A 'Dysonization' scheme for identifying quasi-particles using non-Hermitian quantum mechanics.

Dyson analysed the low-energy excitations of a ferromagnet using a Hamiltonian that was non-Hermitian with respect to the standard inner product. This allowed for a facile rendering of these excitations (known as spin waves) as weakly interacting bosonic quasi-particles. More than 50 years later, we have the full denouement of the non-Hermitian quantum mechanics formalism at our disposal when considering Dyson's work, both technically and contextually.

Detecting chameleon dark energy via an electrostatic analogy.

The late-time accelerated expansion of the Universe could be caused by a scalar field that is screened on small scales, as in the case of chameleon or symmetron scenarios. We present an analogy between such scalar fields and electrostatics, which allows calculation of the field profile for general extended bodies. Interestingly, the field demonstrates a "lightning rod" effect, where it becomes enhanced near the ends of a pointed or elongated object.

Drip paintings and fractal analysis.

It has been claimed that fractal analysis can be applied to unambiguously characterize works of art such as the drip paintings of Jackson Pollock. This academic issue has become of more general interest following the recent discovery of a cache of disputed Pollock paintings. We definitively demonstrate here, by analyzing paintings by Pollock and others, that fractal criteria provide no information about artistic authenticity.

Nearly scale invariant spectrum of gravitational radiation from global phase transitions.

Using a large N sigma model approximation we explicitly calculate the power spectrum of gravitational waves arising from a global phase transition in the early Universe and we confirm that it is scale invariant, implying an observation of such a spectrum may not be a unique feature of inflation. Moreover, the predicted amplitude can be over 3 orders of magnitude larger than the naive dimensional estimate, implying that even a transition that occurs after inflation may dominate in cosmic microwave background polarization or other gravity wave signals.

Fractal Analysis: revisiting Pollock's drip paintings.

We investigate the contentions that Jackson Pollock's drip paintings are fractals produced by the artist's Lévy distributed motion and that fractal analysis may be used to authenticate works of uncertain provenance. We find that the paintings exhibit fractal characteristics over too small a range to be usefully considered as fractal; their limited fractal characteristics are easily generated without Lévy motion, both by freehand drawing and gaussian random motion. Several problems must therefore be addressed before fractal analysis can be used to authenticate paintings.