A First Amendment for Second Life: What Virtual Worlds Mean for the Law of Video Games

In the first decade of the twenty-first century, video games have finally taken their place alongside movies, comic books, and drawings as a form of protected First Amendment speech. Since the Seventh Circuit\u27s 2001 decision in American Amusement Machine Association v. Kendrick, court after court has struck down ordinances and statutes aimed at restricting violent video games--on the grounds that such violate game designers\u27 and players\u27 First Amendment speech rights. This series of rulings marks a stark change from courts\u27 previous stance on video games, which consigned them to the same realm of unprotected non-speech conduct as games like tennis, chess, or checkers. Video games were able to escape from this unprotected realm--and become First Amendment expression--largely because advances in computer graphics and design made them more and more like interactive movies and television shows, and less and less like digitized board games and pinball machines. But instead of simply forging ahead in this jurisprudential evolution, as video games evolve from personal forms of recreation to virtual worlds, this Article suggests that virtual worlds should make us rethink the First Amendment theory that got us to this point. This is because, while video games may have become First Amendment speech by becoming intricate movie-like stories, many virtual worlds are decidedly not scripted stories. They are rather stages for a multitude of expressive activity, some of which is an electronic analogue of the chess-playing, tennis-playing, car racing, or aimless lounging and wandering, that the courts excluded from the realm of First Amendment speech in an earlier era. This Article argues that this exclusion was a mistake. Virtual worlds are realms of First Amendment expression not because of the stories and role play they make possible, but rather because they provide a setting for giving form to imagination in sounds and imagery, a setting that can be walled off from the business of civil government and thus reserved for more unconstrained exercises of individual freedom. Stories and messages are an optional part of this setting and are not a necessary ingredient of First Amendment speech. This is not to say that government has no role to play in regulating virtual worlds: where individuals bring harm-threatening activity into virtual worlds involving acts that abuse others\u27 money or reputation, for example, government might have to regulate such worlds. But such regulation must take place alongside of, and not simply displace, the First Amendment\u27s application to virtual worlds

Giant Molecular Clouds in the Early-type Galaxy NGC 4526

D. Utomo, et al., “Giant Molecular Clouds in the Early-Type Galaxy NGC 4526”, The Astrophysical Journal, Vol. 803(1), April 2015. © 2015. The American Astronomical Society. All rights reserved.We present a high spatial resolution (≈20 pc) of 12CO(2 −1) observations of the lenticular galaxy NGC 4526. We identify 103 resolved giant molecular clouds (GMCs) and measure their properties: size R, velocity dispersion σv, and luminosity L. This is the first GMC catalog of an early-type galaxy. We find that the GMC population in NGC 4526 is gravitationally bound, with a virial parameter α ∼ 1. The mass distribution, dN/dM ∝ M−2.39 ± 0.03, is steeper than that for GMCs in the inner Milky Way, but comparable to that found in some late-type galaxies. We find no size–line width correlation for the NGC 4526 clouds, in contradiction to the expectation from Larson’s relation. In general, the GMCs in NGC 4526 are more luminous, denser, and have a higher velocity dispersion than equal-size GMCs in the Milky Way and other galaxies in the Local Group. These may be due to higher interstellar radiation field than in the Milky Way disk and weaker external pressure than in the Galactic center. In addition, a kinematic measurement of cloud rotation shows that the rotation is driven by the galactic shear. For the vast majority of the clouds, the rotational energy is less than the turbulent and gravitational energy, while the four innermost clouds are unbound and will likely be torn apart by the strong shear at the galactic center. We combine our data with the archival data of other galaxies to show that the surface density Σ of GMCs is not approximately constant, as previously believed, but varies by ∼3 orders of magnitude. We also show that the size and velocity dispersion of the GMC population across galaxies are related to the surface density, as expected from the gravitational and pressure equilibrium, i.e., σv R−1/2 ∝ Σ1/2.Peer reviewe

Dynamically Driven Evolution of the Interstellar Medium in M51

We report the highest-fidelity observations of the spiral galaxy M51 in CO emission, revealing the evolution of giant molecular clouds (GMCs) vis-a-vis the large-scale galactic structure and dynamics. The most massive GMCs (so-called GMAs) are first assembled and then broken up as the gas flow through the spiral arms. The GMAs and their H2 molecules are not fully dissociated into atomic gas as predicted in stellar feedback scenarios, but are fragmented into smaller GMCs upon leaving the spiral arms. The remnants of GMAs are detected as the chains of GMCs that emerge from the spiral arms into interarm regions. The kinematic shear within the spiral arms is sufficient to unbind the GMAs against self-gravity. We conclude that the evolution of GMCs is driven by large-scale galactic dynamics --their coagulation into GMAs is due to spiral arm streaming motions upon entering the arms, followed by fragmentation due to shear as they leave the arms on the downstream side. In M51, the majority of the gas remains molecular from arm entry through the inter-arm region and into the next spiral arm passage.Comment: 6 pages, including 3 figures. Accepted, ApJ

High-Redshift Galaxy Outflows and the Formation of Dwarf Galaxies

We examine the effects of galaxy outflows on the formation of dwarf galaxies in numerical simulations of the high-redshift Universe. Using a Smoothed Particle Hydrodynamic code, we conduct two detailed simulations of a (5.2 Mpc/h)^3 comoving volume of the Universe. In both simulations we implement simple, well-motivated models of galaxy identification and star formation, while our second simulation also includes a simple ``blow-out'' model of galaxy outflows in which supernova driven winds from newly formed disk galaxies punch-out and shock the intergalactic medium while leaving the host galaxies intact. A direct comparison between these simulations suggests that there are two major mechanisms by which outflows affect dwarf formation. Firstly, the formation of an outflow slows down the further accretion of gas onto a galaxy, causing an overall decrease of approximately 50% in the total gas mass accreted by the objects in our simulations. Additionally, our simulations uncover a significant population of approximately 10^9 solar mass objects whose formation is suppressed by the mechanism of ``baryonic stripping,'' in which outflows from early galaxies strip the gas out of nearby overdense regions that would have otherwise later formed into dwarf galaxies. This mechanism may be important in explaining the observed discrepancy between the number of dwarf galaxies predicted and observed in the local group and provide a natural explanation for the formation of empty halos which may be required by the existence of the extremely gas-poor extra-galactic High-Velocity Clouds.Comment: 15 pages, 9 figures, accepted to the Astrophysical Journa

A systematic variation of the stellar initial mass function in early-type galaxies

Much of our knowledge of galaxies comes from analysing the radiation emitted by their stars. It depends on the stellar initial mass function (IMF) describing the distribution of stellar masses when the population formed. Consequently knowledge of the IMF is critical to virtually every aspect of galaxy evolution. More than half a century after the first IMF determination, no consensus has emerged on whether it is universal in different galaxies. Previous studies indicated that the IMF and the dark matter fraction in galaxy centres cannot be both universal, but they could not break the degeneracy between the two effects. Only recently indications were found that massive elliptical galaxies may not have the same IMF as our Milky Way. Here we report unambiguous evidence for a strong systematic variation of the IMF in early-type galaxies as a function of their stellar mass-to-light ratio, producing differences up to a factor of three in mass. This was inferred from detailed dynamical models of the two-dimensional stellar kinematics for the large Atlas3D representative sample of nearby early-type galaxies spanning two orders of magnitude in stellar mass. Our finding indicates that the IMF depends intimately on a galaxy's formation history.Comment: 4 pages, 2 figures, LaTeX. Accepted for publication as a Nature Letter. More information about our Atlas3D project is available at http://purl.org/atlas3

Galactic Halo Models and Particle Dark-Matter Detection

Rates for detection of weakly-interacting massive-particle (WIMP) dark matter are usually carried out assuming the Milky Way halo is an isothermal sphere. However, it is possible that our halo is not precisely spherical; it may have some bulk rotation; and the radial profile may differ from that of an isothermal sphere. In this paper, we calculate detection rates in observationally consistent alternative halo models that produce the same halo contributions to the local and asymptotic rotation speeds to investigate the effects of theoretical uncertainty of the WIMP spatial and velocity distribution. We use self-consistent models to take into account the effects of various mass distributions on the local velocity distribution. The local halo density may be increased up to a factor of 2 by flattening or by an alternative radial profile (which may also decrease the density slightly). However, changes in the WIMP velocity distribution in these models produce only negligible changes in the WIMP detection rate. Reasonable bulk rotations lead to only an $O(10$ effect on event rates. We also show how the nuclear recoil spectrum in a direct-detection experiment could provide information on the shape and rotation of the halo.Comment: 11 pages, LaTe

Metallicity Evolution of Damped Lyman-alpha Systems out to z~5

We present chemical abundance measurements for 47 damped Lyman-alpha systems (DLAs), 30 at z>4, observed with the Echellette Spectrograph and Imager and the High Resolution Echelle Spectrometer on the Keck telescopes. HI column densities of the DLAs are measured with Voigt profile fits to the Lyman-alpha profiles, and we find an increased number of false DLA identifications with SDSS at z>4 due to the increased density of the Lyman-alpha forest. Ionic column densities are determined using the apparent optical depth method, and we combine our new metallicity measurements with 195 from previous surveys to determine the evolution of the cosmic metallicity of neutral gas. We find the metallicity of DLAs decreases with increasing redshift, improving the significance of the trend and extending it to higher redshifts, with a linear fit of -0.22+-0.03 dex per unit redshift from z=0.09-5.06. The metallicity 'floor' of ~1/600 solar continues out to z~5, despite our sensitivity for finding DLAs with much lower metallicities. However, this floor is not statistically different from a steep tail to the distribution. We also find that the intrinsic scatter of metallicity among DLAs of ~0.5 dex continues out to z~5. In addition, the metallicity distribution and the alpha/Fe ratios of z>2 DLAs are consistent with being drawn from the same parent population with those of halo stars. It is therefore possible that the halo stars in the Milky Way formed out of gas that commonly exhibits DLA absorption at z>2.Comment: Accepted for publication in the Astrophysical Journal. 24 pages, 17 figure

GABA Expression and Regulation by Sensory Experience in the Developing Visual System

The developing retinotectal system of the Xenopus laevis tadpole is a model of choice for studying visual experience-dependent circuit maturation in the intact animal. The neurotransmitter gamma-aminobutyric acid (GABA) has been shown to play a critical role in the formation of sensory circuits in this preparation, however a comprehensive neuroanatomical study of GABAergic cell distribution in the developing tadpole has not been conducted. We report a detailed description of the spatial expression of GABA immunoreactivity in the Xenopus laevis tadpole brain at two key developmental stages: stage 40/42 around the onset of retinotectal innervation and stage 47 when the retinotectal circuit supports visually-guided behavior. During this period, GABAergic neurons within specific brain structures appeared to redistribute from clusters of neuronal somata to a sparser, more uniform distribution. Furthermore, we found that GABA levels were regulated by recent sensory experience. Both ELISA measurements of GABA concentration and quantitative analysis of GABA immunoreactivity in tissue sections from the optic tectum show that GABA increased in response to a 4 hr period of enhanced visual stimulation in stage 47 tadpoles. These observations reveal a remarkable degree of adaptability of GABAergic neurons in the developing brain, consistent with their key contributions to circuit development and function