Hawking radiation from decoherence

It is argued that the thermal nature of Hawking radiation arises solely due to decoherence. Thereby any information-loss paradox is avoided because for closed systems pure states remain pure. The discussion is performed for a massless scalar field in the background of a Schwarzschild black hole, but the arguments should hold in general. The result is also compared to and contrasted with the situation in inflationary cosmology.Comment: 6 pages, to appear in Class. Quantum Gra

Fechnerian Scaling in R: The Package fechner

Fechnerian scaling is a procedure for constructing a metric on a set of objects (e.g., colors, symbols, X-ray films, or even statistical models) to represent dissimilarities among the objects "from the point of view" of a system (e.g., person, technical device, or even computational algorithm) "perceiving" these objects. This metric, called Fechnerian, is computed from a data matrix of pairwise discrimination probabilities or any other pairwise measure which can be interpreted as the degree with which two objects within the set are discriminated from each other. This paper presents the package fechner for performing Fechnerian scaling of object sets in R. We describe the functions of the package. Fechnerian scaling then is demonstrated on real and artificial data sets accompanying the package.

Emergent charge ordering in near half doped Na0.46_{0.46}CoO2_{2}

We have utilized neutron powder diffraction to probe the crystal structure of layered Na$_{x}$CoO$_{2}$ near the half doping composition of $x=$0.46 over the temperature range of 2 to 600K. Our measurements show evidence of a dynamic transition in the motion of Na-ions at 300K which coincides with the onset of a near zero thermal expansion in the in-plane lattice constants. The effect of the Na-ordering on the CoO$_{2}$ layer is reflected in the octahedral distortion of the two crystallographically inequivalent Co-sites and is evident even at high temperatures. We find evidence of a weak charge separation into stripes of Co$^{+3.5+\epsilon}$ and Co$^{+3.5-\epsilon}$, $\epsilon\sim0.06e$ below \Tco=150K. We argue that changes in the Na(1)-O bond lengths observed at the magnetic transition at \tm=88K reflect changes in the electronic state of the CoO$_{2}$ layerComment: 7 pages, 6 figures, in press Phys. Rev.

Time-resolved measurement of the local equivalence ratio in a gaseous propane injection process using laser-induced gratings

This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/abstract.cfm?URI=oe-14-26-12994. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.Peer reviewedPublisher PD

The Water Monomer on the Basal Plane of Ice Iₕ: An Effective Pair, Central Force Potential Model of the Static Interaction

The H2O-H2O intermolecular central force potential of Lemberg and Stillinger is used to obtain optimal binding energy surfaces, vibrational frequencies, and bonding configurations of an adsorbed water monomer on a model basal plane of ice Ih. The monomer interacts (pairwise) with 50 molecules arranged in two layers of the unrelaxed bulk ice lattice. The results of calculations for three model surface sites of differing proton arrangement indicate the existence of diffusion barriers of the order of 2.5 kcal/mole and optimal monomer bonding sites at about 9 kcal/mole with nonepitaxial characteristics. Perspective computer-drawn plots of the optimal monomer binding energy surfaces and the center of mass height of the monomer over each of the three sites are shown. Similar diagrams showing the variations in the monomer dipole orientation along walks across the sites are also presented. Mean residence times and mean path lengths of the monomer diffusing over the model ice surface are estimated from the monomer vibrational modes and the estimated average diffusion barriers and binding energies. A sample diffusion path is discussed

Hawking radiation from the quantum Lemaitre-Tolman-Bondi model

In an earlier paper, we obtained exact solutions of the Wheeler-DeWitt equation for the Lemaitre-Tolman-Bondi (LTB) model of gravitational collapse, employing a lattice regularization. In this paper, we derive Hawking radiation in non-marginally bound models from our exact solutions. We show that a non-vanishing energy function does not spoil the (approximate) Planck spectrum near the horizon. We can also reliably compute corrections to the Bogoliubov coefficient because our solutions are exact. The corrections are obtained by going beyond the near horizon region and are shown to introduce additional greybody factors, which modify the black body spectrum of radiation from the black hole.Comment: 14 page

Solving the Problem of Time in Mini-superspace: Measurement of Dirac Observables

One solution to the so-called problem of time is to construct certain Dirac observables, sometimes called evolving constants of motion. There has been some discussion in the literature about the interpretation of such observables, and in particular whether single Dirac observables can be measured. Here we clarify the situation by describing a class of interactions that can be said to implement measurements of such observables. Along the way, we describe a useful notion of perturbation theory for the rigging map eta of group averaging (sometimes loosely called the physical state "projector"), which maps states from the auxiliary Hilbert space to the physical Hilbert space.Comment: 12 pages, ReVTe

The Design of Foundations for the World’s Tallest Buildings

The talk presents the essential requirements for the design of foundations for the world’s tallest buildings from a geotechnical perspective, discusses briefly the basic foundation types and several key principles to remember, including the need for close structural engineer and geotechnical engineer cooperation. The special in-situ testing and load testing techniques commonly used are also presented. International case histories where performance has been monitored are used to illustrate some of the basic points as well as to compare prediction with performance. As an additional feature, the experience of gradually increasing allowable bearing pressures in a given geology over a sufficient time span to observe performance is also presented using Chicago high-rise experience

Semiclassical states for quantum cosmology

In a metric variable based Hamiltonian quantization, we give a prescription for constructing semiclassical matter-geometry states for homogeneous and isotropic cosmological models. These "collective" states arise as infinite linear combinations of fundamental excitations in an unconventional "polymer" quantization. They satisfy a number of properties characteristic of semiclassicality, such as peaking on classical phase space configurations. We describe how these states can be used to determine quantum corrections to the classical evolution equations, and to compute the initial state of the universe by a backward time evolution.Comment: 13 page