Random

random@lists.dm.unipi.it

1 participants
5322 discussions

Seminario VAN DER PAS
by Matteo Ruggiero 12 Oct '18

12 Oct '18

STATISTICS SEMINARS @ COLLEGIO CARLO ALBERTO Venerdì 19 Ottobre 2018, alle ore 12:00, presso il nuovo edificio del Collegio Carlo Alberto, in Piazza Arbarello 8, Torino, si terrà il seguente seminario: ------------------------------------------------ Stephanie VAN DER PAS (Leiden University) POSTERIOR CONCENTRATION FOR BAYESIAN REGRESSION TREES AND THEIR ENSEMBLES Since their inception in the 1980's, regression trees have been one of the more widely used nonparametric prediction methods. Tree-structured methods yield a histogram reconstruction of the regression surface, where the bins correspond to terminal nodes of recursive partitioning. Trees are powerful, yet susceptible to overfitting. Strategies against overfitting have traditionally relied on pruning greedily grown trees. The Bayesian framework offers an alternative remedy against overfitting through priors. Roughly speaking, a good prior charges smaller trees where overfitting does not occur. In this paper, we take a step towards understanding why/when do Bayesian trees and their ensembles not overfit. We study the speed at which the posterior concentrates around the true smooth regression function. We propose a spike-and-tree variant of the popular Bayesian CART prior and establish new theoretical results showing that regression trees (and their ensembles) (a) are capable of recovering smooth regression surfaces, achieving optimal rates up to a log factor, (b) can adapt to the unknown level of smoothness and (c) can perform effective dimension reduction. These results provide a piece of missing theoretical evidence explaining why Bayesian trees (and additive variants thereof) have worked so well in practice. ------------------------------------------------ Tutti gli interessati sono invitati a partecipare. Il seminario è organizzato dalla "de Castro" Statistics Initiative (www.carloalberto.org/stats) in collaborazione con il Collegio Carlo Alberto. Cordiali saluti, Matteo Ruggiero --- Matteo Ruggiero University of Torino and Collegio Carlo Alberto www.matteoruggiero.it

1 0

numero speciale di DEF
by Rigo Pietro 10 Oct '18

10 Oct '18

La rivista Decisions in Economics and Finance (Springer) dedica un numero speciale al workshop The Mathematics of Subjective Probability (Milano, settembre 2018) Tutti gli interessati (anche se non hanno partecipato al workshop) sono invitati a sottomettere i loro lavori. La deadline e' 28 febbraio 2019. Ulteriori informazioni nel file allegato. Pietro Rigo

1 0

12th Bayesian nonparametrics workshop
by Fabrizio Leisen 08 Oct '18

08 Oct '18

Dear All, the 12th Bayesian nonparametrics (BNP) meeting will be held in Oxford from the 24th to the 28th of June 2019: http://www.stats.ox.ac.uk/bnp12/ The Bayesian nonparametrics conference is a bi-annual international meeting bringing together leading experts and talented young researchers working on applications and theory of nonparametric Bayesian statistics. It is an official section meeting of the Bayesian Nonparametrics section of the International Society for Bayesian Analysis (ISBA). *****CALL for CONTRIBUTED TALKS**** The Scientific Committee invites submissions for possible contributed talks. The deadline for submitting a title/abstract is 15th December 2018. You can submit your abstract at: https://www.stats.ox.ac.uk/bnp12/index.html#abstract *****Call for TRAVEL SUPPORT***** The submission of applications for travel support opens on 1st October 2018 and closes on 15th December 2018. Currently, there are 35 awards that could be either travel awards or accommodation awards. The support is for junior researchers (students currently enrolled in a Dphil (PhD) programme or having graduated after 1st October 2015). The applicant agrees to present her/his work at the conference as a poster or oral if awarded the travel support. Please see the following link for further details. https://www.stats.ox.ac.uk/bnp12/index.html#travelsupport Best Wishes, Fabrizio Leisen -- Fabrizio Leisen Reader in Statistics Director of the Msc programmes in Statistics School of Mathematics, Statistics and Actuarial Sciences Sibson Building, University of Kent, Canterbury, CT2 7FS https://www.kent.ac.uk/smsas/our-people/profiles/leisen_fabrizio.html http://sites.google.com/site/fabrizioleisen/

1 0

Dottorato in Statistica - Univ. Bocconi (2019-2020)
by Antonio Lijoi 07 Oct '18

07 Oct '18

Cari tutti, con preghiera di diffusione, inoltro l'annuncio relativo al bando (allegato) per l'ammissione al PhD in Statistics presso l'Universita' Bocconi, per l'a.a. 2019-2020. La scadenza per la presentazione delle domande e' l'1 Febbario 2019. Saluti, AL ------------------------------------------------- PhD in Statistics - a.y. 2019-2020 Call for applications for PhD student positions ------------------------------------------------- The Bocconi PhD School provides 4 scholarships for the PhD in Statistics and a position with tuition waiver. * Scholarship amount * 20.280 euro per annum in the 1st and 2nd year 15.343 euro per annum in the 3rd and 4th year Further funding is available through teaching and research assistantship. Visit www.unibocconi.eu/admissionphd for detailed information. ** Applications are due by February 1, 2019. ** Within the Bocconi PhD School, the four-year PhD program in Statistics provides a solid grounding for high level research in Statistics, Probability and Data Science. The curriculum is organized over two years of courses and two years entirely devoted to research. Students gain a deep mathematical and methodological preparation through the first-year. The second-year courses provide students with a more specialized competence and focus on topics that may be the object of the doctoral dissertation. The third and forth years are entirely devoted to research. Both theoretical and applied research, including methods for Machine Learning and Data Science, are supported and pursued. Multidisciplinary interchange with other graduate programs in Bocconi’s PhD School, as well as research experience abroad, are encouraged. Highly qualified and motivated students with M.Sc. degrees in Statistics, Mathematics, Economics, Engineering, as well as other quantitatively-oriented fields, are encouraged to apply for admission. Applicants should hold or be on their way to hold a graduate degree or equivalent. For more information about the PhD program in Statistics at Bocconi, visit www.unibocconi.eu/phdstatistics and feel free to contact: Antonio Lijoi (antonio.lijoi(a)unibocconi.it) Angela Baldassarre, PhD administrative assistant (angela.baldassarre(a)unibocconi.it) -- Antonio Lijoi Bocconi University http://mypage.unibocconi.it/antoniolijoi

1 0

seminar announcement
by Marco Scarsini 05 Oct '18

05 Oct '18

October 11th, 2018, 12:00 *Department of Economics and Finance* *LUISS* Room 207, Viale Romania 32 00196 Roma *Speaker: *Vianney Perchet, École Normale Supérieure, Paris *Title: * *“Dynamic Pricing with Finitely Many Unknown Valuations”* *Abstract:* *“We consider revenue maximization in stochastic dynamic pricing where the distribution of buyers' private values is supported on an unknown set of points of unknown cardinality. This choice of setting is well-suited to model scenarios in which buyers are grouped in an unknown number of latent types, characterized by their private values for the good on sale. We focus on the construction of learning algorithm, using ideas and techniques from multi-armed bandit literature. We will show that if there are only two different possible, but unknown, private values, then the learning cost (called ``regret'') is not bigger than if the values are known (but not the demand at those points).We also consider the case of arbitrarily large number of private values, and show that logarithmic regret is only possible under some specific additional assumptions on the model and we provide such an algorithm.”* The calendar of the future seminars can be found at http://economiaefinanza.luiss.it/en/seminari/prossimi-seminari ******************************************************* Marco Scarsini Dipartimento di Economia e Finanza LUISS Viale Romania 32 00197 Roma, ITALY URL: http://docenti.luiss.it/scarsini/

1 0

Seminario di E. Bisi a Milano - Bicocca (5 ottobre 2018)
by Francesco Caravenna 04 Oct '18

04 Oct '18

Scusandomi per lo scarso preavviso, segnalo il seguente seminario di probabilità che si terrà domani a Milano - Bicocca. Nell'ambito del ciclo "Insalate di matematica", venerdì 5 Ottobre alle ore 13.30 Elia Bisi (University College Dublin) terrà un seminario dal titolo: "How long does it take to go through a sequence of N queues?" nell'aula 3014 del Dipartimento di Matematica e Applicazioni dell'Università di Milano-Bicocca (edificio U5, terzo piano, via Cozzi 55, Milano). Trovate il sommario al seguente indirizzo: https://drive.google.com/file/d/1tcyQ3_hxS7SmifbmQ_ZIZT6YUHa86S-L/view?usp=… Tutti gli interessati sono invitati a partecipare. -- _________________________________________ Francesco Caravenna Dipartimento di Matematica e Applicazioni Università degli Studi di Milano-Bicocca Via Cozzi 55, 20125 Milano, Italy http://www.matapp.unimib.it/~fcaraven/ _________________________________________

1 0

Seminario di Probabilità - Padova
by Paolo Dai Pra 04 Oct '18

04 Oct '18

SEMINARIO DI CALCOLO DELLE PROBABILITA' Ho il piacere di invitarvi al seguente seminario, che si terrà Venerdì 12 Ottobre alle 11:30, nella Sala Riunioni del VII piano della Torre Archimede, in Via Trieste 63, Padova, LUISA ANDREIS (Weierstraß-Institut für Angewandte Analysis und Stochastik - WIAS) Titolo: A large-deviations approach to the multiplicative coagulation process Abstract: At least since the days of Smoluchovski, there is a desire to understand the behaviour of large particle systems that undergo chemical reactions of coagulation type. One of the phenomena that attracts much attention is the question for the existence of a phase transition of gelation type, i.e., the appearance of a particle of macroscopic size in the system. In this talk, we consider the (non-spatial) coagulating model (sometimes called the Marcus-Lushnikov model), starting with N particles with mass one each, where each two particles coagulate after independent exponentially distributed times that depend on a given coagulation kernel, function of the two masses. We focus on the case in which the corresponding coagulation kernel is multiplicative in the two masses, hence the process is identified as the multiplicative coagulation process. This case is of particular interest also for its strong relations with the time dependent Erdös-Rényi random graph. We work for fixed time t > 0 and derive, for the number N of initial particles going to infinity, a joint large-deviations principle for all relevant quantities in the system (microscopic, mesoscopic and macroscopic particle sizes) with an explicit rate function. We deduce laws of large numbers and in particular derive from that the well-known phase transition at time t = 1, the time at which a macroscopic particle (the so-called gel) appears, as well as the Smoluchovski characterisation of the statistics of the finite-sized particles. This is a joint work with Wolfgang König and Robert Patterson (WIAS). Paolo Dai Pra

1 0

RTDA mat/06 presso il Dipartimento di Matematica, La Sapienza.
by Faggionato, Alessandra 04 Oct '18

04 Oct '18

Buongiorno è stato pubblicato sul sito web del Dipartimento e di Ateneo il seguente bando per ricercatore a tempo determinato di tipologia A https://web.uniroma1.it/trasparenza/sites/default/files/bando%20RTD_A%202_2… n. 2_2018 per il conferimento di n. 1 posto da ricercatore a tempo determinato Settore concorsuale 01/A3 SSD: MAT/06 scadenza: 1° novembre 2018 Vi prego di trasmetterne notizia ai possibili interessati Grazie per la collaborazione Saluti Alessandra -- ************************************************* Prof. Alessandra Faggionato http://www1.mat.uniroma1.it/~faggionato/ Department of Mathematics University "La Sapienza" Piazzale Aldo Moro, 5 00185 - Rome Office 5, Phone (0039) 06 49913252 *************************************************

1 0

1year PostDoc position @ Scuola Normale Superiore
by Daniele Tantari 04 Oct '18

04 Oct '18

A call for a one-year postdoc is open at the Scuola Normale Superiore di Pisa (Italy). The topic of the research is *“**Dynamic networks: measure, model and mitigate financial risks”* and it is funded by the Scuola Normale. The details of the call are at - ITA: *https://www.sns.it/bando/assegno-di-ricerca-la-collaborazione-al-programma-di-ricerca-%E2%80%9Creti-dinamiche-il-rischio-finanziario-misure-e-modelli%E2%80%9D <https://www.sns.it/bando/assegno-di-ricerca-la-collaborazione-al-programma-…>* - ENG: *https://en.sns.it/bando/research-contract-part-research-project-%E2%80%9Cdynamic-networks-measure-model-and-mitigate-financial <https://en.sns.it/bando/research-contract-part-research-project-%E2%80%9Cdy…>* The deadline is October 23. I would be grateful if you could forward this message to any potentially interested candidate. Thanks and all the best, Daniele Tantari

1 0

Seminario di Alessandra Caraceni a Roma Tre il 17/10/18
by Pietro Caputo 03 Oct '18

03 Oct '18

Alessandra Caraceni (University of Bath, UK) Titolo: Polynomial mixing time for edge flips on quadrangulations. Mercoledi' 17 Ottobre 2018 ORE 16:00 Dipartimento di Matematica e Fisica Universita' degli Studi Roma Tre Largo San Leonardo Murialdo,1 - Pal.C - Aula 211 Abstract This talk will revolve around recent joint work with Alexandre Stauffer in which we give the first polynomial upper bound for the relaxation time of the edge flip Markov chain on rooted quadrangulations. A quadrangulation of size n is a connected planar graph endowed with a cellular embedding in the sphere such that all of its n faces have degree 4, considered up to orientation-preserving homeomorphisms of the sphere itself; we call it rooted when it is endowed with a distinguished oriented edge. Given a (rooted) quadrangulation of size n, a step of the Markov chain we are interested in a so-called “edge flip” consists in choosing an edge uniformly at random, deleting it and replacing it with one of the three possible edges (two when the original edge is adjacent to only one face) which, if drawn, recreate a quadrangulation. We will see how one can relate the edge flip chain on quadrangulations to a “leaf translation” chain on plane trees (which has a natural interpretation as a chain on the set of Dyck paths, and on other Catalan structures as well). Having discussed how to set up a successful comparison between the two chains which exploits the well-known bijection by Schaeffer and a specific construction of leaf translations as sequences of edge flips, we shall estimate the relaxation time of the leaf translation chain by improving on a result by Movassagh and Shor.

1 0

Jump to page:

2025

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

Random