Notiziario Scientifico

Notiziario dei seminari di carattere matematico
a cura del Dipartimento 'G. Castelnuovo'
Sapienza Università di Roma

Settimana dal 5 all'11 giugno 2017


Lunedì 5 giugno 2017
Ore 09:00, Argiletum in Madonna dei Monti,
Numeration2017
09:00 Conference Opening
09:30 A. Kovacs 'Numbers, systems, applications'
10:00 P. Surer 'Substitutions, coding prescriptions and Numeration'
10:30 M. Maggioni 'On the semi-random Luroth map'
11:30 D. Krenn 'k-regular Sequences & Mellin Perron Summation for Analyzing Fluctuations in Pascal's Rhombus'
12:00 V. Aiello and R. Conti 'The Thompson groups, graph polynomials, and knot theory'
14:30 G.H. Choe 'High precision computing for continued fractions and mod 2 normal numbers'
15:00 D. Boka and P. Burcsi 'Limits of families of canonical number systems'
16:00 H. Dlouha and S. Starosta 'An upper bound on prolongation of periods of continued fractions by Mobius transformation'
16:30 C. Sanna 'On the sum of digits of the factorial'


Lunedì 5 giugno 2017
Ore 10:20, aula INdAM
INdAM workshop
DinAmicI V: Modern Trends in the Ergodic Theory of Dynamical Systems
10:20 D. Dolgopyat (University of Maryland) Error in Central Limit Theorem for i.i.d. random variables with atomic distribution
12:00 L. Bunimovich (Georgia Tech, Atlanta) When and where orbits of chaotic systems prefer to go
14:30 A.M. Cherubini (Università del Salento) A study of the stochastic resonance as a periodic random dynamical system
15:30 M. Monge (U.F. Rio de Janeiro) Rigorous computation in random dynamics and computer-aided proof of noise-induced-order
17:00 S. Marmi (Scuola Normale Superiore, Pisa) TBA


Lunedì 5 giugno 2017
Ore 11:00, aula 34 (IV piano), dipartimento di Scienze Statistiche
seminario
Cristina Costantini (Università G. d'Annunzio Chieti-Pescara)
Approssimazione di diffusione di processi a velocità finita
Con processi a velocità finita (a volte detti anche processi di trasporto o evoluzioni aleatorie) intendiamo qui dei modelli, pensati per descrivere il moto di una particella, in cui la posizione della particella a un tempo t è data dall'integrale di un processo velocità, che è costante, o evolve deterministicamente finché, a intervalli di tempo esponenziali, cambia in modo aleatorio. Sulla retta e nel piano, questi processi sono stati approfonditamente studiati (Orsingher, Pinsky, Kolesnik, Stadje e molti altri), in particolare per quanto riguarda l'equazione alle derivate parziali soddisfatta dalla distribuzione a un tempo della posizione e, in alcuni casi importanti, la forma esplicita della distribuzione. Questo seminario tratterà invece del limite, sotto riscalamento spazio-temporale diffusivo, di questi processi, anch'esso studiato da molti autori (Bensoussan, Lions, Papanicolaou, Bal, Degond, Kurtz, Costantini e molti altri). Tale limite può essere ottenuto in dimensione qualunque, per una classe ampia di nuclei di transizione della velocità, anche dipendenti dalla posizione e dalla velocità correnti, e anche nel caso in cui il moto della particella è confinato in una regione e sulla frontiera la velocità cambia in modo deterministico o aleatorio, a seconda della velocità d'impatto trasversale. L'approccio utilizzato è quello delle equazioni differenziali stocastiche e dei problemi di martingala, combinati, nel caso in cui la particella è confinata, con cambiamenti di tempo aleatori.


Lunedì 5 giugno 2017
Ore 11:30, aula conferenze (piano terra), IASI-CNR, via dei Taurini 19
colloquia@iasi
Klaus Truemper (University of Texas at Dallas)
Wittgenstein's Philosophy and the Creation vs. Discovery Question of Mathematics
Over the span of tens of thousands of years, humans have created an elaborate body of theory unequaled in size and complexity: mathematics. There is a profound philosophical question: Where do all the results of this gigantic body of theory come from? Are they already present in some hidden, possibly metaphysical, location and then discovered by inquisitive minds, or are they created in the same way that engineers design various machines for energy conversion, production of goods, or transportation? Over hundreds of years, this question has been answered in various, often diametrically opposed, ways. We examine this question using the approach of the philosopher Ludwig Wittgenstein for the resolution of philosophical problems. With the help of modern brain science, we also look into the strange aspect that eminent researchers arrived at and vigorously defended diametrically opposed answers. Indeed, that amazing process is ongoing today. The talk assumes no prior knowledge in mathematics or philosophy.


Lunedì 5 giugno 2017
Ore 14:00, aula Dal Passo, Università di Roma Tor Vergata
seminario
Elena Pulvirenti (Bonn University)
Metastability for the Widom-Rowlinson model
In this talk I will discuss the Widom-Rowlinson model on a finite two-dimensional box subject to a stochastic dynamics in which particles are randomly created and annihilated inside the box according to an infinite reservoir with a given chemical potential. The particles are viewed as points carrying disks and the energy of a particle configuration is the volume of the union of the disks minus the sum of the volumes of the disks. Consequently, the interaction between the particles is attractive. We are interested in the metastable behaviour of the system at low temperature when the chemical potential is supercritical. In particular, we start with the empty box and are interested in the first time when the box is fully covered by disks. In order to achieve the transition from empty to full, the system needs to create a sufficiently large droplet, called critical droplet, which triggers the crossover. We compute the distribution of the crossover time, identify the size and the shape of the critical droplet, and investigate how the system behaves on its way from empty to full. This is a joint work in progress with F. den Hollander, S. Jansen, R. Kotecky.


Lunedì 5 giugno 2017
Ore 14:30, aula di Consiglio
seminario di Analisi Matematica
Bernardino Sciunzi (Università della Calabria)
Monotonicity and rigidity of solutions to some elliptic systems with uniform limits
I will talk about recent results obtained in collaboration with Alberto Farina and Nicola Soave. We consider the coupled competing Gross-Pitaevskii system (with Λ>0):

-Δu=u-u^3-Λuv^2
-Δv=v-v^3-Λu^2v
u,v> 0

and we prove the validity of the Gibbons' conjecture in the case Λ>1. We also provide Liouville-type theorems in the case Λ∈(0,1].

Lunedì 5 giugno 2017
Ore 14:30, aula Picone
Ninth Summer School in Analysisand Applied Mathematics
14.30 Choksi: Nonlocal geometric variational problems I
16.30 Carrillo: Nonlinear aggregation-diffusion equations: minimizers and long-time asymptotic I


Martedì 6 giugno 2017
Ore 09:00, Argiletum in Madonna dei Monti,
Numeration2017
09:00 S. Akiyama 'Around discretized rotation'
10:00 Z. Masakova and M. Tinkova 'Finiteness in real cubic fields'
11:00 A. Petho 'Nearly linear recursive sequences, especially SRS'
11:30 L.L. Cristea and H. Prodinger 'Order statistics of the values of words with respect to the generalised multinomial measure'
12:00 J. Thuswaldner 'Discrepancy bounds for β-adic Halton sequences'
14:30 I. Dubois 'Algebraic structure and numeration systems for circular words'
15:00 S. Arnone, C. Falcolini, F. Moauro, and M. Siccardi 'A constrained Diophantine equation on symmetric numbers in different bases'
16:00 G. Nagy 'On the structure of periodic elements of simultaneous systems'
16:30 B. Rittaud 'A Numeration System and a Gray Code Given by a Variant of the Tower of Hanoi'
17:00 A.B. Mathis 'Interactions between digits in Fibonacci Numeration'


Martedì 6 giugno 2017
Ore 09:30, aula Picone
Ninth Summer School in Analysisand Applied Mathematics
09.30 Peletier: Mean-field limits in particle systems and Wasserstein gradient flows I
11.30 Carrillo: Nonlinear aggregation-diffusion equations: minimizers and long-time asymptotic II
14.30 Chambolle: Nonlocal and crystalline curvature flows I


Martedì 6 giugno 2017
Ore 09:30, aula INdAM
INdAM workshop
DinAmicI V: Modern Trends in the Ergodic Theory of Dynamical Systems
09:30 C. Ulcigrai (University of Bristol) A CLT for cocycles over rotations
10:30 D. Ravotti (University of Bristol) Quantitative mixing for area-preserving flows on compact surfaces
12:00 S. Luzzatto (ICTP Trieste) Young Towers and SRB measures for (nonuniformly) hyperbolic surface diffeomorphisms
14:30 H.K. Zhang (University of Massachusetts, Amherst) Diffusion for Sinai billiards with flat points
15:30 J. De Simoi (University of Toronto) Spectral rigidity and planar convex billiards
17:00 D. Szasz (Budapest U. of Technology) Equidistribution for standard pairs in planar dispersing billiard flows


Martedì 6 giugno 2017
Ore 14:30, aula Dal Passo, Università di Roma Tor Vergata
seminario
Marcello Lucia (CUNY)
Non-Degeneracy of topological solutions for a Chern-Simons model
We consider a system of PDE arising from a Chern-Simons model involving two Higgs fields. As the coupling constant goes to zero the Higgs fields exhibit two behaviors, which are referred as 'non-topological solutions' and 'topological solutions'. In this talk, the stability of those latter solutions will be discussed.


Martedì 6 giugno 2017
Ore 15:00, aula 1B1, dipartimento SBAI, via A. Scarpa 14
seminario di Geometria
Jerzy Weyman (University of Connecticut)
Quiver representations and their semi-invariants
In this talk I will discuss the basic notions related to quiver representations. A quiver is just a directed graph, its representation is assigning a vector space to each vertex and a linear map to each arrow. One studies the structure of representations of a given quiver. I will discuss Gabriel Theorem which classifies quivers for which there are only finitely many indecomposable representations. In more complicated cases one needs geometric methods, which involves rings of semi-invariants with respect to groups of coordinate changes at each vertex. I will describe some applications including an application to describing tensor product multiplicities of irreducible representations of general linear groups.


Martedì 6 giugno 2017
Ore 15:00, aula B, Università di Roma Tre, via della Vasca Navale 84
colloqui di Fisica
Muscari Giovanni (INGV, Roma)
The Polar Stratosphere: from the Ozone Depletion to Climate Change
During winter and spring, cold temperatures and scarse insolation cause the occurrence of unique physical and chemical phenomena in the polar stratosphere. In the past 30 years, the ozone depletion has been the most observed and studied outcome of these phenomena. However, due to the complexity of the processes that can lead to depletion, the long lifetime of CFCs, the potential impact of a changing climate, and the difficulties in observing the polar stratosphere, there is still work to do before the so called 'ozone hole' can be considered history. In recent years, as the spotlight moved from ozone to climate change, the winter polar stratosphere always proved to be a place where to look for answers. And yet, very few ground stations are equipped with instruments capable of sounding the stratosphere and a large gap in satellite coverage of most polar stratospheric parameters is expected in the near future. This presentation will outline the physics and chemistry behind the ozone depletion, will give an update on its recovery, and will show how the polar stratosphere never ceases to entertain the scientific community.


Mercoledì 7 giugno 2017
Ore 09:00, Argiletum in Madonna dei Monti,
Numeration2017
09:00 K.G. Hare 'Bernoulli convolutions, Garsia entropy and local dimension'
09:30 V. Komornik and D. Kong 'Bases with two expansions'
10:00 N. Langeveld 'A shrinking hole for beta-transformations'
11:00 P. Loreti 'Expansions in non-integer bases in control problems'
11:30 T. Vavra 'Periodic representations in algebraic non-integer base'
12:00 A.C. Lai 'Self-similar manipulators, Fibonacci sequence and number systems'


Mercoledì 7 giugno 2017
Ore 09:30, aula Picone
Ninth Summer School in Analysisand Applied Mathematics
9.30 Carrillo: Nonlinear aggregation-diffusion equations: minimizers and long-time asymptotic III
11.30 Choksi: Nonlocal geometric variational problems, II


Mercoledì 7 giugno 2017
Ore 09:30, aula INdAM
INdAM workshop
DinAmicI V: Modern Trends in the Ergodic Theory of Dynamical Systems
09:30 R. Artuso (Università dell'Insubria) Numerical mixing
10:30 G. Cristadoro (Università di Bologna) About the relationship between symmetry and structure in DNA sequences
12:00 R. Natalini (IAC-CNR, Roma) Large time behavior of evolutionary problems in cell biology


Mercoledì 7 giugno 2017
Ore 10:00, aula riunioni (I piano), IAC-CNR, via dei Taurini 19
seminario di Probabilità
Nicolas Privault (NTU, Singapore)
Probability approximation for functionals of independent random sequences
We derive general Stein distribution bounds between functionals of uniform random variables and the Gaussian and gamma distributions, using multiple stochastic integral expansions combined with derivation and finite difference operators. This approach applies more generally to sums and functionals of continuous and discrete independent random variables, such as U-statistics.


Mercoledì 7 giugno 2017
Ore 15:00, aula di Consiglio
seminario di Algebra e Geometria
Jerzy Weyman (UConn)
Finite free resolutions and Kac-Moody Lie algebras
Let us recall that a format (rn,...,r1) of a free complex F*:0→Fn→Fn-1→...→F0 over a commutative Noetherian ring R is the sequence of ranks ri of the i-th differential di. We will assume that rank(F_i)=ri+ri+1. We say that an acyclic complex Fgen* of a given format over a given ring Rgen is generic if for every complex G* of this format over a Noetherian ring S there exists a homomorphism f:Rgen→S such that G=Fgen×Rgen S. For complexes of length 2 the existence of the generic acyclic complex was established by Hochster and Huneke in the 1980's. It is a normalization of the ring giving a generic complex (two matrices with composition zero and rank conditions). I will discuss the ideas going into the proof of the following result: Associate to a triple of ranks (r3,r2,r1) a triple (p,q,r)=(r3+1, r2-1,r1+1). Associate to (p,q,r) the graph Tp,q,r (three arms of lengths p-1, q-1, r-1 attached to the central vertex). Then there exists a Noetherian generic ring Rgen for this format if and only if Tp,q,r is a Dynkin graph. In other cases one can construct in a uniform way a non-Noetherian generic ring Rgen, which deforms to a ring carrying an action of the Kac-Moody Lie algebra corresponding to the graph Tp,q,r.


Mercoledì 7 giugno 2017
Ore 20:30, aula Magna del Rettorato, Università di Roma Tre, via Ostiense 159
La Fisica incontra la Città
Antonio Di Domenico (Sapienza Università di Roma)
Le particelle strane, entanglement e paradossi quantistici
Il mesone K (o kaone) neutro è una particella elementare ben nota nella fisica nucleare. È dotato di 'stranezza', può oscillare e può rigenerarsi nell'attraversare un materiale prima di decadere disintegrandosi in particelle più leggere. Alcuni di questi decadimenti mostrano uno dei rarissimi esempi di violazione di una simmetria fondamentale della natura, la simmetria CP. Negli acceleratori i kaoni neutri possono essere prodotti in coppie esibendo gli effetti di un caratteristico fenomeno della meccanica quantistica, l'entanglement, con risultati controintuitivi ed apparentemente paradossali. Questa proprietà può essere sfruttata per effettuare dei raffinati test delle simmetrie fondamentali della natura. In questo seminario si illustreranno questi affascinanti fenomeni, le più recenti ricerche condotte su queste tematiche e le prospettive con l'esperimento KLOE-2 attualmente in corso presso i Laboratori Nazionali di Frascati dell'Istituto Nazionale di Fisica Nucleare.


Giovedì 8 giugno 2017
Ore 09:00, Argiletum in Madonna dei Monti,
Numeration2017
09:00 S. Baker 'Digit frequencies and self-affine sets with non-empty interior'
09:30 B. Mance and R. Nikiforov 'Essentially nonnormal numbers for random Cantor series expansions'
10:00 T. Krutki, B. Nemeth and A. Kovacs 'Computing with generalized number systems using the computer algebra system SYGNM'
11:00 P. Hudoba and A. Kovacs 'Examining the number system property with probabilistic algorithms'
11:30 C. Mullner 'Normal Subsequences of Automatic Sequences'
12:00 J.L. Verger-Gaugry 'Totally Real Algebraic Numbers, Bogomolov Property, and Dynamical Zeta Function of the β-shift'
14:30 R. Nikiforov 'On the Hausdorff dimension faithfulness of expansions with infinite alphabet and properties of non-normal numbers'
15:00 R. Nair and E. Nasr 'On Weyl's theorem on Uniform Distribution and Ergodic Theorems'
16:00 F. Caldarola 'Fractals and space-filling curves viewed by a new numerical computation system using infinities and infinitesimals'
16:30 I. Harko 'On relations between systems of numerations and fractal properties of subsets of non-normal numbers'
17:00 P. Drungilas, J. Siurys, J. Jankauskas 'On Littlewood and Newman polynomial multiples of Borwein polynomials'


Giovedì 8 giugno 2017
Ore 09:30, aula INdAM
INdAM workshop
DinAmicI V: Modern Trends in the Ergodic Theory of Dynamical Systems
09:30 N. Frantzikinakis (University of Crete) Ergodicity of the Liouville system implies the Chowla conjecture
10:30 F. Cellarosi (Queen's University, Kingston) Ergodic and statistical properties of B-free numbers
12:00 J.R. Chazottes (Ecole Polytechnique, Palaiseau) Concentration inequalities for dynamical systems
14:30 G. Pinzari (Università di Padova) Recent results on the three-body problem
15:30 M. Gidea (Yeshiva University, New York) Diffusion along chains of normally hyperbolic cylinders


Giovedì 8 giugno 2017
Ore 11:30, aula Picone
Ninth Summer School in Analysisand Applied Mathematics
11.30 Chambolle: Nonlocal and crystalline curvature flows II
14.30 Peletier: Mean-field limits in particle systems and Wasserstein gradient flows II
16.15 Choksi: Nonlocal geometric variational problems III


Giovedì 8 giugno 2017
Ore 14:30, aula 211, Università di Roma Tre, largo san L. Murialdo 1
seminario di Geometria
Giuseppe Pareschi (Università di Roma Tor Vergata)
Cohomological rank functions on abelian varieties: examples and applications
According to recent work of Barja, Pardini and Stoppino, on an abelian variety one can naturally define the ranks of the cohomology groups of a coherent sheaf (or a finite complex of coherent sheaves) twisted with a rational multiple of a polarization. This gives rise to cohomological rank functions defined on the rational numbers, which can be in turn extended to the real numbers. These functions seem to encode interesting geometric informations, as I will try to show by computing some simple examples. Finally, I will show an application to the so-called GV-subvarieties of principally polarized abelian varieties. The main tool is a transformation formula for cohomological rank functions with respect to the Fourier-Mukai equivalence associated to the Poincaré line bundle. This is a report of a joint work in progress with Zhi Jiang (Fudan University, Shanghai).


Venerdì 9 giugno 2017
Ore 09:00, Argiletum in Madonna dei Monti,
Numeration2017
09:00 U. Zannier 'Expansions of quadratic numbers in a p-adic continued fraction'
10:00 M. Weitzer 'An introduction to p-adic systems: A new kind of number system'
11:00 A. Dubickas 'Salem numbers as unusual Mahler measures'
11:30 M. Madritsch 'On multiplicative independent bases for canonical number systems in cyclotomic number fields'
12:00 B. Loridant and S. Zhang 'Topology of a class of p2-crystallographic replication tiles'
12:30 Closing


Venerdì 9 giugno 2017
Ore 09:30, aula Picone
Ninth Summer School in Analysisand Applied Mathematics
09.30 Chambolle: Nonlocal and crystalline curvature flows III
11.30 Peletier: Mean-field limits in particle systems and Wasserstein gradient flows III


Venerdì 9 giugno 2017
Ore 09:30, aula INdAM
INdAM workshop
DinAmicI V: Modern Trends in the Ergodic Theory of Dynamical Systems
09:30 P. Giulietti (Scuola Normale Superiore, Pisa) Infinite mixing for maps with an indifferent fixed point
10:30 S. Senti (U.F. Rio de Janeiro) Thermodynamical Formalism for multidimensional intermittent maps
12:00 Y. Pesin (PennState University) A geometric approach for constructing equilibrium measures in hyperbolic dynamics



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