48,181 research outputs found
From nominal to higher-order rewriting and back again
We present a translation function from nominal rewriting systems (NRSs) to
combinatory reduction systems (CRSs), transforming closed nominal rules and
ground nominal terms to CRSs rules and terms, respectively, while preserving
the rewriting relation. We also provide a reduction-preserving translation in
the other direction, from CRSs to NRSs, improving over a previously defined
translation. These tools, together with existing translations between CRSs and
other higher-order rewriting formalisms, open up the path for a transfer of
results between higher-order and nominal rewriting. In particular, techniques
and properties of the rewriting relation, such as termination, can be exported
from one formalism to the other.Comment: 41 pages, journa
The Econometrics of DSGE Models
In this paper, I review the literature on the formulation and estimation of dynamic stochastic general equilibrium (DSGE) models with a special emphasis on Bayesian methods. First, I discuss the evolution of DSGE models over the last couple of decades. Second, I explain why the profession has decided to estimate these models using Bayesian methods. Third, I briefly introduce some of the techniques required to compute and estimate these models. Fourth, I illustrate the techniques under consideration by estimating a benchmark DSGE model with real and nominal rigidities. I conclude by offering some pointers for future research.DSGE Models, Likelihood Estimation, Bayesian Methods
Invariant versus classical quartet inference when evolution is heterogeneous across sites and lineages
One reason why classical phylogenetic reconstruction methods fail to
correctly infer the underlying topology is because they assume oversimplified
models. In this paper we propose a topology reconstruction method consistent
with the most general Markov model of nucleotide substitution, which can also
deal with data coming from mixtures on the same topology. It is based on an
idea of Eriksson on using phylogenetic invariants and provides a system of
weights that can be used as input of quartet-based methods. We study its
performance on real data and on a wide range of simulated 4-taxon data (both
time-homogeneous and nonhomogeneous, with or without among-site rate
heterogeneity, and with different branch length settings). We compare it to the
classical methods of neighbor-joining (with paralinear distance), maximum
likelihood (with different underlying models), and maximum parsimony. Our
results show that this method is accurate and robust, has a similar performance
to ML when data satisfies the assumptions of both methods, and outperforms all
methods when these are based on inappropriate substitution models or when both
long and short branches are present. If alignments are long enough, then it
also outperforms other methods when some of its assumptions are violated.Comment: 32 pages; 9 figure
A General Model of Bilateral Migration Agreements
Unilateral migration policies impose externalities on other countries. In order to try to internalize these externalities, countries sign bilateral migration agreements. One element of these agreements is the emphasis on enforcing migration policies: immigrant-receiving countries agree to allow more immigrants from their emigrant-sending partner if they cooperate in enforcing their migration policy at the border. I present a simple theoretical model that justifies this behavior in a two-country setting with welfare maximizing governments. These governments establish migration quotas that need to be enforced at a cost. I prove that uncoordinated migration policies are inefficient. Both countries can improve welfare by exchanging a more "generous" migration quota for expenditure on enforcement policy. Contrary to what could be expected, this result does not depend on the enforcement technology that both countries employ.international migration, cooperation, migration policy
Gevrey expansions of hypergeometric integrals II
We study integral representations of the Gevrey series solutions of irregular
hypergeometric systems under certain assumptions. We prove that, for such
systems, any Gevrey series solution, along a coordinate hyperplane of its
singular support, is the asymptotic expansion of a holomorphic solution given
by a carefully chosen integral representation.Comment: 27 pages, 2 figure
Local description of phylogenetic group-based models
Motivated by phylogenetics, our aim is to obtain a system of equations that
define a phylogenetic variety on an open set containing the biologically
meaningful points. In this paper we consider phylogenetic varieties defined via
group-based models. For any finite abelian group , we provide an explicit
construction of phylogenetic invariants (polynomial equations) of
degree at most that define the variety on a Zariski open set . The
set contains all biologically meaningful points when is the group of
the Kimura 3-parameter model. In particular, our main result confirms a
conjecture by the third author and, on the set , a couple of conjectures by
Bernd Sturmfels and Seth Sullivant.Comment: 22 pages, 7 figure
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