2,040 research outputs found
Adam Smith and Colonialism
In the context of debates about liberalism and colonialism, the arguments of Adam Smith have been taken as illustrative of an important line of anti-colonial liberal thought. The reading of Smith presented here challenges this interpretation. It argues that Smith’s opposition to colonial rule derived largely from its impact on the metropole, rather than on its impact on the conquered and colonised; that Smith recognised colonialism had brought ‘improvement’ in conquered territories and that Smith struggled to balance recognition of moral diversity with a universal moral framework and a commitment to a particular interpretation of progress through history. These arguments have a wider significance as they point towards some of the issues at stake in liberal anti-colonial arguments more generally
Forward Flux Sampling for rare event simulations
Rare events are ubiquitous in many different fields, yet they are notoriously
difficult to simulate because few, if any, events are observed in a conventiona
l simulation run. Over the past several decades, specialised simulation methods
have been developed to overcome this problem. We review one recently-developed
class of such methods, known as Forward Flux Sampling. Forward Flux Sampling
uses a series of interfaces between the initial and final states to calculate
rate constants and generate transition paths, for rare events in equilibrium or
nonequilibrium systems with stochastic dynamics. This review draws together a
number of recent advances, summarizes several applications of the method and
highlights challenges that remain to be overcome.Comment: minor typos in the manuscript. J.Phys.:Condensed Matter (accepted for
publication
Perceptual Context in Cognitive Hierarchies
Cognition does not only depend on bottom-up sensor feature abstraction, but
also relies on contextual information being passed top-down. Context is higher
level information that helps to predict belief states at lower levels. The main
contribution of this paper is to provide a formalisation of perceptual context
and its integration into a new process model for cognitive hierarchies. Several
simple instantiations of a cognitive hierarchy are used to illustrate the role
of context. Notably, we demonstrate the use context in a novel approach to
visually track the pose of rigid objects with just a 2D camera
Information theoretic approach to interactive learning
The principles of statistical mechanics and information theory play an
important role in learning and have inspired both theory and the design of
numerous machine learning algorithms. The new aspect in this paper is a focus
on integrating feedback from the learner. A quantitative approach to
interactive learning and adaptive behavior is proposed, integrating model- and
decision-making into one theoretical framework. This paper follows simple
principles by requiring that the observer's world model and action policy
should result in maximal predictive power at minimal complexity. Classes of
optimal action policies and of optimal models are derived from an objective
function that reflects this trade-off between prediction and complexity. The
resulting optimal models then summarize, at different levels of abstraction,
the process's causal organization in the presence of the learner's actions. A
fundamental consequence of the proposed principle is that the learner's optimal
action policies balance exploration and control as an emerging property.
Interestingly, the explorative component is present in the absence of policy
randomness, i.e. in the optimal deterministic behavior. This is a direct result
of requiring maximal predictive power in the presence of feedback.Comment: 6 page
Supersymmetric QCD: Exact Results and Strong Coupling
We revisit two longstanding puzzles in supersymmetric gauge theories. The
first concerns the question of the holomorphy of the coupling, and related to
this the possible definition of an exact (NSVZ) beta function. The second
concerns instantons in pure gluodynamics, which appear to give sensible, exact
results for certain correlation functions, which nonetheless differ from those
obtained using systematic weak coupling expansions. For the first question, we
extend an earlier proposal of Arkani-Hamed and Murayama, showing that if their
regulated action is written suitably, the holomorphy of the couplings is
manifest, and it is easy to determine the renormalization scheme for which the
NSVZ formula holds. This scheme, however, is seen to be one of an infinite
class of schemes, each leading to an exact beta function; the NSVZ scheme,
while simple, is not selected by any compelling physical consideration. For the
second question, we explain why the instanton computation in the pure
supersymmetric gauge theory is not reliable, even at short distances. The
semiclassical expansion about the instanton is purely formal; if infrared
divergences appear, they spoil arguments based on holomorphy. We demonstrate
that infrared divergences do not occur in the perturbation expansion about the
instanton, but explain that there is no reason to think this captures all
contributions from the sector with unit topological charge. That one expects
additional contributions is illustrated by dilute gas corrections. These are
infrared divergent, and so difficult to define, but if non-zero give order one,
holomorphic, corrections to the leading result. Exploiting an earlier analysis
of Davies et al, we demonstrate that in the theory compactified on a circle of
radius beta, due to infrared effects, finite contributions indeed arise which
are not visible in the formal limit that beta goes to infinity.Comment: 28 pages, two references added, one typo correcte
Boundary Conditions on Internal Three-Body Wave Functions
For a three-body system, a quantum wave function with definite
and quantum numbers may be expressed in terms of an internal wave
function which is a function of three internal coordinates. This
article provides necessary and sufficient constraints on to
ensure that the external wave function is analytic. These
constraints effectively amount to boundary conditions on and its
derivatives at the boundary of the internal space. Such conditions find
similarities in the (planar) two-body problem where the wave function (to
lowest order) has the form at the origin. We expect the boundary
conditions to prove useful for constructing singularity free three-body basis
sets for the case of nonvanishing angular momentum.Comment: 41 pages, submitted to Phys. Rev.
Effective interaction between helical bio-molecules
The effective interaction between two parallel strands of helical
bio-molecules, such as deoxyribose nucleic acids (DNA), is calculated using
computer simulations of the "primitive" model of electrolytes. In particular we
study a simple model for B-DNA incorporating explicitly its charge pattern as a
double-helix structure. The effective force and the effective torque exerted
onto the molecules depend on the central distance and on the relative
orientation. The contributions of nonlinear screening by monovalent counterions
to these forces and torques are analyzed and calculated for different salt
concentrations. As a result, we find that the sign of the force depends
sensitively on the relative orientation. For intermolecular distances smaller
than it can be both attractive and repulsive. Furthermore we report a
nonmonotonic behaviour of the effective force for increasing salt
concentration. Both features cannot be described within linear screening
theories. For large distances, on the other hand, the results agree with linear
screening theories provided the charge of the bio-molecules is suitably
renormalized.Comment: 18 pages, 18 figures included in text, 100 bibliog
1950: Abilene Christian College Bible Lectures - Full Text
Introduction
We offer with interest and pleasure another volume of a great series of discourses delivered at Abilene Christian College. The following were given in February, 1950. The first of these Lectureships was held in the year 1919, and was published by the Firm Foundation Publishing House in book form. With little exception they have appeared each year since that time. The printing was done by others a few times. Those who are fortunate enough to have a complete set of these fine gospel sermons are possessed of a treasure in religious literature. Only a few of the later years can now be supplied. The rest are numbered among the “rare books” and we frequently have calls for them, but of course cannot supply them. Any reader having a copy for sale is requested to write the office of the Firm Foundation at Austin, Texas. The “Lectureship” of Abilene Christian College has become a great annual affair to the churches of Christ; thousands are in attendance, many of them coming from Canada and other countries besides all over the United States. This annual “mass meeting” must not be understood to be a “Convention” of the churches of Christ. We have no such conventions and do not endorse them. The Lectureship is simply a feature in the work of Abilene Christian College, a series of gospel sermons to which friends and patrons of the school and others are invited. It is our hope that the contents of this book may enrich the life, and strengthen the faith of the reader.
G. H. F. SHOWALTER
Austin, Texas August 20, 195
The Value of Information for Populations in Varying Environments
The notion of information pervades informal descriptions of biological
systems, but formal treatments face the problem of defining a quantitative
measure of information rooted in a concept of fitness, which is itself an
elusive notion. Here, we present a model of population dynamics where this
problem is amenable to a mathematical analysis. In the limit where any
information about future environmental variations is common to the members of
the population, our model is equivalent to known models of financial
investment. In this case, the population can be interpreted as a portfolio of
financial assets and previous analyses have shown that a key quantity of
Shannon's communication theory, the mutual information, sets a fundamental
limit on the value of information. We show that this bound can be violated when
accounting for features that are irrelevant in finance but inherent to
biological systems, such as the stochasticity present at the individual level.
This leads us to generalize the measures of uncertainty and information usually
encountered in information theory
Letters between Fred J. Pack and William Kerr\u27s secretary
Letters concerning a position at the Utah Agricultural College
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