD) (artificial molecule) coupled with the continuous spectrum states. We demonstrated that Coulomb interaction modifies relaxation rates and is responsible for non-monotonic time evolution of the localized charge. We suggested new mechanism of this non-monotonic charge time evolution connected with charge redistribution between different relaxation channels in each QD.Comment: 10 pages, 10 figure