17,073 research outputs found
MS-167: Hiram Parker Jr. Letters
There are 52 letters total in the collection spanning from 1862-1874. The bulk of the letters are written by Hiram most of which are to his father, mother Mary Sparks. However, there are a couple to another member of the Sparks family and a few other friends. Six are letters written to Hiram from his friends and the collection also includes 12 handwritten and printed reports on the construction of the gunboat Tacony. Hiram’s letters are very detailed (some of his letters are over a dozen pages), and he wrote to people very often even adding on to some letters after he originally finished writing them. Many of the letters still have their original envelopes with them.
Special Collections and College Archives Finding Aids are discovery tools used to describe and provide access to our holdings. Finding aids include historical and biographical information about each collection in addition to inventories of their content. More information about our collections can be found on our website http://www.gettysburg.edu/special_collections/collections/.https://cupola.gettysburg.edu/findingaidsall/1140/thumbnail.jp
MS-129: Burlew Letters
This collection consists of letter written between Aaron E. Burlew, John W. Burlew, and Carrie Burlew, all siblings from Atkinsons Mills, Pennsylvania, during the Civil War.https://cupola.gettysburg.edu/findingaidsall/1149/thumbnail.jp
Detecting Unresolved Binaries in TESS Data with Speckle Imaging
The Transiting Exoplanet Survey Satellite (TESS) is conducting a two-year
wide-field survey searching for transiting exoplanets around nearby bright
stars that will be ideal for follow-up characterization. To facilitate studies
of planet compositions and atmospheric properties, accurate and precise
planetary radii need to be derived from the transit light curves. Since 40 -
50% of exoplanet host stars are in multiple star systems, however, the observed
transit depth may be diluted by the flux of a companion star, causing the
radius of the planet to be underestimated. High angular resolution imaging can
detect companion stars that are not resolved in the TESS Input Catalog, or by
seeing-limited photometry, to validate exoplanet candidates and derive accurate
planetary radii. We examine the population of stellar companions that will be
detectable around TESS planet candidate host stars, and those that will remain
undetected, by applying the detection limits of speckle imaging to the
simulated host star populations of Sullivan et al. (2015) and Barclay et al.
(2018). By detecting companions with contrasts of delta m < 7 - 9 and
separations of ~0.02 - 1.2'', speckle imaging can detect companion stars as
faint as early M stars around A - F stars and stars as faint as mid-M around G
- M stars, as well as up to 99% of the expected binary star distribution for
systems located within a few hundred parsecs.Comment: Accepted for publication in The Astronomical Journal; 16 pages, 8
figures, 2 table
Simple groups separated by finiteness properties
We show that for every positive integer there exists a simple group that
is of type but not of type . For
these groups are the first known examples of this kind. They also provide
infinitely many quasi-isometry classes of finitely presented simple groups. The
only previously known infinite family of such classes, due to Caprace--R\'emy,
consists of non-affine Kac--Moody groups over finite fields. Our examples arise
from R\"over--Nekrashevych groups, and contain free abelian groups of infinite
rank.Comment: 25 pages. v2: incorporated comments v3: final version, to appear,
Invent. Mat
Exact Excited States of Non-Integrable Models
We discuss a method of numerically identifying exact energy eigenstates for a
finite system, whose form can then be obtained analytically. We demonstrate our
method by identifying and deriving exact analytic expressions for several
excited states, including an infinite tower, of the one dimensional spin-1 AKLT
model, a celebrated non-integrable model. The states thus obtained for the AKLT
model can be interpreted as one-to-an extensive number of quasiparticles on the
ground state or on the highest excited state when written in terms of dimers.
Included in these exact states is a tower of states spanning energies from the
ground state to the highest excited state. To our knowledge, this is the first
time that exact analytic expressions for a tower of excited states have been
found in non-integrable models. Some of the states of the tower appear to be in
the bulk of the energy spectrum, allowing us to make conjectures on the strong
Eigenstate Thermalization Hypothesis (ETH). We also generalize these exact
states including the tower of states to the generalized integer spin AKLT
models. Furthermore, we establish a correspondence between some of our states
and those of the Majumdar-Ghosh model, yet another non-integrable model, and
extend our construction to the generalized integer spin AKLT models.Comment: 32 pages, 27 figures v2: References adde
Entanglement analysis of isotropic spin-1 chains
We investigate entanglement spectra of the SO(3) bilinear-biquadratic spin-1
chain, a model with phases exhibiting spontaneous symmetry breaking (both
translation and spin rotation), points of enlarged symmetry, and a
symmetry-protected topological phase (the Haldane phase). Our analysis reveals
how these hallmark features are manifested in the entanglement spectra, and
highlights the versatility of entanglement spectra as a tool to study
one-dimensional quantum systems via small finite size realisations.Comment: 21 pages, 13 figure
The Climate Gap: Inequalities in How Climate Change Hurts Americans & How to Close the Gap
By now, virtually all Americans concur that climate change is real, and could pose devastating consequences for our nation and our children. Equally real is the "Climate Gap" -- the sometimes hidden and often-unequal impact climate change will have on people of color and the poor in the United States. This report helps to document the Climate Gap, connecting the dots between research on heat waves, air quality, and other challenges associated with climate change. But we do more than point out an urgent problem; we also explore how we might best combine efforts to both solve climate change and close the Climate Gap -- including an appendix focused on California's global warming policy and a special accompanying analysis of the federal-level American Clean Energy Security Act
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