Isotopic overabundances and the energetic particle model of solar flares

According to the energetic particle model of solar flares particles are efficiently accelerated in the magnetic field loop of an active region (AR) by hydromagnetic turbulence. It is demonstrated that the isotopic overabundances observed in some flares are not a consequence of the flare itself but are characteristic of the plasma in the AR. Only when a flare releases the plasma into the interplanetary space it is possible to observe this anomalous composition at spacecraft locations

Creative Destruction in Cariou v. Prince

When portrait photographer Patrick Cariou saw that his original photos of Jamaican Rastafarians had been used by renowned appropriation artist Richard Prince in a collage series called “Canal Zone”—sales of which grossed Prince close to $11 million—Cariou sued for copyright infringement in the Southern District of New York. The decision was held in Cariou’s favor and was blasted by commentators as “frightening,” “[k]afkaesque,” and “untenable.” Much of that criticism wasn’t aimed at the court’s rejection of appropriation as fair use, but rather at its authorized remedy: to “deliver up for impounding, destruction, or other disposition, as Plaintiff determines,” all unsold works from the “Canal Zone” series. The legal status of appropriation art in the Second Circuit has long been a matter of some ambiguity. The Second Circuit subsequently reversed and remanded the majority decision, and in the process unleashed a revised, but largely formless fair use standard: whether the reasonable observer can detect new meaning in the work in question. The public furor surrounding the district court’s remedy may partially explain why the Second Circuit took special pains to clarify that the court-ordered destruction of Richard Prince’s art would be “improper and against the public interest.” But the truth of that statement isn’t exactly self-evident. This post was originally published on the Cardozo Arts & Entertainment Law Journal website on February 10, 2014. The original post can be accessed via the Archived Link button above

Noncanonical Quantization of Gravity. I. Foundations of Affine Quantum Gravity

The nature of the classical canonical phase-space variables for gravity suggests that the associated quantum field operators should obey affine commutation relations rather than canonical commutation relations. Prior to the introduction of constraints, a primary kinematical representation is derived in the form of a reproducing kernel and its associated reproducing kernel Hilbert space. Constraints are introduced following the projection operator method which involves no gauge fixing, no complicated moduli space, nor any auxiliary fields. The result, which is only qualitatively sketched in the present paper, involves another reproducing kernel with which inner products are defined for the physical Hilbert space and which is obtained through a reduction of the original reproducing kernel. Several of the steps involved in this general analysis are illustrated by means of analogous steps applied to one-dimensional quantum mechanical models. These toy models help in motivating and understanding the analysis in the case of gravity.Comment: minor changes, LaTeX, 37 pages, no figure

Universality of Tip Singularity Formation in Freezing Water Drops

A drop of water deposited on a cold plate freezes into an ice drop with a pointy tip. While this phenomenon clearly finds its origin in the expansion of water upon freezing, a quantitative description of the tip singularity has remained elusive. Here we demonstrate how the geometry of the freezing front, determined by heat transfer considerations, is crucial for the tip formation. We perform systematic measurements of the angles of the conical tip, and reveal the dynamics of the solidification front in a Hele-Shaw geometry. It is found that the cone angle is independent of substrate temperature and wetting angle, suggesting a universal, self-similar mechanism that does not depend on the rate of solidification. We propose a model for the freezing front and derive resulting tip angles analytically, in good agreement with observations.Comment: Letter format, 5 pages, 3 figures. Note: authors AGM and ORE contributed equally to the pape

Random walks in random Dirichlet environment are transient in dimension d≥3d\ge 3

We consider random walks in random Dirichlet environment (RWDE) which is a special type of random walks in random environment where the exit probabilities at each site are i.i.d. Dirichlet random variables. On $\Z^d$, RWDE are parameterized by a $2d$-uplet of positive reals. We prove that for all values of the parameters, RWDE are transient in dimension $d\ge 3$. We also prove that the Green function has some finite moments and we characterize the finite moments. Our result is more general and applies for example to finitely generated symmetric transient Cayley graphs. In terms of reinforced random walks it implies that directed edge reinforced random walks are transient for $d\ge 3$.Comment: New version published at PTRF with an analytic proof of lemma