Automatically Generating Solutions for Sokoban Maps

Generating solutions to Sokoban levels is an NP-hard problem that is difficult for even modern day computers to solve due to its complexity. This project explores the creation of a Sokoban solver by eliminating as many potential moves as possible to greatly limit the overall search space. This reduction is achieved through abstracting out moves that don’t involve a box push and also through removing any deadlocked states where the problem is in a state that makes it unsolvable. The result is a Sokoban solver that shows substantial improvement over a standard exhaustive approach

Ariel - Volume 11 Number 1

Executive Editors Ellen Feldman Leonardo S. Nasca, Jr. Business Managers Barbara L. Davies Martin B. Getzow News Editor Aaron D. Bleznak Features Editor Dave Van Wagoner CAHS Editor Joan M. Greco Editorial Page Editor Samuel Markind Photography Editor Leonardo S. Nasca, Jr. Sports Editor Paul F. Mansfiel

NGC 5846-UDG1: A Galaxy Formed Mostly by Star Formation in Massive, Extremely Dense Clumps of Gas

It has been shown that ultra-diffuse galaxies (UDGs) have higher specific frequencies of globular clusters, on average, than other dwarf galaxies with similar luminosities. The UDG NGC 5846-UDG1 is among the most extreme examples of globular cluster-rich galaxies found so far. Here we present new Hubble Space Telescope observations and analysis of this galaxy and its globular cluster system. We find that NGC 5846-UDG1 hosts 54 ± 9 globular clusters, three to four times more than any previously known galaxy with a similar luminosity and higher than reported in previous studies. With a galaxy luminosity of L V,gal ≈ 6 × 107 L ⊙ (M ⋆ ≈ 1.2 × 108 M ⊙) and a total globular cluster luminosity of L V,GCs ≈ 7.6 × 106 L ⊙, we find that the clusters currently comprise ∼13% of the total light. Taking into account the effects of mass loss from clusters during their formation and throughout their lifetime, we infer that most of the stars in the galaxy likely formed in globular clusters, and very little to no normal low-density star formation occurred. This result implies that the most extreme conditions during early galaxy formation promoted star formation in massive and dense clumps, in contrast to the dispersed star formation observed in galaxies today

LSST Cadence Optimization White Paper in Support of Observations of Unresolved Tidal Stellar Streams in Galaxies beyond the Local Group

Deep observations of faint surface brightness stellar tidal streams in external galaxies with LSST are addressed in this White Paper contribution. We propose using the Wide--Fast--Deep survey that contains several nearby galaxies (at distances where the stars themselves are not resolved, i.e., beyond 20 Mpc). In the context of hierarchical galaxy formation, it is necessary to understand the prevalence and properties of tidal substructure around external galaxies based on integrated (i.e., unresolved) diffuse light. This requires collecting observations on much larger samples of galaxies than the Milky Way and M31. We will compare the observed structures to the predictions of cosmological models of galactic halo formation that inform us about the number and properties of streams around Milky Way-like galaxies. The insight gained from these comparisons will allow us to infer the properties of stream progenitors (masses, dynamics, metallicities, stellar populations). The changes in the host galaxies caused by the interactions with the dissolving companion galaxies will be another focus of our studies. We conclude by discussing synergies with WFIRST and Euclid, and also provide concrete suggestions for how the effects of scattered light could be minimized in LSST images to optimize the search for low surface brightness features, such as faint unresolved stellar tidal streams.Comment: 13 pages, 2 figures, submitted to Call for White Papers on LSST Cadence Optimizatio

Monetary and fiscal policies for a finite planet

Current macroeconomic policy promotes continuous economic growth. Unemployment, poverty and debt are associated with insufficient growth. Economic activity depends upon the transformation of natural materials, ultimately returning to the environment as waste. Current levels of economic throughput exceed the planet\u27s carrying capacity. As a result of poorly constructed economic institutions, society faces the unacceptable choice between ecological catastrophe and human misery. A transition to a steady-state economy is required, characterized by a rate of throughput compatible with planetary boundaries. This paper contributes to the development of a steady-state economy by addressing US monetary and fiscal policies. A steady-state monetary policy would support counter-cyclical, debt-free vertical money creation through the public sector, in ways that contribute to sustainable well-being. The implication for a steady-state fiscal policy is that any lending or spending requires a careful balance of recovery of money, not as a means of revenue, but as an economic imperative to meet monetary policy goals. A steady-state fiscal policy would prioritize targeted public goods investments, taxation of ecological bads and economic rent and implementation of progressive tax structures. Institutional innovations are considered, including common asset trusts, to regulate throughput, and a public monetary trust, to strictly regulate money supply

WISEA J041451.67–585456.7 and WISEA J181006.18–101000.5: The First Extreme T-type Subdwarfs?

We present the discoveries of WISEA J041451.67−585456.7 and WISEA J181006.18−101000.5, two low-temperature (1200–1400 K), high proper motion T-type subdwarfs. Both objects were discovered via their high proper motion (>0".5 yr⁻¹); WISEA J181006.18−101000.5 as part of the NEOWISE proper motion survey and WISEA J041451.67−585456.7 as part of the citizen science project Backyard Worlds; Planet 9. We have confirmed both as brown dwarfs with follow-up near-infrared spectroscopy. Their spectra and near-infrared colors are unique among known brown dwarfs, with some colors consistent with L-type brown dwarfs and other colors resembling those of the latest-type T dwarfs. While no forward model consistently reproduces the features seen in their near-infrared spectra, the closest matches suggest very low metallicities ([Fe/H] ⩽ −1), making these objects likely the first examples of extreme subdwarfs of the T spectral class (esdT). WISEA J041451.67−585456.7 and WISEA J181006.18−101000.5 are found to be part of a small population of objects that occupy the "substellar transition zone," and have the lowest masses and effective temperatures of all objects in this group