9,332 research outputs found
Dynamic Efficiency, the Riskless Rate, and Debt Ponzi Games under Uncertainty.
In a dynamically efficient economy, can a government roll its debt forever and avoid the need to raise taxes? In a series of examples of economies with zero growth, this paper shows that such Ponzi games may be infeasible even when the average rate of return on bonds is negative, and may be feasible even when the average rate of return on bonds is positive. The paper then reveals the structure which underlies these examples.
Operations between sets in geometry
An investigation is launched into the fundamental characteristics of
operations on and between sets, with a focus on compact convex sets and star
sets (compact sets star-shaped with respect to the origin) in -dimensional
Euclidean space . For example, it is proved that if , with three
trivial exceptions, an operation between origin-symmetric compact convex sets
is continuous in the Hausdorff metric, GL(n) covariant, and associative if and
only if it is addition for some . It is also
demonstrated that if , an operation * between compact convex sets is
continuous in the Hausdorff metric, GL(n) covariant, and has the identity
property (i.e., for all compact convex sets , where
denotes the origin) if and only if it is Minkowski addition. Some analogous
results for operations between star sets are obtained. An operation called
-addition is generalized and systematically studied for the first time.
Geometric-analytic formulas that characterize continuous and GL(n)-covariant
operations between compact convex sets in terms of -addition are
established. The term "polynomial volume" is introduced for the property of
operations * between compact convex or star sets that the volume of ,
, is a polynomial in the variables and . It is proved that if
, with three trivial exceptions, an operation between origin-symmetric
compact convex sets is continuous in the Hausdorff metric, GL(n) covariant,
associative, and has polynomial volume if and only if it is Minkowski addition
A review of factors that influence individual compliance with mass drug administration for elimination of lymphatic filariasis.
BACKGROUND: The success of programs to eliminate lymphatic filariasis (LF) depends in large part on their ability to achieve and sustain high levels of compliance with mass drug administration (MDA). This paper reports results from a comprehensive review of factors that affect compliance with MDA. METHODOLOGY/PRINCIPAL FINDINGS: Papers published between 2000 and 2012 were considered, and 79 publications were included in the final dataset for analysis after two rounds of selection. While results varied in different settings, some common features were associated with successful programs and with compliance by individuals. Training and motivation of drug distributors is critically important, because these people directly interact with target populations, and their actions can affect MDA compliance decisions by families and individuals. Other important programmatic issues include thorough preparation of personnel, supplies, and logistics for implementation and preparation of the population for MDA. Demographic factors (age, sex, income level, and area of residence) are often associated with compliance by individuals, but compliance decisions are also affected by perceptions of the potential benefits of participation versus the risk of adverse events. Trust and information can sometimes offset fear of the unknown. While no single formula can ensure success MDA in all settings, five key ingredients were identified: engender trust, tailor programs to local conditions, take actions to minimize the impact of adverse events, promote the broader benefits of the MDA program, and directly address the issue of systematic non-compliance, which harms communities by prolonging their exposure to LF. CONCLUSIONS/SIGNIFICANCE: This review has identified factors that promote coverage and compliance with MDA for LF elimination across countries. This information may be helpful for explaining results that do not meet expectations and for developing remedies for ailing MDA programs. Our review has also identified gaps in understanding and suggested priority areas for further research
Canonical decomposition of linear differential operators with selected differential Galois groups
We revisit an order-six linear differential operator having a solution which
is a diagonal of a rational function of three variables. Its exterior square
has a rational solution, indicating that it has a selected differential Galois
group, and is actually homomorphic to its adjoint. We obtain the two
corresponding intertwiners giving this homomorphism to the adjoint. We show
that these intertwiners are also homomorphic to their adjoint and have a simple
decomposition, already underlined in a previous paper, in terms of order-two
self-adjoint operators. From these results, we deduce a new form of
decomposition of operators for this selected order-six linear differential
operator in terms of three order-two self-adjoint operators. We then generalize
the previous decomposition to decompositions in terms of an arbitrary number of
self-adjoint operators of the same parity order. This yields an infinite family
of linear differential operators homomorphic to their adjoint, and, thus, with
a selected differential Galois group. We show that the equivalence of such
operators is compatible with these canonical decompositions. The rational
solutions of the symmetric, or exterior, squares of these selected operators
are, noticeably, seen to depend only on the rightmost self-adjoint operator in
the decomposition. These results, and tools, are applied on operators of large
orders. For instance, it is seen that a large set of (quite massive) operators,
associated with reflexive 4-polytopes defining Calabi-Yau 3-folds, obtained
recently by P. Lairez, correspond to a particular form of the decomposition
detailed in this paper.Comment: 40 page
Non-integrability of the generalised spring-pendulum problem
We investigate a generalisation of the three dimensional spring-pendulum
system. The problem depends on two real parameters , where is the
Young modulus of the spring and describes the nonlinearity of elastic
forces. We show that this system is not integrable when . We
carefully investigated the case when the necessary condition for
integrability given by the Morales-Ramis theory is satisfied. We discuss an
application of the higher order variational equations for proving the
non-integrability in this case.Comment: 20 pages, 1 figur
Dileptons in a coarse-grained transport approach
We calculate dilepton spectra in heavy-ion collisions using a coarse-graining
approach to the simulation of the created medium with the UrQMD transport
model. This enables the use of dilepton-production rates evaluated in
equilibrium quantum-field theory at finite temperatures and chemical
potentials.Comment: 4 pages, 2 figures, contribution to the proceedings of "The 15th
International Conference on Strangeness in Quark Matter" (SQM 2015), 06-11
July in Dubna, Russi
Lateral-directional control of the x-15 airplane
Lateral directional control and stability characteristics of X-15 aircraf
Globally nilpotent differential operators and the square Ising model
We recall various multiple integrals related to the isotropic square Ising
model, and corresponding, respectively, to the n-particle contributions of the
magnetic susceptibility, to the (lattice) form factors, to the two-point
correlation functions and to their lambda-extensions. These integrals are
holonomic and even G-functions: they satisfy Fuchsian linear differential
equations with polynomial coefficients and have some arithmetic properties. We
recall the explicit forms, found in previous work, of these Fuchsian equations.
These differential operators are very selected Fuchsian linear differential
operators, and their remarkable properties have a deep geometrical origin: they
are all globally nilpotent, or, sometimes, even have zero p-curvature. Focusing
on the factorised parts of all these operators, we find out that the global
nilpotence of the factors corresponds to a set of selected structures of
algebraic geometry: elliptic curves, modular curves, and even a remarkable
weight-1 modular form emerging in the three-particle contribution
of the magnetic susceptibility of the square Ising model. In the case where we
do not have G-functions, but Hamburger functions (one irregular singularity at
0 or ) that correspond to the confluence of singularities in the
scaling limit, the p-curvature is also found to verify new structures
associated with simple deformations of the nilpotent property.Comment: 55 page
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