Good approximate quantum LDPC codes from spacetime circuit Hamiltonians

We study approximate quantum low-density parity-check (QLDPC) codes, which are approximate quantum error-correcting codes specified as the ground space of a frustration-free local Hamiltonian, whose terms do not necessarily commute. Such codes generalize stabilizer QLDPC codes, which are exact quantum error-correcting codes with sparse, low-weight stabilizer generators (i.e. each stabilizer generator acts on a few qubits, and each qubit participates in a few stabilizer generators). Our investigation is motivated by an important question in Hamiltonian complexity and quantum coding theory: do stabilizer QLDPC codes with constant rate, linear distance, and constant-weight stabilizers exist? We show that obtaining such optimal scaling of parameters (modulo polylogarithmic corrections) is possible if we go beyond stabilizer codes: we prove the existence of a family of $[[N,k,d,\varepsilon]]$ approximate QLDPC codes that encode $k = \widetilde{\Omega}(N)$ logical qubits into $N$ physical qubits with distance $d = \widetilde{\Omega}(N)$ and approximation infidelity $\varepsilon = \mathcal{O}(1/\textrm{polylog}(N))$. The code space is stabilized by a set of 10-local noncommuting projectors, with each physical qubit only participating in $\mathcal{O}(\textrm{polylog} N)$ projectors. We prove the existence of an efficient encoding map, and we show that arbitrary Pauli errors can be locally detected by circuits of polylogarithmic depth. Finally, we show that the spectral gap of the code Hamiltonian is $\widetilde{\Omega}(N^{-3.09})$ by analyzing a spacetime circuit-to-Hamiltonian construction for a bitonic sorting network architecture that is spatially local in $\textrm{polylog}(N)$ dimensions.Comment: 51 pages, 13 figure

Consumption Growth and Agricultural Shocks in Rural Madagascar

The aim of this paper is to evaluate the effect of rainfall and agricultural shocks on consumption growth in Madagascar. We are also interested in the impact of local endowments in infrastructures and social services on consumption growth. To achieve this goal, a micro model of household consumption growth is estimated thanks to household panel data collected by the Reseau des Observatoires Ruraux (ROR) between 1999 and 2004. Additional data sources include the 2001 communes census organized by the Ilo program of Cornell University. Altogether these different data sources make an unusually rich data set, at least when considered with developing country standards. We use panel data fixed effect estimation technique to remove unobserved household and community level time invariant heterogeneity. We find that production shocks have a substantial impact on consumption growth and we find sign of persistence of rainfall shocks. Roads and education seems to improve household’s consumption growth and remotness decreases it.risks, growth, poverty, Food Security and Poverty,

UV Emission from Elliptical Galaxies Near and Far

The far-ultraviolet is the most rapidly evolving portion of the spectrum in both very young galaxies and very old galaxies. The ``UV upturn'' in the spectra of elliptical galaxies shortward of 2000 Angstroms offers a promising probe of the ages and chemical evolution of very old galaxies. In early-type non-active galaxies with the bluest 1550-V colors, the bulk of the emission arises from Extreme Horizontal Branch (EHB) stars, along their evolution from the zero-age HB to the white-dwarf cooling curve. The strength of the UV-upturn is governed by the fraction of stars that evolve through the EHB phase, which is in turn governed by age, metallicity, helium abundance, and other parameters such as stellar rotation and binarity that might influence the amount of mass loss on the RGB. Spectral constraints on the nature of the hot stellar population from Astro-2 are reviewed, and new imaging results from the HST Faint Object Camera are presented. Attempts to measure evolution through observations of high-redshift elliptical galaxies in the rest-frame UV are reviewed.Comment: 10 pages, Latex, 5 figures. Uses aipproc.sty and aipproc.cls. To appear in the conference proceedings of 'The UV Universe at Low and High Redshift: Probing the Progress of Galaxy Evolution,' eds. W. H. Waller, M. N. Fanelli, and A. C. Danks (New York: AIP). Postscript file with color figures available from http://icarus.stsci.edu/~ferguson/research/papers/uvuniverse_color.p

Far-UV Emission from Elliptical Galaxies at z=0.55

The restframe UV-to-optical flux ratio, characterizing the ``UV upturn'' phenomenon, is potentially the most sensitive tracer of age in elliptical galaxies; models predict that it may change by orders of magnitude over the course of a few Gyr. In order to trace the evolution of the UV upturn as a function of redshift, we have used the far-UV camera on the Space Telescope Imaging Spectrograph to image the galaxy cluster CL0016+16 at z=0.55. Our 25''x25'' field includes four bright elliptical galaxies, spectroscopically confirmed to be passively evolving cluster members. The weak UV emission from the galaxies in our image demonstrates that the UV upturn is weaker at a lookback time 5.6 Gyr earlier than our own, as compared to measurements of the UV upturn in cluster E and S0 galaxies at z=0 and z=0.375. These images are the first with sufficient depth to demonstrate the fading of the UV upturn expected at moderate redshifts. We discuss these observations and the implications for the formation history of galaxies.Comment: 4 pages, Latex. 2 figures. Uses corrected version of emulateapj.sty and apjfonts.sty (included). Accepted for publication in ApJ Letter

Acesso à educação de artes no ensino médio: Porque a participação dos alunos é tão importante quanto à disponibilidade do Curso

There is renewed interest in the role of arts education in the curriculum of U.S. public schools not only because of the intrinsic value of the arts and its believed impact on achievement, but because cultivating creativity is thought to promote innovation and fuel economic growth. Still, we know little about basic access to arts education. Using individual-level administrative data from The University of Texas at Dallas Education Research Center (UTD-ERC), we develop several distinct indices of access to identify high schools rich in the arts. We find that high schools offering an extensive number of courses in the arts do not necessarily enjoy high rates of student participation. Policymakers who examine access based only on course counts in the arts will identify predominately large, non-rural high schools as having arts-rich environments. Evaluating arts programs along a single dimension, as is common in federal reports and other studies, fails to provide an accurate representation of access to arts education. Any examination of access to arts education should jointly consider course availability and student engagement in the arts. Policymakers can follow our approach and develop similar indices to assess the current state of arts education in their states.Existe un renovado interés en el papel de la educación artística en el currículo de las escuelas públicas de Estados Unidos, no sólo por el valor intrínseco de las artes y su impacto en el rendimiento, sino porque el cultivo de la creatividad se cree promueve la innovación y el crecimiento económico. Sin embargo, sabemos muy poco sobre el acceso básico a la educación artística. Utilizando los datos administrativos a nivel individual del Centro de Investigación en Educación de la Universidad de Texas en Dallas (UTD-ERC), desarrollamos varios índices de acceso para identificar las escuelas secundarias con mayor acceso a las artes. Encontramos que las escuelas secundarias que ofrecen un gran número de cursos de artes no disfrutan necesariamente de altas tasas de participación de los estudiantes. Las autoridades que examinan acceso basado únicamente en número de cursos de arte identificarán las escuelas secundarias predominantemente grandes, en zonas no rurales, como poseedoras de ambientes ricos en arte. La evaluación de los programas de arte en una sola dimensión, como es común en los informes federales y otros estudios, no proporcionan una representación precisa del acceso a la educación artística. Cualquier examen de acceso a la educación artística debe considerar conjuntamente disponibilidad del curso y la participación del estudiante en las artes. Los políticos pueden seguir nuestro enfoque y desarrollar índices similares para evaluar el estado actual de la educación artística en sus estados.Há um interesse renovado no papel da educação de artes no currículo das escolas públicas dos Estados Unidos, não só por causa do valor intrínseco das artes e seu acreditável impacto no sucesso, mas porque cultivar a criatividade é considerado promover a inovação e servir como combustível no crescimento econômico. Ainda assim, nós sabemos pouco sobre o acesso básico à educação de artes. Usando dados administrativos a nível individual na Universidade de Texas no Centro de Pesquisa Educação Dallas (UTD-ERC), nós desenvolvemos vários índices distintos de acesso para identificar escolas de ensino médio ricas em artes. Nós achamos que escolas de ensino médio que oferecem uma extensa série de cursos em artes não necessariamente desfrutam de altos índices de participação dos alunos. Os legisladores, que examinam o acesso com base apenas na contagem de cursos de artes identificará predominantemente grandes escolas de ensino médio, não-rurais como tendo ambientes ricos em artes. Avaliação de programas de artes ao longo de uma única dimensão, como é comum em relatórios federais e outros estudos, não fornecem uma representação precisa do acesso à educação de artes. Qualquer exame de acesso à educação de artes deve considerar em conjunto a disponibilidade do curso e o envolvimento dos alunos nas artes. Os formuladores de políticas podem seguir nossa abordagem e desenvolver índices semelhantes para avaliar o estado atual da educação de artes em seus estados

Steady-state activation and modulation of the synaptic-type α1β2γ2L GABAA receptor by combinations of physiological and clinical ligands

The synaptic α1β2γ2 GAB

Color--Luminosity Relations for the Resolved Hot Stellar Populations in the Centers of M 31 and M 32

We present Faint Object Camera (FOC) ultraviolet images of the central 14x14'' of Messier 31 and Messier 32. The hot stellar population detected in the composite UV spectra of these nearby galaxies is partially resolved into individual stars, and their individual colors and apparent magnitudes are measured. We detect 433 stars in M 31 and 138 stars in M 32, down to detection limits of m_F275W = 25.5 mag and m_F175W = 24.5 mag. We investigate the luminosity functions of the sources, their spatial distribution, their color-magnitude diagrams, and their total integrated far-UV flux. Although M 32 has a weaker UV upturn than M 31, the luminosity functions and color-magnitude diagrams of M 31 and M 32 are surprisingly similar, and are inconsistent with a majority contribution from any of the following: PAGB stars more massive than 0.56 Msun, main sequence stars, or blue stragglers. Both the the luminosity functions and color-magnitude diagrams are consistent with a dominant population of stars that have evolved from the extreme horizontal branch (EHB) along tracks with masses between 0.47 and 0.53 Msun. These stars are well below the detection limits of our images while on the zero-age EHB, but become detectable while in the more luminous (but shorter) AGB-Manque' and post-early asymptotic giant branch (PEAGB) phases. The FOC observations require that only a only a very small fraction of the main sequence population (2% in M 31 and 0.5% in M 32) in these two galaxies evolve though the EHB and post-EHB phases, with the remainder evolving through bright PAGB evolution that is so rapid that few if any stars are expected in the small field of view covered by the FOC.Comment: 35 pages, Latex. 19 figures. To appear in ApJ. Uses emulateapj.sty and apjfonts.sty (included). Color plates distributed seperatedly: fig1.jpg and fig2.jp