9,355 research outputs found
Neutron matter from chiral two- and three-nucleon calculations up to NLO
Neutron matter is an ideal laboratory for nuclear interactions derived from
chiral effective field theory since all contributions are predicted up to
next-to-next-to-next-to-leading order (NLO) in the chiral expansion. By
making use of recent advances in the partial-wave decomposition of three-
nucleon (3N) forces, we include for the first time NLO 3N interactions in
many-body perturbation theory (MBPT) up to third order and in self-consistent
Green's function theory (SCGF). Using these two complementary many-body
frameworks we provide improved predictions for the equation of state of neutron
matter at zero temperature and also analyze systematically the many-body
convergence for different chiral EFT interactions. Furthermore, we present an
extension of the normal-ordering framework to finite temperatures. These
developments open the way to improved calculations of neutron-rich matter
including estimates of theoretical uncertainties for astrophysical
applications.Comment: minor changes, published versio
Choreographies in Practice
Choreographic Programming is a development methodology for concurrent
software that guarantees correctness by construction. The key to this paradigm
is to disallow mismatched I/O operations in programs, called choreographies,
and then mechanically synthesise distributed implementations in terms of
standard process models via a mechanism known as EndPoint Projection (EPP).
Despite the promise of choreographic programming, there is still a lack of
practical evaluations that illustrate the applicability of choreographies to
concrete computational problems with standard concurrent solutions. In this
work, we explore the potential of choreographies by using Procedural
Choreographies (PC), a model that we recently proposed, to write distributed
algorithms for sorting (Quicksort), solving linear equations (Gaussian
elimination), and computing Fast Fourier Transform. We discuss the lessons
learned from this experiment, giving possible directions for the usage and
future improvements of choreography languages
Uncertainties in constraining low-energy constants from H decay
We discuss the uncertainties in constraining low-energy constants of chiral
effective field theory from H decay. The half-life is very
precisely known, so that the Gamow-Teller matrix element has been used to fit
the coupling of the axial-vector current to a short-range two-nucleon
pair. Because the same coupling also describes the leading one-pion-exchange
three-nucleon force, this in principle provides a very constraining fit,
uncorrelated with the H binding energy fit used to constrain another
low-energy coupling in three-nucleon forces. However, so far such H
half-life fits have only been performed at a fixed cutoff value. We show that
the cutoff dependence due to the regulators in the axial-vector two-body
current can significantly affect the Gamow-Teller matrix elements and
consequently also the extracted values for the coupling constant. The
degree of the cutoff dependence is correlated with the softness of the employed
NN interaction. As a result, present three-nucleon forces based on a fit to
H decay underestimate the uncertainty in . We explore a range
of values that is compatible within cutoff variation with the
experimental H half-life and estimate the resulting uncertainties for
many-body systems by performing calculations of symmetric nuclear matter.Comment: 9 pages, 11 figures, published version, includes Erratum, which
corrects Figs. 2-6 due to the incorrect c_D relation between 3N forces and
two-body currents use
The Many Facets of a Diamond: Space and Gender in Selma Lagerlöf’s Antikrists Mirakler and in her Italian Legends
For the first time ever, cutting-edge research about the Swedish Nobel Laureate Selma Lagerlöf and her work is made available to a world-wide audience in one comprehensive volume. Written by an international group of scholars, Re-Mapping Lagerlöf highlights the interdisciplinarity of current Lagerlöf research which frequently cuts across genres, media and disciplines. The structure of the book, with sections dedicated to performance, film and intermediality, transnational narratives and European transmissions, is reinforced by the extensive introductory portal. The authors explore themes such as Lagerlöf in and political contexts, her involvement in the women’s movement, the construction of her celebrity persona, her role for early Swedish film, the transnationality of her work and its impact in international contexts. The volume includes a number of illustrations that are rarely reproduced, and the detailed bibliographical section will contribute to making Re-Mapping Lagerlöf an indispensable platform for Lagerlöf scholarship for years to come. It also offers a model for interdisciplinary research in the arts and humanities
The Paths to Choreography Extraction
Choreographies are global descriptions of interactions among concurrent
components, most notably used in the settings of verification (e.g., Multiparty
Session Types) and synthesis of correct-by-construction software (Choreographic
Programming). They require a top-down approach: programmers first write
choreographies, and then use them to verify or synthesize their programs.
However, most existing software does not come with choreographies yet, which
prevents their application.
To attack this problem, we propose a novel methodology (called choreography
extraction) that, given a set of programs or protocol specifications,
automatically constructs a choreography that describes their behavior. The key
to our extraction is identifying a set of paths in a graph that represents the
symbolic execution of the programs of interest. Our method improves on previous
work in several directions: we can now deal with programs that are equipped
with a state and internal computation capabilities; time complexity is
dramatically better; we capture programs that are correct but not necessarily
synchronizable, i.e., they work because they exploit asynchronous
communication
Position and velocity space diffusion of test particles in stochastic electromagnetic fields
The two--dimensional diffusive dynamics of test particles in a random
electromagnetic field is studied. The synthetic electromagnetic fluctuations
are generated through randomly placed magnetised ``clouds'' oscillating with a
frequency . We investigate the mean square displacements of particles
in both position and velocity spaces. As increases the particles
undergo standard (Brownian--like) motion, anomalous diffusion and ballistic
motion in position space. Although in general the diffusion properties in
velocity space are not trivially related to those in position space, we find
that energization is present only when particles display anomalous diffusion in
position space. The anomalous character of the diffusion is only in the
non--standard values of the scaling exponents while the process is Gaussian.Comment: 10 pages, 4 figure
Quantifying signals with power-law correlations: A comparative study of detrended fluctuation analysis and detrended moving average techniques
Detrended fluctuation analysis (DFA) and detrended moving average (DMA) are
two scaling analysis methods designed to quantify correlations in noisy
non-stationary signals. We systematically study the performance of different
variants of the DMA method when applied to artificially generated long-range
power-law correlated signals with an {\it a-priori} known scaling exponent
and compare them with the DFA method. We find that the scaling
results obtained from different variants of the DMA method strongly depend on
the type of the moving average filter. Further, we investigate the optimal
scaling regime where the DFA and DMA methods accurately quantify the scaling
exponent , and how this regime depends on the correlations in the
signal. Finally, we develop a three-dimensional representation to determine how
the stability of the scaling curves obtained from the DFA and DMA methods
depends on the scale of analysis, the order of detrending, and the order of the
moving average we use, as well as on the type of correlations in the signal.Comment: 15 pages, 16 figure
Economic Ideology and the Rise of the Firm as a Criminal Enterprise
Over the last 50 years, the institutions, ideology, nature, and power of firms in the United States have been radically transformed. Neoclassical economics has led that transformation, supplying an ideology that justified a dramatic increase in top executive compensation while dismantling the mechanisms that produced personal accountability tied to anything but relatively short term shifts in share prices. Yet, alongside the rise of the corporation, from the time of Adam Smith forward, has been concern that the separation of ownership and control creates opportunities to use the corporation as a “weapon” of fraud, and with the return of global financial crises, there has been renewed concern that finance has once again become an agent of crime that threatens the economic order.
This article compares economic and criminological approaches to the corporation. Both approaches focus on incentives and assume that rational actors are responsive to changes such as the dramatic growth in executive financial compensation and the evisceration of other forms of corporate accountability. Both approaches study the separation of ownership and control, and the temptations that come from the ability to speculate with other people’s money. Yet, neoclassical economists assume that markets will police fraud and that fraud therefore need not be a serious subject of study while criminologists posit that the policies that neoclassic economists have championed have created “criminogenic environments” that encourage the use of firms as instruments of fraud.
Criminologists call the use of seemingly legitimate firms to manipulate financial markets “control fraud,” that is, fraud by the persons in charge, most typically starting with the Chief Executive Officer (CEO). Modern executive and professional compensation has transformed the CEO and the independent professionals, such as accountants, who once served as sources of external discipline. Today’s CEO can disguise losses, eliminate underwriting, lay off needed workers and take other measures that boost share prices at the expense of a company’s long term viability. Moreover, if enough executives increase their companies’ apparent profitability (and their own bonuses) in doing so, the result creates a “Gresham’s dynamic” in which bad ethics drives good ethics from the industry and the professions. In these criminogenic environments, control frauds become so pervasive that prosecution becomes extremely difficult and markets do respond—with extremely destructive boom and bust financial cycles
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