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1 == Colloquium of the Department of Mathematics and Statistics ==
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3 [[List of held colloquiums>>doc:mathstat.Ajankohtaista.Colloquium of the Department of Mathematics and Statistics.List of colloquiums.WebHome]]
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5 Starting on January 28, 2009, a Colloquium of the Department of Mathematics and Statistics will convene once a month during the semesters. The Colloquium will convene on the last Wednesday of each month from 16:15 to 17:00.
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7 Each colloquium talk will be given in English by a distinguished mathematician/statistician/computer scientist either from our own department or by a guest.
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12 Department Colloquium
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14 Wednesday, April 17, 2019 in the Auditorium CK112 at 4.15pm.
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16 Speaker: University lecturer Ritva Hurri-Syrjänen
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18 University of Helsinki
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20 Title: On Sobolev-type inequalities and beyond
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25 Department Colloquium
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27 Wednesday, December 19, 2018 in the Auditorium CK112 at 4.15 PM.
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29 Speaker: Associate Professor Jani Virtanen
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31 University of Reading
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33 Title: Toeplitz determinants and their applications in mathematical physics
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41 Department Colloquium
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43 Wednesday, November 28, 2018 in the Auditorium CK112 at 4.15 PM.
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45 Speaker: Professor Agnieszka Kalamajska
46 University of Warsaw and Polish Academy of Sciences
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48 Title: Strongly nonlinear multiplicative inequalities
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55 Department Colloquium
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57 Wednesday, October 31, 2018 in the Exactum Auditorium CK 112at 4.15 PM.
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59 Speaker: Lecturer Tuomas Sahlsten
60 University of Manchester
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62 Title: How to find a criminal from a city of millions?
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69 Department Colloquium
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71 === Wednesday, September 26, 2018 at 4.15 PM in the Exactum Auditorium CK 112. ===
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73 Speaker: Senior Lecturer Petteri Harjulehto
74 \\ University of Turku
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76 Title: Generalized Orlicz spaces and related variational problems
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83 The fourth and last Departmental Colloquium (laitoskollokvio) of the fall term
84 will take place on
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86 === Wednesday, December 14, in the Auditorium CK112 at 4.15 PM. ===
87
88 Speaker:
89 University Lecturer Jari Taskinen
90 University of Helsinki
91
92 WHEELTAPPERS, COMPACT SETS AND SOBOLEV EMBEDDINGS
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94 Abstract:
95 In linear algebra we learn that given a self-adjoint nxn-matrix
96 A one can find an orthonormal basis of the n-dimensional Euclidean space,
97 which consists of eigenvectors of A. The concepts of eigenvalues and
98 eigenvectors generalize to spectral theory of linear operators in Hilbert
99 spaces. Two reasons make this a fundamental object of study. First, it is
100 a beautiful, nontrivial abstract mathematical theory. Second, very many
101 linearized physical models are based on it. In particular the propagation
102 of acoustic (or many other types of) waves in a given domain \Omega
103 depends on the spectral problem for the underlying elliptic partial
104 differential equation (PDE).
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106 The functional analytic approach to elliptic PDE's involves Sobolev-Hilbert
107 spaces and Sobolev embedding theorems. We sketch this classical approach
108 and review recent research (jointly with S.A. Nazarov), emphasizing the
109 interesting phenomena created by geometrically nontrivial domains \Omega.
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111 As is already a custom, after the talk there will be wine, pizza,
112 and beverages available. Everyone is warmly welcome!
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130 The third Departmental Colloquium (laitoskollokvio) of the fall term will take place on
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132 === Wednesday, November 30, in the Auditorium CK112 at 4.15 PM. ===
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134 Speaker:
135 Professor Mika Seppälä, Helsinki
136 University of Helsinki and Florida State University
137
138 Algebraic Curves, Riemann Surfaces, and their Jacobians
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140 Abstract:
141 Compact Riemann surfaces, projective algebraic curves, and their Jacobian varieties are different views of the same object. Classical methods make this result explicit in the case of genus one Riemann surfaces. To find a method to pass numerically from a given Riemann surface to a representation of the same object as an algebraic curve, and then to compute approximations of its Jacobian, is a difficult open problem in the general case. The main obstacle here is Hilbert’s 22nd problem, the problem of numerical uniformization. This can be solved in the case of hyper-elliptic algebraic curves using a method of P. J. Myrberg.
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143 As is already a custom, after the talk there will be wine, pizza,
144 and beverages available. Everyone is warmly welcome!
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172 The second Departmental Colloquium (laitoskollokvio) of the fall term will take place on
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174 === Wednesday, October 26, in the Auditorium A111 at 4.15 PM. ===
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176 Speaker: Professor Gunther Uhlmann
177 University of Washington (Seattle)
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179 Title and abstract will be given later.
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214 The first Departmental Colloquium (laitoskollokvio) of the fall term will take place on
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216 === Wednesday, September 28, in the Auditorium CK112 at 4.15 PM. ===
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218 Speaker: Professor Tom Körner
219 Cambridge University
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221 Title: Why is Analysis 101 so hard?
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223 As is already a custom, after the talk there will be wine, pizza,
224 and beverages available. Everyone is warmly welcome!
225
226 The abstract of the talk is below.
227
228 Best regards, Pertti Mattila
229
230 Abstract:
231
232 It is very hard to prove things that we know are true.
233 By studying analysis over the rationals rather than the
234 reals it becomes clear that the things we think are necessarily
235 true are not. I shall give simple examples, known to
236 all professionals, and a couple of examples which
237 may be less known.
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261 The Departmental Colloquium (laitoskollokvio) of May will take place on
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263 === Wednesday, May 25, in the Auditorium CK112 at 4.15 PM. ===
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265 Speaker: Professor Gaven J. Martin
266 Massey University, New Zealand
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268 Title: Quasiregular Mappings, Curvature & Dynamics.
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270 As is already a custom, after the talk there will be wine, pizza, and beverages available. Everyone is warmly welcome!
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272 The abstract of the talk is below.
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274 Best regards, Matti Lassas
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276 Abstract:
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278 We survey recent developments in the area of geometric function theory and nonlinear analysis and in particular those that pertain to recent developments linking these areas to dynamics and rigidity theory in higher dimensions. A self mapping of an n-manifold is rational or uniformly quasiregular if it preserves some bounded measurable conformal structure. Because of Rickman's version of Montel's theorem there is a close analogy between the dynamics of rational mappings of closed manifolds and the classical Fatou-Julia theory of iteration of rational mappings of the complex plane. The theory is particularly interesting on the Riemann n-sphere where many classical results find their analogue. We also present recent results toward classifying manifolds admitting rational maps.
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280 **The talk has a broad mix of different mathematics and is intended for a general audience.**
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308 The Departmental Colloquium (laitoskollokvio) of April will take place on
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310 === Wednesday, April 27, in the Auditorium CK112 at 4.15 PM. ===
311
312 Speaker: Professor Pentti Saikkonen, University of Helsinki
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314 Title: Parameter Estimation in Nonlinear Autoregressive Models with Generalized Autoregressive Conditional Heteroskedasticity.
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316 As is already a custom, after the talk there will be wine, pizza, and beverages available. Everyone is warmly welcome!
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318 The abstract of the talk is below.
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320 Best regards, Matti Lassas
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322 Abstract: Parameter estimation in nonlinear autoregressive (AR) models with the conditional variance specified as a general nonlinear first order generalized autoregressive conditional heteroskedasticity (GARCH(1,1)) model is discussed. Such models are widely used to analyze financial time series in fields such as economics, finance, and insurance. The focus of the talk is in some special issues encountered in establishing strong consistency and asymptotic normality of the Gaussian quasi maximum likelihood (QML) estimator.
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347 The Departmental Colloquium (laitoskollokvio) of March will take place on
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349 === Wednesday, March 30, in the Auditorium CK112 at 4.15 PM. ===
350
351 Speaker: Professor Kari Astala
352 University of Helsinki
353
354 Title: Holomorphic motions
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356 As is already a custom, after the talk there will be wine, pizza,
357 and beverages available. Everyone is warmly welcome!
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359 The abstract of the talk is below.
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361 Best regards, Matti Lassas
362
363 Abstract:
364
365 What happens when the space is deformed so that the time-dependence is complex analytic
366 (holomorphic) ? Briefly: What if time is holomorphic ?
367
368 Such questions arise in complex dynamics, Kleinian groups and geometric analysis, giving
369 rise to the notion of holomorphic motions. These then give, for instance,
370 a natural explanation of the geometric stability in dynamical systems.
371 We review first few of the surprising properties of holomorphic motions and their
372 relations to analysis and geometry.
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389 The Departmental Colloquium (laitoskollokvio) of February will take place on
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391 === Wednesday, February 23, in the Auditorium CK112 at 4.15 PM. ===
392
393 Speaker: Professor Jouko Väänänen
394 University of Helsinki
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396 Title: Logic and set theory
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398 As is already a custom, after the talk there will be wine, pizza,
399 and beverages available. Everyone is warmly welcome!
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401 The abstract of the talk is below.
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403 Best regards, Matti Lassas
404
405 Abstract:
406
407 Abstract: I will give a quick glimpse of mathematical logic from the vantage point of set theoretic model theory, focusing on two particular problems, one related to generalized quantifiers and another related to infinitary logic.
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421 The first Departmental Colloquium (laitoskollokvio) of the spring term will take place on
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423 === Wednesday, January 26, in the Auditorium CK112 at 4.15 PM. ===
424
425 Speaker: Professor Peter Lindqvist
426 Norwegian University of Science and Technology, Trondheim
427
428 Title: The Infinity-Laplace Equation
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430 As is already a custom, after the talk there will be wine, pizza,
431 and beverages available. Everyone is warmly welcome!
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433 The abstract of the talk is below.
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435 Best regards, Matti Lassas
436
437 Abstract:
438
439 The Infinity-Laplace Equation is akin to the ubiquitous Laplace Equation and it has been intensively studied during the last 15 years. This "fully non-linear equation" has connexions to several branches of mathematics: calculus of variations, partial differential equations, probability theory [[image:https://wiki.helsinki.fi/s/en_GB/7701/88819522251e178b5cc83bc1e3ddc18a884c1aed/_/images/icons/emoticons/warning.svg||title="(warning)" border="0" class="emoticon emoticon-warning"]] , image processing, and so on.
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441 Its solutions, the infinity-harmonic functions, provide the optimal Lipschitz-extension of the boundary values. The modern concept of viscosity solutions, originally created for first order equations by Lions, Evans, Ishii, Jensen, and others, plays a central role. ~-~-The connexion to game theory is spectacular, a game ("Tug-of-War") replacing the Brownian motion.
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443 The talk is about this fascinating equation, once called "the Last Great Scalar Equation" by Evans.
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471 The last Departmental Colloquium (laitoskollokvio) of the fall term will take place
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473 === Wednesday, December 15, in the Auditorium CK112 at 4.15 PM. ===
474
475 Speaker: Professor Kari Vilonen (Northwestern University)
476
477 Title: The microlocal codimension three conjecture
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479 Abstract below.
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481 As is already a custom, after the talk there will be wine, pizza and beverages available! ... and don't forget that the chairman (MG) of the department wants everyone to be present.
482
483 Jouko Väänänen
484 Czar of the Colloquium
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486 Abstract:
487
488 According to an old well-established principle, special functions (or distributions) can be understood and analyzed in terms of the systems of differential equations that they satisfy. To this end, a general theory of systems of linear (micro) differential equations was developed by the Sato school in Kyoto. This point of view, in its various incarnations, is now ubiquitous in many parts of mathematics allowing functions to be replaced by geometric objects. In joint work with Kashiwara we have proved the main longstanding conjecture in this subject, the codimension three conjecture. I will explain this conjecture and some of the very general ideas which enter the proof.
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506 The next Departmental Colloquium (laitoskollokvio) of the fall term will take place
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508 === Wednesday, November 24, in the Auditorium CK112 at 4.15 PM. ===
509
510 Speaker: Professor Antti Kupiainen.
511
512 Title: Renormalization - from Magic to Mathematics.
513
514 Abstract below.
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516 As is already a custom, after the talk there will be wine, pizza and beverages available! ... and don't forget that the chairman (MG) of the department wants everyone to be present.
517
518 Jouko Väänänen
519 Czar of the Colloquium
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521 Abstract:
522 Renormalization Group emerged half a century ago to deal with the problem of divergencies physicists encountered when trying to do calculations in Quantum Electrodynamics. Subsequently it developed into a powerful tool to deal with multi scale problems both in physics and mathematics.
523 We review these developments and explain some more recent applications of Renormalization Group to probability.
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537 The next Departmental Colloquium (laitoskollokvio) of the fall term will take place
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539 === Wednesday, October 27, in the Auditorium CK112 at 4.15 PM. ===
540
541 The speaker is Professor Michael Lacey (Georgia Institute of Technology).
542
543 Title: Pointwise Convergence of Fourier Series: Past, Present and Future.
544
545 Abstract below.
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547 As is already a custom, after the talk there will be wine, pizza and beverages available! ... and don't forget that the chairman (MG) of the department wants everyone to be present.
548
549 Jouko Väänänen
550 Czar of the Colloquium
551
552 Abstract:
553
554 We recall Lennart Carleson's Theorem asserting the pointwise convergence of partial summation of Fourier series of square integrable functions. We explain what the Theorem says, and why it is worthy of citation by the Abel Prize committee: It is a "multi-scale" theorem. The talk finishes with related results that suggest possibilities for 'non-commutative' variants of Carleson's Theorem.
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564 The next Departmental Colloquium (laitoskollokvio) of the fall term will take place at the expected time:
565
566 === Wednesday, September 29, in the Auditorium CK112 at 4.15 PM. ===
567
568 The speaker is Professor Jukka Corander.
569
570 Title: Have I Seen You Before? Principles of predictive classification revisited.
571
572 Abstract below.
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574 As is already the custom, after the talk there will be wine, pizza and beverages available! ... and don't forget that the chairman (MG) of the department wants everyone to be present.
575
576 Jouko Väänänen
577 Czar of the Colloquium
578
579 Abstract: Classification of objects into a finite set of alternative classes based on observed features of the objects is a common task in statistical machine learning. An important application example familiar to most of us is spam filtering of email messages. In this talk we review the probabilistic basis of generative classification and show how a particular inductive rule of classification arises from basic principles of predictive probabilistic modeling pioneered by Seymour Geisser in 1960's. The standard practice of classifying objects one by one, which follows from an i.i.d. assumption, is demonstrated to be at odds with laws of predictive probability and we show also that it can be motivated as an asymptotic approximation to a more coherent rule. A novel inductive principle of predictive classification is introduced and we discuss its properties in relation to other principles.
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593 The first Departmental Colloquium (laitoskollokvio) of the fall term will take place
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595 === Wednesday, September 15, in the Auditorium CK112 at 4.15 PM. ===
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597 The speaker is Professor Menachem Magidor (Hebrew University, Jerusalem).
598
599 Title: Some reflections on the Continuum Hypothesis.
600
601 Abstract below.
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603 As is already a custom, after the talk there will be wine, pizza and beverages available! ... and don't forget that the chairman (MG) of the department wants everyone to be present.
604
605 Jouko Väänänen
606 Czar of the Colloquium
607
608 Abstract:
609
610 The continuum problem is the problem of determining whether the cardinality of the real line is the immediate successor of the cardinality of the integers or there is a set of reals whose cardinality is strictly between the cardinality of the integers and the reals. The Continuum Problem was the first problem on Hilbert’s famous list. The problem turned out to be undecidable by the usual axiom systems for Set Theory. The results of Gödel and Cohen tell us that the axioms give very little information about the relative size of the set of integers and the set of reals. Gödel’s conjecture that strong axioms of infinity will settle the problem turned out to be false. Is this the end of the story?
611 In this talk we shall survey some of the current approaches of trying to give a meaningful answer to the problem, in spite of its independence. Two direction of research we shall concentrate on will be forcing axioms and the theory of universally Baire sets of reals.
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621 The fourth colloquium of the spring term will take place
622
623 === Wednesday, April 28, in the Auditorium CK112 at 4.15 PM. ===
624
625 The speaker is: Professor Eero Saksman
626
627 Title: On random geometry
628
629 Abstract: An emerging new field, vaguely called 'Random Geometry', is described through some examples. The case of random conformal welding
630 is considered in more detail.
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632 As is already a custom, after the talk there will be wine, pizza and beverages available!
633 ... and don't forget that the chairman (MG) of the department wants everyone to be
634 present.
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641 The third colloquium of the spring term will take place
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643 === Wednesday, March 31, in the Auditorium CK112 at 4.15 PM. ===
644
645 The speaker is: Professor Jean Bricmont (Université catholique de Louvain)
646
647 Title: From the microscopic to the macroscopic world.
648
649 Abstract: Basic physics studies microscopic equations, i.e. Newton's or Schödinger's
650 equations. But another part of physics, as well as most applications, deals with
651 macroscopic equations, such as the heat, Navier-Stokes or Boltzmann equations. Are the
652 latter independent of the microscopic equations? Are they rather a consequence of them?
653 Does the derivation of the macroscopic equations from the microscopic ones involve some
654 new principle? Part of the problem is that the microscopic equations describe the world
655 in the same way whether we go from past to future or from future to past, while the
656 macroscopic equations do not: they are compatible with the increase of entropy (or the
657 second law of thermodynamics) and have therefore an intrinsic time direction.
658
659 The goal of the talk will be to sketch an answer to those questions for a mathematical
660 audience.
661
662 As is already a custom, after the talk there will be wine, pizza and beverages available!
663 ... and don't forget that the chairman (MG) of the department wants everyone to be
664 present.
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671 The second colloquium of the spring term will take place
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673 === Wednesday, February 24, in the Auditorium CK112 at 4.15 PM. ===
674
675 The speaker is:
676 Professor Karen Smith (University of Michigan + University of Jyväskylä)
677 Title: "Thresholds of Singularities."
678 Abstract:
679 Consider a polynomial function f on complex N space. We say that f is singular at a point if its gradient vanishes there. But how can we quantify how singular? I will present three different ways of trying to quantify or measure the singularities of a polynomial or analytic function. The most classical involves using integration to measure how fast the reciprocal approaches infinity at the singular points. Or using algebraic geometry, we can measure the singularities in terms of the complicatedness of a "resolution of singularities". Finally, we can also "reduce mod p" and study the behavior of f under the Frobenius (or p-th power) map. Amazingly, all these different ways of measuring singularities turn out to be more or less equivalent, and I hope to hint at why.
680
681 As is already a custom, after the talk there will be wine, pizza and
682 beverages available! ... and don't forget that the chairman (MG) of
683 the department wants everyone to be present.
684
685 Yours Sincerely,
686
687 Kari Astala
688 Czar of the Colloquium
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695 The first colloquium of the spring term will take place
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697 === Wednesday January 27, in the Auditorium CK112 at 4.15 PM. ===
698
699 The speaker is:
700 Professor Juha Kinnunen (Helsinki University of Technology - Aalto University)
701
702 Title: On a theorem of Beckenbach and Rado for subharmonic functions.
703
704 Abstract: Beckenbach and Rado characterized logarithmically subharmonic functions in the plane in terms of integral inequalities involving spherical averages. We extend this result to higher dimensions and thus answer a question raised by Beckenbach and Rado. We also consider related integral inequalities suggested by Beckenbach and Rado and discuss connections to Muckenhoupt's weights.
705
706 As is already a custom, after the talk there will be wine, pizza and beverages available! ... and don't forget that the chairman (MG) of
707 the department wants everyone to be present.
708 Yours Sincerely,
709
710 Kari Astala
711 Czar of the Colloquium
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718 The colloquium in December will take place
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720 === Wednesday, December 9:th, 2009, in the Auditorium CK112 at 4.15 PM. ===
721
722 The speaker is UNIVERSITY LECTURER TAPANI HYTTINEN, and he will give a talk on
723
724 FINDING FIELDS
725
726 ==== Abstract ====
727
728 Suppose a (large) blackboard is equipped with tools that allow one to draw a line
729 through any given two distinct points, draw the common point of any two intersecting lines
730 and draw a line which contains a given point and is parallel with a given line.
731 Then given three distinct points, call them 0, 1 and I, which are not collinear,
732 it is elementary to construct using these tools an addition and a multiplication to the
733 set of points of the line containing 0 and 1 so that it becomes isomorphic with the field of real numbers. In the talk I will look at variations of this construction,
734 some old and some more recent.
735
736 As is already a custom, after the talk there will be wine, pizza and beverages available! ... and don't forget that the chairman of the department wants everyone to be present.
737 {{/panel}}
738
739 === Previous colloquia ===
740
741 {{panel borderColor="#8C8A87" bgColor="#eeeeee" borderStyle="solid"}}
742 === Wednesday, November 25, 2009, in the Auditorium CK112 at 4.15 PM. ===
743
744 The speaker is PROFESSOR MAARIT JÄRVENPÄÄ, and he will give a talk on
745
746 HOW TO TURN A NEEDLE?
747
748 ==== Abstract ====
749
750 In 1917 S. Kakeya asked the following question nowadays known as the Kakeya needle problem: what is the least amount of
751 area required to rotate continuously a unit line segment in the plane by a full rotation? I discuss the history and some
752 recent developments related to this problem.
753
754 As is already a custom, after the talk there will be wine, pizza and beverages available! ... and don't forget that the chairman of the department wants everyone to be present.
755 {{/panel}}
756
757 === Previous colloquia ===
758
759 {{panel borderColor="#8C8A87" bgColor="#eeeeee" borderStyle="solid"}}
760 === Wednesday, October 28, 2009, in the Auditorium CK112 at 4.15 PM. ===
761
762 The speaker is PROFESSOR JANI ONNINEN, and he will give a talk on
763
764 DEFORMATIONS OF FINITE (TOTAL) CONFORMAL ENERGY AND THE NITSCHE CONJECTURE
765
766 ==== Abstract ====
767
768 We give an account of a few of recent developments in which the quasiconformal
769 theory and nonlinear elasticity share common problems of compelling mathematical
770 interest. We study deformations between bounded domains in Euclidean n-space. There are
771 many new and unexpected phenomena concerning existence, uniqueness and failure of radial
772 symmetry of the extremal deformations. We also introduce natural conditions on the
773 integrand that guarantee the existence and global invertibility of the minimizers. The
774 talk is based on joint work with Tadeusz Iwaniec and Leonid V. Kovalev.
775
776 As is already a custom, after the talk there will be wine, pizza and beverages available! ... and don't forget that the chairman of the department wants everyone to be present.
777 {{/panel}}
778
779 (% class="auto-cursor-target" %)
780 \\
781
782 {{panel borderColor="#8C8A87" bgColor="#eeeeee" borderStyle="solid"}}
783 === Wednesday, September 30, 2009, the Auditorium CK112 at 4.15 PM. ===
784
785 The speaker is PROFESSOR MATTI JUTILA, and he will give a talk on
786
787 THE ROLE OF HARDY'S FUNCTION IN THE THEORY OF RIEMANN'S ZETA FUNCTION
788
789 ==== Abstract ====
790
791 The following topics will be discussed: the history of Riemann's zeta-function with its connection to the distribution of primes,
792 definition and basic properties of Hardy's function, its role in the characterization and numerical verification of Riemann's hypothesis,
793 and recent work on the integral function of Hardy's function.
794
795 As is already a custom, after the talk there will be wine, pizza and beverages available! ... and don't forget that the chairman of the department wants everyone to be present.
796 {{/panel}}
797
798 (% class="auto-cursor-target" %)
799 \\
800
801 {{panel borderColor="#8C8A87" bgColor="#eeeeee" borderStyle="solid"}}
802 === Wednesday, June 3., 2009, the Auditorium CK112 at 4.15 PM. ===
803
804 The speaker is PROFESSOR MATS GYLLENBERG and he will give a talk on
805
806 POPULATION DYNAMICS, DELAY EQUATIONS AND SEMIGROUPS
807
808 ==== Abstract ====
809
810 In this talk I explain the basic principles for modelling structured populations. I show that every relevant population model could and should be formulated as a delay equation. Finally I show how the theory of adjoint semigroups can be used for stability and bifurcation analysis of delay equations.
811
812 As is already a custom, after the talk there will be wine, pizza and beverages available! ... and don't forget that the chairman (MG) of the department wants everyone to be present.
813 {{/panel}}
814
815 (% class="auto-cursor-target" %)
816 \\
817
818 {{panel borderColor="#8C8A87" bgColor="#eeeeee" borderStyle="solid"}}
819 === Wednesday, April 29, 2009, the Auditorium CK112 at 4.15 PM. ===
820
821 The speaker is PROFESSOR JOUKO MICKELSSON, and he will give a talk on
822
823 THE GOOD, THE BAD AND THE UGLY: THE OPERATOR RESIDUE, THE TRACE, AND THE FREDHOLM INDEX
824
825 ==== Abstract ====
826
827 Index theory of Fredholm operators lies at the crossroads of analysis, geometry, and topology with important applications to mathematical physics. The great breakthrough in the geometric index theory was made in seminal papers by M.F. Atiyah and I.M. Singer about fourty years ago, and since then there has been active research on this field with new connections to other fields of mathematics and physics.
828
829 In this talk I want to describe in a simple manner some aspects of the theory using a method based on residue calculus and trace extensions of linear operators in a Hilbert space.
830
831 As is already a custom, after the talk there will be wine, pizza and beverages available! ... and don't forget that the chairman of the department wants everyone to be present.
832 {{/panel}}
833
834 (% class="auto-cursor-target" %)
835 \\
836
837 {{panel borderColor="#8C8A87" bgColor="#eeeeee" borderStyle="solid"}}
838 === Wednesday, March 25, 2009, in the Auditorium CK112 at 4.15 PM. ===
839
840 The speaker is PROFESSOR YUVAL PERES, Microsoft research and University of Washington, and he will give a talk on
841
842 VISUAL MATHEMATICS- THE CASE OF FAIR ALLOCATIONS
843
844 ==== Abstract ====
845
846 I will give some recent examples where properly simulating and viewing mathematical objects has led to new mathematics, some of it appearing in the Annals of Math.
847
848 I will focus on the fair allocation problem: Given an infinite collection of points in the plane (a point process) how do we allocate the same area to each point in a decentralized way? See [[http:~~/~~/www.stat.berkeley.edu/~~~~peres/stable/stable.html>>url:http://www.stat.berkeley.edu/~~peres/stable/stable.html||shape="rect"]]for one solution, and [[http:~~/~~/depts.washington.edu/probab/research.php>>url:http://depts.washington.edu/probab/research.php||shape="rect"]] for another.
849
850 Different approaches to this problem have connections with probability, combinatorics, ergodic theory, the Riemann mapping theorem, and Newtonian gravity (in higher dimensions); see the gallery at [[http:~~/~~/www.math.huji.ac.il/~~~~romik/Site/Allocations.html>>url:http://www.math.huji.ac.il/~~romik/Site/Allocations.html||shape="rect"]] but there is lots of room for new creative ideas.
851
852 The talk will be accessible to a broad mathematical audience.
853
854 As is already a custom, after the talk there will be wine, pizza and beverages available! ... and don't forget that the chairman of the department wants everyone to be present.
855 {{/panel}}
856
857 (% class="auto-cursor-target" %)
858 \\
859
860 {{panel borderColor="#8C8A87" bgColor="#eeeeee" borderStyle="solid"}}
861 === Wednesday, February 25, 2009, the Auditorium CK112 at 4 PM. ===
862
863 The speaker is professor PROFESSOR SAMULI SILTANEN and he will give a talk on
864
865 INVERSION METHODS FOR THREE-DIMENSIONAL MEDICAL X-RAY IMAGING
866
867 ==== Abstract ====
868
869 In medical X-ray tomography, three dimensional structure of tissue is reconstructed from a collection of projection images.
870 Mathematically, this data can be interpreted as a collection of line integrals of nonnegative X-ray attenuation coefficient. In many practical imaging situations only a small number of truncated projections is available from a limited range of view.
871 Traditional reconstruction algorithms, such as filtered backprojection, do not give satisfactory results when applied to such
872 data. More suitable reconstruction algorithms based on Bayesian inversion are studied. In this approach, a priori information is used to compensate for the incomplete information of the measurement data. Examples with in vitro measurements from dental radiology are presented.
873
874 After the talk there will be wine and pizza!
875 {{/panel}}
876
877 (% class="auto-cursor-target" %)
878 \\
879
880 {{panel borderColor="#8C8A87" bgColor="#eeeeee" borderStyle="solid"}}
881 === Wednesday, January 28, 2009, the Auditorium CK112 ===
882
883 The speaker is PROFESSOR ELJA ARJAS and he will give a talk on
884
885 RANDOMNESS, PROBABILITY, AND LEARNING:
886 SOME SIMPLE ILLUSTRATIONS AND IDEAS,
887
888 ==== Abstract: ====
889
890 The purpose of this talk is to discuss first principles of statistical inference in the context of simple random sampling. In particular, I will consider the situation of data accumulating over time, and the consequent learning. The only prerequisite for following the talk is familiarity with the basic rules of probability calculus.
891
892 NOTE ALSO THAT WINE WILL BE SERVED AFTER THE COLLOQUIUM.
893 {{/panel}}
894
895 (% class="auto-cursor-target" %)
896 \\