Results 11 to 20 of about 142 (139)
Assessing the role of spatial externalities in the survival of Italian innovative startups
Regional Science Policy &Practice, EarlyView., 2023 Abstract The paper provides novel empirical evidence about the effects of spatial externalities on the survival of innovative startups in Italy. Using geocoded firm‐level data, we build micro‐geographic measures of specialization and diversity that are robust to the modifiable areal unit problem.
Diego Giuliani +4 more
wiley +1 more source
Stochastic Gradient Descent in High Dimensions for Multi‐Spiked Tensor PCA
Communications on Pure and Applied Mathematics, EarlyView.ABSTRACT We study the high‐dimensional dynamics of online stochastic gradient descent (SGD) for the multi‐spiked tensor model. This multi‐index model arises from the tensor principal component analysis (PCA) problem with multiple spikes, where the goal is to estimate the unknown signal vectors within the N$N$‐dimensional unit sphere through maximum ...
Gérard Ben Arous +2 more
wiley +1 more source
Journal of Applied Econometrics, EarlyView.ABSTRACT We present four novel tests of equal predictive accuracy and encompassing á Pitarakis (2023, 2025) for factor‐augmented regressions. Factors are estimated using cross‐section averages (CAs) of grouped series and our theoretical findings are empirically relevant: asymptotic normality, robustness to an overspecification of the number of factors,
Alessandro Morico, Ovidijus Stauskas
wiley +1 more source
Stability results for martingale representations: The general case
Transactions of the American Mathematical Society, 2019 In this paper, we obtain stability results for martingale representations in a very general framework. More specifically, we consider a sequence of martingales, each adapted to its own filtration, and a sequence of random variables measurable with respect to those filtrations.
Papapantoleon, Antonis +2 more
openaire +4 more sources
A Joint Test of Unconfoundedness and Common Trends
Journal of Applied Econometrics, EarlyView.ABSTRACT We introduce an overidentification test of two alternative assumptions to identify the average treatment effect on the treated in a two‐period panel data setting: unconfoundedness and common trends. Under unconfoundedness, treatment assignment and post‐treatment outcomes are independent, conditional on control variables and pre‐treatment ...
Martin Huber, Eva‐Maria Oeß
wiley +1 more source
Models of Viscous Fluids Generated by Martingales on the Groups of Diffeomorphisms
Journal of Computational and Engineering Mathematics, 2023 Summary: We study two martingales on the group of Sobolev diffeomorphisms of the flat \(n\)-dimensional torus, they both are described by systems of two special equations with mean derivatives. The first one describes a solution of the Burgers equation on the torus that also satisfies an analog of continuity equation.
Gliklikh, Yuriĭ Evgen'evich +1 more
openaire +2 more sources
Stop Using Limiting Stimuli as a Measure of Sensitivities of Energetic Materials
Propellants, Explosives, Pyrotechnics, EarlyView.ABSTRACT Accurately estimating the sensitivity of explosive materials is a potentially life‐saving task that requires standardised protocols across nations. One of the most widely applied procedures worldwide is the so‐called ‘1‐In‐6’ test from the United Nations (UN) Manual of Tests in Criteria, which estimates a ‘limiting stimulus’ for a material. In
Dennis Christensen, Geir Petter Novik
wiley +1 more source
A generalization of Cramér large deviations for martingales
Comptes Rendus. Mathématique, 2014 In this note, we give a generalization of Cramér's large deviations for martingales, which can be regarded as a supplement of Fan et al. (2013) [3]. Our method is based on the change of probability measure developed by Grama and Haeusler (2000) [6].
Fan, Xiequan, Grama, Ion, Liu, Quansheng
openaire +4 more sources
Deepening the real options debate: Real options as dynamic optimization
Strategic Management Journal, EarlyView.Abstract Research Summary Is real option theory useful for management research? This topic was hotly debated two decades ago. Real options were said to be inapplicable to management research and to lack conceptual distinctiveness. Whereas responses to the claim about the non‐distinctiveness of real options were disparate, the concern about the theory's
Arkadiy V. Sakhartov +2 more
wiley +1 more source
Generalization of Itô's formula for smooth nondegenerate martingales
Stochastic Processes and their Applications, 2001 Let \(W\) be a \(d\)-dimensional Wiener process, \(X=(X_ {t}) _ {0\leq t\leq T}\) a \(d\)-dimensional continuous local martingale adapted to \(W\) and satisfying certain nondegeneracy hypotheses. It is proven that if \(f\in L^ {p}_ {\text{loc}}(\mathbb R^ {d})\) for some \(p>d\), then the quadratic covariation of the processes \(f(X)\) and \(X^ {i}\), \
Moret, S., Nualart, D.
openaire +2 more sources