C ONFERENCE IN HONOUR OF D ON DAVIS String Topological Robotics L EHIGH U NIV., B ETHLEHEM , P ENNSYLVANIA , USA My Ismail Mamouni Agrégé-Doctor CRMEF Rabat, Morocco http ://myismail.net [email protected] My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 1 / 49 Joint work with Joint work with Derfoufi Younes Fac. Sc. Meknes, Morocco My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 2 / 49 Our Main Goal Marrying Topological Robotics and String Topology My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 3 / 49 Hard Task Feeling Giant I Giant II Baby My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 4 / 49 Love and Peace and Mathematics Ê¿ñ JÜ Ï @ É¿ñ JJ ʯ àñ é<Ë@ Õæ ¢ ªË@ Y á ÔgQË@ é<Ë@ Õæ k QË@ Õæ . é<Ë@ úΫ ð Translation : Let’s Go. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 5 / 49 Hard Task Context Closed, orientable mfld Path-connect. space path-conn. G-mfld compact or not orientable or not My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 6 / 49 Content 1 2 3 4 Brief Introduction Topological Robotics String Topology Strings through Topological Robotics Loop Motion Planning Algorithms (LMPA) String LMPA Product Acknowledgements Summer School Announcement My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 7 / 49 Brief Introduction Topological Robotics Robotics My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 8 / 49 Brief Introduction Topological Robotics Robotics Motion Planning Algorithm (MPA) Given a robot, a motion planning algorithm is a set of rules determining to the robot how to move from one state to another. X , The configuration space of a robot is just the set of all robot states. A motion is just a path from a point to another in this configuration space. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 9 / 49 Brief Introduction Topological Robotics Topological Robotics Once X and PX topologized Farber’s Topological Approach (2003) An MPA is any continuous section s : X 2 −→ PX of the double evaluation π : PX −→ X 2 . γ 7−→ (γ(0), γ(1)) My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 10 / 49 Brief Introduction Topological Robotics Topological Robotics Farber’s Key Queries on MPA 1 Existence 2 Continuity MPA exist whenever X path-connected MPA are continuous iff X is contractible My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 11 / 49 Brief Introduction Topological Robotics Topological Robotics Farber’s Key Remark on MPA Continuity of motion planning means that close initial-final pairs (A, B) and (A0 , B 0 ) produce close movements s(A, B) and s(A0 , B 0 ). discontinuity will result in the instability of behaviour My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 12 / 49 Brief Introduction Topological Robotics Topological Robotics Farber’s Key Ingredient : Topological Complexity TC(X) := minimal necessary number k (or infinity) to cover X × X by k + 1 open sets X × X = U0 ∪ · · · ∪ Uk on each for each there exists a local MPA si : Ui −→ PX (i.e., π ◦ si = idUi ). My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 13 / 49 Brief Introduction Topological Robotics Topological Robotics Interpretation TC measures the discontinuity of any motion planner and the algorithmic complexity of finding a motion planning algorithm. Low TC Farber (2003) : TC(X) = 0 iff X is contractible ; Grant-Lupton-Oprea (2013) : TC(X) = 1 iff X is homotopy equivalent to some odd-dimensional sphere ; Farber (2003) : TC(Sn ) = 2, whenever n is even. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 14 / 49 Brief Introduction Topological Robotics Topological Robotics Interpretation TC measures the discontinuity of any motion planner and the algorithmic complexity of finding a motion planning algorithm. Low TC Farber (2003) : TC(X) = 0 iff X is contractible ; Grant-Lupton-Oprea (2013) : TC(X) = 1 iff X is homotopy equivalent to some odd-dimensional sphere ; Farber (2003) : TC(Sn ) = 2, whenever n is even. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 14 / 49 Brief Introduction String Topology String Topology Chas’s and Sullivan’s Main Motivation (1999) Study algebraic structures on the homology of the loop space of a manifold. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 15 / 49 Brief Introduction String Topology String Topology Chas’s and Sullivan’s Main Goal Define transversely an intersection product at level of chains of loop. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 16 / 49 Brief Introduction String Topology Intersection Product at level of manifolds Recalling Y , Z some submanifolds of respective co-dimension i and j, are said to intersect transversely in X if for all x ∈ Y ∩ Z , one have Tx Y ⊕ Tx Z = Tx X . Hence, Y ∩ Z is a submanifold of X of co-dimension i + j. Intersection Product : [Y ∩ Z ] = [Y ] · [Z ]. Here [−], denotes the homological fundamental class that represents the named submanifold. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 17 / 49 Brief Introduction String Topology Intersection Product at level of loop spaces 1 Transeversality in LX := X S is a little specific 1 A path in LX is a path of loops ; 2 A velocity vector in this case is a vector field. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 18 / 49 Brief Introduction String Topology String Topology Chas’s and Sullivan’s Key ideas 1 Consider two families of closed oriented curves 2 At each point of intersection of two curves, form a new closed curve by going around the first curve and then going around the second. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 19 / 49 Brief Introduction String Topology String Topology Chas’s and Sullivan’s Mathematical Approach 1 1 consider γ : ∆i −→ X S and σ : ∆j −→ X S some 1 simplices of X S such that γ(1) : ∆i −→ X and 1 σ(1) : ∆j −→ X S intersect transversally in X ; compute the intersection product γ(1).σ(1) at each point (s, t) ∈ ∆i × ∆j such that γ(1)(s) = σ(1)(t) perform the composition of the loops γ(s) and σ(t) to 1 obtain, the (i + j − n)-simplex γ • σ : ∆i+j−n −→ X S (loop product) ; 1 1 set H∗ (X S ) := H∗+n (X S ; Z) (loop homology ) ; extend the loop product to loop homology product ; define a structure of associative graded commutative algebra : (H∗ (X ), •). My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 20 / 49 Strings through Topological Robotics Loop Motion Planning Algorithms (LMPA) Loop Motion Planning Algorithms (LMPA) Derfoufi, M. (2015) LMPA on a manifold X is any continuous section s : X × 1 X −→ X S of the loop evaluation π LP : X S γ 1 . −→ X × X 7−→ (γ(0), γ( 21 )) Interpretation Input : Pair (A=departure, B=target) ; Output : A goings and comings motion by requiring a come-back to the departure point. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 21 / 49 Strings through Topological Robotics Loop Motion Planning Algorithms (LMPA) Loop Motion Planning Algorithms (LMPA) Derfoufi, M. (2015) LMPA on a manifold X is any continuous section s : X × 1 X −→ X S of the loop evaluation π LP : X S γ 1 . −→ X × X 7−→ (γ(0), γ( 21 )) Interpretation Input : Pair (A=departure, B=target) ; Output : A goings and comings motion by requiring a come-back to the departure point. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 21 / 49 Strings through Topological Robotics Loop Motion Planning Algorithms (LMPA) Loop Motion Planning Algorithms (LMPA) Applications Areas The motion of a drone like an unmanned warplane or a guided TV camera ; The famous NP-complete problem of vehicle routing with pick-up and delivery Derfoufi, M. (2015) LMPAs exist iff X is contractible. Notation MLP (X ) denotes the set of all LMPAs on X My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 22 / 49 Strings through Topological Robotics Loop Motion Planning Algorithms (LMPA) Loop Motion Planning Algorithms (LMPA) Applications Areas The motion of a drone like an unmanned warplane or a guided TV camera ; The famous NP-complete problem of vehicle routing with pick-up and delivery Derfoufi, M. (2015) LMPAs exist iff X is contractible. Notation MLP (X ) denotes the set of all LMPAs on X My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 22 / 49 Strings through Topological Robotics Loop Motion Planning Algorithms (LMPA) Loop Motion Planning Algorithms (LMPA) Applications Areas The motion of a drone like an unmanned warplane or a guided TV camera ; The famous NP-complete problem of vehicle routing with pick-up and delivery Derfoufi, M. (2015) LMPAs exist iff X is contractible. Notation MLP (X ) denotes the set of all LMPAs on X My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 22 / 49 Strings through Topological Robotics String LMPA Product First Obstacle In Farber’s context LMPAs has sense iff X is contractible My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 23 / 49 Strings through Topological Robotics String LMPA Product First Obstacle In Farber’s context LMPAs has sense iff X is contractible Solution : Lubawski’s & Marzantowicz’s definition of MPA PX is replaced by PX ×X /G PX := {(γ, τ ) = ∈ PX × PX , G.γ(0) G.τ (1)}. Paths can have a discontinuity point, but this discontinuity is controlled by a group action. "motion planner" in the sense of Lubawski-Marzantowicz is stable in the Farber’s sense : small changes of either the initial or terminal point result in small changes of the path between them). My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 23 / 49 Strings through Topological Robotics String LMPA Product LMPA product Derfoufi, M. (2015) For any LMPA’s s1 and s2 , we set : µ(s1 , s2 )(A, B)(t) = s1 (A, B)(t) if 0 ≤ t ≤ 21 = s1 (A, B)(3t − 1) if 12 ≤ t ≤ 23 = s2 (A, B)(3t − 2) if 32 ≤ t ≤ 1 My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 24 / 49 Strings through Topological Robotics String LMPA Product LMPA product Key Inspiration Remark two free loops are composable iff they have a common base point. two LMPAs are composable iff they have two common base points. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 25 / 49 Strings through Topological Robotics String LMPA Product Next Aim Inspire from Laudenbach’s work He extends the theory of string topology to all manifolds, compact or not, orientable or not. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 26 / 49 Strings through Topological Robotics String LMPA Product Laudenbach context Small simplices Equip X with a chart A. A p-simplex σ : ∆i −→ X is said to be small iff there exists U(σ) ∈ A such that σ(∆i ) ⊂ U(σ) ; U(σ) is chosen once for all ; P Small p-chain : any linear combination nk σk of many finitely p-small simplices σk , with integer coefficients nk ∈ Z ; Small bi-simplex : σ × γ : ∆i × ∆j −→ X × X with σ and γ are both small. Small bi-chains : any linear combination P nk (σk × γk ) of many finitely small bi-simplices σk × γ, with integer coefficients nk ∈ Z. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 27 / 49 Strings through Topological Robotics String LMPA Product Laudenbach context Small Transverse bi-Simplices A small bi-simplex σ × γ : ∆i × ∆j −→ X × X is said to be transverse whenever the map σ × γ and all its faces are transverse to the diagonal map ∆X Recall Two maps are said to be transverse, when their image are, as submaniflods. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 28 / 49 Strings through Topological Robotics String LMPA Product Laudenbach context Small Transverse bi-Simplices A small bi-simplex σ × γ : ∆i × ∆j −→ X × X is said to be transverse whenever the map σ × γ and all its faces are transverse to the diagonal map ∆X Recall Two maps are said to be transverse, when their image are, as submaniflods. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 28 / 49 Strings through Topological Robotics String LMPA Product Our Key Idea Bridge from simplex of MLP (X ) to that of X 2 the bi-evaluation ev : MLP (X ) −→ X 2 , s 7−→ (s(−, −)(0), s(−, −)(1/2)) relates any i-simplex Σ : ∆i −→ MLP (X ) of MLP (X ) to the i-simplex σ := ev (Σ) : ∆i −→ X 2 of X 2 . My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 29 / 49 Strings through Topological Robotics String LMPA Product Transeversality at level of LMPA chains A (i, j)-bi-simplex Σ × Γ : ∆i × ∆j −→ MLP (X ) × MLP (X ) is said to be small (resp. transverse) in MLP (X ), when the associated (i, j)-bi-simplex ev (Σ × Γ) := ev (Σ) × ev (Γ) : ∆i × ∆j −→ X 2 × X 2 is also in X 2 . My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 30 / 49 Strings through Topological Robotics String LMPA Product Key Remark I Hence W = ev (Σ × Γ)−1 (∆X 2 ) is (i + j − 2n)-dimensional orientable sub-manifold of ∆i ×∆j , with corner that can be triangulated. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 31 / 49 Strings through Topological Robotics String LMPA Product Key Remark I Hence W = ev (Σ × Γ)−1 (∆X 2 ) is (i + j − 2n)-dimensional orientable sub-manifold of ∆i ×∆j , with corner that can be triangulated. Illustrative Diagram My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 31 / 49 Strings through Topological Robotics String LMPA Product For x ∈ W , put (Σ × Γ)(x) = (s1 , s2 ) ∈ MLP (X ) × MLP (X ). Illustrative Diagram My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 32 / 49 Strings through Topological Robotics String LMPA Product For x ∈ W , put (Σ × Γ)(x) = (s1 , s2 ) ∈ MLP (X ) × MLP (X ). Key Remark II Note that ev (Σ × Γ) ev (Σ × Γ) = ∈ (s1 (−, −)(0), s1 (−, −)(1/2), s2 (−, −)(0), s2 (−, −)(1/2)) ∆X 2 s1 and s2 are composable in MLP (X ) since they have two common base points, namely A = s1 (−, −)(0) = s2 (−, −)(0) and B = s1 (−, −)(1/2) = s2 (−, −)(1/2). Illustrative Diagram My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 32 / 49 Strings through Topological Robotics String LMPA Product Intersection LMPA product Derfoufi, M. (2015) Σ.Γ := µ((Σ × Γ)|W ) is well defined at level of transverse bi-simplices of MLP (X ) and can be extended P naturaly and linearly at level of transverse bi-chain Σk × Γk , where each simplex Σk × Γk is transverse. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 33 / 49 Strings through Topological Robotics String LMPA Product Loop Motion Homology Twisted boundary operator at level of p-simplices of MLP (X ) : ∂Σ := P p i i=0 εi (−1) Fi Σ, where εi is the sign of the Jacobian of the coordinates change U(ev (Fi Σ)) −→ U(ev (Σ)). Here Fi denotes the i-th face. Loop Motion Homology H∗ (MLP (X ), ∂) coefficients are taken in Z. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 34 / 49 Strings through Topological Robotics String LMPA Product Loop Motion Homology Twisted boundary operator at level of p-simplices of MLP (X ) : ∂Σ := P p i i=0 εi (−1) Fi Σ, where εi is the sign of the Jacobian of the coordinates change U(ev (Fi Σ)) −→ U(ev (Σ)). Here Fi denotes the i-th face. Loop Motion Homology H∗ (MLP (X ), ∂) coefficients are taken in Z. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 34 / 49 Strings through Topological Robotics String LMPA Product String LMPA Homology Product Derfoufi, M. (2015) [Σ].[Γ] = [Σ.Γ]. Well defined : Sketch of Proof 1 Claim 1 : Any product bi-cycle can be represented, up to a small boundary preserving homotopy, by a small ad transverse product bi-cycle, and that it does not depend on the choice of the homological representants. 2 Claim 2 : The homological class [Σ.Γ] does not depend on the choice of the homological representants. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 35 / 49 Strings through Topological Robotics String LMPA Product String LMPA Homology Product Derfoufi, M. (2015) [Σ].[Γ] = [Σ.Γ]. Well defined : Sketch of Proof 1 Claim 1 : Any product bi-cycle can be represented, up to a small boundary preserving homotopy, by a small ad transverse product bi-cycle, and that it does not depend on the choice of the homological representants. 2 Claim 2 : The homological class [Σ.Γ] does not depend on the choice of the homological representants. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 35 / 49 Strings through Topological Robotics String LMPA Product String LMPA Homology Product Derfoufi, M. (2015) [Σ].[Γ] = [Σ.Γ]. Well defined : Outlines of Proof My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 36 / 49 Strings through Topological Robotics String LMPA Product String LMPA Homology Product Derfoufi, M. (2015) [Σ].[Γ] = [Σ.Γ]. Well defined : Outlines of Proof My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 36 / 49 Strings through Topological Robotics String LMPA Product String LMPA Homology Recall Hi (MLP (X ), ∂)⊗Hj (MLP (X ), ∂) −→ Hi+j−2n (MLP (X ), ∂). As Promised H∗ (MLP (X )) := H∗+2n (MLP (X ), ∂), endowed with the String LMPA Homology Product Hi (MLP (X )) ⊗ Hj (MLP (X )) −→ Hi+j (MLP (X )) is a commutative and associative graded algebra. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 37 / 49 Strings through Topological Robotics String LMPA Product String LMPA Homology Recall Hi (MLP (X ), ∂)⊗Hj (MLP (X ), ∂) −→ Hi+j−2n (MLP (X ), ∂). As Promised H∗ (MLP (X )) := H∗+2n (MLP (X ), ∂), endowed with the String LMPA Homology Product Hi (MLP (X )) ⊗ Hj (MLP (X )) −→ Hi+j (MLP (X )) is a commutative and associative graded algebra. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 37 / 49 Strings through Topological Robotics String LMPA Product M. Chas, D. Sullivan, String Topology, arXiv :math/9911159 [math.GT]. M. Farber, Topological complexity of motion planning, Discrete Comput. Geom., vol. 29 (2003), no. 2, 211-221. F. Laudenbach, A note on the Chas-Sullivan product, L’Enseignement Mathématique, Vol. 57, Issue 1-2 (2011), 3-21. W. Lubawski, W. Marzantowicz, Invariant topological complexity, Bull. London Math. Soc., vol. 47 (2015) 101-117. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 38 / 49 Acknowledgements Acknowledgements Organizers My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 39 / 49 Acknowledgements Acknowledgements Organizers 20 Emails with me x 100 Participants+...=.... My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 39 / 49 Acknowledgements ´ Poland Zbigniew Błaszczyk, Poznan, For pointing out our attention to the Lubawski’s and Marzantowicz’s work My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 40 / 49 Acknowledgements Acknowledgements David Chataur, Lille, France For pointing out our attention to the Laudenbach’s work My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 41 / 49 Acknowledgements Acknowledgements MAAT, Moroccan Research Group My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 42 / 49 Acknowledgements MAAT : Moroccan Area of Algebraic Topology Born : 2012 ; Logo : Home Page : http ://algtop.net Members : 3 professors, 7 PhD Students, 30 Master Students ; Scientific production since 2012 1 Papers Published=1 Accepted=2 Submitted=7 On Progress=3 2 3 Seminar : Monthly Research School : Bi-Annual, Geometry, Topology in Physics and Mathematics= GeToPhyMa. My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 43 / 49 Acknowledgements GeToPhyMa History 2014 : on Moduli spaces, in memory of Bill Thurston (1946-2012) 2013 : on Operads, in memory of Jean Louis Loday (1946-2012) 2012 : General lectures 2011 : General lectures My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 44 / 49 Summer School Announcement GeToPhyMa-2016 July 10-20, 2016 (Rabat, Morocco) Home page : http ://algtop.net/geto16 Topic : Rational Homotopty Theory and its Interactions 17 Speakers Scientific Contents : 6 courses blocks, 30 hours of courses, 14 hours of exercises or/and discussion sessions, and 6x20mn-communications. Excursions : One half day Casablanca visit, One half day Rabat visit, Two days (Fes-Meknes, Atlas Mountains) excursion My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 45 / 49 Summer School Announcement GeToPhyMa-2016 Will Celebrate Jim Stasheff Dennis Sullivan 80th Anniversary 75th Anniversary My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 46 / 49 Summer School Announcement Don Davis’s 70th birthday My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 47 / 49 Summer School Announcement Questions or Comments are accepted in slowly formulated My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 48 / 49 Summer School Announcement @Qº My Ismail Mamouni Lehigh Univ., Bethlehem, Pennsylvania, USA May 22-24, 2015 49 / 49
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