Mathematical Colloquium

 

PROGRAM


ODELJENJE ZA MATEMATIKU
MATEMATIČKOG INSTITUTA SANU

                      


PROGRAM ZA NOVEMBAR 2019.


Petak 15.11.2019. u 14:15, sala 301f, MISANU, Kneza Mihaila 36
Saeed Ghasemi, Institute of Mathematics CAS, Prague
STRONGLY SELF-ABSORBING C*-ALGEBRAS AND FRAISSE LIMITS
A unital separable C*-algebra (other than the C*-algebra of all complex numbers) is strongly self-absorbing if it is isomorphic to its (minimal) tensor product with itself, in a "strong" sense. Strongly self-absorbing C*-algebras play a crucial role in Elliott's classification program of separable nuclear C*-algebras by K-theoretic data. Among them, the Jiang-Su algebra Z has a special place and, to this date, the classification of separable, simple, unital, nuclear C*-algebras that tensorially absorb Z and satisfy the UCT has been the most remarkable achievement of the classification program. In their original paper from 1999, Jiang and Su already prove that Z is strongly self-absorbing. However, their proof uses heavy tools from classification, such as KK-theory and it is quite difficult. We give a self-contained, rather elementary and direct proof for the fact that Z is strongly self-absorbing. This is done by establishing a general connection between the strongly self-absorbing C*-algebras and the Fraisse limits of categories of C*-algebras that are sufficiently closed under tensor products. It was previously known that Z can be realized as the "Fraisse limit" of a certain category of C*-algebras and embeddings consisting of its building blocks, i.e. the prime dimension-drop algebras.
Zajednički sastanak sa Seminarom za logiku



Petak, 22.11.2019. u 14:15, sala 301f, MISANU, Kneza Mihaila 36
Dragan Urošević, Matematički institut SANU
REŠAVANJE NEKIH VARIJANTI PROBLEMA TRGOVAČKOG PUTNIKA PRIMENOM METODE PROMENLJIVIH OKOLINA
Biće prikazano nekoliko varijanti problema trgovačkog putnika: problem trgovačkog putnika sa preuzimanjem i isporukom, problem isporučioca (Travelling Deliveryman Problem) i problem servisera sa profitom (Travelling Repairman Problem with Profits). Ovi problemi se razlikuju od klasičnog problema trgovačkog putnika u funkciji cilja i/ili u dodatnim ograničenjima vezanim za maršrutu (tako da prostor rešenja nije skup svih mogućih permutacija mesta/korisnika koje treba posetiti). Zbog toga se usložnjava postupak istraživanja nekih (ili svih) okolina razvijenih za klasični problem trgovačkog putnika. Ali koristeći određene napredne strukture podataka za reprezentovanje rešenja moguće je ubrzati istraživanje nekih okolina. U izlaganju će biti prikazane strukture podataka koje su korišćene. Takođe je značajan deo istraživanja bio posvećen izboru najboljeg redosleda obilaska okolina.




Odeljenje za matematiku je opsti matematicki seminar namenjen sirokoj publici. Predavanja su prilagodjena matematicarima i onima koji zele da to postanu.


Zoran Petric, Odeljenje za matematiku Matematickog instituta SANU