177,949 research outputs found
Smoothing semi-smooth stable Godeaux surfaces
No full textWe show that all the semi-smooth stable complex Godeaux surfaces, classified in
[M. Franciosi, R. Pardini and S. Rollenske, Ark. Mat. 56 (2018), no. 2, 299–317], are
smoothable and that the moduli stack is smooth of the expected dimension 8 at the
corresponding points
A footnote to a theorem of Kawamata
No full textKawamata has shown that the quasi-Albanese map of a quasi-projective variety
with log-irregularity equal to the dimension and log-Kodaira dimension 0 is
birational. In this note we show that under these hypotheses the quasi-Albanese
map is proper in codimension 1 as conjectured by Iitaka.Comment: Added an addendum by O. Fujino, M. Mendes Lopes, R. Pardini and S.
Tirabassi that contains an alternative proof of Theorem A in the paper and
explains how to avoid an unsubstantiated claim made in the original proo
Higher-dimensional Clifford-Severi equalities
No full textLet X be a smooth complex projective variety, a: X → A a morphism to an abelian variety such that pic0(A) injects into pic0(X) and let L be a line bundle on X; denote by ha0(X,L) the minimum of h0(X,LS - a-α) for α Pic0(A). The so-called Clifford-Severi inequalities have been proven in [M. A. Barja, Generalized Clifford-Severi inequality and the volume of irregular varieties, Duke Math. J. 164(3) (2015) 541-568; M. A. Barja, R. Pardini and L. Stoppino, Linear systems on irregular varieties, J. Inst. Math. Jussieu (2019) 1-39; doi:10.1017/S1474748019000069]; in particular, for any L there is a lower bound for the volume given by: vol(L) ≥ n!ha0(X,L), and, if KX - L is pseudoeffective, vol(L) ≥ 2n!ha0(X,L). In this paper, we characterize varieties and line bundles for which the above Clifford-Severi inequalities are equalities
'La Meta Sudans ed il compitum. Strutture, apparato decorativo e ipotesi ricostruttiva' [in in ZEGGIO S., PARDINI G., Roma - Meta Sudans. I monumenti. Lo scavo. La storia]
No full textQuesto lavoro è dedicato ai risultati delle indagini svaltesi dal 1986 al 2003 nella Piazza del Colosseo in Roma, nell'area circostante i resti della monumentale fontana di età flavia detta Meta Sudans. Viene dapprima riassunta la complessa sequenza stratigrafico-monumentali, con evidenze che vanno dall'età orientalizzante all'attuale e con monumentistraordinariamente conservati, soprattutto per l'età giulio-claudia. Viene poi analizzato l'eccezionale complesso monumentale rinvenuto al disotto delle fondazioni della fontana flavia. Edificato in età augustea di fronte al probabile santuario delle Curiae Veteres e restaurato in epoca claudia, questo complesso attesta l'esistenza di una precedente Meta Sudans, affiancata da un sacello compitale
Birational geometry of surfaces. Preface
No full textThis volume is an issue of the Bollettino dell’Unione Matematica Italiana connected to the workshop “Birational geometry of surfaces” which took place at the Department of Mathematics of the University of Rome “Tor Vergata”, Italy, in January, 11–15, 2016. We thank the Editors of the Bollettino dell’Unione Matematica Italiana for having accepted to dedicate this issue to this topic.
The workshop was organized by Ciro Ciliberto, Thomas Dedieu, Flaminio Flamini, Rita Pardini with the support of the projects:
Geometria, Algebra e Combinatoria di Spazi di Moduli e Configurazioni—no. PRA-2016-67—of the University of Pisa,
National Research Project (PRIN 2010-11) Geometria delle Varietà Algebriche—no. 2010S47ARA-005—(nodes of Pisa and Roma “Tor Vergata”),
GDRE (CNRS-INdAM) GRIFGA 2012–2015,
Families of subvarieties in complex algebraic varieties; this project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 652782
Appendix: coins catalogue [in Marcello Mogetta – Ilaria Battiloro – Ivan Varriale – Daniel P. Diffendale – Giordano Iacomelli – Mattia D’Acri – Chiara Corbino – Chiara Comegna – Giacomo Pardini . 2022. Archaeological Research at the Sanctuary of Venus in Pompeii: Interim Report of the 2018-2019 Seasons of the Venus Pompeiana Project, FOLD&R Italy: 535, pp. 1-41]
No full textPresentazione dei risultati dello scavo (campagne 2018 e 2019) condotto presso il tempio di Venere a Pompei e diretto dalla Mount Allison University e dall'University of Missouri nell'ambito del Venus Pompeiana Project (VPP
Preface
No full textThis volume collects contributions from speakers at the INdAM Workshop “Birational Geometry and Moduli Spaces”, which was held in Rome on 11–15 June 2018. The workshop was devoted to the interplay between birational geometry and moduli spaces and the contributions of the volume reflect the same idea, focusing on both these areas and their interaction. In particular, the book includes both surveys and original papers on irreducible holomorphic symplectic manifolds, Severi varieties, degenerations of Calabi-Yau varieties, uniruled threefolds, toric Fano threefolds, mirror symmetry, canonical bundle formula, the Lefschetz principle, birational transformations, and deformations of diagrams of algebras. The intention is to disseminate the knowledge of advanced results and key techniques used to solve open problems. The book is intended for all advanced graduate students and researchers interested in the new research frontiers of birational geometry and moduli spaces
Theoretical Performance Bounds on the Estimation of Forest Structure Parameters From Multibaseline SAR Data
No full textGiven their central role in the carbon budget, the SAR remote sensing of forests has become during the last two decades a “hot” research topic. A powerful way to analyze forest scattering consists in the coherent combination of multibaseline (MB) SAR data, possibly also polarimetric. For instance, SAR Tomography is a powerful technique whose natural output is the 3-D imaging in the range-azimuth-height space, thus allowing the resolution of multiple scatterers in height in the same cell. As a consequence, the extraction of a high amount of information is made possible, e.g. forest height and biomass, radar reflectivities, sub-canopy topography, soil humidity, volume extinction [1].
In the last years, many tomographic algorithms have been conceived for the estimation of forest structure parameters in both parametric and non parametric frameworks and their performance have been judged against the available in-situ measurements [2-5]. However, not so many efforts have been spent in the analytical derivation of theoretical performance bounds, despite their primary importance. In fact, such tools provide a benchmark against which it is possible to compare the performance of any estimator. Not only, but they alert to the physical impossibility of finding an estimator whose performance is lower than the bounds.
This work offers a contribution to tackle the performance bounding problem by resorting to the Cramér-Rao bound (CRB) theory. The CRB is a result of the information theory which provides a lower bound on the variance of any unbiased estimator of an unknown parameter. Given also its relative easiness of calculation, the CRB is widely used in the statistical signal processing to judge the efficiency of the parameter estimators. In the specific MB SAR field, it could also be a very useful instrument to characterize the potentials of acquisition configurations and possibly as a guideline in designing acquisition patterns (mission planning) and systems. An interesting extension of the CRB is represented by the Hybrid CRB (HCRB), in which the presence of random phase offsets between different acquisitions (e.g. due to non perfect baseline estimation and/or propagation effects through the atmosphere) can be taken into account.
In particular, in this work the CRB and HCRB derivations are focused to the analysis of forest areas by assuming a two-layer model for the MB data vector, i.e. a ground layer and a canopy layer, with different characteristics of their vertical structure. Starting from the very general formulations of MB bounds in [6] and [7], ready-to-use CRB and HCRB formulas are given for forest scenarios. Moreover, the obtained precision limits on the parameters of interest are calculated numerically for some realistic acquisition patterns and for different observed scenarios. The presence of temporal decorrelation is considered in the model, which is recognized to be one of the main application barriers of MB repeat-pass forest observations, especially from space [8].
References
[1] A. Reigber, A.Moreira, “First Demonstration of Airborne SAR Tomography Using Multibaseline L-Band Data,” IEEE Trans. on Geoscience and Remote Sensing, vol. 38, 2000.
[2] F. Lombardini, M. Pardini, “Experiments of Tomography-Based SAR Techniques with P-Band Polarimetric Data”, Proc. of the 2009 ESA PolInSAR Workshop.
[3] M. Nannini, R. Scheiber, et al., “Estimation of the Minimum Number of Tracks for SAR Tomography,” IEEE Trans. on Geoscience and Remote Sensing, vol. 47, 2009.
[4] M. Neumann, L. Ferro-Famil, et al., “Estimation of Forest Structure, Ground, and Canopy Layer Characteristics From Multibaseline Polarimetric Interferometric Data,” IEEE Trans. on Geoscience and Remote Sensing, vol. 48, 2010.
[5] S. Tebaldini, “Single and Multipolarimetric SAR Tomography of Forested Areas: A Parametric Approach,” IEEE Trans. on Geoscience and Remote Sensing, vol. 48, 2010.
[6] F. Gini, F. Lombardini, M. Montanari, “Layover Solution in Multibaseline SAR Interferometry,” IEEE Trans. on Aerospace and Electronic Systems, vol. 38, 2002.
[7] M. Pardini, F. Lombardini, F. Gini, “The Hybrid Cramér-Rao Bound for Broadside DOA Estimation of Extended Sources in Presence of Array Errors,” IEEE Trans. on Signal Processing, vol. 56, pp. 1726–1730, Apr 2008.
[8] F. Lombardini, F. Cai, M. Pardini, “Parametric Differential SAR Tomography of decorrelating Volume Scatterers,” Proc. of the 2009 European Radar Conference (EURAD)
La moneta di basso conto a Elea/Velia: uso e produzione
No full textPresentazione del progetto di ricerca del DisPaC/Università degli Studi di Salerno sui rinvenimenti monetali di Elea/Velia
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