Notiziario Scientifico
Notiziario dei seminari di carattere matematico
a cura del Dipartimento 'G. Castelnuovo'
Sapienza Università di Roma
Settimana dal 20 al 26 febbraio 2017
Lunedì 20 febbraio 2017
Ore 11:00, aula B
Incontro di lavoro su Calcolo delle Variazioni e
Γ-convergenza/Working seminar on Calculus of Variations
and Γ-convergence
Roberto Peirone (Università di Roma Tor Vergata)
A finitely ramified fractal with no self-similar energy
The starting point for many problems in analysis on fractals is the
construction of a self-similar Dirchlet form (a sort of abstract
version of the Dirichlet integral). An old conjecture was that on
every P.C.F. self-similar set (a general class of finitely ramified
fractals) there exists a self-similar Dirichlet form (with good
properties). In this talk, I show a counterexample to that conjecture.
Lunedì 20 febbraio 2017
Ore 14:00, dipartimento di Fisica
seminario delle Meccaniche
Giovanni Gallavotti
Sull'ipotesi ergodica e sui moti caotici
L'ipotesi ergodica di Boltzmann-Maxwell (e Clausius), quale
fondamento della Meccanica Statistica, sarà ridiscussa
insieme alle sue implicazioni sulla teoria statistica del moto
caotico.
Lunedì 20 febbraio 2017
Ore 14:30, aula di Consiglio
seminario di Analisi Matematica
Roberto Natalini (Istituto per le Applicazioni del Calcolo CNR)
Some analytical results on smooth solutions to a semilinear
hyperbolic model of chemotaxis on networks
We consider a semilinear hyperbolic chemotaxis model evolving on a
network. This model is motivated both by the optimization of
tissue-engineering scaffolds used in wound healing and by the movement
of physarum populations in a maze. First we introduce some suitable
transmission conditions at node, which are different with respect to
those used in similar problems. Next, we show the local existence of
smooth solutions, using semigroup techniques. Then we establish the
existence of global (in time) smooth solutions to this problem for
suitably small initial data. The result is obtained by using energy
estimates and the Nishida functional. Finally we will describe some
recent analytical result about the asymptotic behavior of the
solutions and some related numerical simulations. All these results
have been obtained in a series of collaborations with M. Ribot, F, M.
Guarguaglini and G. Bretti.
Martedì 21 febbraio 2017
Ore 14:30, aula E
seminario di Probabilità e Statistica
Wolfgand Woess (TU Graz)
Multidimensional reflected random walk - some results and many questions
Martedì 21 febbraio 2017
Ore 14:30, aula D'Antoni, Università di Roma Tor Vergata
seminario di Equazioni Differenziali
Felix Otto (Max Planck Institut fuer Mathematik, Leipzig)
The thresholding scheme for mean curvature flow and De Giorgi's ideas
for minimizing movements
We consider the thresholding scheme, a practically relevant time
discretization for mean curvature flow (MCF) introduced by
Bence-Merriman-Osher, and prove a (conditional) convergence result in the
multi-phase case. The result establishes convergence towards a weak
formulation in the framework of sets of finite perimeter.
The proof is based on the interpretation of the thresholding scheme as a
minimizing movement scheme, which means that the thresholding scheme
preserves the structure of (multi-phase) mean curvature flow as a gradient
flow w.r.t. the total interfacial energy. More precisely, the
thresholding scheme is a minimizing movement scheme for an energy
functional that Γ-converges to the total interfacial energy (joint
work with Selim Esedoglu).
Our proof is similar in spirit to the convergence result by
Luckhaus-Sturzenhecker of the Almgren-Taylor-Wang scheme, a more academic
minimizing movement scheme for MCF. In particular, ours is a conditional
convergence result, in the sense that we assume that the energy of the
approximation converges to the energy of the limit.
In addition, we appeal to an argument of De Giorgi to show that the limit
also satisfies Brakke's inequality, a way to encode the gradient flow
structure of MCF. De Giorgi's abstract set-up of metric slope and
variational interpolation for minimizing movements, as formulated by
Ambrosio-Gigli-Savare, is taylor-made for this limit.
This is joint work with Tim Laux.
Martedì 21 febbraio 2017
Ore 15:00, aula C
seminario di Modellistica Differenziale Numerica
Vito Trianni (CNR-ISTC)
Decisioni collettive: dove osano gli sciami
La capacità che hanno gli sciami di scegliere collettivamente la migliore opzione tra
una serie di alternative è notevole. In particolare, precedenti studi sulla selezione del sito
di nidificazione delle api hanno descritto dei meccanismi che possono essere impiegati per commutare
in modo adattativo tra scelte deliberate e 'greedy'. Queste ultime scelte sono prese quando il valore
delle alternative disponibili è paragonabile.
In questo seminario passerò in rassegna le prove sui meccanismi auto-organizzati per le scelte
collettive, e introdurrò una metodologia di progettazione per sistemi multi-agente decentralizzati
che garantisce il raggiungimento di proprietà macroscopiche desiderate.
In particolare, presenterò un modello di progettazione per il processo decisionale collettivo che
fornisce le linee guida formali per l'attuazione microscopica delle decisioni collettive al fine di soddisfare
quantitativamente le previsioni macroscopiche. Inoltre, fornirò esempi della metodologia di progettazione
attraverso diversi casi studio che mostrano la fattibilità dell'approccio. I casi di studio coprono modelli
multi-agente astratti e applicazioni in robotica degli sciami e reti di radio cognitive.
Martedì 21 febbraio 2017
Ore 15:30, aula E
seminario di Probabilità e Statistica
Oriane Blondel (CNRS Lyon)
More random walks on random walks
We consider a Poissonian distribution of particles performing independent
simple random walks. Simultaneously, on top of this system, a random walker
evolves with a drift to the right when it is on top of (at least) a particle, to the
left when it is on an empty site. We obtain a LLN, CLT and large deviation
bounds in high and low density. Joint work with Marcelo Hilario, Renato dos Santos,
Vladas Sidoravicius, Augusto Teixeira.
Mercoledì 22 febbraio 2017
Ore 09:20, palazzina E, dipartimento SBAI
GROUPS, PROBABILITY, DYNAMICS: A conference on the occasion of the 50th
birthday of T. Ceccherini-Silberstein
09:20 opening
09:50 R.I.Grigorchuk
11:10 T.Nagnibeda
12:10 M.D'Adderio
14:30 A.Bufetov
15:30 D.D'Angeli
16:30 M.Coornaert
17:30 F.de Giovanni
Mercoledì 22 febbraio 2017
Ore 16:30, aula di Consiglio
seminario di Fisica Matematica
Cristian Giardinà (Università di Modena e Reggio Emilia)
The Ising model on random graphs
Random graphs are useful models for complex networks appearing in empirical studies
of networks. Several structural properties have been identified in this context, including
scale-free and small-world properties.
In this talk I will describe the Ising model on random graphs satisfying these properties.
The Ising model is a stochastic model introduced in statistical physics to model phase
transitions. Thus two sources of randomness are intertwined in the Ising model on
random graphs. I will investigate their interplay studying the Boltzmann-Gibbs measure
for a fixed random graph realization or when the average over graphs (quenched or
annealed) is performed. I shall focus on universality, proving law of large numbers
and central limit theorems in the uniqueness phase, as well as non-classical limit
theorems at criticality.
Mercoledì 22 febbraio 2017
Ore 17:15, aula di Consiglio
seminario di Fisica Matematica
Cédric Bernardin (Université de Nice Sophia-Antipolis)
From diffusion to fractional superdiffusion in a Hamiltonian lattice field model with noise
We consider a Hamiltonian lattice field model perturbed by an energy conserving noise and
show that after a space-time rescaling the energy-energy correlation function is given by the
solution of a skew-fractional heat equation with exponent 3/4. We then investigate the validity
of this result under some deterministic or stochastic perturbations.
Giovedì 23 febbraio 2017
Ore 09:20, palazzina E, dipartimento SBAI
GROUPS, PROBABILITY, DYNAMICS: A conference on the occasion of the 50th
birthday of T. Ceccherini-Silberstein
09:20 E.Rodaro
10:00 A.Georgakopulos
11:10 A.Valette
12:10 F.Radulescu
14:30 E.Frenkel
15:10 K.Schmidt
16:30 M.Cavaleri
17:10 S.Smirnov
Giovedì 23 febbraio 2017
Ore 10:30, aula riunioni (I piano), IAC-CNR, via dei Taurini 19
seminario di Matematica Applicata
Giovanni Ciccotti (IAC, Sapienza università di Roma, UCD Dublin)
How can molecular simulation help the dream of modern engineering?
The talk intend to explain at fundamental level (i) why Molecular Simulations (MS: Molecular
Dynamics, MD, and, generally , Metropolis Monte Carlo, MC, although the talk will concentrate on
MD simulations, the only containing dynamical information) are a rigorous scientific tool and (ii)
how they have been able to produce applicative and practical impact. In particular, in the second
part, it will address the question of how it can help the progress of modern flow engineering by
constructing direct, atomistic, simulation of non-equilibrium hydro-dynamical flows.
In more details, as for the first question, it will explain: (i) where Molecular Dynamics (MD) is from;
(ii) what is it and which complexity it can cope with; (iii) how MD has extended its predictive power
toward predicting the thermodynamic and structural properties of materials and coping with chemical
questions such as chemical reactivity, nucleation, etc (in short, activated processes). As for the second,
the applicative success will be illustrated discussing: (i) how to cope with nucleation phenomena;
(ii) how to avoid the need of constitutive relations in 'ab-initio', atomistic, hydrodynamical calculations.
Giovedì 23 febbraio 2017
Ore 14:30, aula di Consiglio
seminario PdN/P(N)
Luca Battaglia (Sapienza Università di Roma)
Ground state solutions for a nonlinear Choquard equation
I will discuss the existence of groundstate solutions for the Choquard
equation in the whole space RN. I will first consider the case of a
homogeneous nonlinearity F(u) = |u|p, then I will prove the existence
of solutions under general hypotheses. In particular, the cases N=2 and
N≥3 will have to be treated differently. The solutions are found
through a variational mountain pass strategy.
Giovedì 23 febbraio 2017
Ore 14:30, aula 211, Università di Roma Tre,
l.go san L. Murialdo 1
seminario di Geometria
Roberto Volpato (Università di Padova)
K3 surfaces from the point of view of superstrings
I will describe some new theorems and conjectures on K3 surfaces and
their symplectic automorphisms that are motivated by the properties of
physical models arising in string theory.
Venerdì 24 febbraio 2017
Ore 09:20, palazzina E, dipartimento SBAI
GROUPS, PROBABILITY, DYNAMICS: A conference on the occasion of the 50th
birthday of T. Ceccherini-Silberstein
09:20 A.Rosenmann
10:00 E.Manara
11:00 V.Kaimanovich
12:00 W.Woess
Venerdì 24 febbraio 2017
Ore 11:00, aula di Consiglio
discussione Tesi di Dottorato
Sergio Ciamprone (Sapienza Università di Roma)
Certain braided weak Hopf C*-algebras associated to modular categories
Venerdì 24 febbraio 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
Antonio Di Carlo
Percolation and absorption in a (soft) porous matrix
Venerdì 24 febbraio 2017
Ore 16:00, aula Picone
seminario per insegnanti (Piano Lauree Scientifiche)
Ciro Ciliberto (Università di Roma Tor Vergata)
Dalla geometria elementare ai grafi
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