2,837 research outputs found
Australian Asian options
We study European options on the ratio of the stock price to its average and viceversa. Some of these options are traded in the Australian Stock Exchange since 1992, thus we call them Australian Asian options. For geometric averages, we obtain closed-form expressions for option prices. For arithmetic means, we use dierent approximations that produce very similar results.Asian options, arithmetic average, geometric average, edgeworth expansion, lognormal distribution, gamma distribution
Consistency of objective Bayes factors as the model dimension grows
In the class of normal regression models with a finite number of regressors,
and for a wide class of prior distributions, a Bayesian model selection
procedure based on the Bayes factor is consistent [Casella and Moreno J. Amer.
Statist. Assoc. 104 (2009) 1261--1271]. However, in models where the number of
parameters increases as the sample size increases, properties of the Bayes
factor are not totally understood. Here we study consistency of the Bayes
factors for nested normal linear models when the number of regressors increases
with the sample size. We pay attention to two successful tools for model
selection [Schwarz Ann. Statist. 6 (1978) 461--464] approximation to the Bayes
factor, and the Bayes factor for intrinsic priors [Berger and Pericchi J. Amer.
Statist. Assoc. 91 (1996) 109--122, Moreno, Bertolino and Racugno J. Amer.
Statist. Assoc. 93 (1998) 1451--1460]. We find that the the Schwarz
approximation and the Bayes factor for intrinsic priors are consistent when the
rate of growth of the dimension of the bigger model is for . When
the Schwarz approximation is always inconsistent under the alternative
while the Bayes factor for intrinsic priors is consistent except for a small
set of alternative models which is characterized.Comment: Published in at http://dx.doi.org/10.1214/09-AOS754 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Energy partition and segregation for an intruder in a vibrated granular system under gravity
The difference of temperatures between an impurity and the surrounding gas in
an open vibrated granular system is studied. It is shown that, in spite of the
high inhomogeneity of the state, the temperature ratio remains constant in the
bulk of the system. The lack of energy equipartition is associated to the
change of sign of the pressure diffusion coefficient for the impurity at
certain values of the parameters of the system, leading to a segregation
criterium. The theoretical predictions are consistent with previous
experimental results, and also in agreement with molecular dynamics simulation
results reported in this paper.Comment: To appear in Phys. Rev. Let
Consistency of Bayesian procedures for variable selection
It has long been known that for the comparison of pairwise nested models, a
decision based on the Bayes factor produces a consistent model selector (in the
frequentist sense). Here we go beyond the usual consistency for nested pairwise
models, and show that for a wide class of prior distributions, including
intrinsic priors, the corresponding Bayesian procedure for variable selection
in normal regression is consistent in the entire class of normal linear models.
We find that the asymptotics of the Bayes factors for intrinsic priors are
equivalent to those of the Schwarz (BIC) criterion. Also, recall that the
Jeffreys--Lindley paradox refers to the well-known fact that a point null
hypothesis on the normal mean parameter is always accepted when the variance of
the conjugate prior goes to infinity. This implies that some limiting forms of
proper prior distributions are not necessarily suitable for testing problems.
Intrinsic priors are limits of proper prior distributions, and for finite
sample sizes they have been proved to behave extremely well for variable
selection in regression; a consequence of our results is that for intrinsic
priors Lindley's paradox does not arise.Comment: Published in at http://dx.doi.org/10.1214/08-AOS606 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org
On the frequentist and Bayesian approaches to hypothesis testing
Hypothesis testing is a model selection problem for which the solution proposed by the two main statistical streams of thought, frequentists and Bayesians, substantially differ. One may think that this fact might be due to the prior chosen in the Bayesian analysis and that a convenient prior selection may reconcile both approaches. However, the Bayesian robustness viewpoint has shown that, in general, this is not so and hence a profound disagreement between both approaches exists. In this paper we briefly revise the basic aspects of hypothesis testing for both the frequentist and Bayesian procedures and discuss the variable selection problem in normal linear regression for which the discrepancies are more apparent. Illustrations on simulated and real data are given
Symmetry breaking and clustering in a vibrated granular gas with several macroscopically connected compartments
The spontaneous symmetry breaking in a vibro-fluidized low-density granular
gas in three connected compartments is investigated. When the total number of
particles in the system becomes large enough, particles distribute themselves
unequally among the three compartments. Particles tend to concentrate in one of
the compartments, the other two having the (relatively small) same average
number of particles. A hydrodynamical model that accurately predicts the
bifurcation diagram of the system is presented. The theory can be easily
extended to the case of an arbitrary number of connected compartments
2S Albumin Storage Proteins: What Makes them Food Allergens?
2S albumin storage proteins are becoming of increasing interest in nutritional and clinical studies as they have been reported as major food allergens in seeds of many mono- and di-cotyledonous plants. This review describes the main biochemical, structural and functional properties of these proteins thought to play a role in determining their potential allergenicity. 2S albumins are considered to sensitize directly via the gastrointestinal tract (GIT). The high stability of their intrinsic protein structure, dominated by a well-conserved skeleton of cysteine residues, to the harsh conditions present in the GIT suggests that these proteins are able to cross the gut mucosal barrier to sensitize the mucosal immune system and/or elicit an allergic response. The flexible and solvent-exposed hypervariable region of these proteins is immunodominant and has the ability to bind IgE from allergic patients´ sera. Several linear IgE-binding epitopes of 2S albumins spanning this region have been described to play a major role in allergenicity; the role of conformational epitopes of these proteins in food allergy is far from being understood and need to be investigated. Finally, the interaction of these proteins with other components of the food matrix might influence the absorption rates of immunologically reactive 2S albumins but also in their immune response
Uncertainty representation in software models: a survey
This paper provides a comprehensive overview and analysis of research work on how uncertainty is currently represented in software models. The survey presents the definitions and current research status of different proposals for addressing uncertainty modeling and introduces a classification framework that allows to compare and classify existing proposals, analyze their current status and identify new trends. In addition, we discuss possible future research directions, opportunities and challenges.This work is partially supported by the European Commission (FEDER) and the Spanish Government under projects APOLO (US1264651), HORATIO (RTI2018-101204-B-C21), EKIPMENT-PLUS (P18-FR-2895) and COSCA (PGC2018-094905-B-I00)
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