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Seminario di Antonio Blanca a Roma Tre il 24-10-2019
by Pietro Caputo 15 Oct '19

15 Oct '19

Speaker: Antonio Blanca (Penn State University) Titolo: Lower bounds for testing spin systems Giovedi' 24 Ottobre 2019 ORE 10:00 Dipartimento di Matematica e Fisica Universita' degli Studi Roma Tre Largo San Leonardo Murialdo,1 - Pal.C - Aula 211 Abstract We study the identity testing problem in the context of spin systems where it takes the following form: given the parameter specification of the model M and a sampling oracle for the distribution μ of an unknown model M*, can we efficiently determine if the two models M and M* are the same? We establish hardness results for this problem for two prototypical spin systems: the Ising model and proper colorings. For the ferromagnetic (attractive) Ising model, Daskalakis et al. (2018) presented a polynomial-time algorithm for identity testing. I will present a hardness result for the antiferromagnetic (repulsive) setting. In our proofs, we use random graphs as gadgets; this is inspired by similar constructions in seminal works on the hardness of approximate counting. The results for proper colorings are based on the presumed hardness of #BIS, the problem of (approximately) counting independent sets in bipartite graphs. Based on joint work with Ivona Bezakova, Zongchen Chen, Daniel Stefankovic and Eric Vigoda

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Seminario KOLOKOLTSOV @ UniTo
by Cristina Zucca 14 Oct '19

14 Oct '19

********************************************************************* SEMINARI DI PROBABILITA' E STATISTICA MATEMATICA DIPARTIMENTO DI MATEMATICA "G. PEANO" UNIVERSITA' DEGLI STUDI DI TORINO ********************************************************************* Martedì 17 Aprile 2018 alle ore 15:00 in Aula Marro presso il Dipartimento di Matematica "G. Peano" dell'Università degli Studi di Torino, Via Carlo Alberto 10, Il Prof. *VASSILI KOLOKOLTSOV* terrà un seminario dal titolo *Recent developments in probabilistic and analytic methods for fractional differential equations * Abstract: We shall discuss recent achievements in solving fractional differential equations and their extensions arising from generalized fractional calculus. Probabilistic techniques will be derived from the notion of Markov processes interrupted on the attempt to cross the boundary. Analytic techniques will cover generalized operator-valued Mittag-Leffler functions and chronological Feynman-Kac formulas. Tutti gli interessati sono invitati a partecipare. -- Dr. Cristina Zucca Department of Mathematics University of Torino Via Carlo Alberto 10 10123 Torino, Italy tel: +39-011-6702850 fax: +39-011-6702878

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Announcement -- Half day in Stochastic Analysis and applications (fwd)
by Tiziano Vargiolu 14 Oct '19

14 Oct '19

---------- Forwarded message ---------- Date: Mon, 14 Oct 2019 07:53:54 +0200 From: ancona(a)math.unipd.it To: users(a)math.unipd.it Subject: Announcement -- Half day in Stochastic Analysis and applications Dear Colleagues, it is our great pleasure to announce at our Department the *workshop* *** Half day in Stochastic Analysis and applications *** WHEN: Wednesday 30 October 2019, starting at 10:30 WHERE: Aula 1C150, Torre Archimede, via Trieste 61, Padova *** SCHEDULE: *** 10.30: Terry Lyons (Oxford) 11.05: Franco Flandoli (SNS Pisa) 11.40: Francesco Caravenna (Milano Bicocca) 12.15: Franco Rampazzo (Padova) Please find more details below in attachment. Looking forward to your participation, Fabio Ancona, Paolo Dai Pra, Franco Rampazzo ---------------------------------------------------------------- *** Half day in Stochastic Analysis and applications *** Wed. 30 Oct. 2019, Aula 1C150 Maths Department, via Trieste 63, Padova ---------------- *** Special Guest: TERRY LYONS (Oxford) *** *** Opening the workshop at 10:30 *** ---------------- *** Speaker: FRANCO FLANDOLI (SNS Pisa)*** *** Seminar at 11:05 *** *** Title: Effect of transport noise on PDEs *** *** Abstract *** Linear PDEs of transport type are regularized by the addition of an extra transport term of stochastic type; this is a phenomenon discovered around 2010 and consolidated by different techniques and on different examples. However, the effect on nonlinear PDEs is much less clear. Two results for point vortex solutions and point charge solutions of 2D Euler equations and 1D Vlasov-Poisson equations respectively, indicate that a rich noise has to be considered, opposite to the linear case where a simple space-independent noise suffices to regularize. Some confirmations that such rich noise may have regularizing properties on nonlinear models came for Leray alpha model and dyadic models of turbulence. We now have new insight in the case of 2D Euler equations and 3D Navier-Stokes equations, that will be explained in the talk. The results mentioned above, the classical and the new ones, have been obtained by several authors including Gubinelli, Priola, Barbato, Galeati, Luo and myself. ---------------- *** Speaker: FRANCESCO CARAVENNA (Milano Bicocca) *** *** Seminar at 11:40 *** *** Title: On the two-dimensional KPZ equation *** *** Abstract: *** We consider the Kardar-Parisi-Zhang (KPZ) equation in two space dimensions, driven by space-time white noise. This is a singular PDE which lacks a solution theory, so it is standard to consider a regularized version of the equation and then to investigate the behavior of the solution when the regularization is removed. We first show that the regularized solution undergoes a phase transition, as the noise strength is varied on a logarithmic scale. Then, in the sub-critical regime, we prove convergence (after centering and rescaling) to an explicit well-posed random PDE, the additive Stochastic Heat Equation, with a non-trivial constant on the noise. Based on joint works with Rongfeng Sun and Nikos Zygouras. ---------------- *** Speaker: FRANCO RAMPAZZO (Padova) *** *** Seminar at 12:15 *** *** Title: Limit solutions for control-affine nonlinear systems of ode's *** *** Abstract: *** The aim of this talk, which is fully devoted to deterministic input-output systems, is to present the extremely weak notion of 'limit solution', that might be (or might be not) of interest also for whom is more interested in Stochastic Analysis. For a nonlinear (deterministic) control system with a given initial condition and with a dynamics which is affine in the control variable, a 'limit solution' verifies the following properties: i) it is pointwise defined for an input which is (formally) the derivative of a Lebesgue integrable function; ii) in the commutative case (i.e. when all Lie brackets of the involved vector field vanish identically) the limit solution coincides with the solution one can obtain via a (existing) change of coordinates which makes all vector fields constant; iii) the notion of limit solution subsumes former concepts of solution valid for the generic, non-commutative case. In particular, when the control is the derivative of a bounded variation path, a quite clear relation is established between limit solutions and so-called 'graph completion' solutions.

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Postdoctoral position in Paris - Saclay with Eric Moulines and Nicolas Chopin
by Julyan Arbel 12 Oct '19

12 Oct '19

---------- Forwarded message ---------- From: eric.moulines(a)polytechnique.edu Date: 12 Oct 2019 at 09:33 +0200 To: 'Julyan Arbel' <julyan.arbel(a)inria.fr> Subject: TR: offre de post-doc > As a consequence of its recent funding by the Agence Nationale de la Recherche (ANR), the ABSint research group is recruiting a post-doctoral collaborator for up to 21 months. The accronym ABSint stands for Approximate Bayesian solutions for inference on large datasets and complex models. The project involves researchers in Paris, Saclay, Montpellier, Lyon and Nice. This second call seeks candidates with an excellent research record interested to collaborate more closely with members on the ABSint team located in Saclay, at institutions such as Institut Polytechnique de Paris (e.g. Nicolas Chopin and Eric Moulines), Université Paris Saclay, on any topic (broadly) relevant to ABSint and to these researchers' interests. > Applications can be submitted in either English or French. > The candidate must obtain a PhD degree by the date of application. > Good working knowledge of English is required. > Estimated salary is around 2500 EUR with taxes, depending on experience since PhD. > Position opened December 1, 2019, with possible accommodation for later start. > Call opened until position filled. > Candidates should contact Nicolas Chopin (mail address: nicolas.chopin(a)ensae.fr) with a vita and a motivation letter. Letters of recommendation can also be sent to the same address. >

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Seminario PODOLSKIJ
by Pierpaolo De Blasi 11 Oct '19

11 Oct '19

STATISTICS SEMINARS @ COLLEGIO CARLO ALBERTO Venerdì 18 Ottobre 2019, alle ore 12:00, presso il nuovo edificio del Collegio Carlo Alberto, in Piazza Arbarello 8, Torino, si terrà il seguente seminario: ------------------------------------------------ Mark PODOLSKIJ (Aarhus University) OPTIMAL ESTIMATION OF CERTAIN RANDOM QUANTITIES ASSOCIATED WITH LEVY PROCESSES In this talk we present new ideas on optimality of statistical estimates of certain random quantities of stochastic processes, such as supremum or local times. Despite the existing results on estimation of such objects through high frequency observations, the question of optimality is rarely discussed. We will demonstrate some optimal estimation methods for the supremum and local times of the Brownian motion in the L2 and L1 sense. In the second part of the talk we will investigate how the main ideas can be extended towards the class of Levy processes and continuous diffusion models. (joint work with J. Ivanovs) ------------------------------------------------ Tutti gli interessati sono invitati a partecipare. Il seminario è organizzato dalla "de Castro" Statistics Initiative (www.carloalberto.org/stats <http://www.carloalberto.org/stats>) in collaborazione con il Collegio Carlo Alberto. Cordiali saluti, Pierpaolo De Blasi --- Pierpaolo De Blasi University of Torino & Collegio Carlo Alberto https://sites.google.com/a/carloalberto.org/pdeblasi/

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Fellowships at Heilbronn Institute
by Tiziano De Angelis 10 Oct '19

10 Oct '19

Dear All, The fellowship advertised below might be of interest to people in your network. Best wishes Tiziano Posted on behalf of the Heilbronn Institute: The Heilbronn Institute invites applications for Heilbronn Research Fellowships. We have a number of Fellowships available at Imperial College London, King’s College London, University of Bristol, University College London, University of Manchester. Deadline 17 November 2019. Please see our website for further details: https://heilbronn.ac.uk/fellowships-2/ Heilbronn Research Fellowship: https://www.jobs.ac.uk/job/BVN616/heilbronn-research-fellowship Data Science Heilbronn Research Fellowship: https://www.jobs.ac.uk/job/BVF215/data-science-heilbronn-research-fellowship

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Seminario Enrico Scalas @ UniTo - 15 Ottobre
by Bruno Toaldo 10 Oct '19

10 Oct '19

******************************************************************** SEMINARI DI PROBABILITÀ E STATISTICA MATEMATICA DIPARTIMENTO DI MATEMATICA "G. PEANO" UNIVERSITÀ DEGLI STUDI DI TORINO ********************************************************************* Martedì 15 Ottobre 2019 alle ore 16:30 in Sala S presso il Dipartimento di Matematica "G. Peano" dell'Università degli Studi di Torino, Via Carlo Alberto 10, Il Prof. *Enrico Scalas* (Department of Mathematics – University of Sussex, UK) terrà un seminario dal titolo *Functional and Thermodynamic Limits of a Simple Coagulation-Fragmentation Markov Chain* Abstract: We discuss a simple random exchange model for the distribution of wealth. There are N agents, each one endowed with a fraction of the total wealth; indebtedness is not possible, so wealth fractions are positive random variables. At each step, two agent are randomly selected, their wealths are first merged (coagulation) and then randomly split into two parts (fragmentation) conserving the total wealth. We start from a discrete state space - discrete time version of this model and, under suitable scaling, we present its functional convergence to a continuous space - discrete time model. Then, we discuss how a continuous-time version of the one-point marginal Markov chain functionally converges to a kinetic equation of Boltzmann type. Solutions to this equation are presented and they coincide with the appropriate limits of the invariant measure for the marginal Markov chain. In this way, in this simple case, we complete Boltzmann’s program of deriving kinetic equations from random dynamics. Joint work with: Bertram Duering, Nicos Georgiou, Sara Merino Aceituno Tutti gli interessati sono invitati a partecipare.

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Seminario Jonathan Hermon a Roma Tre il 15-10-2019
by Pietro Caputo 09 Oct '19

09 Oct '19

Martedi' 15 Ottobre 2019 ORE 14:30 Dipartimento di Matematica e Fisica Universita' degli Studi Roma Tre Largo San Leonardo Murialdo,1 - Pal.C - Aula 211 Speaker: Jonathan Hermon Titolo: Anchored expansion in supercritical percolation on nonamenable graphs. Abstract: Let G be a transitive nonamenable graph, and consider supercritical Bernoulli bond percolation on G. We prove that the probability that the origin lies in a finite cluster of size n decays exponentially in n. We deduce that: 1. Every infinite cluster has anchored expansion (a relaxation of having positive Cheeger constant), and so is nonamenable in some weak sense. This answers positively a question of Benjamini, Lyons, and Schramm (1997). 2. Various observables, including the percolation probability and the truncated susceptibility (which was not even known to be finite!) are analytic functions of p throughout the entire supercritical phase. 3. A RW on an infinite cluster returns to the origin at time 2n with probability exp(-Theta(n^{1/3})). Joint work with Tom Hutchcroft.

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Seminar Mealli @Bocconi
by Giacomo Zanella 08 Oct '19

08 Oct '19

We announce the following DEC Statistics seminar: Thursday, October 10 12:30 Meeting room 3-e4-sr03, Bocconi University, Via Roentgen 1, 3rd floor Fabrizia Mealli (University of Florence) Title: Assessing causal effects in the presence of treatment switching through principal stratification Abstract: consider clinical trials focusing on survival outcomes for patients suffering from Acquired Immune Deficiency Syndrome (AIDS)-related illnesses or particularly painful cancers in advanced stages. These trials often allow patients in the control arm to switch to the treatment arm if their physical conditions are worse than certain tolerance levels. The Intention-To-Treat analysis compares groups formed by randomization regardless of the treatment actually received. Although it provides valid causal estimates of the effect of assignment, it does not measure the effect of the actual receipt of the treatment and ignores the information of treatment switching in the control group. Other existing methods propose to reconstruct the outcome a unit would have had if s/he had not switched. But these methods usually rely on strong assumptions, for example, there exists no relation between patient's prognosis and switching behavior, or the treatment effect is constant. Clearly, the switching status of the units in the control group contains important post-treatment information, which is useful to characterize the treatment effect heterogeneity. We propose to re-define the problem of treatment switching using principal stratification and introduce new causal estimands, principal causal effects for patients belonging to subpopulations defined by the switching behavior under control. For statistical inference, we use a Bayesian approach to take into account that (i) switching happens in continuous time generating infinitely many principal strata; (ii) switching time is not defined for units who never switch in a particular experiment; and (iii) survival time and switching time are subject to censoring. We illustrate our framework using a synthetic dataset based on the Concorde study, a randomized controlled trial aimed to assess causal effects on time to-disease progression or death of immediate versus deferred treatment with zidovudine among patients with asymptomatic HIV infection. Joint work with Alessandra Mattei and Peng Ding Kind regards, Giacomo Zanella The DEC statistics seminars schedule is available at http://www.unibocconi.eu/statseminar Please note: if you are a guest and you do not have a Bocconi ID Card to access to the Bocconi Buildings, please communicate your participation by sending an email to arianna.colombo(a)unibocconi.it

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2-year Teaching Fellow in Statistics at the University of Leeds
by Tiziano De Angelis 07 Oct '19

07 Oct '19

Dear All, We have an opening for a Teaching Fellow in Statistics at the University of Leeds. The position is fixed term for 2 years. Please see the advert below https://www.timeshighereducation.com/unijobs/minisites/university-of-leeds/… I would be most grateful if you could please circulate the advert to any potential candidate. Best wishes Tiziano

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