4,780 research outputs found
Borel-de Siebenthal theory for affine reflection systems
We develop a Borel-de Siebenthal theory for affine reflection systems by
classifying their maximal closed subroot systems. Affine reflection systems
(introduced by Loos and Neher) provide a unifying framework for root systems of
finite-dimensional semi-simple Lie algebras, affine and toroidal Lie algebras,
and extended affine Lie algebras. In the special case of nullity toroidal
Lie algebras, we obtain a one-to-one correspondence between maximal closed
subroot systems with full gradient and triples , where is a
prime number, is a -tuple of integers in the interval and
is a Hermite normal form matrix with determinant . This
generalizes the result of Dyer and Lehrer in the setting of affine Lie
algebras
Twisted Demazure modules, fusion product decomposition and twisted Q--systems
In this paper, we introduce a family of indecomposable finite-dimensional
graded modules for the twisted current algebras. These modules are indexed by
an -tuple of partitions \bxi=(\xi^{\alpha})_{\alpha\in R^+} satisfying
a natural compatibility condition. We give three equivalent presentations of
these modules and show that for a particular choice of \bxi these modules
become isomorphic to Demazure modules in various levels for the twisted affine
algebras. As a consequence we see that the defining relations of twisted
Demazure modules can be greatly simplified. Furthermore, we investigate the
notion of fusion products for twisted modules, first defined in \cite{FL99} for
untwisted modules, and use the simplified presentation to prove a fusion
product decomposition of twisted Demazure modules. As a consequence we prove
that twisted Demazure modules can be obtained by taking the associated graded
modules of (untwisted) Demazure modules for simply-laced affine algebras.
Furthermore we give a semi-infinite fusion product construction for the
irreducible representations of twisted affine algebras. Finally, we prove that
the twisted -sytem defined in \cite{HKOTT02} extends to a non-canonical
short exact sequence of fusion products of twisted Demazure modules
The increasing importance of economic conditions on fertility
This paper investigates whether there has been a fundamental change in the importance of economic conditions on fertility. Through the 1980s econometric studies had found at best a mixed, neutral or negative effect of economic conditions on fertility. Notably, Butz and Ward (1979) concluded that fertility was counter-cyclical, with fertility falling in good times, as the opportunity costs of childbearing rose. More recently, there have been signs that fluctuations in fertility have been pro-cyclical, with good economic times being associated with higher birth rates, and the recent recession with lower birth rates. In this paper, we use panel methods to study short term changes in aggregate fertility and economic measures in OECD countries from 1976-2008. We find indeed that fertility became positively associated with good economic conditions. Furthermore, the increasing importance of economic conditions was detected for both tempo and quantum.economic conditions, total fertility rate
Gate induced monolayer behavior in twisted bilayer black phosphorus
Optical and electronic properties of black phosphorus strongly depend on the
number of layers and type of stacking. Using first-principles calculations
within the framework of density functional theory, we investigate the
electronic properties of bilayer black phosphorus with an interlayer twist
angle of 90. These calculations are complemented with a simple
model which is able to capture most of the low energy
features and is valid for arbitrary twist angles. The electronic spectrum of
90 twisted bilayer black phosphorus is found to be x-y isotropic in
contrast to the monolayer. However x-y anisotropy, and a partial return to
monolayer-like behavior, particularly in the valence band, can be induced by an
external out-of-plane electric field. Moreover, the preferred hole effective
mass can be rotated by 90 simply by changing the direction of the
applied electric field. In particular, a +0.4 (-0.4) V/{\AA} out-of-plane
electric field results in a 60\% increase in the hole effective mass
along the y (x) axis and enhances the ()
ratio as much as by a factor of 40. Our DFT and
simulations clearly indicate that the twist angle in combination with an
appropriate gate voltage is a novel way to tune the electronic and optical
properties of bilayer phosphorus and it gives us a new degree of freedom to
engineer the properties of black phosphorus based devices.Comment: 8 pages, 8 figure
Was Levinas an Antiphilosopher? Archi-ethics and the Jewish Experience of the Prisoner
This paper explores Levinas’s Carnets de captivité and Écrits sur la captivité in light of Badiou’s category of ‘antiphilosophy’. We make four movements: firstly, a description of what antiphilosophy is; secondly, an explanation of why the category of antiphilosophy is important to a reading of Levinas; thirdly, an exposition of the antiphilosophical elements of the Carnets and Écrits on captivity; and fourthly, we situate our reading of the notebooks within the larger context of Levinas’s post-captivity work.
The Idea of Sustainable Development in Public Administration
This article introduces the Focus Issue on Sustainable Development by first discussing the environmental problems caused by unsustainable development and then the shortcomings caused by a piecemeal approach to policy development and implementation. The idea of sustainability appears to fit well with other core values of public administration, which is a consistent theme throughout each of the articles in this issue. Definitions of sustainability are discussed, followed by two relevant models. Finally, each article in the focus issue is introduced
Velocity Correlations in Dense Gravity Driven Granular Chute Flow
We report numerical results for velocity correlations in dense,
gravity-driven granular flow down an inclined plane. For the grains on the
surface layer, our results are consistent with experimental measurements
reported by Pouliquen. We show that the correlation structure within planes
parallel to the surface persists in the bulk. The two-point velocity
correlation function exhibits exponential decay for small to intermediate
values of the separation between spheres. The correlation lengths identified by
exponential fits to the data show nontrivial dependence on the averaging time
\dt used to determine grain velocities. We discuss the correlation length
dependence on averaging time, incline angle, pile height, depth of the layer,
system size and grain stiffness, and relate the results to other length scales
associated with the rheology of the system. We find that correlation lengths
are typically quite small, of the order of a particle diameter, and increase
approximately logarithmically with a minimum pile height for which flow is
possible, \hstop, contrary to the theoretical expectation of a proportional
relationship between the two length scales.Comment: 21 pages, 16 figure
Identities of the multi-variate independence polynomials from heaps theory
We study and derive identities for the multi-variate independence polynomials
from the perspective of heaps theory. Using the inversion formula and the
combinatorics of partially commutative algebras we show how the multi-variate
version of Godsil type identity as well as the fundamental identity can be
obtained from weight preserving bijections. Finally, we obtain a new
multi-variate identity involving connected bipartite subgraphs similar to the
Christoffel-Darboux type identities obtained by Bencs
HapTree-X: An Integrative Bayesian Framework for Haplotype Reconstruction from Transcriptome and Genome Sequencing Data
By running standard genotype calling tools, it is possible to accurately identify the number of wild type and mutant alleles for each single-nucleotide polymorphism (SNP) site. However, in the case of two heterozygous SNP sites, genotype calling tools cannot determine whether mutant alleles from different SNP loci are on the same chromosome or on different homologous chromosomes (i.e. compound heterozygote)
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