15,044 research outputs found
Natural Density of Rectangular Unimodular Integer Matrices
In this paper, we compute the natural density of the set of k x n integer
matrices that can be extended to an invertible n x n matrix over the integers.
As a corollary, we find the density of rectangular matrices with Hermite normal
form [O Id]. Connections with Cesaro's Theorem on the density of coprime
integers and Quillen-Suslin's Theorem are also presented.Comment: 8 page
Public Key Cryptography based on Semigroup Actions
A generalization of the original Diffie-Hellman key exchange in
found a new depth when Miller and Koblitz suggested that such a protocol could
be used with the group over an elliptic curve. In this paper, we propose a
further vast generalization where abelian semigroups act on finite sets. We
define a Diffie-Hellman key exchange in this setting and we illustrate how to
build interesting semigroup actions using finite (simple) semirings. The
practicality of the proposed extensions rely on the orbit sizes of the
semigroup actions and at this point it is an open question how to compute the
sizes of these orbits in general and also if there exists a square root attack
in general. In Section 2 a concrete practical semigroup action built from
simple semirings is presented. It will require further research to analyse this
system.Comment: 20 pages. To appear in Advances in Mathematics of Communication
Weight-Preserving Simulated Tempering
Simulated tempering is popular method of allowing MCMC algorithms to move
between modes of a multimodal target density {\pi}. One problem with simulated
tempering for multimodal targets is that the weights of the various modes
change for different inverse-temperature values, sometimes dramatically so. In
this paper, we provide a fix to overcome this problem, by adjusting the mode
weights to be preserved (i.e., constant) over different inverse-temperature
settings. We then apply simulated tempering algorithms to multimodal targets
using our mode weight correction. We present simulations in which our
weight-preserving algorithm mixes between modes much more successfully than
traditional tempering algorithms. We also prove a diffusion limit for an
version of our algorithm, which shows that under appropriate assumptions, our
algorithm mixes in time O(d [log d]^2)
Biomedical and Human Factors Requirements for a Manned Earth Orbiting Station
This report is the result of a study conducted by Republic Aviation Corporation in conjunction with Spacelabs, Inc.,in a team effort in which Republic Aviation Corporation was prime contractor. In order to determine the realistic engineering design requirements associated with the medical and human factors problems of a manned space station, an interdisciplinary team of personnel from the Research and Space Divisions was organized. This team included engineers, physicians, physiologists, psychologists, and physicists. Recognizing that the value of the study is dependent upon medical judgments as well as more quantifiable factors (such as design parameters) a group of highly qualified medical consultants participated in working sessions to determine which medical measurements are required to meet the objectives of the study. In addition, various Life Sciences personnel from NASA (Headquarters, Langley, MSC) participated in monthly review sessions. The organization, team members, consultants, and some of the part-time contributors are shown in Figure 1. This final report embodies contributions from all of these participants
Separate Identity, Tax Treaty Interpretation, and Unilateral Treaty Override: An Analysis of Revenue Rulings 84-152 and 84-153
Painting Native America in Public: American Indian Artists and the New Deal
The New Deal represents a critical period in the development of American Indian art. Shifts in policy created opportunities for American Indians to study art, and New Deal commissions for murals in post offices and other public spaces enabled artists to develop skills, establish their reputations, and make a living. American Indian artists also faced challenges in the form of dominant expectations for Native art and paternalism from officials and administrators. The benefits of New Deal commissions and the struggles with their limitations nonetheless formed a foundation for subsequent generations of Native artists who claimed more control over their art
Representing Native Peoples: Native Narratives of Indigenous History and Culture
Together, the articles in this special issue of the American Indian Culture and Research Journal offer a discussion of how Indigenous peoples have represented themselves and their communities in different periods and contexts, as well as through various media. Ranging across anthropology, art history, cartography, film studies, history, and literature, the authors examine how Native people negotiate with prominent images and ideas that represented Indians in the dominant culture and society in the United States and the Americas. These essays go beyond the problems of cultural appropriation by non-Indians to probe the myriad ways Native Americans and Indigenous people have challenged, reinforced, shifted, and overturned those representations
- …