BEGIN:VCALENDAR
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PRODID:researchseminars.org
CALSCALE:GREGORIAN
X-WR-CALNAME:researchseminars.org
BEGIN:VEVENT
SUMMARY:Ralf Meyer
DTSTART;VALUE=DATE-TIME:20200930T120000Z
DTEND;VALUE=DATE-TIME:20200930T133000Z
DTSTAMP;VALUE=DATE-TIME:20230925T233001Z
UID:WSIPM/2
DESCRIPTION:Title: Gr
oupoid models and C*-algebras of diagrams of groupoid correspondences\
nby Ralf Meyer as part of Western Sydney\, IPM joint workshop on Operator
Algebras\n\n\nAbstract\nA groupoid correspondence is a generalised morphi
sm between étale groupoids. Topological graphs\, self-similarities of gr
oups\, or self-similar graphs are examples of this. Groupoid corresponden
ces induce C*-correspondences between groupoid C*-algebras\, which then gi
ve Cuntz-Pimsner algebras. The Cuntz-Pimsner algebra of a groupoid corres
pondence is isomorphic to a groupoid C*-algebra of an étale groupoid buil
t from the groupoid correspondence. This gives a uniform construction of
groupoid models for many interesting C*-algebras\, such as graph C*-algebr
as of regular graphs\, Nekrashevych's C*-algebras of self-similar groups a
nd their generalisation by Exel and Pardo for self-similar graphs. If pos
sible\, I would also like to mention work in progress to extend this theor
em to relative Cuntz-Pimsner algebras\, which would then cover all topolog
ical graph C*-algebras.\nGroupoid correspondences form a bicategory. This
structure is already used to form the groupoid model of a groupoid corres
pondence. It also allows us to define actions of monoids or\, more genera
lly\, of categories on groupoids by groupoid correspondences. Passing to
C*-algebras\, this gives a product system where the unit fibre is a groupo
id C*-algebra. If the monoid is an Ore monoid\, then the Cuntz-Pimsner al
gebra of this product system is again a groupoid C*-algebra of an étale g
roupoid\, which is defined directly from the action by groupoid correspond
ences. For more general monoids\, the two constructions become different\
, however. We show this in a special case that is related to separated gr
aph C*-algebras and their tame versions.\n
LOCATION:https://researchseminars.org/talk/WSIPM/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Aidan Sims
DTSTART;VALUE=DATE-TIME:20201001T103000Z
DTEND;VALUE=DATE-TIME:20201001T120000Z
DTSTAMP;VALUE=DATE-TIME:20230925T233001Z
UID:WSIPM/5
DESCRIPTION:Title: Re
construction of groupoids\, and classification of Fell algebras\nby Ai
dan Sims as part of Western Sydney\, IPM joint workshop on Operator Algebr
as\n\n\nAbstract\nI will the history of reconstruction of groupoids from p
airs of operator algebras\, from Feldman and Moore’s results on von Neum
ann algebras through Kumjian’s and then Renault’s results about C*-alg
ebras of twists\, and including some recent results about groupoids that a
re not topologically principal. I will finish by outlining how Kumjian’s
theory leads to a Dixmier-Douady classification theorem for Fell algebras
.\n
LOCATION:https://researchseminars.org/talk/WSIPM/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ralf Meyer
DTSTART;VALUE=DATE-TIME:20201001T120000Z
DTEND;VALUE=DATE-TIME:20201001T133000Z
DTSTAMP;VALUE=DATE-TIME:20230925T233001Z
UID:WSIPM/6
DESCRIPTION:Title: Gr
oupoid models and C*-algebras of diagrams of groupoid correspondences\
nby Ralf Meyer as part of Western Sydney\, IPM joint workshop on Operator
Algebras\n\n\nAbstract\nA groupoid correspondence is a generalised morphi
sm between étale groupoids. Topological graphs\, self-similarities of gr
oups\, or self-similar graphs are examples of this. Groupoid corresponden
ces induce C*-correspondences between groupoid C*-algebras\, which then gi
ve Cuntz-Pimsner algebras. The Cuntz-Pimsner algebra of a groupoid corres
pondence is isomorphic to a groupoid C*-algebra of an étale groupoid buil
t from the groupoid correspondence. This gives a uniform construction of
groupoid models for many interesting C*-algebras\, such as graph C*-algebr
as of regular graphs\, Nekrashevych's C*-algebras of self-similar groups a
nd their generalisation by Exel and Pardo for self-similar graphs. If pos
sible\, I would also like to mention work in progress to extend this theor
em to relative Cuntz-Pimsner algebras\, which would then cover all topolog
ical graph C*-algebras.\nGroupoid correspondences form a bicategory. This
structure is already used to form the groupoid model of a groupoid corres
pondence. It also allows us to define actions of monoids or\, more genera
lly\, of categories on groupoids by groupoid correspondences. Passing to
C*-algebras\, this gives a product system where the unit fibre is a groupo
id C*-algebra. If the monoid is an Ore monoid\, then the Cuntz-Pimsner al
gebra of this product system is again a groupoid C*-algebra of an étale g
roupoid\, which is defined directly from the action by groupoid correspond
ences. For more general monoids\, the two constructions become different\
, however. We show this in a special case that is related to separated gr
aph C*-algebras and their tame versions.\n
LOCATION:https://researchseminars.org/talk/WSIPM/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dana Williams
DTSTART;VALUE=DATE-TIME:20201001T133000Z
DTEND;VALUE=DATE-TIME:20201001T150000Z
DTSTAMP;VALUE=DATE-TIME:20230925T233001Z
UID:WSIPM/7
DESCRIPTION:Title: Mo
rita equivalence\, the equivariant Brauer group\, and beyond\nby Dana
Williams as part of Western Sydney\, IPM joint workshop on Operator Algebr
as\n\n\nAbstract\nI will give a brief survey of work on the equivariant Br
auer group together with the necessary preliminaries as well as generaliza
tions involving groupoid C*-algebras.\n
LOCATION:https://researchseminars.org/talk/WSIPM/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gabor Szabo
DTSTART;VALUE=DATE-TIME:20201001T150000Z
DTEND;VALUE=DATE-TIME:20201001T163000Z
DTSTAMP;VALUE=DATE-TIME:20230925T233001Z
UID:WSIPM/8
DESCRIPTION:Title: Dy
namical criteria towards classifiable transformation group C*-algebras
\nby Gabor Szabo as part of Western Sydney\, IPM joint workshop on Operato
r Algebras\n\n\nAbstract\nIn this talk I will report on joint work with Da
vid Kerr regarding the structure and classification of certain transformat
ion group C*-algebras. It is a general important question when free minima
l actions of amenable groups on compact spaces give rise to crossed produc
t C*-algebras that fall within the scope of Elliott's program. After some
years of research where this had been partially settled for special classe
s of groups with methods related to noncommutative dimension theory\, Kerr
's notion of almost finiteness opens the door to systematically study this
problem for all amenable groups. I will give an overview of these techniq
ues and the current state-of-the-art\, culminating in our result that asse
rts the classifiability of such crossed products if the underlying space i
s finite-dimensional and the group has subexponential growth.\n
LOCATION:https://researchseminars.org/talk/WSIPM/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ralf Meyer
DTSTART;VALUE=DATE-TIME:20201002T103000Z
DTEND;VALUE=DATE-TIME:20201002T120000Z
DTSTAMP;VALUE=DATE-TIME:20230925T233001Z
UID:WSIPM/9
DESCRIPTION:Title: Gr
oupoid models and C*-algebras of diagrams of groupoid correspondences\
nby Ralf Meyer as part of Western Sydney\, IPM joint workshop on Operator
Algebras\n\n\nAbstract\nA groupoid correspondence is a generalised morphi
sm between étale groupoids. Topological graphs\, self-similarities of gr
oups\, or self-similar graphs are examples of this. Groupoid corresponden
ces induce C*-correspondences between groupoid C*-algebras\, which then gi
ve Cuntz-Pimsner algebras. The Cuntz-Pimsner algebra of a groupoid corres
pondence is isomorphic to a groupoid C*-algebra of an étale groupoid buil
t from the groupoid correspondence. This gives a uniform construction of
groupoid models for many interesting C*-algebras\, such as graph C*-algebr
as of regular graphs\, Nekrashevych's C*-algebras of self-similar groups a
nd their generalisation by Exel and Pardo for self-similar graphs. If pos
sible\, I would also like to mention work in progress to extend this theor
em to relative Cuntz-Pimsner algebras\, which would then cover all topolog
ical graph C*-algebras.\nGroupoid correspondences form a bicategory. This
structure is already used to form the groupoid model of a groupoid corres
pondence. It also allows us to define actions of monoids or\, more genera
lly\, of categories on groupoids by groupoid correspondences. Passing to
C*-algebras\, this gives a product system where the unit fibre is a groupo
id C*-algebra. If the monoid is an Ore monoid\, then the Cuntz-Pimsner al
gebra of this product system is again a groupoid C*-algebra of an étale g
roupoid\, which is defined directly from the action by groupoid correspond
ences. For more general monoids\, the two constructions become different\
, however. We show this in a special case that is related to separated gr
aph C*-algebras and their tame versions.\n
LOCATION:https://researchseminars.org/talk/WSIPM/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alcides Buss
DTSTART;VALUE=DATE-TIME:20201002T120000Z
DTEND;VALUE=DATE-TIME:20201002T133000Z
DTSTAMP;VALUE=DATE-TIME:20230925T233001Z
UID:WSIPM/10
DESCRIPTION:Title: A
menability for actions of groups on C*-algebras\nby Alcides Buss as pa
rt of Western Sydney\, IPM joint workshop on Operator Algebras\n\n\nAbstra
ct\nIn this lecture I will explain recent developments in the theory of am
enability for actions of groups on C*-algebras and Fell bundles\, based on
joint works with Siegfried Echterhoff\, Rufus Willett\, Fernando Abadie a
nd Damián Ferraro. Our main results prove that essentially all known noti
ons of amenability are equivalent. We also extend Matsumura’s theorem to
actions of exact locally compact groups on commutative C*-algebras and gi
ve a counter-example for the weak containment problem for actions on nonco
mmutative C*-algebras.\n
LOCATION:https://researchseminars.org/talk/WSIPM/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:N. Christopher Phillips
DTSTART;VALUE=DATE-TIME:20201002T133000Z
DTEND;VALUE=DATE-TIME:20201002T150000Z
DTSTAMP;VALUE=DATE-TIME:20230925T233001Z
UID:WSIPM/11
DESCRIPTION:Title: C
rossed products by automorphisms of C(X\,D)\nby N. Christopher Phillip
s as part of Western Sydney\, IPM joint workshop on Operator Algebras\n\n\
nAbstract\nWe consider crossed products of\nthe form $C^* \\bigl( {\\mathb
b{Z}}\, \\\, C (X\, D)\, \\\, \\alpha \\bigr)$\nin which $D$ is simple\, $
X$ is compact metrizable\,\n$\\alpha$ induces a minimal homeomorphism $h \
\colon X \\to X$\,\nand a mild technical assumption holds.\nIn a number of
examples inaccessible\nvia methods based on finite Rokhlin dimension\,\ne
ither because $D$ is not ${\\mathcal{Z}}$-stable\nor because $X$ is infini
te dimensional\,\nwe prove structural properties of the crossed product\,\
nsuch as (tracial) ${\\mathcal{Z}}$-stability\, stable rank one\,\nreal ra
nk zero\, and pure infiniteness.\n\nThe method is to find a centrally larg
e subalgebra\nof the crossed product which is a direct limit of\n``recursi
ve subhomogeneous algebras over $D$''.\nWith a better understanding of suc
h direct limits\,\nmany more examples would become accessible.\n\nThis is
joint work with Dawn Archey and Julian Buck.\n
LOCATION:https://researchseminars.org/talk/WSIPM/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alex Kumjian
DTSTART;VALUE=DATE-TIME:20201002T150000Z
DTEND;VALUE=DATE-TIME:20201002T163000Z
DTSTAMP;VALUE=DATE-TIME:20230925T233001Z
UID:WSIPM/12
DESCRIPTION:Title: P
ushouts of groupoid extensions by abelian group bundles\nby Alex Kumji
an as part of Western Sydney\, IPM joint workshop on Operator Algebras\n\n
\nAbstract\nGiven a groupoid extension of a locally compact Hausdorff grou
poid by a bundle of abelian groups on which it acts\, we construct a pusho
ut twist over the groupoid semidirect product of the groupoid acting on th
e dual of the bundle regarded as a topological space. We then show that
the C*-algebra of the original extension groupoid is isomorphic to the twi
sted groupoid associated to the pushout. We will also discuss examples.
This talk is based on current joint work with Marius Ionescu\, Jean Renaul
t\, Aidan Sims and Dana Williams.\n
LOCATION:https://researchseminars.org/talk/WSIPM/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Aidan Sims
DTSTART;VALUE=DATE-TIME:20200930T103000Z
DTEND;VALUE=DATE-TIME:20200930T120000Z
DTSTAMP;VALUE=DATE-TIME:20230925T233001Z
UID:WSIPM/24
DESCRIPTION:Title: R
econstruction of groupoids\, and classification of Fell algebras\nby A
idan Sims as part of Western Sydney\, IPM joint workshop on Operator Algeb
ras\n\n\nAbstract\nI will the history of reconstruction of groupoids from
pairs of operator algebras\, from Feldman and Moore’s results on von Neu
mann algebras through Kumjian’s and then Renault’s results about C*-al
gebras of twists\, and including some recent results about groupoids that
are not topologically principal. I will finish by outlining how Kumjian’
s theory leads to a Dixmier-Douady classification theorem for Fell algebra
s.\n
LOCATION:https://researchseminars.org/talk/WSIPM/24/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dana Williams
DTSTART;VALUE=DATE-TIME:20200930T133000Z
DTEND;VALUE=DATE-TIME:20200930T150000Z
DTSTAMP;VALUE=DATE-TIME:20230925T233001Z
UID:WSIPM/26
DESCRIPTION:Title: M
orita equivalence\, the equivariant Brauer group\, and beyond\nby Dana
Williams as part of Western Sydney\, IPM joint workshop on Operator Algeb
ras\n\n\nAbstract\nI will give a brief survey of work on the equivariant B
rauer group together with the necessary preliminaries as well as generaliz
ations involving groupoid C*-algebras.\n
LOCATION:https://researchseminars.org/talk/WSIPM/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jean Renault
DTSTART;VALUE=DATE-TIME:20200930T150000Z
DTEND;VALUE=DATE-TIME:20200930T163000Z
DTSTAMP;VALUE=DATE-TIME:20230925T233001Z
UID:WSIPM/27
DESCRIPTION:Title: K
MS states and groupoid C*-algebras\nby Jean Renault as part of Western
Sydney\, IPM joint workshop on Operator Algebras\n\n\nAbstract\nI will il
lustrate the use of groupoids in the study of KMS states and weights on C*
-algebras. The KMS condition\, which was introduced in quantum statistical
mechanics to characterize equilibrium states\, plays a crucial role in th
e theory of von Neumann algebras. The study of KMS states and their phase
transitions on specific C*-algebras\, in particular graph algebras\, is an
active field of research where the groupoid techniques are well suited.\n
LOCATION:https://researchseminars.org/talk/WSIPM/27/
END:VEVENT
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