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UID:/NewsandEvents/Archives/current/newsitem/16087
 /14-April-2026-Computational-Social-Choice-Seminar
 -Soumyajit-Pyne
DTSTAMP:20260226T142413
SUMMARY:Computational Social Choice Seminar, Soumy
 ajit Pyne
ATTENDEE;ROLE=Speaker:Soumyajit Pyne
DTSTART;TZID=Europe/Amsterdam:20260414T160000
LOCATION:Room L1.08, Lab42, Science Park 900, Amst
 erdam
DESCRIPTION:The Hotelling-Downs model studies stra
 tegic positioning of candidates along an ideologic
 al line where voters choose the nearest candidate.
  While equilibrium structure has been widely analy
 zed, little is known about the computational compl
 exity of finding equilibria. We provide algorithmi
 c results for computing equilibria in both discret
 e and continuous variants of the model. For the co
 ntinuous case, we prove a structural result showin
 g that whenever an equilibrium exists, one also ex
 ists with rational positions of bounded complexity
 , enabling discretization via a notion we call ref
 lection barriers. Using dynamic programming, we sh
 ow: (i) equilibrium existence is decidable in poly
 nomial time for discrete candidate locations; (ii)
  in the continuous-candidate and discrete-voter se
 tting, equilibria can be computed in pseudo-polyno
 mial time; and (iii) in the fully continuous setti
 ng, an ϵ-equilibrium can be computed in time polyn
 omial in 1/ϵ. This is joint work with Umang Bhaska
 r.  For more information on the Computational Soci
 al Choice Seminar, please consult https://staff.sc
 ience.uva.nl/u.endriss/seminar/.
X-ALT-DESC;FMTTYPE=text/html:\n  <p>The Hotelling-
 Downs model studies strategic positioning of candi
 dates along an ideological line where voters choos
 e the nearest candidate. While equilibrium structu
 re has been widely analyzed, little is known about
  the computational complexity of finding equilibri
 a. We provide algorithmic results for computing eq
 uilibria in both discrete and continuous variants 
 of the model. For the continuous case, we prove a 
 structural result showing that whenever an equilib
 rium exists, one also exists with rational positio
 ns of bounded complexity, enabling discretization 
 via a notion we call reflection barriers. Using dy
 namic programming, we show: (i) equilibrium existe
 nce is decidable in polynomial time for discrete c
 andidate locations; (ii) in the continuous-candida
 te and discrete-voter setting, equilibria can be c
 omputed in pseudo-polynomial time; and (iii) in th
 e fully continuous setting, an ϵ-equilibrium can b
 e computed in time polynomial in 1/ϵ. This is join
 t work with Umang Bhaskar.</p>\n  <p>For more info
 rmation on the Computational Social Choice Seminar
 , please consult <a href="https://staff.science.uv
 a.nl/u.endriss/seminar/" target="_blank" rel="noop
 ener">https://staff.science.uva.nl/u.endriss/semin
 ar/</a>.</p>\n
URL:https://staff.science.uva.nl/u.endriss/seminar
 /
CONTACT:Ulle Endriss at ulle.endriss at uva.nl
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