102,162 research outputs found
Bott–Chern Laplacian on almost Hermitian manifolds
No full textLet (M, J, g, ω) be a 2n-dimensional almost Hermitian manifold. We extend the definition of the Bott–Chern Laplacian on (M, J, g, ω) , proving that it is still elliptic. On a compact Kähler manifold, the kernels of the Dolbeault Laplacian and of the Bott–Chern Laplacian coincide. We show that such a property does not hold when (M, J, g, ω) is a compact almost Kähler manifold, providing an explicit almost Kähler structure on the Kodaira–Thurston manifold. Furthermore, if (M, J, g, ω) is a connected compact almost Hermitian 4-manifold, denoting by hBC1,1 the dimension of the space of Bott–Chern harmonic (1, 1)-forms, we prove that either hBC1,1=b- or hBC1,1=b-+1. In particular, if g is almost Kähler, then hBC1,1=b-+1, extending the result by Holt and Zhang (Harmonic forms on the Kodaira–Thurston manifold. arXiv:2001.10962, 2020) for the kernel of Dolbeault Laplacian. We also show that the dimensions of the spaces of Bott–Chern and Dolbeault harmonic (1, 1)-forms behave differently on almost complex 4-manifolds endowed with strictly locally conformally almost Kähler metrics. Finally, we relate some spaces of Bott-Chern harmonic forms to the Bott–Chern cohomology groups for almost complex manifolds, recently introduced in Coelho et al. (Maximally non-integrable almost complex structures: an h-principle and cohomological properties, arXiv:2105.12113, 2021)
Weather derivatives market: the Italian case
No full textThe purpose of this article is to analyse the weather derivatives market and to ascertain if and to what extent a weather market has developed in Italy. The first part of the article provides a general introduction to the weather derivatives market and to weather contracts. This is followed by a description of the most common models used to price weather derivatives. The third and the fourth sections contain the simulation of the pricing of a weather cal
Weather derivatives market: The Italian case
No full textThe purpose of this article is to analyse the weather derivatives market and to ascertain if and to what extent a weather market has developed in Italy. The first part of the article provides a general introduction to the weather derivatives market and to weather contracts. This is followed by a description of the most common models used to price weather derivatives. The third and the fourth sections contain the simulation of the pricing of a weather call. In the third section meteorological data are analysed, while in the fourth the process used to price this contract is explained and the results obtained are reported. An analysis of European and Italian weather derivatives markets is given in section five, with some conclusions being drawn in the final section. © EuroJournals Publishing, Inc. 2012
Bott-Chern harmonic forms on complete Hermitian manifolds
No full textLet (M, J, g,ω) be a Hermitian manifold of complex dimension n. Assume that the torsion of the Chern connection Δ is bounded, and that there exists a C∞exhausting function ρ : M → R such that Δρ,Δ2ρ are bounded. We characterize W1,2 Bott-Chern harmonic forms, extending the usual result that holds on compact Hermitian manifolds. Finally, if (M,J, g,ω) is Kähler complete, ω = dη, with η bounded, and the sectional curvature is bounded, then we get a vanishing theorem for W1,2 Bott-Chern harmonic (p, q)-forms, if p + q ≠= n
ON THE UTILITY OF THE HURST EXPONENT IN PREDICTING FUTURE CRISES
No full textThe aim of this article is to ascertain whether and to what extent the Hurst exponent can be used to forecast future crises. The first and second sections focus on the Hurst exponent, giving theoretical insights and a summary of its uses in finance. The analysis of a dataset of 35 indices and stocks representing various geographical areas and economic sectors is presented in Section 3, while in the last section the conclusion is drawn that in fact the Hurst exponent has, after all, no usefulness in predicting future crises
Aeppli Cohomology and Gauduchon Metrics
No full textLet (M, J, g, ω) be a complete Hermitian manifold of complex dimension n≥ 2. Let 1 ≤ p≤ n- 1 and assume that ωn-p is (∂+ ∂ ̄) -bounded. We prove that, if ψ is an L2 and d-closed (p, 0)-form on M, then ψ= 0. In particular, if M is compact, we derive that if the Aeppli class of ωn-p vanishes, then HBCp,0(M)=0. As a special case, if M admits a Gauduchon metric ω such that the Aeppli class of ωn-1 vanishes, then HBC1,0(M)=0
G. B. Vico nel terzo centenario della nascita, a cura di Pontieri (E.), Galasso (G.), Petruzzelis (N.), Martano (G.), Carbonara (C), Badaloni (N.), Piovani (P.), Pagliaro (Α.), Franchini (R.), Ballucci (Α.)
No full textVan Bever Pierre. G. B. Vico nel terzo centenario della nascita, a cura di Pontieri (E.), Galasso (G.), Petruzzelis (N.), Martano (G.), Carbonara (C), Badaloni (N.), Piovani (P.), Pagliaro (Α.), Franchini (R.), Ballucci (Α.). In: Revue belge de philologie et d'histoire, tome 55, fasc. 3, 1977. Langues et littératures modernes — Moderne taal- en letterkunde. p. 939
Analisi dell’infestazione di Ips typographus nella foresta dell’Alta Val Parma e strategie per la ricomposizione del bosco
No full textAnalysis of the bark beetle outbreak in the forest “Alta Val Parma” (Corniglio, Parma, Italy) and strategies for its regeneration. Norway spruce plantations located in the Foresta Demaniale Alta Val Parma (Corniglio, province of Parma - Italy) experienced since 2004 a massive outbreak of Norway spruce bark beetle (Ips typographus). This outbreak has been triggered by the exceptionally warm and dry summer of 2003. In the following years bark beetle attacks repeated and spread, raising concern about the future of this kind of stands. A survey program has been carried out to help local administration to chose the correct managements strategies. Monitoring of Ips typographus population, carried out between 2007 and 2013, confirmed the presence of two generations per year, with values above the risk threshold in 2007 and just below though very high in 2011. In the affected area, six survey plots have been realized to test different management options with the aim of favoring a fast regeneration of the forest cover. The tested options showed the great difficulty in the establishment of natural generation either for the lack of mother plants in such pure stands or for competition with tall grasses. Sowing brought no significative results, while direct plantation of indigenous broadleaves was more effective, with almost half of the individuals still alive after three years. Our results confirm the great difficulty to rebuild the forest cover after strong ecological disturbances in these artificial forests. Hybrid management strategies and ad hoc silvicultural choices seem to be the only way to manage such kind of situations in a National park, where the priority is biodiversity conservatio
Oltre la perturbazione: la foresta di Lagdei verso un nuovo futuro
No full textStudi, interventi e scelte di gestione dopo le annate siccitose e gli attacchi di bostrico dell’abete ross
Ten years of Ips typographus in Lagdei forest (Province of Parma): outbreak analysis and forest regeneration
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