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TZID:Asia/Jerusalem
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DTSTART:20171029T020000
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DTSTART:20180323T020000
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UID:calendar.49412.field_date.0@mathematics.huji.ac.il
DTSTAMP:20191122T145121Z
CREATED:20171229T230903Z
DESCRIPTION:Date: \n\n2:30pm to 3:30pm\n\n\n\n\nSee also: Events & Semina
rs\, ColloquiumLocation: \n\nManchester Building (Hall 2)\, Hebrew Univers
ity Jerusalem\n\n\nOne of the mainstream and modern tools in the study of
non abelian groups are quasi-morphisms. These are functions from a group t
o the reals which satisfy homomorphism condition up to a bounded error. No
wadays they are used in many fields of mathematics. For instance\, they ar
e related to bounded cohomology\, stable commutator length\, metrics on di
ffeomorphism groups\, displacement of sets in symplectic topology\, dynami
cs\, knot theory\, orderability\, and the study of mapping class groups an
d of concordance group of knots.\nLet S be a compact oriented surface. In
this talk I will discuss several invariant metrics and quasi-morphisms on
the identity component Diff_0(S\, area) of the group of area preserving di
ffeomorphisms of S. In particular\, I will show that some quasi-morphisms
on Diff_0(S\, area) are related to the topological entropy. More precisely
\, I will discuss a construction of infinitely many linearly independent q
uasi-morphisms on Diff_0(S\, area) whose absolute values bound from below
the topological entropy. If time permits\, I will define a bi-invariant me
tric on this group\, called the entropy metric\, and show that it is unbou
nded. Based on a joint work with M. Marcinkowski.\n\n Export\n \n\n \ns
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DTSTART;TZID=Asia/Jerusalem:20171104T143000
DTEND;TZID=Asia/Jerusalem:20171104T153000
LAST-MODIFIED:20191104T060051Z
SUMMARY:Colloquium: Michael Brandenbursky (BGU) - 'Entropy\, metrics and qu
asi-morphisms'
URL;TYPE=URI:https://mathematics.huji.ac.il/event/colloquium-michael-brande
nbursky-bgu-entropy-metrics-and-quasi-morphisms-0
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