Rete ITaliana di Approssimazione 

Research ITalian network on Approximation (RITA)

The "Research ITalian network on Approximation (RITA)" groups several italian numerical analysts working on Multivariate Approximation. In this website we collect all research topics and activites of RITA members and institutions.


Statute and guidelines


At the moment the network is among the following institutions and people:

Topics: meshless approximation theory and algorithms; numerical cubature and polynomial approximation; mathematical system modelling from data; high performance computing; multivariate polynomial approximation; kernel-based approximation; mapped bases; barycentric rational approximation; medical image analysis and reconstruction; generalized Bernstein operators; kernel methods and machine learning 

International collaborations: A. M. Acu (University of Sibiu), B. Bauman (Lawrence Livermore National Laboratory), J.-P. Berrut (University of Fribourg), L. Bialas-Ciez (Jagiellonian University Krakow), M. Buhmann (University of Giessen), J.-P. Calvi (Univ. of Toulouse III), K. Hormann (Univ. della Svizzera Italiana), A. Iske (Univ. of Hamburg), A. Kroo (Hungarian Academy of Sciences, Budapest), E. Larsson (University of Uppsala), G. Meurant (CEA), P. Leopardi (Australian Gov. Bureau of Meteorology, Melbourne), N. Levenberg (Indiana Univ., Bloomington), M. Mohammadi (Kharazmi University Teheran), I. Rasa (Technical University Cluj-Napoca), R. Schaback (Univ. of Goettingen), K. Usevich (CNRS, Grenoble), H. Wendland (University of Bayreuth), Y. Xu (Univ. of Oregon, Eugene) 

Visiting 2023: M. Mohammadi (Kharazmi University) 5/1-6/2 2023, A. M. Acu ("Lucian Blaga" University of Sibiu) and I. Rasa (Technical University of Cluj-Napoca) 16-22/1 2023, L. Bialas-Ciez (Jagellonian University of Cracow) 16-24/1 2023

Visiting 2022: A. M. Acu ("Lucian Blaga" University of Sibiu) 19/2-12/3 2022, A. Iske (University of Hamburg) 17-22/12 2022

Visiting 2020: L. Bialas-Ciez (Jagellonian University of Cracow) and M. Baran (Pedagogical University of Cracow) 12-22/2 2020

Visiting 2019: A. Kroo (Hungarian Academy of Sciences, Budapest) 1-30/6 2019, A. P. Peron (University of São Paulo, São Carlos) 14-25/1 2019, L. Plaskota (Univ. of Warsaw) 9-18/1 2019 [phd-course], A. Weinmann (Darmstadt Univ. of Applied Sciences) 13-31/5 2019


Visiting 2018: N. Levenberg (Indiana Univ., Bloomington) 27/4-5/5 2018, M. Slawinski (Memorial University of Newfoundland) 18-22/6 2018


Visiting 2017: A. Kroo (Hungarian Academy of Sciences, Budapest) 8/1-8/4 2017, A. Neisy (Allameh Tabataba'i Univ.) 19/7-22/8 2017,  W. Erb (Univ. of Hawaii, Honolulu) 24-28/7 2017, A. Weinmann (Univ. of Darmstadt) 24-28/7 2017, M. Buhmann (Univ. of Giessen) 30/10-4/11 2017, H. Wendland (Univ. of Bayreuth) 6-27/11 2017 [seminar-abstract]

Topics: polynomial, trigonometric and rational interpolation and approximation; matrix exponential approximation by interpolation

International collaborations: T. Bloom (Univ. of Toronto), J.-P. Calvi (Univ. of Toulouse III), K. Hormann (Univ. of Lugano), N. Levenberg (Indiana Univ., Bloomington), A. Ostermann and S. Rainer (Univ. of Innsbruck), S. Waldron (Univ. of Auckland)

Visiting 2017: A. Ostermann (Univ. of Innsbruck) 24/4-5/5 2017

Topics: meshfree approximation, kernel based methods, approximation theory, wavelets, mathematica signal and image processing 

International collaborations: F. Arandiga and R. Donat (Univ. of Valencia), C. Rabut (INSA Toulouse), T. Sauer (Univ of Passau), R. Schaback (Univ. of Goettingen)

Topics: kernel methods; meshless approximation and applications; approximation theory in medical imaging; adaptive methods for PDEs ; approximation algorithms for biological models; artificial intelligence and machine learning algorithms; traffic models for sustainable mobility; subdivision schemes; design of curves and surfaces; weighted polynomial approximation; numerical methods for integral equations; quadrature formulas; orthogonal polynomials 

International collaborations: S. Demertzis (Cardiocentro Ticino, Lugano), M. Esmaeilbeigi (Malayer Univ.), G.E. Fasshauer (Colorado School of Mines, Golden), A. Guessab (Université de Pau et des Pays de l'Adour), M. Haque (Univ. of Nottingham), K. Hormann (Univ. della Svizzera Italiana), P. Junghanns (Chemnitz University of Technology), E. Larsson (Uppsala Univ.), S. López-Ureña (Univ. de Vaència), H. Malchow (Osnabrueck Univ.), M. Mayr (FH Wiener Neustadt), M.J. McCourt (SigOpt, Inc., San Francisco), G. V. Milovanovic (Serbian Academy of Sciences and Arts), B. Quatember and W. Recheis (Univ. of Innsbruck), J. Stöckler (TU Dortmund),H. Wendland (Univ. of Bayreuth), J. Szabados and P. Vértesi (Alfréd Rényi Institute of Mathematics, Hungarian Academy of Sciences), L. Szili (Lorànd Eötvös University and Budapest University of Technology and Economics)

Visiting 2023: K. Hormann (Università della Svizzera Italiana), M. Marva Ruiz (universidad de Alcalá), A. Guessab (Université de Pau et des Pays de l’Adour) 

Visiting 2022: D. Leviatan (Tel Aviv University), A. Guessab (Université de Pau et des Pays de l'Adour) 14-23/04

Topics: approximation theory; inverse problems; kernels; machine learning; imaging; applications to solar physics 

International collaborations: Prof. G. Hurford (Space Sciences Laboratory, California); Prof. T. Chácon Rebollo, (University of Sevilla, Spain); Prof. J.M. Vega (E.T.S.I. Aeronáuticos, UPM, Madrid, Spain); Prof. M. Azaïez (INP Bordeaux, France); Dr. S. Dutta (US Army, USA); Prof. M. Buhmann, (University of Giessen, Germay)

Topics: kernel methods; surface reconstruction for inverse problems; medical and astronomical imaging 

Topics: geometric modeling; numerical methods for CAGD; refinable functions; subdivision schemes; image analysis and segmentation

International collaborations: G. Albrecht (Univ. of Medellin), N. Dyn (Tel Aviv Univ.), V. Hernandez Mederos and J. Estrada Sarlabous (ICIMAF, Havana), J.-L. Merrien (INSA Toulouse), J. Stockler (TU Dortmund), M. Unser (EPFL Lausanne), J. Yoon (Ewha W. Univ. Seul)

Topics: subdivision,splines, approximation theory, regression analysis 

International collaborations: A. Cuyt (Universiteit Antwerpen), N. Dyn (Tel Aviv Univ.), S. López-Ureña (Univ. de Vaència), J.-L. Merrien (INSA Toulouse), T. Sauer (Univ. of Passau), J. Stockler (TU Dortmund), M. Unser (EPFL Lausanne), J. Yoon (Ewha W. Univ. Seul)

Visiting 2018: D. Labate (Houston Univ.)  15/5-13/6 2018

Visiting 2017: S. Huning (TU Graz) 10/9-24/12 2017, S. Lopez Urena (Univ. of Valencia) 1/10-24/12 2017, J.-L. Merrien (INSA Toulouse) 22-28/1 2017

Topics: numerical methods for PDE; polynomial interpolation and approximation; spectral methods; image analysis; inverse problems; classification and regression problems; Support Vector Machines; numerical methods for integral equations

International collaborations: Y. Li (Liaocheng Univ.), G. Manzini (Los Alamos National Laboratory), S. Pickl (Universität der Bundeswehr München), L. Qiao (Liaocheng Univ.), N. Sorin (Universität der Bundeswehr München)

Topics: approximation by sampling-type operators; neural network operators and their applications; approximation theory in medical imaging; mathematical image processing; signal theory; mathematical methods for civil and energetic engineering; real analysis; functional analysis; operators in Orlicz spaces; self-adjoint operators; direct and inverse spectral theory; water waves; discrete and integral operator; Voronovskaja formula 

International collaborations: T. Acar (Selçuk Univ., Selcuklu), J. Appel (Wuerzburg Univ.), P.L. Butzer and R.L. Stens (Aachen), L. Coroianu (Oradea Univ.), U. Kadak (Gazi Univ.), H. Karsli (Abant Izzet Baysal Universitesi), E. Lyflyand (Bar-llan Univ.), N. Merentes (Universidad Central de Venezuela), J. Musielak (Poznan), S. Reinwand (University of Wurzburg, Germany), G. Schmeisser (Friedrich-Alexander-University of Erlangen-Nürnberg), M. Skopina (S. Petersburg State Univ.), S. Tikhonov (Barcellona), M. A. Valera-Lòpez (Universidad Central de Venezuela) 

Visiting 2018: M. Skopina (S. Petersburg State Univ.) 14-21/1 2018

Visiting 2017: S. Tikhonov (Barcellona), E. Lyflyand (Bar-llan Univ.) 14-20/2 2017

Topics: subdivision schemes; wavelets; mathematical signal processing; fractional differential problems; undetermined inverse problems; multiscale analysis; time-frequency transforms; image processing; information theory; numerical solution of inverse problems; randomized methods; numerical methods for fractional differential problems 

International collaborations: D. Calvetti and F. Somersalo (Case Western Reserve Univ., Cleveland), A. Kokaram (Trinity College, Dublin), B. Piccoli (Rutgers Univ., USA), I. Selesnick (New York Univ.)

Visiting 2019: D. Calvetti and F. Somersalo (Case Western Reserve Univ., Cleveland) 14/1-14/2 2019

Topics: special functions in approximation theory; non-trigonometric Fourier analysis; polynomial and trigonometric approximation; quadrature and cubature formulas; eigenvalues approximation; geometrical models; fractional differential problems; numerical methods for integral equations; approximation algorithms for biological models

International collaborations: P. Agarwal (ANAND, Jaipur, India), N. Cakic (Univ. of Beograd, Serbia),  D. Caratelli (Tomsk Polytechnic Univ., Tomsk, Russia), R. Dmytryshynr (Vasyl Stefanyk Precarpathian National University), J. Gielis (Univ. of Antwerp, Belgium), M.X. He (Nova Southeastern Univ., Ft. Lauderdale, FL, U.S.A.), S. Jimenez (UPM), S. Khan (Aligarh Muslim Univ., India), O. Moaaz (Mansoura University, Egypt), S. Pinelas (Academia Militar, Amadora, Purtugal), H.M. Srivastava (Univ. of Victoria, Canada),  I. Tavkhelidze (Tbilisi State Univ., Georgia), L. Vazquez Martinez (Univ. Complutense), Yamilet Quintana (Univ. Carlos III, Madrid, Spain) 

Visiting 2022: P. Agarwal

Topics: Numerical resolution of inverse problems; splines functions; numerical stability of rational barycentric operators.


International collaboration: K. Hormann (Univ. of Lugano)


Visiting 2020: K. Hormann (Univ. of Lugano) 07/01 2020

Topics: kernel methods; meshless approximation and applications; mathematical signal processing; high performance computing; mutlivariate data analysis; mathematics for AI 


International collaborations: G. Mei (University of Geoscience, Beijing), P. Assari (Bu-Ali Sina University)

Visiting 2019: D. Calvetti and E. Somersalo (Case Western Reserve Univ., Cleveland) 18/05-20/06 2019 [Data-Mining-course]

Visiting 2018: D. Calvetti and E. Somersalo (Case Western Reserve Univ., Cleveland) 02-21/05 2018

Topics: meshless approximation and applications; numerical methods for integral equations; polynomial interpolation and approximation; quadrature and cubature formulas; singular problems; wavelets


International collaborations: F. Filbir (Helmholtz Munich), P. Junghanns (TU Chemitz), M. Van Barel (KU Leuven)


Visiting 2019: F. Filbir (Helmholtz & Technische Universität München) 28/2-9/3 2019 [seminar-abstract-1], [seminar-abstract-2]

Topics: collocation/Runge-Kutta methods for ODEs, FDEs and VIEs; parallel numerical methods; model reduction methods; exponentially fitted methods for oscillatory problems; numerical methods for stochastic VIEs

International collaborations: Z. Jackiewicz (Arizona State Univ.), L.Gr. Ixaru (Institute of Physics and Nuclear Engineering, Bucharest), Ch. Lubich (Univ. of Tuebingen), F. Mohammadi and L. Moradi (Univ. of  Hormozgan, Iran), S. Shahmorad and Y. Talaei (Univ. of Tabriz, Iran)

Visiting 2019: L. Moradi (Univ. of  Hormozgan, Iran) 9/7/2018-5/8/2019 and 27/9-24/10 2019, J. Butcher (Univ. of Auckland, New Zealand) 31/7-4/08 2019, H. Podhaisky (Univ. of Halle, Germany) 22/9-30/9 2019, L. Ixaru (Institute of Physics and Nuclear Engineering, Bucharest, Romania) 17/11-26/11 2019

Visiting 2018: D. Cohen (Umea Univ.) 2-7/2/2018, Z. Jackiewicz (Arizona State Univ.) 8-13/7 2018

Visiting 2017: L.Gr. Ixaru (Institute of Physics and Nuclear Engineering, Bucharest), 14-18/12 2017

Topics: approximation theory, semigroups theory, functional analysis 


International collaborators: T. Acar (Selçuk Univ., Selcuklu), P. Garrancho (Univ. of Jaen), I. Rasa (Technical Univ. of Cluj-Napoca)

Topics: Korovkin approximation theory, evolution problems, semigroup theory

International collaborations: T. Acar (Selçuk Univ., Selcuklu), I. Rasa (Technical Univ. of Cluj-Napoca)

Topics: numerical methods for integral equations; polynomial interpolation and approximation; quadrature rules; approximation of integral transforms; operator theory; singular problems; positive approximation processes; approximation problems for semigroups of operators and evolution equations; numerical treatment of BIE; potential theory applied to several BVPs

International collaborations: T. Acar (Selcuk Univ., Selcuklu), T. Diogo and P. Lima (Instituto Superior Técnico, Lisbon), P. Garrancho (University of Jaén), P. Junghanns (TU Chemnitz), G.V. Milovanovic (Serbian Academy of Sciences, Beograd), I. Rasa (Technical Univ. of Cluj-Napoca), J. Szabados (Hungarian Academy of Sciences, Budapest), M. Stanic and T. Tomovic (University of Kagrujevac) 

Topics: Eco-epidemiological mathematical models, Wastewater bioremediation modelling, Electrical activity and Ca+ dynamics in endocrine cells modelling, Slow/fast bifurcation analysis, Mathematical models applied to cancer, Graph signal processing

Topics: Integral equations, quadrature and cubature formulae, inverse problems 

International collaborations: D. Djukic (University of Belgrade, Serbia), T. Diogo and P. Lima (Instituto Superior Tecnico, Lisbon), R. Mutavdzic (University of Belgrade, Serbia),  L. Reichel (Kent State University, Ohio, US), M. Spalevic (University of Belgrade, Serbia)

Topics: meshless approximation and applications; scattered data approximation; polynomial interpolation; quadrature and cubature formulas; mixed interpolation and regression; bisection-exclusion algorithms; initial and boundary value problems; collocation methods; polynomials and their applications in approximation theory 

International collaborations: W.M. Abd-Elhameed (Cairo University), A. Guessab (Université de Pau et des Pays de l'Adour), K. Hormann (Univ. of Lugano), O. Nouisser (Univ. Ibn Tofail, Kenitra, Marocco)

Visiting 2022: A. Guessab (Université de Pau et des Pays de l'Adour) 

Visiting 2018: T. Sauer (Univ. of Passau) 11/1 2018 [seminar-abstract], B. Zerroudi (Ibn Tofail Univ., Kenitra) 8-20/4 2018

Topics: subdivision schemes; wavelets; frames; mathematical signal processing

International collaborations: M. Charina (Univ. of Wien), M. Holschneider (Univ. of Potsdam), T. Sauer (Univ. of Passau)

Visiting 2019: M. Charina (Univ. of Vienna) and T. Sauer (Univ. of Passau) 9-17/1 2019

Visiting 2018: T. Sauer (Univ. of Passau) 7-13/1 2018

Topics: kernel methods; meshless approximation and applications; wavelet and multiresolution analysis; high performance computing; BVPs; approximation algorithms for biological models; approximation theory; sampling-type operators; frames; image analysis and processing; medical imaging; machine learning  

International collaborations: G.E. Fasshauer (Colorado School of Mines, Golden), F.M. Hilker (Osnabrueck Univ.), M.J. McCourt (SigOpt, Inc., San Francisco), A. Yezzi (Georgia Tech, Atlanta), J.-P. Antoine (UCLouvain, Louvain-la-Neuve), P. Balazs (ÖAW, Vienna), D. Stoeva (University of Vienna, Vienna) 

Visiting 2019: G.E. Fasshauer (Colorado School of Mines, Golden) 12-18/6 2019


Topics: wavelets; mathematical signal processing; image restoration

International collaborations: M. Holschneider (Potsdam Univ.)


RITA abroad