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UID:www.tcs.tifr.res.in/event/1189
DTSTAMP:20230914T125954Z
SUMMARY:Extension Preservation in the Finite and Prefix Classes of First Or
 der Logic
DESCRIPTION:Speaker: Abhisekh Sankaran (University of Cambridge)\n\nAbstrac
 t: \nIt is well known that the classic Los-Tarski preservation theorem fai
 ls in the finite: there are first order definable classes of finite struct
 ures closed under extensions which are not definable in the existential fr
 agment of first order logic. We strengthen this [1] by constructing for ev
 ery n\, first order definable classes of finite structures closed under ex
 tensions which are not definable with n quantifier alternations. The class
 es we construct are definable in the extension of Datalog with negation. T
 his answers negatively an open question posed by Rosen and Weinstein [2].\
 n[1] Anuj Dawar and Abhisekh Sankaran. Extension preservation in the finit
 e and prefix classes of first order logic. Proceedings of the 31st Compute
 r Science Logic (CSL)\, Ljubljana\, Slovenia\, January 25 -- 28\, 2021\, p
 p. 18:1 -- 18:13.\n[2] Eric Rosen and Scott Weinstein. Preservation theore
 ms in finite model theory. In the International Workshop on Logic and Comp
 utational Complexity\, pages 480âEUR"502. Springer\,1994.\n\nBio: Abhisek
 h Sankaran is a post-doctoral research associate at the Department of Comp
 uter Science and Technology of the University of Cambridge\, UK. He works 
 with Prof. Anuj Dawar  and has been at Cambridge since September 2018. Pri
 or to that\, he was a post-doctoral fellow for a year in the Theoretical C
 omputer Science Wing of the Institute of Mathematical Sciences Chennai. He
  completed his Ph.D. and also his Bachelors and Masters from the Computer 
 Science department of IIT Bombay. His research interests lie in mathematic
 al logic\, particularly classical and finite model theory\, and parameteri
 zed algorithms\, particularly algorithmic metatheorems. For the present se
 minar\, he will be  speaking on a classical model theoretic result in the 
 context of finite structures.\n
URL:https://www.tcs.tifr.res.in/web/events/1189
DTSTART;TZID=Asia/Kolkata:20220222T160000
DTEND;TZID=Asia/Kolkata:20220222T170000
LOCATION:Via Zoom
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