IJS KOLOKVIJ, sreda, 20. 04. 2016; ob 13. uri; prof. dr. Nir S. Gov

[Tanja Debevec]

Vabimo vas na 17. predavanje iz sklopa "Kolokviji na IJS" v letu 2015/16, ki bo v sredo, 20. aprila 2016, ob 13. uri v Veliki predavalnici Instituta »Jožef Stefan«  na Jamovi cesti 39 v Ljubljani. Napovednik predavanja najdete tudi na naslovu http://www.ijs.si/ijsw/Koledar_prireditev, posnetke preteklih predavanj pa na http://videolectures.net/kolokviji_ijs. 

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prof. dr. Nir S. Gov

Weizmann Institute of Science, Rehovot, Izrael

 

Fizikalno modeliranje kolektivnega gibanja v skupinah živali: prenašajoče mravlje

 

Kolektivni transport težkih bremen je zahtevna naloga in ga v resnici skoraj ne poznamo le pri mravljah in ljudeh. Da bi dosegli učinkovit transport, je treba premagati nasprotja znotraj skupine. A zaradi konformizma je lahko taka skupina premalo odzivna na nove podatke. Zato je kolektivni transport pri mravljah idealen modelski sistem za raziskovanje optimizacije teh nasprotujočih si zahtev v skupinah živali. Predstavili bomo pristop, kjer za opis kolektivnega transporta uporabimo kombinacijo eksperimentov in teorije. Mravlje opišemo z binarnimi Isingovimi spini, ki predstavljajo dve vlogi mravelj pri transport. Pokaže se, da so mravlje kot kolektiv v bližini kritične točke, kjer je njihov odziv na nanovo vključeno mravljo karseda velik. Ugotovili smo, da je velikost skupine sorazmerna z obratno efektivno temperaturo, tako da lahko s spreminjanjem velikosti skupine dosežemo mezoskopski prehod vrste red-nered. Če breme ogradimo z nitjo, se prične sistem vesti kot močno nelinearno nihalo. Teoretično smo napovedali, da se pri kritični velikosti v sistemu zgodi Hopfova bifurkacija, ki ji sledi globalna bifurkacija s polnimi nihaji. Te napovedi smo presenetljivo dobro podkrepili z eksperimenti.

 

Predavanje bo v angleščini.

Lepo vabljeni!

 

 

 




We invite you to the 17th Institute colloquium in the academic year 2015/16. The colloquium will be held on Wednesday April 20, 2016 at 1 PM in the main Institute lecture hall, Jamova 39, Ljubljana. To read the abstract click  http://www.ijs.si/ijsw/Koledar_prireditev. Past colloquia are posted on  http://videolectures.net/kolokviji_ijs.

 

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prof. dr. Nir S. Gov

Weizmann Institute of Science, Rehovot, Israel

 

Physical modeling of collective motion in animal groups: Carrying ants

 

Collectively carrying a heavy load is a hard task and in fact is rarely seen outside ants and humans. Conflicts within the group must be suppressed to succeed with efficient collective transport. However, conformism may render the system unresponsive to new information. Collective transport by ants is therefore an ideal model system to study how animal groups optimize these opposing requirements. We combine experiments and theory to characterize the collective transport process. The ants are modeled as binary Ising spins, representing the two roles ants can perform during transport. It turns out that the ants poise themselves collectively near a critical point where the response to a newly attached ant is maximized. We identify the size as being proportional to an inverse effective temperature and thus the system can exhibit a mesoscopic transition between order and disorder by manipulating the size. Constraining the cargo with a string makes the system behave as a strongly non-linear pendulum. Theoretically we predict that a Hopf bifurcation occur at a critical size followed by a global bifurcation where full swings emerge. Remarkably, these theoretical predictions were verified experimentally.       

 

Cordially invited!

 

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