BernoulliPub Date : 2020-11-23DOI: 10.3150/21-bej1368
B. Jourdain, W. Margheriti
{"title":"Martingale Wasserstein inequality for probability measures in the convex order","authors":"B. Jourdain, W. Margheriti","doi":"10.3150/21-bej1368","DOIUrl":"https://doi.org/10.3150/21-bej1368","url":null,"abstract":"It is known since [24] that two one-dimensional probability measures in the convex order admit a martingale coupling with respect to which the integral of $vert x-yvert$ is smaller than twice their $mathcal W_1$-distance (Wasserstein distance with index $1$). We showed in [24] that replacing $vert x-yvert$ and $mathcal W_1$ respectively with $vert x-yvert^rho$ and $mathcal W_rho^rho$ does not lead to a finite multiplicative constant. We show here that a finite constant is recovered when replacing $mathcal W_rho^rho$ with the product of $mathcal W_rho$ times the centred $rho$-th moment of the second marginal to the power $rho-1$. Then we study the generalisation of this new stability inequality to higher dimension.","PeriodicalId":55387,"journal":{"name":"Bernoulli","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2020-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43963397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
BernoulliPub Date : 2020-11-20DOI: 10.3150/22-bej1485
Quentin Duchemin, Y. D. Castro, C. Lacour
{"title":"Concentration inequality for U-statistics of order two for uniformly ergodic Markov chains","authors":"Quentin Duchemin, Y. D. Castro, C. Lacour","doi":"10.3150/22-bej1485","DOIUrl":"https://doi.org/10.3150/22-bej1485","url":null,"abstract":"We prove a new concentration inequality for U-statistics of order two for uniformly ergodic Markov chains. Working with bounded π-canonical kernels, we show that we can recover the convergence rate of Arcones and Gine (1993) who proved a concentration result for U-statistics of independent random variables and canonical kernels. Our proof relies on an inductive analysis where we use martingale techniques, uniform ergodicity, Nummelin splitting and Bernstein's type inequality where the spectral gap of the chain emerges. Our result allows us to conduct three applications. First, we establish a new exponential inequality for the estimation of spectra of trace class integral operators with MCMC methods. The novelty is that this result holds for kernels with positive and negative eigenvalues, which is new as far as we know. In addition, we investigate generalization performance of online algorithms working with pairwise loss functions and Markov chain samples. We provide an online-to-batch conversion result by showing how we can extract a low risk hypothesis from the sequence of hypotheses generated by any online learner. We finally give a non-asymptotic analysis of a goodness-of-fit test on the density of the invariant measure of a Markov chain. We identify the classes of alternatives over which our test based on the L2 distance has a prescribed power.","PeriodicalId":55387,"journal":{"name":"Bernoulli","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2020-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46570568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
BernoulliPub Date : 2020-11-17DOI: 10.3150/21-bej1393
G. Kersting, C. Minuesa
{"title":"Defective Galton-Watson processes in a varying environment","authors":"G. Kersting, C. Minuesa","doi":"10.3150/21-bej1393","DOIUrl":"https://doi.org/10.3150/21-bej1393","url":null,"abstract":"We study an extension of the so-called defective Galton-Watson processes obtained by allowing the offspring distribution to change over the generations. Thus, in these processes, the individuals reproduce independently of the others and in accordance to some possibly defective offspring distribution depending on the generation. Moreover, the defect $1-f_n(1)$ of the offspring distribution at generation $n$ represents the probability that the process hits an absorbing state $Delta$ at that generation. We focus on the asymptotic behaviour of these processes. We establish the almost sure convergence of the process to a random variable with values in $mathbb{N}_0cup{Delta}$ and we provide two characterisations of the duality extinction-absorption at $Delta$. We also state some results on the absorption time and the properties of the process conditioned upon its non-absorption, some of which require us to introduce the notion of defective branching trees in varying environment.","PeriodicalId":55387,"journal":{"name":"Bernoulli","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2020-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47845376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
BernoulliPub Date : 2020-11-16DOI: 10.3150/21-bej1413
D. Belomestny, S. Gugushvili, Moritz Schauer, P. Spreij
{"title":"Nonparametric Bayesian volatility estimation for gamma-driven stochastic differential equations","authors":"D. Belomestny, S. Gugushvili, Moritz Schauer, P. Spreij","doi":"10.3150/21-bej1413","DOIUrl":"https://doi.org/10.3150/21-bej1413","url":null,"abstract":"We study a nonparametric Bayesian approach to estimation of the volatility function of a stochastic differential equation driven by a gamma process. The volatility function is modelled a priori as piecewise constant, and we specify a gamma prior on its values. This leads to a straightforward procedure for posterior inference via an MCMC procedure. We give theoretical performance guarantees (contraction rates for the posterior) for the Bayesian estimate in terms of the regularity of the unknown volatility function. We illustrate the method on synthetic and real data examples.","PeriodicalId":55387,"journal":{"name":"Bernoulli","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46156393","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
BernoulliPub Date : 2020-11-11DOI: 10.3150/21-bej1362
P. Doukhan, Anne Leucht, Michael H. Neumann
{"title":"Mixing properties of non-stationary INGARCH(1,1) processes","authors":"P. Doukhan, Anne Leucht, Michael H. Neumann","doi":"10.3150/21-bej1362","DOIUrl":"https://doi.org/10.3150/21-bej1362","url":null,"abstract":"We derive mixing properties for a broad class of Poisson count time series satisfying a certain contraction condition. Using specific coupling techniques, we prove absolute regularity at a geometric rate not only for stationary Poisson-GARCH processes but also for models with an explosive trend. We provide easily verifiable sufficient conditions for absolute regularity for a variety of models including classical (log-)linear models. Finally, we illustrate the practical use of our results for hypothesis testing.","PeriodicalId":55387,"journal":{"name":"Bernoulli","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2020-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43778612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
BernoulliPub Date : 2020-11-11DOI: 10.3150/21-bej1456
M. Hallin, D. L. Vecchia, Han Liu
{"title":"Rank-based testing for semiparametric VAR models: A measure transportation approach","authors":"M. Hallin, D. L. Vecchia, Han Liu","doi":"10.3150/21-bej1456","DOIUrl":"https://doi.org/10.3150/21-bej1456","url":null,"abstract":"We develop a class of tests for semiparametric vector autoregressive (VAR) models with unspecified innovation densities, based on the recent measure-transportation-based concepts of multivariate center-outward ranks and signs. We show that these concepts, combined with Le Cam's asymptotic theory of statistical experiments, yield novel testing procedures, which (a) are valid under a broad class of innovation densities (possibly non-elliptical, skewed, and/or with infinite moments), (b) are optimal (locally asymptotically maximin or most stringent) at selected ones, and (c) are robust against additive outliers. In order to do so, we establish a Hajek asymptotic representation result, of independent interest, for a general class of center-outward rank-based serial statistics. As an illustration, we consider the problems of testing the absence of serial correlation in multiple-output and possibly non-linear regression (an extension of the classical Durbin-Watson problem) and the sequential identification of the order p of a vector autoregressive (VAR(p)) model. A Monte Carlo comparative study of our tests and their routinely-applied Gaussian competitors demonstrates the benefits (in terms of size, power, and robustness) of our methodology; these benefits are particularly significant in the presence of asymmetric and leptokurtic innovation densities. A real data application concludes the paper.","PeriodicalId":55387,"journal":{"name":"Bernoulli","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2020-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49488933","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
BernoulliPub Date : 2020-11-02DOI: 10.3150/20-bej1211
V. Todorov
{"title":"Testing and inference for fixed times of discontinuity in semimartingales","authors":"V. Todorov","doi":"10.3150/20-bej1211","DOIUrl":"https://doi.org/10.3150/20-bej1211","url":null,"abstract":"We develop a nonparametric test for deciding whether a semimartingale process, modeling an asset price, contains a fixed time of discontinuity, i.e., a positive probability of a jump, at a given point in time, and we further propose a rate-optimal estimator of the jump distribution when this is the case. Itô semimartingales used commonly in applied work have absolutely continuous in time, with respect to Lebesgue measure, jump compensators, and this rules out fixed times of discontinuity in their paths. However, certain phenomena, such as scheduled economic announcements in finance, make the existence of such discontinuities a possibility. The inference in the paper is based on noisy observations of options written on the asset with different strikes and two different expiration dates. The asymptotics is joint in which the times to maturity of the options shrink to zero and the number of observed options increases to infinity. The test is based on estimates of the characteristic function of the increments of the semimartingale, constructed from the option data, and the fact that the asymptotic limit of the increments and their characteristic functions is different with and without fixed time of discontinuity. The limit distribution of the test statistic is derived and feasible inference is developed on the basis of wild bootstrap type techniques. A Monte Carlo and an empirical illustration show the applicability of the developed inference procedures.","PeriodicalId":55387,"journal":{"name":"Bernoulli","volume":"26 1","pages":"2907-2948"},"PeriodicalIF":1.5,"publicationDate":"2020-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45406255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
BernoulliPub Date : 2020-11-01DOI: 10.3150/19-bej1164
Victor-Emmanuel Brunel
{"title":"Deviation inequalities for random polytopes in arbitrary convex bodies","authors":"Victor-Emmanuel Brunel","doi":"10.3150/19-bej1164","DOIUrl":"https://doi.org/10.3150/19-bej1164","url":null,"abstract":"","PeriodicalId":55387,"journal":{"name":"Bernoulli","volume":"26 1","pages":"2488-2502"},"PeriodicalIF":1.5,"publicationDate":"2020-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41782388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
BernoulliPub Date : 2020-11-01DOI: 10.3150/20-bej1209
Luo Xiao
{"title":"Asymptotic properties of penalized splines for functional data","authors":"Luo Xiao","doi":"10.3150/20-bej1209","DOIUrl":"https://doi.org/10.3150/20-bej1209","url":null,"abstract":"Penalized spline methods are popular for functional data analysis but their asymptotic properties have not been developed. We present a theoretic study of the L2 and uniform convergence of penalized spline estimators for estimating the mean and covariance functions for functional data under general settings. The established convergence rates for the mean function estimation are mini-max rate optimal and the rates for the covariance function estimation are comparable to those using other smoothing methods.","PeriodicalId":55387,"journal":{"name":"Bernoulli","volume":"26 1","pages":"2847-2875"},"PeriodicalIF":1.5,"publicationDate":"2020-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47507222","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
BernoulliPub Date : 2020-10-23DOI: 10.3150/22-bej1472
Hamid Eftekhari, M. Banerjee, Y. Ritov
{"title":"Design of c-optimal experiments for high-dimensional linear models","authors":"Hamid Eftekhari, M. Banerjee, Y. Ritov","doi":"10.3150/22-bej1472","DOIUrl":"https://doi.org/10.3150/22-bej1472","url":null,"abstract":"We study random designs that minimize the asymptotic variance of a de-biased lasso estimator when a large pool of unlabeled data is available but measuring the corresponding responses is costly. The optimal sampling distribution arises as the solution of a semidefinite program. The improvements in efficiency that result from these optimal designs are demonstrated via simulation experiments.","PeriodicalId":55387,"journal":{"name":"Bernoulli","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2020-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44623316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}