Phantom Rings

A phantom using titanium and Landolt rings for image quality evaluation in mammography.

A phantom for image quality evaluation of digital mammography systems is presented and compared to the most widely used phantoms in Europe and the US. The phantom contains objects for subjective detection of Landolt rings (four-alternative, forced-choice task) and for objective calculation of signal-difference-to-noise ratios (SDNR), both in a titanium background within a 12-step wedge. Evaluat...

Phantom appearance of non-phantom matter

Two cosmological models with non-phantom matter having the same expansion of the universe as phantom cosmologies are constructed. The first model is characterized by the evolving gravitational “constant” G and a dark energy component with a non-conserved energy-momentum tensor. The second model includes two interacting components, the dark energy component and the matter component. Closed form ...

Phantom Maps and Chromatic Phantom Maps

In the first part, we determine conditions on spectra X and Y under which either every map from X to Y is phantom, or no nonzero maps are. We also address the question of whether such all or nothing behaviour is preserved when X is replaced with V ∧ X for V finite. In the second part, we introduce chromatic phantom maps. A map is n-phantom if it is null when restricted to finite spectra of type...

Differential Polynomial Rings of Triangular Matrix Rings

phantom energy

We examine cosmological models with generalized phantom energy (GPE). Generalized phantom energy satisfies the supernegative equation of state, but its evolution with the scale factor is generally independent, i.e. not determined by its equation of state. The requirement of general covariance makes the gravitational constant time-dependent. It is found that a large class of distinct GPE models ...