Notiziario Scientifico
Notiziario dei seminari di carattere matematico
a cura del Dipartimento 'G. Castelnuovo'
Sapienza Università di Roma
Settimana dal 13 al 19 marzo 2017
Lunedì 13 marzo 2017
Ore 14:30, aula di Consiglio
seminario di Equazioni Differenziali
Alessio Porretta (Università di Roma Tor Vergata)
Crescita sopra-naturale in equazioni di Hamilton-Jacobi con diffusione
In questo seminario discuteremo diversi fenomeni indotti nelle equazioni del second'ordine
dalla crescita sopra-quadratica dei termini del prim'ordine, detta anche crescita sopra-naturale.
Il modello discusso è quello di equazioni di Hamilton-Jacobi con diffusione e Hamiltoniana
coerciva a crescita sopra-quadratica, che presentano un regime inedito, a metà strada tra
modelli del primo e del second'ordine. I fenomeni discussi includono: regolarità locale e
globale per soluzioni stazionarie, blow-up e formazione di singolarità per soluzioni evolutive,
perdita (e ritrovamento!) della condizione al bordo.
Lunedì 13 marzo 2017
Ore 16:00, aula di Consiglio
seminario di Probabilità e Statistica Matematica
Yosi Rinott (The Hebrew University and LUISS)
Differential Privacy applied to common methods of dissemination of frequency tables
When official data are to be disseminated to the public, the agency that releases the data must
guarantee the privacy of individuals whose data are to be released.
It is not clear how to define and measure privacy. I will explain a notion developed in computer
science known as Differential Privacy, and my work (with others) on issues that arise in applying it
to the dissemination of frequency tables.
Martedì 14 marzo 2017
Ore 15:30, aula E
seminario di Didattica della Matematica
Nathalie Sinclair (Simon Fraser University, Vancouver)
Geometry: Beyond just naming shapes in primary school
In this talk, I will discuss the experiences I've had working with inservice primary school teachers to
promote the inclusion of more geometry activities in the classroom. I will highlight a few of the main
barriers that I've come across in this work and offer several strategies for further promoting geometry
in the primary school, including the focus on spatial reasoning and the use of technology.
Martedì 14 marzo 2017
Ore 16:30, aula 1103, Università di Roma Tor Vergata
seminario di Analisi Complessa
Feng Rong (Shanghai Jiao Tong University)
On origin-preserving automorphisms of quasi-circular domains
It is known that all origin-preserving automorphisms of quasi-circular domains are
polynomial mappings. By introducing the 'resonance order' and 'quasi-resonance order',
we provide the optimal uniform upper bound for the degree of such mappings.
We will also discuss the problem from the point of view of Bergman representative coordinates.
Mercoledì 15 marzo 2017
Ore 14:00, aula Conversi, dipartimento di Fisica
seminario delle Meccaniche
Valerio Lucarini (University of Reading and University of Hamburg)
Response and Fluctuations in Climate Science
The climate is a complex, chaotic, non-equilibrium system
featuring a limited horizon of predictability, variability on a vast range
of temporal and spatial scales, instabilities resulting into energy
transformations, and mixing and dissipative processes resulting into
entropy production. Despite great progresses, we still do not have a
complete theory of climate dynamics able to encompass instabilities,
equilibration processes, and response to changing parameters of the system(1).
We will outline some applications of the response theory developed by
Ruelle for non-equilibrium statistical mechanical systems, showing how it
allows for setting in a coherent framework concepts like climate
sensitivity and climate response. We show how to predict climate change –
both the global averages and the spatial patterns of climatic fields -
using suitably defined Green functions constructed for comprehensive global
climate models (2). By using the transfer operator formalism in a reduced
space, we also present evidence of the fact that the breakdown of the
Ruelle response is associated to being in the vicinity of climatic critical
transitions (3). We also find evidence in a simple forced and dissipative
atmospheric model of a clear violation of the fluctuation-dissipation
theorem and clarify theoretical reasons and practical relevance of this
result (4). Finally, we address the problem of climate multistability
resulting from the ice-albedo feedback, and find the Melancholia state,
i.e. the edge state sitting in between the two attractors corresponding to
the co-existing warm and snowball climate states. The Melancholia state is
the gate for the noise-inducted transitions between the two stable states.
1. V. Lucarini, R. Blender, C. Herbert, F. Ragone, S. Pascale,
J. Wouters, Mathematical and Physical Ideas for Climate Science, Reviews of
Geophysics (2014)
2. V. Lucarini, F. Lunkeit, F. Ragone, Predicting Climate Change Using
Response Theory: Global Averages and Spatial Patterns, J. Stat. Phys. (2016)
3. A. Tantet, V. Lucarini, F. Lunkeit, H. Dijkstra, Crisis of the Chaotic
Attractor of a Climate Model: A Transfer Operator Approach,
arXiv:1507.02228v1 (2015)
4. A. Gritsun, V. Lucarini, Fluctuations, Response, and Resonances in a
Simple Atmospheric Model, arXiv:1604.04386v2 (2016)
5. V. Lucarini, T. Bodai, Melancholia States in the Clim
Mercoledì 15 marzo 2017
Ore 15:00, aula di Consiglio
seminario di Algebra e Geometria
Bruno Klingler (Jussieu)
Chern's conjecture for special affine manifolds
An affine manifold X (in the sense of differential geometry) is a differentiable manifold
admitting an atlas of charts with value in an affine space with locally constant affine
change of coordinates. Equivalently, it is a manifold admitting a flat torsion free
connection on its tangent bundle. Around 1955 Chern asked if there is any topological
obstruction to the existence of an affine structure on a compact manifold X.
He conjectured that the Euler characteristic e(TX) of any compact affine manifold has
to vanish. I will discuss this conjecture and a proof when X is special affine (i.e. X is
affine and moreover admits a parallel volume form). Surprisingly (or not), the proof
relies on algebraic methods coming from hypercomplex geometry.
Mercoledì 15 marzo 2017
Ore 16:15, aula di Consiglio
seminario congiunto di Fisica Matematica e Geometria
Guo Chuan Thiang (University of Adelaide)
The differential topology of semimetals
The 'Weyl fermion' was discovered in a topological semimetal in 2015. Its mathematical
characterisation turns out to involve deep and subtle results in differential topology. I will
outline this theory, and explain some connections to Euler structures, torsion of manifolds,
and Seiberg-Witten invariants. I also propose interesting generalisations with torsion
topological charges arising from Kervaire semicharacteristics and 'Quaternionic' characteristic classes.
Venerdì 17 marzo 2017
Ore 15:00, Biblioteca - sala Ingegneria Geotecnica, Dipartimento di Ingegneria
Strutturale e Geotecnica (DISG), via Eudossiana 18
Mechanics and Mathematics of (soft) Materials and Structures @ DISG
Giuseppe Tomassetti
Modeling thin plates of polymer gels
Venerdì 17 marzo 2017
Ore 16:00, aula Picone
seminario per insegnanti (Piano Lauree Scientifiche)
Dario Benedetto (Università di Roma Tor Vergata), Claudia Cipriani, Giovanni Armellino,
Patrizia Berneschi, Elena Possamai (Liceo Nomentano)
Esperimenti, dati, metodi
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